Skip to main content

BIER support via ISIS
draft-przygienda-bier-isis-ranges-00

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Author Tony Przygienda
Last updated 2014-09-29
Replaced by draft-ietf-bier-isis-extensions, draft-ietf-bier-isis-extensions, RFC 8401
RFC stream (None)
Formats
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date (None)
Responsible AD (None)
Send notices to (None)
draft-przygienda-bier-isis-ranges-00
Internet Engineering Task Force                            A. Przygienda
Internet-Draft                                                  Ericsson
Intended status: Standards Track                      September 27, 2014
Expires: March 31, 2015

                         BIER support via ISIS
                  draft-przygienda-bier-isis-ranges-00

Abstract

   Specification of an ISIS extension to support BIER domains.

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 RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 31, 2015.

Copyright Notice

   Copyright (c) 2014 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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

Przygienda               Expires March 31, 2015                 [Page 1]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Concepts  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  BIER as Capability  . . . . . . . . . . . . . . . . . . .   4
     4.2.  BIER Domain Identifier  . . . . . . . . . . . . . . . . .   4
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Enabling a BIER Domain  . . . . . . . . . . . . . . . . .   4
     5.2.  Length of Bitmasks  . . . . . . . . . . . . . . . . . . .   4
       5.2.1.  Special Consideration . . . . . . . . . . . . . . . .   5
     5.3.  Encapsulation . . . . . . . . . . . . . . . . . . . . . .   5
     5.4.  Label Advertisements  . . . . . . . . . . . . . . . . . .   5
       5.4.1.  Special Consideration . . . . . . . . . . . . . . . .   5
     5.5.  BFR-id Advertisements . . . . . . . . . . . . . . . . . .   5
   6.  Packet Formats  . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  BIER BFR sub-TLV  . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Bit Index Explicit Replication (BIER)
   [I-D.draft-wijnands-bier-architecture-00] defines an architecture
   where all intended multicast receivers are encoded as bitmask in the
   Multicast packet header within different encapsulations such as
   [I-D.draft-wijnands-mpls-bier-encapsulation-00].  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
   ISIS for IP [RFC7142] protocol to support distribution of information
   necessary for operation of BIER domains.  This document defines a new
   TLV to be distributed by every router participating in such BIER
   domains.

Przygienda               Expires March 31, 2015                 [Page 2]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

2.  Terminology

   Some of the terminology specified in
   [I-D.draft-wijnands-bier-architecture-00] 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 BFER's).

   BM:  Bit Mask (A bit stream of a certain fixed length.  Each Bit
      represents a receiver).

   P-BM:  Packet Bit Mask (A Bit Mask included in the Multicast Packet).

   BP:  Bit Position (A single Bit from the Bit Mask that represents a
      receiver).

   BFR:  Bit Forwarding Router (A router that participates in Bit Index
      Multipoint Forwarding).

   BFIR:  Bit Forwarding Ingress Router (The ingress border router that
      inserts the BM into the packet).

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

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

   BIFT:  Bit Index Forwarding Table (A Bit index forwarding table).

   BMS:  Bit Mask Set. Set containing bit positions of all BFER
      participating in a set.

   BMP:  Bit Mask Position, a given bit in a BMS.

3.  IANA Considerations

   This document requests IANA to assign sub-TLV type values from the
   ISIS router capability TLV [RFC4971] registry.

4.  Concepts

Przygienda               Expires March 31, 2015                 [Page 3]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

4.1.  BIER as Capability

   This draft introduces a sub-TLV in the router capabilites TLV
   [RFC4971] to distribute the information.  Any of the router's
   loopback addresses that it originates are considered BFR prefixes as
   required by [I-D.draft-wijnands-bier-architecture-00].  The question
   whether a particular loopback address is routable in a specific
   topology [RFC5120] can be resolved by
   [I-D.draft-xu-isis-routable-ip-address-01].

4.2.  BIER Domain Identifier

   ISIS can carry BIER information not only for a single BIER domain but
   for multiple, distinct domains.  This allows to run many disjoint
   BIER layers within the same Multi-Topology [RFC5120] easily instead
   of always forcing different multicast overlays to share the exactly
   same set of BFRs and resources.  Moreover, multi topology [RFC5120]
   can be used for the purpose of restricting links that certain set of
   BIER domains can use or change metrics of such links.  A BIER set is
   therefore always uniquely identified by the tuple of topology T,
   domain D it belongs to and its number S, denoted as <T,D,S>.  The
   domain itself has as its unique attributes the encapsulation, bitmask
   length and the type of tree it is using to forward BIER frames
   (currently always SPF).

5.  Procedures

5.1.  Enabling a BIER Domain

   A given domain D in a multi-topology T [RFC5120] (denoted as <T,D>
   from now on) is normally not advertised to preserve the scaling of
   the protocol (i.e.  ISIS carries no TLVs containing any of the
   elements related to <T,D>) and is enabled by a first BIER sub-TLV
   (Section 6.1) containing <T,D> being advertised into the area.  The
   trigger itself is outside the scope of this draft but can be .e.g. a
   VPN desiring to initiate a domain as MP2MP or P2MP tree or a BMP
   being administratively assigned to a BFER and advertised via BIER TLV
   into the area or any other means within Multicast BIER Overlay(s)
   using BIER domains.

5.2.  Length of Bitmasks

   All routers in the flooding scope of the BIER TLVs SHOULD advertise
   the same bit mask length for a given <T,D>.  A router discovering
   bitmask lengths advertised that are shorter than its own MUST report
   a misconfiguration of a specific <T,D>.  Each router MUST compute
   BFTs for <T,D> using only routers having the same mask length as its
   own advertised Bit Mask Length in BIER sub-TLV for <T,D>.

Przygienda               Expires March 31, 2015                 [Page 4]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

5.2.1.  Special Consideration

   The same router MAY advertise for different <T,D> combinations two
   different mask lengths.  This allows to cleanly delineate domains
   crossing the same router but using different mask lengths in the
   encoding, even within the same topology.

5.3.  Encapsulation

   Since encapsulation is an attribute of a domain <T,D> just like
   bitmask length, all rules that apply to Bitmask Length per
   Section 5.2 apply to it well.

5.4.  Label Advertisements

   Each router MAY advertise within the sub-TLV of an according <T,D>
   (denoted further as TLV<T,D>) a valid starting label value and a non-
   zero range length.  It MUST advertise a valid label value and a non-
   zero range length IF it has computed itself as being on the BFT
   rooted at any of the BFRs with valid BFR-ids (except itself)
   participating in <T,D>.

   A router CAN withdraw its TLV<T,D> if it does not want to participate
   in the domain due to resource constraints, label space optimization,
   administrative configuration or any other reasons.  In case a router
   advertises a label range size of 0 for <T,D> it MUST be excluded from
   the BIER BFTs for <T,D>.

5.4.1.  Special Consideration

   A router MUST advertise a for <T,D> label range size that guarantees
   to cover the maximum BFR-id injected into <T,D> (which implies a
   certain set id as described in
   [I-D.draft-wijnands-bier-architecture-00]).  Any router that violates
   this condition MUST be excluded from BIER BFTs for <T,D>.

5.5.  BFR-id Advertisements

   Each BFER MAY advertise with its TLV<T,D> the according BFR-id that
   it has administratively chosen.

   If two BFRs advertise in their TLV<T,D> the same value for BFR-id,
   all routers MUST report it as misconfiguration and disregard those
   routers for all BIER calculations and procedures to align with
   [I-D.draft-wijnands-bier-architecture-00].  Such routers with
   colliding assignments MAY still act as BFIRs but will be never able
   to receive traffic.

Przygienda               Expires March 31, 2015                 [Page 5]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

6.  Packet Formats

   All ISIS BIER information is carried within the router capability TLV
   [RFC4971] with S bit clear.

6.1.  BIER BFR sub-TLV

   This sub-TLV carries the information for the BIER domains that the
   router participates in as BFR.  It can repeat multiple times.  If the
   same <T,D> is advertised more than once, the first one in the first
   sub-TLV in the fragment with the lowest ID MUST be used.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Type             |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     MT-ID     |   Bier Domain ID              |   Bit Msk Len |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Lbl Range Size|                    Label                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   BFR-id                      |A|R|T| Reserv  |  Encaps       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  TBD1.

   Length:  2 octets.

   MT-ID:  Multi-Topology [RFC5120], 1 octet.

   BIER Domain ID:  Unique identifier for a BIER domain, 2 octets.

   Label Range Size:  Number of labest in the range used on
      encapsulation for this BIER domain, 1 octet.

   Label:  First label of the range used on encapsulation for this BIER
      domain, 20 bits.  The label is used by e.g.
      [I-D.draft-wijnands-mpls-bier-encapsulation-00] to forward traffic
      to sets of BFERs.

   Local BitMask Length:  Bitmask length for this BFR per
      [I-D.draft-wijnands-bier-architecture-00].

   Encapsulation Type:  The BIER encapsulation type, 1 octet.  Allowed
      values are:

Przygienda               Expires March 31, 2015                 [Page 6]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

      0  MPLS per [I-D.draft-wijnands-mpls-bier-encapsulation-00].

   A  Indicates administratively set value if set, otherwise the BFR-id
      value MUST be considered as not assigned in this TLV.

   R  Reserved for future use.  MUST be 0.

   T  Reserved for future use.  MUST be 0.

   Reserved  MUST be 0 on send, ignored on receive.

7.  Security Considerations

   The extension does not introduce any known new protocol
   vulnerabilities.

8.  Acknowledgements

   The draft is aligned with the
   [I-D.draft-kumar-ospf-bier-extension-00] draft as far as the protocol
   mechanisms overlap.

9.  Normative References

   [I-D.draft-kumar-ospf-bier-extension-00]
              Psenak, P. and IJ. Wijnands, "OSPF Extension for Bit Index
              Explicit Replication", internet-draft draft-ietf-ospf-
              prefix-link-attr-00.txt, September 2014.

   [I-D.draft-wijnands-bier-architecture-00]
              Wijnands, IJ., "Stateless Multicast using Bit Index
              Explicit Replication Architecture", internet-draft draft-
              wijnands-bier-architecture-00.txt, February 2014.

   [I-D.draft-wijnands-mpls-bier-encapsulation-00]
              Wijnands et al., IJ., "Bit Index Explicit Replication
              using MPLS encapsulation", internet-draft draft-wijnands-
              mpls-bier-encapsulation-00.txt, February 2014.

   [I-D.draft-xu-isis-routable-ip-address-01]
              Chunduri et al., U., "Carrying Routable IP Addresses in
              IS-IS Router Capability TLV", internet-draft draft-xu-
              isis-routable-ip-address-01.txt, September 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

Przygienda               Expires March 31, 2015                 [Page 7]
Internet-Draft    draft-przygienda-bier-isis-ranges-00    September 2014

   [RFC4971]  Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
              System to Intermediate System (IS-IS) Extensions for
              Advertising Router Information", RFC 4971, July 2007.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

   [RFC7142]  Shand, M. and L. Ginsberg, "Reclassification of RFC 1142
              to Historic", RFC 7142, February 2014.

Author's Address

   Tony Przygienda
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA

   Email: antoni.przygienda@ericsson.com

Przygienda               Expires March 31, 2015                 [Page 8]