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Mishra 6 Expires: 1 October 2021 Verizon Inc. 7 30 March 2021 9 Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP 10 draft-mirsky-mpls-bfd-bootstrap-clarify-02 12 Abstract 14 This document, if approved, updates RFC 5884 by clarifying procedures 15 for using MPLS LSP ping to bootstrap Bidirectional Forwarding 16 Detection (BFD) over MPLS Label Switch Path. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on 1 October 2021. 35 Copyright Notice 37 Copyright (c) 2021 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 42 license-info) in effect on the date of publication of this document. 43 Please review these documents carefully, as they describe your rights 44 and restrictions with respect to this document. Code Components 45 extracted from this document must include Simplified BSD License text 46 as described in Section 4.e of the Trust Legal Provisions and are 47 provided without warranty as described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 53 3. Use of Return Mode Field . . . . . . . . . . . . . . . . . . 2 54 4. Use of BFD Discriminator TLV in LSP Echo Reply . . . . . . . 3 55 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 56 6. Security Considerations . . . . . . . . . . . . . . . . . . . 3 57 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 58 8. Normative References . . . . . . . . . . . . . . . . . . . . 3 59 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 61 1. Introduction 63 [RFC5884] defines how LSP Ping [RFC8029] uses BFD Discriminator TLV 64 to bootstrap Bidirectional Forwarding Detection (BFD) session over 65 MPLS Label Switch Path (LSP). Implementation and operational 66 experiences suggest that two aspects of using LSP ping to bootstrap 67 BFD session can benefit from clarification. This document updates 68 [RFC5884] in use of Return mode field in MPLS LSP echo request 69 message and use of BFD Discriminator TLV in MPLS LSP echo reply. 71 2. Requirements Language 73 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 74 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 75 "OPTIONAL" in this document are to be interpreted as described in BCP 76 14 [RFC2119] [RFC8174] when, and only when, they appear in all 77 capitals, as shown here. 79 3. Use of Return Mode Field 81 [RFC5884] does not define the value to be used for the Return mode 82 field [RFC8029] when LSP ping is used to bootstrap a BFD session of 83 MPLS LSP. When LSP echo request is being used to detect defects in 84 MPLS data plane and verify consistency between the control plane and 85 the data plane echo reply is needed to confirm the correct state, 86 provide positive acknowledgment. But when an LSP echo request is 87 being used to bootstrap BFD session, then the positive 88 acknowledgment, according to [RFC5884] is provided by the egress 89 transmitting BFD control message. Thus LSP echo reply is not 90 required to bootstrap BFD session and hence the Return mode field in 91 echo request message SHOULD be set to 1 (Do not reply) [RFC8029] when 92 LSP echo request used to bootstrap BFD session. 94 4. Use of BFD Discriminator TLV in LSP Echo Reply 96 [RFC5884] in section 6 defines that echo reply by the egress LSR to 97 BFD bootstrapping echo request MAY include BFD Discriminator TLV with 98 locally assigned discriminator value for the BFD session. But the 99 [RFC5884] does not define how the ingress LSR may use the returned 100 value. From a practical point, as discussed in Section 3, the 101 returned value is not useful since the egress is required to send the 102 BFD control message right after successfully validating the FEC and 103 before sending an echo reply message. Secondly, identifying the 104 corresponding BFD session at ingress without returning its 105 discriminator presents an unnecessary challenge for the 106 implementation. Thus the egress LSR SHOULD NOT include BFD 107 Discriminator TLV if sending echo reply to BFD bootstrapping echo 108 request. 110 5. IANA Considerations 112 This document does not require any action by IANA. This section may 113 be removed. 115 6. Security Considerations 117 This document does not introduce new security aspects but inherits 118 all security considerations from [RFC5880], [RFC5884], [RFC8029]. 120 7. Acknowledgements 122 TBA 124 8. Normative References 126 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 127 Requirement Levels", BCP 14, RFC 2119, 128 DOI 10.17487/RFC2119, March 1997, 129 . 131 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 132 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 133 . 135 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 136 "Bidirectional Forwarding Detection (BFD) for MPLS Label 137 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 138 June 2010, . 140 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 141 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 142 Switched (MPLS) Data-Plane Failures", RFC 8029, 143 DOI 10.17487/RFC8029, March 2017, 144 . 146 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 147 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 148 May 2017, . 150 Authors' Addresses 152 Greg Mirsky 153 ZTE Corporation 155 Email: gregimirsky@gmail.com, gregory.mirsky@ztetx.com 157 Yanhua Zhao 158 ZTE Corporation 160 Email: zhao.yanhua3@zte.com.cn 162 Gyan Mishra 163 Verizon Inc. 165 Email: gyan.s.mishra@verizon.com