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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Santosh Esale 3 Intended Status: Proposed Standard Kireeti Kompella 4 Expires: November 21, 2018 Juniper Networks 5 May 20, 2018 7 LDP Extensions for RMR 8 draft-esale-mpls-ldp-rmr-extensions-02 10 Abstract 12 This document describes LDP extensions to signal Resilient MPLS Ring 13 (RMR) Label Switched Paths (LSPs). An RMR LSP is a multipoint to 14 point LSP signaled using LDP (Label Distribution Protocol). RMR 15 Architecture document - draft-ietf-mpls-rmr-02 - describes why and 16 how MPLS should be used in ring topologies. 18 Status of this Memo 20 This Internet-Draft is submitted to IETF in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that 25 other groups may also distribute working documents as 26 Internet-Drafts. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 The list of current Internet-Drafts can be accessed at 34 http://www.ietf.org/1id-abstracts.html 36 The list of Internet-Draft Shadow Directories can be accessed at 37 http://www.ietf.org/shadow.html 39 Copyright and License Notice 41 Copyright (c) 2018 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Protocol extensions . . . . . . . . . . . . . . . . . . . . . 4 59 3.1. Ring LSP Capability . . . . . . . . . . . . . . . . . . . 4 60 3.2. Ring FEC Element . . . . . . . . . . . . . . . . . . . . . 4 61 4. Ring Procedures . . . . . . . . . . . . . . . . . . . . . . . 6 62 4.1 Upstream LSR . . . . . . . . . . . . . . . . . . . . . . . . 6 63 4.2 Ring Label Mapping Procedures . . . . . . . . . . . . . . . 7 64 4.2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . 7 65 4.2.2 Preliminary . . . . . . . . . . . . . . . . . . . . . . 7 66 4.2.3 Egress LSR . . . . . . . . . . . . . . . . . . . . . . 7 67 4.2.4 Ingress and Transit LSR . . . . . . . . . . . . . . . . 8 68 4.3 Equal Cost Multipath (ECMP) . . . . . . . . . . . . . . . . 8 69 4.4 Protection . . . . . . . . . . . . . . . . . . . . . . . . . 8 70 5. LSP Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 9 71 6. Ring LSPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 72 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 73 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 11 74 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 11 75 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11 76 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 77 11.1 Normative References . . . . . . . . . . . . . . . . . . . 12 78 11.2 Informative References . . . . . . . . . . . . . . . . . . 12 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 81 1 Introduction 83 This document describes LDP extensions to signal resilient MPLS ring 84 (RMR) label switched paths (LSPs). An RMR LSP is a multipoint to 85 point LSP signaled using LDP (Label Distribution Protocol). 86 Architecture document of RMR - draft-ietf-mpls-rmr-02 - describes why 87 and how MPLS should be used in ring topologies. 89 The ring is either auto-discovered or configured using IGP protocol 90 such as OSPF or ISIS. IGP extensions for RMR is described in a 91 companion documents. After the ring discovery, each ring node acting 92 as egress constructs and signals a clockwise (CW) and anti-clockwise 93 (AC) ring FEC towards AC and CW direction respectively. Each transit 94 node that receives the RMR FEC signals this LSP further in same 95 direction using RMR link state database. In addition, it also adds a 96 transit and ingress route for this LSP. Once the signaling is 97 complete, every node in a ring should have two counter rotating LSPs 98 in CW and AC direction to reach every other node on the ring. 100 2. Terminology 102 A ring consists of a subset of n nodes {R_i, 0 <= i < n}. The 103 direction from node R_i to R_i+1 is defined as as "clockwise" (CW) 104 and the reverse direction is defined as "anti-clockwise" (AC). As 105 there may be several rings in a graph, each ring is numbered with a 106 distinct ring ID (RID). 108 The following terminology is used for ring LSPs: 110 Ring ID (RID): A non-zero number that identifies a ring; this is 111 unique in some scope of a Service Provider's network. A node 112 may belong to multiple rings. 114 Ring node: A member of a ring. Note that a device may belong to 115 several rings. 117 Node index: A logical numbering of nodes in a ring, from zero upto 118 one less than the ring size. Used purely for exposition in this 119 document. 121 Ring neighbors: Nodes whose indices differ by one (modulo ring 122 size). 124 Ring links: Links that connect ring neighbors. 126 Express links: Links that connect non-neighboring ring nodes. 128 MP2P LSP: Each LSP in the ring is a multipoint to point LSP such 129 that LSP can have multiple ingress nodes and one egress node. 131 3. Protocol extensions 133 This section describes LDP extensions to signal RMR LSP in a ring. 135 3.1. Ring LSP Capability 137 RMR LSPs support for a LSR is advertised using LDP capabilities as 138 defined in [RFC5561]. An implementation that supports the RMR 139 procedures specified in this document MUST add the procedures 140 pertaining to Capability Parameters for Initialization messages. 142 A new optional capability parameter TLV, RMR Capability, is defined. 143 Following is the format of the RMR Capability Parameter: 145 0 1 2 3 146 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 1 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 |U|F| RMR Capability (TBD) | Length (= 1) | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 |S| Reserved | 151 +-+-+-+-+-+-+-+-+ 153 As described in [RFC5561] 154 U: set to 1. Ignore, if not known. 155 F: Set to 0. Do not forward. 156 S: MUST be set to 1 to advertise the RMR Capability TLV. 158 The RMR Capability TLV MUST be advertised in the LDP Initialization 159 message. If the peer has not advertised the RMR capability, then 160 label messages pertaining to RMR FEC Element MUST NOT be sent to the 161 peer. 163 3.2. Ring FEC Element 165 In order to setup RMR LSP in clockwise and anti-clockwise direction 166 for every ring node, this document defines new protocol entity, the 167 RMR FEC Element, to be used as a FEC Element in the FEC TLV. 169 The RMR FEC Element consists of the ring address, ring identifier and 170 ring flags which depicts ring direction. The combination of ring 171 address, ring identifier and ring flags uniquely identifies a ring 172 LSP within the MPLS network. 174 The RMR FEC Element value encoding is as follows: 176 0 1 2 3 177 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 1 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 | RMR(TBD) | Address Family | PreLen | 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | Ring Prefix | 182 ~ ~ 183 | | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Ring ID | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | Ring Flags | Reserved | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 FEC Type 191 One octet quantity containing a value from FEC Type 192 Name Space that encodes the fec type for a RMR LDP LSP. 194 Address Family 195 Two octet quantity containing a value from ADDRESS FAMILY 196 NUMBERS in [ASSIGNED_AF] that encodes the address family for 197 the address prefix in the Prefix field. 199 PreLen 200 One octet unsigned integer containing the length in bits of 201 the address prefix that follows. A length of zero indicates 202 a prefix that matches all addresses (the default 203 destination); in this case, the Prefix itself is zero 204 octets). 206 Prefix 207 An address prefix encoded according to the Address Family 208 field, whose length, in bits, was specified in the PreLen 209 field, padded to a byte boundary. 211 Ring ID (RID) 212 A four-octet non-zero number that identifies a ring; this is 213 unique in some scope of a Service Provider's network. 215 Ring Flags 217 0 218 0 1 2 3 4 5 6 7 219 +-+-+-+-+-+-+-+-+ 220 |RF | Reserved | 221 +-+-+-+-+-+-+-+-+ 222 The value of ring flags (RF) is defined as follows: 223 1: Clockwise (CW) FEC 224 2: Anti-clockwise (AC) FEC 226 4. Ring Procedures 228 This section describes LDP procedures to signal RMR LSP in a ring. 230 4.1 Upstream LSR 232 Upstream LSR for RMR LSP is selected as follows: 234 R0 . . . R1 235 . . 236 R7 . RID = 18 . R2 237 | . . . . | 238 Anti- | . R9 . . R8 . | 239 Clockwise v . . v Clockwise 240 R6 RID =17 R3 241 . . 242 R5 . . . R4 244 Figure 1: Two Rings with 10 nodes 246 Consider a MPLS ring with 10 nodes. During the discovery of this 247 ring, IGP populates its link state database with ring information. 248 After the discovery, there are just two paths - one in clockwise 249 direction and other in anti-clockwise direction - for every ring 250 neighbor on a specific ring. For instance, the following table shows 251 router R0's path for ring 17 and 18 depicted in figure 1. 253 +--------------------------------+ 254 | RID |CW neighbor|AC neighbor| 255 +--------------------------------+ 256 | 17 | R1 | R7 | 257 +--------------------------------+ 258 | 18 | R1 | R9 | 259 +--------------------------------+ 261 Figure 2: R0's RMR upstream signaling table 263 IGP informs LDP that a new MPLS ring, RID 17, is discovered. A LDP 264 transit LSR uses this information to establish RMR LSPs. For 265 instance, suppose R5 receives a FEC with prefix R0, RID 17 and ring 266 flags AC. R5 knows that its clockwise path is R6 and anti-clockwise 267 path is R4 to reach R0 and that the label map arrived from router R4 268 for a anti-clockwise LSP. Therefore, R5 selects the upstream session 269 for this LSP as R6. 271 4.2 Ring Label Mapping Procedures 273 The procedures in the subsequent sections are organized by the role 274 that a node plays to establish a ring LSP. Each node is egress for 275 its own prefixes and transit for every prefix received with a Label 276 Mapping message. Every transit node is also a ingress for that LSP. 278 4.2.1 Definitions 280 This section defines the notations for initiation, decoding, 281 processing and propagation of RMR FEC Element. 283 1. RMR FEC Element or : a FEC Element with egress 284 prefix P, RID R and clockwise direction C or 285 anti-clockwise direction A. 286 2. RMR Label Mapping or : a Label Mapping 287 message with a FEC TLV with a single RMR FEC Element or 288 and Label TLV with label L. Label L MUST be allocated 289 from the per-platform label space of the LSR sending the Label 290 Mapping message. The use of the interface label space is outside 291 the scope of this document. 292 3. RMR Label Withdraw or : a Label Withdraw 293 message with a FEC TLV with a single RMR FEC Element or 294 and Label TLV with label L. 295 4. RMR LSP or : A RMR LSP with egress prefix P, 296 Ring ID R and clockwise direction C or anti-clockwise direction A. 298 4.2.2 Preliminary 300 A node X wishing to participate in LDP RMR signaling SHOULD negotiate 301 the RMR capability with all its neighbors. When the IGP informs X of 302 its RMR neighbors A and C for RID R, it MUST check that A and C have 303 also negotiated the RMR capability with X. If these conditions are 304 not satisfied, X cannot participate in signaling for ring R. This 305 applies for all roles that X may play: ingress, transit and egress. 307 4.2.3 Egress LSR 309 Every ring node initiates two counter-rotating LSPs that egress on 310 that node. After the IGP discovers the ring, LDP constructs the 311 clockwise RMR FEC and sends it in a Label Mapping message 312 to anti-clockwise neighbor. Similarly, LDP constructs a anti- 313 clockwise RMR FEC and sends it in a Label Mapping message 314 to clockwise neighbor. This SHOULD establish a clockwise and anti- 315 clockwise LSP - in terms of data traffic - in the clockwise and anti- 316 clockwise direction respectively. 318 Furthermore, if a label other than implicit or explicit null is 319 advertised for a LSP, LDP SHOULD add a pop route for this label in 320 the Incoming Label Map (ILM) MPLS table. 322 When the node is no longer part of the ring, it SHOULD tear down its 323 egress LSPs - CW and AC - by sending a label withdraw message. 325 4.2.4 Ingress and Transit LSR 327 When a transit LSR R5 depicted in figure 1 receives a label map 328 message with RMR FEC Element from a downstream LDP 329 session to R4, it SHOULD verify that R4 is indeed its anticlockwise 330 neighbor for ring 17. If not, it SHOULD stop decoding the FEC TLV, 331 abort processing the message containing the TLV, send an "Unknown 332 FEC" Notification message to its LDP peer R4 signaling an error and 333 close the session. 335 If the LSR encounters no other error while parsing the RMR FEC 336 element, it allocates a Label L2 and determines a upstream LDP 337 session as R6 using the algorithm described in section 'Upstream 338 LSR'. It also programs a MPLS ILM table with label route L2 swapped 339 to L1 and Ingress tunnel table with prefix R0 with label push L1 on 340 all the LDP interfaces to R4, and sends the RMR FEC Element to R6. 343 If a session to the anti-clockwise neighbor for RID 17 depicted in 344 Figure 2, namely R6, does not exist, the RMR FEC Element SHOULD NOT be propagated further. Similarly, when the upstream 346 session changes because of ring topology change, transit LSR should 347 send a label withdraw for RMR FEC Element to older 348 upstream session R6 before sending Label Mapping message with RMR FEC 349 Element to a new upstream session. 351 4.3 Equal Cost Multipath (ECMP) 353 A transit and ingress LSR of RMR LSP uses all the links between 354 itself and downstream LSR to program transit and ingress route. Thus, 355 ECMP works automatically for a LDP RMR LSP. A vendor could provide 356 exception when necessary to this behavior by disabling certain ring 357 links for RMR LSPs. 359 4.4 Protection 360 RMR uses the two counter-rotating LSPs to protect the other. Say 361 that R5 wants to protect the LSP to R0 for RID 17. R5 receives RMR 362 FEC Element from R4 and sends RMR FEC Element to R6. Then the primary path for the AC LSP is to swap L1 364 with L2 with next hop R4. Also, R5 receives RMR FEC Element from R6 and sends RMR FEC Element to R4. The 366 primary path for the CW LSP is to swap L3 with L4. The protection 367 path for the AC LSP is to swap L1 with L4 with next hop R6, thus 368 sending the traffic back where it came from, but with a different 369 label. The protection path for the CW LSP is to swap L3 with L2 with 370 next hop R4. 372 5. LSP Hierarchy 374 R9 R10 R11 375 . . . 376 . . . . 377 . . 378 R8 . . . R9 379 . . 380 . . 381 . . 382 R0 . . . R1 383 . . 384 R7 R2 385 Anti- | . Ring . | 386 Clockwise | . . | Clockwise 387 v . RID = 17 . v 388 R6 R3 389 . . 390 R5 . . . R4 392 Figure 3: Ring 17 with rest of the Network 394 Suppose R5 needs to reach R10. Only RMR LSPs are setup inside the 395 ring 17. Additionally, whenever services on R5 need to reach R10, R5 396 dynamically establishes a tLDP session to ring 17 master node R0 and 397 R1. Further, suppose it only learns IPv4 and IPv6 FECs only over this 398 session using [draft-ietf-mpls-app-aware-tldp-05]. Thus, in order to 399 reach R10, R5 uses top label as RMR LSP label to R0 or R1 and bottom 400 label as R10's FEC label received over tLDP session of R0 or R1 401 respectively. 403 6. Ring LSPs 404 An RMR LSP consists of two counter-rotating ring LSPs that start and 405 end at the same node, say R1. As such, this appears to cause a loop, 406 something that is normally to be avoided by LDP [RSVP-TE]. There are 407 some benefits to this. Having a ring LSP allows the anchor node R1 408 to ping itself and thus verify the end-to-end operation of the LSP. 409 This, in conjunction with link-level OAM, offers a good indication of 410 the operational state of the LSP. [Also, having R1 be the ingress 411 means that R1 can initiate the Path messages for the two ring LSPs. 412 This avoids R1 having to coordinate with its neighbors to signal the 413 LSPs, and simplifies the case where a ring update changes R1's ring 414 neighbors.] The cost of this is a little more signaling and a couple 415 more label entries in the LFIB. 417 7. Security Considerations 419 The Capability and RMR FEC procedures described in this document will 420 not introduce any change to LDP Security Considerations section 421 described in [RFC5036]. 423 8. IANA Considerations 425 This document requires the assignment of a new code point for a 426 Capability Parameter TLVs from the IANA managed LDP registry "TLV 427 Type Name Space", corresponding to the advertisement of the RMR 428 capability. IANA is requested to assign the lowest available value. 430 Value Description Reference 431 ----- ---------------- --------- 432 TBD1 RMR capability [this document] 434 This document requires the assignment of a new code point for a FEC 435 type from the IANA managed LDP registry "Forwarding Equivalence Class 436 (FEC) Type Name Space". IANA is requested to assign the lowest 437 available value. 439 Value Description Reference 440 ----- ---------------- --------- 441 TBD1 RMR FEC type [this document] 443 9. Acknowledgments 445 TODO. 447 10. Contributors 449 Raveendra Torvi 450 Juniper Networks 451 10 Technology Park Dr 452 Westford, MA 01886 453 USA 454 Email: rtorvi@juniper.net 456 Ravi Singh 457 Juniper Networks 458 1133 Innovation Way 459 Sunnyvale, CA 94089 460 USA 461 Email: ravis@juniper.net 463 Abhishek Deshmukh 464 Juniper Networks 465 10 Technology Park Dr 466 Westford, MA 01886 467 USA 468 Email: adeshmukh@juniper.net 470 11. References 472 11.1 Normative References 474 [I-D.ietf-mpls-rmr] Kompella, K. and L. Contreras, "Resilient MPLS 475 Rings", draft-ietf-mpls-rmr-03 (work in progress), October 476 2016. 478 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 479 "LDP Specification", RFC 5036, October 2007, 480 . 482 [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. 483 Le Roux, "LDP Capabilities", RFC 5561, July 2009, 484 . 486 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 487 Requirement Levels", BCP 14, RFC 2119, DOI 488 10.17487/RFC2119, March 1997, . 491 11.2 Informative References 493 [RFC6388] IJ. Wijnands, I. Minei, K. Kompella, B. Thomas, "Label 494 Distribution Protocol Extensions for Point-to-Multipoint 495 and Multipoint-to-Multipoint Label Switched Paths", RFC 496 6388, November 2011, 499 [I-D.draft-deshmukh-mpls-rsvp-rmr-extension] A. Deshmukh, K. 500 Kompella, "RSVP Extensions for RMR", draft-deshmukh-mpls- 501 rsvp-rmr-extension-00 (work in progress), July 2016. 503 [I-D.draft-kompella-isis-ospf-rmr] K. Kompella, "IGP Extensions for 504 Resilient MPLS Rings", draft-kompella-isis-ospf-rmr-00 505 (work in progress), October 2016. 507 [I-D.draft-ietf-mpls-app-aware-tldp] Santosh Esale, Raveendra Torvi, 508 Luay Jalil, U. Chunduri, Kamran Raza, "Application-aware 509 Targeted LDP", draft-ietf-mpls-app-aware-tldp-05 (work in 510 progress), June 2016. 512 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 513 Requirement Levels", BCP 14, RFC 2119, March 1997, 514 . 516 Authors' Addresses 518 Santosh Esale 519 Juniper Networks 520 1133 Innovation Way 521 Sunnyvale, CA 94089 522 USA 523 Email: sesale@juniper.net 525 Kireeti Kompella 526 Juniper Networks 527 1133 Innovation Way 528 Sunnyvale, CA 94089 529 USA 530 Email: kireeti@juniper.net