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Network Working Group                                         S. PrevidiRequest for Comments: 5130                                 M. Shand, Ed.Category: Standards Track                                  Cisco Systems                                                               C. Martin                                                          iPath Services                                                           February 2008A Policy Control Mechanism in IS-IS Using Administrative TagsStatus 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.Abstract   This document describes an extension to the IS-IS protocol to add   operational capabilities that allow for ease of management and   control over IP prefix distribution within an IS-IS domain.  This   document enhances the IS-IS protocol by extending the information   that an Intermediate System (IS) router can place in Link State   Protocol (LSP) Data Units for policy use.  This extension will   provide operators with a mechanism to control IP prefix distribution   throughout multi-level IS-IS domains.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . . .23.  Sub-TLV Additions . . . . . . . . . . . . . . . . . . . . . . .23.1.  32-bit Administrative Tag Sub-TLV 1 . . . . . . . . . . . .33.2.  64-bit Administrative Tag Sub-TLV 2 . . . . . . . . . . . .34.  Ordering of Tags  . . . . . . . . . . . . . . . . . . . . . . .35.  Compliance  . . . . . . . . . . . . . . . . . . . . . . . . . .46.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . .47.  Security Considerations . . . . . . . . . . . . . . . . . . . .58.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .59.  Manageability Considerations  . . . . . . . . . . . . . . . . .510. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .611. Contributors  . . . . . . . . . . . . . . . . . . . . . . . . .612. References  . . . . . . . . . . . . . . . . . . . . . . . . . .612.1. Normative References  . . . . . . . . . . . . . . . . . . .612.2. Informative References  . . . . . . . . . . . . . . . . . .6Previdi, et al.             Standards Track                     [Page 1]

RFC 5130                    IS-IS Admin Tags               February 20081.  Introduction   As defined in [RFC1195] and extended in [RFC3784], the IS-IS protocol   [ISO10589] may be used to distribute IPv4 prefix reachability   information throughout an IS-IS domain.  In addition, thanks to   extensions made in [RFC5120] and [ISIS-IPv6], IS-IS may be used to   distribute IPv6 reachability information.   The IPv4 prefix information is encoded as TLV type 128 and 130 in   [RFC1195], with additional information carried in TLV 135 as   specified in [RFC3784] and TLV 235 as defined in [RFC5120].  In   particular, the extended IP Reachability TLV (TLV 135) contains   support for a larger metric space, an up/down bit to indicate   redistribution between different levels in the hierarchy, an IP   prefix, and one or more sub-TLVs that can be used to carry specific   information about the prefix.  TLV 235 is a derivative of TLV 135,   with the addition of Multi-Topology membership information [RFC5120].   The IPv6 prefix information is encoded as TLV 236 in [ISIS-IPv6], and   TLV 237 in [RFC5120].   This document defines 2 new sub-TLVs for TLV 135, TLV 235, TLV 236   and TLV 237 that may be used to carry administrative information   about an IP prefix.2.  Conventions Used in This Document   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 inBCP 14, [RFC2119].3.  Sub-TLV Additions   This document creates 2 new "Administrative Tag" sub-TLVs to be added   to TLV 135, TLV 235, TLV 236 and TLV 237.  These TLVs specify one or   more 32- or 64-bit unsigned integers that may be associated with an   IP prefix.  Example uses of these tags include carrying BGP standard   (or extended) communities and controlling redistribution between   levels and areas, different routing protocols, or multiple instances   of IS-IS running on the same router.   The methods for which their use is employed is beyond the scope of   this document and left to the implementer and/or operator.   The encoding of the sub-TLV(s) is discussed in the following   subsections.Previdi, et al.             Standards Track                     [Page 2]

RFC 5130                    IS-IS Admin Tags               February 20083.1.  32-bit Administrative Tag Sub-TLV 1   The Administrative Tag SHALL be encoded as one or more 4-octet   unsigned integers using Sub-TLV 1 in TLV 135 [RFC3784], TLV 235   [RFC5120], TLV 236 [ISIS-IPv6], and TLV 237 [RFC5120].  The   Administrative Tag Sub-TLV has following structure:   o  1 octet of type (value: 1)   o  1 octet of length (value: multiple of 4)   o  one or more instances of 4 octets of administrative tag   On receipt, an implementation MAY consider only one encoded tag, in   which case, the first encoded tag MUST be considered and any   additional tags ignored.  A tag value of zero is reserved and SHOULD   be treated as "no tag".3.2.  64-bit Administrative Tag Sub-TLV 2   The Administrative Tag SHALL be encoded as one or more 8-octet   unsigned integers using Sub-TLV 2 in TLV 135 [RFC3784], TLV 235   [RFC5120], TLV 236 [ISIS-IPv6], and TLV 237 [RFC5120].  The 64-bit   Administrative Tag Sub-TLV has following structure:   o  1 octet of type (value: 2)   o  1 octet of length (value: multiple of 8)   o  one or more instances of 8 octets of administrative tag   On receipt, an implementation MAY consider only one encoded tag; in   which case, the first encoded tag MUST be considered and any   additional tags ignored.  A tag value of zero is reserved and SHOULD   be treated as "no tag".4.  Ordering of Tags   The semantics of the tag order are implementation-dependent.  That   is, there is no implied meaning to the ordering of the tags that   indicates a certain operation or set of operations need be performed   based on the order of the tags.  Each tag SHOULD be treated as an   autonomous identifier that MAY be used in policy to perform a policy   action.  Whether or not tag A precedes or succeeds tag B SHOULD not   change the meaning of the tag set.  However, when propagating TLVs   that contain multiple tags between levels, an implementation SHOULDPrevidi, et al.             Standards Track                     [Page 3]

RFC 5130                    IS-IS Admin Tags               February 2008   preserve the ordering such that the first tag remains the first tag,   so that implementations that only recognize a single tag will have a   consistent view across levels.   Each IS that receives an LSP with TLV(s) 135 and/or 235 and/or 236   and/or 237, that have associated sub-TLV(s) 1 and/or 2, MAY operate   on the tag values as warranted by the implementation.  If an   implementation needs to change tag values, for example, when   propagating TLVs between levels at an area boundary, then the TLV(s)   SHOULD be copied to the newly generated Level-1 or Level-2 LSP.  At   that point, the contents of the sub-TLV(s) MAY change as dictated by   the policy action.  In the event that no change is required, the sub-   TLV(s) SHOULD be copied in order into the new LSP, such that ordering   is preserved.5.  Compliance   A compliant IS-IS implementation MUST be able to assign one tag to   any IP prefix in any of the following TLVs: TLV 135, TLV 235, TLV   236, TLV 237.  It MUST be able to interpret a single tag present in   the sub-TLV, or the first tag where there is more than one tag   present in the sub-TLV.   A compliant IS-IS implementation MAY be able to assign more than one   tag to any IP prefix in any of the following TLVs: TLV 135, TLV 235,   TLV 236, TLV 237.  It MAY be able to interpret the second and   subsequent tags where more than one tag is present in the sub-TLV.   When propagating TLVs between levels, a compliant IS-IS   implementation MAY be able to rewrite or remove one or more tags   associated with a prefix in any of the following TLVs: TLV 135, TLV   235, TLV 236, TLV 237.6.  Operations   An administrator associates an Administrative Tag value with some   interesting property.  When IS-IS advertises reachability for some IP   prefix that has that property, it adds the Administrative Tag to the   IP reachability information TLV for that prefix, and the tag "sticks"   to the prefix as it is flooded throughout the routing domain.   Consider the network in Figure 1.  We wish to "leak" L1 prefixes   [RFC2966] with some property, A, from L2 to the L1 router R1.   Without policy groups, there is no way for R2 to know property A   prefixes from property B prefixes.Previdi, et al.             Standards Track                     [Page 4]

RFC 5130                    IS-IS Admin Tags               February 2008                        R2--------R3--------R4                 L2     /                    \                 - - - /- - - - - - - - - - - - - -                 L1   /                        \                    R1----1.1.1.0/24 (A)       R5                                                |                                                |                                          1.1.2.0/24 (B)                        Figure 1: Example of usage   We associate Administrative Tag 100 with property A, and have R5   attach that value to the IP extended reachability information TLV for   prefix 1.1.2.0/24.  R2 has a policy in place to "match prefixes with   Administrative Tag 100, and leak to L1".   The previous example is rather simplistic; it seems that it would be   just as easy for R2 simply to match the prefix 1.1.2.0/24.  However,   if there are a large number of routers that need to apply some policy   according to property A and a large number of "A" prefixes, this   mechanism can be quite helpful.   Implementations that support only a single tag and those that support   multiple tags may coexist in the same IS-IS domain.  An   implementation supporting multiple tags SHOULD therefore assign any   tag that is required to be interpreted by all systems as the first   tag in any set of multiple tags.7.  Security Considerations   This document raises no new security issues for IS-IS, as any   annotations to IP prefixes should not pass outside the administrative   control of the network operator of the IS-IS domain.  Such an   allowance would violate the spirit of Interior Gateway Protocols in   general and IS-IS in particular.8.  IANA Considerations   IANA has assigned "1" as the type code of the 32-bit Administrative   Tag Sub-TLV and "2" as the type code of the 64-bit Administrative Tag   Sub-TLV.9.  Manageability Considerations   These extensions have been designed, developed, and deployed for many   years and do not have any new impact on management and operation of   the IS-IS protocol via this standardization process.Previdi, et al.             Standards Track                     [Page 5]

RFC 5130                    IS-IS Admin Tags               February 200810.  Acknowledgements   The authors would like to thank Henk Smit for clarifying the best   place to describe this new information, Tony Li and Tony Przygienda   for useful comments on this document, and Danny McPherson for some   much needed formatting assistance.11.  Contributors   Brad Neal contributed portions of this document.12.  References12.1.  Normative References   [ISO10589]   International Organization for Standardization,                "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)", ISO/                IEC 10589:2002, Second Edition, Nov 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 1997.12.2.  Informative References   [ISIS-IPv6]  Hopps, C.,"Routing IPv6 with IS-IS", Work in Progress,                October 2007.   [RFC2966]    Li, T., Przygienda, T., and H. Smit, "Domain-wide Prefix                Distribution with Two-Level IS-IS",RFC 2966,                October 2000.   [RFC3784]    Smit, H. and T. Li, "Intermediate System to Intermediate                System (IS-IS) Extensions for Traffic Engineering (TE)",RFC 3784, June 2004.   [RFC5120]    Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi                Topology (MT) Routing in IS-IS",RFC 5120,                February 2008.Previdi, et al.             Standards Track                     [Page 6]

RFC 5130                    IS-IS Admin Tags               February 2008Authors' Addresses   Stefano Previdi   Cisco Systems   Via Del Serafico, 200   00142 Rome,   Italy   EMail: sprevidi@cisco.com   Mike Shand (editor)   Cisco Systems   250, Longwater Avenue.   Reading, Berks  RG2 6GB   UK   Phone: +44 208 824 8690   EMail: mshand@cisco.com   Christian Martin   iPath Services   EMail: chris@ipath.netPrevidi, et al.             Standards Track                     [Page 7]

RFC 5130                    IS-IS Admin Tags               February 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Previdi, et al.             Standards Track                     [Page 8]