A Policy Control Mechanism in IS-IS Using Administrative Tags
RFC 5130

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Network Working Group                                         S. Previdi
Request for Comments: 5130                                 M. Shand, Ed.
Category: Standards Track                                  Cisco Systems
                                                               C. Martin
                                                          iPath Services
                                                           February 2008

     A Policy Control Mechanism in IS-IS Using Administrative Tags

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.

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 Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
   3.  Sub-TLV Additions . . . . . . . . . . . . . . . . . . . . . . . 2
     3.1.  32-bit Administrative Tag Sub-TLV 1 . . . . . . . . . . . . 3
     3.2.  64-bit Administrative Tag Sub-TLV 2 . . . . . . . . . . . . 3
   4.  Ordering of Tags  . . . . . . . . . . . . . . . . . . . . . . . 3
   5.  Compliance  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   9.  Manageability Considerations  . . . . . . . . . . . . . . . . . 5
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     12.1. Normative References  . . . . . . . . . . . . . . . . . . . 6
     12.2. Informative References  . . . . . . . . . . . . . . . . . . 6

Previdi, et al.             Standards Track                     [Page 1]
RFC 5130                    IS-IS Admin Tags               February 2008

1.  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 in BCP 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]