BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP
draft-mirsky-mpls-p2mp-bfd-06

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MPLS Working Group                                             G. Mirsky
Internet-Draft                                                 ZTE Corp.
Intended status: Standards Track                         January 5, 2019
Expires: July 9, 2019

     BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP
                     draft-mirsky-mpls-p2mp-bfd-06

Abstract

   This document describes procedures for using Bidirectional Forwarding
   Detection (BFD) for multipoint networks to detect data plane failures
   in Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp)
   Label Switched Paths (LSPs).  It also describes the applicability of
   LSP Ping, as in-band, and the control plane, as out-band, solutions
   to bootstrap a BFD session in this environment.

Status of This Memo

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  Multipoint BFD Encapsulation  . . . . . . . . . . . . . . . .   3
     3.1.  IP Encapsulation of Multipoint BFD  . . . . . . . . . . .   3
     3.2.  Non-IP Encapsulation of Multipoint BFD  . . . . . . . . .   4
   4.  Bootstrapping Multipoint BFD  . . . . . . . . . . . . . . . .   4
     4.1.  LSP Ping  . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Control Plane . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Source MEP ID IP Address Type . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [I-D.ietf-bfd-multipoint] defines a method of using Bidirectional
   Detection (BFD) [RFC5880] to monitor and detect unicast failures
   between the sender (head) and one or more receivers (tails) in
   multipoint or multicast networks.  This document describes procedures
   for using such mode of BFD protocol to detect data plane failures in
   Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp) Label
   Switched Paths (LSPs).  The document also describes the applicability
   of out-band solutions to bootstrap a BFD session in this environment.

2.  Conventions used in this document

2.1.  Terminology

   MPLS: Multiprotocol Label Switching

   LSP: Label Switched Path

   BFD: Bidirectional Forwarding Detection

   p2mp: Point-to-Multipoint

   FEC: Forwarding Equivalence Class

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   G-ACh: Generic Associated Channel

   ACH: Associated Channel Header

   GAL: G-ACh Label

2.2.  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.

3.  Multipoint BFD Encapsulation

   [I-D.ietf-bfd-multipoint] defines how the tail of multipoint BFD
   session demultiplexes received BFD control packet when Your
   Discriminator is not set, i.e., equals zero.  Because
   [I-D.ietf-bfd-multipoint] uses BFD in Demand mode from the very start
   of the p2mp BFD session, the head of BFD multipoint session transmits
   all BFD control packets with Your Discriminator set to zero.  As a
   result, a tail cannot demultiplex BFD sessions using Your
   Discriminator, as defined in [RFC5880].  [I-D.ietf-bfd-multipoint]
   requires that to demultiplex BFD sessions the tail uses the source IP
   address, My Discriminator and the identity of the multipoint tree
   from which the Multipoint BFD Control packet was received.  The
   identification of the multipoint tree MAY be provided by the p2mp
   MPLS LSP label in case of inclusive p-tree or upstream assigned label
   in case of aggregate p-tree.  If the BFD control packet is
   encapsulated in IP/UDP, then the source IP address MUST be used to
   demultiplex the received BFD control packet as described in
   Section 3.1.  The non-IP encapsulation case is described in
   Section 3.2.

3.1.  IP Encapsulation of Multipoint BFD

   [I-D.ietf-bfd-multipoint] defines IP/UDP encapsulation for multipoint
   BFD over p2mp MPLS LSP:

      UDP destination port MUST be set to 3784;

      destination IP address MUST be from the 127/8 range for IPv4 and
      from the 0:0:0:0:0:FFFF:7F00/104 range for IPv6;

   This specification further clarifies that:

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      if multiple alternative paths for the given p2mp LSP Forwarding
      Equivalence Class (FEC) exist, the MultipointHead SHOULD use
      Entropy Label [RFC6790] used for LSP Ping [RFC8029] to exercise
      that particular alternative path;

      or the MultipointHead MAY use the IP address discovered by LSP
      Ping traceroute [RFC8029] as the destination IP address to
      possibly exercise that particular alternate path.

3.2.  Non-IP Encapsulation of Multipoint BFD

   In some environments, the overhead of extra IP/UDP encapsulations may
   be considered as overburden and make using more compact G-ACh
   encapsulation attractive.  Non-IP encapsulation for multipoint BFD
   over p2mp MPLS LSP MUST use Generic Associated Channel (G-ACh) Label
   (GAL) [RFC5586] at the bottom of the label stack followed by
   Associated Channel Header (ACH).  Channel Type field in ACH MUST be
   set to MPLS-TP CV value (0x0023) [RFC6428].  To provide the identity
   of the MultipointHead for the particular multipoint BFD session this
   document defines new Source MEP ID IP Address type (TBA1) in
   Section 6.1.  If the Length value is 4, then the Value field contains
   an IPv4 address.  If the Length value is 16, then the Value field
   contains an IPv6 address.  Any other value of the Length field MUST
   be considered as an error, and the BFD control packet MUST be
   discarded.

4.  Bootstrapping Multipoint BFD

4.1.  LSP Ping

   LSP Ping is the part of on-demand OAM toolset to detect and localize
   defects in the data plane, and verify the control plane against the
   data plane by ensuring that the LSP is mapped to the same FEC, at the
   egress, as the ingress.

   LSP Ping, as defined in [RFC6425], MAY be used to bootstrap
   MultipointTail.  If the LSP Ping used, it MUST include the Target FEC
   TLV and the BFD Discriminator TLV defined in [RFC5884].  The Target
   FEC TLV MUST use sub-TLVs defined in Section 3.1 [RFC6425].  It is
   RECOMMENDED setting the value of Reply Mode field to "Do not reply"
   [RFC8029] for the LSP Ping to bootstrap MultipointTail of the p2mp
   BFD session.  A MaultipointTail that receives the LSP Ping that
   includes the BFD Discriminator TLV:

   o  MUST validate the LSP Ping;

   o  MUST associate the received BFD Discriminator value with the p2mp
      LSP;

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   o  MUST create p2mp BFD session and set bfd.SessionType =
      MultipointTail as described in [I-D.ietf-bfd-multipoint];

   o  MUST use the source IP address of LSP Ping, the value of BFD
      Discriminator from the BFD Discriminator TLV, and the identity of
      the p2mp LSP to properly demultiplex BFD sessions.

   Besides bootstrapping a BFD session over a p2mp LSP, LSP Ping SHOULD
   be used to verify the control plane against the data plane
   periodically by checking that the p2mp LSP is mapped to the same FEC
   at the MultipointHead and all active MultipointTails.  The rate of
   generation of these LSP Ping Echo request messages SHOULD be
   significantly less than the rate of generation of the BFD Control
   packets because LSP Ping requires more processing to validate the
   consistency between the data plane and the control plane.  An
   implementation MAY provide configuration options to control the rate
   of generation of the periodic LSP Ping Echo request messages.

4.2.  Control Plane

   BGP-BFD Attribute [I-D.ietf-bess-mvpn-fast-failover] MAY be used to
   bootstrap multipoint BFD session on a tail.

5.  Security Considerations

   This document does not introduce new security aspects but inherits
   all security considerations from [RFC5880], [RFC5884], [RFC7726],
   [I-D.ietf-bfd-multipoint], [RFC8029], and [RFC6425].

   Also, BFD for p2mp MPLS LSP MUST follow the requirements listed in
   section 4.1 [RFC4687] to avoid congestion in the control plane or the
   data plane caused by the rate of generating BFD control packets.  An
   operator SHOULD consider the amount of extra traffic generated by
   p2mp BFD when selecting the interval at which the MultipointHead will
   transmit BFD control packets.  Also, the operator MAY consider the
   size of the packet the MultipointHead transmits periodically as using
   IP/UDP encapsulation adds up to 28 octets, which is more than 50% of
   BFD control packet length, comparing to G-ACh encapsulation.

6.  IANA Considerations

6.1.  Source MEP ID IP Address Type

   IANA is required to allocate value (TBD) for the Source MEP ID IP
   Address type from the "CC/CV MEP-ID TLV" registry which is under the
   "Pseudowire Associated Channel Types" registry.

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                  +-------+-------------+---------------+
                  | Value | Description | Reference     |
                  +-------+-------------+---------------+
                  | TBA1  |  IP Address | This document |
                  +-------+-------------+---------------+

                Table 1: Source MEP ID IP Address TLV Type

7.  Acknowledgements

   The author sincerely appreciates the comments received from Andrew
   Malis.

8.  References

8.1.  Normative References

   [I-D.ietf-bess-mvpn-fast-failover]
              Morin, T., Kebler, R., and G. Mirsky, "Multicast VPN fast
              upstream failover", draft-ietf-bess-mvpn-fast-failover-04
              (work in progress), November 2018.

   [I-D.ietf-bfd-multipoint]
              Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for
              Multipoint Networks", draft-ietf-bfd-multipoint-19 (work
              in progress), December 2018.

   [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>.

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586,
              DOI 10.17487/RFC5586, June 2009,
              <https://www.rfc-editor.org/info/rfc5586>.

   [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>.

   [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "Bidirectional Forwarding Detection (BFD) for MPLS Label
              Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
              June 2010, <https://www.rfc-editor.org/info/rfc5884>.

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   [RFC6425]  Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
              Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
              Failures in Point-to-Multipoint MPLS - Extensions to LSP
              Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011,
              <https://www.rfc-editor.org/info/rfc6425>.

   [RFC6428]  Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
              "Proactive Connectivity Verification, Continuity Check,
              and Remote Defect Indication for the MPLS Transport
              Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011,
              <https://www.rfc-editor.org/info/rfc6428>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

   [RFC7726]  Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
              Aldrin, "Clarifying Procedures for Establishing BFD
              Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
              DOI 10.17487/RFC7726, January 2016,
              <https://www.rfc-editor.org/info/rfc7726>.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,
              <https://www.rfc-editor.org/info/rfc8029>.

   [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>.

8.2.  Informative References

   [RFC4687]  Yasukawa, S., Farrel, A., King, D., and T. Nadeau,
              "Operations and Management (OAM) Requirements for Point-
              to-Multipoint MPLS Networks", RFC 4687,
              DOI 10.17487/RFC4687, September 2006,
              <https://www.rfc-editor.org/info/rfc4687>.

Author's Address

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com

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