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Network Working Group                                              X. Xu
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                  Huawei
Expires: February 26, 2016                                      K. Patel
                                                             I. Wijnands
                                                                   Cisco
                                                           A. Przygienda
                                                                Ericsson
                                                         August 25, 2015


                        BGP Extensions for BIER
                    draft-xu-bier-idr-extensions-00

Abstract

   Bit Index Explicit Replication (BIER) is a new multicast forwarding
   architecture which doesn't require an explicit tree-building protocol
   and doesn't require intermediate routers to maintain any multicast
   state.  BIER is applicable in a multi-tenant data center network
   environment for efficient delivery of Broadcast, Unknown-unicast and
   Multicast (BUM) traffic while eliminating the need for maintaining a
   huge amount of multicast state in the underlay.  This document
   describes BGP extensions for advertising the BIER-specific
   information.  These extensions are applicable in those multi-tenant
   data centers where BGP instead of IGP is deployed as an underlay for
   network reachability advertisement.  These extensions may also be
   applicable in other scenarios.

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 26, 2016.






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Copyright Notice

   Copyright (c) 2015 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
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   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BIER Path Attribute . . . . . . . . . . . . . . . . . . . . .   3
   4.  Originating BIER Attribute  . . . . . . . . . . . . . . . . .   4
   5.  Restrictions on Sending/Receiving . . . . . . . . . . . . . .   5
   6.  Deployment Considerations . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
   a new multicast forwarding architecture which doesn't require an
   explicit tree-building protocol and doesn't require intermediate
   routers to maintain any multicast state.  BIER is applicable in a
   multi-tenant data center network environment for efficient delivery
   of Broadcast, Unknown-unicast and Multicast (BUM) traffic while
   eliminating the need for maintaining a huge amount of multicast state
   in the underlay [I-D.ietf-bier-use-cases].  This document describes
   BGP extensions for advertising the BIER-specific information.  More
   specifically, in this document, we define a new optional, non-
   transitive BGP attribute, referred to as the BIER attribute, to
   convey the BIER-specific information such as BFR-ID, BitString Length
   (BSL) and so on.  In addition, this document specifies procedures to
   prevent the BIER attribute from "leaking out" of a BIER domain .



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   These extensions are applicable in those multi-tenant data centers
   where BGP instead of IGP is used as an underlay
   [I-D.ietf-rtgwg-bgp-routing-large-dc].  These extensions may also be
   applicable to other BGP based network scenarios.

1.1.  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].

2.  Terminology

   This memo makes use of the terms defined in [RFC4271] and
   [I-D.ietf-bier-architecture].

3.  BIER Path Attribute

   This draft defines a new optional, transitive BGP path attribute,
   referred to as the BIER attribute.  This attribute can be attached to
   a BGP UPDATE message by the originator so as to indicate the BIER-
   specific information of a particular BFR which is identified by the
   /32 or /128 address prefix contained in the NLRI.  In other words, if
   the BIER path attribute is present, the NLRI is treated by BIER as a
   "BFR-prefix".  When creating a BIER attribute, a BFR needs to include
   one BIER TLV for every <Sub-domain, BFR-ID> pair that it supports.

   The attribute type code for the BIER Attribute is TBD.  The value
   field of the BIER Attribute contains one or more BIER TLV as shown in
   Figure 1.

       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=TBD            |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Sub-domain   |            BFR-ID             |   Reserved    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                                                               ~
       |                           Sub-TLVs                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................
                             Figure 1:BIER TLV

      Type: Two octets encoding the BIER TLV Type: TBD.

      Length: Two octets encoding the length in octets of the TLV,
      including the type and length fields.  The length is encoded as an




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      unsigned binary integer.  (Note that the minimum length is 8,
      indicating that no sub-TLV is present.)

      Sub-domain: a one-octet field encoding the sub-domain ID
      corresponding to the BFR-ID.

      BFR-ID: a two-octet field encoding the BFR-ID.

      Sub-TLVs: contains one or more sub-TLV.  The BIER MPLS
      Encapsulation sub-TLV is one of such sub-TLVs.

   The BIER MPLS Encapsulation sub-TLV is encoded as follows:

       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=TBD            |         Length=8              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Label Range Base               |Lbl Range Size |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      BSL      |                    Reserved                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   Figure 2:BIER MPLS Encapsulation sub-TLV

      Type:TBD

      Length:12

      Label Range Size: a one-octet field indicating the size of the
      label range.

      Label Range Base: a 3-octet field where the 20 rightmost bits
      represent the first label in the label range while the other bits
      MUST be set to 0 when transmitting, and MUST be ignored upon
      receipt.

      BSL: a one-octet field indicating the length of the Bitstring in
      4-octets.  The field MUST be filled with one of the valid BSL
      values as specified in [I-D.ietf-bier-architecture].  Upon
      receiving a BSL-TLV containing an invalid BSL value, it MUST be
      ignored.

4.  Originating BIER Attribute

   An implementation that supports the BIER attribute MUST support a
   policy to enable or disable the creation of the BIER attribute and
   its attachment to specific BGP routes.  An implementation MAY disable
   the creation of the BIER attribute unless explicitly configured to do



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   so otherwise.  A BGP speaker MUST only attach the locally created
   BIER attribute to a BGP UPDATE message in which at least one of its
   BFR-prefixes is contained in the NLRI.

5.  Restrictions on Sending/Receiving

   An implementation that supports the BIER attribute MUST support a
   per-EBGP-session policy, that indicates whether the attribute is
   enabled or disabled for use on that session.  The BIER attribute MUST
   NOT be sent on any EBGP peers for which the session policy is not
   configured.  If an BIER attribute is received on a BGP session for
   which session policy is not configured, then the received attribute
   MUST be treated exactly as if it were an unrecognised non-transitive
   attribute.  That is, "it MUST be quietly ignored and not passed along
   to other BGP peers".

   To prevent the BIER attribute from "leaking out" of an BIER domain,
   each BGP router on the BIER domain MUST support an outbound route
   announcement policy.  Such a policy MUST be disabled on each EBGP
   session by default unless explicitly configured.

6.  Deployment Considerations

   It's assumed by this document that the BIER domain is aligned with
   the Administrative Domain (AD) which are composed of multiple ASes
   (either private or public ASes).  Use of the BIER attribute in other
   scenarios is outside the scope of this document.

   Since the BIER attribute is an optional, transitive BGP path
   attribute, a non-BFR BGP speakers could still advertise the received
   route with a BIER attribute.  This is desirable in the incremental
   deployment scenario where a BGP speaker could tunnel a BIER packet or
   the payload of a BIER packet to a BFER directly if the BGP next-hop
   of the route for that BFER is a non-BFR.  Furthermore, a BGP speaker
   is allowed to tunnel a BIER packet to the BGP next-hop if these two
   BFR-capable BGP neighbors are not directly connected (e.g., multi-hop
   EBGP) .

7.  Acknowledgements

   Thanks a lot for Eric Rosen and Peter Psenak for their valuable
   comments on this document.

8.  IANA Considerations

   IANA is requested to assign a codepoint in the "BGP Path Attributes"
   registry to the BIER attribute.  IANA shall create a registry for
   "BGP BIER Attribute Types".  The type field consists of two octets,



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   with possible values from 1 to 655355 (The value 0 is "reserved".)
   The allocation policy for this field is to be "First Come First
   Serve".  Type codes should be allocated for BIER TLV and BIER MPLS
   Encapsulation sub-TLV respectively.

9.  Security Considerations

   This document introduces no new security considerations beyond those
   already specified in [RFC4271].

10.  References

10.1.  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-02 (work in
              progress), July 2015.

   [I-D.ietf-bier-mpls-encapsulation]
              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J., and
              S. Aldrin, "Encapsulation for Bit Index Explicit
              Replication in MPLS Networks", draft-ietf-bier-mpls-
              encapsulation-01 (work in progress), June 2015.

   [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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

10.2.  Informative References

   [I-D.ietf-bier-use-cases]
              Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
              Przygienda, T., arkadiy.gulko@thomsonreuters.com, a.,
              Robinson, D., and V. Arya, "BIER Use Cases", draft-ietf-
              bier-use-cases-01 (work in progress), August 2015.

   [I-D.ietf-rtgwg-bgp-routing-large-dc]
              Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for
              routing in large-scale data centers", draft-ietf-rtgwg-
              bgp-routing-large-dc-06 (work in progress), August 2015.



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Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Mach Chen
   Huawei

   Email: mach.chen@huawei.com


   Keyur Patel
   Cisco

   Email: keyupate@cisco.com


   IJsbrand Wijnands
   Cisco

   Email: ice@cisco.com


   Antoni Przygienda
   Ericsson

   Email: antoni.przygienda@ericsson.com





















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