idnits 2.17.1 draft-ietf-mpls-app-aware-tldp-07.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 7, 2017) is 2635 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group Santosh Esale 3 INTERNET-DRAFT Raveendra Torvi 4 Updates: 7473 (if approved) Juniper Networks 5 Intended Status: Proposed Standard Luay Jalil 6 Expires: August 11, 2017 Verizon 7 Uma Chunduri 8 Huawei 9 Kamran Raza 10 Cisco Systems, Inc. 11 February 7, 2017 13 Application-aware Targeted LDP 14 draft-ietf-mpls-app-aware-tldp-07 16 Abstract 18 Recent targeted LDP (tLDP) applications such as remote loop-free 19 alternate (LFA) and BGP auto discovered pseudowire may automatically 20 establish a tLDP session to any LSR in a network. The initiating LSR 21 has information about the targeted applications to administratively 22 control initiation of the session. However, the responding LSR has no 23 such information to control acceptance of this session. This document 24 defines a mechanism to advertise and negotiate Targeted Applications 25 Capability (TAC) during LDP session initialization. As the 26 responding LSR becomes aware of targeted applications, it may 27 establish a limited number of tLDP sessions for certain applications. 28 In addition, each targeted application is mapped to LDP Forwarding 29 Equivalence Class (FEC) Elements to advertise only necessary LDP FEC- 30 label bindings over the session. This document updates RFC 7473. 32 Status of this Memo 34 This Internet-Draft is submitted to IETF in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF), its areas, and its working groups. Note that 39 other groups may also distribute working documents as 40 Internet-Drafts. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 The list of current Internet-Drafts can be accessed at 48 http://www.ietf.org/1id-abstracts.html 50 The list of Internet-Draft Shadow Directories can be accessed at 51 http://www.ietf.org/shadow.html 53 Copyright and License Notice 55 Copyright (c) 2017 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 1.1 Conventions Used in This Document . . . . . . . . . . . . . 4 72 1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 73 2. Targeted Application Capability . . . . . . . . . . . . . . . . 5 74 2.1 Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 5 75 2.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 2.3 LDP message procedures . . . . . . . . . . . . . . . . . . . 8 77 2.3.1 Initialization message . . . . . . . . . . . . . . . . . 8 78 2.3.2 Capability message . . . . . . . . . . . . . . . . . . . 8 79 3. Targeted Application FEC Advertisement Procedures . . . . . . . 9 80 4. Interaction of Targeted Application Capabilities and State 81 Advertisement Control Capabilities . . . . . . . . . . . . . . 10 82 5. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 83 5.1 Remote LFA Automatic Targeted session . . . . . . . . . . . 12 84 5.2 FEC 129 Auto Discovery Targeted session . . . . . . . . . . 13 85 5.3 LDP over RSVP and Remote LFA targeted session . . . . . . . 13 86 5.4 mLDP node protection targeted session . . . . . . . . . . . 13 87 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 13 88 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14 89 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 15 90 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . . 15 91 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 92 10.1 Normative References . . . . . . . . . . . . . . . . . . . 16 93 10.2 Informative References . . . . . . . . . . . . . . . . . . 16 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 96 1 Introduction 98 LDP uses extended discovery mechanism to establish the tLDP adjacency 99 and subsequent session as described in [RFC5036]. An LSR initiates 100 extended discovery by sending tLDP Hello to specific address. The 101 remote LSR decides to either accept or ignore the tLDP Hello based on 102 local configuration only. For an application such as FEC 128 103 pseudowire, the remote LSR is configured with the source LSR address 104 so that it can use that information to accept or ignore given tLDP 105 Hello. 107 Applications such as Remote LFA and BGP auto discovered pseudowire 108 automatically initiate asymmetric extended discovery to any LSR in a 109 network based on local state only. With these applications, the 110 remote LSR is not explicitly configured with the source LSR address. 111 So the remote LSR either responds or ignores all tLDP Hellos. 113 In addition, since the session is initiated and established after 114 adjacency formation, the responding LSR has no targeted applications 115 information to choose the targeted application it is configured to 116 support. Also, the initiating LSR may employ a limit per application 117 on locally initiated automatic tLDP sessions, however the responding 118 LSR has no such information to employ a similar limit on the incoming 119 tLDP sessions. Further, the responding LSR does not know whether the 120 source LSR is establishing a tLDP session for configured, automatic 121 or both applications. 123 This document proposes and describes a solution to advertise Targeted 124 Application Capability (TAC), consisting of a targeted application 125 list, during initialization of a tLDP session. It also defines a 126 mechanism to enable an new application and disable an old application 127 after session establishment. This capability advertisement provides 128 the responding LSR with the necessary information to control the 129 acceptance of tLDP sessions per application. For instance, an LSR may 130 accept all BGP auto discovered tLDP sessions as defined in [RFC6074] 131 but may only accept limited number of Remote LFA tLDP sessions as 132 defined in [RFC7490] 134 Also, targeted LDP application is mapped to LDP FEC element type to 135 advertise specific application FECs only, avoiding the advertisement 136 of other unnecessary FECs over a tLDP session. 138 1.1 Conventions Used in This Document 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 142 document are to be interpreted as described in RFC 2119 [RFC2119]. 144 1.2 Terminology 146 This document uses terminology discussed in [RFC7473] along with 147 others defined in this document. 149 TAC : Targeted Application Capability 150 TAE : Targeted Application Element 151 TA-Id : Targeted Application Identifier 152 SAC : State (FEC-Label bindings) Advertisement Control Capability 154 2. Targeted Application Capability 156 2.1 Encoding 158 An LSR MAY advertise that it is capable to negotiate a targeted LDP 159 application list over a tLDP session by using the Capability 160 Advertisement as defined in [RFC5561] and encoded as follows: 162 0 1 2 3 163 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 1 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 |U|F| TLV Code Point | Length | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 |S| Reserved | | 168 +-+-+-+-+-+-+-+-+ Capability Data | 169 | +-+-+-+-+-+-+-+-+ 170 | | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 This document defines a new optional capability TLV of type TBD1 174 called 'Targeted Application Capability (TAC)'. Flag "U" MUST be 175 set to 1 to indicate that this capability must be silently ignored 176 if unknown. 178 It's encoded as follows: 180 Targeted Application Element(TAE) 182 0 1 2 3 183 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 1 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Targ. Appl. Id |E| Reserved | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 Targeted Application Identifier (TA-Id): 189 a 16 bit Targeted Application Identifier value. 191 E-bit: The enable bit indicates whether the sender is 192 advertising or withdrawing the TAE. The E-bit value is used as 193 follows: 195 1 - The TAE is advertising the targeted application. 196 0 - The TAE is withdrawing the targeted application. 198 2.2 Procedures 200 At tLDP session establishment time, a LSR MAY include a new 201 capability TLV, TAC TLV, as an optional TLV in the LDP Initialization 202 message. The TAC TLV's Capability data MAY consists of none, one or 203 more TAE each pertaining to a unique TA-Id that a LSR supports over 204 the session. If the receiver LSR receives the same TA-Id in more than 205 one TAE, it MUST process the first element and ignore the duplicate 206 elements. If the receiver LSR received an unknown TA-Id in the TAE, 207 it MUST silently ignore such a TAE and continue processing the rest 208 of the TLV. 210 If the receiver LSR does not receive the TAC TLV in the 211 Initialization message or it does not understand the TAC TLV, the TAC 212 negotiation MUST be considered unsuccessful and the session 213 establishment MUST proceed as per [RFC5036]. On the receipt of a 214 valid TAC TLV, an LSR MUST generate its own TAC TLV with TAEs 215 consisting of unique TA-Ids that it supports over the tLDP session. 216 If there is at least one TAE common between the TAC TLV it has 217 received and its own, the session MUST proceed to establishment as 218 per [RFC5036]. If not, A LSR MUST send a 'Session Rejected/Targeted 219 Application Capability Mis-Match' Notification message to the peer 220 and close the session. The initiating LSR SHOULD tear down the 221 corresponding tLDP adjacency after sent or receipt of a 'Session 222 Rejected/Targeted Application Capability Mis-Match' Notification 223 message to or from the responding LSR respectively. 225 If both the peers advertise TAC TLV, an LSR decides to establish or 226 close a tLDP session based on the negotiated targeted application 227 list. For instance, suppose a initiating LSR advertises A, B and C as 228 TA-Ids. Further, suppose the responding LSR advertises C, D and E as 229 TA-Ids. Than the negotiated TA-Id, as per both the LSRs is C. In the 230 second instance, suppose a initiating LSR advertises A, B and C as 231 TA-Ids and the responding LSR, which acts as a passive LSR, 232 advertises all the applications - A, B, C, D and E that it supports 233 over this session. Than the negotiated targeted applications as per 234 both the LSRs are A, B and C. In the last instance, suppose the 235 initiating LSR advertises A, B and C as a TA-Ids and the responding 236 LSR advertises D and E as TA-Ids, than the negotiated targeted 237 applciations as per both the LSRs are none. Therefore, if the 238 intersection of the sets of received and sent TA-Id is null, then LSR 239 MUST sends 'Session Rejected/Targeted Application Capability Mis- 240 Match' Notification message to the initiating LSR and close the 241 session. 243 When the responding LSR playing the active role in LDP session 244 establishment receives a 'Session Rejected/Targeted Application 245 Capability Mis-Match' Notification message, it MUST set its session 246 setup retry interval to a maximum value, as 0xffff. The session MAY 247 stay in NON EXISTENT state. When it detects a change in the 248 initiating LSR or local LSR configuration pertaining to TAC TLV, it 249 MUST clear the session setup back off delay associated with the 250 session to re-attempt the session establishment. A LSR detects 251 configuration change on the other LSR with the receipt of tLDP Hello 252 message that has a higher configuration sequence number than the 253 earlier tLDP Hello message. 255 When the initiating LSR playing the active role in LDP session 256 establishment receives a 'Session Rejected/Targeted Application 257 Capability Mis-Match' Notification message, either it MUST close the 258 session and tear down the corresponding tLDP adjacency or it MUST set 259 its session setup retry interval to a maximum value, as 0xffff. 261 If it decides to tear down the associated tLDP adjacency, the session 262 is destroyed on the initiating as well as the responding LSR. The 263 initiating LSR MAY take appropriate actions if it is unable to bring 264 up the tLDP session. For instance, if an automatic session intended 265 to support the Remote LFA application is rejected by the responding 266 LSR, the initiating LSR may inform the IGP to calculate another PQ 267 node [RFC7490] for the route or set of routes. More specific actions 268 are a local matter and outside the scope of this document. 270 If it sets the session setup retry interval to maximum, the session 271 MAY stay in a non-existent state. When this LSR detects a change in 272 the responding LSR configuration or its own configuration pertaining 273 to TAC TLV, it MUST clear the session setup back off delay associated 274 with the session in order to re-attempt the session establishment. 276 After a tLDP session has been established with TAC capability, the 277 initiating and responding LSR MUST distribute FEC-label bindings for 278 the negotiated applications only. For instance, if the tLDP session 279 is established for BGP auto discovered pseudowire, only FEC 129 label 280 bindings MUST be distributed over the session. Similarly, a LSR 281 operating in downstream on demand mode MUST request FEC-label 282 bindings for the negotiated applications only. 284 If the Targeted Application Capability and Dynamic Capability, 285 described in [RFC5561], are negotiated during session initialization, 286 TAC MAY be re-negotiated after session establishment by sending an 287 updated TAC TLV in LDP Capability message. The updated TAC TLV 288 carries TA-Ids with incremental update only. The updated TLV MUST 289 consist of one or more TAEs with E-bit set or E-bit off to advertise 290 or withdraw the new and old application respectively. This may lead 291 to advertisements or withdrawals of certain types of FEC-Label 292 bindings over the session or tear down of the tLDP adjacency and 293 subsequently the session. 295 The Targeted Application Capability is advertised on tLDP session 296 only. If the tLDP session changes to link session, a LSR SHOULD 297 withdraw it with S bit set to 0. Similarly, if the link session 298 changes to tLDP, a LSR SHOULD advertise it via the Capability 299 message. If the capability negotiation fails, this may lead to 300 destruction of the tLDP session. 302 By default, LSR SHOULD accept tLDP hellos in order to then accept or 303 reject the tLDP session based on the application information. 305 In addition, LSR SHOULD allow the configuration of any TAI in order 306 to facilitate private TAI's usage by a network operator. 308 2.3 LDP message procedures 310 2.3.1 Initialization message 312 1. The S-bit of the Targeted Application Capability TLV MUST be 313 set to 1 to advertise Targeted Application Capability and 314 SHOULD be ignored on the receipt as defined in [RFC5561] 316 2. The E-bit of the Targeted Application Element MUST be set to 1 to 317 enable Targeted application and SHOULD be ignored on the receipt. 319 3. An LSR MAY add State Control Capability by mapping Targeted 320 Application Element to State Advertisement Control (SAC) Elements 321 as defined in Section 4. 323 2.3.2 Capability message 325 The initiating or responding LSR may re-negotiate the TAC after local 326 configuration change with the Capability message. 328 1. The S-bit of TAC is set to 1 or 0 to advertise or withdraw it. 330 2. After configuration change, If there is no common TAE between 331 its new TAE list and peers TAE list, the LSR MUST send a 332 'Session Rejected/Targeted Application Capability Mis-Match' 333 Notification message and close the session. 335 3. If there is a common TAE, a LSR MAY also update SAC Capability 336 based on updated TAC as described in section 4 and send the 337 updated TAC and SAC capabilities in a Capability message to 338 the peer. 340 4. A receiving LSR processes the Capability message with TAC TLV. 341 If the S-bit is set to 0, the TAC is disabled for the session. 343 5. If the S-bit is set to 1, a LSR process a list of TAEs from 344 TACs capability data with E-bit set to 1 or 0 to update the 345 peer's TAE. 347 3. Targeted Application FEC Advertisement Procedures 349 The targeted LDP application MUST be mapped to LDP FEC element types 350 as follows to advertise only necessary LDP FEC-Label bindings over 351 the tLDP session. 353 Targeted Application Description FEC mappings 354 +----------------------+------------------------+------------------+ 355 |LDPv4 Tunneling | LDP IPv4 over RSVP-TE | IPv4 prefix | 356 | | or other MPLS tunnel | | 357 +----------------------+------------------------+------------------+ 358 | | | | 359 |LDPv6 Tunneling | LDP IPv6 over RSVP-TE | IPv6 prefix | 360 | | or other MPLS tunnel | | 361 +----------------------+------------------------+------------------+ 362 |mLDP Tunneling | mLDP over RSVP-TE or | P2MP | 363 | | or other MPLS tunnel | MP2MP-up | 364 | | | MP2MP-down | 365 | | | HSMP-downstream | 366 | | | HSMP-upstream | 367 +----------------------+------------------------+------------------+ 368 | | | | 369 |LDPv4 Remote LFA | LDPv4 over LDPv4 or | IPv4 prefix | 370 | | other MPLS tunnel | | 371 +----------------------+------------------------+------------------+ 372 |LDPv6 Remote LFA | LDPv6 over LDPv6 or | IPv6 prefix | 373 | | other MPLS tunnel | | 374 +----------------------+------------------------+------------------+ 375 | | | | 376 |LDP FEC 128 PW | LDP FEC 128 Pseudowire | PWid FEC Element | 377 +----------------------+------------------------+------------------+ 378 | | | | 379 |LDP FEC 129 PW | LDP FEC 129 Pseudowire | Generalized PWid | 380 | | | FEC Element | 381 +----------------------+------------------------+------------------+ 382 | | | FEC types as | 383 |LDP Session Protection| LDP session protection | per protected | 384 | | | session | 385 +----------------------+------------------------+------------------+ 386 |LDP ICCP | LDP Inter-chasis | | 387 | | control protocol | None | 388 +----------------------+------------------------+------------------+ 389 | | | | 390 |LDP P2MP PW | LDP P2MP Pseudowire | P2MP PW Upstream | 391 | | | FEC Element | 392 +----------------------+------------------------+------------------+ 393 | | | P2MP | 394 |mLDP Node Protection | mLDP node protection | MP2MP-up | 395 | | | MP2MP-down | 396 | | | HSMP-downstream | 397 | | | HSMP-upstream | 398 +----------------------+------------------------+------------------+ 399 | | | | 400 |IPv4 intra-area FECs | IPv4 intra-area FECs | IPv4 prefix | 401 +----------------------+------------------------+------------------+ 402 | | | | 403 |IPv6 intra-area FECs | IPv6 intra-area FECs | IPv6 prefix | 404 +----------------------+------------------------+------------------+ 406 Intra-area FECs : FECs that are on the shortest path tree and not 407 leafs of the shortest path tree. 409 4. Interaction of Targeted Application Capabilities and State 410 Advertisement Control Capabilities 412 As described in this document, the set of TAEs negotiated between two 413 LDP peers advertising TAC represents the willingness of both peers to 414 advertise state information for a set of applications. The set of 415 applications negotiated by the TAC mechanism is symmetric between the 416 two LDP peers. In the absence of further mechanisms, two LDP peers 417 will both advertise state information for the same set of 418 applications. 420 As described in [RFC7473], State Advertisement Control(SAC) TLV can 421 be used by an LDP speaker to communicate its interest or disinterest 422 in receiving state information from a given peer for a particular 423 application. Two LDP peers can use the SAC mechanism to create 424 asymmetric advertisement of state information between the two peers. 426 The TAC negotiation facilitates the awareness of targeted 427 applications to both the peers. It enables them to advertise only 428 necessary LDP FEC-label bindings corresponding to negotiated 429 applications. With the SAC, the responding LSR is not aware of 430 targeted applications. Thus it may be unable to communicate its 431 interest or disinterest to receive state information from the peer. 432 Therefore, when the responding LSR is not aware of targeted 433 applications such a remote LFA and BGP auto discovered pseudowires, 434 TAC mechanism should be used and when the responding LSR is aware 435 (with appropriate configuration) of targeted applications such as FEC 436 128 pseudowire, SAC mechanism should be used. Also after TAC 437 mechanism makes the responding LSR aware of targeted application, the 438 SAC mechanism may be used to communicate its disinterest in receiving 439 state information from the peer for a particular negotiated 440 application, creating asymmetric advertisements. 442 Thus, the TAC mechanism enables two LDP peers to symmetrically 443 advertise state information for negotiated targeted applications. 444 Further, the SAC mechanism enables both of them to asymmetrically 445 disable receipt of state information for some of the already 446 negotiated targeted applications. Collectively, both TAC and SAC 447 mechanisms can be used to control the FEC-label bindings that are 448 advertised over the tLDP session. For instance, suppose the 449 initiating LSR establishes a tLDP session to the responding LSR for 450 Remote LFA and FEC 129 PW targeted applications with TAC. So each LSR 451 advertises the corresponding FEC-Label bindings. Further, suppose 452 the initiating LSR is not the PQ node for responding LSRs Remote LFA 453 IGP calculations. In such a case, the responding LSR may use the SAC 454 mechanism to convey its disinterest in receiving state information 455 for Remote LFA targeted LDP application. 457 For a given tLDP session, the TAC mechanism can be used without the 458 SAC mechanism, and the SAC mechanism can be used without the TAC 459 mechanism. It is useful to discuss the behavior when TAC and SAC 460 mechanisms are used on the same tLDP session. The TAC mechanism MUST 461 take precedence over the SAC mechanism with respect to enabling 462 applications for which state information will be advertised. For a 463 tLDP session using the TAC mechanism, the LDP peers MUST NOT 464 advertise state information for an application that has not been 465 negotiated in the most recent TAE list (referred to as an un- 466 negotiated application). This is true even if one of the peers 467 announces its interest in receiving state information that 468 corresponds to the un-negotiated application by sending a SAC TLV. 469 In other words, when TAC is being used, SAC cannot and should not 470 enable state information advertisement for applications that have not 471 been enabled by TAC. 473 On the other hand, the SAC mechanism MUST take precedence over the 474 TAC mechanism with respect to disabling state information 475 advertisements. If an LDP speaker has announced its disinterest in 476 receiving state information for a given application to a given peer 477 using the SAC mechanism, its peer MUST NOT send state information for 478 that application, even if the two peers have negotiated that the 479 corresponding application via the TAC mechanism. 481 For the purposes of determining the correspondence between targeted 482 applications defined in this document and application state as 483 defined in [RFC7473] an LSR MUST use the following mappings: 485 LDPv4 Tunneling - IPv4 Prefix-LSPs 486 LDPv6 Tunneling - IPv6 Prefix-LSPs 487 LDPv4 Remote LFA - IPv4 Prefix-LSPs 488 LDPv6 Remote LFA - IPv6 Prefix-LSPs 489 LDP FEC 128 PW - FEC128 P2P-PW 490 LDP FEC 129 PW - FEC129 P2P-PW 492 An LSR MUST map Targeted Application to LDP capability as follows: 494 mLDP Tunneling - P2MP Capability, MP2MP Capability 495 and HSMP LSP Capability TLV 496 mLDP node protection - P2MP Capability, MP2MP Capability 497 and HSMP LSP Capability TLV 499 5. Use cases 501 5.1 Remote LFA Automatic Targeted session 503 An LSR determines that it needs to form an automatic tLDP session to 504 remote LSR based on IGP calculation as described in [RFC7490] or some 505 other mechanism, which is outside the scope of this document. The LSR 506 forms the tLDP adjacency and during session setup, constructs an 507 Initialization message with TAC TLV with TAE as Remote LFA. The 508 receiver LSR processes the LDP Initialization message and verifies 509 whether it is configured to accept a Remote LFA tLDP session. If it 510 is, it may further verify that establishing such a session does not 511 exceed the configured limit for Remote LFA sessions. If all these 512 conditions are met, the receiver LSR may respond back with an 513 Initialization message with TAC corresponding to Remote LFA, and 514 subsequently the session may be established. 516 After the session has been established with TAC capability, the 517 sender and receiver LSR distribute IPv4 or IPv6 FEC label bindings 518 over the session. Further, the receiver LSR may determine that it 519 does not need these FEC label bindings. So it may disable the receipt 520 of these FEC label bindings by mapping targeted application element 521 to state control capability as described in section 4. 523 5.2 FEC 129 Auto Discovery Targeted session 525 BGP auto discovery MAY determine whether an LSR needs to initiate an 526 auto-discovery tLDP session with a border LSR. Multiple LSRs MAY try 527 to form an auto discovered tLDP session with a border LSR. So, a 528 service provider may want to limit the number of auto discovered tLDP 529 sessions a border LSR may accept. As described in Section 2, LDP may 530 convey targeted applications with TAC TLV to border LSR. A border LSR 531 may establish or reject the tLDP session based on local 532 administrative policy. Also, as the receiver LSR becomes aware of 533 targeted applications, it can also employ an administrative policy 534 for security. For instance, it can employ a policy 'accept all auto- 535 discovered session from source-list'. 537 Moreover, the sender and receiver LSR MUST exchange FEC 129 label 538 bindings only over the tLDP session. 540 5.3 LDP over RSVP and Remote LFA targeted session 542 A LSR may want to establish a tLDP session to a remote LSR for LDP 543 over RSVP tunneling and Remote LFA applications. The sender LSR may 544 add both these applications as a unique Targeted Application Element 545 in the Targeted Application Capability data of a TAC TLV. The 546 receiver LSR MAY have reached a configured limit for accepting Remote 547 LFA automatic tLDP sessions, but it may also be configured to accept 548 LDP over RSVP tunneling. In such a case, the tLDP session is formed 549 for both LDP over RSVP and Remote LFA applications as both needs same 550 FECs - IPv4 and/or IPv6. 552 5.4 mLDP node protection targeted session 554 A merge point LSR may determine that it needs to form automatic tLDP 555 session to the upstream point of local repair (PLR) LSR for MP2P and 556 MP2MP LSP [RFC6388] node protection as described in the [RFC7715]. 557 The MPT LSR may add a new targeted LDP application - mLDP protection, 558 as a unique TAE in the Targeted Application Capability Data of a TAC 559 TLV and send it in the Initialization message to the PLR. If the PLR 560 is configured for mLDP node protection and establishing this session 561 does not exceed the limit of either mLDP node protection sessions or 562 automatic tLDP sessions, the PLR may decide to accept this session. 563 Further, the PLR may respond back with the initialization message 564 with a TAC TLV that has one of the TAEs as - mLDP protection and the 565 session proceeds to establishment as per [RFC5036]. 567 6. Security Considerations 569 The Capability procedure described in this document will apply and 570 does not introduce any change to LDP Security Considerations section 571 described in [RFC5036]. 573 As described in [RFC5036], DoS attacks via Extended Hellos can be 574 addressed by filtering Extended Hellos using access lists that define 575 addresses with which Extended Discovery is permitted. Further, as 576 described in section 5.2 of this document, a LSR can employ a policy 577 to accept all auto-discovered Extended Hellos from the configured 578 source addresses list. 580 Also for the two LSRs supporting TAC, the tLDP session is only 581 established after successful negotiation of the TAC. The initiating 582 and receiving LSR MUST only advertise TA-Ids that they support. In 583 other words, what they are configured for over the tLDP session. In 584 addition, when there is no common targeted LDP application between 585 two LSRs due to administrative policy, the tLDP session SHOULD NOT be 586 established. 588 7. IANA Considerations 590 This document requires the assignment of a new code point for a 591 Capability Parameter TLVs from the IANA managed LDP registry "TLV 592 Type Name Space", corresponding to the advertisement of the Targeted 593 Applications capability. IANA is requested to assign the lowest 594 available value after 0x050B. 596 Value Description Reference 597 ----- -------------------------------- --------- 598 TBD1 Targeted Applications capability [this document] 600 This document requires the assignment of a new code point for a 601 status code from the IANA managed registry "STATUS CODE NAME SPACE" 602 on the Label Distribution Protocol (LDP) Parameters page, 603 corresponding to the notification of session Rejected/Targeted 604 Application Capability Mis-Match. IANA is requested to assign the 605 lowest available value after 0x0000004B. 607 Value Description Reference 608 ----- -------------------------------- --------- 609 TBD2 Session Rejected/Targeted 610 Application Capability Mis-Match [this document] 612 This document also creates a new name space 'the LDP Targeted 613 Application Identifier' on the Label Distribution Protocol (LDP) 614 Parameters page, that is to be managed by IANA. The range is 0x0001- 615 0xFFFE, with the following values requested in this document. 617 Value Description Reference 618 -------- ------------------------- --------------- 619 0x0000 Reserved [this document] 620 0x0001 LDPv4 Tunneling [this document] 621 0x0002 LDPv6 Tunneling [this document] 622 0x0003 mLDP Tunneling [this document] 623 0x0004 LDPv4 Remote LFA [this document] 624 0x0005 LDPv6 Remote LFA [this document] 625 0x0006 LDP FEC 128 PW [this document] 626 0x0007 LDP FEC 129 PW [this document] 627 0x0008 LDP Session Protection [this document] 628 0x0009 LDP ICCP [this document] 629 0x000A LDP P2MP PW [this document] 630 0x000B mLDP Node Protection [this document] 631 0x000C LDPv4 Intra-area FECs [this document] 632 0x000D LDPv6 Intra-area FECs [this document] 633 0x0001 - 0x1FFF Available for assignment 634 by IETF Review 635 0x2000 - 0F7FF Available for assignment 636 as first come first served 637 0xF800 - 0xFBFF Available for private use 638 0xFC00 - 0xFFFE Available for experimental use 639 0xFFFF Reserved [this document] 641 8. Acknowledgments 643 The authors wish to thank Nischal Sheth, Hassan Hosseini, Kishore 644 Tiruveedhul, Loa Andersson, Eric Rosen, Yakov Rekhter, Thomas 645 Beckhaus, Tarek Saad, Lizhong Jin and Bruno Decraene for doing the 646 detailed review. Thanks to Manish Gupta and Martin Ehlers for their 647 input to this work and many helpful suggestions. 649 9. Contributing Authors 651 Chris Bowers 652 Juniper Networks 653 1133 Innovation Way 654 Sunnyvale, CA 94089 655 USA 656 EMail: cbowers@juniper.net 658 Zhenbin Li 659 Huawei 660 Bld No.156 Beiqing Rd 661 Beijing 100095 662 China 663 Email: lizhenbin@huawei.com 665 10. References 667 10.1 Normative References 669 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 670 "LDP Specification", RFC 5036, October 2007, 671 . 673 [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. 674 Le Roux, "LDP Capabilities", RFC 5561, July 2009, 675 . 677 [RFC7473] Kamran Raza, Sami Boutros, "Controlling State 678 Advertisements of Non-negotiated LDP Applications", RFC 679 7473, March 2015, . 682 [RFC7715] IJ. Wijnands, E. Rosen, K. Raza, J. Tantsura, A. Atlas, Q. 683 Zhao, "mLDP Node Protection", RFC 7715, January 2016, 684 . 686 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 687 Requirement Levels", BCP 14, RFC 2119, March 1997, 688 . 690 10.2 Informative References 692 [RFC7490] S. Bryant, C. Filsfils, S. Previdi, M. Shand, N. So, 693 "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 694 April 2015. 696 [RFC6074] E. Rosen, B. Davie, V. Radoaca, and W. Luo, "Provisioning, 697 Auto-Discovery, and Signaling in Layer 2 Virtual Private 698 Networks (L2VPNs)", January 2011. 700 [RFC6388] IJ. Wijnands, I. Minei, K. Kompella, B. Thomas, "Label 701 Distribution Protocol Extensions for Point-to-Multipoint 702 and Multipoint-to-Multipoint Label Switched Paths", 703 November 2011. 705 Authors' Addresses 707 Santosh Esale 708 Juniper Networks 709 1133 Innovation Way 710 Sunnyvale, CA 94089 711 USA 712 EMail: sesale@juniper.net 714 Raveendra Torvi 715 Juniper Networks 716 10 Technology Park Drive 717 Westford, MA 01886 718 USA 719 EMail: rtorvi@juniper.net 721 Luay Jalil 722 Verizon 723 1201 E Arapaho Rd 724 Richardson, TX 75081 725 USA 726 Email: luay.jalil@verizon.com 728 Uma Chunduri 729 Huawei 730 2330 Central Expy 731 Santa Clara, CA 95050 732 USA 733 Email: uma.chunduri@huawei.com 735 Kamran Raza 736 Cisco Systems, Inc. 737 2000 Innovation Drive 738 Ottawa, ON K2K-3E8 739 Canada 740 E-mail: skraza@cisco.com