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IETF RFC 6165
Extensions to IS-IS for Layer-2 Systems
Last modified on Thursday, April 14th, 2011
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Internet Engineering Task Force (IETF) A. Banerjee
Request for Comments: 6165 Cisco Systems
Category: Standards Track D. Ward
ISSN: 2070-1721 Juniper Networks
April 2011
Extensions to IS-IS for Layer-2 Systems
 Abstract
This document specifies the Intermediate System to Intermediate
System (IS-IS) extensions necessary to support link state routing for
any protocols running directly over Layer-2. While supporting this
concept involves several pieces, this document only describes
extensions to IS-IS. Furthermore, the Type, Length, Value pairs
(TLVs) described in this document are generic Layer-2 additions, and
specific ones as needed are defined in the IS-IS technology-specific
extensions. We leave it to the systems using these IS-IS extensions
to explain how the information carried in IS-IS is used.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6165.
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RFC 6165 Layer-2-IS-IS April 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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. Overview ........................................................2
1.1. Terminology ................................................3
2. TLV Enhancements to IS-IS .......................................3
2.1. Multi-Topology-Aware Port Capability TLV ...................3
2.2. The MAC-Reachability TLV ...................................4
3. Acknowledgements ................................................5
4. Security Considerations .........................................5
5. IANA Considerations .............................................5
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................6
1. Overview
There are a number of systems (for example, [RBRIDGES], [802.1aq],
and [OTV]) that use Layer-2 addresses carried in a link state routing
protocol, specifically Intermediate System to Intermediate System
[IS-IS] [RFC 1195], to provide true Layer-2 routing. In almost all
the technologies mentioned above, classical Layer-2 packets are
encapsulated with an outer header. The outer header format varies
across all these technologies. This outer header is used to route
the encapsulated packets to their destination.
Each Intermediate System (IS) advertises one or more IS-IS Link State
Protocol Data Units (PDUs) with routing information. Each Link State
PDU (LSP) is composed of a fixed header and a number of tuples, each
consisting of a Type, a Length, and a Value. Such tuples are
Banerjee & Ward Standards Track PAGE 2
RFC 6165 Layer-2-IS-IS April 2011
commonly known as TLVs. In this document, we specify a set of TLVs
to be added to [IS-IS] PDUs, to support these proposed systems. The
TLVs are generic Layer-2 additions, and specific ones, as needed, are
defined in the IS-IS technology-specific extensions. This document
does not propose any new forwarding mechanisms using this additional
information carried within IS-IS.
1.1. Terminology
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 RFC 2119 [RFC 2119].
2. TLV Enhancements to IS-IS
This section specifies the enhancements for the TLVs that are needed
in common by Layer-2 technologies.
2.1. Multi-Topology-Aware Port Capability TLV
The Multi-Topology-aware Port Capability (MT-PORT-CAP) is IS-IS TLV
type 143 and has the following format:
+-+-+-+-+-+-+-+-+
| Type=MTPORTCAP| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|R|R|R| Topology Identifier | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs (variable bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: TLV Type, set to MT-PORT-CAP TLV 143.
o Length: Total number of bytes contained in the value field,
including the length of the sub-TLVs carried in this TLV.
o R: Reserved 4 bits, MUST be sent as zero and ignored on receipt.
o Topology Identifier: MT ID is a 12-bit field containing the MT ID
of the topology being announced. This field when set to zero
implies that it is being used to carry base topology information.
o Sub-TLVs: The MT-PORT-CAP TLV value contains sub-TLVs formatted as
described in [RFC 5305]. They are defined in the technology-
specific documents.
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RFC 6165 Layer-2-IS-IS April 2011
The MT-PORT-CAP TLV may occur multiple times and is carried within an
IS-IS Hello (IIH) PDU.
2.2. The MAC-Reachability TLV
The MAC-Reachability (MAC-RI) TLV is IS-IS TLV type 147 and has the
following format:
+-+-+-+-+-+-+-+-+
| Type= MAC-RI | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Topology-id/Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Confidence | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | VLAN-ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC (1) (6 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC (N) (6 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: TLV Type, set to 147 (MAC-RI).
o Length: Total number of bytes contained in the value field given
by 5 + 6*n bytes.
o Topology-id/Nickname : Depending on the technology in which it is
used, this carries the topology-id or nickname. When this field
is set to zero, this implies that the Media Access Control (MAC)
addresses are reachable across all topologies or across all
nicknames of the originating IS.
o Confidence: This carries an 8-bit quantity indicating the
confidence level in the MAC addresses being transported. Whether
this field is used, and its semantics if used, are further defined
by the specific protocol using Layer-2 IS-IS. If not used, it
MUST be set to zero on transmission and be ignored on receipt.
o RESV: (4 bits) MUST be sent as zero and ignored on receipt.
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RFC 6165 Layer-2-IS-IS April 2011
o VLAN-ID: This carries a 12-bit VLAN identifier that is valid for
all subsequent MAC addresses in this TLV, or the value zero if no
VLAN is specified.
o MAC(i): This is the 48-bit MAC address reachable from the IS that
is announcing this TLV.
The MAC-RI TLV is carried in a standard Link State PDU (LSP). This
TLV can be carried multiple times in an LSP and in multiple LSPs. It
MUST contain only unicast addresses. The manner in which these TLVs
are generated by the various Layer-2 routing technologies and the
manner in which they are consumed are detailed in the technology-
specific documents.
In most of the technologies, these MAC-RI TLVs will translate to
populating the hardware with these entries and with appropriate next-
hop information as derived from the advertising IS.
3. Acknowledgements
The authors would like to thank Peter Ashwood-Smith, Donald E.
Eastlake 3rd, Dino Farinacci, Don Fedyk, Les Ginsberg, Radia Perlman,
Mike Shand, and Russ White for their useful comments.
4. Security Considerations
This document adds no additional security risks to IS-IS, nor does it
provide any additional security for IS-IS.
5. IANA Considerations
This document specifies the definition of a set of new IS-IS TLVs --
the Port-Capability TLV (type 143) and the MAC-Reachability TLV
(type 147). They are listed in the IS-IS TLV codepoint registry.
IIH LSP SNP
MT-Port-Cap-TLV (143) X - -
MAC-RI TLV (147) - X -
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RFC 6165 Layer-2-IS-IS April 2011
6. References
6.1. Normative References
[IS-IS] ISO/IEC 10589:2002, Second Edition, "Intermediate System
to Intermediate System Intra-Domain Routing Information
Exchange Protocol for use in Conjunction with the Protocol
for Providing the Connectionless-mode Network Service
(ISO 8473)", 2002.
[RFC 1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
6.2. Informative References
[802.1aq] "Standard for Local and Metropolitan Area Networks /
Virtual Bridged Local Area Networks / Amendment 8:
Shortest Path Bridging, Draft IEEE P802.1aq/D1.5", 2008.
[OTV] Grover, H., Rao, D., and D. Farinacci, "Overlay Transport
Virtualization", Work in Progress, October 2010.
[RBRIDGES]
Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "RBridges: Base Protocol Specification", Work
in Progress, March 2010.
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RFC 6165 Layer-2-IS-IS April 2011
Authors' Addresses
Ayan Banerjee
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95138
USA
EMail: ayabaner@cisco.com
David Ward
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089-1206
USA
Phone: +1-408-745-2000
EMail: dward@juniper.net
Banerjee & Ward Standards Track PAGE 7
Extensions to IS-IS for Layer-2 Systems
RFC TOTAL SIZE: 12266 bytes
PUBLICATION DATE: Thursday, April 14th, 2011
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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