draft-ietf-core-dynlink-11.txt   draft-ietf-core-dynlink-12.txt 
CoRE Working Group M. Koster CoRE Working Group M. Koster
Internet-Draft SmartThings Internet-Draft SmartThings
Intended status: Informational B. Silverajan, Ed. Intended status: Informational B. Silverajan, Ed.
Expires: January 14, 2021 Tampere University Expires: July 16, 2021 Tampere University
July 13, 2020 January 12, 2021
Dynamic Resource Linking for Constrained RESTful Environments Dynamic Resource Linking for Constrained RESTful Environments
draft-ietf-core-dynlink-11 draft-ietf-core-dynlink-12
Abstract Abstract
This specification defines Link Bindings, which provide dynamic This specification defines Link Bindings, which provide dynamic
linking of state updates between resources, either on an endpoint or linking of state updates between resources, either on an endpoint or
between endpoints, for systems using CoAP (RFC7252). This between endpoints, for systems using CoAP (RFC7252). This
specification also defines Conditional Notification Attributes that specification also defines Conditional Notification and Control
work with Link Bindings or with CoAP Observe (RFC7641). Attributes that work with Link Bindings or with CoAP Observe
(RFC7641).
Editor note Editor note
The git repository for the draft is found at https://github.com/core- The git repository for the draft is found at https://github.com/core-
wg/dynlink wg/dynlink
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
skipping to change at page 1, line 40 skipping to change at page 1, line 41
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 14, 2021. This Internet-Draft will expire on July 16, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Conditional Notification Attributes . . . . . . . . . . . . . 4 3. Conditional Notification and Control Attributes . . . . . . . 4
3.1. Attribute Definitions . . . . . . . . . . . . . . . . . . 4 3.1. Attribute Definitions . . . . . . . . . . . . . . . . . . 4
3.1.1. Minimum Period (pmin) . . . . . . . . . . . . . . . . 5 3.1.1. Minimum Period (pmin) . . . . . . . . . . . . . . . . 5
3.1.2. Maximum Period (pmax) . . . . . . . . . . . . . . . . 5 3.1.2. Maximum Period (pmax) . . . . . . . . . . . . . . . . 6
3.1.3. Change Step (st) . . . . . . . . . . . . . . . . . . 5 3.1.3. Change Step (st) . . . . . . . . . . . . . . . . . . 6
3.1.4. Greater Than (gt) . . . . . . . . . . . . . . . . . . 6 3.1.4. Greater Than (gt) . . . . . . . . . . . . . . . . . . 6
3.1.5. Less Than (lt) . . . . . . . . . . . . . . . . . . . 6 3.1.5. Less Than (lt) . . . . . . . . . . . . . . . . . . . 7
3.1.6. Notification Band (band) . . . . . . . . . . . . . . 6 3.1.6. Notification Band (band) . . . . . . . . . . . . . . 7
3.2. Server processing of Conditional Notification Attributes 8 3.1.7. Minimum Evaluation Period (epmin) . . . . . . . . . . 8
4. Link Bindings . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.8. Maximum Evaluation Period (epmax) . . . . . . . . . . 8
4.1. The "bind" attribute and Binding Methods . . . . . . . . 9 3.2. Server processing of Conditional Notification Attributes 9
4.1.1. Polling . . . . . . . . . . . . . . . . . . . . . . . 10 4. Link Bindings . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.2. Observe . . . . . . . . . . . . . . . . . . . . . . . 10 4.1. The "bind" attribute and Binding Methods . . . . . . . . 10
4.1.3. Push . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.1. Polling . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.4. Execute . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.2. Observe . . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Link Relation . . . . . . . . . . . . . . . . . . . . . . 11 4.1.3. Push . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Binding Table . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.4. Execute . . . . . . . . . . . . . . . . . . . . . . . 12
6. Implementation Considerations . . . . . . . . . . . . . . . . 13 4.2. Link Relation . . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 5. Binding Table . . . . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 6. Implementation Considerations . . . . . . . . . . . . . . . . 14
8.1. Resource Type value 'core.bnd' . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8.2. Link Relation Type . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 8.1. Resource Type value 'core.bnd' . . . . . . . . . . . . . 15
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15 8.2. Link Relation Type . . . . . . . . . . . . . . . . . . . 15
11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 16
12.1. Normative References . . . . . . . . . . . . . . . . . . 18 11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . 18 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 19 12.1. Normative References . . . . . . . . . . . . . . . . . . 20
A.1. Minimum Period (pmin) example . . . . . . . . . . . . . . 19 12.2. Informative References . . . . . . . . . . . . . . . . . 20
A.2. Maximum Period (pmax) example . . . . . . . . . . . . . . 20 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 20
A.3. Greater Than (gt) example . . . . . . . . . . . . . . . . 21 A.1. Minimum Period (pmin) example . . . . . . . . . . . . . . 21
A.4. Greater Than (gt) and Period Max (pmax) example . . . . . 22 A.2. Maximum Period (pmax) example . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 A.3. Greater Than (gt) example . . . . . . . . . . . . . . . . 22
A.4. Greater Than (gt) and Period Max (pmax) example . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
IETF Standards for machine to machine communication in constrained IETF Standards for machine to machine communication in constrained
environments describe a REST protocol [RFC7252] and a set of related environments describe a REST protocol [RFC7252] and a set of related
information standards that may be used to represent machine data and information standards that may be used to represent machine data and
machine metadata in REST interfaces. CoRE Link-format [RFC6690] is a machine metadata in REST interfaces. CoRE Link-format [RFC6690] is a
standard for doing Web Linking [RFC8288] in constrained environments. standard for doing Web Linking [RFC8288] in constrained environments.
This specification introduces the concept of a Link Binding, which This specification introduces the concept of a Link Binding, which
defines a new link relation type to create a dynamic link between defines a new link relation type to create a dynamic link between
resources over which state updates are conveyed. Specifically, a resources over which state updates are conveyed. Specifically, a
Link Binding is a unidirectional link for binding the states of Link Binding is a unidirectional link for binding the states of
source and destination resources together such that updates to one source and destination resources together such that updates to one
are sent over the link to the other. CoRE Link Format are sent over the link to the other. CoRE Link Format
representations are used to configure, inspect, and maintain Link representations are used to configure, inspect, and maintain Link
Bindings. This specification additionally defines Conditional Bindings. This specification additionally defines Conditional
Notification Attributes for use with Link Bindings and with CoRE Notification and Control Attributes for use with Link Bindings and
Observe [RFC7641]. with CoRE Observe [RFC7641].
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This specification requires readers to be familiar with all the terms This specification requires readers to be familiar with all the terms
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the resource values between a source and a destination. The the resource values between a source and a destination. The
process of using a REST method to achieve this is defined as process of using a REST method to achieve this is defined as
"State Synchronization". The endpoint triggering the state "State Synchronization". The endpoint triggering the state
synchronization is the synchronization initiator. synchronization is the synchronization initiator.
Notification Band: A resource value range that results in state Notification Band: A resource value range that results in state
sychronization. The value range may be bounded by a minimum and sychronization. The value range may be bounded by a minimum and
maximum value or may be unbounded having either a minimum or maximum value or may be unbounded having either a minimum or
maximum value. maximum value.
3. Conditional Notification Attributes 3. Conditional Notification and Control Attributes
3.1. Attribute Definitions 3.1. Attribute Definitions
This specification defines Conditional Notification Attributes, which This specification defines Conditional Notification and Control
provide for fine-grained control of notification and state Attributes, which provide for fine-grained control of notification
synchronization when using CoRE Observe [RFC7641] or Link Bindings and state synchronization when using CoRE Observe [RFC7641] or Link
(see Section 4). Conditional Notification Attributes define the Bindings (see Section 4). Conditional Notification Attributes define
conditions that trigger a notification. the conditions that trigger a notification. Conditional Control
Attributes define the cadence of the measurement of the conditions
that trigger a notification.
When resource interfaces following this specification are made When resource interfaces following this specification are made
available over CoAP, the CoAP Observation mechanism [RFC7641] MAY available over CoAP, the CoAP Observation mechanism [RFC7641] MAY
also be used to observe any changes in a resource, and receive also be used to observe any changes in a resource, and receive
asynchronous notifications as a result. A resource marked as asynchronous notifications as a result. A resource marked as
Observable in its link description SHOULD support these Conditional Observable in its link description SHOULD support these Conditional
Notification Attributes. Notification and Control Attributes.
The set of parameters defined here allow a client to control how The set of Notification Attributes defined here allow a client to
often a client is interested in receiving notifications and how much control how often a client is interested in receiving notifications
a resource value should change for the new representation to be and how much a resource value should change for the new
interesting. representation to be interesting. The set of Control Attributes
defined here allow a client to control how often the server performs
a measurement of the conditions.
One or more Notification Attributes MAY be included as query One or more Notification Attributes MAY be included as query
parameters in an Observe request. parameters in an Observe request.
These attributes are defined below: Conditional Notification Attributes are defined below:
+--------------------+-----------+-----------------+ +-------------------+-----------+-----------------+
| Attribute | Parameter | Value | | Attribute | Parameter | Value |
+--------------------+-----------+-----------------+ +-------------------+-----------+-----------------+
| Minimum Period (s) | pmin | xs:decimal (>0) | | Greater Than | gt | xs:decimal |
| | | | | | | |
| Maximum Period (s) | pmax | xs:decimal (>0) | | Less Than | lt | xs:decimal |
| | | | | | | |
| Change Step | st | xs:decimal (>0) | | Change Step | st | xs:decimal (>0) |
| | | | | | | |
| Greater Than | gt | xs:decimal | | Notification Band | band | xs:boolean |
| | | | +-------------------+-----------+-----------------+
| Less Than | lt | xs:decimal |
| | | |
| Notification Band | band | xs:boolean |
+--------------------+-----------+-----------------+
Table 1: Conditional Notification Attributes Table 1: Conditional Notification Attributes
One or more Control Attributes MAY be included as query parameters in
an Observe request.
Conditional Control Attributes are defined below:
+-------------------------------+-----------+-----------------+
| Attribute | Parameter | Value |
+-------------------------------+-----------+-----------------+
| Minimum Period (s) | pmin | xs:decimal (>0) |
| | | |
| Maximum Period (s) | pmax | xs:decimal (>0) |
| | | |
| Minimum Evaluation Period (s) | epmin | xs:decimal (>0) |
| | | |
| Maximum Evaluation Period (s) | epmax | xs:decimal (>0) |
+-------------------------------+-----------+-----------------+
Table 2: Conditional Control Attributes
Conditional Notification Attributes SHOULD be evaluated on all Conditional Notification Attributes SHOULD be evaluated on all
potential notifications from a resource, whether resulting from an potential notifications from a resource, whether resulting from an
internal server-driven sampling process or from external update internal server-driven sampling process or from external update
requests to the server. requests to the server. Conditional Control Attributes are used to
configure the internal server-driven sampling process for performing
measurements of the conditions of a resource.
Note: In this draft, we assume that there are finite quantization Note: In this draft, we assume that there are finite quantization
effects in the internal or external updates to the value of a effects in the internal or external updates to the value of a
resource; specifically, that a resource may be updated at any time resource; specifically, that a resource may be updated at any time
with any valid value. We therefore avoid any continuous-time with any valid value. We therefore avoid any continuous-time
assumptions in the description of the Conditional Notification assumptions in the description of the Conditional Notification
Attributes and instead use the phrase "sampled value" to refer to a Attributes and instead use the phrase "sampled value" to refer to a
member of a sequence of values that may be internally observed from member of a sequence of values that may be internally observed from
the resource state over time. the resource state over time.
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notifications may be greater than pmin even when the sampled value notifications may be greater than pmin even when the sampled value
changes within the pmin interval. Pmin may or may not be used to changes within the pmin interval. Pmin may or may not be used to
drive the internal sampling process. drive the internal sampling process.
3.1.2. Maximum Period (pmax) 3.1.2. Maximum Period (pmax)
When present, the maximum period indicates the maximum time, in When present, the maximum period indicates the maximum time, in
seconds, between two consecutive notifications (whether or not the seconds, between two consecutive notifications (whether or not the
resource value has changed). In the absence of this parameter, the resource value has changed). In the absence of this parameter, the
maximum period is up to the server. The maximum period MUST be maximum period is up to the server. The maximum period MUST be
greater than zero and MUST be greater than the minimum period greater than zero and MUST be greater than, or equal to, the minimum
parameter (if present) otherwise the receiver MUST return a CoAP period parameter (if present) otherwise the receiver MUST return a
error code 4.00 "Bad Request" (or equivalent). CoAP error code 4.00 "Bad Request" (or equivalent).
3.1.3. Change Step (st) 3.1.3. Change Step (st)
When present, the change step indicates how much the value of a When present, the change step indicates how much the value of a
resource SHOULD change before triggering a notification, compared to resource SHOULD change before triggering a notification, compared to
the value of the previous notification. Upon reception of a query the value of the previous notification. Upon reception of a query
including the st attribute, the most recently sampled value of the including the st attribute, the most recently sampled value of the
resource is reported, and then set as the last reported value resource is reported, and then set as the last reported value
(last_rep_v). When a subsequent sample or update of the resource (last_rep_v). When a subsequent sample or update of the resource
value differs from the last reported value by an amount, positive or value differs from the last reported value by an amount, positive or
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including equal to gt or lt. including equal to gt or lt.
If the band is specified in which the value of gt is greater than If the band is specified in which the value of gt is greater than
that of lt, out-of-band notification occurs. That is, notification that of lt, out-of-band notification occurs. That is, notification
occurs when the resource value not between the gt and lt values, occurs when the resource value not between the gt and lt values,
excluding equal to gt and lt. excluding equal to gt and lt.
The Notification Band parameter can only be supported on resources The Notification Band parameter can only be supported on resources
with a scalar numeric value. with a scalar numeric value.
3.1.7. Minimum Evaluation Period (epmin)
When present, the minimum evaluation period indicates the minimum
time, in seconds, the client recommends to the server to wait between
two consecutive measurements of the conditions of a resource since
the client has no interest in the server doing more frequent
measurements. When the minimum evaluation period expires after the
previous measurement, the server MAY immediately perform a new
measurement. In the absence of this parameter, the minimum
evaluation period is not defined and thus not used by the server.
The server MAY use pmin, if defined, as a guidance on the desired
measurement cadence. The minimum evaluation period MUST be greater
than zero otherwise the receiver MUST return a CoAP error code 4.00
"Bad Request" (or equivalent).
3.1.8. Maximum Evaluation Period (epmax)
When present, the maximum evaluation period indicates the maximum
time, in seconds, the server MAY wait between two consecutive
measurements of the conditions of a resource. When the maximum
evaluation period expires after the previous measurement, the server
MUST immediately perform a new measurement. In the absence of this
parameter, the maximum evaluation period is not defined and thus not
used by the server. The maximum evaluation period MUST be greater
than zero and MUST be greater than the minimum evaluation period
parameter (if present) otherwise the receiver MUST return a CoAP
error code 4.00 "Bad Request" (or equivalent).
3.2. Server processing of Conditional Notification Attributes 3.2. Server processing of Conditional Notification Attributes
Pmin, pmax, st, gt, lt and band may be present in the same query. Pmin, pmax, epmin, epmax, st, gt, lt and band may be present in the
Howver, they are not defined at multiple prioritization levels. The same query. However, they are not defined at multiple prioritization
server sends a notification whenever any of the parameter conditions levels. The server sends a notification whenever any of the
are met, upon which it updates its last notification value and time parameter conditions are met, upon which it updates its last
to prepare for the next notification. Only one notification occurs notification value and time to prepare for the next notification.
when there are multiple conditions being met at the same time. The Only one notification occurs when there are multiple conditions being
reference code below illustrates the logic to determine when a met at the same time. The reference code below illustrates the logic
notification is to be sent. to determine when a notification is to be sent.
bool notifiable( Resource * r ) { bool notifiable( Resource * r ) {
#define BAND r->band #define BAND r->band
#define SCALAR_TYPE ( num_type == r->type ) #define SCALAR_TYPE ( num_type == r->type )
#define STRING_TYPE ( str_type == r->type ) #define STRING_TYPE ( str_type == r->type )
#define BOOLEAN_TYPE ( bool_type == r->type ) #define BOOLEAN_TYPE ( bool_type == r->type )
#define PMIN_EX ( r->last_sample_time - r->last_rep_time >= r->pmin ) #define PMIN_EX ( r->last_sample_time - r->last_rep_time >= r->pmin )
#define PMAX_EX ( r->last_sample_time - r->last_rep_time > r->pmax ) #define PMAX_EX ( r->last_sample_time - r->last_rep_time > r->pmax )
#define LT_EX ( r->v < r->lt ^ r->last_rep_v < r->lt ) #define LT_EX ( r->v < r->lt ^ r->last_rep_v < r->lt )
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This specification defines a new CoRE link attribute "bind". This is This specification defines a new CoRE link attribute "bind". This is
the identifier for a binding method which defines the rules to the identifier for a binding method which defines the rules to
synchronize the destination resource. This attribute is mandatory. synchronize the destination resource. This attribute is mandatory.
+----------------+-----------+-----------+ +----------------+-----------+-----------+
| Attribute | Parameter | Value | | Attribute | Parameter | Value |
+----------------+-----------+-----------+ +----------------+-----------+-----------+
| Binding method | bind | xs:string | | Binding method | bind | xs:string |
+----------------+-----------+-----------+ +----------------+-----------+-----------+
Table 2: The bind attribute Table 3: The bind attribute
The following table gives a summary of the binding methods defined in The following table gives a summary of the binding methods defined in
this specification. this specification.
+---------+------------+-------------+---------------+ +---------+------------+-------------+---------------+
| Name | Identifier | Location | Method | | Name | Identifier | Location | Method |
+---------+------------+-------------+---------------+ +---------+------------+-------------+---------------+
| Polling | poll | Destination | GET | | Polling | poll | Destination | GET |
| | | | | | | | | |
| Observe | obs | Destination | GET + Observe | | Observe | obs | Destination | GET + Observe |
| | | | | | | | | |
| Push | push | Source | PUT | | Push | push | Source | PUT |
| | | | | | | | | |
| Execute | exec | Source | POST | | Execute | exec | Source | POST |
+---------+------------+-------------+---------------+ +---------+------------+-------------+---------------+
Table 3: Binding Method Summary Table 4: Binding Method Summary
The description of a binding method defines the following aspects: The description of a binding method defines the following aspects:
Identifier: This is the value of the "bind" attribute used to Identifier: This is the value of the "bind" attribute used to
identify the method. identify the method.
Location: This information indicates whether the binding entry is Location: This information indicates whether the binding entry is
stored on the source or on the destination endpoint. stored on the source or on the destination endpoint.
REST Method: This is the REST method used in the Request/Response REST Method: This is the REST method used in the Request/Response
skipping to change at page 12, line 23 skipping to change at page 13, line 23
The Methods column defines the REST methods supported by the Binding The Methods column defines the REST methods supported by the Binding
Table, which are described in more detail below. Table, which are described in more detail below.
+---------------+----------+----------+----------------+ +---------------+----------+----------+----------------+
| Resource | rt= | Methods | Content-Format | | Resource | rt= | Methods | Content-Format |
+---------------+----------+----------+----------------+ +---------------+----------+----------+----------------+
| Binding Table | core.bnd | GET, PUT | link-format | | Binding Table | core.bnd | GET, PUT | link-format |
+---------------+----------+----------+----------------+ +---------------+----------+----------+----------------+
Table 4: Binding Table Description Table 5: Binding Table Description
The REST methods GET and PUT are used to manipulate a Binding Table. The REST methods GET and PUT are used to manipulate a Binding Table.
A GET request simply returns the current state of a Binding Table. A A GET request simply returns the current state of a Binding Table. A
request with a PUT method and a content format of application/link- request with a PUT method and a content format of application/link-
format is used to clear the bindings to the table or replaces its format is used to clear the bindings to the table or replaces its
entire contents. All links in the payload of a PUT rquest MUST have entire contents. All links in the payload of a PUT rquest MUST have
a relation type "boundto". a relation type "boundto".
The following example shows requests for discovering, retrieving and The following example shows requests for discovering, retrieving and
replacing bindings in a binding table. replacing bindings in a binding table.
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resolution of the resource value when setting sequential bands. For resolution of the resource value when setting sequential bands. For
example: Given BandA (Abmn=10, Bbmx=20) and BandB (Bbmn=21, Bbmx=30). example: Given BandA (Abmn=10, Bbmx=20) and BandB (Bbmn=21, Bbmx=30).
If the resource value returns an integer then notifications for If the resource value returns an integer then notifications for
values between and inclusive of 10 and 30 will be triggered. Whereas values between and inclusive of 10 and 30 will be triggered. Whereas
if the resolution is to one decimal point (0.1) then notifications if the resolution is to one decimal point (0.1) then notifications
for values 20.1 to 20.9 will not be triggered. for values 20.1 to 20.9 will not be triggered.
The use of the notification band minimum and maximum allow for a The use of the notification band minimum and maximum allow for a
synchronization whenever a change in the resource value occurs. synchronization whenever a change in the resource value occurs.
Theoretically this could occur in-line with the server internal Theoretically this could occur in-line with the server internal
sample period for the determining the resource value. Implementors sample period or the configuration of epmin and epmax values for
SHOULD consider the resolution needed before updating the resource, determining the resource value. Implementors SHOULD consider the
e.g. updating the resource when a temperature sensor value changes by resolution needed before updating the resource, e.g. updating the
0.001 degree versus 1 degree. resource when a temperature sensor value changes by 0.001 degree
versus 1 degree.
The initiation of a Link Binding can be delegated from a client to a The initiation of a Link Binding can be delegated from a client to a
link state machine implementation, which can be an embedded client or link state machine implementation, which can be an embedded client or
a configuration tool. Implementation considerations have to be given a configuration tool. Implementation considerations have to be given
to how to monitor transactions made by the configuration tool with to how to monitor transactions made by the configuration tool with
regards to Link Bindings, as well as any errors that may arise with regards to Link Bindings, as well as any errors that may arise with
establishing Link Bindings in addition to established Link Bindings. establishing Link Bindings in addition to established Link Bindings.
When a server has multiple observations with different measurement
cadences as defined by the epmin and epmax values, the server MAY
evaluate all observations when performing the measurement of any one
observation.
7. Security Considerations 7. Security Considerations
Consideration has to be given to what kinds of security credentials Consideration has to be given to what kinds of security credentials
the state machine of a configuration tool or an embedded client needs the state machine of a configuration tool or an embedded client needs
to be configured with, and what kinds of access control lists client to be configured with, and what kinds of access control lists client
implementations should possess, so that transactions on creating Link implementations should possess, so that transactions on creating Link
Bindings and handling error conditions can be processed by the state Bindings and handling error conditions can be processed by the state
machine. machine.
8. IANA Considerations 8. IANA Considerations
skipping to change at page 15, line 24 skipping to change at page 16, line 28
Acknowledgement is given to colleagues from the SENSEI project who Acknowledgement is given to colleagues from the SENSEI project who
were critical in the initial development of the well-known REST were critical in the initial development of the well-known REST
interface concept, to members of the IPSO Alliance where further interface concept, to members of the IPSO Alliance where further
requirements for interface types have been discussed, and to Szymon requirements for interface types have been discussed, and to Szymon
Sasin, Cedric Chauvenet, Daniel Gavelle and Carsten Bormann who have Sasin, Cedric Chauvenet, Daniel Gavelle and Carsten Bormann who have
provided useful discussion and input to the concepts in this provided useful discussion and input to the concepts in this
specification. Christian Amsuss supplied a comprehensive review of specification. Christian Amsuss supplied a comprehensive review of
draft -06. Hannes Tschofenig and Mert Ocak highlighted syntactical draft -06. Hannes Tschofenig and Mert Ocak highlighted syntactical
corrections in the usage of pmax and pmin in a query. Discussions corrections in the usage of pmax and pmin in a query. Discussions
with Ari Keraenen led to the addition of an extra binding method with Ari Keraenen led to the addition of an extra binding method
supporting POST operations. supporting POST operations. Alan Soloway contributed text leading to
the inclusion of epmin and epmax. David Navarro proposed allowing
for pmax to be equal to pmin.
10. Contributors 10. Contributors
Christian Groves Christian Groves
Australia Australia
email: cngroves.std@gmail.com email: cngroves.std@gmail.com
Zach Shelby Zach Shelby
ARM ARM
Vuokatti Vuokatti
FINLAND FINLAND
phone: +358 40 7796297 phone: +358 40 7796297
email: zach.shelby@arm.com email: zach.shelby@arm.com
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eMail: matthieu.vial@schneider-electric.com eMail: matthieu.vial@schneider-electric.com
Jintao Zhu Jintao Zhu
Huawei Huawei
Xi'an, Shaanxi Province Xi'an, Shaanxi Province
China China
email: jintao.zhu@huawei.com email: jintao.zhu@huawei.com
11. Changelog 11. Changelog
draft-ietf-core-dynlink-12
o Attributes epmin and epmax included
o pmax now can be equal to pmin
draft-ietf-core-dynlink-11 draft-ietf-core-dynlink-11
o Updates to author list o Updates to author list
draft-ietf-core-dynlink-10 draft-ietf-core-dynlink-10
o Binding methods now support both POST and PUT operations for o Binding methods now support both POST and PUT operations for
server push. server push.
draft-ietf-core-dynlink-09 draft-ietf-core-dynlink-09
skipping to change at page 17, line 4 skipping to change at page 18, line 35
draft-ietf-core-dynlink-06 draft-ietf-core-dynlink-06
o Document restructure and refactoring into three main sections o Document restructure and refactoring into three main sections
o Clarifications on band usage o Clarifications on band usage
o Implementation considerations introduced o Implementation considerations introduced
o Additional text on security considerations o Additional text on security considerations
draft-ietf-core-dynlink-05
o Addition of a band modifier for gt and lt, adapted from draft- o Addition of a band modifier for gt and lt, adapted from draft-
groves-core-obsattr groves-core-obsattr
o Removed statement prescribing gt MUST be greater than lt o Removed statement prescribing gt MUST be greater than lt
draft-ietf-core-dynlink-03 draft-ietf-core-dynlink-03
o General: Reverted to using "gt" and "lt" from "gth" and "lth" for o General: Reverted to using "gt" and "lt" from "gth" and "lth" for
this draft owing to concerns raised that the attributes are this draft owing to concerns raised that the attributes are
already used in LwM2M with the original names "gt" and "lt". already used in LwM2M with the original names "gt" and "lt".
 End of changes. 29 change blocks. 
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