wdiff draft-ietf-manet-dlep-lid-extension-04.txt draft-ietf-manet-dlep-lid-extension-05.txt

Mobile Ad hoc Networks Working Group R. Taylor
Internet-Draft Airbus Defence & Space
Intended status: Standards Track S. Ratliff
Expires: February 24, 2019 January 26, 2020 VT iDirect
August 23, 2018
July 25, 2019

DLEP Link Identifier Extension
draft-ietf-manet-dlep-lid-extension-04
draft-ietf-manet-dlep-lid-extension-05

Abstract

There exists a class of modems that would benefit from supporting the

The Dynamic Link Exchange Protocol (DLEP) [RFC8175] but do not present a
single Layer 2 network domain as required by DLEP. Such devices may
be:

o Modems that maintain describes a varying link
protocol for modems to some upstream backbone
network infrastructure, where advertise the ability status of wireless links between
reachable destinations to announce link state
and attached routers. The core specification
of the protocol assumes that every modem in the radio network has an
attached DLEP metrics is desired, but router, and requires that the concept MAC address of a the DLEP destination
interface on the attached router for be used to identify the backbone does not apply. Examples of such devices
can include LTE modems, IEEE 802.11 stations not destination
in ad-hoc mode, the network, for purposes of reporting the state and some satellite terminals.

o Modems that provide Layer 3 wide area network connectivity between
devices, where remote DLEP destinations do exist, but are not
directly reachable by MAC address, such as modems quality of
the link to that contain
embedded routing functionality. destination.

This document introduces an optional extension to the core describes a DLEP
specification, Extension allowing DLEP to be used between routers and modems that operate in this way.

Note:

o This document is intended as an extension to do not
meet the core strict requirement above to use DLEP
specification, to describe link
availability and readers are expected quality to be fully conversant
with one or more destinations reachable beyond
a device on the operation of core DLEP. Layer 2 domain.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on February 24, 2019. January 26, 2020.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Terminology . . . . . . . . . . . . . . . . . . . . . . 3
2. Operation . . 3
1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Requirements . . 3
2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 4
2.2. Negotiation . . . 3
2. Operation . . . . . . . . . . . . . . . . . . . . 5
3. New Data Items . . . . . . 4
2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 5
3.1. Link Identifier Length Data Item .
2.2. Negotiation . . . . . . . . . . . 5
3.2. Link Identifier Data Item . . . . . . . . . . . . 5
3. New Data Items . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations
3.1. Link Identifier Length Data Item . . . . . . . . . . . . 6
3.2. Link Identifier Data Item . . . . . . . . . . 7
6. References . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.2. Informative
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 8

1. Introduction

The Dynamic Link Exchange Protocol (DLEP) [RFC8175] describes a
protocol for modems to advertise the status of wireless links between
reachable destinations to attached routers. The core specification
of the protocol assumes that every modem in the radio network has an
attached DLEP router, and requires that the MAC address of the DLEP
interface on the attached router is be used to identify the destination
in the network network, for purposes of reporting the state and quality of
the link to that destination.

This document describes a DLEP Extension allowing modems that do not
meet the strict requirement that DLEP must be implemented on a single
Layer 2 domain above to use DLEP to describe link
availability and quality to one or more destinations reachable beyond
a local or remote device on the Layer 2 domain. A

As with core DLEP, a router can use this knowledge to influence any
routing or flow-control decisions regarding traffic to this
destination, understanding that such traffic flows via Layer 3.

1.1. Terminology

Local Layer 2 domain: The Layer 2 domain that links the router and
modem participants of the current DLEP session.

Layer 3 DLEP Destination: A DLEP Destination that is not directly
addressable within the local Layer 2 domain, but is reachable via
a node addressable within the local Layer 2 domain.

Gateway Node: The last device with a MAC address reachable in the
local Layer 2 domain on the path from the DLEP router participant,
towards the Layer 3 destination may DLEP Destination. This device is commonly the
DLEP peer modem but could be an attached another DLEP router, Destination in the case of
a modem Layer
2 domain.

1.2. Applicability

This extension was designed primarily to address the following use
cases:

1. A radio system that does not operate in Layer 2 bridge mode, but
instead provides Layer 3 wide area network connectivity between
devices, or destinations, often
using its own embedded Layer 3 routing function.

2. A point-to-multipoint tunnel system, such as an SD-WAN
deployment, where the tunnel provider acts as a logical destination modem, having
knowledge of the characteristics of the underlay network, and
providing that describes information as availability and metrics between
tunnel endpoints in the overlay network.

3. A modem that provides connectivity to a set remote wide-area network
via a wireless link, but the concept of attached
subnets, when referring a Layer 2 reachable
remote router does not apply. An example of such a modem would
be an LTE device or 802.11 station that provides variable
connectivity to some upstream backbone network
infrastructure.

1.1. the Internet.

This list of use-cases is not exhaustive, and this extension may well
be applicable to future, currently unforeseen, use-cases.

1.3. Requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119.
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

2. Operation

To refer to a Layer 3 DLEP Destination, the DLEP session participant
adds a Link Identifier Data Item (Section 3.2) to the relevant
Destination Message, and (as usual) includes a MAC Address Data Item.
When paired with a Link Identifier Data Item, the MAC Address Data
Item MUST contain the MAC address of the last reachable node in the
Layer 2 domain beyond which the Layer 3 DLEP Destination resides.
For example, if the over-the-air network is not a single Layer 2
domain, the MAC Address Data Item might be the address of the LAN-
side interface of the local modem. Alternatively, when used with
some kind of backbone infrastructure, the MAC Address Data Item would
be the address of the last device reachable on the local Layer 2
domain. However, how such remote destinations are discovered is
beyond the scope of this specification. Gateway Node.

As only modems are initially aware of Layer 3 DLEP Destinations, Link
Identifier Data Items referring to a new link MUST first appear in a
DLEP Destination Up Message from the modem to the router. Once a
link has been identified in this way, Link Identifier Data Items MAY may
be used by either DLEP participant during the lifetime of a DLEP
session. Because of this, a router MUST NOT send a DLEP Destination
Announce Message containing a Link Identifier Data Item referring to
a link that has not been mentioned in a prior DLEP Destination Up
Message. If a modem receives such a message, it MUST terminate the
session by issuing a Session Termination Message containing a Status
Data Item with status code set to 131 'Invalid Destination' and
transition to the Session Termination state.

Because the MAC Address associated with any DLEP Destination Message
containing a Link Identifier Data Item is not the Layer 2 address of
the final destination, all DLEP Destination Up Messages containing a
Link Identifier Data Item MUST contain Layer 3 information. In the
case of modems that provide Layer 3 wide area network connectivity
between devices, this means one or more IPv4 or IPv6 Address Data
Items providing the Layer 3 address of the final destination. When
referring to some upstream backbone network infrastructure, this
means one or more IPv4 or IPv6 Attached Subnet Data Items, for
example: '0.0.0.0/0' or '::/0'. This allows the DLEP peer router to
understand the properties of the link to those routes.

When the DLEP peer router wishes to forward route packets to the Layer 3
destination or subnet, DLEP
Destination, the MAC address associated with the link Gateway Node MUST be
used as the Layer 2 destination of the packet packet, if it wishes to use
the modem network to forward the packet.

As most mainstream routers expect to populate their routing information base with the IP
address of the next hop router towards a destination, implementations
supporting this extension SHOULD announce at least one or more valid IPv4 or
IPv6 addresses of the last
reachable Layer 2 device, i.e. the device with the corresponding MAC
Address.

If the last reachable Layer 2 device is not Gateway Node, this removes the DLEP peer modem, then need for the modem SHOULD announce a DLEP Destination with
router to use an additional IP address resolution protocol before
adding the required MAC
Address without including a Link Identifier Data Item. route to its routing information base.

2.1. Identifier Restrictions

A Link Identifier is by default 4 octets in length. If a modem
wishes to use a Link Identifier of a different length, it MUST be
announced using the Link Identifier Length Data Item (Section 3.1)
contained in the DLEP Session Initialization Response message sent by
the modem to the router.

During the lifetime of a DLEP session, the length of Link Identifiers
MUST remain constant, i.e. the Length field of the Link Identifier
Data Item MUST NOT differ between destinations.

The method for generating Link Identifiers is a modem implementation
matter and out of scope of this document. Routers MUST NOT must not make any
assumptions about the meaning of Link Identifiers, or how Link
Identifiers are generated.

Within a single DLEP session, all Link Identifiers MUST be unique per
MAC Address. This means that a Layer 3 DLEP Destination is uniquely
identified by the pair: {MAC Address,Link Identifier}.

Link Identifiers MUST NOT be reused, i.e. a {MAC Address,Link
Identifier} pair that has been used to refer to one Layer 3 DLEP
Destination MUST NOT be recycled to refer to a different destination
within the lifetime of a single DLEP session.

2.2. Negotiation

To use this extension, as with all DLEP extensions, the extension
MUST be announced during DLEP session initialization. A router
advertises support by including the value 'Link Identifiers' (TBD1),
Section 5, Identifiers', TBD1
(Section 5), in the Extension Data Item within the Session
Initialization Message. A modem advertises support by including the
value 'Link Identifiers' (TBD1) in the Extension Data Item within the
Session Initialization Response Message. If both DLEP peers
advertise support for this extension then the Link Identifier Data
Item MAY Items
can be used. included in DLEP Messages.

If a modem requires support for this extension in order to describe
destinations, and the router does not advertise support, then the
modem MUST NOT include a Link Identifier Data Item in any DLEP
Message. However, the modem SHOULD NOT immediately terminate the
DLEP session, rather it SHOULD use session-wide a combination of DLEP Session
Messages and DLEP Attached Subnet Data Items to
announce provide general information about all reachable destinations via the
modem. By doing this, a modem allows a router not supporting this
extension to at least make a best guess at the state of any reachable
network. A modem MUST NOT attempt to re-use the MAC Address Data
Item to perform some kind of sleight-of-hand, assuming that the
router will notice the DLEP Peer Type of the modem is special in some
way.
information.

3. New Data Items

This extension introduces two new DLEP Data Items: the Link
Identifier Data Item (Section 3.2) used to identify a Layer 3 link at
or beyond a destination, and the Link Identifier Length Data Item
(Section 3.1) used to announce the length of Link Identifiers at
session initialization.

3.1. Link Identifier Length Data Item

The Link Identifier Length Data Item is used by a DLEP modem
implementation to specify the length of Link Identifier Data Items.
It MUST be used during Session Initialization, contained in a Session
Initialization Response Message, if the specified length is not the
default value of 4 octets.

The Link Identifier Length Data Item MAY be used during Session
Initialization, contained in a Session Initialization Response
Message.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Identifier Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Data Item Type: TBD2, Section 5 TBD2 (Section 5)

Length: 2

Link Identifier Length: The length, in octets, of Link Identifiers
used by the DLEP modem for this session.

A Link Identifier Length Data Item that specifies a Link Identifier
Length of 4 octets (the default) is valid, even if it has no effect.

3.2. Link Identifier Data Item

The Link Identifier Data Item MAY be used wherever a MAC Address Data
Item is defined as usable in core DLEP.

Data Item Type: TBD3, Section 5 TBD3 (Section 5)
Length: The length of the Data Item, by default 4, but may be
different if a Link Identifier Length Data Item (Section 3.1) has
been announced during session initialization.

Link Identifier: The unique identifier of the Layer 3 destination. DLEP
Destination. This Link Identifier has no implicit meaning and is
only used to discriminate between multiple links.

4. Security Considerations

As an extension to the core DLEP protocol, the security
considerations of that protocol apply to this extension. This
extension adds no additional security mechanisms or features.

None of the features introduced by this extension require extra
consideration by an implementation.

5. IANA Considerations

Upon approval of this document, IANA is requested to:

o Assign a new DLEP Extensions Registry value (TBD1) from the
Specification Required section, named "Link Identifiers".

o Assign a new DLEP Data Item Type Values Registry value (TBD2) from
the Specification Required section, named "Link Identifier
Length".

o Assign a new DLEP Data Item Type Values Registry value (TBD3) from
the Specification Required section, named "Link Identifier".

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
DOI 10.17487/RFC8175, June 2017,
<https://www.rfc-editor.org/info/rfc8175>.

6.2. Informative References

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.

Authors' Addresses

Rick Taylor
Airbus Defence & Space
Quadrant House
Celtic Springs
Coedkernew
Newport NP10 8FZ
UK

Email: rick.taylor@airbus.com

Stan Ratliff
VT iDirect
13861 Sunrise Valley Drive, Suite 300
Herndon, VA 20171
USA

Email: sratliff@idirect.net