Internet DRAFT - draft-wang-bier-lite-ospf-extension

draft-wang-bier-lite-ospf-extension






BIER WG                                                          C. Wang
Internet-Draft                                                  Z. Zhang
Intended status: Standards Track                         ZTE Corporation
Expires: April 18, 2016                                 October 16, 2015


                      OSPF Extension for BIER-Lite
                 draft-wang-bier-lite-ospf-extension-01

Abstract

   Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
   an architecture that provides optimal multicast forwarding through a
   "BIER domain" without requiring intermediate routers to maintain any
   multicast related per-flow state.  BIER also does not require any
   explicit tree-building protocol for its operation.  Currently, the
   data plane of BIER is apt to use BIER-MPLS encapsulation to transmit
   multicast traffic.  However, this document tries to propose a
   solution name BIER-Lite about how to extend OSPF protocol to support
   BIER forwarding in non-MPLS underlay network instead of MPLS underlay
   network.

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
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   This Internet-Draft will expire on April 18, 2016.

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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Convention and Terminology . . . . . . . . . . . . . . . . . .  5
   3.  BIER-Lite Sub-TLV in OSPF extension  . . . . . . . . . . . . .  6
   4.  Flooding scope of BIER-Lite Information  . . . . . . . . . . .  8
   5.  Considerations on BIER-Lite  . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13































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1.  Introduction

   Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
   an architecture that provides optimal multicast forwarding through a
   "BIER domain" without requiring intermediate routers to maintain any
   multicast related per-flow state.  BIER also does not require any
   explicit tree-building protocol for its operation.  A multicast data
   packet enters a BIER domain at a "Bit-Forwarding Ingress Router"
   (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding
   Egress Routers" (BFERs).  The BFIR router adds a BIER header to the
   packet.  The BIER header contains a bit-string in which each bit
   represents exactly one BFER to forward the packet to.  The set of
   BFERs to which the multicast packet needs to be forwarded is
   expressed by setting the bits that correspond to those routers in the
   BIER header.

   Currently, the data plane of BIER is defined in BIER-MPLS
   encapsulation [I-D.ietf-bier-mpls-encapsulation] to transmit
   multicast traffic in MPLS encapsulation.  Admittedly, BIER-MPLS
   introduces the advantages of MPLS forwarding.  However, this requires
   the underlay network is an MPLS network, and along the path, there
   need label switching and label lookup.  Additionally, every BFR
   requires per-label forwarding table to assist BIER forwarding.
   What!_s more, prior of that, IGP protocol or BGP protocol requires a
   precise mechanism to generate these label information, after that, to
   advertise these label information to form the per-label forwarding
   table between the label and the bit index forwarding table(BIFT).
   Sometimes, how to categorize this label information in differentiated
   MPLS Encapsulation sub-sub-TLV is a difficult decision.  And some
   other times, after the label information advertisement, there may be
   some redundant label information as well as some redundant label
   forwarding table because each BFR advertises continuous labels for
   different Set Identifiers for each combination of Sub-domain and
   BitStringLength which may be redundant because traffic to some BFERs
   may not transit this advertising node, especially when these BFERs
   belonging to the same Set Identifier reside together geographically.

   In fact, some multicast scenario may be not in MPLS network, or may
   be in a relatively simple network.  In other words, if BIER
   forwarding uses IP forwarding instead of MPLS forwarding in these
   kind of networks, it would be much easier to deploy BIER in current
   deployment.  Of course, if the BIER forwarding is compatible with
   BIER-MPLS encapsulation forwarding, that would be much more
   significant.

   The following section tries to propose how to extend OSPF protocol to
   support BIER forwarding in non-MPLS underlay network instead of MPLS
   underlay network.



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   And this document names this solution as BIER-Lite.


















































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2.  Convention and Terminology

   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].

   The terms about BIER are defined in [I-D.ietf-bier-architecture].












































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3.  BIER-Lite Sub-TLV in OSPF extension

   Given that the BIER-Lite-specific information that a BFR needs to
   advertise to other BFRs are associated with the BFR-Prefix, the OSPF
   Extended Prefix Opaque LSA [I-D.ietf-ospf-prefix-link-attr] is used
   to flood BIER-Lite-specific information.

   Here, in order to implement the BIER forwarding in non-MPLS network
   and simplify the BIER forwarding mentioned in
   [I-D.ietf-bier-mpls-encapsulation] , a new BIER-Lite sub-TLV of the
   Extended Prefix Opaque LSA is defined to advertise BIER-Lite-specific
   information, which is illustrated as follow in Figure 1.  Multiple
   BIER-Lite Sub-TLVs may be included in the Extended Prefix TLV.


      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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Sub-domain-ID |     MT-ID     |              BFR-id           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | M |            Resvered                       | BSL Identifier|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 1: BIER-Lite Sub-TLV in OSPF extension

     Type: indicates BIER-Lite sub-TLV

     Length: 8 octet.

     Sub-domain-ID: unique value identifying the BIER sub-domain within
   the BIER domain, as described in section 1 of
   [I-D.ietf-bier-architecture].

     MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies
   the topology that is associated with the BIER sub-domain.

     BFR-id: a 2 octet field encoding the BFR-id, as documented in
   section 2 [I-D.ietf-bier-architecture].  If the BFR-id is zero, it
   means, the advertising router is not advertising any BFR-id.

     M: indicating whether is compatible with BIER MPLS Encapsulation
   sub-sub-TLV.  When M is set to 1, it means if there has BIER MPLS
   Encapsulation sub-sub-TLV, validating and using the BSL information
   and label information in BIER MPLS Encapsulation sub-sub-TLV.  When M
   is set to 0, it means validating and using the BSL information in the



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   BSL Identifier even if there has BIER MPLS Encapsulation sub-sub-TLV
   and ignoring all the information in BIER MPLS Encapsulation sub-sub-
   TLV.

     BSL Identifier: indicating the BSL the sending BFR supporting.

   The sending BFR may support one or several BSLs, as following:

   00000001: represents BSL 64 bits;

   00000010: represents BSL 128 bits;

   00000100: represents BSL 256 bits;

   00001000: represents BSL 512 bits;

   00010000: represents BSL 1024 bits;

   00100000: represents BSL 2048 bits;

   01000000: represents BSL 4096 bits;

   Each bit represents one BSL.  When there are two or more bits set,
   that means the sending BFR supports more than one BSL.  For example,
   if the BSL Identifier is 00010101, it means the sending BFR supports
   1024 bits, 256 bits and 64 bits.

   Each BFR sub-domain MUST be associated with a single OSPF topology
   that is identified by the MT-ID.  If the association between BIER
   sub-domain and OSPF topology advertised in the BIER-Lite sub-TLV is
   different from the association on the receiving router, BIER-Lite
   sub-TLV SHOULD be ignored.

   On the other hand, the BIER-Lite sub-TLV, which encapsulates the BSL
   information together with the BIER Info sub-TLV, may be a
   complementation and an extension of BIER Info sub-TLV defined in
   [I-D.ietf-bier-ospf-bier-extensions].  Additionally, adding an M
   identifier in the BIER Info sub-TLV
   [I-D.ietf-bier-ospf-bier-extensions] to be compatible with BIER MPLS
   encapsulation sub-sub-TLV.  So, BIER-Lite sub-TLV can also multiplex
   and extend BIER Info sub-TLV defined in
   [I-D.ietf-bier-ospf-bier-extensions] instead of defining a new TLV.









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4.  Flooding scope of BIER-Lite Information

   Flooding scope of the OSPF Extended Prefix Opaque LSA
   [I-D.ietf-ospf-prefix-link-attr] that is used for advertising BIER-
   Lite sub-TLV is set to area.  To allow BIER deployment in a multi-
   area environment, OSPF must propagate BIER-Lite information between
   areas.












































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5.  Considerations on BIER-Lite

   TBD.
















































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6.  Security Considerations

   It will be considered in a future revision.
















































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7.  IANA Considerations

   This document can request a new allocation from OSPF Extended Prefix
   sub-TLV registry for BIER-Lite sub-TLV.  Or it can multiplex the BIER
   Info sub-TLV defined in [I-D.ietf-bier-ospf-bier-extensions] and
   extend M information and BSL Identifier information to BIER Info sub-
   TLV.












































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8.  References

8.1.  Normative References

   [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>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <http://www.rfc-editor.org/info/rfc4915>.

8.2.  Informative 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-isis-extensions]
              Ginsberg, L., Aldrin, S., Zhang, J., and T. Przygienda,
              "BIER support via ISIS",
              draft-ietf-bier-isis-extensions-00 (work in progress),
              April 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-02 (work in progress),
              August 2015.

   [I-D.ietf-bier-ospf-bier-extensions]
              Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
              Przygienda, T., Zhang, J., and S. Aldrin, "OSPF Extensions
              For BIER", draft-ietf-bier-ospf-bier-extensions-00 (work
              in progress), April 2015.

   [I-D.ietf-ospf-prefix-link-attr]
              Psenak, P., Gredler, H., rjs@rob.sh, r., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", draft-ietf-ospf-prefix-link-attr-13 (work
              in progress), August 2015.





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Authors' Addresses

   Cui Wang
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: wang.cui1@zte.com.cn


   Zheng Zhang
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: zhang.zheng@zte.com.cn

































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