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Zhao 4 Updates: 5884 (if approved) ZTE Corporation 5 Intended status: Standards Track October 18, 2017 6 Expires: April 21, 2018 8 Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP 9 draft-mirsky-mpls-bfd-bootstrap-clarify-00 11 Abstract 13 This document, if approved, updates RFC 5884 by clarifying procedures 14 for using MPLS LSP ping to bootstrap Bidirectional Forwarding 15 Detection (BFD) over MPLS Label Switch Path. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on April 21, 2018. 34 Copyright Notice 36 Copyright (c) 2017 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Conventions used in this document . . . . . . . . . . . . . . 2 53 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 54 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 2 55 3. Use of Return Mode Field . . . . . . . . . . . . . . . . . . 2 56 4. Use of BFD Discriminator TLV in LSP Echo Reply . . . . . . . 3 57 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 58 6. Security Considerations . . . . . . . . . . . . . . . . . . . 3 59 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 60 8. Normative References . . . . . . . . . . . . . . . . . . . . 3 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 63 1. Introduction 65 [RFC5884] defines how LSP Ping [RFC8029] uses BFD Discriminator TLV 66 to bootstrap Bidirectional Forwarding Detection (BFD) session over 67 MPLS Label Switch Path (LSP). Implementation and operational 68 experiences suggest that two aspects of using LSP ping to bootstrap 69 BFD session can benefit from clarification. This document updates 70 [RFC5884] in use of Return mode field in MPLS LSP echo request 71 message and use of BFD Discriminator TLV in MPLS LSP echo reply. 73 2. Conventions used in this document 75 2.1. Terminology 77 MPLS: Multiprotocol Label Switching 79 LSP: Label Switched Path 81 BFD: Bidirectional Forwarding Detection 83 2.2. Requirements Language 85 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 86 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 87 "OPTIONAL" in this document are to be interpreted as described in BCP 88 14 [RFC2119] [RFC8174] when, and only when, they appear in all 89 capitals, as shown here. 91 3. Use of Return Mode Field 93 [RFC5884] does not define the value to be used for the Return mode 94 field [RFC8029] when LSP ping is used to bootstrap a BFD session of 95 MPLS LSP. When LSP echo request is being used to detect defects in 96 MPLS data plane and verify consistency between the control plane and 97 the data plane echo reply is needed to confirm the correct state, 98 provide the positive acknowledgment. But when LSP echo request is 99 being used to bootstrap BFD session, then the positive 100 acknowledgement, according to [RFC5884] is provided by the egress 101 transmitting BFD control message. Thus LSP echo reply is not 102 required to bootstrap BFD session and hence the Return mode field in 103 echo request message SHOULD be set to 1 (Do not reply) [RFC8029] when 104 LSP echo request used to bootstrap BFD session. 106 4. Use of BFD Discriminator TLV in LSP Echo Reply 108 [RFC5884] in section 6 defines that echo reply by the egress LSR to 109 BFD bootstrapping echo request MAY include BFD Discriminator TLV with 110 locally assigned discriminator value for the BFD session. But the 111 [RFC5884] does not define how the ingress LSR may use the returned 112 value. From practical point, as discussed in Section 3, the returned 113 value is not useful since the egress is required to send the BFD 114 control message right after successfully validating the FEC and 115 before sending echo reply message. Secondly, identifying the 116 corresponding BFD session at ingress without returning its 117 discriminator presents unnecessary challenge for the implementation. 118 Thus the egress LSR SHOULD NOT include BFD Discriminator TLV if 119 sending echo reply to BFD bootstrapping echo request. 121 5. IANA Considerations 123 This document does not require any action by IANA. This section may 124 be removed. 126 6. Security Considerations 128 This document does not introduce new security aspects but inherits 129 all security considerations from [RFC5880], [RFC5884], [RFC8029]. 131 7. Acknowledgements 133 TBA 135 8. Normative References 137 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 138 Requirement Levels", BCP 14, RFC 2119, 139 DOI 10.17487/RFC2119, March 1997, 140 . 142 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 143 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 144 . 146 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 147 "Bidirectional Forwarding Detection (BFD) for MPLS Label 148 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 149 June 2010, . 151 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 152 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 153 Switched (MPLS) Data-Plane Failures", RFC 8029, 154 DOI 10.17487/RFC8029, March 2017, 155 . 157 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 158 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 159 May 2017, . 161 Authors' Addresses 163 Greg Mirsky 164 ZTE Corporation 166 Email: gregimirsky@gmail.com 168 Yanhua Zhao 169 ZTE Corporation 171 Email: zhao.yanhua3@zte.com.cn