Bit Index Explicit Replication (BIER) Support via IS-IS
RFC 8401

Internet Engineering Task Force (IETF)                  L. Ginsberg, Ed.
Request for Comments: 8401                                 Cisco Systems
Category: Standards Track                                  A. Przygienda
ISSN: 2070-1721                                         Juniper Networks
                                                               S. Aldrin
                                                                  Google
                                                                J. Zhang
                                                  Juniper Networks, Inc.
                                                               June 2018

        Bit Index Explicit Replication (BIER) Support via IS-IS

Abstract

   This document defines IS-IS extensions to support multicast
   forwarding using the Bit Index Explicit Replication (BIER)
   architecture.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8401.

Copyright Notice

   Copyright (c) 2018 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
   (https://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.

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RFC 8401                 BIER Support via IS-IS                June 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Concepts  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  BIER Domains and Subdomains . . . . . . . . . . . . . . .   5
     4.2.  Advertising BIER Information  . . . . . . . . . . . . . .   5
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Multi-Topology and Subdomain  . . . . . . . . . . . . . .   5
     5.2.  BFR-id Advertisements . . . . . . . . . . . . . . . . . .   6
     5.3.  Logging Misconfiguration  . . . . . . . . . . . . . . . .   6
     5.4.  Flooding Reduction  . . . . . . . . . . . . . . . . . . .   6
   6.  Packet Formats  . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  BIER Info Sub-TLV . . . . . . . . . . . . . . . . . . . .   7
     6.2.  BIER MPLS Encapsulation Sub-sub-TLV . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Bit Index Explicit Replication (BIER) [RFC8279] defines an
   architecture where all intended multicast receivers are encoded as a
   bitmask in the multicast packet header within different
   encapsulations such as described in [RFC8296].  A router that
   receives such a packet will forward the packet based on the bit
   position in the packet header towards the receiver(s) following a
   precomputed tree for each of the bits in the packet.  Each receiver
   is represented by a unique bit in the bitmask.

   This document presents necessary extensions to the currently deployed
   IS-IS for IP [RFC1195] to support distribution of information
   necessary for operation of BIER domains and subdomains.  This
   document defines a new TLV to be advertised by every router
   participating in BIER signaling.

   This document defines support for MPLS encapsulation as specified in
   [RFC8296].  Support for other encapsulation types and the use of
   multiple encapsulation types are outside the scope of this document.

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2.  Terminology

   Some of the terminology specified in [RFC8279] is replicated here and
   extended by necessary definitions:

   BIER:  Bit Index Explicit Replication.  The overall architecture of
      forwarding multicast using a bit position.

   BIER-OL:  BIER Overlay Signaling.  The method for the BFIR to learn
      about BFERs.

   BFR:  Bit Forwarding Router.  A router that participates in Bit Index
      Multipoint Forwarding.  A BFR is identified by a unique BFR-prefix
      in a BIER domain.

   BFIR:  Bit Forwarding Ingress Router.  The ingress border router that
      inserts the BitString into the packet.  Each BFIR must have a
      valid BFR-id assigned.

   BFER:  Bit Forwarding Egress Router.  A router that participates in
      Bit Index Forwarding as a leaf.  Each BFER must be a BFR.  Each
      BFER must have a valid BFR-id assigned.

   BFT:  Bit Forwarding Tree used to reach all BFERs in a domain.

   BIER subdomain:  A further distinction within a BIER domain
      identified by its unique subdomain identifier.  A BIER subdomain
      can support multiple BitString Lengths.

   BFR-id:  An optional, unique identifier for a BFR within a BIER
      subdomain.

   Invalid BFR-id:  Unassigned BFR-id.  The special value 0 is reserved
      for this purpose.

   BAR:  BIER Algorithm.  Used to calculate underlay next hops.

   IPA:  IGP Algorithm.  May be used to modify, enhance, or replace the
      calculation of underlay paths as defined by the BAR value.

   SPF:  Shortest Path First routing calculation based on the IGP link
      metric.

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RFC 8401                 BIER Support via IS-IS                June 2018

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  IANA Considerations

   This document adds the following entry to the "Sub-TLVs for TLVs 135,
   235, 236, and 237" registry.

   Value: 32

   Name: BIER Info

   This document also introduces a new registry for sub-sub-TLVs for the
   BIER Info sub-TLV.  The registration policy is Expert Review as
   defined in [RFC8126].  The "Sub-sub-TLVs for BIER Info Sub-TLV" has
   been created within the "IS-IS TLV Codepoints" registry.  The defined
   value is as follows:

     Type    Name
     ----    ----
     1       BIER MPLS Encapsulation

   IANA has created the "BIER Algorithms" registry within the "Bit Index
   Explicit Replication (BIER)" registry.  The registration policies
   [RFC8126] for this registry are:

      "Standards Action" for values 0-127

      "Specification Required" for values 128-239

      "Experimental Use" for values 240-254

   The initial values in the "BIER Algorithms" registry are:

      0: No BIER-specific algorithm is used

      255: Reserved

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RFC 8401                 BIER Support via IS-IS                June 2018