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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Z. Hu 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track H. Chen 5 Expires: April 30, 2020 Futurewei 6 J. Yao 7 Huawei Technologies 8 C. Bowers 9 Juniper Networks 10 Y. Zhu 11 China Telecom 12 October 28, 2019 14 SR-TE Path Midpoint Protection 15 draft-hu-spring-segment-routing-proxy-forwarding-06 17 Abstract 19 Segment Routing Traffic Engineering (SR-TE) supports the creation of 20 explicit paths using segment lists containing adjacency-SIDs, node- 21 SIDs, anycast-SIDs, and binding-SIDs. When the segment list defining 22 an SR-TE path contains a node-SID, and the node fails, the network 23 may no longer be able to properly forward traffic on that SR-TE path. 24 [I-D.bashandy-rtgwg-segment-routing-ti-lfa] and 25 [I-D.hegde-spring-node-protection-for-sr-te-paths] describe a 26 mechanism that allows local repair actions on the direct neighbors of 27 the failed node to temporarily route traffic to the node immediately 28 following the failed node on the SR-TE path segment list. However, 29 once the IGP shortest paths have converged, the local repair 30 mechanism is no longer sufficient to continue forwarding traffic 31 using the original segment list of the SR-TE path, since the non- 32 neighbors of the failed node will no longer have a route to reach the 33 failed node. This document describes a mechanism that allows traffic 34 to continue to be forwarded on an SR-TE path for an extended period 35 of time after the failure of a node used in the path's segment list. 37 Requirements Language 39 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 40 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 41 document are to be interpreted as described in RFC 2119 [RFC2119]. 43 Status of This Memo 45 This Internet-Draft is submitted in full conformance with the 46 provisions of BCP 78 and BCP 79. 48 Internet-Drafts are working documents of the Internet Engineering 49 Task Force (IETF). Note that other groups may also distribute 50 working documents as Internet-Drafts. The list of current Internet- 51 Drafts is at https://datatracker.ietf.org/drafts/current/. 53 Internet-Drafts are draft documents valid for a maximum of six months 54 and may be updated, replaced, or obsoleted by other documents at any 55 time. It is inappropriate to use Internet-Drafts as reference 56 material or to cite them other than as "work in progress." 58 This Internet-Draft will expire on April 30, 2020. 60 Copyright Notice 62 Copyright (c) 2019 IETF Trust and the persons identified as the 63 document authors. All rights reserved. 65 This document is subject to BCP 78 and the IETF Trust's Legal 66 Provisions Relating to IETF Documents 67 (https://trustee.ietf.org/license-info) in effect on the date of 68 publication of this document. Please review these documents 69 carefully, as they describe your rights and restrictions with respect 70 to this document. Code Components extracted from this document must 71 include Simplified BSD License text as described in Section 4.e of 72 the Trust Legal Provisions and are provided without warranty as 73 described in the Simplified BSD License. 75 Table of Contents 77 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 78 2. Extensions to IGP for Proxy Forwarding . . . . . . . . . . . 4 79 2.1. Extensions to OSPF . . . . . . . . . . . . . . . . . . . 4 80 2.1.1. Advertising Proxy Forwarding . . . . . . . . . . . . 4 81 2.1.2. Advertising Binding Segment . . . . . . . . . . . . . 7 82 2.2. Extensions to IS-IS . . . . . . . . . . . . . . . . . . . 9 83 2.2.1. Advertising Proxy Forwarding . . . . . . . . . . . . 9 84 2.2.2. Advertising Binding Segment . . . . . . . . . . . . . 11 85 3. Building Proxy Forwarding Table . . . . . . . . . . . . . . . 13 86 3.1. Advertising Proxy Forwarding . . . . . . . . . . . . . . 15 87 3.2. Building Proxy Forwarding Table . . . . . . . . . . . . . 15 88 4. Node Protection for Segment List . . . . . . . . . . . . . . 15 89 4.1. Next Segment is an Adjacency Segment . . . . . . . . . . 16 90 4.2. Next Segment is a Node Segment . . . . . . . . . . . . . 16 91 4.3. Next Segment is a Binding Segment . . . . . . . . . . . . 17 92 5. Security Considerations . . . . . . . . . . . . . . . . . . . 18 93 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 94 6.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 18 95 6.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 19 96 6.3. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 19 97 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 98 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 99 8.1. Normative References . . . . . . . . . . . . . . . . . . 20 100 8.2. Informative References . . . . . . . . . . . . . . . . . 21 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 103 1. Introduction 105 Segment Routing Traffic Engineering (SR-TE) is a technology that 106 implements traffic engineering using Segment Routing. SR-TE supports 107 the creation of explicit paths using adjacency-SIDs, node-SIDs, 108 anycast-SIDs, and binding-SIDs. A node-SID in the segment list 109 defining an SR-TE path indicates a loose hop that the SR-TE path 110 should pass through. When a particular node fails, it would be 111 useful to be able to continue to send traffic on an SR-TE path that 112 uses the node-SID of the failed node for an extended period of time, 113 without having to immediately modify the segment list used at the 114 ingress to the SR-TE path. 116 The first step to achieve this objective is to make the rest of the 117 routers in the network continue to forward traffic using the node-SID 118 of the failed node. If we don't do anything special, once the IGP 119 converges to take into account the failed node, a given router will 120 no longer maintain a route corresponding to the node-SID. Any 121 traffic that arrives at the router with the node-SID of the failed 122 node as the active segment will be dropped. This document addresses 123 this problem by having each neighbor of the failed node advertise its 124 SR proxy forwarding capability. This indicates that the neighbor 125 (the Proxy Forwarder) will forward traffic on behalf of the failed 126 node. A router receiving the SR Proxy Forwarding capability from 127 neighbors of a failed node will send traffic using the node-SID of 128 the failed node to the nearest Proxy Forwarder. 130 Once the affected traffic reaches a Proxy Forwarder, the Proxy 131 Forwarder sends the traffic on the post-failure shortest path to the 132 node immediately following the failed node in the segment list. 133 [I-D.bashandy-rtgwg-segment-routing-ti-lfa] and 134 [I-D.hegde-spring-node-protection-for-sr-te-paths] describe how the 135 immediate neighbors of a failed node can accomplish this by 136 forwarding based on the first two segments in the segment list. The 137 forwarding described in these drafts was originally intended to be 138 used for only a short period of time, to provide fast-reroute 139 protection until the IGP converges. The current document proposes to 140 extend this behavior on the Proxy Forwarder until well after the IGP 141 has converged. 143 If the faulty node is a label adhesion node, the Binding-SIDs cannot 144 be exchanged to the label stack for its identity, and the traffic 145 will be lost before it reaches the faulty node. 147 In this document, the proxy mechanism is provided in the neighbor 148 node of the faulty node of the forwarding path to implement traffic 149 forwarding after the node with the label adhesion fails on the SR-TE 150 loose path. 152 2. Extensions to IGP for Proxy Forwarding 154 When a node has segment routing proxy forwarding capability, it 155 advertises this capability. The capability indicates that the node 156 has the ability to do proxy forwarding for the global SID of each of 157 its neighbors. When an neighbor in a SR-TE path fails, the traffic 158 can be forwarded to the proxy node, which fast re-routes the traffic 159 to the node immediately following the failed node on the SR-TE path. 161 2.1. Extensions to OSPF 163 2.1.1. Advertising Proxy Forwarding 165 When a node P has the capability to do a SR proxy forwarding for all 166 its neighboring nodes for protecting the failures of these nodes, 167 node P advertises its SR proxy forwarding capability in its router 168 information opaque LSA, which contains a Router Functional 169 Capabilities TLV of the format as shown in Figure 1. 171 0 1 2 3 172 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 1 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | Type | Length | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 | Functional Capabilities | 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 Figure 1: Router Functional Capabilities TLV 181 One bit (called PF bit) in the Functional Capabilities field of the 182 TLV is used to indicate node P's SR proxy forwarding capability. 183 When this bit is set to one by node P, it indicates that node P is 184 capable of doing a SR proxy forwarding for its neighboring nodes. 186 For a node X in the network, it learns the prefix/node SID of node N, 187 which is originated and advertised by node N. It creates a proxy 188 prefix/node SID of node N for node P if node P is capable of doing SR 189 proxy forwarding for node N. The proxy prefix/node SID of node N for 190 node P is a copy of the prefix/node SID of node N originated by node 191 N, but stored under (or say, associated with) node P. 193 In normal operations, node X prefers to use the prefix/node SID of 194 node N. When node N fails, node X prefers to use the proxy prefix/ 195 node SID of node N. Thus node X will forward the traffic targeting 196 to node N to node P when node N fails, and node P will do a SR proxy 197 forwarding for node N and forwarding the traffic to its destination 198 without going through node N. After node N fails, node X will keep 199 the proxy prefix/node SID of node N for a given period of time. 201 If node P can not do a SR proxy forwarding for all its neighboring 202 nodes, but for some of them, then it advertises the node SID of each 203 of the nodes as a proxy node SID, indicating that it is able to do 204 proxy forwarding for the node SID. 206 A new TLV, called Proxy Node SIDs TLV, is defined for node P to 207 advertise the node SIDs of some of its neighboring nodes. It has the 208 format as shown in Figure 2. 210 0 1 2 3 211 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 1 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 | Type (TBD1) | Length | 214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 | Node SID Sub-TLVs | 216 : : 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 Figure 2: OSPF Proxy Node SIDs TLV 221 The Type (TBD1) is to be assigned by IANA. The TLV contains a number 222 of Node SID Sub-TLVs. The Length is the total size of the Node SID 223 Sub-TLVs included in the TLV. A Node SID Sub-TLV is the Prefix SID 224 Sub-TLV defined in [I-D.ietf-ospf-segment-routing-extensions]. 226 A proxy forwarding node P originates an Extended Prefix Opaque LSA 227 containing this new TLV. The TLV includes the Node SID Sub-TLVs for 228 the node SIDs of some of P's neighboring nodes. For each of some of 229 P's neighboring nodes, the Node SID Sub-TLV for its prefix/node SID 230 is included the TLV. This prefix/node SID is called a proxy prefix/ 231 node SID. 233 A proxy forwarding node will originate an Extended Prefix Opaque LSA, 234 which includes a Proxy Node SIDs TLV. The format of the LSA is shown 235 in Figure 3. 237 For a proxy forwarding node P, having a number of neighboring nodes, 238 P originates and maintains an Extended Prefix Opaque LSA, which 239 includes a Proxy Node SIDs TLV. The TLV contains the Prefix/Node SID 240 Sub-TLV for each of some of the neighboring nodes after node P 241 creates the corresponding proxy forwarding entries for protecting the 242 failure of some of the neighboring nodes. 244 0 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | LS age | Options | LS Type | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Opaque Type(7)| Opaque ID | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | Advertising Router | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | LS sequence number | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | LS checksum | Length | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | | 258 : TLVs : 259 : (including Proxy Node SIDs TLV) : 260 | | 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 Figure 3: OSPFv2 Extended Prefix Opaque LSA 265 When an neighboring node fails, P maintains the LSA with the TLV 266 containing the Prefix/Node SID Sub-TLV for the neighboring node for a 267 given period of time. After the given period of time, the Prefix/ 268 Node SID Sub-TLV for the neighboring node is removed from the TLV in 269 the LSA and then after a given time the corresponding proxy 270 forwarding entries for protecting the failure of the neighboring node 271 is removed. 273 For a node X in the network, it learns the prefix/node SID of node N 274 and the proxy prefix/node SID of node N. The former is originated 275 and advertised by node N, and the latter is originated and advertised 276 by the proxy forwarding node P of node N. Note that the proxy 277 Prefix/Node SID Sub-TLV for node N does not contain a prefix of node 278 N, and the prefix is the prefix associated with the prefix/node SID 279 of node N originated by node N. 281 In normal operations, node X prefers to use the prefix/node SID of 282 node N. When node N fails, node X prefers to use the proxy prefix/ 283 node SID of node N. Thus node X will forward the traffic targeting 284 to node N to node P when node N fails, and node P will do a proxy 285 forwarding for node N and forwarding the traffic to its destination 286 without going through node N. 288 2.1.2. Advertising Binding Segment 290 For a binding segment (or binding for short) on a node A, which 291 consists of a binding SID and a list of segments, node A advertises 292 an LSA containing the binding (i.e., the binding SID and the list of 293 the segments). The LSA is advertised only to each of the node A's 294 neighboring nodes. For OSPFv2, the LSA is a opaque LSA of LS type 9 295 (i.e., a link local scope LSA). 297 A binding segment is represented by binding segment TLV of the format 298 as shown in Figure 4. 300 0 1 2 3 301 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 1 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 303 | Type (TBD2) | Length | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 305 | Reserved |BindingSID Type| SIDs Type | 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 ~ Binding SID Sub-TLV/value ~ 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 ~ SID Sub-TLVs/values ~ 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 312 Figure 4: OSPF Binding Segment TLV 314 It comprises a binding SID and a list of segments (SIDs). The fields 315 of this TLV are defined as follows: 317 Type: 2 octets, its value (TBD2) is to be assigned by IANA. 319 Length: 2 octets, its value is (4 + length of Sub-TLVs/values). 321 Binding SID Type (BT): 1 octet indicates whether the binding SID is 322 represented by a Sub-TLV or a value included in the TLV. For the 323 binding SID represented by a value, it indicates the type of binding 324 SID. The following BT values are defined: 326 o BT = 0: The binding SID is represented by a Sub-TLV (i.e., Binding 327 SID Sub-TLV) in the TLV. A binding SID Sub-TLV is a SID/Label Sub- 328 TLV defined in [I-D.ietf-ospf-segment-routing-extensions]. BT != 0 329 indicates that the binding SID is represented by a value. 331 o BT = 1: The binding SID value is a label, which is represented by 332 the 20 rightmost bits. The length of the value is 3 octets. 334 o BT = 2: The binding SID value is a 32-bit SID. The length of the 335 value is 4 octets. 337 SIDs Type (ST): 1 octet indicates whether the list of segments (SIDs) 338 are represented by Sub-TLVs or values included in the TLV. For the 339 SIDs represented by values, it indicates the type of SIDs. The 340 following ST values are defined: 342 o ST = 0: The SIDs are represented by Sub-TLVs (i.e., SID Sub-TLVs) 343 in the TLV. A SID Sub-TLV is an Adj-SID Sub-TLV, a Prefix-SID Sub- 344 TLV or a SID/Label Sub-TLV defined in 345 [I-D.ietf-ospf-segment-routing-extensions]. ST != 0 indicates that 346 the SIDs are represented by values. 348 o ST = 1: Each of the SID values is a label, which is represented by 349 the 20 rightmost bits. The length of the value is 3 octets. 351 o ST = 2: Each of the SID values is a 32-bit SID. The length of the 352 value is 4 octets. 354 The opaque LSA of LS Type 9 containing the binding segment (i.e., the 355 binding SID and the list of the segments) has the format as shown in 356 Figure 5. It may have Opaque Type of x (the exact type is to be 357 assigned by IANA) for Binding Segment Opaque LSA. 359 0 1 2 3 360 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 1 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 362 | LS age | Options | LS Type (9) | 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 | Opaque Type(x)| Opaque ID | 365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 | Advertising Router | 367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 368 | LS sequence number | 369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 370 | LS checksum | Length | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | | 373 : Binding Segment TLVs : 374 | | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 Figure 5: OSPFv2 Binding Segment Opaque LSA 379 For every binding on a node A, the LSA originated by A contains a 380 binding segment TLV for it. 382 For node A running OSPFv3, it originates a link-local scoping LSA of 383 a new LSA function code (TBD3) containing binding segment TLVs for 384 the bindings on it. The format of the LSA is illustrated in 385 Figure 6. 387 0 1 2 3 388 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 1 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | LS age |0|0|0| BS-LSA (TBD3) | 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 | Link State ID | 393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 394 | Advertising Router | 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | LS Sequence Number | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 | LS checksum | Length | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 | | 401 : Binding Segment TLVs : 402 | | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 405 Figure 6: OSPFv3 Binding Segment Opaque LSA 407 The U-bit is set to 0, and the scope is set to 00 for link-local 408 scoping. 410 2.2. Extensions to IS-IS 412 2.2.1. Advertising Proxy Forwarding 414 When a node P has the capability to do a SR proxy forwarding for its 415 neighboring nodes for protecting the failures of them, node P 416 advertises its SR proxy forwarding capability in its LSP, which 417 contains a Router Capability TLV of Type 242 including a SR 418 capabilities sub-TLV of sub-Type 2. 420 One bit (called PF bit as shown in Figure 7) in the Flags field of 421 the SR capabilities sub-TLV is defined to indicate node P's SR proxy 422 forwarding capability. When this bit is set to one by node P, it 423 indicates that node P is capable of doing a SR proxy forwarding for 424 its neighboring nodes. 426 0 1 2 3 427 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 1 428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 429 | Type (2) | Length | Flags | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | Range | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 // SID/Label Sub-TLV (variable) // 434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 436 0 1 2 3 4 5 6 7 437 +--+--+--+--+--+--+--+--+ 438 | I| V|PF| | 439 +--+--+--+--+--+--+--+--+ 440 Flags 442 Figure 7: SR Capabilities sub-TLV 444 If node P can not do a SR proxy forwarding for all its neighboring 445 nodes, but for some of them, then it advertises the node SID of each 446 of the nodes as a proxy node SID, indicating that it is able to do 447 proxy forwarding for the node SID. 449 The IS-IS SID/Label Binding TLV (suggested value 149) is defined in 450 [I-D.ietf-isis-segment-routing-extensions]. A Proxy Forwarder uses 451 the SID/Label Binding TLV to advertise the node SID of its 452 neighboring node. The Flags field of the SID/Label Binding TLV is 453 extended to include a P flag as shown in Figure 8. The prefix/node 454 SID in prefix/node SID Sub-TLV included in SID/Label Binding TLV is 455 identified as a proxy forwarding prefix/node SID. 457 0 1 2 3 458 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 1 459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 460 | Type | Length | Flags | RESERVED | 461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 462 | Range | Prefix Length | Prefix | 463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 464 // Prefix (continued, variable) // 465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 | SubTLVs (variable) | 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 469 0 1 2 3 4 5 6 7 470 +-+-+-+-+-+-+-+-+ 471 |F|M|S|D|A|P| | 472 +-+-+-+-+-+-+-+-+ 473 Flags 475 Figure 8: SID/Label Binding TLV 477 Where: 479 P-Flag: Proxy forwarding flag. If set, this prefix/node SID is 480 advertised by the proxy node. This TLV is used to announce that the 481 node has the ability to proxy forward the prefix/node SID. 483 When the P-flag is set in the SID/Label Binding TLV, the following 484 usage rules apply. 486 The Range, Prefix Length and Prefix field are not used. They should 487 be set to zero on transmission and ignored on receipt. 489 SID/Label Binding TLV contains a number of prefix/node SID Sub-TLVs. 490 The TLV advertised by a proxy forwarding node P contains prefix/node 491 SID Sub-TLVs for the node SIDs of P's neighbor nodes. Each of the 492 Sub-TLVs is a prefix/node SID Sub-TLV defined in 493 [I-D.ietf-isis-segment-routing-extensions]. From the SID in a 494 prefix/node SID Sub-TLV advertised by the Proxy Forwarding node, its 495 prefix can be obtained through matching corresponding prefix/node SID 496 advertised by the neighbor/protected node using TLV-135 (or 235, 236, 497 or 237) together with the prefix/node SID Sub-TLV. 499 2.2.2. Advertising Binding Segment 501 [I-D.ietf-spring-segment-routing-policy] has defined the usage of 502 binding-SID. For supporting binding SID proxy forwarding, a new IS- 503 IS TLV, called Binding Segment TLV, is defined. It contains a 504 binding SID and a list of segments (SIDs). This TLV may be 505 advertised in IS-IS Hello (IIH) PDUs, LSPs, or in Circuit Scoped Link 506 State PDUs (CS-LSP) [RFC7356]. Its format is shown in Figure 9. 508 0 1 2 3 509 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 1 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | Type | Length |BindingSID Type| SIDs Type | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 ~ Binding SID value/Sub-TLV ~ 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 ~ SID values/Sub-TLVs ~ 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 Figure 9: IS-IS Binding Segment TLV 520 The fields of this TLV are defined as follows: 522 Type: 1 octet Suggested value 152 (to be assigned by IANA) 524 Length: 1 octet (2 + length of Sub-TLVs/values). 526 Binding SID Type (BT): 1 octet indicates whether the binding SID is 527 represented by a Sub-TLV or a value included in the TLV. For the 528 binding SID represented by a value, it indicates the type of binding 529 SID. The following BT values are defined: 531 o BT = 0: The binding SID is represented by a Sub-TLV (i.e., binding 532 SID Sub-TLV) in the TLV. A binding SID Sub-TLV is a SID/Label Sub- 533 TLV defined in [I-D.ietf-isis-segment-routing-extensions]. BT != 0 534 indicates that the binding SID is represented by a value. 536 o BT = 1: The binding SID value is a label, which is represented by 537 the 20 rightmost bits. The length of the value is 3 octets. 539 o BT = 2: The binding SID value is a 32-bit SID. The length of the 540 value is 4 octets. 542 SIDs Type (ST): 1 octet indicates whether the SIDs are represented by 543 Sub-TLVs or values included in the TLV. For the SIDs represented by 544 values, it indicates the type of SIDs. The following ST values are 545 defined: 547 o ST = 0: The SIDs are represented by Sub-TLVs (i.e., SID Sub-TLVs) 548 in the TLV. A SID Sub-TLV is an Adj-SID Sub-TLV, a Prefix-SID Sub- 549 TLV or a SID/Label Sub-TLV defined in 550 [I-D.ietf-isis-segment-routing-extensions]. ST != 0 indicates that 551 the SIDs are represented by values. 553 o ST = 1: Each of the SID values is a label, which is represented by 554 the 20 rightmost bits. The length of the value is 3 octets. 556 o ST = 2: Each of the SID values is a 32-bit SID. The length of the 557 value is 4 octets. 559 3. Building Proxy Forwarding Table 561 Figure 10 is used to illustrate the SR proxy forwarding approach. 562 Each node N has SRGB = [N000-N999]. RT1 is an ingress node of SR 563 domain. RT3 is a failure node. RT2 is a Point of Local Repair (PLR) 564 node, i.e., a proxy forwarding node. Three label stacks are shown in 565 the figure. Label Stack 1 uses only adjacency-SIDs and represents 566 the path RT1->RT2->RT3->RT4->RT5. Label Stack 2 uses only node-SIDs 567 and represents the ECMP-aware path RT1->RT3->RT4->RT5. Label Stack 3 568 uses a node-SID and a binding SID. The Binding-SID with label=100 at 569 RT3 represents the ECMP-aware path RT3->RT4->RT5. So Label Stack 3, 570 which consists of the node-SID for RT3 following by Binding-SID=100, 571 represents the ECMP-aware path RT1->RT3->RT4->RT5. 573 Node SID:2 Node SID:3 574 +-----+ +-----+ 575 | |----------+ | 576 / |RT2 | | RT3 |\ 577 / +-----+ +-----+ \ 578 / | \ /| \ 579 / | \ / | \ 580 / | \ / | \ 581 / | \ / | \ 582 / | \ / | \ 583 Node SID:1 | \ / | \Node SID:4 Node SID:5 584 +-----+ | \ / | +-----+ +-----+ 585 | | | X | | |-------| | 586 | RT1 | | / \ | | RT4 | | RT5 | 587 +-----+ | / \ | +-----+ +-----+ 588 \ | / \ | / 589 \ | / \ | / 590 \ | / \ | / 591 \ | / \ | / 592 \ | / \| / 593 \ |/ | / 594 \ +-----+ +-----+ / 595 \ | | | |/ 596 \ | RT6 |-----------| RT7 | 597 +-----+ +-----+ 598 Node SID:6 Node SID:7 600 +-----------------+ +--------------+ 601 | Node SRGB | | Adj-SID | +-------+ +-------+ +-------+ 602 +-----------------+ +--------------+ |Label | |Label | |Label | 603 | RT1:[1000-1999] | |RT1->RT2:10012| |Stack 1| |Stack 2| |Stack 3| 604 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 605 | RT2:[2000-2999] | |RT2->RT3:20023| | 10012 | | 1003 | | 1003 | 606 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 607 | RT3:[3000-3999] | |RT3->RT6:30036| | 20023 | | 3004 | | 100 | 608 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 609 | RT4:[4000=4999] | |RT3->RT7:30037| | 30034 | | 4005 | 100 is 610 +-----------------+ +--------------+ +-------+ +-------+ binding SID 611 | RT5:[5000-5999] | |RT3->RT4:30034| | 40045 | to 612 +-----------------+ +--------------+ +-------+ {30034,40045} 613 | RT6:[6000-6999] | |RT7->RT4:70074| 614 +-----------------+ +--------------+ 615 | RT7:[7000-7999] | |RT4->RT5:40045| 616 +-----------------+ +--------------+ 618 Figure 10: Topology of SR-TE Path 620 3.1. Advertising Proxy Forwarding 622 If the Point of Local Repair (PLR), for example, RT2, has the 623 capability to do a SR proxy forwarding for all its neighboring nodes, 624 it must advertise this capability. If the PLR can not do a SR proxy 625 forwarding for all its neighboring nodes, but for some of them, for 626 example, RT3, then it uses proxy Node SIDs TLV to advertise the 627 prefix-SID learned from RT3. The TLV contains the Sub-TLV/value for 628 the prefix/node SID of RT3 as a proxy SID. When RT3 fails, RT2 needs 629 to maintain the Sub-TLV/value for a period of time. When the proxy 630 forwarding table corresponding to the fault node is deleted (see 631 section 3.2), the Sub-TLV/value is withdrawn. The nodes in the 632 network (for example, RT1) learn the prefix/node SID TLV advertised 633 by RT3 and the proxy Node SIDs TLV advertised by RT2. When RT3 is 634 normal, the nodes prefer prefix/node SID TLV. When the RT3 fails, 635 the proxy prefix/node SIDs TLV advertised by RT2 is preferred. 637 3.2. Building Proxy Forwarding Table 639 A SR proxy node P needs to build an independent proxy forwarding 640 table for each neighbor N. The proxy forwarding table for node N 641 contains the following information: 643 1: Node N's SRGB range and the difference between the SRGB start 644 value of node P and that of node N; 646 2: All adjacency-SID of N and Node-SID of the node pointed to by node 647 N's adjacency-SID. 649 3: The binding-SID of N and the label stack associated with the 650 binding-SID. 652 Node P (PLR) uses a proxy forwarding table based on the next segment 653 to find a node N as a backup forwarding entry to the adj-SID and 654 Node-SID of node N. When node N fails, the proxy forwarding table 655 needs to be maintained for a period of time, which is recommended for 656 30 minutes. 658 Node RT3 in the topology of Figure 1 is node N, and node RT2 is node 659 P (PLR). RT2 builds the proxy forwarding table for RT3. The 660 structure of the table and how to build the table is a local 661 implementation issue. 663 4. Node Protection for Segment List 665 Segment Routing Traffic Engineering supports the creation of explicit 666 paths using adjacency-SIDs, node-SIDs, and binding-SIDs. The label 667 stack is a combination of one or more of adjacency-SIDs, node-SIDs, 668 and binding-SIDs. This Section shows how a proxy node uses the SR 669 proxy forwarding mechanism to protect traffic to the destination node 670 when the next segment of label stack is adjacency-SIDs, node-SIDs, or 671 binding-SIDs, respectively. 673 4.1. Next Segment is an Adjacency Segment 675 As shown in Figure 1, Label Stack 1 {10012, 20023, 30034, 40045} 676 represents SR-TE strict explicit path RT1->RT2->RT3->RT4->RT5. When 677 RT3 fails, node RT2 acts as a PLR, and uses next adj-SID (30034) of 678 the label stack to lookup the proxy forwarding table built by RT2 679 locally for RT3. The path returned is the label forwarding path to 680 RT3's next hop node RT4, which bypasses RT3. The specific steps are 681 as follows: 683 a. RT1 pops top adj-SID 10012, and forwards the packet to RT2; 685 b. RT2 uses the label 20023 to identify the next hop node RT3, which 686 has failed. RT2 pops label 20023 and queries the Proxy Forwarding 687 Table corresponding to RT3 with label 30034. The Proxy Forwarding 688 Table corresponding to RT3 returns an outgoing interface and label 689 stack representing a path to RT4 that does not pass through RT3. In 690 this case, outgoing interface to RT7 with label stack 7004, satisfies 691 this requirement. 693 c. So the packet leaves RT2 out the interface to RT7 with label 694 stack {7004, 40045}. RT4 forwards it to RT4, where the original path 695 is rejoined. 697 d. RT2 forwards packets to RT7. RT7 queries the local routing table 698 to forward the packet to RT4. 700 4.2. Next Segment is a Node Segment 702 As shown in Figure 1, Label Stack 2 {1003, 3004, 4005} represents SR- 703 TE loose path RT1->RT3->RT4->RT5, where 1003 is the node SID of RT3. 705 When the node RT3 fails, the proxy forwarding TLV advertised by the 706 RT2 is preferred to direct the traffic of the RT1 to the PLR node 707 RT2. Node RT2 acts as a PLR node and queries the proxy forwarding 708 table locally built for RT3. The path returned is the label 709 forwarding path to RT3's next hop node RT4, which bypasses RT3. The 710 specific steps are as follows: 712 a. RT1 swaps label 1003 to out-label 2003 to RT3. 714 b. RT2 receives the label forwarding packet whose top label of label 715 stack is 2003, and searches for the local Routing Table, the behavior 716 found is to lookup Proxy Forwarding table due to RT3 failure. 718 c. RT2 uses 2003 as the in-label to lookup Proxy Forwarding table, 719 and the query result is forwarding the packet to RT4. 721 d. Then RT2 queries the Routing Table to RT4, using the primary or 722 backup path to RT4. The next hop is RT7. 724 e. RT2 forwards the packet to RT7. RT7 queries the local routing 725 table to forward the packet to RT4. 727 f. After RT1 convergences, node SID 1003 is preferred to the proxy 728 SID implied/advertised by RT2. 730 4.3. Next Segment is a Binding Segment 732 As shown in Figure 1, Label Stack 3 {1003, 100} represents SR-TE 733 loose path RT1->RT3->RT4->RT5, where 100 is a Binding-SID, which 734 represents segment list {30034, 40045}. 736 When the node RT3 fails, the proxy forwarding SID implied or 737 advertised by the RT2 is preferred to forward the traffic of the RT1 738 to the PLR node RT2. Node RT2 acts as a PLR node and uses Binding- 739 SID to query the proxy forwarding table locally built for RT3. The 740 path returned is the label forwarding path to RT3's next hop node 741 (RT4), which bypasses RT3. The specific steps are as follows: 743 a. RT1 swaps label 1003 to out-label 2003 to RT3. 745 b. RT2 receives the label forwarding packet whose top label of label 746 stack is 2003, and searches for the local Routing Table, the behavior 747 found is to lookup Proxy Forwarding table due to RT3 failure. 749 c. RT2 uses Binding-SID:100 (label 2003 has pop) as the in-label to 750 lookup the Next Label record of the Proxy Forwarding Table, the 751 behavior found is to swap to Segment list {30034, 40045}. 753 d. RT2 swaps Binding-SID:100 to Segment list {30034, 40045}, and 754 uses the 3034 to lookup the Next Label record of the Proxy Forwarding 755 table again. The behavior found is to forward the packet to RT4. 757 e. RT2 queries the Routing Table to RT4, using primary or backup 758 path to RT4. The next hop is RT7. 760 f. RT2 forwards packets to RT7. RT7 queries the local routing table 761 to forward the packet to RT4. 763 5. Security Considerations 765 The extensions to OSPF and IS-IS described in this document result in 766 two types of behaviors in data plane when a node in a network fails. 767 One is that for a node, which is a upstream (except for the direct 768 upstream) node of the failed node along a SR-TE path, it continues to 769 send the traffic to the failed node along the SR-TE path for an 770 extended period of time. The other is that for a node, which is the 771 direct upstream node of the failed node, it fast re-routes the 772 traffic around the failed node to the direct downstream node of the 773 failed node along the SR-TE path. These behaviors are internal to a 774 network and should not cause extra security issues. 776 6. IANA Considerations 778 6.1. OSPFv2 780 Under Subregistry Name "OSPF Router Functional Capability Bits" 781 within the "Open Shortest Path First v2 (OSPFv2) Parameters" 782 [RFC7770], IANA is requested to assign one bit for Proxy Forwarding 783 Capability as follows: 785 +============+==================+===================+ 786 | Bit number | Capability Name | Reference | 787 +============+==================+===================+ 788 | 31 | Proxy Forwarding | This document | 789 +------------+------------------+-------------------+ 791 Under Registry Name "OSPFv2 Extended Prefix Opaque LSA TLVs" 792 [RFC7684], IANA is requested to assign one new TLV value for OSPF 793 Proxy Node SIDs as follows: 795 +============+=====================+================+ 796 | TLV Value | TLV Name | Reference | 797 +============+=====================+================+ 798 | 2 | Proxy Node SIDs TLV | This document | 799 +------------+---------------------+----------------+ 801 Under Registry Name "Opaque Link-State Advertisements (LSA) Option 802 Types" [RFC5250], IANA is requested to assign new Opaque Type 803 registry values for Binding Segment LSA as follows: 805 +================+==================+================+ 806 | Registry Value | Opaque Type | Reference | 807 +================+==================+================+ 808 | 10 | Binding Segment | This document | 809 +----------------+------------------+----------------+ 811 IANA is requested to create and maintain new registries: 813 o OSPFv2 Binding Segment Opaque LSA TLVs 815 Initial values for the registry are given below. The future 816 assignments are to be made through IETF Review [RFC5226]. 818 Value TLV Name Definition 819 ----- ----------------------- ---------- 820 0 Reserved 821 1 Binding Segment TLV This Document 822 2-32767 Unassigned 823 32768-65535 Reserved 825 6.2. OSPFv3 827 Under Registry Name "OSPFv3 LSA Function Codes", IANA is requested to 828 assign new registry values for Binding Segment LSA as follows: 830 +========+========================+================+ 831 | Value | LSA Function Code Name | Reference | 832 +========+========================+================+ 833 | 16 | Binding Segment LSA | This document | 834 +--------+------------------------+----------------+ 836 IANA is requested to create and maintain new registries: 838 o OSPFv3 Binding Segment LSA TLVs 840 Initial values for the registry are given below. The future 841 assignments are to be made through IETF Review [RFC5226]. 843 Value TLV Name Definition 844 ----- ----------------------- ---------- 845 0 Reserved 846 1 Binding Segment TLV This Document 847 2-32767 Unassigned 848 32768-65535 Reserved 850 6.3. IS-IS 852 Under Registration "Segment Routing Capability" in the "sub-TLVs for 853 TLV 242" registry [I-D.ietf-isis-segment-routing-extensions], IANA is 854 requested to assign one bit flag for Proxy Forwarding Capability as 855 follows: 857 +============+=======================+===============+ 858 | Bit number | Capability Name | Reference | 859 +============+=======================+===============+ 860 | 2 | Proxy Forwarding (PF) | This document | 861 +------------+-----------------------+---------------+ 863 Under Registration "Segment Identifier/Label Binding TLV 149" 864 [I-D.ietf-isis-segment-routing-extensions], IANA is requested to 865 assign one bit P-Flag as follows: 867 +============+=================+===============+ 868 | Bit number | Flag Name | Reference | 869 +============+=================+===============+ 870 | 5 | P-Flag | This document | 871 +------------+-----------------+---------------+ 873 Under Registry Name: IS-IS TLV Codepoints, IANA is requested to 874 assign one new TLV value for IS-IS Binding Segment as follows: 876 +========+======================+===============+ 877 | Value | TLV Name | Reference | 878 +========+======================+===============+ 879 | 152 | Binding Segment TLV | This Document | 880 +--------+----------------------+---------------+ 882 7. Acknowledgements 884 The authors would like to thank Peter Psenak, Acee Lindem, Les 885 Ginsberg, Bruno Decraene and Jeff Tantsura for their comments to this 886 work. 888 8. References 890 8.1. Normative References 892 [I-D.ietf-isis-segment-routing-extensions] 893 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 894 Gredler, H., and B. Decraene, "IS-IS Extensions for 895 Segment Routing", draft-ietf-isis-segment-routing- 896 extensions-25 (work in progress), May 2019. 898 [I-D.ietf-ospf-segment-routing-extensions] 899 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 900 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 901 Extensions for Segment Routing", draft-ietf-ospf-segment- 902 routing-extensions-27 (work in progress), December 2018. 904 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 905 Requirement Levels", BCP 14, RFC 2119, 906 DOI 10.17487/RFC2119, March 1997, 907 . 909 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 910 IANA Considerations Section in RFCs", RFC 5226, 911 DOI 10.17487/RFC5226, May 2008, 912 . 914 [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The 915 OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250, 916 July 2008, . 918 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 919 Scope Link State PDUs (LSPs)", RFC 7356, 920 DOI 10.17487/RFC7356, September 2014, 921 . 923 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 924 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 925 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 926 2015, . 928 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 929 S. Shaffer, "Extensions to OSPF for Advertising Optional 930 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 931 February 2016, . 933 8.2. Informative References 935 [I-D.bashandy-rtgwg-segment-routing-ti-lfa] 936 Bashandy, A., Filsfils, C., Decraene, B., Litkowski, S., 937 Francois, P., daniel.voyer@bell.ca, d., Clad, F., and P. 938 Camarillo, "Topology Independent Fast Reroute using 939 Segment Routing", draft-bashandy-rtgwg-segment-routing-ti- 940 lfa-05 (work in progress), October 2018. 942 [I-D.hegde-spring-node-protection-for-sr-te-paths] 943 Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, 944 "Node Protection for SR-TE Paths", draft-hegde-spring- 945 node-protection-for-sr-te-paths-05 (work in progress), 946 July 2019. 948 [I-D.ietf-spring-segment-routing-policy] 949 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 950 bogdanov@google.com, b., and P. Mattes, "Segment Routing 951 Policy Architecture", draft-ietf-spring-segment-routing- 952 policy-03 (work in progress), May 2019. 954 [I-D.sivabalan-pce-binding-label-sid] 955 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 956 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 957 in PCE-based Networks.", draft-sivabalan-pce-binding- 958 label-sid-07 (work in progress), July 2019. 960 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 961 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 962 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 963 2009, . 965 Authors' Addresses 967 Zhibo Hu 968 Huawei Technologies 969 Huawei Bld., No.156 Beiqing Rd. 970 Beijing 100095 971 China 973 Email: huzhibo@huawei.com 975 Huaimo Chen 976 Futurewei 977 Boston, MA 978 USA 980 Email: Huaimo.chen@futurewei.com 982 Junda Yao 983 Huawei Technologies 984 Huawei Bld., No.156 Beiqing Rd. 985 Beijing 100095 986 China 988 Email: yaojunda@huawei.com 989 Chris Bowers 990 Juniper Networks 991 1194 N. Mathilda Ave. 992 Sunnyvale, CA 94089 993 USA 995 Email: cbowers@juniper.net 997 Yongqing 998 China Telecom 999 109, West Zhongshan Road, Tianhe District 1000 Guangzhou 510000 1001 China 1003 Email: zhuyq.gd@chinatelecom.cn