BIER Flooding Mechanism
draft-zhang-bier-flooding-00

Versions: 00                                                            
BIER WG                                                     Zheng. Zhang
Internet-Draft                                              BenChong. Xu
Intended status: Standards Track                         ZTE Corporation
Expires: April 3, 2018                                September 30, 2017


                        BIER Flooding Mechanism
                    draft-zhang-bier-flooding-00.txt

Abstract

   This document introduces a method to flood BIER information in hybrid
   network to build BIER forwarding plane.

Status of This Memo

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   This Internet-Draft will expire on April 3, 2018.

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Table of Contents

   1.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Scheduled Update  . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Triggered Update  . . . . . . . . . . . . . . . . . . . .   4
   3.  Message Format  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  PFM message . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  BIER information TLV  . . . . . . . . . . . . . . . . . .   5
     3.3.  BIER MPLS Encapsulation sub-TLV . . . . . . . . . . . . .   6
     3.4.  Optional BIER sub-domain BSL conversion sub-TLV . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Problem Statement

   Some networks have been deployed widely are hybrid networks.  There
   are different dynamic routing protocols running in the hybrid
   networks.  Multicast services can also be provided in these kinds of
   networks because of the protocol independent feature of PIM.

   BIER [I-D.ietf-bier-architecture] provides a new architecture for the
   forwarding of multicast data packets.  It does not require a protocol
   for explicitly building multicast distribution trees, nor does it
   require intermediate nodes to maintain any per-flow state.
   [I-D.ietf-bier-isis-extensions] and
   [I-D.ietf-bier-ospf-bier-extensions] are good at establishing BIER
   forwarding plane in network which uses OSPF or IS-IS as BIER underlay
   protocol.




















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                              |                |
                     .........|................|.........
                     .  ISIS  |                |        .
                     .        |                |        .
                     .       MR1--------------MR2       .
                     .        |  .          .  |        .
                     .        |    .      .    |        .
                     .        |      .  .      |        .
                     .        |       ..       |        .
                     .        |     .    .     |        .
                     .        |   .        .   |        .
                     .        | .            . |        .
                     .        MR3              MR4      .
                     .       /  \             /  \      .
                     ....................................
                            /    \           /    \
                           /      \         /      \
                          /        \       /        \
                     ...................  ................
                     .    B1--------B2 .  .B3--------B4  .
                     .                 .  .              .
                     .   Rm            .  . Rx           .
                     .       ...       .  .     ...      .
                     .            Rn   .  .         Ry   .
                     .                 .  .              .
                     .         OSPF    .  .       OSPF   .
                     ...................  ................
                       Figure 1: An typical hybrid network

   In the mentioned networks, there are more than one dynamic routing
   protocols running in the networks.  For example in figure 1, this is
   a partial typical network in actually deployment.  Two different
   dynamic routing protocols and are used in the network.  Sometimes
   static configured routes also are used in some parts of the network.
   In order to deploy BIER multicast, we can divide the network into
   several BIER domains.  Obviously the efficiency slows down due to
   multiple encapsulating/ decapsulating executions.

2.  Solution

   The Bootstrap Router mechanism (BSR) [RFC5059] is a commonly used
   mechanism for distributing dynamic Group to RP mappings in PIM.  It
   is responsible for flooding information about such mappings
   throughout a PIM domain, so that all routers in the domain can have
   the same information.  [I-D.ietf-pim-source-discovery-bsr] defines a
   mechanism that can flood any kind of information throughout a PIM
   domain.  This document borrows the idea from the two drafts,
   introduces a mechanism to flood BIER node's information throughout a



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   BIER domain to build BIER forwarding plane.  Nodes can use unicast
   forwarding table directly to establish BIER forwarding plane.

   The validation processing of PFM messages is the same as the
   definition in [I-D.ietf-pim-source-discovery-bsr] section 3.2.

   BIER node originates BIER information TLV and optional associated
   sub-TLVs in PFM message.  The PFM messages are flooded by throughout
   the BIER domain.  BFR gets routing information from the unicast
   forwarding table directly, and computes BIER forwarding table.  Then
   BIER forwarding plane is established.

2.1.  Scheduled Update

   Because PIM advertisement is scheduled, the node's BIER information
   is refreshed periodically.  In case one node's BIER information
   changes or expires, the other nodes recompute the BIER forwarding
   table.  The holdtime in the BIER information TLV is used to make the
   item expired.

2.2.  Triggered Update

   If the BIER node's configuration changes, such as BFR-id, the node
   should send update PFM messages immediately.  Then other nodes can
   recompute the new BIER forwarding table.

3.  Message Format

3.1.  PFM message

   New TLVs are defined in PFM message to flood node's BIER information,
   such as BFR-id, BFR-prefix and so on.  The new TLVs align exactly
   with the definition and restrictions in
   [I-D.ietf-bier-isis-extensions] and
   [I-D.ietf-bier-ospf-bier-extensions].
















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         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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |PIM Ver| Type  |N|  Reserved   |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Originator Address (Encoded-Unicast format)        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Type 1               |          Length 1             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Value 1                            |
       |                               .                               |
       |                               .                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                               .                               |
       |                               .                               |
       |          Type n               |          Length n             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Value n                            |
       |                               .                               |
       |                               .                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 2: PFM message format

   The format of PFM message is defined in
   [I-D.ietf-pim-source-discovery-bsr].

   Originator Address: The router's address that originate the message.
   The address SHOULD be the same with the node's BFR-prefix.

   The other fields is the same as definition in
   [I-D.ietf-pim-source-discovery-bsr].

3.2.  BIER information TLV

   A new type of TLV is defined in PFM message.  This new type TLV is
   named by BIER information TLV.  Two types of sub-TLV are associated
   with it.  There is no optional BIER tree type sub-TLV in PFM message
   because of the independence of routing protocol.













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         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 = 1               |          Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Reserved    |  subdomain-id   |           BFR-id            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Holdtime           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              BFR-prefix (Encoded-Unicast format)              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 3: BIER information TLV

   o  Type: The value of type should be assigned by IANA.

   o  Length: The total length of the BIER information TLV except for
      the first two fields.

   o  Reserved: Must be 0 on transmission, ignored on reception.  May be
      used in future version. 1 octets.

   o  Subdomain-id: Unique value identifying the BIER sub-domain. 1
      octet.

   o  BFR-id: The value of BFR-id defined in [BIER-arch], 2 octets. 0 is
      invalid value.  If the value of this field is set to 0, the whole
      TLV MUST be ignored and not forwarded.

   o  Holdtime: The life cycle of the BIER information.  The default
      value is 60s.

   o  BFR-prefix: The BFR-prefix of the node in this sub-domain.  The
      format for this address is given in the Encoded-Unicast address in
      [RFC7761].

   A node may belong to several BIER sub-domains, so it is possible that
   there are multiple BIER information TLVs in the PFM message.

3.3.  BIER MPLS Encapsulation sub-TLV

   In case the nodes in the network support MPLS forwarding, BIER MPLS
   encapsulation sub-TLV can be advertised for a specific bitstring
   length for a certain (MT,subdomain).  This sub-TLV may appear
   multiple times within single BIER information TLV.  The format and
   restriction is the same as the definition in
   [I-D.ietf-bier-isis-extensions] and
   [I-D.ietf-bier-ospf-bier-extensions].




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   The type value of this sub-TLV should be assigned by IANA.  The
   suggestion value is 1.

3.4.  Optional BIER sub-domain BSL conversion sub-TLV

   The format and restriction is the same as the definition in
   [I-D.ietf-bier-isis-extensions] and
   [I-D.ietf-bier-ospf-bier-extensions].  The type value of this sub-TLV
   should be assigned by IANA.  The suggestion value is 2.

4.  Security Considerations

   The security considerations are mainly similar to what is documented
   in [I-D.ietf-pim-source-discovery-bsr].

5.  IANA Considerations

   This document requires the assignment of a new PFM TLV type for the
   BIER information Flooding Mechanism.  IANA is also requested to
   create two sub-TLV types for BIER MPLS encapsulation sub-TLV and BIER
   sub-domain BSL conversion sub-TLV.

6.  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-08 (work in
              progress), September 2017.

   [I-D.ietf-bier-isis-extensions]
              Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang,
              "BIER support via ISIS", draft-ietf-bier-isis-
              extensions-05 (work in progress), July 2017.

   [I-D.ietf-bier-ospf-bier-extensions]
              Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
              Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions
              for BIER", draft-ietf-bier-ospf-bier-extensions-07 (work
              in progress), July 2017.

   [I-D.ietf-pim-source-discovery-bsr]
              Wijnands, I., Venaas, S., Brig, M., and A. Jonasson, "PIM
              flooding mechanism and source discovery", draft-ietf-pim-
              source-discovery-bsr-06 (work in progress), March 2017.






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   [RFC5059]  Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
              "Bootstrap Router (BSR) Mechanism for Protocol Independent
              Multicast (PIM)", RFC 5059, DOI 10.17487/RFC5059, January
              2008, <https://www.rfc-editor.org/info/rfc5059>.

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <https://www.rfc-editor.org/info/rfc7761>.

Authors' Addresses

   Zheng(Sandy) Zhang
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing
   China

   Email: zhang.zheng@zte.com.cn


   BenChong Xu
   ZTE Corporation
   No. 68 Zijinghua Road, Yuhuatai Distinct
   Nanjing
   China

   Email: xu.benchong@zte.com.cn






















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