draft-ietf-core-resource-directory-11.txt   draft-ietf-core-resource-directory-12.txt 
CoRE Z. Shelby CoRE Z. Shelby
Internet-Draft ARM Internet-Draft ARM
Intended status: Standards Track M. Koster Intended status: Standards Track M. Koster
Expires: January 4, 2018 SmartThings Expires: May 3, 2018 SmartThings
C. Bormann C. Bormann
Universitaet Bremen TZI Universitaet Bremen TZI
P. van der Stok P. van der Stok
consultant consultant
C. Amsuess, Ed. C. Amsuess, Ed.
Energy Harvesting Solutions Energy Harvesting Solutions
July 03, 2017 October 30, 2017
CoRE Resource Directory CoRE Resource Directory
draft-ietf-core-resource-directory-11 draft-ietf-core-resource-directory-12
Abstract Abstract
In many M2M applications, direct discovery of resources is not In many M2M applications, direct discovery of resources is not
practical due to sleeping nodes, disperse networks, or networks where practical due to sleeping nodes, disperse networks, or networks where
multicast traffic is inefficient. These problems can be solved by multicast traffic is inefficient. These problems can be solved by
employing an entity called a Resource Directory (RD), which hosts employing an entity called a Resource Directory (RD), which hosts
descriptions of resources held on other servers, allowing lookups to descriptions of resources held on other servers, allowing lookups to
be performed for those resources. This document specifies the web be performed for those resources. This document specifies the web
interfaces that a Resource Directory supports in order for web interfaces that a Resource Directory supports in order for web
skipping to change at page 1, line 46 skipping to change at page 1, line 46
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 4, 2018. This Internet-Draft will expire on May 3, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 26 skipping to change at page 2, line 26
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Architecture and Use Cases . . . . . . . . . . . . . . . . . 5 3. Architecture and Use Cases . . . . . . . . . . . . . . . . . 5
3.1. Principles . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Principles . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Architecture . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Architecture . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Use Case: Cellular M2M . . . . . . . . . . . . . . . . . 7 3.3. Content model . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Use Case: Home and Building Automation . . . . . . . . . 8 3.4. Use Case: Cellular M2M . . . . . . . . . . . . . . . . . 11
3.5. Use Case: Link Catalogues . . . . . . . . . . . . . . . . 8 3.5. Use Case: Home and Building Automation . . . . . . . . . 12
4. Finding a Resource Directory . . . . . . . . . . . . . . . . 9 3.6. Use Case: Link Catalogues . . . . . . . . . . . . . . . . 12
4.1. Resource Directory Address Option (RDAO) . . . . . . . . 10 4. Finding a Resource Directory . . . . . . . . . . . . . . . . 13
5. Resource Directory . . . . . . . . . . . . . . . . . . . . . 11 4.1. Resource Directory Address Option (RDAO) . . . . . . . . 14
5.1. Content Formats . . . . . . . . . . . . . . . . . . . . . 12 5. Resource Directory . . . . . . . . . . . . . . . . . . . . . 15
5.2. URI Discovery . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Content Formats . . . . . . . . . . . . . . . . . . . . . 16
5.3. Registration . . . . . . . . . . . . . . . . . . . . . . 14 5.2. URI Discovery . . . . . . . . . . . . . . . . . . . . . . 16
5.3.1. Simple Registration . . . . . . . . . . . . . . . . . 17 5.3. Registration . . . . . . . . . . . . . . . . . . . . . . 18
5.3.2. Simple publishing to Resource Directory Server . . . 18 5.3.1. Simple Registration . . . . . . . . . . . . . . . . . 22
5.3.3. Third-party registration . . . . . . . . . . . . . . 18 5.3.2. Third-party registration . . . . . . . . . . . . . . 23
5.3.4. Plurality of link references in a Registration . . . 19 5.4. Operations on the Registration Resource . . . . . . . . . 23
5.4. Operations on the Registration Resource . . . . . . . . . 19 5.4.1. Registration Update . . . . . . . . . . . . . . . . . 24
5.4.1. Registration Update . . . . . . . . . . . . . . . . . 20 5.4.2. Registration Removal . . . . . . . . . . . . . . . . 26
5.4.2. Registration Removal . . . . . . . . . . . . . . . . 22 5.4.3. Read Endpoint Links . . . . . . . . . . . . . . . . . 27
5.4.3. Read Endpoint Links . . . . . . . . . . . . . . . . . 23 5.4.4. Update Endpoint Links . . . . . . . . . . . . . . . . 28
5.4.4. Update Endpoint Links . . . . . . . . . . . . . . . . 24 6. RD Groups . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6. RD Groups . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6.1. Register a Group . . . . . . . . . . . . . . . . . . . . 29
6.1. Register a Group . . . . . . . . . . . . . . . . . . . . 28 6.2. Group Removal . . . . . . . . . . . . . . . . . . . . . . 31
6.2. Group Removal . . . . . . . . . . . . . . . . . . . . . . 30
7. RD Lookup . . . . . . . . . . . . . . . . . . . . . . . . . . 31 7. RD Lookup . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8. Security Considerations . . . . . . . . . . . . . . . . . . . 36 7.1. Resource lookup . . . . . . . . . . . . . . . . . . . . . 32
8.1. Endpoint Identification and Authentication . . . . . . . 36 7.2. Endpoint and group lookup . . . . . . . . . . . . . . . . 33
8.2. Access Control . . . . . . . . . . . . . . . . . . . . . 36 7.3. Lookup filtering . . . . . . . . . . . . . . . . . . . . 33
8.3. Denial of Service Attacks . . . . . . . . . . . . . . . . 37 7.4. Lookup examples . . . . . . . . . . . . . . . . . . . . . 35
8. Security Considerations . . . . . . . . . . . . . . . . . . . 38
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 8.1. Endpoint Identification and Authentication . . . . . . . 38
9.1. Resource Types . . . . . . . . . . . . . . . . . . . . . 37 8.2. Access Control . . . . . . . . . . . . . . . . . . . . . 39
9.2. IPv6 ND Resource Directory Address Option . . . . . . . . 37 8.3. Denial of Service Attacks . . . . . . . . . . . . . . . . 39
9.3. RD Parameter Registry . . . . . . . . . . . . . . . . . . 37 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 38 9.1. Resource Types . . . . . . . . . . . . . . . . . . . . . 40
10.1. Lighting Installation . . . . . . . . . . . . . . . . . 38 9.2. IPv6 ND Resource Directory Address Option . . . . . . . . 40
10.1.1. Installation Characteristics . . . . . . . . . . . . 39 9.3. RD Parameter Registry . . . . . . . . . . . . . . . . . . 40
10.1.2. RD entries . . . . . . . . . . . . . . . . . . . . . 40 9.3.1. Full description of the "Endpoint Type" Registration
10.2. OMA Lightweight M2M (LWM2M) Example . . . . . . . . . . 43 Parameter . . . . . . . . . . . . . . . . . . . . . . 42
10.2.1. The LWM2M Object Model . . . . . . . . . . . . . . . 43 9.4. "Endpoint Type" (et=) RD Parameter values . . . . . . . . 42
10.2.2. LWM2M Register Endpoint . . . . . . . . . . . . . . 45 10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.2.3. LWM2M Update Endpoint Registration . . . . . . . . . 46 10.1. Lighting Installation . . . . . . . . . . . . . . . . . 43
10.2.4. LWM2M De-Register Endpoint . . . . . . . . . . . . . 47 10.1.1. Installation Characteristics . . . . . . . . . . . . 43
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47 10.1.2. RD entries . . . . . . . . . . . . . . . . . . . . . 44
12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 47 10.2. OMA Lightweight M2M (LWM2M) Example . . . . . . . . . . 47
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 10.2.1. The LWM2M Object Model . . . . . . . . . . . . . . . 47
13.1. Normative References . . . . . . . . . . . . . . . . . . 51 10.2.2. LWM2M Register Endpoint . . . . . . . . . . . . . . 49
13.2. Informative References . . . . . . . . . . . . . . . . . 52 10.2.3. LWM2M Update Endpoint Registration . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 10.2.4. LWM2M De-Register Endpoint . . . . . . . . . . . . . 51
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 51
12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 51
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 56
13.1. Normative References . . . . . . . . . . . . . . . . . . 56
13.2. Informative References . . . . . . . . . . . . . . . . . 57
Appendix A. Web links and the Resource Directory . . . . . . . . 58
A.1. A simple example . . . . . . . . . . . . . . . . . . . . 58
A.1.1. Resolving the URIs . . . . . . . . . . . . . . . . . 59
A.1.2. Interpreting attributes and relations . . . . . . . . 59
A.2. A slightly more complex example . . . . . . . . . . . . . 59
A.3. Enter the Resource Directory . . . . . . . . . . . . . . 60
A.4. A note on differences between link-format and Link
headers . . . . . . . . . . . . . . . . . . . . . . . . . 62
Appendix B. Syntax examples for Protocol Negotiation . . . . . . 62
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 63
1. Introduction 1. Introduction
The work on Constrained RESTful Environments (CoRE) aims at realizing The work on Constrained RESTful Environments (CoRE) aims at realizing
the REST architecture in a suitable form for the most constrained the REST architecture in a suitable form for the most constrained
nodes (e.g., 8-bit microcontrollers with limited RAM and ROM) and nodes (e.g., 8-bit microcontrollers with limited RAM and ROM) and
networks (e.g. 6LoWPAN). CoRE is aimed at machine-to-machine (M2M) networks (e.g. 6LoWPAN). CoRE is aimed at machine-to-machine (M2M)
applications such as smart energy and building automation. applications such as smart energy and building automation.
The discovery of resources offered by a constrained server is very The discovery of resources offered by a constrained server is very
important in machine-to-machine applications where there are no important in machine-to-machine applications where there are no
humans in the loop and static interfaces result in fragility. The humans in the loop and static interfaces result in fragility. The
discovery of resources provided by an HTTP Web Server is typically discovery of resources provided by an HTTP Web Server is typically
called Web Linking [RFC5988]. The use of Web Linking for the called Web Linking [RFC5988]. The use of Web Linking for the
description and discovery of resources hosted by constrained web description and discovery of resources hosted by constrained web
servers is specified by the CoRE Link Format [RFC6690]. However, servers is specified by the CoRE Link Format [RFC6690]. However,
[RFC6690] only describes how to discover resources from the web [RFC6690] only describes how to discover resources from the web
server that hosts them by requesting "/.well-known/core". In many server that hosts them by querying "/.well-known/core". In many M2M
M2M scenarios, direct discovery of resources is not practical due to scenarios, direct discovery of resources is not practical due to
sleeping nodes, disperse networks, or networks where multicast sleeping nodes, disperse networks, or networks where multicast
traffic is inefficient. These problems can be solved by employing an traffic is inefficient. These problems can be solved by employing an
entity called a Resource Directory (RD), which hosts descriptions of entity called a Resource Directory (RD), which hosts descriptions of
resources held on other servers, allowing lookups to be performed for resources held on other servers, allowing lookups to be performed for
those resources. those resources.
This document specifies the web interfaces that a Resource Directory This document specifies the web interfaces that a Resource Directory
supports in order for web servers to discover the RD and to register, supports in order for web servers to discover the RD and to register,
maintain, lookup and remove resource descriptions. Furthermore, new maintain, lookup and remove resource descriptions. Furthermore, new
link attributes useful in conjunction with a Resource Directory are link attributes useful in conjunction with a Resource Directory are
skipping to change at page 4, line 31 skipping to change at page 4, line 46
This specification makes use of the following additional terminology: This specification makes use of the following additional terminology:
Resource Directory Resource Directory
A web entity that stores information about web resources and A web entity that stores information about web resources and
implements the REST interfaces defined in this specification for implements the REST interfaces defined in this specification for
registration and lookup of those resources. registration and lookup of those resources.
Domain Domain
In the context of a Resource Directory, a domain is a logical In the context of a Resource Directory, a domain is a logical
grouping of endpoints. This specification assumes that the list grouping of endpoints.
of Domains supported by an RD is pre-configured by that RD. When
a domain is exported to DNS, the domain value equates to the DNS
domain name.
Group Group
In the context of a Resource Directory, a group is a logical In the context of a Resource Directory, a group is a logical
grouping of endpoints for the purpose of group communications. grouping of endpoints for the purpose of group communications.
All groups within a domain are unique. All groups within a domain have unique names.
Endpoint Endpoint
Endpoint (EP) is a term used to describe a web server or client in Endpoint (EP) is a term used to describe a web server or client in
[RFC7252]. In the context of this specification an endpoint is [RFC7252]. In the context of this specification an endpoint is
used to describe a web server that registers resources to the used to describe a web server that registers resources to the
Resource Directory. An endpoint is identified by its endpoint Resource Directory. An endpoint is identified by its endpoint
name, which is included during registration, and is unique within name, which is included during registration, and has a unique name
the associated domain of the registration. within the associated domain of the registration.
Context Context
When registering links to a Resource Directory, the Context refers A Context is a base URL that gives scheme and (typically)
to the scheme, address, port, and base path for all the links authority information about an Endpoint. The Context of an
registered on behalf of an endpoint, of the general form Endpoint is provided at registration time, and is used by the
scheme://host:port/path/ where the client may explicitly set the Resource Directory to resolve relative references inside the
scheme and host, and may supply the port and path as optional registration into absolute URIs.
parameters. When the context of a registration is explicitly set,
the URI resolution rules in [RFC3986] MUST be applied. Directory Resource
A resource in the Resource Directory (RD) containing registration
resources.
Group Resource
A resource in the RD containing registration resources of the
Endpoints that form a group.
Registration Resource
A resource in the RD that contains information about an Endpoint
and its links.
Commissioning Tool Commissioning Tool
Commissioning Tool (CT) is a device that assists during the Commissioning Tool (CT) is a device that assists during the
installation of the network by assigning values to parameters, installation of the network by assigning values to parameters,
naming endpoints and groups, or adapting the installation to the naming endpoints and groups, or adapting the installation to the
needs of the applications. needs of the applications.
RDAO RDAO
Resource Directory Address Option. Resource Directory Address Option.
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information themselves. No other client can modify data in the information themselves. No other client can modify data in the
resource directory or even expect those changes to propagate back to resource directory or even expect those changes to propagate back to
its source. its source.
3.2. Architecture 3.2. Architecture
The resource directory architecture is illustrated in Figure 1. A The resource directory architecture is illustrated in Figure 1. A
Resource Directory (RD) is used as a repository for Web Links Resource Directory (RD) is used as a repository for Web Links
[RFC5988] about resources hosted on other web servers, which are [RFC5988] about resources hosted on other web servers, which are
called endpoints (EP). An endpoint is a web server associated with a called endpoints (EP). An endpoint is a web server associated with a
scheme, IP address and port (called Context), thus a physical node scheme, IP address and port, thus a physical node may host one or
may host one or more endpoints. The RD implements a set of REST more endpoints. The RD implements a set of REST interfaces for
interfaces for endpoints to register and maintain sets of Web Links endpoints to register and maintain sets of Web Links (called resource
(called resource directory registration entries), and for clients to directory registration entries), and for clients to lookup resources
lookup resources from the RD or maintain groups. Endpoints from the RD or maintain groups. Endpoints themselves can also act as
themselves can also act as clients. An RD can be logically segmented clients. An RD can be logically segmented by the use of Domains.
by the use of Domains. The domain an endpoint is associated with can The domain an endpoint is associated with can be defined by the RD or
be defined by the RD or configured by an outside entity. This configured by an outside entity. This information hierarchy is shown
information hierarchy is shown in Figure 2. in Figure 2.
A mechanism to discover an RD using CoRE Link Format [RFC6690] is A mechanism to discover an RD using CoRE Link Format [RFC6690] is
defined. defined.
Endpoints proactively register and maintain resource directory Endpoints proactively register and maintain resource directory
registration entries on the RD, which are soft state and need to be registration entries on the RD, which are soft state and need to be
periodically refreshed. periodically refreshed.
An endpoint is provided with interfaces to register, update and An endpoint is provided with interfaces to register, update and
remove a resource directory registration entry. It is also possible remove a resource directory registration entry. It is also possible
for an RD to fetch Web Links from endpoints and add them as resource for an RD to fetch Web Links from endpoints and add them as resource
directory entries. directory registration entries.
At the first registration of a set of entries, a "registration At the first registration of a set of entries, a "registration
resource" is created, the location of which is returned to the resource" is created, the location of which is returned to the
registering endpoint. The registering endpoint uses this registering endpoint. The registering endpoint uses this
registration resource to manage the contents of the registration registration resource to manage the contents of the registration
entry. entry.
A lookup interface for discovering any of the Web Links held in the A lookup interface for discovering any of the Web Links held in the
RD is provided using the CoRE Link Format. RD is provided using the CoRE Link Format.
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| Endpoint | <-- Name, Scheme, IP, Port | Endpoint | <-- Name, Scheme, IP, Port
+------------+ +------------+
| |
| |
+------------+ +------------+
| Resource | <-- Target, Parameters | Resource | <-- Target, Parameters
+------------+ +------------+
Figure 2: The resource directory information hierarchy. Figure 2: The resource directory information hierarchy.
3.3. Use Case: Cellular M2M 3.3. Content model
The Entity-Relationship (ER) models shown in Figure 3 and Figure 4
model the contents of /.well-known/core and the resource directory
respectively, with entity-relationship diagrams [ER]. Entities
(rectangles) are used for concepts that exist independently.
Attributes (ovals) are used for concepts that exist only in
connection with a related entity. Relations (diamonds) give a
semantic meaning to the relation between entities. Numbers specify
the cardinality of the relations.
Some of the attribute values are URIs. Those values are always full
URIs and never relative references in the information model. They
can, however, be expressed as relative references in serializations,
and often are.
These models provide an abstract view of the information expressed in
link-format documents and a Resource Directory. They cover the
concepts, but not necessarily all details of an RD's operation; they
are meant to give an overview, and not be a template for
implementations.
+----------------------+
| /.well-known/core |
+----------------------+
|
| 1
////////\\\\\\\
< contains >
\\\\\\\\///////
|
| 0+
+--------------------+
| link |
+--------------------+
|
| 1 oooooooo
+-----o target o
0+ | oooooooo
oooooooooooo |
o target o--------+
o attribute o | 0+ oooooo
oooooooooooo +-----o rel o
| oooooo
|
| 1 ooooooooo
+-----o context o
ooooooooo
Figure 3: E-R Model of the content of /.well-known/core
The model shown in Figure 3 models the contents of /.well-known/core
which contains:
o a set of links belonging to the host
The host is free to choose links it deems appropriate to be exposed
in its ".well-known/core". Typically, the links describe resources
that are served by the host, but the set can also contain links to
resources on other servers (see examples in [RFC6690] page 14). The
set does not necessarily contain links to all resources served by the
host.
A link has the following attributes:
o Zero or more link relations: They describe a relations between the
link context and the link target.
In link-format serialization, they are expressed as space-
separated values in the "rel" attribute, and default to "hosts".
o A link context URI: It defines the source of the relation, eg.
_who_ "hosts" something.
In link-format serialization, it is expressed in the "anchor"
attribute. There, it can be a relative reference, in which case
it gets resolved against the URI of the ".well-known/core"
document it was obtained from . It defaults to that document's
URI.
In the serialization, the context also serves as the Base URI for
resolving the target reference.
o A link target URI: It defines the destination of the relation (eg.
_what_ is hosted), and is the topic of all target attributes.
In link-format serialization, it is expressed between angular
brackets, and sometimes called the "href". If it is a relative URI,
it gets resolved against the link context URI.
o Other target attributes (eg. resource type (rt), interface (if),
cor content-type (ct)). These provide additional information
about the target URI.
+----------------------+
| resource-directory |
+----------------------+
|
| oooooooooooo 0-1
| o MC address o---+
| oooooooooooo |
| |
//////\\\\ 0+ +--------+
< contains >----------------| group |
\\\\\///// +--------+
| |
0-n | | 1+
ooooooo 1 +---------------+ ///////\\\\\\
o con o-------| registration |---------< composed of >
ooooooo +---------------+ \\\\\\\//////
| |
| +--------------+
oooooooo 1 | |
o loc o----+ /////\\\\
oooooooo | < contains >
| \\\\\/////
oooooooo 1 | |
o ep o----+ | 0+
oooooooo | +------------------+
| | link |
oooooooo 0-1 | +------------------+
o d o----+ |
oooooooo | | 1 oooooooo
| +-----o target o
oooooooo 0-1 | | oooooooo
o lt o----+ ooooooooooo 0+ |
oooooooo | o target o-----+
| o attribute o | 0+ oooooo
ooooooooooo 0+ | ooooooooooo +-----o rel o
o endpoint o----+ | oooooo
o attribute o |
ooooooooooo | 1 ooooooooo
+----o context o
ooooooooo
Figure 4: E-R Model of the content of the Resource Directory
The model shown in Figure 4 models the contents of the resource
directory which contains in addition to /.well-known/core:
o 0 to n Registration (entries),
o 0 or more Groups
A Group has no or one Multicast address attribute and is composed of
0 or more endpoints. A registration is associated with one endpoint
(ep). An endpoint can be part of 0 or more Groups . A registration
defines a set of links as defined for /.well-known/core. A
Registration has six attributes:
o one ep (endpoint with a unique name)
o one con (a string describing the scheme://authority part)
o one lt (lifetime),
o one loc (location in the RD)
o optional one d (domain for query filtering),
o optional additional endpoint attributes (from Section 9.3)
The cardinality of con is currently 1. Its value is used as a Base
URI when resolving URIs in the links contained in the endpoint.
Links are modelled as they are in Figure 3.
3.4. Use Case: Cellular M2M
Over the last few years, mobile operators around the world have Over the last few years, mobile operators around the world have
focused on development of M2M solutions in order to expand the focused on development of M2M solutions in order to expand the
business to the new type of users: machines. The machines are business to the new type of users: machines. The machines are
connected directly to a mobile network using an appropriate embedded connected directly to a mobile network using an appropriate embedded
air interface (GSM/GPRS, WCDMA, LTE) or via a gateway providing short wireless interface (GSM/GPRS, WCDMA, LTE) or via a gateway providing
and wide range wireless interfaces. From the system design point of short and wide range wireless interfaces. From the system design
view, the ambition is to design horizontal solutions that can enable point of view, the ambition is to design horizontal solutions that
utilization of machines in different applications depending on their can enable utilization of machines in different applications
current availability and capabilities as well as application depending on their current availability and capabilities as well as
requirements, thus avoiding silo like solutions. One of the crucial application requirements, thus avoiding silo like solutions. One of
enablers of such design is the ability to discover resources the crucial enablers of such design is the ability to discover
(machines -- endpoints) capable of providing required information at resources (machines -- endpoints) capable of providing required
a given time or acting on instructions from the end users. information at a given time or acting on instructions from the end
users.
In a typical scenario, during a boot-up procedure (and periodically Imagine a scenario where endpoints installed on vehicles enable
afterwards), the machines (endpoints) register with a Resource tracking of the position of these vehicles for fleet management
Directory (for example EPs installed on vehicles enabling tracking of purposes and allow monitoring of environment parameters. During the
their position for fleet management purposes and monitoring boot-up process endpoints register with a Resource Directory, which
environment parameters) hosted by the mobile operator or somewhere is hosted by the mobile operator or somewhere in the cloud.
else in the network, periodically a description of its own
capabilities. Due to the usual network configuration of mobile Periodically, these endpoints update their registration and may
networks, the EPs attached to the mobile network may not always be modify resources they offer.
efficiently reachable. Therefore, a remote server is usually used to
provide proxy access to the EPs. The address of each (proxy) When endpoints are not always connected, for example because they
endpoint on this server is included in the resource description enter a sleep mode, a remote server is usually used to provide proxy
stored in the RD. The users, for example mobile applications for access to the endpoints. Mobile apps or web applications for
environment monitoring, contact the RD, look up the endpoints capable environment monitoring contact the RD, look up the endpoints capable
of providing information about the environment using appropriate set of providing information about the environment using appropriate set
of link parameters, obtain information on how to contact them (URLs of link parameters, obtain information on how to contact them (URLs
of the proxy server) and then initiate interaction to obtain of the proxy server) and then initiate interaction to obtain
information that is finally processed, displayed on the screen and information that is finally processed, displayed on the screen and
usually stored in a database. Similarly, fleet management systems usually stored in a database. Similarly, fleet management systems
provide the appropriate link parameters to the RD to look up for EPs provide the appropriate link parameters to the RD to look up for EPs
deployed on the vehicles the application is responsible for. deployed on the vehicles the application is responsible for.
3.4. Use Case: Home and Building Automation 3.5. Use Case: Home and Building Automation
Home and commercial building automation systems can benefit from the Home and commercial building automation systems can benefit from the
use of M2M web services. The discovery requirements of these use of M2M web services. The discovery requirements of these
applications are demanding. Home automation usually relies on run- applications are demanding. Home automation usually relies on run-
time discovery to commission the system, whereas in building time discovery to commission the system, whereas in building
automation a combination of professional commissioning and run-time automation a combination of professional commissioning and run-time
discovery is used. Both home and building automation involve peer- discovery is used. Both home and building automation involve peer-
to-peer interactions between endpoints, and involve battery-powered to-peer interactions between endpoints, and involve battery-powered
sleeping devices. sleeping devices.
3.5. Use Case: Link Catalogues 3.6. Use Case: Link Catalogues
Resources may be shared through data brokers that have no knowledge Resources may be shared through data brokers that have no knowledge
beforehand of who is going to consume the data. Resource Directory beforehand of who is going to consume the data. Resource Directory
can be used to hold links about resources and services hosted can be used to hold links about resources and services hosted
anywhere to make them discoverable by a general class of anywhere to make them discoverable by a general class of
applications. applications.
For example, environmental and weather sensors that generate data for For example, environmental and weather sensors that generate data for
public consumption may provide the data to an intermediary server, or public consumption may provide the data to an intermediary server, or
broker. Sensor data are published to the intermediary upon changes broker. Sensor data are published to the intermediary upon changes
skipping to change at page 9, line 13 skipping to change at page 13, line 18
be sufficient to store external metadata in Resource Directories. be sufficient to store external metadata in Resource Directories.
The additional features of Resource Directory allow domains to be The additional features of Resource Directory allow domains to be
defined to enable access to a particular set of resources from defined to enable access to a particular set of resources from
particular applications. This provides isolation and protection of particular applications. This provides isolation and protection of
sensitive data when needed. Resource groups may defined to allow sensitive data when needed. Resource groups may defined to allow
batched reads from multiple resources. batched reads from multiple resources.
4. Finding a Resource Directory 4. Finding a Resource Directory
Several mechanisms can be employed for discovering the RD, including A device coming up may want to find one or more resource directories
assuming a default location (e.g. on an Edge Router in a LoWPAN), to make itself known with.
assigning an anycast address to the RD, using DHCP, or discovering
the RD using .well-known/core and hyperlinks as specified in CoRE
Link Format [RFC6690]. Endpoints that want to contact a Resource
Directory can obtain candidate IP addresses for such servers in a
number of ways.
In a 6LoWPAN, good candidates can be taken from: The device may be pre-configured to exercise specific mechanisms for
finding the resource directory:
o specific static configuration (e.g., anycast addresses), if any, o It may be configured with a specific IP address for the RD. That
IP address may also be an anycast address, allowing the network to
forward RD requests to an RD that is topologically close; each
target network environment in which some of these preconfigured
nodes are to be brought up is then configured with a route for
this anycast address that leads to an appropriate RD. (Instead of
using an anycast address, a multicast address can also be
preconfigured. The RD directory servers then need to configure
one of their interfaces with this multicast address.)
o the ABRO option of 6LoWPAN-ND [RFC6775], o It may be configured with a DNS name for the RD and a resource-
record type to look up under this name; it can find a DNS server
to perform the lookup using the usual mechanisms for finding DNS
servers.
o other ND options that happen to point to servers (such as RDNSS), o It may be configured to use a service discovery mechanism such as
DNS-SD [RFC6763]. The present specification suggests configuring
the service with name rd._sub._coap._udp, preferably within the
domain of the querying nodes.
o DHCPv6 options that might be defined later. For cases where the device is not specifically configured with a way
to find a resource directory, the network may want to provide a
suitable default.
o The IPv6 Neighbor Discovery Resource Directory Address Option o If the address configuration of the network is performed via
described in Section 4.1 SLAAC, this is provided by the RDAO option Section 4.1.
In networks with more inexpensive use of multicast, the candidate IP o If the address configuration of the network is performed via DHCP,
address may be a well-known multicast address, i.e. directory servers this could be provided via a DHCP option (no such option is
are found by simply sending GET requests to that well-known multicast defined at the time of writing).
address (see Section 5.2).
Constrained nodes configured in large batches may be configured for Finally, if neither the device nor the network offer any specific
an anycast address for the RD. Each target network environment in configuration, the device may want to employ heuristics to find a
which some of these preconfigured nodes are to be brought up is then suitable resource directory.
configured with a route for this anycast address that leads to an RD
that is appropriate for the environment.
As some of these sources are just (more or less educated) guesses, The present specification does not fully define these heuristics, but
endpoints MUST make use of any error messages to very strictly rate- suggests a number of candidates:
limit requests to candidate IP addresses that don't work out. For
example, an ICMP Destination Unreachable message (and, in particular, o In a 6LoWPAN, just assume the Edge Router (6LBR) can act as a
the port unreachable code for this message) may indicate the lack of resource directory (using the ABRO option to find that [RFC6775]).
a CoAP server on the candidate host, or a CoAP error response code Confirmation can be obtained by sending a Unicast to
such as 4.05 "Method Not Allowed" may indicate unwillingness of a "coap://[6LBR]/.well-known/core?rt=core.rd*".
CoAP server to act as a directory server.
o In a network that supports multicast well, discovering the RD
using a multicast query for /.well-known/core as specified in CoRE
Link Format [RFC6690]: Sending a Multicast GET to
"coap://[ff02::1]/.well-known/core?rt=core.rd*". RDs within the
multicast scope will answer the query.
As some of the RD addresses obtained by the methods listed here are
just (more or less educated) guesses, endpoints MUST make use of any
error messages to very strictly rate-limit requests to candidate IP
addresses that don't work out. For example, an ICMP Destination
Unreachable message (and, in particular, the port unreachable code
for this message) may indicate the lack of a CoAP server on the
candidate host, or a CoAP error response code such as 4.05 "Method
Not Allowed" may indicate unwillingness of a CoAP server to act as a
directory server.
4.1. Resource Directory Address Option (RDAO) 4.1. Resource Directory Address Option (RDAO)
The Resource Directory Option (RDAO) using IPv6 neighbor Discovery The Resource Directory Option (RDAO) using IPv6 neighbor Discovery
(ND) carries information about the address of the Resource Directory (ND) carries information about the address of the Resource Directory
(RD). This information is needed when endpoints cannot discover the (RD). This information is needed when endpoints cannot discover the
Resource Directory with link-local multicast address because the Resource Directory with link-local multicast address because the
endpoint and the RD are separated by a border Router (6LBR). In many endpoint and the RD are separated by a border Router (6LBR). In many
circumstances the availability of DHCP cannot be guaranteed either circumstances the availability of DHCP cannot be guaranteed either
during commissioning of the network. The presence and the use of the during commissioning of the network. The presence and the use of the
skipping to change at page 11, line 43 skipping to change at page 15, line 45
A value of all zero bits (0x0) indicates A value of all zero bits (0x0) indicates
that this Resource Directory address that this Resource Directory address
is not valid anymore. is not valid anymore.
Reserved: This field is unused. It MUST be Reserved: This field is unused. It MUST be
initialized to zero by the sender and initialized to zero by the sender and
MUST be ignored by the receiver. MUST be ignored by the receiver.
RD Address: IPv6 address of the RD. RD Address: IPv6 address of the RD.
Figure 3: Resource Directory Address Option Figure 5: Resource Directory Address Option
5. Resource Directory 5. Resource Directory
This section defines the required set of REST interfaces between a This section defines the required set of REST interfaces between a
Resource Directory (RD) and endpoints. Although the examples Resource Directory (RD) and endpoints. Although the examples
throughout this section assume the use of CoAP [RFC7252], these REST throughout this section assume the use of CoAP [RFC7252], these REST
interfaces can also be realized using HTTP [RFC7230]. In all interfaces can also be realized using HTTP [RFC7230]. In all
definitions in this section, both CoAP response codes (with dot definitions in this section, both CoAP response codes (with dot
notation) and HTTP response codes (without dot notation) are shown. notation) and HTTP response codes (without dot notation) are shown.
An RD implementing this specification MUST support the discovery, An RD implementing this specification MUST support the discovery,
registration, update, lookup, and removal interfaces defined in this registration, update, lookup, and removal interfaces defined in this
section. section.
All operations on the contents of the Resource Directory MUST be
atomic and idempotent.
A resource directory MAY make the information submitted to it
available to further directories, if it can ensure that a loop does
not form. The protocol used between directories to ensure loop-free
operation is outside the scope of this document.
5.1. Content Formats 5.1. Content Formats
Resource Directory implementations using this specification MUST Resource Directory implementations using this specification MUST
support the application/link-format content format (ct=40). support the application/link-format content format (ct=40).
Resource Directories implementing this specification MAY support Resource Directories implementing this specification MAY support
additional content formats. additional content formats.
Any additional content format supported by a Resource Directory Any additional content format supported by a Resource Directory
implementing this specification MUST have an equivalent serialization implementing this specification MUST have an equivalent serialization
in the application/link-format content format. in the application/link-format content format.
5.2. URI Discovery 5.2. URI Discovery
Before an endpoint can make use of an RD, it must first know the RD's Before an endpoint can make use of an RD, it must first know the RD's
address and port, and the URI path information for its REST APIs. address and port, and the URI path information for its REST APIs.
This section defines discovery of the RD and its URIs using the well- This section defines discovery of the RD and its URIs using the well-
known interface of the CoRE Link Format [RFC6690]. It is however known interface of the CoRE Link Format [RFC6690]. A complete set of
expected that RDs will also be discoverable via other methods RD discovery methods is described in Section 4.
depending on the deployment.
Discovery of the RD registration URI path is performed by sending Discovery of the RD registration URI path is performed by sending
either a multicast or unicast GET request to "/.well-known/core" and either a multicast or unicast GET request to "/.well-known/core" and
including a Resource Type (rt) parameter [RFC6690] with the value including a Resource Type (rt) parameter [RFC6690] with the value
"core.rd" in the query string. Likewise, a Resource Type parameter "core.rd" in the query string. Likewise, a Resource Type parameter
value of "core.rd-lookup*" is used to discover the URIs for RD Lookup value of "core.rd-lookup*" is used to discover the URIs for RD Lookup
operations, and "core.gp" is used to discover the URI path for RD operations, and "core.rd-group" is used to discover the URI path for
Group operations. Upon success, the response will contain a payload RD Group operations. Upon success, the response will contain a
with a link format entry for each RD function discovered, indicating payload with a link format entry for each RD function discovered,
the URI path of the RD function returned and the corresponding indicating the URI path of the RD function returned and the
Resource Type. When performing multicast discovery, the multicast IP corresponding Resource Type. When performing multicast discovery,
address used will depend on the scope required and the multicast the multicast IP address used will depend on the scope required and
capabilities of the network. the multicast capabilities of the network.
A Resource Directory MAY provide hints about the content-formats it A Resource Directory MAY provide hints about the content-formats it
supports in the links it exposes or registers, using the "ct" link supports in the links it exposes or registers, using the "ct" link
attribute, as shown in the example below. Clients MAY use these attribute, as shown in the example below. Clients MAY use these
hints to select alternate content-formats for interaction with the hints to select alternate content-formats for interaction with the
Resource Directory. Resource Directory.
HTTP does not support multicast and consequently only unicast HTTP does not support multicast and consequently only unicast
discovery can be supported using HTTP. Links to Resource Directories discovery can be supported using HTTP. Links to Resource Directories
MAY be registered in other Resource Directories, and well-known entry MAY be registered in other Resource Directories, and well-known entry
skipping to change at page 13, line 21 skipping to change at page 17, line 31
Interaction: EP -> RD Interaction: EP -> RD
Method: GET Method: GET
URI Template: /.well-known/core{?rt} URI Template: /.well-known/core{?rt}
URI Template Variables: URI Template Variables:
rt := Resource Type (optional). MAY contain one of the values rt := Resource Type (optional). MAY contain one of the values
"core.rd", "core.rd-lookup*", "core.rd-lookup-d", "core.rd- "core.rd", "core.rd-lookup*", "core.rd-lookup-res", "core.rd-
lookup-res", "core.rd-lookup-ep", "core.rd-lookup-gp", lookup-ep", "core.rd-lookup-gp", "core.rd-group" or "core.rd*"
"core.rd-group" or "core.rd*"
Content-Format: application/link-format (if any) Content-Format: application/link-format (if any)
Content-Format: application/link-format+json (if any) Content-Format: application/link-format+json (if any)
Content-Format: application/link-format+cbor (if any) Content-Format: application/link-format+cbor (if any)
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.05 "Content" or 200 "OK" with an application/link-format, Success: 2.05 "Content" or 200 "OK" with an application/link-format,
application/link-format+json, or application/link-format+cbor application/link-format+json, or application/link-format+cbor
payload containing one or more matching entries for the RD payload containing one or more matching entries for the RD
resource. resource.
Failure: 4.04 "Not Found" or 404 "Not Found" is returned in case no
matching entry is found for a unicast request.
Failure: 4.00 "Bad Request" or 400 "Bad Request" is returned in case Failure: 4.00 "Bad Request" or 400 "Bad Request" is returned in case
of a malformed request for a unicast request. of a malformed request for a unicast request.
Failure: No error response to a multicast request. Failure: No error response to a multicast request.
HTTP support : YES (Unicast only) HTTP support : YES (Unicast only)
The following example shows an endpoint discovering an RD using this The following example shows an endpoint discovering an RD using this
interface, thus learning that the RD registration resource is, in interface, thus learning that the directory resource is, in this
this example, at /rd, and that the content-format delivered by the example, at /rd, and that the content-format delivered by the server
server hosting the resource is application/link-format (ct=40). Note hosting the resource is application/link-format (ct=40). Note that
that it is up to the RD to choose its RD resource paths. it is up to the RD to choose its RD resource paths.
Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd* Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd*
Res: 2.05 Content Res: 2.05 Content
</rd>;rt="core.rd";ct=40, </rd>;rt="core.rd";ct=40,
</rd-lookup/ep>;rt="core.rd-lookup-ep";ct=40, </rd-lookup/ep>;rt="core.rd-lookup-ep";ct=40,
</rd-lookup/res>;rt="core.rd-lookup-res";ct=40, </rd-lookup/res>;rt="core.rd-lookup-res";ct=40,
</rd-lookup/gp>;rt="core.rd-lookup-gp";ct=40, </rd-lookup/gp>;rt="core.rd-lookup-gp";ct=40,
</rd-lookup/d>;rt="core.rd-lookup-d";ct=40,
</rd-group>;rt="core.rd-group";ct=40 </rd-group>;rt="core.rd-group";ct=40
Figure 4: Example discovery exchange Figure 6: Example discovery exchange
The following example shows the way of indicating that a client may The following example shows the way of indicating that a client may
request alternate content-formats. The Content-Format code attribute request alternate content-formats. The Content-Format code attribute
"ct" MAY include a space-separated sequence of Content-Format codes "ct" MAY include a space-separated sequence of Content-Format codes
as specified in Section 7.2.1 of [RFC7252], indicating that multiple as specified in Section 7.2.1 of [RFC7252], indicating that multiple
content-formats are available. The example below shows the required content-formats are available. The example below shows the required
Content-Format 40 (application/link-format) indicated as well as a Content-Format 40 (application/link-format) indicated as well as the
more application-specific content format (picked as 65225 in this the CBOR and JSON representation of link format. The RD resource
example; this is in the experimental space, not an assigned value). paths /rd, /rd-lookup, and /rd-group are example values.
The RD resource paths /rd, /rd-lookup, and /rd-group are example
values. This server only implements some of the interfaces described [ The RFC editor is asked to replace these and later occurrences of
in this document. TBD64 and TBD504 with the numeric ID values assigned by IANA to
application/link-format+cbor and application/link-format+json,
respectively, as they are defined in I-D.ietf-core-links-json. ]
Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd* Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd*
Res: 2.05 Content Res: 2.05 Content
</rd>;rt="core.rd";ct="40 65225", </rd>;rt="core.rd";ct="40 65225",
</rd-lookup/res>;rt="core.rd-lookup-res";ct="40 65225", </rd-lookup/res>;rt="core.rd-lookup-res";ct="40 TBD64 TBD504",
</rd-lookup/ep>;rt="core.rd-lookup-ep";ct="40 65225", </rd-lookup/ep>;rt="core.rd-lookup-ep";ct="40 TBD64 TBD504",
</rd-group>;rt="core.rd-group";ct="40 65225" </rd-lookup/gp>;rt="core.rd-lookup-gp";ct=40 TBD64 TBD504",
</rd-group>;rt="core.rd-group";ct="40 TBD64 TBD504"
5.3. Registration 5.3. Registration
After discovering the location of an RD, an endpoint MAY register its After discovering the location of an RD, an endpoint MAY register its
resources using the registration interface. This interface accepts a resources using the registration interface. This interface accepts a
POST from an endpoint containing the list of resources to be added to POST from an endpoint containing the list of resources to be added to
the directory as the message payload in the CoRE Link Format the directory as the message payload in the CoRE Link Format
[RFC6690], JSON CoRE Link Format (application/link-format+json), or [RFC6690], JSON CoRE Link Format (application/link-format+json), or
CBOR CoRE Link Format (application/link-format+cbor) CBOR CoRE Link Format (application/link-format+cbor)
[I-D.ietf-core-links-json], along with query parameters indicating [I-D.ietf-core-links-json], along with query parameters indicating
the name of the endpoint, and optionally its domain and the lifetime the name of the endpoint, and optionally its domain and the lifetime
of the registration. It is expected that other specifications will of the registration. It is expected that other specifications will
define further parameters (see Section 9.3). The RD then creates a define further parameters (see Section 9.3). The RD then creates a
new registration resource in the RD and returns its location. An new registration resource in the RD and returns its location. An
endpoint MUST use that location when refreshing registrations using endpoint MUST use that location when refreshing registrations using
this interface. Endpoint resources in the RD are kept active for the this interface. Registration resources in the RD are kept active for
period indicated by the lifetime parameter. The endpoint is the period indicated by the lifetime parameter. The endpoint is
responsible for refreshing the entry within this period using either responsible for refreshing the registration resource within this
the registration or update interface. The registration interface period using either the registration or update interface. The
MUST be implemented to be idempotent, so that registering twice with registration interface MUST be implemented to be idempotent, so that
the same endpoint parameters ep and d does not create multiple RD registering twice with the same endpoint parameters ep and d does not
entries. A new registration may be created at any time to supersede create multiple registration resources. A new registration resource
an existing registration, replacing the registration parameters and may be created at any time to supersede an existing registration,
links. replacing the registration parameters and links.
An empty payload is considered a malformed request.
The posted link-format document can (and typically does) contain
relative references both in its link targets and in its anchors, or
contain empty anchors. The RD server needs to resolve these
references in order to faithfully represent them in lookups. The
Base URI against which they are resolved is the context of the
registration, which is provided either explicitly in the "con"
parameter or constructed implicitly from the requester's network
address. When resolving relative target references, the server first
resolves the context of that link, and then interprets the target as
a reference relative to that context (see Appendix A.4).
The registration request interface is specified as follows: The registration request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: POST Method: POST
URI Template: {+rd}{?ep,d,et,lt,con} URI Template: {+rd}{?ep,d,lt,con,extra-attrs*}
URI Template Variables: URI Template Variables:
rd := RD registration URI (mandatory). This is the location of rd := RD registration URI (mandatory). This is the location of
the RD, as obtained from discovery. the RD, as obtained from discovery.
ep := Endpoint name (mandatory). The endpoint name is an ep := Endpoint name (mostly mandatory). The endpoint name is an
identifier that MUST be unique within a domain. The maximum identifier that MUST be unique within a domain. The maximum
length of this parameter is 63 bytes. length of this parameter is 63 bytes. If the RD is configured
to recognize the endpoint (eg. based on its security context),
the endpoint can elide the endpoint name, and assign one based
on the configuration.
d := Domain (optional). The domain to which this endpoint d := Domain (optional). The domain to which this endpoint
belongs. The maximum length of this parameter is 63 bytes. belongs. The maximum length of this parameter is 63 bytes.
When this parameter is elided, the RD MAY associate the When this parameter is elided, the RD MAY associate the
endpoint with a configured default domain. endpoint with a configured default domain.
et := Endpoint Type (optional). The semantic type of the
endpoint. This parameter SHOULD be less than 63 bytes.
lt := Lifetime (optional). Lifetime of the registration in lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included seconds. Range of 60-4294967295. If no lifetime is included
in the initial registration, a default value of 86400 (24 in the initial registration, a default value of 86400 (24
hours) SHOULD be assumed. If the lt parameter is not included hours) SHOULD be assumed.
in a registration refresh or update operation, the most
recently supplied value SHALL be re-used.
con := Context (optional). This parameter sets the scheme, con := Context (optional). This parameter sets the Default Base
address, port and path at which this server is available in the URI under which the request's links are to be interpreted. The
form scheme://host:port/path. In the absence of this parameter URI MUST NOT have a path component of its own, but MUST be
the scheme of the protocol, source address and source port of suitable as a base URI to resolve any relative references given
the register request are assumed. This parameter is mandatory in the registration. The parameter is therefore of the shape
when the directory is filled by a third party such as an "scheme://authority" for HTTP and CoAP URIs. In the absence of
commissioning tool. When con is used, scheme and host are this parameter the scheme of the protocol, source address and
mandatory and port and path parameters are optional. If the source port of the registration request are assumed. This
endpoint uses an ephemeral port to register with, it MUST parameter is mandatory when the directory is filled by a third
include the con: parameter in the registration to provide a party such as an commissioning tool. If the endpoint uses an
valid network path. If the endpoint which is located behind a ephemeral port to register with, it MUST include the con
NAT gateway is registering with a Resource Directory which is parameter in the registration to provide a valid network path.
on the network service side of the NAT gateway, the endpoint If the endpoint which is located behind a NAT gateway is
MUST use a persistent port for the outgoing registration in registering with a Resource Directory which is on the network
order to provide the NAT gateway with a valid network address service side of the NAT gateway, the endpoint MUST use a
for replies and incoming requests. persistent port for the outgoing registration in order to
provide the NAT gateway with a valid network address for
replies and incoming requests.
extra-attrs := Additional registration attributes (optional).
The endpoint can pass any parameter registered at Section 9.3
to the directory. If the RD is aware of the parameter's
specified semantics, it processes it accordingly. Otherwise,
it MUST store the unknown key and its value(s) as an endpoint
attribute for further lookup.
Content-Format: application/link-format Content-Format: application/link-format
Content-Format: application/link-format+json Content-Format: application/link-format+json
Content-Format: application/link-format+cbor Content-Format: application/link-format+cbor
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.01 "Created" or 201 "Created". The Location header Success: 2.01 "Created" or 201 "Created". The Location header
option MUST be included in the response when a new registration option MUST be included in the response when a new registration
resource is created. This Location MUST be a stable identifier resource is created. This Location MUST be a stable identifier
generated by the RD as it is used for all subsequent operations on generated by the RD as it is used for all subsequent operations on
this registration resource. The registration resource location this registration resource. The registration resource location
thus returned is for the purpose of updating the lifetime of the thus returned is for the purpose of updating the lifetime of the
registration and for maintaining the content of the registered registration and for maintaining the content of the registered
links, including updating and deleting links. links, including updating and deleting links. A registration with
an already registered ep and d value pair responds with the same
success code and Location as the original registration; the set of
links registered with the endpoint is replaced with the links from
the payload.
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request. request.
Failure: 4.09 "Conflict" or 409 "Conflict". Attempt to update the
registration content with links resulting in plurality of
references; see Section 5.3.4.
Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable". Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable".
Service could not perform the operation. Service could not perform the operation.
HTTP support: YES HTTP support: YES
The following example shows an endpoint with the name "node1" The following example shows an endpoint with the name "node1"
registering two resources to an RD using this interface. The registering two resources to an RD using this interface. The
location "/rd" is an example RD location discovered in a request location "/rd" is an example RD location discovered in a request
similar to Figure 4. similar to Figure 6.
Req: POST coap://rd.example.com/rd?ep=node1 Req: POST coap://rd.example.com/rd?ep=node1
Content-Format: 40 Content-Format: 40
Payload: Payload:
</sensors/temp>;ct=41;rt="temperature-c";if="sensor", </sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/light>;ct=41;rt="light-lux";if="sensor" </sensors/light>;ct=41;rt="light-lux";if="sensor"
Res: 2.01 Created Res: 2.01 Created
Location: /rd/4521 Location: /rd/4521
A Resource Directory may optionally support HTTP. Here is an example A Resource Directory may optionally support HTTP. Here is an example
of the same registration operation above, when done using HTTP. of almost the same registration operation above, when done using HTTP
and the JSON Link Format.
Req: POST /rd?ep=node1&con=http://[2001:db8::1:1] HTTP/1.1
Host : example.com
Content-Type: application/link-format
Payload:
</sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/light>;ct=41;rt="light-lux";if="sensor"
Res: 201 Created Req: POST /rd?ep=node1&con=http://[2001:db8:1::1] HTTP/1.1
Location: /rd/4521 Host : example.com
Content-Type: application/link-format+json
Payload:
[
{"href": "/sensors/temp", "ct": "41", "rt": "temperature-c", "if": "sensor"},
{"href": "/sensors/light", "ct": "41", "rt": "light-lux", "if": "sensor"}
]
Res: 201 Created
Location: /rd/4521
5.3.1. Simple Registration 5.3.1. Simple Registration
Not all endpoints hosting resources are expected to know how to Not all endpoints hosting resources are expected to know how to
upload links to a RD as described in Section 5.3. Instead, simple upload links to a RD as described in Section 5.3. Instead, simple
endpoints can implement the Simple Registration approach described in endpoints can implement the Simple Registration approach described in
this section. An RD implementing this specification MUST implement this section. An RD implementing this specification MUST implement
Simple Registration. However, there may be security reasons why this Simple Registration. However, there may be security reasons why this
form of directory discovery would be disabled. form of directory discovery would be disabled.
This approach requires that the endpoint makes available the hosted This approach requires that the endpoint makes available the hosted
resources that it wants to be discovered, as links on its "/.well- resources that it wants to be discovered, as links on its "/.well-
known/core" interface as specified in [RFC6690]. known/core" interface as specified in [RFC6690].
The endpoint then finds one or more addresses of the directory server The endpoint then finds one or more addresses of the directory server
as described in Section 4. as described in Section 4.
An endpoint can send (a selection of) hosted resources to a directory An endpoint finally asks the directory server to probe it for
server for publication as described in Section 5.3.2. resources and publish them as follows:
The directory server integrates the information it received this way
into its resource directory. It MAY make the information available
to further directories, if it can ensure that a loop does not form.
The protocol used between directories to ensure loop-free operation
is outside the scope of this document.
5.3.2. Simple publishing to Resource Directory Server It sends (and regularly refreshes with) a POST request to the
"/.well-known/core" URI of the directory server of choice. The body
of the POST request is empty, which triggers the resource directory
server to perform GET requests at the requesting server's default
discovery URI to obtain the link-format payload to register.
An endpoint that wants to make itself discoverable occasionally sends The endpoint includes the same registration parameters in the POST
a POST request to the "/.well-known/core" URI of any candidate request as it would per Section 5.3. The context of the registration
directory server that it finds. The body of the POST request is is taken from the requesting server's URI.
empty, which triggers the resource directory server to perform GET
requests at the requesting server's default discovery URI to obtain
the link-format payload to register.
The endpoint MUST include the endpoint name and MAY include the The endpoints MUST be deleted after the expiration of their lifetime.
registration parameters d, lt, and et, in the POST request as per Additional operations cannot be executed because no registration
Section 5.3. location is returned.
The following example shows an endpoint using simple publishing, by The following example shows an endpoint using Simple Registration, by
simply sending an empty POST to a resource directory. simply sending an empty POST to a resource directory.
Req:(to RD server from [ff02::1]) Req:(to RD server from [2001:db8:2::1])
POST coap://rd.example.com/.well-known/core?lt=6000;ep=node1 POST /.well-known/core?lt=6000&ep=node1
Content-Format: 40 Content-Format: 40
No payload
payload:
(empty payload)
Res: 2.04 Changed Res: 2.04 Changed
(later) (later)
Req: (from RD server to [ff02::1]) Req: (from RD server to [2001:db8:2::1])
GET coap://[ff02::1]/.well-known/core GET /.well-known/core
Accept: 40 Accept: 40
Res: 2.05 Content Res: 2.05 Content
Payload:
payload:
</sen/temp> </sen/temp>
5.3.3. Third-party registration 5.3.2. Third-party registration
For some applications, even Simple Registration may be too taxing for For some applications, even Simple Registration may be too taxing for
certain very constrained devices, in particular if the security certain very constrained devices, in particular if the security
requirements become too onerous. requirements become too onerous.
In a controlled environment (e.g. building control), the Resource In a controlled environment (e.g. building control), the Resource
Directory can be filled by a third device, called a commissioning Directory can be filled by a third device, called a commissioning
tool. The commissioning tool can fill the Resource Directory from a tool. The commissioning tool can fill the Resource Directory from a
database or other means. For that purpose the scheme, IP address and database or other means. For that purpose the scheme, IP address and
port of the registered device is indicated in the Context parameter port of the registered device is indicated in the Context parameter
of the registration described in Section 5.3. of the registration described in Section 5.3.
5.3.4. Plurality of link references in a Registration
Plurality of link references within a Registration (registration
resource) is an indication of some error condition and should not be
allowed.
Plurality of link references exists if, and only if, two or more
links in a Registration contain identical context, target, and
relation values. This condition would be likely to arise if there
were multiple co-ordinators or configuration tools, each with a
different set of configuration values for the same resource.
A Resource Directory SHOULD reject a registration, or an operation on
a registration, which would result in a plurality of link references
within the the context of the registration. There is no requirement
in this document for a resource directory to check for plurality of
reference between different registrations. Resource Directory
operations which are rejected due to reference plurality SHOULD be
returned the "Conflict" code, indicating that there is someting wrong
with the request.
5.4. Operations on the Registration Resource 5.4. Operations on the Registration Resource
After the initial registration, an endpoint should retain the After the initial registration, an endpoint should retain the
returned location of the Registration Resource for further returned location of the Registration Resource for further
operations, including refreshing the registration in order to extend operations, including refreshing the registration in order to extend
the lifetime and "keep-alive" the registration. If the lifetime of the lifetime and "keep-alive" the registration. When the lifetime of
the registration expires, the RD SHOULD NOT respond to discovery the registration has expired, the RD SHOULD NOT respond to discovery
queries with information from the endpoint. The RD SHOULD continue queries concerning this endpoint. The RD SHOULD continue to provide
to provide access to the Registration Resource after a registration access to the Registration Resource after a registration time-out
time-out occurs in order to enable the registering endpoint to occurs in order to enable the registering endpoint to eventually
eventually refresh the registration. The RD MAY eventually remove refresh the registration. The RD MAY eventually remove the
the registration resource for the purpose of resource recovery and registration resource for the purpose of resource recovery and
garbage collection. If the Registration Resource is removed, the garbage collection. If the Registration Resource is removed, the
endpoint will need to re-register. endpoint will need to re-register.
The Registration Resource may also be used to inspect the The Registration Resource may also be used to inspect the
registration resource using GET, update the registration link registration resource using GET, update the registration link
contents using PATCH (as introduced in [RFC8132]), or cancel the contents, or cancel the registration using DELETE.
registration using DELETE.
These operations are described in this section. These operations are described in this section.
In accordance with Section 5.3.4, operations which would result in
plural link references within the context of a registration resource
SHOULD be rejected using the "Conflict" result code.
5.4.1. Registration Update 5.4.1. Registration Update
The update interface is used by an endpoint to refresh or update its The update interface is used by an endpoint to refresh or update its
registration with an RD. To use the interface, the endpoint sends a registration with an RD. To use the interface, the endpoint sends a
POST request to the registration resource returned in the Location POST request to the registration resource returned in the Location
header option in the response returned from the intial registration header option in the response returned from the initial registration
operation. operation.
An update MAY update the lifetime or context registration parameters An update MAY update the lifetime- or the context- registration
"lt", "con" as in Section 5.3 ) if the previous settings are to be parameters "lt", "con" as in Section 5.3. Parameters that are not
retained. Parameters that are not being changed changed SHOULD NOT being changed SHOULD NOT be included in an update. Adding parameters
be included in an update. Adding parameters that have not changed that have not changed increases the size of the message but does not
increases the size of the message but does not have any other have any other implications. Parameters MUST be included as query
implications. Parameters MUST be included as query parameters in an parameters in an update operation as in Section 5.3.
update operation as in Section 5.3.
Upon receiving an update request, an RD MUST reset the timeout for
that endpoint and update the scheme, IP address and port of the
endpoint, using the source address of the update, or the context
("con") parameter if present. If the lifetime parameter "lt" is
included in the received update request, the RD MUST update the
lifetime of the registration and set the timeout equal to the new
lifetime. If the lifetime parameter is not included in the
registration update, the most recent setting is re-used for the next
registration time-out period.
An update MAY optionally add or replace links for the endpoint by A registration update resets the timeout of the registration to the
including those links in the payload of the update as a CoRE Link (possibly updated) lifetime of the registration, independent of
Format document. A link is replaced only if all of the target URI whether a "lt" parameter was given.
and relation type (if present) and anchor value (if present) match.
If the link payload is included, it SHOULD be checked for reference If the context of the registration is changed in an update explicitly
plurality as described in Section 5.3.4 and rejected with a or implicitly, relative references submitted in the original
"Conflict" result if there are plural link references detected. registration or later updates are resolved anew against the new
context (like in the original registration).
In addition to the use of POST, as described in this section, there This operation only describes the use of POST with an empty payload.
is an alternate way to add, replace, and delete links using PATCH as As with modification of individual using iPATCH or PATCH as proposed
described in Section 5.4.4. in Section 5.4.4, future standards might describe the semantics of
using content formats and payloads with the POST method to update the
links of a registration.
The update registration request interface is specified as follows: The update registration request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: POST Method: POST
URI Template: {+location}{?lt,con}
URI Template: {+location}{?lt,con,extra-attrs*}
URI Template Variables: URI Template Variables:
location := This is the Location returned by the RD as a result location := This is the Location returned by the RD as a result
of a successful earlier registration. of a successful earlier registration.
lt := Lifetime (optional). Lifetime of the registration in lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included, seconds. Range of 60-4294967295. If no lifetime is included,
the previous last lifetime set on a previous update or the the previous last lifetime set on a previous update or the
original registration (falling back to 86400) SHOULD be used. original registration (falling back to 86400) SHOULD be used.
con := Context (optional). This parameter sets the scheme, con := Context (optional). This parameter updates the context
address and port at which this server is available in the form established in the original registration to a new value. If
scheme://host:port/path. In the absence of this parameter the the parameter is set in an update, it is stored by the RD as
scheme of the protocol, source address and source port of the the new Base URI under which to interpret the links of the
register request are assumed. This parameter is mandatory when registration, following the same restrictions as in the
the directory is filled by a third party such as an registration. If the parameter is not set and was set
commissioning tool. When con is used, scheme and host are explicitly before, the previous context value is kept
mandatory and port and path parameters are optional. unmodified. If the parameter is not set and was not set
explicitly before either, the source address and source port of
Content-Format: application/link-format (mandatory) the update request are stored as the context.
Content-Format: application/link-format+json (optional) extra-attrs := Additional registration attributes (optional). As
with the registration, the RD processes them if it knows their
semantics. Otherwise, unknown attributes are stored as
endpoint attributes, overriding any previously stored endpoint
attributes of the same key.
Content-Format: application/link-format+cbor (optional) Content-Format: none (no payload)
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.04 "Changed" or 204 "No Content" if the update was Success: 2.04 "Changed" or 204 "No Content" if the update was
successfully processed. successfully processed.
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request. request.
Failure: 4.04 "Not Found" or 404 "Not Found". Registration does not Failure: 4.04 "Not Found" or 404 "Not Found". Registration does not
exist (e.g. may have expired). exist (e.g. may have expired).
Failure: 4.09 "Conflict" or 409 "Conflict". Attempt to update the
registration content with links resulting in plurality of
references; see Section 5.3.4.
Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable". Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable".
Service could not perform the operation. Service could not perform the operation.
HTTP support: YES HTTP support: YES
The following example shows an endpoint updating its registration at
an RD using this interface with the example location value: /rd/4521. The following example shows an endpoint updating its registration
resource at an RD using this interface with the example location
value: /rd/4521.
Req: POST /rd/4521 Req: POST /rd/4521
Res: 2.04 Changed Res: 2.04 Changed
The following example shows an endpoint updating its registration The following example shows an endpoint updating its registration
with a new lifetime and context, changing an existing link, and resource at an RD using this interface with the example location
adding a new link using this interface with the example location value: /rd/4521. The initial registration by the client set the
value /rd/4521. With the initial registration the client set the
following values: following values:
o endpoint name (ep)=endpoint1
o lifetime (lt)=500 o lifetime (lt)=500
o context (con)=coap://local-proxy-old.example.com:5683 o context (con)=coap://local-proxy-old.example.com:5683
o resource= </sensors/temp>;ct=41;rt="foobar";if="sensor" The initial state of the Resource Directory is reflected in the
following request:
Req: POST /rd/4521?lt=600&con="coap://local-proxy.example.com:5683" Req: GET /rd-lookup/res?ep=endpoint1
Content-Format: 40
Payload: Res: 2.01 Content
</sensors/temp>;ct=41;rt="temperature-f";if="sensor", Payload:
</sensors/door>;ct=41;rt="door";if="sensor" </sensors/temp>;ct=41;rt="temperature";anchor="coap://local-proxy-old.example.com:5683",
</sensors/light>;ct=41;rt="light-lux";if="sensor";anchor="coap://local-proxy-old.example.com:5683"
The following example shows an EP changing the context to
"coaps://new.example.com:5684":
Req: POST /rd/4521?con=coaps://new.example.com:5684
Res: 2.04 Changed Res: 2.04 Changed
The consecutive query returns:
Req: GET /rd-lookup/res?ep=endpoint1
Res: 2.01 Content
Payload:
</sensors/temp>;ct=41;rt="temperature";anchor="coaps://new.example.com:5684",
</sensors/light>;ct=41;rt="light-lux";if="sensor";anchor="coaps://new.example.com:5684",
5.4.2. Registration Removal 5.4.2. Registration Removal
Although RD entries have soft state and will eventually timeout after Although RD entries have soft state and will eventually timeout after
their lifetime, an endpoint SHOULD explicitly remove its entry from their lifetime, an endpoint SHOULD explicitly remove its entry from
the RD if it knows it will no longer be available (for example on the RD if it knows it will no longer be available (for example on
shut-down). This is accomplished using a removal interface on the RD shut-down). This is accomplished using a removal interface on the RD
by performing a DELETE on the endpoint resource. by performing a DELETE on the endpoint resource.
Removed endpoints are implicitly removed from the groups to which
they belong.
The removal request interface is specified as follows: The removal request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: DELETE Method: DELETE
URI Template: {+location} URI Template: {+location}
URI Template Variables: URI Template Variables:
skipping to change at page 24, line 39 skipping to change at page 28, line 47
Req: GET /rd/4521 Req: GET /rd/4521
Res: 2.01 Content Res: 2.01 Content
Payload: Payload:
</sensors/temp>;ct=41;rt="temperature-c";if="sensor", </sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/light>;ct=41;rt="light-lux";if="sensor" </sensors/light>;ct=41;rt="light-lux";if="sensor"
5.4.4. Update Endpoint Links 5.4.4. Update Endpoint Links
A PATCH update adds, removes or changes links for the endpoint by An iPATCH (or PATCH) update [RFC8132] adds, removes or changes links
including link update information in the payload of the update as a of a registration by including link update information in the payload
merge-patch+json format [RFC7396] document. of the update with a media type that still needs to be defined.
Other PATCH document formats may be used as appropriate for patching
the array of objects format of a Registration Resource. In
particular, a select-merge patch document format could combine the
function of link selection query and link attribute replacement
values.
One or more links are selected for update by using query filtering as
specified in [RFC6690] Section 4.1
The query filter selects the links to be modified or deleted, by
matching the query parameter values to the values of the link
attributes.
When the query parameters are not present in the request, the payload
specifies links to be added to the target document. When the query
parameters are present, the attribute names and values in the query
parameters select one or more links on which to apply the PATCH
operation.
If no links are selected by the query parameters, the PATCH operation
SHOULD NOT update the state of any resource, and SHOULD return a
reply of "Changed".
If an attribute name specified in the PATCH document exists in any
the set of selected links, all occurrences of the attribute value in
the target document MUST be updated using the value from the PATCH
payload. If the attribute name is not present in any selected links,
the attribute MUST be added to the links.
If the PATCH payload contains plural link references, or processing
the PATCH payload would result in plural link references, the request
SHOULD be rejected with a "Conflict" result.
If the PATCH payload results in the modification of link target,
context, or relation values, that is "href", "rel", or "anchor", the
request SHOULD be rejected with a "Conflict" result code.
The update request interface is specified as follows:
Interaction: EP -> RD
Method: PATCH
URI Template: {+location}{?href,rel,rt,if,ct}
URI Template Variables:
location := This is the Location returned by the RD as a result
of a successful earlier registration.
href,rel,rt,if,ct := link relations and attributes specified in
the query in order to select particular links based on their
relations and attributes. "href" denotes the URI target of the
link. See [RFC6690] Sec. 4.1
Content-Format: application/merge-patch+json (mandatory)
The following response codes are defined for this interface:
Success: 2.04 "Changed" 0r 204 "No Content" in the update was
successfully processed.
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request.
Failure: 4.04 "Not Found" or 404 "Not Found". Registration resource
does not exist (e.g. may have expired).
Failure: 4.09 "Conflict" or 409 "Conflict". Attempt to update the
registration content with links resulting in plurality of
references; see Section 5.3.4.
Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable".
Service could not perform the operation.
HTTP support: YES
The following examples show an endpoint adding </sensors/humid>,
modifying </sensors/temp>, and removing </sensors/light> links in RD
using the Update Endpoint Links function with the example location
value /rd/4521.
The Registration Resource initial state is:
Req: GET /rd/4521
Res: 2.01 Content
Payload:
</sensors/temp>;ct=41;rt="temperature",
</sensors/light>;ct=41;rt="light-lux";if="sensor"
The following example shows an EP adding the link </sensors/
humid>;ct=41;rt="humid-s";if="sensor" to the collection of links at
the location /rd/4521.
Req: PATCH /rd/4521
Payload:
[{"href":"/sensors/humid","ct": 41, "rt": "humid-s", "if": "sensor"}]
Content-Format:
application/merge-patch+json
Res: 2.04 Changed
Req: GET /rd/4521
Res: 2.01 Content
Payload:
</sensors/temp>;ct=41;rt="temperature",
</sensors/light>;ct=41;rt="light-lux";if="sensor",
</sensors/humid>;ct=41;rt="humid-s";if="sensor"
The following example shows an EP modifying all links at the example
location /rd/4521 which are identified by href="/sensors/temp", from
the initial link-value of </sensors/temp>;rt="temperature" to the new
link-value </sensors/temp>;rt="temperature-c";if="sensor" by changing
the value of the link attribute "rt" and adding the link attribute
if="sensor" using the PATCH operation with the supplied merge-
patch+json document payload.
Req: PATCH /rd/4521?href=/sensors/temp
Payload:
{"rt": "temperature-c", "if": "sensor"},
Content-Format:
application/merge-patch+json
Res: 2.04 Changed
Req: GET /rd/4521
Res: 2.01 Content
Payload:
</sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/light>;ct=41;rt="light-lux";if="sensor",
</sensors/humid>;ct=41;rt="humid-s";if="sensor"
This example shows an EP removing all links at the example location
/rd/4521 which are identified by href="/sensors/light".
Req: PATCH /rd/4521?href=/sensors/light
Payload:
{}
Content-Format:
application/merge-patch+json
Res: 2.04 Changed
Req: GET /rd/4521
Res: 2.01 Content
Payload:
</sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/humid>;ct=41;rt="humid-s";if="sensor"
6. RD Groups 6. RD Groups
This section defines the REST API for the creation, management, and This section defines the REST API for the creation, management, and
lookup of endpoints for group operations. Similar to endpoint lookup of endpoints for group operations. Similar to endpoint
registration entries in the RD, groups may be created or removed. registration entries in the RD, groups may be created or removed.
However unlike an endpoint entry, a group entry consists of a list of However unlike an endpoint entry, a group entry consists of a list of
endpoints and does not have a lifetime associated with it. In order endpoints and does not have a lifetime associated with it. In order
to make use of multicast requests with CoAP, a group MAY have a to make use of multicast requests with CoAP, a group MAY have a
multicast address associated with it. multicast address associated with it.
6.1. Register a Group 6.1. Register a Group
In order to create a group, a commissioning tool (CT) used to In order to create a group, a commissioning tool (CT) used to
configure groups, makes a request to the RD indicating the name of configure groups, makes a request to the RD indicating the name of
the group to create (or update), optionally the domain the group the group to create (or update), optionally the domain the group
belongs to, and optionally the multicast address of the group. The belongs to, and optionally the multicast address of the group. The
registration message includes the list of endpoints that belong to registration message is a list of links to registration resources of
that group. the endpoints that belong to that group.
All the endpoints in the group MUST be registered with the RD before The commissioning tool SHOULD not send any target attributes with the
registering a group. If an endpoint is not yet registered to the RD links to the registration resources, and the resource directory
before registering the group, the registration message returns an SHOULD ignore any attributes that are set.
error. The RD sends a blank target URI for every endpoint link when
registering the group.
Configuration of the endpoints themselves is out of scope of this Configuration of the endpoints themselves is out of scope of this
specification. Such an interface for managing the group membership specification. Such an interface for managing the group membership
of an endpoint has been defined in [RFC7390]. of an endpoint has been defined in [RFC7390].
The registration request interface is specified as follows: The registration request interface is specified as follows:
Interaction: CT -> RD Interaction: CT -> RD
Method: POST Method: POST
skipping to change at page 29, line 15 skipping to change at page 30, line 6
gp := Group Name (mandatory). The name of the group to be gp := Group Name (mandatory). The name of the group to be
created or replaced, unique within that domain. The maximum created or replaced, unique within that domain. The maximum
length of this parameter is 63 bytes. length of this parameter is 63 bytes.
d := Domain (optional). The domain to which this group belongs. d := Domain (optional). The domain to which this group belongs.
The maximum length of this parameter is 63 bytes. Optional. The maximum length of this parameter is 63 bytes. Optional.
When this parameter is elided, the RD MAY associate the When this parameter is elided, the RD MAY associate the
endpoint with a configured default domain. endpoint with a configured default domain.
con := Context (optional). This parameter sets the scheme, con := Context (optional). This parameter sets the scheme,
address and port at which this server is available in the form address and port of the multicast address associated with the
scheme://host:port/path. In the absence of this parameter the group. When con is used, scheme and host are mandatory and
scheme of the protocol, source address and source port of the port parameter is optional.
register request are assumed. This parameter is mandatory when
the directory is filled by a third party such as an
commissioning tool. When con is used, scheme and host are
mandatory and port and path parameters are optional.
Content-Format: application/link-format Content-Format: application/link-format
Content-Format: application/link-format+json Content-Format: application/link-format+json
Content-Format: application/link-format+cbor Content-Format: application/link-format+cbor
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.01 "Created" or 201 "Created". The Location header Success: 2.01 "Created" or 201 "Created". The Location header
option MUST be returned in response to a successful group CREATE option MUST be returned in response to a successful group CREATE
operation. This Location MUST be a stable identifier generated by operation. This Location MUST be a stable identifier generated by
the RD as it is used for delete operations of the group the RD as it is used for delete operations of the group resource.
registration resource.
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request. request.
Failure: 4.04 "Not Found" or 404 "Not Found". An Endpoint is not Failure: 4.04 "Not Found" or 404 "Not Found". An Endpoint is not
registered in the RD (e.g. may have expired). registered in the RD (e.g. may have expired).
Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable". Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable".
Service could not perform the operation. Service could not perform the operation.
HTTP support: YES HTTP support: YES
The following example shows an EP registering a group with the name The following example shows an EP registering a group with the name
"lights" which has two endpoints to an RD using this interface. The "lights" which has two endpoints. The RD group path /rd-group is an
RD group path /rd-group is an example RD location discovered in a example RD location discovered in a request similar to Figure 6.
request similar to Figure 4.
Req: POST coap://rd.example.com/rd-group?gp=lights Req: POST coap://rd.example.com/rd-group?gp=lights
&con=coap://[ff35:30:2001:db8::1]
Content-Format: 40 Content-Format: 40
Payload: Payload:
<>;ep="node1", </rd/4521>,
<>;ep="node2" </rd/4522>
Res: 2.01 Created Res: 2.01 Created
Location: /rd-group/12 Location: /rd-group/12
The href value is the path to the registration resource of the
Endpoint.
6.2. Group Removal 6.2. Group Removal
A group can be removed simply by sending a removal message to the A group can be removed simply by sending a removal message to the
location of the group registration resource which was returned when location of the group registration resource which was returned when
intially registering the group. Removing a group MUST NOT remove the initially registering the group. Removing a group MUST NOT remove
endpoints of the group from the RD. the endpoints of the group from the RD.
The removal request interface is specified as follows: The removal request interface is specified as follows:
Interaction: CT -> RD Interaction: CT -> RD
Method: DELETE Method: DELETE
URI Template: {+location} URI Template: {+location}
URI Template Variables: URI Template Variables:
location := This is the Location returned by the RD as a result location := This is the path of the group resource returned by
of a successful group registration. the RD as a result of a successful group registration.
The following responses codes are defined for this interface: The following responses codes are defined for this interface:
Success: 2.02 "Deleted" or 204 "No Content" upon successful deletion Success: 2.02 "Deleted" or 204 "No Content" upon successful deletion
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request. request.
Failure: 4.04 "Not Found" or 404 "Not Found". Group does not exist. Failure: 4.04 "Not Found" or 404 "Not Found". Group does not exist.
skipping to change at page 31, line 11 skipping to change at page 31, line 48
The following examples shows successful removal of the group from the The following examples shows successful removal of the group from the
RD with the example location value /rd-group/12. RD with the example location value /rd-group/12.
Req: DELETE /rd-group/12 Req: DELETE /rd-group/12
Res: 2.02 Deleted Res: 2.02 Deleted
7. RD Lookup 7. RD Lookup
In order for an RD to be used for discovering resources registered To discover the resources registered with the RD, a lookup interface
with it, an optional lookup interface may be provided. This lookup must be provided. This lookup interface is defined as a default, and
interface is defined as a default, and it is assumed that RDs may it is assumed that RDs may also support lookups to return resource
also support lookups to return resource descriptions in alternative descriptions in alternative formats (e.g. Atom or HTML Link) or
formats (e.g. Atom or HTML Link) or using more advanced interfaces using more advanced interfaces (e.g. supporting context or semantic
(e.g. supporting context or semantic based lookup). based lookup).
RD Lookup allows lookups for domains, groups, endpoints and resources
using attributes defined in this document and for use with the CoRE
Link Format. The result of a lookup request is the list of links (if
any) corresponding to the type of lookup. Thus, a domain lookup MUST
return a list of domains, a group lookup MUST return a list of
groups, an endpoint lookup MUST return a list of endpoints and a
resource lookup MUST return a list of links to resources.
RD Lookup does not expose registration resources directly, but RD Lookup allows lookups for groups, endpoints and resources using
returns link content from registration resource entries which satisfy attributes defined in this document and for use with the CoRE Link
RD Lookup queries. Format. The result of a lookup request is the list of links (if any)
corresponding to the type of lookup. Thus, a group lookup MUST
return a list of groups, an endpoint lookup MUST return a list of
endpoints and a resource lookup MUST return a list of links to
resources.
The lookup type is selected by a URI endpoint, which is indicated by The lookup type is selected by a URI endpoint, which is indicated by
a Resource Type as per Table 1 below: a Resource Type as per Table 1 below:
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
| Lookup Type | Resource Type | Mandatory | | Lookup Type | Resource Type | Mandatory |
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
| Resource | core.rd-lookup-res | Mandatory | | Resource | core.rd-lookup-res | Mandatory |
| Endpoint | core.rd-lookup-ep | Mandatory | | Endpoint | core.rd-lookup-ep | Mandatory |
| Domain | core.rd-lookup-d | Optional |
| Group | core.rd-lookup-gp | Optional | | Group | core.rd-lookup-gp | Optional |
+-------------+--------------------+-----------+ +-------------+--------------------+-----------+
Table 1: Lookup Types Table 1: Lookup Types
Each endpoint and resource lookup result returns respectively the 7.1. Resource lookup
scheme (IP address and port) followed by the path part of the URI of
every endpoint and resource inside angle brackets ("<>") and followed
by the other parameters.
The target of these links SHOULD be the actual location of the Resource lookup results in links that are semantically equivalent to
domain, endpoint or resource, but MAY be an intermediate proxy e.g. the links submitted to the RD if they were accessed on the endpoint
in the case of an HTTP lookup interface for CoAP endpoints. itself. The links and link parameters returned are equal to the
submitted ones except for anchor, which was resolved by the server
against the endpoint's context.
The domain lookup returns every lookup domain with a base RD resource Links that did not have an anchor attribute are therefore returned
value (e.g. "/rd") encapsulated within angle brackets. with the (explicitly or implicitly set) context URI of the
registration as the anchor. Links whose anchor was submitted as an
absolute URI are returned as they were registered. The hrefs of
links can always be served as they were submitted; the server MAY
return relative references in absolute form in to resource lookups,
but that results in needlessly verbose responses.
In case that a group does not implement any multicast address, the Above rules allow the client to interpret the response as links
group lookup returns every group lookup with a group base resource without any further knowledge of what the RD does. The Resource
value encapsulated within angle brackets (e.g. "/rd/look-up"). Directory MAY replace the contexts with a configured intermediate
Otherwise, the group lookup returns the multicast address of the proxy, e.g. in the case of an HTTP lookup interface for CoAP
group inside angle brackets. endpoints.
7.2. Endpoint and group lookup
Endpoint and group lookups result in links to registration resources
and group resources, respectively. Endpoint registration resources
are annotated with their endpoint names (ep), domains (d, if
present), context (con) and lifetime (lt, if present). Additional
endpoint attributes are added as link attributes to their endpoint
link unless their specification says otherwise. Group resources are
annotated with their group names (gp), domain (d, if present) and
multicast address (con, if present).
While Endpoint Lookup does expose the registration resources, the RD
does not need to make them accessible to clients. Clients SHOULD NOT
attempt to dereference or manipulate them.
7.3. Lookup filtering
Using the Accept Option, the requester can control whether this list Using the Accept Option, the requester can control whether this list
is returned in CoRE Link Format ("application/link-format", default) is returned in CoRE Link Format ("application/link-format", default)
or its alternate content-formats ("application/link-format+json" or or its alternate content-formats ("application/link-format+json" or
"application/link-format+cbor"). "application/link-format+cbor").
The page and count parameters are used to obtain lookup results in The page and count parameters are used to obtain lookup results in
specified increments using pagination, where count specifies how many specified increments using pagination, where count specifies how many
links to return and page specifies which subset of links organized in links to return and page specifies which subset of links organized in
sequential pages, each containing 'count' links, starting with link sequential pages, each containing 'count' links, starting with link
zero and page zero. Thus, specifying count of 10 and page of 0 will zero and page zero. Thus, specifying count of 10 and page of 0 will
return the first 10 links in the result set (links 0-9). Count = 10 return the first 10 links in the result set (links 0-9). Count = 10
and page = 1 will return the next 'page' containing links 10-19, and and page = 1 will return the next 'page' containing links 10-19, and
so on. so on.
Multiple query parameters MAY be included in a lookup, all included Multiple search criteria MAY be included in a lookup. All included
parameters MUST match for a resource to be returned. The criteria MUST match for a link to be returned.
character'*' MAY be included at the end of a parameter value as a
wildcard operator.
RD Lookup requests MAY use any set of query parameters to match the A link matches a search criterion if it has an attribute of the same
registered attributes and relations. In addition, this interface MAY name and the same value, allowing for a trailing "*" wildcard
be used with queries that specify domains, endpoints, and groups. operator as in Section 4.1 of [RFC6690]. Attributes that are defined
For example, a domain lookup filtering on groups would return a list as "link-type" match if the search value matches any of their values
of domains that contain the specified groups. An endpoint lookup (see Section 4.1 of [RFC6690]; eg. "?if=core.s" matches ";if="abc
filtering on groups would return a list of endpoints that are in the core.s";"). A link also matches a search criterion if the link that
specified groups. would be produced for any of its containing entities would match the
criterion: A search criterion matches an endpoint if it matches the
endpoint itself or any of the groups it is contained in, and one on a
resource if it matches the resource, the resource's endpoint, or any
of the endpoint's groups.
Note that "href" is also a valid search criterion and matches target
references. Like all search criteria, on a resource lookup it can
match the target reference of the resource link itself, but also the
registration resource of the endpoint that registered it, or any
group resource that endpoint is contained in.
Clients that are interested in a lookup result repeatedly or Clients that are interested in a lookup result repeatedly or
continuously can use mechanisms like ETag caching, resource continuously can use mechanisms like ETag caching, resource
observation ([RFC7641]), or any future mechanism that might allow observation ([RFC7641]), or any future mechanism that might allow
more efficient observations of collections. These are advertised, more efficient observations of collections. These are advertised,
detected and used according to their own specifications and can be detected and used according to their own specifications and can be
used with the lookup interface as with any other resource. used with the lookup interface as with any other resource.
The lookup interface is specified as follows: The lookup interface is specified as follows:
Interaction: Client -> RD Interaction: Client -> RD
Method: GET Method: GET
URI Template: {+type-lookup-
location}{?d,res,ep,gp,et,rt,page,count,resource-param} URI Template: {+type-lookup-location}{?page,count,search*}
URI Template Variables: URI Template Variables:
type-lookup-location := RD Lookup URI for a given lookup type type-lookup-location := RD Lookup URI for a given lookup type
(mandatory). The address is discovered as described in (mandatory). The address is discovered as described in
Section 5.2. Section 5.2.
ep := Endpoint name (optional). Used for endpoint, group and search := Search criteria for limiting the number of results
resource lookups. (optional).
d := Domain (optional). Used for domain, group, endpoint and
resource lookups.
res := resource (optional). Used for domain, group, endpoint and
resource lookups.
gp := Group name (optional). Used for endpoint, group and
resource lookups.
page := Page (optional). Parameter can not be used without the page := Page (optional). Parameter can not be used without the
count parameter. Results are returned from result set in pages count parameter. Results are returned from result set in pages
that contain 'count' links starting from index (page * count). that contain 'count' links starting from index (page * count).
Page numbering starts with zero. Page numbering starts with zero.
count := Count (optional). Number of results is limited to this count := Count (optional). Number of results is limited to this
parameter value. If the page parameter is also present, the parameter value. If the page parameter is also present, the
response MUST only include 'count' links starting with the response MUST only include 'count' links starting with the
(page * count) link in the result set from the query. If the (page * count) link in the result set from the query. If the
count parameter is not present, then the response MUST return count parameter is not present, then the response MUST return
all matching links in the result set. Link numbering starts all matching links in the result set. Link numbering starts
with zero. with zero.
rt := Resource type (optional). Used for group, endpoint and
resource lookups.
et := Endpoint type (optional). Used for group, endpoint and
resource lookups.
resource-param := Link attribute parameters (optional). Any link
target attribute as defined in Section 4.1 of [RFC6690], used
for resource lookups.
Content-Format: application/link-format (optional) Content-Format: application/link-format (optional)
Content-Format: application/link-format+json (optional) Content-Format: application/link-format+json (optional)
Content-Format: application/link-format+cbor (optional) Content-Format: application/link-format+cbor (optional)
The following responses codes are defined for this interface: The following responses codes are defined for this interface:
Success: 2.05 "Content" or 200 "OK" with an "application/link- Success: 2.05 "Content" or 200 "OK" with an "application/link-
format", "application/link-format+cbor", or "application/link- format", "application/link-format+cbor", or "application/link-
format+json" payload containing matching entries for the lookup. format+json" payload containing matching entries for the lookup.
The payload can contain zero links (which is an empty payload,
Failure: 4.04 "Not Found" or 404 "Not Found" in case no matching "80" (hex) or "[]" in the respective content format), indicating
entry is found for a unicast request. that no entities matched the request.
Failure: No error response to a multicast request. Failure: No error response to a multicast request.
Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed Failure: 4.00 "Bad Request" or 400 "Bad Request". Malformed
request. request.
Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable". Failure: 5.03 "Service Unavailable" or 503 "Service Unavailable".
Service could not perform the operation. Service could not perform the operation.
HTTP support: YES HTTP support: YES
7.4. Lookup examples
The examples in this section assume CoAP hosts with a default CoAP The examples in this section assume CoAP hosts with a default CoAP
port 61616. HTTP hosts are possible and do not change the nature of port 61616. HTTP hosts are possible and do not change the nature of
the examples. the examples.
The following example shows a client performing a resource lookup The following example shows a client performing a resource lookup
with the example resource look-up locations discovered in Figure 4: with the example resource look-up locations discovered in Figure 6:
Req: GET /rd-lookup/res?rt=temperature Req: GET /rd-lookup/res?rt=temperature
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::123]:61616/temp>;rt="temperature" </temp>;rt="temperature";anchor="coap://[2001:db8:3::123]:61616"
The following example shows a client performing an endpoint type The same lookup using the CBOR Link Format media type:
lookup:
Req: GET /rd-lookup/ep?et=power-node Req: GET /rd-lookup/res?rt=temperature
Accept: TBD64
Res: 2.05 Content
Content-Format: TBD64
Payload in Hex notation:
81A301652F74656D70096B74656D706572617475726503781E636F61703A2F2F5B323030
313A6462383A333A3A3132335D3A3631363136
Decoded payload:
[{1: "/temp", 9: "temperature", 3: "coap://[2001:db8:3::123]:61616"}]
A client that wants to be notified of new resources as they show up
can use observation:
Req: GET /rd-lookup/res?rt=light
Observe: 0
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::127]:61616>;ep="node5", Observe: 23
<coap://[FDFD::129]:61616>;ep="node7" Payload: empty
The following example shows a client performing a domain lookup: (at a later point in time)
Req: GET /rd-lookup/d Res: 2.05 Content
Observe: 24
Payload:
</west>;rt="light";anchor="coap://[2001:db8:3::124]",
</south>;rt="light";anchor="coap://[2001:db8:3::124]",
</east>;rt="light";anchor="coap://[2001:db8:3::124]"
The following example shows a client performing an endpoint type
lookup:
Req: GET /rd-lookup/ep?et=power-node
Res: 2.05 Content Res: 2.05 Content
<>;d="domain1", </rd/1234>;con="coap://[2001:db8:3::127]:61616";ep="node5";
<>;d="domain2" et="power-node";ct="40";lt="600",
</rd/4521>;con="coap://[2001:db8:3::129]:61616";ep="node7";
et="power-node";ct="40";lt="600";d="floor-3"
The following example shows a client performing a group lookup for The following example shows a client performing a group lookup for
all groups: all groups:
Req: GET /rd-lookup/gp Req: GET /rd-lookup/gp
Res: 2.05 Content Res: 2.05 Content
<>;gp="lights1";d="example.com" </rd-group/1>;gp="lights1";d="example.com";con="coap://[ff35:30:2001:db8::1]",
<>;gp="lights2";d="ecample.com" </rd-group/2>;gp="lights2";d="example.com";con="coap://[ff35:30:2001:db8::2]"
The following example shows a client performing a lookup for all The following example shows a client performing a lookup for all
endpoints in a particular group: endpoints in a particular group:
Req: GET /rd-lookup/ep?gp=lights1 Req: GET /rd-lookup/ep?gp=lights1
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::123]:61616>;ep="node1", </rd/abcd>;con="coap://[2001:db8:3::123]:61616";ep="node1";et="power-node";ct="40";lt="600",
<coap://[FDFD::124]:61616>;ep="node2" </rd/efgh>;con="coap://[2001:db8:3::124]:61616";ep="node2";et="power-node";ct="40";lt="600"
The following example shows a client performing a lookup for all The following example shows a client performing a lookup for all
groups an endpoint belongs to: groups the endpoint "node1" belongs to:
Req: GET /rd-lookup/gp?ep=node1 Req: GET /rd-lookup/gp?ep=node1
Res: 2.05 Content Res: 2.05 Content
<>;gp="lights1" </rd-group/1>;gp="lights1"
The following example shows a client performing a paginated resource
lookup
The following example shows a client performing a paginated lookup
Req: GET /rd-lookup/res?page=0&count=5 Req: GET /rd-lookup/res?page=0&count=5
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::123]:61616/res/0>;rt=sensor;ct=60 </res/0>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/1>;rt=sensor;ct=60 </res/1>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/2>;rt=sensor;ct=60 </res/2>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/3>;rt=sensor;ct=60 </res/3>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/4>;rt=sensor;ct=60 </res/4>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616"
Req: GET /rd-lookup/res?page=1&count=5 Req: GET /rd-lookup/res?page=1&count=5
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::123]:61616/res/5>;rt=sensor;ct=60 </res/5>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/6>;rt=sensor;ct=60 </res/6>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/7>;rt=sensor;ct=60 </res/7>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/8>;rt=sensor;ct=60 </res/8>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616",
<coap://[FDFD::123]:61616/res/9>;rt=sensor;ct=60 </res/9>;rt=sensor;ct=60;anchor="coap://[2001:db8:3::123]:61616"
The following example shows a client performing a lookup of all
resources from endpoints of a given endpoint type. It assumes that
two endpoints (with endpoint names "sensor1" and "sensor2") have
previously registered with their respective addresses
"coap://sensor1.example.com" and "coap://sensor2.example.com", and
posted the very payload of the 6th request of section 5 of [RFC6690].
It demonstrates how the link targets stay unmodified, but the anchors
get constructed by the resource directory:
Req: GET /rd-lookup/res?et=sensor-node
</sensors>;ct=40;title="Sensor Index";
anchor="coap://sensor1.example.com",
</sensors/temp>;rt="temperature-c";if="sensor";
anchor="coap://sensor1.example.com",
</sensors/light>;rt="light-lux";if="sensor";
anchor="coap://sensor1.example.com",
<http://www.example.com/sensors/t123>;rel="describedby";
anchor="coap://sensor1.example.com/sensors/temp",
</t>;rel="alternate";anchor="coap://sensor1.example.com/sensors/temp",
</sensors>;ct=40;title="Sensor Index";
anchor="coap://sensor2.example.com",
</sensors/temp>;rt="temperature-c";if="sensor";
anchor="coap://sensor2.example.com",
</sensors/light>;rt="light-lux";if="sensor";
anchor="coap://sensor2.example.com",
<http://www.example.com/sensors/t123>;rel="describedby";
;anchor="coap://sensor2.example.com/sensors/temp",
</t>;rel="alternate";anchor="coap://sensor2.example.com/sensors/temp"
8. Security Considerations 8. Security Considerations
The security considerations as described in Section 7 of [RFC5988] The security considerations as described in Section 7 of [RFC5988]
and Section 6 of [RFC6690] apply. The "/.well-known/core" resource and Section 6 of [RFC6690] apply. The "/.well-known/core" resource
may be protected e.g. using DTLS when hosted on a CoAP server as may be protected e.g. using DTLS when hosted on a CoAP server as
described in [RFC7252]. DTLS or TLS based security SHOULD be used on described in [RFC7252]. DTLS or TLS based security SHOULD be used on
all resource directory interfaces defined in this document. all resource directory interfaces defined in this document.
8.1. Endpoint Identification and Authentication 8.1. Endpoint Identification and Authentication
An Endpoint is determined to be unique by an RD by the Endpoint An Endpoint is determined to be unique within (the domain of) an RD
identifier parameter included during Registration, and any associated by the Endpoint identifier parameter included during Registration,
TLS or DTLS security bindings. An Endpoint MUST NOT be identified by and any associated TLS or DTLS security bindings. An Endpoint MUST
its protocol, port or IP address as these may change over the NOT be identified by its protocol, port or IP address as these may
lifetime of an Endpoint. change over the lifetime of an Endpoint.
Every operation performed by an Endpoint or Client on a resource Every operation performed by an Endpoint or Client on a resource
directory SHOULD be mutually authenticated using Pre-Shared Key, Raw directory SHOULD be mutually authenticated using Pre-Shared Key, Raw
Public Key or Certificate based security. Endpoints using a Public Key or Certificate based security.
Certificate MUST include the Endpoint identifier as the Subject of
the Certificate, and this identifier MUST be checked by a resource Consider te following threat: two devices A and B are managed by a
directory to match the Endpoint identifier included in the single server. Both devices have unique, per-device credentials for
Registration message. use with DTLS to make sure that only parties with authorization to
access A or B can do so.
Now, imagine that a malicious device A wants to sabotage the device
B. It uses its credentials during the TLS exchange. Then, it puts
the endpoint name of device B. If the server does not check whether
the identifier provided in the DTLS handshake matches the identifier
used at the CoAP layer then it may be inclined to use the endpoint
name for looking up what information to provision to the malicious
device.
Therfore, Endpoints MUST include the Endpoint identifier in the
message, and this identifier MUST be checked by a resource directory
to match the Endpoint identifier included in the Registration
message.
8.2. Access Control 8.2. Access Control
Access control SHOULD be performed separately for the RD Access control SHOULD be performed separately for the RD
registration, Lookup, and group API paths, as different endpoints may registration, Lookup, and group API paths, as different endpoints may
be authorized to register with an RD from those authorized to lookup be authorized to register with an RD from those authorized to lookup
endpoints from the RD. Such access control SHOULD be performed in as endpoints from the RD. Such access control SHOULD be performed in as
fine-grained a level as possible. For example access control for fine-grained a level as possible. For example access control for
lookups could be performed either at the domain, endpoint or resource lookups could be performed either at the domain, endpoint or resource
level. level.
skipping to change at page 37, line 31 skipping to change at page 40, line 4
unprotected UDP, there is no return routability check, and they can unprotected UDP, there is no return routability check, and they can
have a large amplification factor. The responses from the NTP server have a large amplification factor. The responses from the NTP server
were found to be 19 times larger than the request. A Resource were found to be 19 times larger than the request. A Resource
Directory (RD) which responds to wild-card lookups is potentially Directory (RD) which responds to wild-card lookups is potentially
vulnerable if run with CoAP over UDP. Since there is no return vulnerable if run with CoAP over UDP. Since there is no return
routability check and the responses can be significantly larger than routability check and the responses can be significantly larger than
requests, RDs can unknowingly become part of a DDoS amplification requests, RDs can unknowingly become part of a DDoS amplification
attack. attack.
9. IANA Considerations 9. IANA Considerations
9.1. Resource Types 9.1. Resource Types
"core.rd", "core.rd-group", "core.rd-lookup-ep", "core.rd-lookup- "core.rd", "core.rd-group", "core.rd-lookup-ep", "core.rd-lookup-
res", "core.rd-lookup-d", and "core.rd-lookup-gp" resource types need res", and "core.rd-lookup-gp" resource types need to be registered
to be registered with the resource type registry defined by with the resource type registry defined by [RFC6690].
[RFC6690].
9.2. IPv6 ND Resource Directory Address Option 9.2. IPv6 ND Resource Directory Address Option
This document registers one new ND option type under the subregistry This document registers one new ND option type under the subregistry
"IPv6 Neighbor Discovery Option Formats": "IPv6 Neighbor Discovery Option Formats":
o Resource Directory address Option (38) o Resource Directory address Option (38)
9.3. RD Parameter Registry 9.3. RD Parameter Registry
This specification defines a new sub-registry for registration and This specification defines a new sub-registry for registration and
lookup parameters called "RD Parameters" under "CoRE Parameters". lookup parameters called "RD Parameters" under "CoRE Parameters".
Although this specification defines a basic set of parameters, it is Although this specification defines a basic set of parameters, it is
expected that other standards that make use of this interface will expected that other standards that make use of this interface will
define new ones. define new ones.
Each entry in the registry must include the human readable name of Each entry in the registry must include * the human readable name of
the parameter, the query parameter, validity requirements if any and the parameter, * the short name as used in query parameters or link
a description. The query parameter MUST be a valid URI query key attributes, * indication of whether it can be passed as a query
[RFC3986]. parameter at registration of endpoints or groups, as a query
parameter in lookups, or be expressed as a link attribute, * validity
requirements if any, and * a description.
The query parameter MUST be both a valid URI query key [RFC3986] and
a parmname as used in [RFC5988].
The description must give details on which registrations they apply
to (Endpoint, group registrations or both? Can they be updated?),
and how they are to be processed in lookups.
The mechanisms around new RD parameters should be designed in such a
way that they tolerate RD implementations that are unaware of the
parameter and expose any parameter passed at registration or updates
on in endpoint lookups. (For example, if a parameter used at
registration were to be confidential, the registering endpoint should
be instructed to only set that parameter if the RD advertises support
for keeping it confidential at the discovery step.)
Initial entries in this sub-registry are as follows: Initial entries in this sub-registry are as follows:
+----------+-------+---------------+--------------------------------+ +----------+-------+---------------+-----+--------------------------+
| Name | Query | Validity | Description | | Full | Short | Validity | Use | Description |
+----------+-------+---------------+--------------------------------+ | name | | | | |
| Endpoint | ep | | Name of the endpoint, max 63 | +----------+-------+---------------+-----+--------------------------+
| Name | | | bytes | | Endpoint | ep | | RLA | Name of the endpoint, |
| Lifetime | lt | 60-4294967295 | Lifetime of the registration | | Name | | | | max 63 bytes |
| | | | in seconds | | Lifetime | lt | 60-4294967295 | RLA | Lifetime of the |
| Domain | d | | Domain to which this endpoint | | | | | | registration in seconds |
| | | | belongs | | Domain | d | | RLA | Domain to which this |
| Endpoint | et | | Semantic name of the endpoint | | | | | | endpoint belongs |
| Type | | | | | Context | con | URI | RLA | The scheme, address and |
| Context | con | URI | The scheme, address and port | | | | | | port and path at which |
| | | | and path at which this server | | | | | | this server is available |
| | | | is available | | Group | gp | | RLA | Name of a group in the |
| Resource | res | | Name of the resource | | Name | | | | RD |
| Name | | | | | Page | page | Integer | L | Used for pagination |
| Group | gp | | Name of a group in the RD | | Count | count | Integer | L | Used for pagination |
| Name | | | | | Endpoint | et | | RLA | Semantic name of the |
| Page | page | Integer | Used for pagination | | Type | | | | endpoint (see Section |
| Count | count | Integer | Used for pagination | | | | | | 9.4) |
+----------+-------+---------------+--------------------------------+ +----------+-------+---------------+-----+--------------------------+
Table 2: RD Parameters Table 2: RD Parameters
(Short: Short name used in query parameters or link attributes. Use:
R = used at registration, L = used at lookup, A = expressed in link
attribute
The descriptions for the options defined in this document are only
summarized here. To which registrations they apply and when they are
to be shown is described in the respective sections of this document.
The IANA policy for future additions to the sub-registry is "Expert The IANA policy for future additions to the sub-registry is "Expert
Review" as described in [RFC5226]. Review" as described in [RFC8126]. The evaluation should consider
formal criteria, duplication of functionality (Is the new entry
redundant with an existing one?), topical suitability (Eg. is the
described property actually a property of the endpoint and not a
property of a particular resource, in which case it should go into
the payload of the registration and need not be registered?), and the
potential for conflict with commonly used link attributes (For
example, "if" could be used as a parameter for conditional
registration if it were not to be used in lookup or attributes, but
would make a bad parameter for lookup, because a resource lookup with
an "if" query parameter could ambiguously filter by the registered
endpoint property or the [RFC6690] link attribute). It is expected
that the registry will receive between 5 and 50 registrations in
total over the next years.
9.3.1. Full description of the "Endpoint Type" Registration Parameter
An endpoint registering at an RD can describe itself with endpoint
types, similar to how resources are described with Resource Types in
[RFC6690]. An endpoint type is expressed as a string, which can be
either a URI or one of the values defined in the Endpoint Type
subregistry. Endpoint types can be passed in the "et" query
parameter as part of extra-attrs at the Registration step, are shown
on endpoint lookups using the "et" target attribute, and can be
filtered for using "et" as a search criterion in resource and
endpoint lookup. Multiple endpoint types are given as separate query
parameters or link attributes.
Note that Endpoint Type differs from Resource Type in that it uses
multiple attributes rather than space separated values. As a result,
Resource Directory implementations automatically support correct
filtering in the lookup interfaces from the rules for unknown
endpoint attributes.
9.4. "Endpoint Type" (et=) RD Parameter values
This specification establishes a new sub-registry under "CoRE
Parameters" called '"Endpoint Type" (et=) RD Parameter values'. The
registry properties (required policy, requirements, template) are
identical to those of the Resource Type parameters in [RFC6690], in
short:
The review policy is IETF Review for values starting with "core", and
Specification Required for others.
The requirements to be enforced are:
o The values MUST be related to the purpose described in
Section 9.3.1.
o The registered values MUST conform to the ABNF reg-rel-type
definition of [RFC6690] and MUST NOT be a URI.
o It is recommended to use the period "." character for
segmentation.
The registry is initially empty.
10. Examples 10. Examples
Two examples are presented: a Lighting Installation example in Two examples are presented: a Lighting Installation example in
Section 10.1 and a LWM2M example in Section 10.2. Section 10.1 and a LWM2M example in Section 10.2.
10.1. Lighting Installation 10.1. Lighting Installation
This example shows a simplified lighting installation which makes use This example shows a simplified lighting installation which makes use
of the Resource Directory (RD) with a CoAP interface to facilitate of the Resource Directory (RD) with a CoAP interface to facilitate
skipping to change at page 40, line 5 skipping to change at page 44, line 5
Before commissioning by the lighting manager, the network is Before commissioning by the lighting manager, the network is
installed and access to the interfaces is proven to work by the installed and access to the interfaces is proven to work by the
network manager. network manager.
At the moment of installation, the network under installation is not At the moment of installation, the network under installation is not
necessarily connected to the DNS infra structure. Therefore, SLAAC necessarily connected to the DNS infra structure. Therefore, SLAAC
IPv6 addresses are assigned to CT, RD, luminaries and sensor shown in IPv6 addresses are assigned to CT, RD, luminaries and sensor shown in
Table 3 below: Table 3 below:
+--------------------+--------------+ +--------------------+----------------+
| Name | IPv6 address | | Name | IPv6 address |
+--------------------+--------------+ +--------------------+----------------+
| luminary1 | FDFD::ABCD:1 | | luminary1 | 2001:db8:4::1 |
| luminary2 | FDFD::ABCD:2 | | luminary2 | 2001:db8:4::2 |
| Presence sensor | FDFD::ABCD:3 | | Presence sensor | 2001:db8:4::3 |
| Resource directory | FDFD::ABCD:0 | | Resource directory | 2001:db8:4::ff |
+--------------------+--------------+ +--------------------+----------------+
Table 3: interface SLAAC addresses Table 3: interface SLAAC addresses
In Section 10.1.2 the use of resource directory during installation In Section 10.1.2 the use of resource directory during installation
is presented. is presented.
10.1.2. RD entries 10.1.2. RD entries
It is assumed that access to the DNS infrastructure is not always It is assumed that access to the DNS infrastructure is not always
possible during installation. Therefore, the SLAAC addresses are possible during installation. Therefore, the SLAAC addresses are
skipping to change at page 41, line 13 skipping to change at page 45, line 13
Table 4: Resource Directory identifiers Table 4: Resource Directory identifiers
It is assumed that the CT knows of the RD's address, and has It is assumed that the CT knows of the RD's address, and has
performed URI discovery on it that gave a response like the one in performed URI discovery on it that gave a response like the one in
the Section 5.2 example. the Section 5.2 example.
The CT inserts the endpoints of the luminaries and the sensor in the The CT inserts the endpoints of the luminaries and the sensor in the
RD using the Context parameter (con) to specify the interface RD using the Context parameter (con) to specify the interface
address: address:
Req: POST coap://[FDFD::ABCD:0]/rd Req: POST coap://[2001:db8:4::ff]/rd
?ep=lm_R2-4-015_wndw&con=coap://[FDFD::ABCD:1]&d=R2-4-015 ?ep=lm_R2-4-015_wndw&con=coap://[2001:db8:4::1]&d=R2-4-015
Payload: Payload:
</light/left>;rt="light", </light/left>;rt="light",
</light/middle>;rt="light", </light/middle>;rt="light",
</light/right>;rt="light" </light/right>;rt="light"
Res: 2.01 Created Res: 2.01 Created
Location: /rd/4521 Location: /rd/4521
Req: POST coap://[FDFD::ABCD:0]/rd Req: POST coap://[2001:db8:4::ff]/rd
?ep=lm_R2-4-015_door&con=coap://[FDFD::ABCD:2]&d=R2-4-015 ?ep=lm_R2-4-015_door&con=coap://[2001:db8:4::2]&d=R2-4-015
Payload: Payload:
</light/left>;rt="light", </light/left>;rt="light",
</light/middle>;rt="light", </light/middle>;rt="light",
</light/right>;rt="light" </light/right>;rt="light"
Res: 2.01 Created Res: 2.01 Created
Location: /rd/4522 Location: /rd/4522
Req: POST coap://[FDFD::ABCD:0]/rd Req: POST coap://[2001:db8:4::ff]/rd
?ep=ps_R2-4-015_door&con=coap://[FDFD::ABCD:3]d&d=R2-4-015 ?ep=ps_R2-4-015_door&con=coap://[2001:db8:4::3]d&d=R2-4-015
Payload: Payload:
</ps>;rt="p-sensor" </ps>;rt="p-sensor"
Res: 2.01 Created Res: 2.01 Created
Location: /rd/4523 Location: /rd/4523
The domain name d=R2-4-015 has been added for an efficient lookup The domain name d=R2-4-015 has been added for an efficient lookup
because filtering on "ep" name is more awkward. The same domain name because filtering on "ep" name is more awkward. The same domain name
is communicated to the two luminaries and the presence sensor by the is communicated to the two luminaries and the presence sensor by the
CT. CT.
The group is specified in the RD. The Context parameter is set to The group is specified in the RD. The Context parameter is set to
the site-local multicast address allocated to the group. In the POST the site-local multicast address allocated to the group. In the POST
in the example below, these two endpoints and the endpoint of the in the example below, these two endpoints and the endpoint of the
presence sensor are registered as members of the group. presence sensor are registered as members of the group.
Req: POST coap://[FDFD::ABCD:0]/rd-group Req: POST coap://[2001:db8:4::ff]/rd-group
?gp=grp_R2-4-015&con=coap://[FF05::1] ?gp=grp_R2-4-015&con=coap://[ff05::1]
Payload: Payload:
<>;ep=lm_R2-4-015_wndw, </rd/4521>,
<>;ep=lm_R2-4-015_door, </rd/4522>,
<>;ep=ps_R2-4-015_door </rd/4523>
Res: 2.01 Created Res: 2.01 Created
Location: /rd-group/501 Location: /rd-group/501
After the filling of the RD by the CT, the application in the After the filling of the RD by the CT, the application in the
luminaries can learn to which groups they belong, and enable their luminaries can learn to which groups they belong, and enable their
interface for the multicast address. interface for the multicast address.
The luminary, knowing its domain, queries the RD for the endpoint The luminary, knowing its domain, queries the RD for the endpoint
with rt=light and d=R2-4-015. The RD returns all endpoints in the with rt=light and d=R2-4-015. The RD returns all endpoints in the
domain. domain.
Req: GET coap://[FDFD::ABCD:0]/rd-lookup/ep Req: GET coap://[2001:db8:4::ff]/rd-lookup/ep
?d=R2-4-015;rt=light ?d=R2-4-015;rt=light
Res: 2.05 Content Res: 2.05 Content
<coap://[FDFD::ABCD:1]>; </rd/4521>;con="coap://[2001:db8:4::1]",
ep="lm_R2-4-015_wndw", ep="lm_R2-4-015_wndw",
<coap://[FDFD::ABCD:2]>; </rd/4522>;con="coap://[2001:db8:4::2]",
ep="lm_R2-4-015_door" ep="lm_R2-4-015_door"
Knowing its own IPv6 address, the luminary discovers its endpoint Knowing its own IPv6 address, the luminary discovers its endpoint
name. With the endpoint name the luminary queries the RD for all name. With the endpoint name the luminary queries the RD for all
groups to which the endpoint belongs. groups to which the endpoint belongs.
Req: GET coap://[FDFD::ABCD:0]/rd-lookup/gp Req: GET coap://[2001:db8:4::ff]/rd-lookup/gp
?ep=lm_R2-4-015_wndw ?ep=lm_R2-4-015_wndw
Res: 2.05 Content Res: 2.05 Content
<coap://[FF05::1]>;gp="grp_R2-4-015" </rd-group/501>;gp="grp_R2-4-015";con="coap://[ff05::1]"
From the context parameter value, the luminary learns the multicast From the context parameter value, the luminary learns the multicast
address of the multicast group. address of the multicast group.
Alternatively, the CT can communicate the multicast address directly Alternatively, the CT can communicate the multicast address directly
to the luminaries by using the "coap-group" resource specified in to the luminaries by using the "coap-group" resource specified in
[RFC7390]. [RFC7390].
Req: POST //[FDFD::ABCD:1]/coap-group Req: POST //[2001:db8:4::1]/coap-group
Content-Format: application/coap-group+json Content-Format: application/coap-group+json
{ "a": "[FF05::1]", { "a": "[ff05::1]",
"n": "grp_R2-4-015"} "n": "grp_R2-4-015"}
Res: 2.01 Created Res: 2.01 Created
Location-Path: /coap-group/1 Location-Path: /coap-group/1
Dependent on the situation, only the address, "a", or the name, "n", Dependent on the situation, only the address, "a", or the name, "n",
is specified in the coap-group resource. is specified in the coap-group resource.
10.2. OMA Lightweight M2M (LWM2M) Example 10.2. OMA Lightweight M2M (LWM2M) Example
skipping to change at page 45, line 38 skipping to change at page 49, line 38
When an LWM2M object or instance is registered, this indicates to the When an LWM2M object or instance is registered, this indicates to the
LWM2M server that the object and its resources are available for LWM2M server that the object and its resources are available for
management and service enablement (REST API) operations. management and service enablement (REST API) operations.
LWM2M endpoints may use the following RD registration parameters as LWM2M endpoints may use the following RD registration parameters as
defined in Table 2 : defined in Table 2 :
ep - Endpoint Name ep - Endpoint Name
lt - registration lifetime lt - registration lifetime
Endpoint Name is mandatory, all other registration parameters are Endpoint Name, Lifetime, and LWM2M Version are mandatory parameters
for the register operation, all other registration parameters are
optional. optional.
Additional optional LWM2M registration parameters are defined: Additional optional LWM2M registration parameters are defined:
+------------+-------+-------------------------------+--------------+ +-----------+-------+-------------------------------+---------------+
| Name | Query | Validity | Description | | Name | Query | Validity | Description |
+------------+-------+-------------------------------+--------------+ +-----------+-------+-------------------------------+---------------+
| Protocol | b | {"U",UQ","S","SQ","US","UQS"} | Available | | Binding | b | {"U",UQ","S","SQ","US","UQS"} | Available |
| Binding | | | Protocols | | Mode | | | Protocols |
| | | | | | | | | |
| LWM2M | ver | 1.0 | Spec Version | | LWM2M | ver | 1.0 | Spec Version |
| Version | | | | | Version | | | |
| | | | | | | | | |
| SMS Number | sms | | MSISDN | | SMS | sms | | MSISDN |
+------------+-------+-------------------------------+--------------+ | Number | | | |
+-----------+-------+-------------------------------+---------------+
Table 5: LWM2M Additional Registration Parameters Table 5: LWM2M Additional Registration Parameters
The following RD registration parameters are not currently specified The following RD registration parameters are not currently specified
for use in LWM2M: for use in LWM2M:
et - Endpoint Type et - Endpoint Type
con - Context con - Context
The endpoint registration must include a payload containing links to The endpoint registration must include a payload containing links to
skipping to change at page 46, line 41 skipping to change at page 50, line 42
</1>,</1/0>,</3/0>,</5> </1>,</1/0>,</3/0>,</5>
This link format payload indicates that object ID 1 (LWM2M Server This link format payload indicates that object ID 1 (LWM2M Server
Object) is supported, with a single instance 0 existing, object ID 3 Object) is supported, with a single instance 0 existing, object ID 3
(LWM2M Device object) is supported, with a single instance 0 (LWM2M Device object) is supported, with a single instance 0
existing, and object 5 (LWM2M Firmware Object) is supported, with no existing, and object 5 (LWM2M Firmware Object) is supported, with no
existing instances. existing instances.
10.2.3. LWM2M Update Endpoint Registration 10.2.3. LWM2M Update Endpoint Registration
An LWM2M Registration update proceeds as described in Section 5.4.1, The LwM2M update is really very similar to the registration update as
and adds some optional parameter updates: described in Section 5.4.1, with the only difference that there are
more parameters defined and available. All the parameters listed in
that section are also available with the initial registration but are
all optional:
lt - Registration Lifetime lt - Registration Lifetime
b - Protocol Binding b - Protocol Binding
sms - MSISDN sms - MSISDN
link payload - new or modified links link payload - new or modified links
A Registration update is also specified to be used to update the A Registration update is also specified to be used to update the
LWM2M server whenever the endpoint's UDP port or IP address are LWM2M server whenever the endpoint's UDP port or IP address are
changed. changed.
10.2.4. LWM2M De-Register Endpoint 10.2.4. LWM2M De-Register Endpoint
LWM2M allows for de-registration using the delete method on the LWM2M allows for de-registration using the delete method on the
returned location from the initial registration operation. LWM2M de- returned location from the initial registration operation. LWM2M de-
registration proceeds as described in Section 5.4.2. registration proceeds as described in Section 5.4.2.
skipping to change at page 47, line 14 skipping to change at page 51, line 17
10.2.4. LWM2M De-Register Endpoint 10.2.4. LWM2M De-Register Endpoint
LWM2M allows for de-registration using the delete method on the LWM2M allows for de-registration using the delete method on the
returned location from the initial registration operation. LWM2M de- returned location from the initial registration operation. LWM2M de-
registration proceeds as described in Section 5.4.2. registration proceeds as described in Section 5.4.2.
11. Acknowledgments 11. Acknowledgments
Oscar Novo, Srdjan Krco, Szymon Sasin, Kerry Lynn, Esko Dijk, Anders Oscar Novo, Srdjan Krco, Szymon Sasin, Kerry Lynn, Esko Dijk, Anders
Brandt, Matthieu Vial, Mohit Sethi, Sampo Ukkola, Linyi Tian, Brandt, Matthieu Vial, Jim Schaad, Mohit Sethi, Hauke Petersen,
Chistian Amsuss, and Jan Newmarch have provided helpful comments, Hannes Tschofenig, Sampo Ukkola, Linyi Tian, and Jan Newmarch have
discussions and ideas to improve and shape this document. Zach would provided helpful comments, discussions and ideas to improve and shape
also like to thank his colleagues from the EU FP7 SENSEI project, this document. Zach would also like to thank his colleagues from the
where many of the resource directory concepts were originally EU FP7 SENSEI project, where many of the resource directory concepts
developed. were originally developed.
12. Changelog 12. Changelog
changes from -11 to -12
o added Content Model section, including ER diagram
o removed domain lookup interface; domains are now plain attributes
of groups and endpoints
o updated chapter "Finding a Resource Directory"; now distinguishes
configuration-provided, network-provided and heuristic sources
o improved text on: atomicity, idempotency, lookup with multiple
parameters, endpoint removal, simple registration
o updated LWM2M description
o clarified where relative references are resolved, and how context
and anchor interact
o new appendix on the interaction with RFCs 6690, 5988 and 3986
o lookup interface: group and endpoint lookup return group and
registration resources as link targets
o lookup interface: search parameters work the same across all
entities
o removed all methods that modify links in an existing registration
(POST with payload, PATCH and iPATCH)
o removed plurality definition (was only needed for link
modification)
o enhanced IANA registry text
o More examples and improved text
changes from -09 to -10 changes from -09 to -10
o removed "ins" and "exp" link-format extensions. o removed "ins" and "exp" link-format extensions.
o removed all text concerning DNS-SD. o removed all text concerning DNS-SD.
o removed inconsistency in RDAO text. o removed inconsistency in RDAO text.
o suggestions taken over from various sources o suggestions taken over from various sources
skipping to change at page 51, line 25 skipping to change at page 56, line 15
o Changed the lookup interface to accept endpoint and Domain as o Changed the lookup interface to accept endpoint and Domain as
query string parameters to control the scope of a lookup. query string parameters to control the scope of a lookup.
13. References 13. References
13.1. Normative References 13.1. Normative References
[I-D.ietf-core-links-json] [I-D.ietf-core-links-json]
Li, K., Rahman, A., and C. Bormann, "Representing Li, K., Rahman, A., and C. Bormann, "Representing
Constrained RESTful Environments (CoRE) Link Format in Constrained RESTful Environments (CoRE) Link Format in
JSON and CBOR", draft-ietf-core-links-json-08 (work in JSON and CBOR", draft-ietf-core-links-json-09 (work in
progress), April 2017. progress), July 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc2119>. editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, [RFC5988] Nottingham, M., "Web Linking", RFC 5988,
DOI 10.17487/RFC5988, October 2010, DOI 10.17487/RFC5988, October 2010, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc5988>. editor.org/info/rfc5988>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M., [RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570, and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012, DOI 10.17487/RFC6570, March 2012, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc6570>. editor.org/info/rfc6570>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<http://www.rfc-editor.org/info/rfc6690>. <https://www.rfc-editor.org/info/rfc6690>.
[RFC7396] Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396, [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
DOI 10.17487/RFC7396, October 2014, Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<http://www.rfc-editor.org/info/rfc7396>. <https://www.rfc-editor.org/info/rfc6763>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and [RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
FETCH Methods for the Constrained Application Protocol FETCH Methods for the Constrained Application Protocol
(CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017, (CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
<http://www.rfc-editor.org/info/rfc8132>. <https://www.rfc-editor.org/info/rfc8132>.
13.2. Informative References 13.2. Informative References
[ER] Chen, P., "The entity-relationship model---toward a
unified view of data", ACM Transactions on Database
Systems Vol. 1, pp. 9-36, DOI 10.1145/320434.320440, March
1976.
[I-D.arkko-core-dev-urn]
Arkko, J., Jennings, C., and Z. Shelby, "Uniform Resource
Names for Device Identifiers", draft-arkko-core-dev-urn-04
(work in progress), July 2017.
[I-D.nottingham-rfc5988bis]
Nottingham, M., "Web Linking", draft-nottingham-
rfc5988bis-08 (work in progress), August 2017.
[I-D.silverajan-core-coap-protocol-negotiation]
Silverajan, B. and M. Ocak, "CoAP Protocol Negotiation",
draft-silverajan-core-coap-protocol-negotiation-07 (work
in progress), October 2017.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, Transfer Protocol -- HTTP/1.1", RFC 2616,
DOI 10.17487/RFC2616, June 1999, DOI 10.17487/RFC2616, June 1999, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc2616>. editor.org/info/rfc2616>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012, RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>. <https://www.rfc-editor.org/info/rfc6775>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc7252>. editor.org/info/rfc7252>.
[RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for [RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
the Constrained Application Protocol (CoAP)", RFC 7390, the Constrained Application Protocol (CoAP)", RFC 7390,
DOI 10.17487/RFC7390, October 2014, DOI 10.17487/RFC7390, October 2014, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc7390>. editor.org/info/rfc7390>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained [RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641, Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015, DOI 10.17487/RFC7641, September 2015, <https://www.rfc-
<http://www.rfc-editor.org/info/rfc7641>. editor.org/info/rfc7641>.
Appendix A. Web links and the Resource Directory
Understanding the semantics of a link-format document and its URI
references is a journey through different documents ([RFC3986]
defining URIs, [RFC6690] defining link-format documents based on
[RFC5988] which defines link headers, and [RFC7252] providing the
transport). This appendix summarizes the mechanisms and semantics at
play from an entry in ".well-known/core" to a resource lookup.
This text is primarily aimed at people entering the field of
Constrained Restful Environments from applications that previously
did not use web mechanisms.
A.1. A simple example
Let's start this example with a very simple host, "2001:db8:f0::1".
A client that follows classical CoAP Discovery ([RFC7252] Section 7),
sends the following multicast request to learn about neighbours
supporting resources with resource-type "temperature".
The client sends a link-local multicast:
GET coap://[ff02::fd]:5683/.well-known/core?rt=temperature
RES 2.05 Content
</temp>;rt=temperature;ct=0
where the response is sent by the server, "[2001:db8:f0::1]:5683".
While the client - on the practical or implementation side - can just
go ahead and create a new request to "[2001:db8:f0::1]:5683" with
Uri-Path: "temp", the full resolution steps without any shortcuts
are:
A.1.1. Resolving the URIs
The client parses the single returned record. The link's target
(sometimes called "href") is ""/temp"", which is a relative URI that
needs resolving. The Base URI to resolve that against is, in absence
of an "anchor" parameter, the URI of the requested resource as
described in [RFC6690] Section 2.1.
The URI of the requested resource can be composed by following the
steps of [RFC7252] section 6.5 (with an addition at the end of 8.2)
into ""coap://[2001:db8:f0::1]/.well-known/core"".
The record's target is resolved by replacing the path ""/.well-known/
core"" from the Base URI (section 5.2 [RFC3986]) with the relative
target URI ""/temp"" into ""coap://[2001:db8:f0::1]/temp"".
A.1.2. Interpreting attributes and relations
Some more information but the record's target can be obtained from
the payload: the resource type of the target is "temperature", and
its content type is text/plain (ct=0).
A relation in a web link is a three-part statement that the context
resource has a named relation to the target resource, like "_This
page_ has _its table of contents_ at _/toc.html_". In [RFC6690]
link-format documents, there is an implicit "host relation" specified
with default parameter: rel="hosts".
In our example, the context of the link is the URI of the requested
document itself. A full English expression of the "host relation"
is:
'"coap://[2001:db8:f0::1]/.well-known/core" is hosting the resource
"coap://[2001:db8:f0::1]/temp", which is of the resource type
"temperature" and can be accessed using the text/plain content
format.'
A.2. A slightly more complex example
Omitting the "rt=temperature" filter, the discovery query would have
given some more records in the payload:
</temp>;rt=temperature;ct=0,
</light>;rt=light-lux;ct=0,
</t>;anchor="/sensors/temp";rel=alternate,
<http://www.example.com/sensors/t123>;anchor="/sensors/temp";
rel=describedby,
<t123.pdf>;rel=alternate;ct=65001;
anchor="http://www.example.com/sensors/t123"
Parsing the third record, the client encounters the "anchor"
parameter. It is a URI relative to the document's Base URI and is
thus resolved to ""coap://[2001:db8:f0::1]/sensors/temp"". That is
the context resource of the link, so the "rel" statement is not about
the target and the document Base URI any more, but about the target
and that address.
Thus, the third record could be read as
""coap://[2001:db8:f0::1]/sensors/temp" has an alternate
representation at "coap://[2001:db8:f0::1]/t"".
The fourth record can be read as ""coap://[2001:db8:f0::1]/sensors/
temp" is described by "http://www.example.com/sensors/t123""
In the last example the anchor is absolute, where a ""t123.pdf"" is
resolved relative to ""http://www.example.com/sensors/t123"", which
gives a statement that ""http://www.example.com/sensors/t123/
t123.pdf" is an alternate representation to
""http://www.example.com/sensors/t123" of which the content type is
PDF".
A.3. Enter the Resource Directory
The resource directory tries to carry the semantics obtainable by
classical CoAP discovery over to the resource lookup interface as
faithfully as possible.
For the following queries, we will assume that the simple host has
used Simple Registration to register at the resource directory that
was announced to it, sending this request from its UDP port
"[2001:db8:f0::1]:6553":
POST coap://[2001:db8:f01::ff]/.well-known/core?ep-simple-host1
The resource directory would have accepted the registration, and
queried the simple host's ".well-known/core" by itself. As a result,
the host is registered as an endpoint in the RD with the name
"simple-host1". The registration is active for 86400 seconds, and
the endpoint registration Base URI is ""coap://[2001:db8:f0::1]/""
because that is the address the registration was sent from (and no
explicit "con=" was given).
If the client now queries the RD as it would previously have issued a
multicast request, it would go through the RD discovery steps by
fetching "coap://[2001:db8:f0::ff]/.well-known/core?rt=core.rd-
lookup-res", obtain "coap://[2001:db8:f0::ff]/rd-lookup/res" as the
resource lookup endpoint, and issue a request to
"coap://[2001:db8:f0::ff]/rd-lookup/res?rt=temperature" to receive
the following data:
</temp>;rt=temperature;ct=0;anchor="coap://[2001:db8:f0::1]"
This is not _literally_ the same response that it would have received
from a multicast request, but it would contain the (almost) same
statement:
'"coap://[2001:db8:f0::1]" is hosting the resource
"coap://[2001:db8:f0::1]/temp", which is of the resource type
"temperature" and can be accessed using the text/plain content
format.'
(The difference is whether "/" or "/.well-known/core" hosts the
resources, which is subject of ongoing discussion about RFC6690).
To complete the examples, the client could also query all resources
hosted at the endpoint with the known endpoint name "simple-host1".
A request to "coap://[2001:db8:f0::ff]/rd-lookup/res?ep=simple-host1"
would return
</temp>;rt=temperature;ct=0;anchor="coap://[2001:db8:f0::1]",
</light>;rt=light-lux;ct=0;anchor="coap://[2001:db8:f0::1]",
</t>;anchor="coap://[2001:db8:f0::1]/sensors/temp";rel=alternate,
<http://www.example.com/sensors/t123>;
anchor="coap://[2001:db8:f0::1]/sensors/temp";rel=describedby,
<t123.pdf>;rel=alternate;ct=65001;
anchor="http://www.example.com/sensors/t123"
Note that the last link was not modified at all because its anchor
was already an absolute reference.
Had the simple host registered with an explicit context (eg.
"?ep=simple-host1&con=coap+tcp://simple-host1.example.com"), that
context would have been used to resolve the relative anchor values
instead, giving
</temp>;rt=temperature;ct=0;anchor="coap+tcp://simple-host1.example.com"
and analogous records.
A.4. A note on differences between link-format and Link headers
While link-format and Link headers look very similar and are based on
the same model of typed links, there are some differences between
[RFC6690] and [RFC5988] that should be kept in mind when using or
implementing a Resource Directory:
o There is no percent encoding in link-format documents.
A link-format document is a UTF-8 encoded string of Unicode
characters and does not have percent encoding, while Link headers
are practically ASCII strings that use percent encoding for non-
ASCII characters, stating the encoding explictly when required.
For example, while a Link header in a page about a Swedish city
might read
"Link: </temperature/Malm%C3%B6>;rel="live-environment-data""
a link-format document from the same source might describe the
link as
"</temperature/Malmoe>;rel="live-environment-data""
o In a link-format document, if the anchor attribute is present, the
link target reference is resolved by using the the (resolved)
anchor value as Base URI for that link, while in Link headers, it
is resolved against the URI of the requested document.
This is explicit in [RFC6690] section 2.1 for link-format, and
spelled out in section B.2 of [I-D.nottingham-rfc5988bis] , which
obsoletes the older [RFC5988]. [RFC6690] is based on [RFC5988]
and has not been updated with clarifications from
[I-D.nottingham-rfc5988bis].
Appendix B. Syntax examples for Protocol Negotiation
[ This appendix should not show up in a published version of this
document. ]
The protocol negotiation that is being worked on in
[I-D.silverajan-core-coap-protocol-negotiation] makes use of the
Resource Directory.
Until that document is update to use the latest resource-directory
specification, here are some examples of protocol negotiation with
the current Resource Directory:
An endpoint could register as follows:
Req: POST coap://rd.example.com/rd?ep=node1
&at=coap+tcp://[2001:db8:f1::2]
&at=coap://[2001:db8:f1::2]
Content-Format: 40
Payload:
</temperature>;ct=0;rt="temperature";if="core.s"
Res: 2.01 Created
Location: /rd/1234
A UDP client would then query:
Req: GET /rd-lookup/res?rt=temperature
Res: 2.05 Content
</temperature>;ct=0;rt="temperature";if="core.s";
anchor="coap://[2001:db8:f1::2]"
while a TCP capable client could say:
Req: GET /rd-lookup/res?rt=temperature&tt=tcp
Res: 2.05 Content
</temperature>;ct=0;rt="temperature";if="core.s";
anchor="coap+tcp://[2001:db8:f1::2]"
Authors' Addresses Authors' Addresses
Zach Shelby Zach Shelby
ARM ARM
150 Rose Orchard 150 Rose Orchard
San Jose 95134 San Jose 95134
USA USA
Phone: +1-408-203-9434 Phone: +1-408-203-9434
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