Path Autogeneration in BIER
draft-zhang-bier-path-autogeneration-00

BIER WG                                                         Z. Zhang
Internet-Draft                                                     B. Wu
Intended status: Standards Track                                 C. Wang
Expires: June 23, 2016                                   ZTE Corporation
                                                       December 21, 2015

                      Path Autogeneration in BIER
                draft-zhang-bier-path-autogeneration-00

Abstract

   [I-D.ietf-bier-architecture] BIER introduces a method for multicast
   flow forwarding, without storing states in every node along the
   multicast path.  This document introduces a method of establishing
   multicast path automatically.

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   This Internet-Draft will expire on June 23, 2016.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Packet Formats . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  BFIR procedure . . . . . . . . . . . . . . . . . . . . . .  6
       3.1.1.  Sending the path packets . . . . . . . . . . . . . . .  6
       3.1.2.  Withdraw Nodes . . . . . . . . . . . . . . . . . . . .  6
     3.2.  BFR and BFER . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   5.  IANA considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Normative References . . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11

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1.  Introduction

   [I-D.ietf-bier-architecture] BIER is a technology of multicast flow
   forwarding.  [I-D.ietf-bier-mpls-encapsulation] introduces a way to
   use mpls in BIER forwarding.  This document introduces a method of
   establishing multicast path automatically.

   Upstream-assigned label is used in this document.  Associate with the
   label indicated the BFIR, the two labels compose the keywords for
   multicast flow forwarding.  Every node along the multicast path used
   the two labels to forward multicast flow without label changing.
   Obviously, the nodes along the path establish the mpls forwarding
   table, when they receive the packet which include the label
   combination and the path specification.

   BFIR sends the first packet with label combination and path
   specification, every node along the path build the mpls forwarding
   table, and forward the packet to next node according to the path
   specification.  If there is already a mpls forwarding item which has
   the same label combination, the node combines the next-hop in the
   packet to the existed forwarding item.

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2.  Packet Formats

   This document introduces a new TLV that is carried by the BIER
   packet, and this TLV is composed by the nodes in the multicast path.
   There is a flag in the BIER header indicates that a path TLV is be
   carried.  One of the reserved flag may be used to signal this.

           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
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |0 1 0 1|  Ver  |  Len  |              Entropy                  |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                BitString  (first 32 bits)                     ~
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          ~                                                               ~
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          ~                BitString  (last 32 bits)                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |OAM|     Reserved     1| Proto |            BFIR-id            |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             Figure 1 BIER Header

   The path list is composed by nodes along the multicast path.  The
   multicast path is decided by BFIR in advance through PCE or other
   calculations or configurations.

           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             |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                           BFIR label                          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                     Upstream-assigned label                   |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |             Id                 |              Id              |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          ~                                                               ~
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          ~             Id                 |           BFER-id            |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                           Figure 2 Path Specification

   o  Type TBD, indicate that there is a path TLV.

   o  Length The length of the TLV.

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   o  BFIR label The label of BFIR.

   o  Upstream-assigned label The label that is assigned by BFIR for the
      specific multicast flow.

   o  Id The node BFR-id or the link id along the multicast path.  They
      are carried by the packets in order.

   o  BFER-id The BFR-id of BFER.

   Like the ingress replication, BFIR repeats BIER packets several times
   according to every BFER of the multicast flow.  And then BFIR sends
   the BIER packets with the two labels.

   The withdraw packet is the same format with the path packet.  But the
   type should be another type, and the last node that is carried by the
   withdraw packet is the canceled node.

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3.  Procedures

3.1.  BFIR procedure

3.1.1.  Sending the path packets

   When BFIR gains the BFER information of a specific multicast flow,
   BFIR encapsulates the receiving flow with the path list, and sends to
   every BFER individually.Particularly, the encapsulated packet that is
   sent by BFIR includes the label combination.

                       B-------- C ------ D --------
                       |         |        |        |
                       A ------- F ------ G ------ H
                       |         |        |        |
                       --------- K ------ L -------M
                            Figure 3 An Example

   For example, in figure 3, A is BFIR for a specific multicast flow.
   And D, H, M are BFER.  According the PCE calculation, the multicast
   flow should be sent along these paths: A-F-G-D/H, A-K-L-M.  So A
   encapsulates the flow with the two label combination and makes three
   copies, and then sends to D/H/M separately.  In node A, there is one
   mpls label forwarding item which the ingress label is the two labels
   combination, and the next-hops are F and K with the same two label
   out.  A encapsulates the formal multicast flow with the two labels
   and forwards to next hops.

   For the stability consideration, BFIR sends the path packets every
   once in a while.  The interval may be 30 minutes.  And when new BFER
   joined, BFIR sends the path packets to the new BFER immediately.

3.1.2.  Withdraw Nodes

   According to the PCE calculation, some existed nodes in the path may
   be canceled.  BFIR sends the withdraw path packet which the last node
   is the canceled node.

   For example in figure 1, if the bandwidth in the network is changed,
   the multicast flow should be forwarded along these ways: A-B-C-D-H,
   A-K-L-M.  The specific multicast flow will not pass by the node F and
   G anymore.  Except A sending a new path packet along the path
   A-B-C-D-H, A also sends two withdraw path packets to node F and G.

3.2.  BFR and BFER

   When BFR and BFER receive the path packets, they build an item in the
   mpls forwarding table according to the label combination that is

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   carried by the packets.  If there is an item already in the
   forwarding table, the nodes should add the next-hop which is the next
   node in the path packet.

   When BFR and BFER receive the withdraw path packets which indicate
   that they should be canceled, the BFR and BFER delete the mpls
   forwarding item which line with the label combination.  If the middle
   node finds that the next node that along the path is the canceled
   node, the middle node deletes the next-hop in the mpls forwarding
   item.  If there is no next-hop in the mpls forwarding item, the node
   deletes the mpls item in the mpls forwarding table.

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4.  Security Considerations

   There should be some common security methods to guarantee the
   validation of path packets.

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5.  IANA considerations

   IANA is requested to allocate types in TLVs of BIER path packets.

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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-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-02 (work in progress),
              August 2015.

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Authors' Addresses

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

   Email: zhang.zheng@zte.com.cn

   Bo Wu
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing,
   China

   Email: wu.bo@zte.com.cn

   Cui(Linda) Wang
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing,
   China

   Email: wang.cui1@zte.com.cn

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