Bidirectional Forwarding Detection (BFD) in Segment Routing Networks Using MPLS Dataplane
draft-mirsky-spring-bfd-10

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SPRING Working Group                                           G. Mirsky
Internet-Draft                                                 ZTE Corp.
Intended status: Standards Track                             J. Tantsura
Expires: October 28, 2020                                   Apstra, Inc.
                                                           I. Varlashkin
                                                                  Google
                                                                 M. Chen
                                                                  Huawei
                                                              J. Wenying
                                                                    CMCC
                                                          April 26, 2020

  Bidirectional Forwarding Detection (BFD) in Segment Routing Networks
                          Using MPLS Dataplane
                       draft-mirsky-spring-bfd-10

Abstract

   Segment Routing (SR) architecture leverages the paradigm of source
   routing.  It can be realized in the Multiprotocol Label Switching
   (MPLS) network without any change to the data plane.  A segment is
   encoded as an MPLS label, and an ordered list of segments is encoded
   as a stack of labels.  Bidirectional Forwarding Detection (BFD) is
   expected to monitor any existing path between systems.  This document
   defines how to use Label Switched Path Ping to bootstrap a BFD
   session, control an SR Policy in the reverse direction of the SR-MPLS
   tunnel, and applicability of BFD Demand mode in the SR-MPLS domain.
   Also, the document describes the use of BFD Echo with BFD Control
   packet payload.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on October 28, 2020.

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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  Bootstrapping BFD Session over Segment Routed Tunnel with
       MPLS Data Plane . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel  . .   5
   4.  Use Non-FEC Path TLV  . . . . . . . . . . . . . . . . . . . .   5
   5.  BFD Reverse Path TLV over Segment Routed MPLS Tunnel with
       Dynamic Control Plane . . . . . . . . . . . . . . . . . . . .   7
   6.  Applicability of BFD Demand Mode in SR-MPLS Domain  . . . . .   7
   7.  Using BFD to Monitor Point-to-Multipoint SR Policy  . . . . .   7
   8.  Use of Echo BFD in SR-MPLS  . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Non-FEC Path TLV  . . . . . . . . . . . . . . . . . . . .   8
     9.2.  Return Code . . . . . . . . . . . . . . . . . . . . . . .   9
   10. Implementation Status . . . . . . . . . . . . . . . . . . . .  10
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  11
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     14.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   [RFC5880], [RFC5881], and [RFC5883] defined the operation of
   Bidirectional Forwarding Detection (BFD) protocol between the two
   systems over IP networks.  [RFC5884] and [RFC7726] set rules for
   using BFD Asynchronous mode over point-to-point (p2p) Multiprotocol

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   Label Switching (MPLS) Label Switched Path (LSP).  These latter
   standards implicitly assume that the remote BFD system, which is at
   the egress Label Edge Router (LER), will use the shortest path route
   regardless of the path the BFD system at the ingress LER uses to send
   BFD Control packets towards it.  Throughout this document, references
   to ingress LER and egress LER are used, respectively, as a shortened
   version of the "BFD system at the ingress/egress LER".

   This document defines the use of LSP Ping for Segment Routing
   networks over MPLS data plane [RFC8287] to bootstrap and control path
   of a BFD session from the egress to ingress LER using Segment Routing
   tunnel with MPLS data plane (SR-MPLS).

1.1.  Conventions

1.1.1.  Terminology

   BFD: Bidirectional Forwarding Detection

   BSID: Binding Segment Identifier

   FEC: Forwarding Equivalence Class

   MPLS: Multiprotocol Label Switching

   SR-MPLS Segment Routing with MPLS data plane

   LSP: Label Switched Path

   LER Label Edge Router

   p2p Point-to-point

   p2mp Point-to-multipoint

   SID Segment Identifier

   SR Segment Routing

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.

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2.  Bootstrapping BFD Session over Segment Routed Tunnel with MPLS Data
    Plane

   Use of an LSP Ping to bootstrap BFD over MPLS LSP is required, as
   documented in [RFC5884], to establish an association between a fault
   detection message, i.e., BFD Control message, and the Forwarding
   Equivalency Class (FEC) of a single label stack LSP in case of
   Penultimate Hop Popping or when the egress LER distributes the
   Explicit NULL label to the penultimate hop router.  The Explicit NULL
   label is not advertised as a Segment Identifier (SID) by an SR node
   but, as demonstrated in section 3.1 [RFC8660] if the operation at the
   penultimate hop is NEXT; then the egress SR node will receive an IP
   encapsulated packet.  Thus the conclusion is that LSP Ping MUST be
   used to bootstrap a BFD session in an SR-MPLS domain if there are no
   other means to bootstrap the BFD session, e.g., using an extension to
   a dynamic routing protocol as described in
   [I-D.ietf-bess-mvpn-fast-failover] and
   [I-D.ietf-pim-bfd-p2mp-use-case].

   As demonstrated in [RFC8287], the introduction of Segment Routing
   network domains with an MPLS data plane requires three new sub-TLVs
   that MAY be used with Target FEC TLV.  Section 6.1 addresses the use
   of the new sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute.
   For the case of LSP ping, the [RFC8287] states that:

      The initiator, i.e., ingress LER, MUST include FEC(s)
      corresponding to the destination segment.

      The initiator MAY include FECs corresponding to some or all of
      segments imposed in the label stack by the ingress LER to
      communicate the segments traversed.

   It has been noted in [RFC5884] that a BFD session monitors for
   defects particular <MPLS LSP, FEC> tuple.  [RFC7726] clarified how to
   establish and operate multiple BFD sessions for the same <MPLS LSP,
   FEC> tuple.  Because only the ingress LER is aware of the SR-based
   explicit route, the egress LER can associate the LSP ping with BFD
   Discriminator TLV with only one of the FECs it advertised for the
   particular segment.  Thus this document clarifies that:

      When LSP Ping is used to bootstrapping a BFD session for SR-MPLS
      tunnel the FEC corresponding to the segment to be associated with
      the BFD session MUST be as the very last sub-TLV in the Target FEC
      TLV.

   If the target segment is an anycast prefix segment
   ([I-D.ietf-spring-mpls-anycast-segments]) the corresponding Anycast
   SID MUST be included in the Target TLV as the very last sub-TLV.

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   Also, for BFD Control packet the ingress SR node MUST use precisely
   the same label stack encapsulation, especially Entropy Label
   ([RFC6790]), as for the LSP ping with the BFD Discriminator TLV that
   bootstrapped the BFD session.  Other operational aspects of using BFD
   to monitor the continuity of the path to the particular Anycast SID,
   advertised by a group of SR-MPLS capable nodes, will be considered in
   the future versions of the document.

   Encapsulation of a BFD Control packet in Segment Routing network with
   MPLS data plane MUST follow Section 7 [RFC5884] when the IP/UDP
   header used and MUST follow Section 3.4 [RFC6428] without IP/UDP
   header being used.

3.  Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel

   For BFD over MPLS LSP case, per [RFC5884], egress LER MAY send BFD
   Control packet to the ingress LER either over IP network or an MPLS
   LSP.  Similarly, for the case of BFD over p2p SR-MPLS tunnel, the
   egress LER MAY route BFD Control packet over the IP network, as
   described in [RFC5883], or transmit over a segment tunnel, as
   described in Section 7 [RFC5884].  In some cases, there may be a need
   to direct egress LER to use a specific path for the reverse direction
   of the BFD session by using the BFD Reverse Path TLV and following
   all procedures as defined in [I-D.ietf-mpls-bfd-directed].

4.  Use Non-FEC Path TLV

   For the case of MPLS data plane, Segment Routing Architecture
   [RFC8402] explains that "a segment is encoded as an MPLS label.  An
   ordered list of segments is encoded as a stack of labels."

   This document defines a new optional Non-FEC Path TLV.  The format of
   the Non-FEC Path TLV is presented in Figure 1

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Non-FEC Path TLV Type      |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                          Non-FEC Path                         ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Non-FEC Path TLV Format

   Non-FEC Path TLV Type is two octets in length and has a value of TBD1
   (to be assigned by IANA as requested in Section 9.1).

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   Length field is two octets long and defines the length in octets of
   the Non-FEC Path field.

   Non-FEC Path field contains a sub-TLV.  Any Non-FEC Path sub-TLV
   (defined in this document or to be defined in the future) for Non-FEC
   Path TLV type MAY be used in this field.  None or one sub-TLV MAY be
   included in the Non-FEC Path TLV.  If no sub-TLV has been found in
   the Non-FEC Path TLV, the egress LER MUST revert to using the reverse
   path selected based on its local policy.  If there is more than one
   sub-TLV, then the Return Code in echo reply MUST be set to value TBD3
   "Too Many TLVs Detected" (to be assigned by IANA as requested in
   Table 4).

   Non-FEC Path TLV MAY be used to specify the reverse path of the BFD
   session identified in the BFD Discriminator TLV.  If the Non-FEC Path
   TLV is present in the echo request message the BFD Discriminator TLV
   MUST be present as well.  If the BFD Discriminator TLV is absent when
   the Non-FEC Path TLV is included, then it MUST be treated as
   malformed Echo Request, as described in [RFC8029].

   This document defines the Segment Routing MPLS Tunnel sub-TLV that
   MAY be used with the Non-FEC Path TLV.  The format of the sub-TLV is
   presented in Figure 2.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  SR MPLS Tunnel sub-TLV Type  |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   SID Entry 1 (Top of Stack)                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           SID Entry 2                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   SID Entry N (Bottom of Stack)               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: Segment Routing MPLS Tunnel sub-TLV

   The Segment Routing MPLS Tunnel sub-TLV Type is two octets in length,
   and has a value of TBD2 (to be assigned by IANA as requested in
   Section 9.1).

   The egress LER MUST use the Value field as label stack for BFD
   Control packets for the BFD session identified by the source IP

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   address of the MPLS LSP Ping packet and the value in the BFD
   Discriminator TLV.  Label Entries MUST be in network order.

5.  BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic
    Control Plane

   When Segment Routed domain with MPLS data plane uses distributed
   tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs
   defined in [RFC8287].

6.  Applicability of BFD Demand Mode in SR-MPLS Domain

   [I-D.mirsky-bfd-mpls-demand] defines how Demand mode of BFD,
   specified in sections 6.6 and 6.18.4 of [RFC5880], can be used to
   monitor uni-directional MPLS LSP.  Similar procedures can be
   following in SR-MPLS to monitor uni-directional SR tunnels:

   o  an ingress SR node bootstraps BFD session over SR-MPLS in Async
      BFD mode;

   o  once BFD session is Up, the ingress SR node switches the egress
      LER into the Demand mode by setting D field in BFD Control packet
      it transmits;

   o  if the egress LER detects the failure of the BFD session, it sends
      its BFD Control packet to the ingress SR node over the IP network
      with a Poll sequence;

   o  if the ingress SR node receives a BFD Control packet from the
      remote node in a Demand mode with Poll sequence and Diag field
      indicating the failure, the ingress SR node transmits BFD Control
      packet with Final over IP and switches the BFD over SR-MPLS back
      into Async mode, sending BFD Control packets one per second.

7.  Using BFD to Monitor Point-to-Multipoint SR Policy

   [I-D.voyer-spring-sr-p2mp-policy] defined variants of SR Policy to
   deliver point-to-multipoint (p2mp) services.  For the given P2MP
   segment [RFC8562] can be used if, for example, leaves have an
   alternative source of the multicast service flow to select.  In such
   a scenario, a leaf may switch to using the alternative flow after
   p2mp BFD detects the failure in the working multicast path.  For
   scenarios where it is required for the root to monitor the state of
   the multicast tree [RFC8563] can be used.  The root may use the
   detection of the failure of the multicast tree to the particular leaf
   to restore the path for that leaf or re-instantiate the whole
   multicast tree.

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   An essential part of using p2mp BFD is the bootstrapping the BFD
   session at all the leaves.  The root, acting as the MultipointHead,
   MAY use LSP Ping with the BFD Discriminator TLV.  Alternatively,
   extensions to routing protocols, e.g., BGP, or management plane,
   e.g., PCEP, MAY be used to associate the particular P2MP segment with
   MultipointHead's Discriminator.  Extensions for routing protocols and
   management plane are for further study.

8.  Use of Echo BFD in SR-MPLS

   Echo-BFD [RFC5880] can be used to monitor an SR Policy between the
   local and the remote BFD peers.  As defined in [RFC5880], the remote
   BFD system does not process the payload of an Echo BFD.  Thus it is
   the local system that demultiplexes the Echo BFD packet matching it
   to the appropriate BFD session and detects missing Echo BFD packets.
   A BFD Control packet MAY be used as the payload of Echo BFD.  This
   specification defines the use of Echo BFD in SR-MPLS network with BFD
   Control packet as the payload.  The use of other types of Echo BFD
   payload is outside the scope of this document.  Because the remote
   BFD system does not process Echo BFD, the value of the Your
   Discriminator field MUST be set to the discriminator the local BFD
   system assigned to the given BFD session.  My Discriminator field
   MUST be zeroed.  Authentication MUST be set according to the
   configuration of the BFD session.  To ensure that the Echo BFD packet
   is returned to the sender without being processed, the sender MAY use
   a Binding SID (BSID) [RFC8402] that has been bound with the SR Policy
   that ensures the return of a packet to that particular node.  A BSID
   MAY be associated with the SR Policy that is the reverse to the SR
   Policy programmed onto the BFD Echo packet by the sender.

9.  IANA Considerations

9.1.  Non-FEC Path TLV

   IANA is requested to assign new TLV type from the from Standards
   Action range of the registry "Multiprotocol Label Switching
   Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters -
   TLVs" as defined in Table 1.

               +-------+------------------+---------------+
               | Value | TLV Name         | Reference     |
               +-------+------------------+---------------+
               | TBD1  | Non-FEC Path TLV | This document |
               +-------+------------------+---------------+

                       Table 1: New Non-FEC Path TLV

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   IANA is requested to create new Non-FEC Path sub-TLV registry for the
   Non-FEC Path TLV, as described in Table 2.

   +-------------+---------------+-------------------------------------+
   | Range       |  Registration | Note                                |
   |             |   Procedures  |                                     |
   +-------------+---------------+-------------------------------------+
   | 0-16383     |   Standards   | This range is for mandatory TLVs or |
   |             |     Action    | for optional TLVs that require an   |
   |             |               | error message if not recognized.    |
   | 16384-31743 | Specification | Experimental RFC needed             |
   |             |    Required   |                                     |
   | 32768-49161 |   Standards   | This range is for optional TLVs     |
   |             |     Action    | that can be silently dropped if not |
   |             |               | recognized.                         |
   | 49162-64511 | Specification | Experimental RFC needed             |
   |             |    Required   |                                     |
   | 64512-65535 |  Private Use  |                                     |
   +-------------+---------------+-------------------------------------+

                  Table 2: Non-FEC Path sub-TLV registry

   IANA is requested to allocate the following values from the Non-FEC
   Path sub-TLV registry as defined in Table 3.

      +-------+-------------------------------------+---------------+
      | Value | Description                         | Reference     |
      +-------+-------------------------------------+---------------+
      | 0     | Reserved                            | This document |
      | TBD2  | Segment Routing MPLS Tunnel sub-TLV | This document |
      | 65535 | Reserved                            | This document |
      +-------+-------------------------------------+---------------+

                Table 3: New Segment Routing Tunnel sub-TLV

9.2.  Return Code

   IANA is requested to create Non-FEC Path sub-TLV sub-registry for the
   new Non-FEC Path TLV and assign a new Return Code value from the
   "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
   Ping Parameters" registry, "Return Codes" sub-registry, as follows
   using a Standards Action value.

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           +--------+-------------------------+---------------+
           | Value  | Description             | Reference     |
           +--------+-------------------------+---------------+
           | X TBD3 | Too Many TLVs Detected. | This document |
           +--------+-------------------------+---------------+

                         Table 4: New Return Code

10.  Implementation Status

   - The organization responsible for the implementation: ZTE
   Corporation.

   - The implementation's name ROSng SW empowers traditional routers,
   e.g., ZXCTN 6000.

   - A brief general description: A list of SIDs can be specified as the
   Return Path for an SR-MPLS tunnel.

   - The implementation's level of maturity: production.

   - Coverage: complete

   - Version compatibility: draft-mirsky-spring-bfd-06.

   - Licensing: proprietary.

   - Implementation experience: Appreciate Early Allocation of values
   for Non-FEC TLV and Segment Routing MPLS Tunnel sub-TLV (using
   Private Use code points).

   - Contact information: Qian Xin qian.xin2@zte.com.cn

   - The date when information about this particular implementation was
   last updated: 12/16/2019

   Note to RFC Editor: This section MUST be removed before publication
   of the document.

11.  Security Considerations

   Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],
   and [RFC8029] apply to this document.

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12.  Contributors

      Xiao Min
      ZTE Corp.
      Email: xiao.min2@zte.com.cn

13.  Acknowledgments

   Authors greatly appreciate the help of Qian Xin, who provided the
   information about the implementation of this specification.

14.  References

14.1.  Normative References

   [I-D.ietf-mpls-bfd-directed]
              Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen,
              "Bidirectional Forwarding Detection (BFD) Directed Return
              Path", draft-ietf-mpls-bfd-directed-13 (work in progress),
              December 2019.

   [I-D.mirsky-bfd-mpls-demand]
              Mirsky, G., "BFD in Demand Mode over Point-to-Point MPLS
              LSP", draft-mirsky-bfd-mpls-demand-06 (work in progress),
              December 2019.

   [I-D.voyer-spring-sr-p2mp-policy]
              daniel.voyer@bell.ca, d., Filsfils, C., Parekh, R.,
              Bidgoli, H., and Z. Zhang, "SR Replication Policy for P2MP
              Service Delivery", draft-voyer-spring-sr-p2mp-policy-03
              (work in progress), July 2019.

   [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>.

   [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>.

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   [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>.

   [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>.

   [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>.

   [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>.

   [RFC8287]  Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya,
              N., Kini, S., and M. Chen, "Label Switched Path (LSP)
              Ping/Traceroute for Segment Routing (SR) IGP-Prefix and
              IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data
              Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017,
              <https://www.rfc-editor.org/info/rfc8287>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8562]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
              Ed., "Bidirectional Forwarding Detection (BFD) for
              Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
              April 2019, <https://www.rfc-editor.org/info/rfc8562>.

Mirsky, et al.          Expires October 28, 2020               [Page 12]
Internet-Draft             BFD in SPRING MPLS                 April 2020

   [RFC8563]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
              Ed., "Bidirectional Forwarding Detection (BFD) Multipoint
              Active Tails", RFC 8563, DOI 10.17487/RFC8563, April 2019,
              <https://www.rfc-editor.org/info/rfc8563>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

14.2.  Informative 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-10
              (work in progress), February 2020.

   [I-D.ietf-pim-bfd-p2mp-use-case]
              Mirsky, G. and J. Xiaoli, "Bidirectional Forwarding
              Detection (BFD) for Multi-point Networks and Protocol
              Independent Multicast - Sparse Mode (PIM-SM) Use Case",
              draft-ietf-pim-bfd-p2mp-use-case-03 (work in progress),
              January 2020.

   [I-D.ietf-spring-mpls-anycast-segments]
              Sarkar, P., Gredler, H., Filsfils, C., Previdi, S.,
              Decraene, B., and M. Horneffer, "Anycast Segments in MPLS
              based Segment Routing", draft-ietf-spring-mpls-anycast-
              segments-02 (work in progress), January 2018.

   [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>.

Authors' Addresses

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com

   Jeff  Tantsura
   Apstra, Inc.

   Email: jefftant.ietf@gmail.com

Mirsky, et al.          Expires October 28, 2020               [Page 13]
Internet-Draft             BFD in SPRING MPLS                 April 2020

   Ilya Varlashkin
   Google

   Email: Ilya@nobulus.com

   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com

   Jiang Wenying
   CMCC

   Email: jiangwenying@chinamobile.com

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