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Internet Engineering Task Force (IETF)                             T. LiRequest for Comments: 6233                                   L. GinsbergUpdates:3563,5304,5310                            Cisco Systems, Inc.Category: Standards Track                                       May 2011ISSN: 2070-1721IS-IS Registry Extension for PurgesAbstract   IANA maintains the "IS-IS TLV Codepoints" registry.  This registry   documents which TLVs can appear in different types of IS-IS Protocol   Data Units (PDUs), but does not document which TLVs can be found in   zero Remaining Lifetime Link State PDUs (LSPs), a.k.a. purges.  This   document extends the existing registry to record the set of TLVs that   are permissible in purges and updates the rules for generating and   processing purges in the presence of authentication.  This document   updatesRFC 3563,RFC 5304, andRFC 5310.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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6233.Copyright Notice   Copyright (c) 2011 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Li & Ginsberg                Standards Track                    [Page 1]

RFC 6233              Registry Extension for Purges             May 2011Table of Contents1. Introduction ....................................................21.1. Requirements Language ......................................22. Registry Changes ................................................23. Purges and Authentication .......................................34. IANA Considerations .............................................35. Security Considerations .........................................36. Normative References ............................................41.  Introduction   The IS-IS [ISO-10589] routing protocol maintains a link state   database of the topology of its routing domain by flooding a set of   Link State Protocol Data Units (LSPs).  When the protocol no longer   needs the information stored in an LSP, it uses the purge mechanism   to cause the Intermediate Systems (ISs) in its domain to discard the   information contained in the LSP.  The process for generating purges   can be found in Section 7.3.16.4 of [ISO-10589].  This process   retains only the LSP header, discarding any TLVs that had been   carried within the LSP.   Subsequent enhancements to IS-IS, such as [RFC5304] [RFC5310], amend   the process of generating a purge and allow the inclusion of certain   TLVs in purges.1.1.  Requirements Language   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 [RFC2119].2.  Registry Changes   This document extends the current "IS-IS TLV Codepoints" registry,   defined in [RFC3563], to record the set of TLVs that MAY be found in   purges.  All other TLVs MUST NOT appear in purges.  This will serve   as an aid to subsequent documents, which can then refer to the   registry as the definitive list of the TLVs allowed in purges.  This   will also act as an aid to implementers, providing them with an   easily accessible compendium of allowable TLVs.   The purge status defined for a given TLV applies to all sub-TLVs   defined for that TLV.Li & Ginsberg                Standards Track                    [Page 2]

RFC 6233              Registry Extension for Purges             May 20113.  Purges and Authentication   Previous documents on authentication [RFC5304] [RFC5310] required   that an IS only accept a purge if it only contained the   Authentication TLV.   This document updates and generalizes that behavior as follows: an   implementation that implements authentication MUST NOT accept a purge   that contains any TLV listed in the registry that is not acceptable   in a purge.  An implementation MUST NOT accept a purge that contains   a TLV not listed in the registry unless the purge also contains the   Purge Originator Identification (POI) TLV [RFC6232].  Purges that are   accepted MUST be propagated without removal of TLVs.  If multiple   purges are received for the same LSP, then the implementation MAY   propagate any one of the purges.   If an implementation that implements authentication accepts a purge   that does not include the POI TLV and it chooses to insert the POI   TLV, it MUST also recompute authentication.   ISs MUST NOT accept LSPs with a non-zero Remaining Lifetime that   contain the POI TLV.   Purge generation is updated as follows: an implementation that   implements authentication generates a purge by first removing any   TLVs that are not listed in the registry as being acceptable in   purges.  The POI TLV MUST be added.  Then any other TLVs that MAY be   in purges, as shown by the registry, MAY be added.  Finally,   authentication, if any, is added.4.  IANA Considerations   IANA has modified the "IS-IS TLV Codepoints" registry by adding a   column in the registry for 'Purge'.  A 'y' in this column indicates   that the TLV for this row MAY be found in a purge.  An 'n' in this   column indicates that the TLV for this row MUST NOT be found in a   purge.   The 'Purge' column should initially contain a 'y' for TLV type 10   (Authentication) and for TLV type 137 (Dynamic hostname).  All other   entries in this column should have an 'n'.  Other additions to this   registry should explicitly specify their value for this column.5.  Security Considerations   This document introduces no new security issues.Li & Ginsberg                Standards Track                    [Page 3]

RFC 6233              Registry Extension for Purges             May 20116.  Normative References   [ISO-10589]  ISO, "Intermediate system to Intermediate system                intra-domain routeing information exchange protocol for                use in conjunction with the protocol for providing the                connectionless-mode Network Service (ISO 8473)",                ISO/IEC 10589:2002.   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate                Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC3563]    Zinin, A., "Cooperative Agreement Between the ISOC/IETF                and ISO/IEC Joint Technical Committee 1/Sub Committee 6                (JTC1/SC6) on IS-IS Routing Protocol Development",RFC 3563, July 2003.   [RFC5304]    Li, T. and R. Atkinson, "IS-IS Cryptographic                Authentication",RFC 5304, October 2008.   [RFC5310]    Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,                and M. Fanto, "IS-IS Generic Cryptographic                Authentication",RFC 5310, February 2009.   [RFC6232]    Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge                Originator Identification TLV for IS-IS",RFC 6232,                May 2011.Authors' Addresses   Tony Li   Cisco Systems, Inc.   170 W. Tasman Dr.   San Jose, CA  95134   USA   EMail: tony.li@tony.li   Les Ginsberg   Cisco Systems, Inc.   170 W. Tasman Dr.   San Jose, CA  95134   USA   EMail: ginsberg@cisco.comLi & Ginsberg                Standards Track                    [Page 4]