Extensions to IS-IS for Layer-2 Systems
RFC 6165

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/rfc6165.

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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
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   publication of this document.  Please review these documents
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   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] [RFC1195], 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

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   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 [RFC2119].

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 [RFC5305].  They are defined in the technology-
      specific documents.

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   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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   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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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.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5305]  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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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

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