[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

BIER Working Group                                          IJ. Wijnands
Internet-Draft                                             Cisco Systems
Intended status: Informational                                     X. Xu
Expires: February 16, 2018                                        Huawei
                                                              H. Bidgoli
                                                                   Nokia
                                                         August 15, 2017


     An Optional Encoding of the BIFT-id Field in the non-MPLS BIER
                             Encapsulation
          draft-wijnandsxu-bier-non-mpls-bift-encoding-00.txt

Abstract

   Bit Index Explicit Replication (BIER) is an architecture that
   provides optimal multicast forwarding through a "multicast domain",
   without requiring intermediate routers to maintain any per-flow state
   or to engage in an explicit tree-building protocol.  The Multicast
   packet is encapsulated using a BIER Header and transported through an
   MPLS or non-MPLS network.  When MPLS is used as the transport, the
   Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label.
   When non-MPLS transport is used, the BIFT is identified by a 20bit
   value.  This document describes one way of encoding the 20bit value.

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 February 16, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





Wijnands, et al.        Expires February 16, 2018               [Page 1]


Internet-Draft     Non-MPLS BIER BIFT-id Encapsulation       August 2017


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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Specification of Requirements . . . . . . . . . . . . . . . .   3
   4.  The Bit Index Forwarding Table  . . . . . . . . . . . . . . .   3
   5.  The Non-MPLS Static BIFT Encoding . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
   an architecture that provides optimal multicast forwarding through a
   "multicast domain", without requiring intermediate routers to
   maintain any per-flow state or to engage in an explicit tree-building
   protocol.  The Multicast packet is encapsulated
   [I-D.ietf-bier-mpls-encapsulation] using a BIER Header and
   transported through an MPLS or non-MPLS network.  When MPLS is used
   as the transport, the Bit Indexed Forwarding Table (BIFT) is
   identified by a MPLS Label.  When non-MPLS transport is used, the
   BIFT is identified by a 20bit value.  This document describes one way
   of encoding the 20bit value, based on the Sub-Domain (SD), Set
   Identifier (SI) and BitStringLength (BSL) values.

   The BIER architecture requires that a BFR has a BIFT for every
   combination of <SD, SI, BSL> that is being used.  When processing a
   BIER packet, the correct BIFT is inferred from the BIFT-id field of
   the encapsulation.  When the non-MPLS encapsulation is used in a
   given BIER domain, it may be desirable for the a BIFT-id to be unique
   in that domain.  This document describes an OPTIONAL method that can
   be used to form domain-wide unique BIFT-ids based on the <SD, SI,
   BSL> triples.  If in the future the BIER architecture is extented
   with an additonal BIFT argument, this encoding does not generate
   domain-wide unique idenifiers anymore.



Wijnands, et al.        Expires February 16, 2018               [Page 2]


Internet-Draft     Non-MPLS BIER BIFT-id Encapsulation       August 2017


   This encoding, if used, is only for the convenience of the network
   adminstrators.  When forwarding a BIER packet, the BIFT-id is used as
   an opaque 20-bit value that identifies a BIFT; the forwarding
   procedures do not parse the 20-bit value, they just use it as a
   lookup key.

2.  Terminology and Definitions

   Readers of this document are assumed to be familiar with the
   terminology and concepts of the documents listed as Normative
   References.  For convenience, some of the more frequently used terms
   appear below.

   BIER:
      Bit Indexed Explicit Replication.

   BIFT-id:
      Bit Indexed Forwarding Table Identifier.

3.  Specification of Requirements

   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].

4.  The Bit Index Forwarding Table

   In MPLS networks a BIER label is allocated for each Bit Index
   Forwarding Table (BIFT) from the platform specific, downstream label
   database ([I-D.ietf-bier-mpls-encapsulation]).  This label is
   associated with a particular combination of BIER Sub-Domain (SD), Set
   Identifier (SI) and BitStringLength (BSL).  In order for the network
   to know which MPLS label represents a particular combination of <SD,
   SI, BS>, this mapping has to be advertised through the network.  This
   is currently done through an IGP or BGP.  In MPLS networks this is
   not a drawback as the MPLS label has to be advertised anyway.

   When the non-MPLS encoding is chosen, there is no need to advertise
   the BIFT-id to <SD, SI, BSL> mapping if the BIFT-id is domain-wide
   unique.  For this reason we're defining an encoding that MAY be used
   by operators to compute the domain-wide unique BIFT-id values from
   the SD, SI and BSL.  Although the BIFT-id is not expected to change,
   it may change when the BSL mismatch procedures
   [I-D.ietf-bier-architecture] section 6.10.2 are applied.







Wijnands, et al.        Expires February 16, 2018               [Page 3]


Internet-Draft     Non-MPLS BIER BIFT-id Encapsulation       August 2017


5.  The Non-MPLS Static BIFT Encoding

   Find below the first 32 bits of the BIER header, encoding the SD, SI
   and BSL into the 20 bit BIFT-id field.


     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  BSL  |       SD      |       SI      | TC  |S|       TTL     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     |-------- 20 bit BIFT-id Field ---------|


                                 Figure 1

      BSL: This 4-bit field encodes the length in bits of the BitString.
      These are the same values as documented in
      [I-D.ietf-bier-mpls-encapsulation].

      SD: This is a 8-bit field that encodes the Sub-Domain as described
      in [I-D.ietf-bier-architecture].

      SI: This is a 8-bit field that encodes the Set-ID as described in
      [I-D.ietf-bier-architecture].

      TC: This is a 3-bit field set to 000 (following
      [I-D.ietf-bier-mpls-encapsulation]).

      S: This is a 1-bit field set to 1 (following
      [I-D.ietf-bier-mpls-encapsulation]).

      TTL: See [I-D.ietf-bier-mpls-encapsulation].

6.  Security Considerations

   This document does not introduce any new security considerations
   other than already discussed in [I-D.ietf-bier-architecture].

7.  IANA Considerations

   There is no IANA consideration.

8.  Acknowledgments

   The authors like to thank the following people for their comments and
   contributions to this document; Eric Rosen, Neale Ranns, Jeffrey
   Zhang.




Wijnands, et al.        Expires February 16, 2018               [Page 4]


Internet-Draft     Non-MPLS BIER BIFT-id Encapsulation       August 2017


9.  Normative References

   [I-D.ietf-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-07 (work in
              progress), June 2017.

   [I-D.ietf-bier-mpls-encapsulation]
              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
              Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
              Explicit Replication in MPLS and non-MPLS Networks",
              draft-ietf-bier-mpls-encapsulation-07 (work in progress),
              June 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

Authors' Addresses

   IJsbrand Wijnands
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com


   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Hooman Bidgoli
   Nokia
   600 March Rd.
   Ottawa, Ontario  K2K 2E6
   Canada

   Email: hooman.bidgoli@nokia.com







Wijnands, et al.        Expires February 16, 2018               [Page 5]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/