Simplified Extension of Link State PDU (LSP) Space for IS-IS
RFC 5311

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Network Working Group                                  D. McPherson, Ed.
Request for Comments: 5311                                Arbor Networks
Obsoletes: 3786                                              L. Ginsberg
                                                              S. Previdi
                                                                M. Shand
                                                           Cisco Systems
                                                           February 2009

      Simplified Extension of Link State PDU (LSP) Space for IS-IS

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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.

Abstract

   This document describes a simplified method for extending the Link
   State PDU (LSP) space beyond the 256 LSP limit.  This method is
   intended as a preferred replacement for the method defined in RFC
   3786.

McPherson, et al.           Standards Track                     [Page 1]
RFC 5311      Simplified Extension of LSP Space for IS-IS  February 2009

Table of Contents

   1. Overview ........................................................2
   2. Specification of Requirements ...................................3
   3. Definition of Commonly Used Terms ...............................3
   4. Utilizing Additional System IDs .................................4
      4.1. Additional Information in Extended LSPs ....................4
      4.2. Extended LSP Restrictions ..................................4
           4.2.1. TLVs That MUST NOT Appear ...........................4
           4.2.2. Leaf Advertisements in Extended LSPs ................5
           4.2.3. IS Neighbor Advertisement Restrictions ..............5
           4.2.4. Area Addresses ......................................6
           4.2.5. Overload, Attached, Partition Repair Bits ...........6
      4.3. Originating LSP Requirements ...............................6
      4.4. IS Alias ID TLV (IS Alias ID) ..............................7
      4.5. New TLVs in Support of IS Neighbor Attributes ..............7
   5. Comparison with the RFC 3786 Solution ...........................8
   6. Deployment Considerations .......................................8
      6.1. Advertising New TLVs in Extended LSPs ......................9
      6.2. Reachability and Non-SPF TLV Staleness .....................9
      6.3. Normal LSP OL State and Use of Extended LSPs ...............9
      6.4. Moving Neighbor Attribute INFO LSPs ........................9
      6.5. Advertising Leaf INFO Extended LSPs .......................10
   7. Security Considerations ........................................10
   8. IANA Considerations ............................................10
   9. References .....................................................11
      9.1. Normative References ......................................11
      9.2. Informative References ....................................11

1.  Overview

   [IS-IS] defines the set of LSPs that may be originated by a system at
   each level.  This set is limited to 256 LSPs.  [IS-IS] also defines a
   maximum value for an LSP (originatingLxLSPBufferSize) as 1492 bytes.
   The carrying capacity of an LSP set, while bounded, has thus far been
   sufficient for advertisements associated with an area/domain in
   existing deployment scenarios.  However, the definition of additional
   information to be included in LSPs (e.g., multi-topology support,
   traffic engineering information, router capabilities, etc.) has the
   potential to exceed the carrying capacity of an LSP set.

   This issue first drew interest when traffic engineering extensions
   were introduced.  This interest resulted in the solution defined in
   [RFC3786].  However, that solution suffers from restrictions required
   to maintain interoperability with systems that do not support the
   extensions.

McPherson, et al.           Standards Track                     [Page 2]
RFC 5311      Simplified Extension of LSP Space for IS-IS  February 2009

   This document defines extensions that allow a system to exceed the
   256 LSP limit and do so in a way that has no interoperability issues
   with systems that do not support the extension.  It is seen as a