Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP
draft-mirsky-mpls-bfd-bootstrap-clarify-02

Document Type Active Internet-Draft (individual)
Authors Greg Mirsky  , Yanhua Zhao  , Gyan Mishra 
Last updated 2021-03-30
Stream (None)
Intended RFC status (None)
Formats plain text html xml pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
MPLS Working Group                                             G. Mirsky
Internet-Draft                                                   Y. Zhao
Updates: 5884 (if approved)                              ZTE Corporation
Intended status: Standards Track                               G. Mishra
Expires: 1 October 2021                                     Verizon Inc.
                                                           30 March 2021

       Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP
               draft-mirsky-mpls-bfd-bootstrap-clarify-02

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 1 October 2021.

Copyright Notice

   Copyright (c) 2021 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
   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
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Mirsky, et al.           Expires 1 October 2021                 [Page 1]
Internet-Draft   Clarify Bootstrapping BFD over MPLS LSP      March 2021

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.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

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 to be used for the Return mode
   field [RFC8029] when LSP ping is used to bootstrap a BFD session of
   MPLS LSP.  When LSP echo request is being used to detect defects in
   MPLS data plane and verify consistency between the control plane and
   the data plane echo reply is needed to confirm the correct state,
   provide positive acknowledgment.  But when an LSP echo request is
   being used to bootstrap BFD session, then the positive
   acknowledgment, according to [RFC5884] is provided by the egress
   transmitting BFD control message.  Thus LSP echo reply is not
   required to bootstrap BFD session and hence the Return mode field in
   echo request message SHOULD be set to 1 (Do not reply) [RFC8029] when
   LSP echo request used to bootstrap BFD session.

Mirsky, et al.           Expires 1 October 2021                 [Page 2]
Internet-Draft   Clarify Bootstrapping BFD over MPLS LSP      March 2021

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 echo reply to BFD bootstrapping echo
   request.

5.  IANA Considerations

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

6.  Security Considerations

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

7.  Acknowledgements

   TBA

8.  Normative References

   [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>.

   [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>.

Mirsky, et al.           Expires 1 October 2021                 [Page 3]
Internet-Draft   Clarify Bootstrapping BFD over MPLS LSP      March 2021

   [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
   ZTE Corporation

   Email: gregimirsky@gmail.com, gregory.mirsky@ztetx.com

   Yanhua Zhao
   ZTE Corporation

   Email: zhao.yanhua3@zte.com.cn

   Gyan Mishra
   Verizon Inc.

   Email: gyan.s.mishra@verizon.com

Mirsky, et al.           Expires 1 October 2021                 [Page 4]