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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: January 11, 2021 Futurewei 6 J. Yao 7 Huawei Technologies 8 C. Bowers 9 Juniper Networks 10 Y. Zhu 11 China Telecom 12 July 10, 2020 14 SR-TE Path Midpoint Protection 15 draft-hu-spring-segment-routing-proxy-forwarding-09 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.ietf-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 January 11, 2021. 60 Copyright Notice 62 Copyright (c) 2020 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.ietf-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 the prefix/node SID of node N to node P when node N fails, and 197 node P will do a SR proxy forwarding for node N and forwarding the 198 traffic to its final destination without going through node N. After 199 node N fails, node X will keep the FIB entry to the proxy prefix/node 200 SID of node N for a given period of time. 202 If node P can not do a SR proxy forwarding for all its neighboring 203 nodes, but for some of them, then it advertises the node SID of each 204 of the nodes as a proxy node SID, indicating that it is able to do 205 proxy forwarding for the node SID. 207 A new TLV, called Proxy Node SIDs TLV, is defined for node P to 208 advertise the node SIDs of some of its neighboring nodes. It has the 209 format as shown in Figure 2. 211 0 1 2 3 212 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 1 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | Type (TBD1) | Length | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | Node SID Sub-TLVs | 217 : : 218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 Figure 2: OSPF Proxy Node SIDs TLV 222 The Type (TBD1) is to be assigned by IANA. The TLV contains a number 223 of Node SID Sub-TLVs. The Length is the total size of the Node SID 224 Sub-TLVs included in the TLV. A Node SID Sub-TLV is the Prefix SID 225 Sub-TLV defined in [I-D.ietf-ospf-segment-routing-extensions]. 227 A proxy forwarding node P originates an Extended Prefix Opaque LSA 228 containing this new TLV. The TLV includes the Node SID Sub-TLVs for 229 the node SIDs of some of P's neighboring nodes. For each of some of 230 P's neighboring nodes, the Node SID Sub-TLV for its prefix/node SID 231 is included the TLV. This prefix/node SID is called a proxy prefix/ 232 node SID. 234 A proxy forwarding node will originate an Extended Prefix Opaque LSA, 235 which includes a Proxy Node SIDs TLV. The format of the LSA is shown 236 in Figure 3. 238 For a proxy forwarding node P, having a number of neighboring nodes, 239 P originates and maintains an Extended Prefix Opaque LSA, which 240 includes a Proxy Node SIDs TLV. The TLV contains the Prefix/Node SID 241 Sub-TLV for each of some of the neighboring nodes after node P 242 creates the corresponding proxy forwarding entries for protecting the 243 failure of some of the neighboring nodes. 245 0 1 2 3 246 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 1 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | LS age | Options | LS Type | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Opaque Type(7)| Opaque ID | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Advertising Router | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | LS sequence number | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | LS checksum | Length | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | | 259 : TLVs : 260 : (including Proxy Node SIDs TLV) : 261 | | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 Figure 3: OSPFv2 Extended Prefix Opaque LSA 266 When an neighboring node fails, P maintains the LSA with the TLV 267 containing the Prefix/Node SID Sub-TLV for the neighboring node for a 268 given period of time. After the given period of time, the Prefix/ 269 Node SID Sub-TLV for the neighboring node is removed from the TLV in 270 the LSA and then after a given time the corresponding proxy 271 forwarding entries for protecting the failure of the neighboring node 272 is removed. 274 For a node X in the network, it learns the prefix/node SID of node N 275 and the proxy prefix/node SID of node N. The former is originated 276 and advertised by node N, and the latter is originated and advertised 277 by the proxy forwarding node P of node N. Note that the proxy 278 Prefix/Node SID Sub-TLV for node N does not contain a prefix of node 279 N, and the prefix is the prefix associated with the prefix/node SID 280 of node N originated by node N. 282 In normal operations, node X prefers to use the prefix/node SID of 283 node N. When node N fails, node X prefers to use the proxy prefix/ 284 node SID of node N. Thus node X will forward the traffic targeting 285 to node N to node P when node N fails, and node P will do a proxy 286 forwarding for node N and forwarding the traffic to its destination 287 without going through node N. 289 2.1.2. Advertising Binding Segment 291 For a binding segment (or binding for short) on a node A, which 292 consists of a binding SID and a list of segments, node A advertises 293 an LSA containing the binding (i.e., the binding SID and the list of 294 the segments). The LSA is advertised only to each of the node A's 295 neighboring nodes. For OSPFv2, the LSA is a opaque LSA of LS type 9 296 (i.e., a link local scope LSA). 298 A binding segment is represented by binding segment TLV of the format 299 as shown in Figure 4. 301 0 1 2 3 302 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 1 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 | Type (TBD2) | Length | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | Reserved |BindingSID Type| SIDs Type | 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 308 ~ Binding SID Sub-TLV/value ~ 309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 310 ~ SID Sub-TLVs/values ~ 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 Figure 4: OSPF Binding Segment TLV 315 It comprises a binding SID and a list of segments (SIDs). The fields 316 of this TLV are defined as follows: 318 Type: 2 octets, its value (TBD2) is to be assigned by IANA. 320 Length: 2 octets, its value is (4 + length of Sub-TLVs/values). 322 Binding SID Type (BT): 1 octet indicates whether the binding SID is 323 represented by a Sub-TLV or a value included in the TLV. For the 324 binding SID represented by a value, it indicates the type of binding 325 SID. The following BT values are defined: 327 o BT = 0: The binding SID is represented by a Sub-TLV (i.e., Binding 328 SID Sub-TLV) in the TLV. A binding SID Sub-TLV is a SID/Label Sub- 329 TLV defined in [I-D.ietf-ospf-segment-routing-extensions]. BT != 0 330 indicates that the binding SID is represented by a value. 332 o BT = 1: The binding SID value is a label, which is represented by 333 the 20 rightmost bits. The length of the value is 3 octets. 335 o BT = 2: The binding SID value is a 32-bit SID. The length of the 336 value is 4 octets. 338 SIDs Type (ST): 1 octet indicates whether the list of segments (SIDs) 339 are represented by Sub-TLVs or values included in the TLV. For the 340 SIDs represented by values, it indicates the type of SIDs. The 341 following ST values are defined: 343 o ST = 0: The SIDs are represented by Sub-TLVs (i.e., SID Sub-TLVs) 344 in the TLV. A SID Sub-TLV is an Adj-SID Sub-TLV, a Prefix-SID Sub- 345 TLV or a SID/Label Sub-TLV defined in 346 [I-D.ietf-ospf-segment-routing-extensions]. ST != 0 indicates that 347 the SIDs are represented by values. 349 o ST = 1: Each of the SID values is a label, which is represented by 350 the 20 rightmost bits. The length of the value is 3 octets. 352 o ST = 2: Each of the SID values is a 32-bit SID. The length of the 353 value is 4 octets. 355 The opaque LSA of LS Type 9 containing the binding segment (i.e., the 356 binding SID and the list of the segments) has the format as shown in 357 Figure 5. It may have Opaque Type of x (the exact type is to be 358 assigned by IANA) for Binding Segment Opaque LSA. 360 0 1 2 3 361 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 1 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | LS age | Options | LS Type (9) | 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 | Opaque Type(x)| Opaque ID | 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | Advertising Router | 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 369 | LS sequence number | 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | LS checksum | Length | 372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 | | 374 : Binding Segment TLVs : 375 | | 376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 378 Figure 5: OSPFv2 Binding Segment Opaque LSA 380 For every binding on a node A, the LSA originated by A contains a 381 binding segment TLV for it. 383 For node A running OSPFv3, it originates a link-local scoping LSA of 384 a new LSA function code (TBD3) containing binding segment TLVs for 385 the bindings on it. The format of the LSA is illustrated in 386 Figure 6. 388 0 1 2 3 389 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 1 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | LS age |0|0|0| BS-LSA (TBD3) | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | Link State ID | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | Advertising Router | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | LS Sequence Number | 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | LS checksum | Length | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | | 402 : Binding Segment TLVs : 403 | | 404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 Figure 6: OSPFv3 Binding Segment Opaque LSA 408 The U-bit is set to 0, and the scope is set to 00 for link-local 409 scoping. 411 2.2. Extensions to IS-IS 413 2.2.1. Advertising Proxy Forwarding 415 When a node P has the capability to do a SR proxy forwarding for its 416 neighboring nodes for protecting the failures of them, node P 417 advertises its SR proxy forwarding capability in its LSP, which 418 contains a Router Capability TLV of Type 242 including a SR 419 capabilities sub-TLV of sub-Type 2. 421 One bit (called PF bit as shown in Figure 7) in the Flags field of 422 the SR capabilities sub-TLV is defined to indicate node P's SR proxy 423 forwarding capability. When this bit is set to one by node P, it 424 indicates that node P is capable of doing a SR proxy forwarding for 425 its neighboring nodes. 427 0 1 2 3 428 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 1 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 | Type (2) | Length | Flags | 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 | Range | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 // SID/Label Sub-TLV (variable) // 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 0 1 2 3 4 5 6 7 438 +--+--+--+--+--+--+--+--+ 439 | I| V|PF| | 440 +--+--+--+--+--+--+--+--+ 441 Flags 443 Figure 7: SR Capabilities sub-TLV 445 If node P can not do a SR proxy forwarding for all its neighboring 446 nodes, but for some of them, then it advertises the node SID of each 447 of the nodes as a proxy node SID, indicating that it is able to do 448 proxy forwarding for the node SID. 450 The IS-IS SID/Label Binding TLV (suggested value 149) is defined in 451 [I-D.ietf-isis-segment-routing-extensions]. A Proxy Forwarder uses 452 the SID/Label Binding TLV to advertise the node SID of its 453 neighboring node. The Flags field of the SID/Label Binding TLV is 454 extended to include a P flag as shown in Figure 8. The prefix/node 455 SID in prefix/node SID Sub-TLV included in SID/Label Binding TLV is 456 identified as a proxy forwarding prefix/node SID. 458 0 1 2 3 459 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 1 460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 461 | Type | Length | Flags | RESERVED | 462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 463 | Range | Prefix Length | Prefix | 464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 465 // Prefix (continued, variable) // 466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 467 | SubTLVs (variable) | 468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 0 1 2 3 4 5 6 7 471 +-+-+-+-+-+-+-+-+ 472 |F|M|S|D|A|P| | 473 +-+-+-+-+-+-+-+-+ 474 Flags 476 Figure 8: SID/Label Binding TLV 478 Where: 480 P-Flag: Proxy forwarding flag. If set, this prefix/node SID is 481 advertised by the proxy node. This TLV is used to announce that the 482 node has the ability to proxy forward the prefix/node SID. 484 When the P-flag is set in the SID/Label Binding TLV, the following 485 usage rules apply. 487 The Range, Prefix Length and Prefix field are not used. They should 488 be set to zero on transmission and ignored on receipt. 490 SID/Label Binding TLV contains a number of prefix/node SID Sub-TLVs. 491 The TLV advertised by a proxy forwarding node P contains prefix/node 492 SID Sub-TLVs for the node SIDs of P's neighbor nodes. Each of the 493 Sub-TLVs is a prefix/node SID Sub-TLV defined in 494 [I-D.ietf-isis-segment-routing-extensions]. From the SID in a 495 prefix/node SID Sub-TLV advertised by the Proxy Forwarding node, its 496 prefix can be obtained through matching corresponding prefix/node SID 497 advertised by the neighbor/protected node using TLV-135 (or 235, 236, 498 or 237) together with the prefix/node SID Sub-TLV. 500 2.2.2. Advertising Binding Segment 502 [I-D.ietf-spring-segment-routing-policy] has defined the usage of 503 binding-SID. For supporting binding SID proxy forwarding, a new IS- 504 IS TLV, called Binding Segment TLV, is defined. It contains a 505 binding SID and a list of segments (SIDs). This TLV may be 506 advertised in IS-IS Hello (IIH) PDUs, LSPs, or in Circuit Scoped Link 507 State PDUs (CS-LSP) [RFC7356]. Its format is shown in Figure 9. 509 0 1 2 3 510 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 1 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 | Type | Length |BindingSID Type| SIDs Type | 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 ~ Binding SID value/Sub-TLV ~ 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 ~ SID values/Sub-TLVs ~ 517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 Figure 9: IS-IS Binding Segment TLV 521 The fields of this TLV are defined as follows: 523 Type: 1 octet Suggested value 152 (to be assigned by IANA) 525 Length: 1 octet (2 + length of Sub-TLVs/values). 527 Binding SID Type (BT): 1 octet indicates whether the binding SID is 528 represented by a Sub-TLV or a value included in the TLV. For the 529 binding SID represented by a value, it indicates the type of binding 530 SID. The following BT values are defined: 532 o BT = 0: The binding SID is represented by a Sub-TLV (i.e., binding 533 SID Sub-TLV) in the TLV. A binding SID Sub-TLV is a SID/Label Sub- 534 TLV defined in [I-D.ietf-isis-segment-routing-extensions]. BT != 0 535 indicates that the binding SID is represented by a value. 537 o BT = 1: The binding SID value is a label, which is represented by 538 the 20 rightmost bits. The length of the value is 3 octets. 540 o BT = 2: The binding SID value is a 32-bit SID. The length of the 541 value is 4 octets. 543 SIDs Type (ST): 1 octet indicates whether the SIDs are represented by 544 Sub-TLVs or values included in the TLV. For the SIDs represented by 545 values, it indicates the type of SIDs. The following ST values are 546 defined: 548 o ST = 0: The SIDs are represented by Sub-TLVs (i.e., SID Sub-TLVs) 549 in the TLV. A SID Sub-TLV is an Adj-SID Sub-TLV, a Prefix-SID Sub- 550 TLV or a SID/Label Sub-TLV defined in 551 [I-D.ietf-isis-segment-routing-extensions]. ST != 0 indicates that 552 the SIDs are represented by values. 554 o ST = 1: Each of the SID values is a label, which is represented by 555 the 20 rightmost bits. The length of the value is 3 octets. 557 o ST = 2: Each of the SID values is a 32-bit SID. The length of the 558 value is 4 octets. 560 3. Building Proxy Forwarding Table 562 Figure 10 is used to illustrate the SR proxy forwarding approach. 563 Each node N has SRGB = [N000-N999]. RT1 is an ingress node of SR 564 domain. RT3 is a failure node. RT2 is a Point of Local Repair (PLR) 565 node, i.e., a proxy forwarding node. Three label stacks are shown in 566 the figure. Label Stack 1 uses only adjacency-SIDs and represents 567 the path RT1->RT2->RT3->RT4->RT5. Label Stack 2 uses only node-SIDs 568 and represents the ECMP-aware path RT1->RT3->RT4->RT5. Label Stack 3 569 uses a node-SID and a binding SID. The Binding-SID with label=100 at 570 RT3 represents the ECMP-aware path RT3->RT4->RT5. So Label Stack 3, 571 which consists of the node-SID for RT3 following by Binding-SID=100, 572 represents the ECMP-aware path RT1->RT3->RT4->RT5. 574 Node SID:2 Node SID:3 575 +-----+ +-----+ 576 | |----------+ | 577 / |RT2 | | RT3 |\ 578 / +-----+ +-----+ \ 579 / | \ /| \ 580 / | \ / | \ 581 / | \ / | \ 582 / | \ / | \ 583 / | \ / | \ 584 Node SID:1 | \ / | \Node SID:4 Node SID:5 585 +-----+ | \ / | +-----+ +-----+ 586 | | | X | | |-------| | 587 | RT1 | | / \ | | RT4 | | RT5 | 588 +-----+ | / \ | +-----+ +-----+ 589 \ | / \ | / 590 \ | / \ | / 591 \ | / \ | / 592 \ | / \ | / 593 \ | / \| / 594 \ |/ | / 595 \ +-----+ +-----+ / 596 \ | | | |/ 597 \ | RT6 |-----------| RT7 | 598 +-----+ +-----+ 599 Node SID:6 Node SID:7 601 +-----------------+ +--------------+ 602 | Node SRGB | | Adj-SID | +-------+ +-------+ +-------+ 603 +-----------------+ +--------------+ |Label | |Label | |Label | 604 | RT1:[1000-1999] | |RT1->RT2:10012| |Stack 1| |Stack 2| |Stack 3| 605 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 606 | RT2:[2000-2999] | |RT2->RT3:20023| | 10012 | | 1003 | | 1003 | 607 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 608 | RT3:[3000-3999] | |RT3->RT6:30036| | 20023 | | 3004 | | 100 | 609 +-----------------+ +--------------+ +-------+ +-------+ +-------+ 610 | RT4:[4000=4999] | |RT3->RT7:30037| | 30034 | | 4005 | 100 is 611 +-----------------+ +--------------+ +-------+ +-------+ binding SID 612 | RT5:[5000-5999] | |RT3->RT4:30034| | 40045 | to 613 +-----------------+ +--------------+ +-------+ {30034,40045} 614 | RT6:[6000-6999] | |RT7->RT4:70074| 615 +-----------------+ +--------------+ 616 | RT7:[7000-7999] | |RT4->RT5:40045| 617 +-----------------+ +--------------+ 619 Figure 10: Topology of SR-TE Path 621 3.1. Advertising Proxy Forwarding 623 If the Point of Local Repair (PLR), for example, RT2, has the 624 capability to do a SR proxy forwarding for all its neighboring nodes, 625 it must advertise this capability. If the PLR can not do a SR proxy 626 forwarding for all its neighboring nodes, but for some of them, for 627 example, RT3, then it uses proxy Node SIDs TLV to advertise the 628 prefix-SID learned from RT3. The TLV contains the Sub-TLV/value for 629 the prefix/node SID of RT3 as a proxy SID. When RT3 fails, RT2 needs 630 to maintain the Sub-TLV/value for a period of time. When the proxy 631 forwarding table corresponding to the fault node is deleted (see 632 section 3.2), the Sub-TLV/value is withdrawn. The nodes in the 633 network (for example, RT1) learn the prefix/node SID TLV advertised 634 by RT3 and the proxy Node SIDs TLV advertised by RT2. When RT3 is 635 normal, the nodes prefer prefix/node SID TLV. When the RT3 fails, 636 the proxy prefix/node SIDs TLV advertised by RT2 is preferred. 638 3.2. Building Proxy Forwarding Table 640 A SR proxy node P needs to build an independent proxy forwarding 641 table for each neighbor N. The proxy forwarding table for node N 642 contains the following information: 644 1: Node N's SRGB range and the difference between the SRGB start 645 value of node P and that of node N; 647 2: All adjacency-SID of N and Node-SID of the node pointed to by node 648 N's adjacency-SID. 650 3: The binding-SID of N and the label stack associated with the 651 binding-SID. 653 Node P (PLR) uses a proxy forwarding table based on the next segment 654 to find a node N as a backup forwarding entry to the adj-SID and 655 Node-SID of node N. When node N fails, the proxy forwarding table 656 needs to be maintained for a period of time, which is recommended for 657 30 minutes. 659 Node RT3 in the topology of Figure 1 is node N, and node RT2 is node 660 P (PLR). RT2 builds the proxy forwarding table for RT3. The 661 structure of the table and how to build the table is a local 662 implementation issue. 664 4. Node Protection for Segment List 666 Segment Routing Traffic Engineering supports the creation of explicit 667 paths using adjacency-SIDs, node-SIDs, and binding-SIDs. The label 668 stack is a combination of one or more of adjacency-SIDs, node-SIDs, 669 and binding-SIDs. This Section shows how a proxy node uses the SR 670 proxy forwarding mechanism to protect traffic to the destination node 671 when the next segment of label stack is adjacency-SIDs, node-SIDs, or 672 binding-SIDs, respectively. 674 4.1. Next Segment is an Adjacency Segment 676 As shown in Figure 1, Label Stack 1 {10012, 20023, 30034, 40045} 677 represents SR-TE strict explicit path RT1->RT2->RT3->RT4->RT5. When 678 RT3 fails, node RT2 acts as a PLR, and uses next adj-SID (30034) of 679 the label stack to lookup the proxy forwarding table built by RT2 680 locally for RT3. The path returned is the label forwarding path to 681 RT3's next hop node RT4, which bypasses RT3. The specific steps are 682 as follows: 684 a. RT1 pops top adj-SID 10012, and forwards the packet to RT2; 686 b. RT2 uses the label 20023 to identify the next hop node RT3, which 687 has failed. RT2 pops label 20023 and queries the Proxy Forwarding 688 Table corresponding to RT3 with label 30034. The Proxy Forwarding 689 Table corresponding to RT3 returns an outgoing interface and label 690 stack representing a path to RT4 that does not pass through RT3. In 691 this case, outgoing interface to RT7 with label stack 7004, satisfies 692 this requirement. 694 c. So the packet leaves RT2 out the interface to RT7 with label 695 stack {7004, 40045}. RT4 forwards it to RT4, where the original path 696 is rejoined. 698 d. RT2 forwards packets to RT7. RT7 queries the local routing table 699 to forward the packet to RT4. 701 4.2. Next Segment is a Node Segment 703 As shown in Figure 1, Label Stack 2 {1003, 3004, 4005} represents SR- 704 TE loose path RT1->RT3->RT4->RT5, where 1003 is the node SID of RT3. 706 When the node RT3 fails, the proxy forwarding TLV advertised by the 707 RT2 is preferred to direct the traffic of the RT1 to the PLR node 708 RT2. Node RT2 acts as a PLR node and queries the proxy forwarding 709 table locally built for RT3. The path returned is the label 710 forwarding path to RT3's next hop node RT4, which bypasses RT3. The 711 specific steps are as follows: 713 a. RT1 swaps label 1003 to out-label 2003 to RT3. 715 b. RT2 receives the label forwarding packet whose top label of label 716 stack is 2003, and searches for the local Routing Table, the behavior 717 found is to lookup Proxy Forwarding table due to RT3 failure. 719 c. RT2 uses 2003 as the in-label to lookup Proxy Forwarding table, 720 and the query result is forwarding the packet to RT4. 722 d. Then RT2 queries the Routing Table to RT4, using the primary or 723 backup path to RT4. The next hop is RT7. 725 e. RT2 forwards the packet to RT7. RT7 queries the local routing 726 table to forward the packet to RT4. 728 f. After RT1 convergences, node SID 1003 is preferred to the proxy 729 SID implied/advertised by RT2. 731 4.3. Next Segment is a Binding Segment 733 As shown in Figure 1, Label Stack 3 {1003, 100} represents SR-TE 734 loose path RT1->RT3->RT4->RT5, where 100 is a Binding-SID, which 735 represents segment list {30034, 40045}. 737 When the node RT3 fails, the proxy forwarding SID implied or 738 advertised by the RT2 is preferred to forward the traffic of the RT1 739 to the PLR node RT2. Node RT2 acts as a PLR node and uses Binding- 740 SID to query the proxy forwarding table locally built for RT3. The 741 path returned is the label forwarding path to RT3's next hop node 742 (RT4), which bypasses RT3. The specific steps are as follows: 744 a. RT1 swaps label 1003 to out-label 2003 to RT3. 746 b. RT2 receives the label forwarding packet whose top label of label 747 stack is 2003, and searches for the local Routing Table, the behavior 748 found is to lookup Proxy Forwarding table due to RT3 failure. 750 c. RT2 uses Binding-SID:100 (label 2003 has pop) as the in-label to 751 lookup the Next Label record of the Proxy Forwarding Table, the 752 behavior found is to swap to Segment list {30034, 40045}. 754 d. RT2 swaps Binding-SID:100 to Segment list {30034, 40045}, and 755 uses the 3034 to lookup the Next Label record of the Proxy Forwarding 756 table again. The behavior found is to forward the packet to RT4. 758 e. RT2 queries the Routing Table to RT4, using primary or backup 759 path to RT4. The next hop is RT7. 761 f. RT2 forwards packets to RT7. RT7 queries the local routing table 762 to forward the packet to RT4. 764 5. Security Considerations 766 The extensions to OSPF and IS-IS described in this document result in 767 two types of behaviors in data plane when a node in a network fails. 768 One is that for a node, which is a upstream (except for the direct 769 upstream) node of the failed node along a SR-TE path, it continues to 770 send the traffic to the failed node along the SR-TE path for an 771 extended period of time. The other is that for a node, which is the 772 direct upstream node of the failed node, it fast re-routes the 773 traffic around the failed node to the direct downstream node of the 774 failed node along the SR-TE path. These behaviors are internal to a 775 network and should not cause extra security issues. 777 6. IANA Considerations 779 6.1. OSPFv2 781 Under Subregistry Name "OSPF Router Functional Capability Bits" 782 within the "Open Shortest Path First v2 (OSPFv2) Parameters" 783 [RFC7770], IANA is requested to assign one bit for Proxy Forwarding 784 Capability as follows: 786 +============+==================+===================+ 787 | Bit number | Capability Name | Reference | 788 +============+==================+===================+ 789 | 31 | Proxy Forwarding | This document | 790 +------------+------------------+-------------------+ 792 Under Registry Name "OSPFv2 Extended Prefix Opaque LSA TLVs" 793 [RFC7684], IANA is requested to assign one new TLV value for OSPF 794 Proxy Node SIDs as follows: 796 +============+=====================+================+ 797 | TLV Value | TLV Name | Reference | 798 +============+=====================+================+ 799 | 2 | Proxy Node SIDs TLV | This document | 800 +------------+---------------------+----------------+ 802 Under Registry Name "Opaque Link-State Advertisements (LSA) Option 803 Types" [RFC5250], IANA is requested to assign new Opaque Type 804 registry values for Binding Segment LSA as follows: 806 +================+==================+================+ 807 | Registry Value | Opaque Type | Reference | 808 +================+==================+================+ 809 | 10 | Binding Segment | This document | 810 +----------------+------------------+----------------+ 812 IANA is requested to create and maintain new registries: 814 o OSPFv2 Binding Segment Opaque LSA TLVs 816 Initial values for the registry are given below. The future 817 assignments are to be made through IETF Review [RFC5226]. 819 Value TLV Name Definition 820 ----- ----------------------- ---------- 821 0 Reserved 822 1 Binding Segment TLV This Document 823 2-32767 Unassigned 824 32768-65535 Reserved 826 6.2. OSPFv3 828 Under Registry Name "OSPFv3 LSA Function Codes", IANA is requested to 829 assign new registry values for Binding Segment LSA as follows: 831 +========+========================+================+ 832 | Value | LSA Function Code Name | Reference | 833 +========+========================+================+ 834 | 16 | Binding Segment LSA | This document | 835 +--------+------------------------+----------------+ 837 IANA is requested to create and maintain new registries: 839 o OSPFv3 Binding Segment LSA TLVs 841 Initial values for the registry are given below. The future 842 assignments are to be made through IETF Review [RFC5226]. 844 Value TLV Name Definition 845 ----- ----------------------- ---------- 846 0 Reserved 847 1 Binding Segment TLV This Document 848 2-32767 Unassigned 849 32768-65535 Reserved 851 6.3. IS-IS 853 Under Registration "Segment Routing Capability" in the "sub-TLVs for 854 TLV 242" registry [I-D.ietf-isis-segment-routing-extensions], IANA is 855 requested to assign one bit flag for Proxy Forwarding Capability as 856 follows: 858 +============+=======================+===============+ 859 | Bit number | Capability Name | Reference | 860 +============+=======================+===============+ 861 | 2 | Proxy Forwarding (PF) | This document | 862 +------------+-----------------------+---------------+ 864 Under Registration "Segment Identifier/Label Binding TLV 149" 865 [I-D.ietf-isis-segment-routing-extensions], IANA is requested to 866 assign one bit P-Flag as follows: 868 +============+=================+===============+ 869 | Bit number | Flag Name | Reference | 870 +============+=================+===============+ 871 | 5 | P-Flag | This document | 872 +------------+-----------------+---------------+ 874 Under Registry Name: IS-IS TLV Codepoints, IANA is requested to 875 assign one new TLV value for IS-IS Binding Segment as follows: 877 +========+======================+===============+ 878 | Value | TLV Name | Reference | 879 +========+======================+===============+ 880 | 152 | Binding Segment TLV | This Document | 881 +--------+----------------------+---------------+ 883 7. Acknowledgements 885 The authors would like to thank Peter Psenak, Acee Lindem, Les 886 Ginsberg, Bruno Decraene and Jeff Tantsura for their comments to this 887 work. 889 8. References 891 8.1. Normative References 893 [I-D.ietf-isis-segment-routing-extensions] 894 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 895 Gredler, H., and B. Decraene, "IS-IS Extensions for 896 Segment Routing", draft-ietf-isis-segment-routing- 897 extensions-25 (work in progress), May 2019. 899 [I-D.ietf-ospf-segment-routing-extensions] 900 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 901 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 902 Extensions for Segment Routing", draft-ietf-ospf-segment- 903 routing-extensions-27 (work in progress), December 2018. 905 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 906 Requirement Levels", BCP 14, RFC 2119, 907 DOI 10.17487/RFC2119, March 1997, 908 . 910 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 911 IANA Considerations Section in RFCs", RFC 5226, 912 DOI 10.17487/RFC5226, May 2008, 913 . 915 [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The 916 OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250, 917 July 2008, . 919 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 920 Scope Link State PDUs (LSPs)", RFC 7356, 921 DOI 10.17487/RFC7356, September 2014, 922 . 924 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 925 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 926 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 927 2015, . 929 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 930 S. Shaffer, "Extensions to OSPF for Advertising Optional 931 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 932 February 2016, . 934 8.2. Informative References 936 [I-D.hegde-spring-node-protection-for-sr-te-paths] 937 Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, 938 "Node Protection for SR-TE Paths", draft-hegde-spring- 939 node-protection-for-sr-te-paths-05 (work in progress), 940 July 2019. 942 [I-D.ietf-rtgwg-segment-routing-ti-lfa] 943 Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B., 944 Francois, P., Voyer, D., Clad, F., and P. Camarillo, 945 "Topology Independent Fast Reroute using Segment Routing", 946 draft-ietf-rtgwg-segment-routing-ti-lfa-03 (work in 947 progress), March 2020. 949 [I-D.ietf-spring-segment-routing-policy] 950 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 951 P. Mattes, "Segment Routing Policy Architecture", draft- 952 ietf-spring-segment-routing-policy-07 (work in progress), 953 May 2020. 955 [I-D.sivabalan-pce-binding-label-sid] 956 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 957 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 958 in PCE-based Networks.", draft-sivabalan-pce-binding- 959 label-sid-07 (work in progress), July 2019. 961 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 962 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 963 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 964 2009, . 966 Authors' Addresses 968 Zhibo Hu 969 Huawei Technologies 970 Huawei Bld., No.156 Beiqing Rd. 971 Beijing 100095 972 China 974 Email: huzhibo@huawei.com 976 Huaimo Chen 977 Futurewei 978 Boston, MA 979 USA 981 Email: Huaimo.chen@futurewei.com 983 Junda Yao 984 Huawei Technologies 985 Huawei Bld., No.156 Beiqing Rd. 986 Beijing 100095 987 China 989 Email: yaojunda@huawei.com 990 Chris Bowers 991 Juniper Networks 992 1194 N. Mathilda Ave. 993 Sunnyvale, CA 94089 994 USA 996 Email: cbowers@juniper.net 998 Yongqing 999 China Telecom 1000 109, West Zhongshan Road, Tianhe District 1001 Guangzhou 510000 1002 China 1004 Email: zhuyq8@chinatelecom.cn