Mobile Ad hoc Networks Working Group R. Taylor
Internet-Draft Airbus Defence & Space
Intended status: Standards Track May 30, 2017
Expires: December 1, 2017
Link Identifier Extension to DLEP
draft-dlep-lid-00
Abstract
There exists a class of modems that wish to support the Dynamic Link
Exchange Protocol (DLEP) [I-D.ietf-manet-dlep] but do not present a
single Layer 2 network domain as required by DLEP. Such devices may
be:
o Modems that maintain a varying link to some upstream backbone
network infrastructure, where the ability to announce link state
and DLEP metrics is desired, but the concept of a DLEP destination
router for the backbone does not apply. Examples of such devices
can include LTE modems, IEEE 802.11 stations not in ad-hoc mode,
and some satellite terminals.
o Modems that provide Layer 3 wide area network connectivity between
devices, where individual DLEP destinations do exist, but are not
directly reachable by MAC address.
This document introduces an optional extension to the core DLEP
specification, allowing DLEP to be used between routers and modems
that operate in this way.
Note:
o This document is intended as an extension to the core DLEP
specification, and readers are expected to be fully conversant
with the operation of core DLEP.
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3
2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 4
2.2. Link Identifier Data Item . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4.1. DLEP Link Identifier Flag . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The Dynamic Link Exchange Protocol (DLEP) [I-D.ietf-manet-dlep]
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 the MAC address of the DLEP
interface on the router is used to identify the destination in the
network for purposes of reporting the state and quality of the link
to that destination.
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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 to use DLEP to describe link state and quality to one
or more destinations reachable only at Layer 3.
To enable routers to take advantage of the DLEP protocol this
extension adds a single enhancement to the DLEP protocol: A new Link
Identifier Data Item. This Data Item replaces the use of the MAC
Address Data Item whenever the DLEP destination does not have a
router reachable by MAC address.
By using the Link Identifier Data Item, the modem implementation can
announce the link state and quality to a uniquely identified
destination in the network, either logical or physical, explicitly
indicating that the destination is not reachable via a single Layer 2
domain. A router can use this knowledge to influence any routing or
flow-control decisions regarding traffic to this destination,
understanding that such decisions apply at Layer 3.
1.1. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
2. Operation
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 Identitifers' (TBD1)
in the Extension Data Item within the Session Intitialization
Message. A modem advertises support by including the value 'Link
Identitifers' (TBD1) in the Extension Data Item within the Session
Intitialization Response Message. If both DLEP peers advertise
support for this extension then the Link Identifier Data Item MAY be
used.
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 DLEP Data Items to
announce 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
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router will notice the DLEP Peer Type of the modem is special in some
way.
Even when the Link Identifiers extension is in use for a DLEP
session, either peer MAY send and receive Messages concerning DLEP
destinations that are reachable via a single Layer 2 domain, using
the standard DLEP MAC Address Data Item. This allows modems that
support hybrid functionality of directly connected Layer 2 peers, as
well as upstream links to some kind of infrastructure, as well as
multicast logical destinations.
2.1. Identifier Restrictions
Within a single DLEP session, all identifiers used by this extension,
both logical and physical, MUST be unique, and it is RECOMMENDED that
they be 4 octets in length.
Identifiers MUST NOT be reused, i.e. an indentifier that has been
used to refer to one destination MUST NOT be recycled to refer to a
different destination within the lifetime of a single DLEP session.
The method for generating identifiers is a modem implementation
matter and out of scope of this document. Routers MUST NOT make any
assumptions about the meaning of identifiers, or how identifiers are
generated.
2.2. Link Identifier Data Item
The Link Identifier Data Item MAY be used whenever a MAC Address Data
Item is defined as useable in core DLEP. A single Link Identifier
Data Item MUST only be used in place of a single MAC Address Data
Item. A Link Identifier Data Item MUST NOT appear in the same DLEP
Message as a MAC Address Data Item.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Link Identifier... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD2
Length: >0, 4 RECOMMENDED.
Flags: Flags field, defined below.
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Link Identifier: The unique identifier of the link destination.
This identifier has no implicit meaning and is only used to
discriminate between multiple links.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+
Reserved: MUST be zero. Left for future assignment.
The Flags field is here because I think it might be useful, but I
can't think how currently.
3. 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.
4. IANA Considerations
Upon approval of this document, IANA is requested to:
o Assign a new value (TBD1) from the Specification Required section
of the DLEP Extensions Registry, named "Link Identifiers".
o Assign a new value (TBD2) from the Specification Required section
of the DLEP Data Item Type Values Registry, named "Link
Identifier".
4.1. DLEP Link Identifier Flag
Upon approval of this document, IANA is requested to create a new
DLEP registry, named "Link Identifier Flags".
The following table provides initial registry values and the
[RFC5226] defined policies that should apply to the registry:
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+------------+------------------------------------+
| Bit | Description/Policy |
+------------+------------------------------------+
| 0-7 | Unassigned/Specification Required |
+------------+------------------------------------+
5. References
5.1. Normative References
[I-D.ietf-manet-dlep]
Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", draft-
ietf-manet-dlep-29 (work in progress), March 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
5.2. Informative References
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
Author's Address
Rick Taylor
Airbus Defence & Space
Quadrant House
Celtic Springs
Coedkernew
Newport NP10 8FZ
UK
Email: rick.taylor@airbus.com
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