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Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Standards Track May 8, 2017 5 Expires: November 9, 2017 7 Bidirectional Forwarding Detection (BFD) in Segment Routing Networks 8 Using MPLS Dataplane 9 draft-mirsky-spring-bfd-00 11 Abstract 13 Segment Routing architecture leverages the paradigm of source 14 routing. It can be realized in the Multiprotocol Label Switching 15 (MPLS) network without any change to the data plane. A segment is 16 encoded as an MPLS label and an ordered list of segments is encoded 17 as a stack of labels. Bidirectional Forwarding Detection (BFD) is 18 expected to monitor any kind of paths between systems. This document 19 defines how to use Label Switched Path Ping to bootstrap and control 20 path in reverse direction of a BFD session on the Segment Routing 21 network over MPLS dataplane. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on November 9, 2017. 40 Copyright Notice 42 Copyright (c) 2017 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 1.1. Conventions used in this document . . . . . . . . . . . . 2 59 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 2 60 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 61 2. Bootstrapping BFD session over Segment Routed tunnel . . . . 3 62 3. Use BFD Reverse Path TLV over Segment Routed MPLS tunnel . . 4 63 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 66 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 67 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 69 1. Introduction 71 [RFC5880], [RFC5881], and [RFC5883] established the Bidirectional 72 Forwarding Detection (BFD) protocol for IP networks. [RFC5884] and 73 [RFC7726] set rules of using BFD Asynchronous mode over Multiprotocol 74 Label Switching (MPLS) Label Switched Path (LSP). These latter 75 standards implicitly assume that the egress BFD peer, which is the 76 egress Label Edge Router (LER), will use the shortest path route 77 regardless of the path the ingress LER uses to send BFD control 78 packets towards it. 80 This document defines use of LSP Ping for Segment Routing networks 81 over MPLS dataplane [I-D.ietf-mpls-spring-lsp-ping] to bootstrap and 82 control path of a BFD session from the egress to ingress LER. 84 1.1. Conventions used in this document 86 1.1.1. Terminology 88 BFD: Bidirectional Forwarding Detection 90 FEC: Forwarding Equivalence Class 92 MPLS: Multiprotocol Label Switching 94 LSP: Label Switching Path 96 LER: Label Edge Router 98 1.1.2. Requirements Language 100 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 101 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 102 "OPTIONAL" in this document are to be interpreted as described in 103 [RFC2119]. 105 2. Bootstrapping BFD session over Segment Routed tunnel 107 As discussed in [I-D.ietf-mpls-spring-lsp-ping] introduction of 108 Segment Routing network domains with an MPLS data plane adds three 109 new sub-TLVs that MAY be used with Target Forwarding Equivalence 110 Class (FEC) TLV. Section 6.1 addresses use of the new sub-TLVs in 111 Target FEC TLV in LSP ping and LSP traceroute. For the case of LSP 112 ping the [I-D.ietf-mpls-spring-lsp-ping] states that: 114 Initiator MUST include FEC(s) corresponding to the destination 115 segment. 117 Initiator, i.e. ingress LSR, MAY include FECs corresponding to 118 some or all of segments imposed in the label stack by the ingress 119 LSR to communicate the segments traversed. 121 It has been noted in [RFC5884] that a BFD session monitors for 122 defects particular tuple. [RFC7726] clarified how to 123 establish and operate mutiple BFD sessions for the same tuple. Because only ingress edge router is aware of the SR- 125 based explicit route egress edge router can associate the LSP ping 126 with BFD Discriminator TLV with only one of the FECs it advertised 127 for the particular segment. Thus this document defines that: When 128 LSP ping is used to bootstrap a BFD session this document updates the 129 statement and defines that: 131 When LSP Ping is used to bootstrap a BFD session it MUST include 132 only one FEC corresponding to the destination segment and SHOULD 133 NOT include FECs corresponding to some or all of other segments 134 imposed by the ingress LSR. 136 Operationally such restriction would not cause any problem or 137 uncertainty as LSP ping with FECs corresponding to some or all 138 segments or traceroute that validate the segment route MAY precede 139 the LSP ping that bootstraps the BFD session. 141 Encapsulation of a BFD Control packet in Segment Routing network with 142 MPLS dataplane MUST follow Section 7 [RFC5884] when IP/UDP header 143 used and MUST follow Section 3.4 [RFC6428] without IP/UDP header 144 being used. 146 3. Use BFD Reverse Path TLV over Segment Routed MPLS tunnel 148 When a BFD session is used to monitor a source routed unidirectional 149 path there may be a need to direct egress BFD peer to use specific 150 path for the reverse direction of the BFD session by using the BFD 151 Reverse Path TLV [I-D.ietf-mpls-bfd-directed]. For the case of MPLS 152 dataplane, Segment Routing Architecture 153 [I-D.ietf-spring-segment-routing] explains that "a segment is encoded 154 as an MPLS label. An ordered list of segments is encoded as a stack 155 of labels." Following on that this document defines Segment Routing 156 with MPLS dataplane sub-TLV that MAY be used with the BFD Reverse 157 Path TLV [I-D.ietf-mpls-bfd-directed]. The format of the sub-TLV is 158 presented in Figure 1. 160 0 1 2 3 161 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 | SegRouting MPLS sub-TLV Type | Length | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | Label Entry 1 | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | Label Entry 2 | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 ~ ~ 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | Label Entry N | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 Figure 1: Segment Routing MPLS Tunnel sub-TLV 176 The Segment Routing Tunnel sub-TLV Type is two octets in length, and 177 has a value of TBD (to be assigned by IANA as requested in 178 Section 4). 180 The egress LSR MUST use the Value field as label stack for BFD 181 control packets for the BFD session identified by the source IP 182 address of the MPLS LSP Ping packet and the value in the BFD 183 Discriminator TLV. Label Entries MUST be in network order. 185 Exactly one Segment Routing Tunnel sub-TLV MUST be included in the 186 Reverse Path TLV. If more than one Segment Routing Tunnel sub-TLV is 187 present in the Reverse Path TLV, then, in order to avoid ambiguity of 188 which of TLVs to use, the egress BFD peer MUST send Echo Reply with 189 the received Reverse Path TLVs and set the Return Code to "Too Many 190 TLVs Detected" [I-D.ietf-mpls-bfd-directed] 191 The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV 192 defined in [RFC7110] 194 4. IANA Considerations 196 The IANA is requested to assign new sub-TLV type from "Multiprotocol 197 Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping 198 Parameters - TLVs" registry, "Sub-TLVs for TLV Types 1, 16, and 21" 199 sub-registry. 201 +---------+-------------------------------------+---------------+ 202 | Value | Description | Reference | 203 +---------+-------------------------------------+---------------+ 204 | X (TBD) | Segment Routing MPLS Tunnel sub-TLV | This document | 205 +---------+-------------------------------------+---------------+ 207 Table 1: New Segment Routing Tunnel sub-TLV 209 5. Security Considerations 211 Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], 212 and [RFC8029] apply to this document. 214 6. Acknowledgements 216 TBD 218 7. Normative References 220 [I-D.ietf-mpls-bfd-directed] 221 Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, 222 "Bidirectional Forwarding Detection (BFD) Directed Return 223 Path", draft-ietf-mpls-bfd-directed-06 (work in progress), 224 April 2017. 226 [I-D.ietf-mpls-spring-lsp-ping] 227 Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini, 228 S., Gredler, H., and M. Chen, "Label Switched Path (LSP) 229 Ping/Trace for Segment Routing Networks Using MPLS 230 Dataplane", draft-ietf-mpls-spring-lsp-ping-02 (work in 231 progress), December 2016. 233 [I-D.ietf-spring-segment-routing] 234 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 235 and R. Shakir, "Segment Routing Architecture", draft-ietf- 236 spring-segment-routing-11 (work in progress), February 237 2017. 239 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 240 Requirement Levels", BCP 14, RFC 2119, 241 DOI 10.17487/RFC2119, March 1997, 242 . 244 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 245 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 246 . 248 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 249 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 250 DOI 10.17487/RFC5881, June 2010, 251 . 253 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 254 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 255 June 2010, . 257 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 258 "Bidirectional Forwarding Detection (BFD) for MPLS Label 259 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 260 June 2010, . 262 [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., 263 "Proactive Connectivity Verification, Continuity Check, 264 and Remote Defect Indication for the MPLS Transport 265 Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, 266 . 268 [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, 269 "Return Path Specified Label Switched Path (LSP) Ping", 270 RFC 7110, DOI 10.17487/RFC7110, January 2014, 271 . 273 [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 274 Aldrin, "Clarifying Procedures for Establishing BFD 275 Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, 276 DOI 10.17487/RFC7726, January 2016, 277 . 279 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 280 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 281 Switched (MPLS) Data-Plane Failures", RFC 8029, 282 DOI 10.17487/RFC8029, March 2017, 283 . 285 Author's Address 287 Greg Mirsky 288 ZTE Corp. 290 Email: gregimirsky@gmail.com