Bidirectional Forwarding Detection (BFD) for Multi-point Networks and Protocol Independent Multicast - Sparse Mode (PIM-SM) Use Case
draft-mirsky-pim-bfd-p2mp-use-case-00

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PIM Working Group                                              G. Mirsky
Internet-Draft                                                 ZTE Corp.
Updates: 7761 (if approved)                                    J. Xiaoli
Intended status: Standards Track                         ZTE Corporation
Expires: August 19, 2018                               February 15, 2018

 Bidirectional Forwarding Detection (BFD) for Multi-point Networks and
     Protocol Independent Multicast - Sparse Mode (PIM-SM) Use Case
                 draft-mirsky-pim-bfd-p2mp-use-case-00

Abstract

   This document discusses use of Bidirectional Forwarding Detection
   (BFD) for multi-point networks to provide nodes that participate in
   Protocol Independent Multicast - Sparse Mode (PIM-SM) over shared-
   media segment with sub-second convergence of the Designated Router
   and defines the extension to bootstrap point-to-multipoint BFD
   session.  Optional extension to PIM-SM Hello, as defined in RFC 7761,
   also defined in this document.

Status of This Memo

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   This Internet-Draft will expire on August 19, 2018.

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Applicability of p2mp BFD . . . . . . . . . . . . . . . . . .   3
     3.1.  Multipoint BFD Encapsulation  . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [RFC7761] is the current specification of the Protocol Independent
   Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks.
   Confirming implementation of PIM-SM elects a Designated Router (DR)
   on each PIM-SM interface.  When a group of PIM-SM nodes are connected
   to shared-media segment, e.g.  Ethernet, the one elected as DR is to
   act on behalf of directly connected hosts in context of the PIM-SM
   protocol.  Failure of the DR impacts quality of the multicast
   services it provides to directly connected hosts because the default
   failure detection interval for PIM-SM routers is 105 seconds.
   Introduction of Backup DR (BDR), proposed in
   [I-D.ietf-pim-dr-improvement] improves convergence time in the PIM-SM
   over shared-media segment but still depends on long failure detection
   interval.

   Bidirectional Forwarding Detection (BFD) [RFC5880] had been
   originally defined to detect failure of point-to-point (p2p) paths -
   single-hop [RFC5881], multihop [RFC5883].  [I-D.ietf-bfd-multipoint]
   extends [RFC5880] for multipoint and multicast networks, which
   precisely characterizes deployment scenarios for PIM-SM over LAN
   segment.  This document demonstrates how point-to-multipoint (p2mp)
   BFD can enable faster detection of PIM-SM DR and BDR failure and thus
   minimize multicast service disruption.  The document also defines the
   extension to PIM-SM [RFC7761] to bootstrap a PIM-SM router to join in
   p2mp BFD session over shared-media link.

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1.1.  Conventions used in this document

1.1.1.  Terminology

   BFD: Bidirectional Forwarding Detection

   BDR: Backup Designated Router

   DR: Designated Router

   p2mp: Pont-to-Multipoint

   PIM-SM: Protocol Independent Multicast - Sparse Mode

1.1.2.  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.

2.  Problem Statement

   Several PIM-SM routers may be connected over shared-media link, e.g.
   Ethernet.  [RFC7761] does not provide method for fast, e.g. sub-
   second, DR failure detection by other PIM-SM routers on the same
   Ethernet link.  BFD already has many implementations based on HW that
   are capable to support multiple sub-second session concurrently.
   [Editor's note: monitoring of PIM-SM BDR liveliness will be addressed
   in the next update of the draft.]

3.  Applicability of p2mp BFD

   [I-D.ietf-bfd-multipoint] may provide the efficient and scalable
   solution for fast-converging environment that has head-tails
   relationships.  Each such group presents itself as p2mp BFD session
   with its head being the root and other routers being tails of the
   p2mp BFD session.  Figure 1 displays the new BFD Discriminator TLV
   [RFC7761] to bootstrap tail of the p2mp BFD session.

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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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          OptionType           |         OptionLength          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       My  Discriminator                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 1: BFD Discriminator TLV to Bootstrap P2MP BFD session

   where new fields are interpreted as:

      OptionType is value (TBA1) assigned by IANA Section 4 that
      identifies the TLV as BFD Discriminator TLV;

      OptionLength value is always 4

      My Discriminator - My Discriminator value allocated by the root of
      the p2mp BFD session.

   If PIM-SM routers, that support this specification, are configured to
   use p2mp BFD for faster convergence, then the DR MUST create BFD
   session MultipointHead, as defined in [I-D.ietf-bfd-multipoint].
   PIM-SM DR MUST include BFD TLV in its PIM-Hello message.  PIM-SM DR
   periodically transmits BFD control packets.  Source IP address of the
   BFD control packet MUST be the same as the source IP address of the
   PIM-Hello with BFD TLV messages being transmitted by the DR.  The
   values of My Discriminator in the BFD control packet and My
   Discriminator field of the BFD TLV in PIM-Hello, transmitted by the
   PIM-SM DR, MUST be the same.  When non-DR PIM-SM router receives PIM-
   Hello packet from DR with BFD TLV it MAY create p2mp BFD session as
   MultipointTail, as defined in [I-D.ietf-bfd-multipoint], and
   demultiplex p2mp BFD test session based on DR source IP address the
   My Discriminator value value it learned from BFD Discriminator TLV.
   If DR ceased to include BFD TLV in its PIM-Hello message, other PIM-
   SM nodes MUST close corresponding MultipointTail BFD session.

3.1.  Multipoint BFD Encapsulation

   The MultipointHead of p2mp BFD session when transmitting BFD control
   packet:

      MUST set TTL value to 1;

      SHOULD use group address ALL-PIM-ROUTERS ('224.0.0.13' for IPv4
      and 'ff02::d' for IPv6) as destination IP address

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      MAY use network broadcast address for IPv4 or link-local all nodes
      multicast group for IPv6 as destination IP address;

      MUST set destination UDP port value to 3784 when transmitting BFD
      control packets, as defined in [I-D.ietf-bfd-multipoint].

4.  IANA Considerations

   IANA is requested to allocate new OptionType value from PIM Hello
   Options registry according to:

   +-------------+----------------+-------------------+---------------+
   | Value Name  | Length Number  | Name Protocol     | Reference     |
   +-------------+----------------+-------------------+---------------+
   | TBA         | 4              | BFD Discriminator | This document |
   +-------------+----------------+-------------------+---------------+

                  Table 1: BFD Discriminator option type

5.  Security Considerations

   Security considerations discussed in [RFC7761], [RFC5880], and
   [I-D.ietf-bfd-multipoint], apply to this document.

6.  Acknowledgements

   TBD

7.  Normative References

   [I-D.ietf-bfd-multipoint]
              Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for
              Multipoint Networks", draft-ietf-bfd-multipoint-13 (work
              in progress), January 2018.

   [I-D.ietf-pim-dr-improvement]
              Zhang, Z., hu, f., Xu, B., and m. mishra, "PIM DR
              Improvement", draft-ietf-pim-dr-improvement-04 (work in
              progress), December 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

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   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
              DOI 10.17487/RFC5881, June 2010,
              <https://www.rfc-editor.org/info/rfc5881>.

   [RFC5883]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
              June 2010, <https://www.rfc-editor.org/info/rfc5883>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com

   Ji Xiaoli
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: ji.xiaoli@zte.com.cn

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