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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: draft-ietf-mpls-targeted-mldp has been published as RFC 7060 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group IJ. Wijnands, Ed. 3 Internet-Draft E. Rosen 4 Intended status: Standards Track K. Raza 5 Expires: May 17, 2015 Cisco Systems, Inc. 6 J. Tantsura 7 Ericsson 8 A. Atlas 9 Juniper Networks 10 Q. Zhao 11 Huawei Technology 12 November 13, 2014 14 mLDP Node Protection 15 draft-ietf-mpls-mldp-node-protection-02 17 Abstract 19 This document describes procedures to support node protection for 20 Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths 21 (MP LSPs) built by LDP ("Label Distribution Protocol"), or simply 22 mLDP. In order to protect a node N, the Point of Local Repair (PLR) 23 LSR of N must learn the Merge Point (MPT) LSR(s) of node N such that 24 traffic can be redirected to them in case node N fails. Redirecting 25 the traffic around the failed node N depends on existing P2P LSPs 26 originated from the PLR LSR to the MPT LSRs while bypassing LSR node 27 N. 29 Status of this Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on May 17, 2015. 46 Copyright Notice 48 Copyright (c) 2014 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 1.1. Conventions used in this document . . . . . . . . . . . . 3 65 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 66 2. PLR Determination . . . . . . . . . . . . . . . . . . . . . . 4 67 2.1. Transit node procedure . . . . . . . . . . . . . . . . . . 4 68 2.2. MP2MP root node procedure . . . . . . . . . . . . . . . . 5 69 2.3. PLR information encoding . . . . . . . . . . . . . . . . . 5 70 3. Using the tLDP session . . . . . . . . . . . . . . . . . . . . 7 71 4. Link or node failure . . . . . . . . . . . . . . . . . . . . . 9 72 4.1. Re-convergence after node/link failure . . . . . . . . . . 10 73 4.1.1. Node failure . . . . . . . . . . . . . . . . . . . . . 10 74 4.1.2. Link failure . . . . . . . . . . . . . . . . . . . . . 10 75 4.1.3. Switching to new primary path . . . . . . . . . . . . 11 76 5. mLDP Capabilities for Node Protection . . . . . . . . . . . . 11 77 5.1. PLR capability . . . . . . . . . . . . . . . . . . . . . . 12 78 5.2. MPT capability . . . . . . . . . . . . . . . . . . . . . . 12 79 5.3. The Protected LSR . . . . . . . . . . . . . . . . . . . . 12 80 5.4. The Node Protection Capability . . . . . . . . . . . . . . 13 81 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 82 7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 14 83 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 84 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 85 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 86 9.2. Informative References . . . . . . . . . . . . . . . . . . 15 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 89 1. Introduction 91 This document describes procedures to support node protection for 92 Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths 93 (MP-LSPs) built by LDP ("Label Distribution Protocol"), or simply 94 mLDP. In order to protect a node N, the Point of Local Repair (PLR) 95 of N must learn the Merge Point (MPT) LSR(s) of node N such that 96 traffic can be redirected to them in case node N fails. Redirecting 97 the traffic around the failed node N depends on existing P2P LSPs 98 originating from the PLR LSR to the MPT LSR(s) while bypassing node 99 N. The procedures to setup these P2P LSPs are outside the scope of 100 this document, but one can imagine using RSVP-TE or LDP LFA based 101 techniques to accomplish this. 103 The solution described in this document signals the MPT LSR(s) to the 104 PLR LSR(s) via a Targeted LDP (tLDP) session [RFC5036]. By having a 105 tLDP session with the PLR, most of the (m)LDP features currently 106 defined should just work, like Make-Before-Break (MBB), Graceful 107 Restart (GR), Typed Wildcard FEC support, etc. All this is achieved 108 at the expense of having an additional tLDP session between an MPT 109 and PLR LSR. 111 1.1. Conventions used in this document 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 115 document are to be interpreted as described in RFC 2119 [RFC2119]. 117 The terms "node" is used to refer to an LSR and used interchangeably. 118 The terms "PLR" and "MPT" are used as shorthand to refer to "PLR LSR" 119 and "MPT LSR" respectively. 121 1.2. Terminology 123 mLDP: Multipoint extensions to LDP. 125 PLR: Point of Local Repair (the LSR that redirects the traffic to 126 one or more Merge Point LSRs). 128 MPT: Merge Point (the LSR that merges the backup LSP with primary 129 LSP. Note, there can be multiple MPT LSRs for a single MP-LSP 130 node protection). 132 tLDP: Targeted LDP session. 134 MP LSP: Multi-Point LSP (either a P2MP or MP2MP LSP). 136 2. PLR Determination 138 In order for a MPT to establish a tLDP session with the PLR, it first 139 has to learn the PLR for a particular MP LSP. It is the 140 responsibility of the protected node N to advertise the PLR address 141 to the MPT. The PLR address for a MP LSP on node N is the address of 142 the upstream LDP peer, but only when node N is NOT the root node of 143 the MP2MP LSP. If node N is the root node, the procedures are 144 slightly different as described in Section 2.2. The procedures that 145 follow assume that all the participating nodes (N, PLRs, MPTs) are 146 enabled (e.g. by a user configuration) to support and implement this 147 feature. 149 2.1. Transit node procedure 151 Below we are describing the procedures when the protected node is a 152 transit node along the path to the root. 154 root 155 ^ 156 | 157 (LSR1) 158 . | . 159 . | . 160 . (N) . 161 . / \ . 162 . / \. 163 (LSR2) (LSR3) 164 | | 165 Figure 1. 167 N: The node being protected, 168 ...: Backup LSPs from LSR1 to the LSR2 and LSR3. 170 Node N uses the root address of the MP LSP to determine the upstream 171 LSR for a given MP LSP following the procedures as documented in 172 [RFC6388] section 2.4.1.1. The upstream LSR in figure 1 is LSR1 173 because it is the first hop along the shortest path to reach the root 174 address. After determining the upstream LSR, node N (which is 175 feature enabled), MUST advertise the address of LSR1 as the PLR 176 address to the downstream members of the MP LSP (i.e. LSR2 and LSR3) 177 if the given downstream member has announced support for node 178 protection (see Section 5) for Capability negotiation). For the 179 format and encoding of PLR address information, see Section 2.3. 181 2.2. MP2MP root node procedure 183 In this section we are describing the procedures for when the 184 protected node is the root of a MP2MP LSP. Consider figure 2 below; 186 | 187 (LSR1) 188 . | . 189 . | . 190 . (N) . root 191 . / \ . 192 . / \. 193 (LSR2)....(LSR3) 194 | | 195 Figure 2. 197 N: The MP2MP root node being protected. 198 ...: Backup LSPs between LSR1, LSR2 and LSR3. 200 Assume that LSR1, LSR2 and LSR3 are all members of a MP2MP LSP for 201 which N is the root node. Since N is the root of the MP2MP LSP, 202 there is no upstream LSR and no 'single' PLR LSR for protecting node 203 N. In order to protect node N, all the directly connected members of 204 the MP2MP must participate in protecting node N by acting both as PLR 205 and MPT LSR. An LSR will act as MPT for traffic coming from the 206 other LSR(s) and it will act as PLR for traffic it is sending to the 207 other LSR(s). Since node N knows the members of the MP2MP LSP, it 208 will advertise the member list to its directly connected members, 209 excluding the member it is sending to. For example, node N will 210 advertise {LSR3,LSR1} list to LSR2 excluding LSR2 from it. Instead 211 of advertising a single PLR when node N is not the root, a list of 212 PLRs is advertised using the procedures documented in Section 2.3. 214 It should be noted that the MP2MP root node protection mechanism 215 don't replace the Root Node Redundancy (RNR) procedures as described 216 in [RFC6388] section 7. The node protection procedures in this draft 217 will help restoring traffic for the existing MP2MP LSPs after node 218 failure, but a new root node has to be elected eventually in order to 219 allow new MP2MP LSPs to be created. 221 2.3. PLR information encoding 223 The upstream LSR address is conveyed via an LDP Notification message 224 with MP Status, where the MP status contains a new "PLR Status Value 225 Element" that specifies the address of the PLR. 227 The new "PLR Status Value Element" is encoded as follows; 228 PLR Status Element: 230 0 1 2 3 231 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 1 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | Type = TBA-1 | Length | Addr Family | 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 | Addr Fam cont | Num PLR entry | | 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 237 | | 238 | PLR entry (0 or more) ~ 239 | | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 Where 244 Type: PLR Status Value Element (Type TBA-1 to be assigned by IANA) 246 Length: The Length field encodes the length of the Status Value 247 following the Length field. The encoded Length varies based on 248 the Address Family and the number of PLR entries. 250 Address Family: Two octet quantity containing a value from IANA's 251 "Address Family Numbers" registry that encodes the address family 252 for the PLR Address encoded in the PLR entry. 254 Num PLR entry: Number of "PLR entries" encoded in the Status Value 255 Element, followed by "Num PLR entry" field (please see format of a 256 PLR entry below). 258 The format of a "PLR Entry" is as follows: 260 0 1 2 3 261 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 1 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 |A| Reserved | PLR address | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 ~ PLR address (cont) ~ 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 Where 270 A bit: 0 = Withdraw, 1 = Add. 272 Reserved: 15 bits, must be zero on transmit and ignored on receipt 273 PLR address: PLR Address encoded according to Address Family field 274 encoded in the PLR Status Value Element. 276 The size of a "PLR Entry" is the 2 octets ("A bit + Reserved") + PLR 277 address length. The length of the PLR address is depending on the 278 Address Family as encoded in the PLR Status Value Element. The size 279 of a "PLR entry" is 6 octets and 18 octets respectively for an IPv4 280 PLR address and an IPv6 PLR address. 282 If the PLR address on N changes for a given MP LSP, N needs to 283 trigger a new PLR Status to update the MPT(s). A node N can 284 advertise or withdraw a given PLR from its PLR set by setting "A bit" 285 to 1 or 0 respectively in corresponding PLR entry. Removing a PLR 286 address is likely due to a link failure, see the procedures as 287 documented in Section 4.1. To remove all PLR addresses belonging to 288 the encoded Address Family, an LSR N MUST encode PLR Status Value 289 Element with no PLR entry and "Num PLR entry" field MUST be set to 290 zero. 292 Along with the PLR MP Status a MP FEC TLV MUST be included in the LDP 293 Notification message so that a receiver is able to associate the PLR 294 Status with the MP LSP. 296 3. Using the tLDP session 298 The receipt of a PLR MP Status (with PLR addresses) for a MP LSP on a 299 receiving LSR makes it an MPT for node protection. If not already 300 established, the MPT LSR MUST establish a tLDP session with all of 301 the learned PLR addresses using the procedures as documented in 302 [I-D.ietf-mpls-targeted-mldp]. 304 Using Figure 1 as the reference topology, let us assume that both 305 LSR2 and LSR3 are MPTs and have established a tLDP session with the 306 PLR being LSR1. Assume that both LSR2 and LSR3 have a FEC with 307 a upstream LSR N and label Ln assigned to FEC towards N. The MPTs 308 will create a secondary upstream LSR (using the received PLR address) 309 and assigned a Label Lpx to FEC towards PLR for it. The MPTs 310 will do that for each PLR address that was learned for the MP LSP. 311 In this example, the MPTs will have a FEC with two local labels 312 associated with it. Ln that was assigned to N via the normal mLDP 313 procedures, and Label Lpx that was assigned for PLR (LSR1) for the 314 purpose of node protecting MP LSP via node N. Note, when the 315 protected node is a MP2MP root node, there will be an upstream LSR 316 for each PLR address that was advertised along with a unique Label 317 Lpx. 319 The receipt of a FEC Label Mapping alone over the tLDP session from 320 MPT on a PLR conveys the label information but does not convey the 321 node being protected. The information about a protected node is 322 known to the MPT LSR and needs to be communicated to the PLR as well. 323 For this reason, the FEC Label Mapping (FEC : Lpx) sent by the 324 MPT over the tLDP session to the PLR MUST include a Status TLV with 325 MP Status including a new LDP MP status Value Element called the 326 "Protected Node Status Value Element". This new value element is 327 used to specify the address of the node being protected. The 328 "Protected Node Status Value Element" has the following format; 330 0 1 2 3 331 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 1 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Type = TBA-2 | Length | Addr Family | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | Addr Fam cont | Node address | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | Node address continued | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 Type : Protected Node Status Value Element (Type TBA-2 to be 341 assigned by IANA) 343 Length: The Length field encodes the length of the Status Value 344 following the Length field. The encoded Length varies based on 345 the Address Family and is 6 octets (for Address Family + IPv4 346 address and 18 octets for Address Family + IPv6 address. 348 Address Family: Two octet quantity containing a value from IANA's 349 "Address Family Numbers" registry that encodes the address family 350 for the Node Address. 352 Node address: Protected node address encoded according to Address 353 Family field. 355 When a PLR receives a Label Mapping for FEC that includes a 356 Protected Node Status, it will only use that label binding once the 357 Node advertised in the Status value becomes unreachable. If the LSP 358 is a MP2MP LSP, the PLR would have assigned a Label Mapping for the 359 upstream MP2MP FEC Element to the MPT ([RFC6388] section 3) for FEC 360 . This label binding on the MPT MUST only be used once node N 361 becomes unreachable. 363 The procedures to determine if a node is unreachable is a local 364 decision and not spelled out in this draft. Typical link failure or 365 Bidirectional Forwarding Detection (BFD) can be used to determine and 366 detect node unreachability. 368 4. Link or node failure 370 Consider the following topology; 372 root 373 ^ 374 | 375 . (LSR1) 376 . / | . 377 . (M) | . 378 . \ | . 379 . (N) . 380 . / \ . 381 . / \. 382 (LSR2) (LSR3) 383 | | 384 Figure 3. 386 N: The node being protected 387 M: The backup node to protect link LSR1 - N 388 ...; Backup LSPs from LSR1 to LSR2 and LSR3. 390 Assume that LSR1 is the PLR for protected node N, LSR2 and LSR3 are 391 MPTs for node N. When LSR1 discovered that node N is unreachable, it 392 can't determine whether it is the 'LSR1 - N' link or node N that 393 failed. In Figure 3, the link between LSR1 and N is also protected 394 using Fast ReRoute (FRR) [RFC4090] link protection via node M. LSR1 395 MAY potentially invoke 2 protection mechanisms at the same time, 396 redirection the traffic due to link protection via node M to N, and 397 for node protection directly to LSR1 and LSR2. If only the link 398 failed, LSR2 and LSR3 will receive the packets twice due to the two 399 protection mechanisms. To prevent duplicate packets to be forwarded 400 to the receivers on the tree, LSR2 and LSR3 need to determin which 401 upstream node to accept the packets from. So, either from the 402 primary upstream LSR N or from the secondary upstream LSR1, but never 403 both at the same time. The selection between the primary upstream 404 LSR or (one or more) secondary upstream LSRs (on LSR2 and LSR3) is 405 based on the reachability of the protected node N. As long as N is 406 reachable, N is the primary upstream LSR who is accepting the MPLS 407 packets and forwarding them. Once N becomes unreachable, the 408 secondary upstream LSRs (LSR1 in our example) are activated. Note 409 that detecting if N is unreachable is a local decision and not 410 spelled out in this draft. Typical link failure or Bidirectional 411 Forwarding Detection (BFD) can be used to determine and detect node 412 unreachability. 414 4.1. Re-convergence after node/link failure 416 Consider the following topology; 418 root 419 ^ 420 _ | 421 /. (LSR1) 422 /. /. | .\ 423 /. (M). | .\ 424 (P). \. | .\ 425 \. ( N ) .(Q) 426 \. / \ ./ 427 \. / \ ./ 428 (LSR2) (LSR3) 429 | | 430 Figure 4. 432 N: The node being protected. 433 M: The backup node to protect link 'LSR1 - N'. 434 P and Q: The nodes on the new primary path after N failure. 435 ...: P2P backup LSPs. 437 Assume that LSR1 has detected that Node N is unreachable and invoked 438 both the Link Protection and Node Protection procedures as described 439 in this draft. LSR1 is acting as PLR and sending traffic over both 440 the backup P2P LSP to node N (via M) and the P2P LSPs directly to 441 LSR2 and LSR3, acting as MPT LSRs. The sequence of events are 442 depending on whether the link 'LSR1 - N' has failed or node N itself. 443 The node's downsteam from the protected node (and participating in 444 node protection) MUST have the capability to determin that the 445 protected node became unreachable. Otherwise the procedures below 446 can not be applied. 448 4.1.1. Node failure 450 If node N failed, both LSR2 and LSR3 will have changed the primary 451 upstream LSR to the secondary upstream LSR (LSR1) due to node N being 452 unreachable. With that, the label bindings previously assigned to 453 LSR1 will be activated on the MPTs (LSR2 and LSR3) and the label 454 binding to N will be disabled. Traffic is now switched over the 455 label bindings that where installed for node protection. 457 4.1.2. Link failure 459 If the link 'LSR1 - N' has failed, both LSR2 and LSR3 will not change 460 the primary upstream LSR because node N is still reachable. LSR2 and 461 LSR3 will receive traffic over two different bindings, the primary 462 label binding assigned to node N (due to link protection via node M) 463 as well as over the binding assigned to LSR1 for the node protection. 464 Since the secondary upstream LSRs have not been activated, the 465 traffic received due to node protection will be dropped. Node N will 466 re-converge and update LSR2 and LSR3 (Section 2.3) with the 467 information that the PLR address (LSR1) is no longer applicable and 468 must be removed. In response, LSR2 and LSR3 MUST sent a Label 469 Withdraw to LSR1 to withdraw the label binding. This will stop the 470 traffic being forwarded over the backup P2P LSPs for node protection. 471 LSR1 will respond back with a Label Release as soon as the binding 472 has been removed. 474 4.1.3. Switching to new primary path 476 The network will eventually re-converge and a new best path to the 477 root will be found by LSR2 and LSR3. LSR2 will find that P is its 478 new primary upstream LSR to reach the Root and LSR3 will find Q. Note 479 that although the current active upstream LSR can either be node N or 480 LSR1 (depending on link or node failure), it does not matter for the 481 following procedures. Both LSR2 and LSR3 SHOULD use the Make-Before- 482 Break (MBB) procedures as described in [RFC6388] section 8 to switch 483 to the new primary upstream node. As soon as the new primary 484 upstream LSRs P and Q are activated, a Label Withdraw message MUST be 485 sent to the old upstream LSR. Note that an upstream LSR switchover 486 from a tLDP neighbor to a directly connected LDP neighbor is no 487 different compared to switching between two directly connected 488 neighbors. After the Label Withdraw message has been received by 489 LSR1 or node N, forwarding will stop and a Label Release will be 490 sent. 492 When it is determined that after re-convergence there is no more 493 interest in the tLDP session between the MPT and the PLR, the tLDP 494 session MAY be taken down. It is possible that having no more 495 interest in the tLDP session is temporarily due to link flapping. In 496 order to avoid the tLDP session from flapping, it is RECOMMENDED to 497 apply a delay before tearing down the session. Determining the delay 498 is a local implementation matter. 500 5. mLDP Capabilities for Node Protection 502 In order to describe the capabilities of the participating LSRs , we 503 are organizing it per role in the network i.e., Point of Local Repair 504 (PLR), Merge Point (MPT), and Protected Node (as depicted in Fig 1). 506 5.1. PLR capability 508 A PLR node should handle the following conditions; 510 1. Accept an incoming tLDP session from the MPT LSR. 512 2. Support the receipt of a "Protected Node Status Value Element" 513 status in a MP Status TLV over tLDP session. 515 3. Upon node failure detection, capable of switching traffic towards 516 one or more MPT(s) over P2P LSP (bypassing N) using the labels 517 previously advertised for MP LSPs over the tLDP session. 519 An LSR capable of performing these actions will advertise it self as 520 PLR capable in the Node Protection capability (see Section 5.4). 521 This is a unidirectional capability announced from PLR to the 522 protected LSR. 524 5.2. MPT capability 526 An MPT node should handle the following conditions; 528 1. Support the receipt of "PLR Status Value Element" in a MP Status 529 TLV from a protected node N. 531 2. Support to transmit "Protected Node Status Value Element" in a MP 532 Status TLV to a PLR. 534 A LSR capable of performing these actions will advertise itself as 535 the MPT capable in the Node Protection capability (see Section 5.4). 536 This is a unidirectional capability from MPT to the protected LSR. 538 5.3. The Protected LSR 540 A protected node should handle the following conditions; 542 1. Determine the PLR and MPT capability for directly connected 543 upstream and downstream LSRs for a given MP FEC. 545 2. Support transmitting of "PLR Status Value Element" in a MP Status 546 TLV to one or more downstream MPT LSRs. 548 The protected LSR does not advertise any capability for mLDP Node 549 Protection because it does not need to receive any of the defined MP 550 Status values as described above. However, the protected node does 551 play an important role in the signaling and setup of the node 552 protection. For a given FEC, the protected node can only send PLR 553 information to a downstream LSR if the PLR has signaled the PLR 554 capability and the downstream LSR has signaled the MPT capability. 555 When the downstream LSR (acting as MPT) receives the PLR status, it 556 can implicitly infer that the advertised LSR(s) are PLR capable. The 557 MPT LSR can now proceed with setting up a tLDP session with the 558 PLR(s) and MP LSP node protection signaling. 560 5.4. The Node Protection Capability 562 We define a single capability "MP Node Protection Capability" to 563 announce the PLR and MPT capability. 565 The format of the capability parameter TLV is as follows: 567 0 1 2 3 568 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 1 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 |U|F| Type = TBA-3 | Length = 2 | 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 |S| Reserved |P|M| Reserved | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 Where 577 U/F bits: MUST be set to 1 and 0 respectively (as per [RFC5561]) 579 Type: MP Node Protection Capability (Type = TBA-3 to be assigned 580 by IANA) 582 Length: MUST be set to 2. 584 S bit: Set to 1 to announce and 0 to withdraw the capability (as 585 per [RFC5561]) 587 P bit: PLR capable for MP LSP node protection 589 M bit: MPT capable for MP LSP node protection 591 Reserved: Must be zero on transmit and ignored on receipt 593 The above capability can be sent in an LDP Initialization message to 594 announce capability at the session establishment time, or it can be 595 sent in LDP Capability message to dynamically update (announce or 596 withdraw) its capability towards its peer using procedures specified 597 in [RFC5561]. 599 An LSR that supports the PLR functionality LSR MAY send this 600 capability to its downstream MP peers with "P" bit set; whereas, an 601 LSR that supports an the MPT functionality MAY send this capability 602 to its upstream peer with "M" bit set. Moreover, an LSR that 603 supports both the PLR and MPT functionality MAY sent this capability 604 to its peers with both "P" and "M" bit set. 606 6. Security Considerations 608 The same security considerations apply as those for the base mLDP 609 specification, as described in [RFC6388]. 611 7. IANA considerations 613 IANA is requested to allocate two new code points from the "LDP MP 614 Status Value Element type" registry within the Label Distribution 615 Protocol (LDP) Parameters; 617 Value | Name | Reference 618 ------+----------------------------------------+----------- 619 TBA-1 | PLR Status Value Element | this doc 620 ------+----------------------------------------+----------- 621 TBA-2 | Protected Node Status Value Element | this doc 623 IANA is requested to assign a new code points for a new Capability 624 Parameter TLV. The code point should be assigned from the IETF 625 Consensus range of the "TLV Type Name Space" registry within the LDP 626 Parameters. The lowest available new code point after 0x0970 should 627 be used. 629 Value | Description | Reference | Notes/Reg Date 630 ------+-------------------------------+-----------+--------------- 631 TBA-3 | MP Node Protection Capability | This doc | 633 8. Acknowledgments 635 The authors like to thank Nagendra Kumar, Duan Hong, Martin 636 Vigoureux, Kenji Fujihira and Loa Andersson for their comments on 637 this draft. 639 9. References 641 9.1. Normative References 643 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 644 Requirement Levels", BCP 14, RFC 2119, March 1997. 646 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP 647 Specification", RFC 5036, October 2007. 649 [RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas, 650 "Label Distribution Protocol Extensions for Point-to- 651 Multipoint and Multipoint-to-Multipoint Label Switched 652 Paths", RFC 6388, November 2011. 654 [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. 655 Le Roux, "LDP Capabilities", RFC 5561, July 2009. 657 [I-D.ietf-mpls-targeted-mldp] 658 Napierala, M. and E. Rosen, "Using LDP Multipoint 659 Extensions on Targeted LDP Sessions", 660 draft-ietf-mpls-targeted-mldp-01 (work in progress), 661 January 2013. 663 9.2. Informative References 665 [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute 666 Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 667 May 2005. 669 Authors' Addresses 671 IJsbrand Wijnands (editor) 672 Cisco Systems, Inc. 673 De kleetlaan 6a 674 Diegem 1831 675 Belgium 677 Email: ice@cisco.com 679 Eric Rosen 680 Cisco Systems, Inc. 681 1414 Massachusetts Avenue 682 Boxborough MA 01719 683 USA 685 Email: erosen@cisco.com 686 Kamran Raza 687 Cisco Systems, Inc. 688 2000 Innovation Drive 689 Ottawa Ontario K2K-3E8 690 Canada 692 Email: skraza@cisco.com 694 Jeff Tantsura 695 Ericsson 696 300 Holger Way 697 San Jose CA 95134 698 USA 700 Email: jeff.tantsura@ericsson.com 702 Alia Atlas 703 Juniper Networks 704 10 Technology Park Drive 705 Westford MA 01886 706 USA 708 Email: akatlas@juniper.net 710 Quintin Zhao 711 Huawei Technology 712 125 Nagog Technology Park 713 Acton MA 01719 714 USA 716 Email: quintin.zhao@huawei.com