Internet DRAFT - draft-mirsky-mpls-bfd-bootstrap-clarify

draft-mirsky-mpls-bfd-bootstrap-clarify







MPLS Working Group                                             G. Mirsky
Internet-Draft                                                  Ericsson
Updates: 5884 (if approved)                                      Y. Zhao
Intended status: Standards Track                         ZTE Corporation
Expires: 12 July 2024                                          G. Mishra
                                                            Verizon Inc.
                                                               R. Bonica
                                                        Juniper Networks
                                                          9 January 2024


       Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP
               draft-mirsky-mpls-bfd-bootstrap-clarify-05

Abstract

   This document, if approved, updates RFC 5884 by clarifying procedures
   for using MPLS LSP ping to bootstrap Bidirectional Forwarding
   Detection (BFD) over MPLS Label Switch Path.

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 12 July 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   extracted from this document must include Revised BSD License text as
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Use of Return Mode Field  . . . . . . . . . . . . . . . . . .   2
   4.  Use of BFD Discriminator TLV in LSP Echo Reply  . . . . . . .   3
   5.  Destination IPv6 Address  . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   [RFC5884] defines how LSP Ping [RFC8029] uses BFD Discriminator TLV
   to bootstrap Bidirectional Forwarding Detection (BFD) session over
   MPLS Label Switch Path (LSP).  Implementation and operational
   experiences suggest that two aspects of using LSP ping to bootstrap
   BFD session can benefit from clarification.  This document updates
   [RFC5884] in use of Return Mode field in MPLS LSP echo request
   message and use of BFD Discriminator TLV in MPLS LSP echo reply.

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.  Use of Return Mode Field

   [RFC5884] does not define the value for the Return Mode field
   [RFC8029] when LSP ping is used to bootstrap a BFD session of MPLS
   LSP.  When an LSP echo request is used to detect defects in the MPLS
   data plane and verify consistency between the control plane and the
   data plane, an echo reply is needed to confirm the correct state and
   provide positive acknowledgment.  But when an LSP echo request is



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   used to bootstrap a BFD session, the positive acknowledgment,
   according to[RFC5884], is provided by the egress transmitting BFD
   control message.  Thus LSP echo reply is not used to bootstrap the
   BFD session, and hence the Return Mode field in the echo request
   message SHOULD be set to 1 (Do not reply) [RFC8029] when LSP echo
   request is used to bootstrap a BFD session.  If bootstrapping a BFD
   session is combined with the periodic verification of a FEC as
   described in [RFC8029], the Return Mode field MAY be set to 2 (Reply
   via an IPv4/IPv6 UDP packet).  Furthermore, as proposed in
   [I-D.kompella-mpls-lspping-norao], the value of the Return Mode field
   in the echo request used to bootstrap a BFD session MUST NOT be set
   to 3 (Reply via an IPv4/IPv6 UDP packet with Router Alert).

4.  Use of BFD Discriminator TLV in LSP Echo Reply

   [RFC5884] in section 6 defines that echo reply by the egress LSR to
   BFD bootstrapping echo request MAY include BFD Discriminator TLV with
   locally assigned discriminator value for the BFD session.  But the
   [RFC5884] does not define how the ingress LSR may use the returned
   value.  From a practical point, as discussed in Section 3, the
   returned value is not useful since the egress is required to send the
   BFD control message right after successfully validating the FEC and
   before sending an echo reply message.  Secondly, identifying the
   corresponding BFD session at ingress without returning its
   discriminator presents an unnecessary challenge for the
   implementation.  Thus the egress LSR SHOULD NOT include BFD
   Discriminator TLV if sending an echo reply to BFD bootstrapping echo
   request.

5.  Destination IPv6 Address

   [RFC5884] requires that the IPv6 Destination Address used in IP/UDP
   encapsulation of an echo request packet is selected from the IPv4
   loopback address range mapped to IPv6.  Such packets do not have the
   same behavior as prescribed in [RFC1122] for an IPv4 loopback
   addressed packet.

   [RFC4291] defines ::1/128 as the single IPv6 loopback address.
   Considering that this specification updates Section 7 of [RFC5884]
   regarding the selection of an IPv6 destination address for a BFD
   Control message:

   *  For IPv6, the IPv6 loopback address ::1/128 SHOULD be used.

   *  The sender of an echo request MAY select the IPv6 destination
      address from the 0:0:0:0:0:FFFF:7F00/104 range.





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   *  To exercise all paths in an ECMP environment, the entropy other
      than the IP destination address SHOULD use the Entropy Label
      [RFC6790] to discover multiple alternate paths in an MPLS network.

6.  IANA Considerations

   This document does not require any action by IANA.  This section may
   be removed.

7.  Security Considerations

   This document does not introduce new security aspects but inherits
   all security considerations from [RFC5880], [RFC5884], [RFC8029].

8.  Acknowledgements

   TBA

9.  Normative References

   [I-D.kompella-mpls-lspping-norao]
              Kompella, K., Bonica, R., and G. Mirsky, "Deprecating the
              Use of Router Alert in LSP Ping", Work in Progress,
              Internet-Draft, draft-kompella-mpls-lspping-norao-02, 10
              December 2022, <https://datatracker.ietf.org/doc/html/
              draft-kompella-mpls-lspping-norao-02>.

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <https://www.rfc-editor.org/info/rfc1122>.

   [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>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [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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   [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>.

   [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>.

   [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>.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com


   Yanhua Zhao
   ZTE Corporation
   Email: zhao.yanhua3@zte.com.cn


   Gyan Mishra
   Verizon Inc.
   Email: gyan.s.mishra@verizon.com


   Ron Bonica
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA 94089
   United States
   Email: rbonica@juniper.net








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