MPLS Working Group G. Mirsky Internet-Draft Y. Zhao Updates: 5884 (if approved) ZTE Corporation Intended status: Standards Track G. Mishra Expires: June 11, 2021 Verizon Inc. December 8, 2020 Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP draft-mirsky-mpls-bfd-bootstrap-clarify-01 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 June 11, 2021. 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 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 June 11, 2021 [Page 1]
Internet-Draft Clarify Bootstrapping BFD over MPLS LSP December 2020 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 June 11, 2021 [Page 2]
Internet-Draft Clarify Bootstrapping BFD over MPLS LSP December 2020 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 June 11, 2021 [Page 3]
Internet-Draft Clarify Bootstrapping BFD over MPLS LSP December 2020 [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 Yanhua Zhao ZTE Corporation Email: zhao.yanhua3@zte.com.cn Gyan Mishra Verizon Inc. Email: gyan.s.mishra@verizon.com Mirsky, et al. Expires June 11, 2021 [Page 4]