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Versions: 00 01

PIM Working Group                                            Yisong Liu
Internet Draft                                      Huawei Technologies
Intended status: Standards Track                             M. McBride
Expires: December 20, 2019                                    T. Eckert
                                                              Futurewei
                                                          June 20, 2019


                        PIM Assert Message Packing
                      draft-liu-pim-assert-packing-01


Status of this Memo

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   This Internet-Draft will expire on December 20, 2019.

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Abstract

   In PIM-SM shared LAN networks, there is typically more than one
   upstream router. When duplicate data packets appear on the LAN from
   different routers, assert packets are sent from these routers to
   elect a single forwarder. The PIM assert packets are sent
   periodically to keep the assert state. The PIM assert packet carries
   information about a single multicast source and group, along with the
   metric-preference and metric of the route towards the source or RP.
   This document defines a standard to send and receive multiple
   multicast source and group information in a single PIM assert packet
   in a shared network. This can be particularly helpful when there is
   traffic for a large number of multicast groups.

Table of Contents


   1. Introduction ................................................ 2
      1.1. Requirements Language .................................. 3
      1.2. Terminology ............................................ 3
   2. Use Cases ................................................... 3
      2.1. Enterprise network ..................................... 3
      2.2. Video surveillance ..................................... 4
      2.3. Financial Services ..................................... 4
      2.4. IPTV broadcast video ................................... 4
      2.5. Summary ................................................ 4
   3. Solution .................................................... 5
      3.1. PIM Assert Packing Hello Option ........................ 5
      3.2. PIM Assert Packing Simple Type ......................... 5
      3.3. PIM Assert Packing Aggregation Type .................... 5
   4. Packet Format ............................................... 6
      4.1. PIM Assert Packing Hello Option ........................ 6
      4.2. PIM Assert Simple Packing Format ....................... 7
      4.3. PIM Assert Aggregation Packing Format .................. 8
   5. IANA Considerations ........................................ 11
   6. Security Considerations .................................... 11
   7. References ................................................. 11
      7.1. Normative References .................................. 11
      7.2. Informative References ................................ 11
   8. Acknowledgments ............................................ 12

1. Introduction

   In PIM-SM shared LAN networks, there is typically more than one
   upstream router. When duplicate data packets appear on the LAN, from
   different upstream routers, assert packets are sent from these
   routers to elect a single forwarder according to [RFC7761]. The PIM


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   assert packets are sent periodically to keep the assert state.  The
   PIM assert packet carries information about a single multicast
   source and group, along with the corresponding metric-preference and
   metric of the route towards the source or RP.

   This document defines a standard to send and receive multiple
   multicast source and group information in a single PIM assert packet
   in a shared LAN network. It can efficiently pack multiple PIM assert
   packets into a single message and reduce the processing pressure of
   the PIM routers. This can be particularly helpful when there is
   traffic for a large number of multicast groups.

    1.1. Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

    1.2. Terminology

   RPF: Reverse Path Forwarding

   RP: Rendezvous Point

   SPT: Shortest Path Tree

   RPT: RP Tree

   DR: Designated Router

   BDR: Backup Designated Router

2. Use Cases

   PIM Assert will happen in many services where multicast is used and
   not limited to the examples described below.

    2.1. Enterprise network

   When an Enterprise network is connected through a layer-2 network,
   the intra-enterprise runs layer-3 PIM multicast. The different sites
   of the enterprise are equivalent to the PIM connection through the
   shared LAN network. Depending upon the locations and amount of
   groups there could be many asserts on the first hop routers.





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    2.2. Video surveillance

   Video surveillance deployments have migrated from analog based
   systems to IP-based systems oftentimes using multicast. In the
   shared LAN network deployments, when there are many cameras
   streaming to many groups there may be issues with many asserts on
   first hop routers.

    2.3. Financial Services

   Financial services extensively rely on IP Multicast to deliver stock
   market data and its derivatives, and current multicast solution PIM
   is usually deployed. As the number of multicast flows grows, there
   are many stock data with many groups may result in many PIM asserts
   on a shared LAN network from publisher to the subscribers.

    2.4. IPTV broadcast video

   PIM DR and BDR deployments are often used in host-side network for
   IPTV broadcast video services. Host-side access network failure
   scenario may be benefitted by assert packing when many groups are
   being used. According to [RFC7761] the DR will be elected to forward
   multicast traffic in the shared access network. When the DR recovers
   from a failure, the original DR starts to send traffic, and the
   current DR is still forwarding traffic. In the situation multicast
   traffic duplication maybe happen in the shared access network and
   can trigger the assert progress.

    2.5. Summary

   In the above scenarios, the existence of PIM assert process depends
   mainly on the network topology. As long as there is a layer 2
   network between PIM neighbors, there may be multiple upstream
   routers, which can cause duplicate multicast traffic to be forwarded
   and assert process to occur.

   Moreover as the multicast services become widely deployed, the
   number of multicast entries increases, and a large number of assert
   messages may be sent in a very short period when multicast data
   packets trigger PIM assert process in the shared LAN networks. The
   PIM routers need to process a large number of PIM assert small
   packets in a very short time. As a result, the device load is very
   large. The assert packet may not be processed in time or even is
   discarded, thus extending the time of traffic duplication in the
   network.

   Additionally, future backhaul, or fronthaul, networks may want to
   connect L3 across an L2 underlay supporting Time Sensitive Networks
   (TSN). The infrastructure may run DetNet over TSN. These transit L2


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   LANs would have multiple upstreams and downstreams. This document is
   taking a proactive approach to prevention of possible future assert
   issues in these types of environments.

3. Solution

   The change to the PIM assert includes two elements: the PIM assert
   packing hello option and the PIM assert packing method.

   There is no change required to the PIM assert state machine.
   Basically a PIM router can now be the assert winner or loser for
   multiple packed (S, G)'s in a single assert packet instead of one
   (S, G) assert at a time. An assert winner is now responsible for
   forwarding traffic from multiple (S, G)'s out of a particular
   interface based upon the multiple (S, G)'s packed in a single
   assert.

    3.1. PIM Assert Packing Hello Option

   The newly defined Hello Option is used by a router to negotiate the
   assert packet packing capability. It can only be used when all PIM
   routers, in the same shared LAN network, support this capability.

   This document defines two packing methods. One method is a simple
   merge of the original messages and the other is to extract the
   common message fields for aggregation.

    3.2. PIM Assert Packing Simple Type

   In this type of packing, the original assert message body is used as
   a record. The newly defined assert message can carry multiple assert
   records and identify the number of records.

   This packing method is simply extended from the original assert
   packet, but, because the multicast service deployment often uses a
   small number of sources and RPs, there may be a large number of
   assert records with the same metric preference or route metric
   field, which would waste the payload of the transmitted message.

    3.3. PIM Assert Packing Aggregation Type

   When the source or RP addresses, in the actual deployment of the
   multicast service, are very few, this type of packing will combine
   the records related to the source address or RP address in the
   assert message.

   * A (S, G) assert only can contain one SPT (S, G) entry, so it can
   be aggregated according to the same source address, and then all SPT



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   (S, G) entries corresponding to the same source address are merged
   into one assert record.

   * A (*, G) assert may contain a (*, G) entry or a RPT (S, G) entry,
   and both entry types actually depend on the route to the RP. So it
   can be aggregated further according to the same RP address, and then
   all (*, G) and RPT (S, G) entries corresponding to the same RP
   address are merged into one assert record.

   This method can optimize the payload of the transmitted message by
   merging the same field content, but will add the complexity of the
   packet encapsulation and parsing.



4. Packet Format

   This section describes the format of new PIM messages introduced by
   this document.  The messages follow the same transmission order as
   the messages defined in [RFC7761]



    4.1. PIM Assert Packing Hello Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      OptionType = TBD         |      OptionLength = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Packing_Type |
      +-+-+-+-+-+-+-+-+


   - OptionType: TBD

   - OptionLength: 1

   - Packing_Type: The specific packing mode is determined by the value
   of this field:

     1: indicates simple packing type as described in section 2.2

     2: indicates aggregating packing type as described in section 2.3

     3-255: reserved for future





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    4.2. PIM Assert Simple Packing Format

       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  |SubType| Rsvd  |           Checksum            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Reserved            |  Number of Assert Records (M) |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Assert Record [1]                      .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Assert Record [2]                      .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               .                               |
      .                               .                               .
      |                               .                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Assert Record [M]                      .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   PIM Version, Reserved, Checksum

       Same as [RFC7761] Section 4.9.6

   Type

       The new Assert Type and SubType values TBD

   Number of Assert Records

       The number of packed assert records. A record consists of a
       single assert message body.





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   The format of each record is the same as the PIM assert message body
   of section 4.9.6 in [RFC7761].

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Group Address (Encoded-Group format)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Source Address (Encoded-Unicast format)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |R|                      Metric Preference                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Metric                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    4.3. PIM Assert Aggregation Packing Format

   This method also extends PIM assert packets to carry multiple
   records. The specific assert packet format is the same as section
   4.2, but the records are divided into two types.

   The (S, G) assert records are organized by the same source address,
   and the specific message format is:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Source Address (Encoded-Unicast format)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|                      Metric Preference                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Metric                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Number of Groups (N)   |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Group Address 1 (Encoded-Group format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Group Address 2 (Encoded-Group format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             .                                 |
      |                             .                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Group Address N (Encoded-Group format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Source Address, Metric Preference, Metric and Reserved


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       Same as [RFC7761] Section 4.9.6, but the source address MUST NOT
       be set to zero.

   Number of Groups

       The number of group addresses corresponding to the source address
       field in the (S, G) assert record.

   Group Address

       Same as [RFC7761] Section 4.9.6, but there are multiple group
       addresses in the (S, G) assert record

   The (*, G) assert records are organized in the same RP address and
   are divided into two levels of TLVs. The first level is the group
   record of the same RP address, and the second level is the source
   record of the same multicast group address, including (*, G) and RPT
   (S, G), and the specific message format is:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             RP Address (Encoded-Unicast format)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|                      Metric Preference                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Metric                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Number of Group Records(O)  |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Group Record [1]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Group Record [2]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               .                               |
      .                               .                               .
      |                               .                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .


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      .                        Group Record [O]                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   RP Address

       The address of RP corresponding to all of the contained group
       records. The format for this address is given in the encoded
       unicast address in [RFC7761] Section 4.9.1

   Metric Preference, Metric and Reserved

       Same as [RFC7761] Section 4.9.6

   Number of Group Records

       The number of packed group records. A record consists of a group
       address and a source address list.

   The format of each group record is:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Group Address (Encoded-Group format)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Number of Sources (P)  |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Source Address 1 (Encoded-Unicast format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Source Address 2 (Encoded-Unicast format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             .                                 |
      |                             .                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Source Address P (Encoded-Unicast format)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Group Address and Reserved

       Same as [RFC7761] Section 4.9.6

   Number of Sources



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       The number of source addresses corresponding to the group address
       field in the group record.

   Source Address

       Same as [RFC7761] Section 4.9.6, but there are multiple source
       addresses in the group record.



5. IANA Considerations

   This document requests IANA to assign a registry for PIM assert
   packing Hello Option in the PIM-Hello Options and new PIM assert
   packet type and subtype. The assignment is requested permanent for
   IANA when this document is published as an RFC. The string TBD
   should be replaced by the assigned values accordingly.

6. Security Considerations

   For general PIM-SM protocol Security Considerations, see [RFC7761].

   TBD

7. References

    7.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas,
             I.,Parekh, R., Zhang, Z., and L. Zheng, "Protocol
             IndependentMulticast - Sparse Mode (PIM-SM): Protocol
             Specification(Revised)", RFC 7761, March 2016

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, May 2017



    7.2. Informative References

   TBD






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8. Acknowledgments

   The authors would like to thank the following for their valuable
   contributions of this document:

   TBD












































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   Authors' Addresses

   Yisong Liu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: liuyisong@huawei.com


   Mike McBride
   Futurewei
   2330 Central Expressway
   Santa Clara, CA 95055
   USA

   Email: michael.mcbride@futurewei.com



   Toerless Eckert
   Futurewei
   2330 Central Expy
   Santa Clara  95050
   USA

   Email: tte+ietf@cs.fau.de






















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