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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) ** Downref: Normative reference to an Informational RFC: RFC 4736 Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TEAS Working Group T. Saad, Ed. 3 Internet-Draft R. Gandhi, Ed. 4 Intended status: Standards Track Z. Ali 5 Expires: March 8, 2017 Cisco Systems, Inc. 6 R. Venator 7 Defense Information Systems Agency 8 Y. Kamite 9 NTT Communications Corporation 10 September 4, 2016 12 RSVP Extensions For Re-optimization of Loosely Routed 13 Point-to-Multipoint Traffic Engineering Label Switched Paths (LSPs) 14 draft-ietf-teas-p2mp-loose-path-reopt-06 16 Abstract 18 Re-optimization of a Point-to-Multipoint (P2MP) Traffic Engineered 19 (TE) Label Switched Path (LSP) may be triggered based on the need to 20 re-optimize an individual source-to-leaf (S2L) sub-LSP or a set of 21 S2L sub-LSPs, both using Sub-Group-Based Re-optimization method, or 22 the entire P2MP-TE LSP tree using the Make-Before-Break (MBB) method. 23 Mechanisms that facilitate path re-optimization of loosely routed 24 Point-to-Point (P2P) TE LSPs include a method for the ingress node to 25 trigger a new path re-evaluation request and a method for the mid- 26 point node to notify availability of a preferred path. This document 27 discusses the application of these mechanisms to the re-optimization 28 of loosely routed P2MP-TE LSPs, identifies issues in doing so and 29 proposes procedures to address them. 31 This document defines Resource Reservation Protocol (RSVP) signaling 32 extensions to allow the ingress node of a loosely routed P2MP-TE LSP 33 to request the re-evaluation of the entire LSP tree, and a mid-point 34 node to notify to the ingress node that a preferable tree exists for 35 the entire P2MP-TE LSP. For re-optimizing a group of S2L sub-LSPs in 36 a tree using the Sub-Group-Based Re-optimization method, an S2L sub- 37 LSP descriptor list can be used to signal one or more S2L sub-LSPs in 38 an RSVP message. This RSVP message may need to be fragmented when 39 large number of S2L sub-LSPs are added to the descriptor list. This 40 document introduces the notion of a fragment identifier to help 41 recipient nodes unambiguously reconstruct the fragmented S2L sub-LSP 42 descriptor list. 44 Status of this Memo 46 This Internet-Draft is submitted in full conformance with the 47 provisions of BCP 78 and BCP 79. 49 Internet-Drafts are working documents of the Internet Engineering 50 Task Force (IETF). Note that other groups may also distribute 51 working documents as Internet-Drafts. The list of current Internet- 52 Drafts is at http://datatracker.ietf.org/drafts/current/. 54 Internet-Drafts are draft documents valid for a maximum of six months 55 and may be updated, replaced, or obsoleted by other documents at any 56 time. It is inappropriate to use Internet-Drafts as reference 57 material or to cite them other than as "work in progress." 59 Copyright Notice 61 Copyright (c) 2016 IETF Trust and the persons identified as the 62 document authors. All rights reserved. 64 This document is subject to BCP 78 and the IETF Trust's Legal 65 Provisions Relating to IETF Documents 66 (http://trustee.ietf.org/license-info) in effect on the date of 67 publication of this document. Please review these documents 68 carefully, as they describe your rights and restrictions with respect 69 to this document. Code Components extracted from this document must 70 include Simplified BSD License text as described in Section 4.e of 71 the Trust Legal Provisions and are provided without warranty as 72 described in the Simplified BSD License. 74 Table of Contents 76 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 77 1.1. Loosely Routed Inter-domain P2MP-TE LSP Tree . . . . . . . 5 78 1.2. Existing Mechanism For Tree-Based P2MP-TE LSP 79 Re-optimization . . . . . . . . . . . . . . . . . . . . . 5 80 1.3. Existing Mechanism For Sub-Group-Based P2MP-TE LSP 81 Re-optimization . . . . . . . . . . . . . . . . . . . . . 6 82 2. Conventions Used in This Document . . . . . . . . . . . . . . 7 83 2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 7 84 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7 85 2.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 8 86 3. Signaling Procedure For Loosely Routed P2MP-TE LSP 87 Re-optimization . . . . . . . . . . . . . . . . . . . . . . . 8 88 3.1. Tree-Based Re-optimization . . . . . . . . . . . . . . . . 8 89 3.2. Sub-Group-Based Re-optimization Using Fragment 90 Identifier . . . . . . . . . . . . . . . . . . . . . . . . 9 91 4. Message and Object Definitions . . . . . . . . . . . . . . . . 10 92 4.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 10 93 4.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 10 94 4.3. Fragment Identifier For S2L sub-LSP Descriptor . . . . . . 11 95 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 12 96 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 97 6.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 12 98 6.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 13 99 6.3. Fragment Identifier For S2L sub-LSP Descriptor . . . . . . 13 100 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 101 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 102 8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 103 8.2. Informative References . . . . . . . . . . . . . . . . . . 15 104 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16 105 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 107 1. Introduction 109 This document defines Resource Reservation Protocol - Traffic 110 Engineering (RSVP-TE) [RFC2205] [RFC3209] signaling extensions for 111 re-optimizing loosely routed Point-to-Multipoint (P2MP) Traffic 112 Engineered (TE) Label Switched Paths (LSPs) [RFC4875] in a 113 Multi-Protocol Label Switching (MPLS) or Generalized MPLS (GMPLS) 114 network. 116 A P2MP-TE LSP is comprised of one or more source-to-leaf (S2L) 117 sub-LSPs. A loosely routed P2MP-TE S2L sub-LSP is defined as one 118 whose path does not contain the full explicit route identifying each 119 node along the path to the egress node at the time of its signaling 120 by the ingress node. Such an S2L sub-LSP is signaled with no 121 Explicit Route Object (ERO) [RFC3209], or with an ERO that contains 122 at least one loose hop, or with an ERO that contains an abstract node 123 which identifies more than one node. This is often the case with 124 inter-domain P2MP-TE LSPs where Path Computation Element (PCE) is not 125 used [RFC5440]. 127 As per [RFC4875], an ingress node may re-optimize the entire P2MP-TE 128 LSP by re-signaling all its S2L sub-LSP(s) or may re-optimize 129 individual or group of S2L sub-LSP(s) i.e. individual or group of 130 destination(s). 132 [RFC4736] defines RSVP signaling extensions for re-optimizing loosely 133 routed Point-to-Point (P2P) TE LSP(s) as follows: 135 o A mid-point LSR that expands loose next-hop(s) sends a solicited 136 or unsolicited PathErr with the Notify error code (25 as defined in 137 [RFC3209]) with sub-code 6 to indicate "Preferable Path Exists" to 138 the ingress node. 140 o An ingress node triggers a path re-evaluation request at all 141 mid-point LSR(s) that expands loose next-hop(s) by setting the "Path 142 Re-evaluation Request" flag (0x20) in SESSION_ATTRIBUTES Object in 143 the Path message. 145 o The ingress node upon receiving this PathErr either solicited or 146 unsolicited initiates re-optimization of the LSP with a different 147 LSP-ID. 149 The following sections discuss the issues that may arise when 150 applying the mechanisms defined in [RFC4736] for re-optimizing 151 loosely routed P2MP-TE LSPs. 153 1.1. Loosely Routed Inter-domain P2MP-TE LSP Tree 155 An example of a loosely routed inter-domain P2MP-TE LSP tree is shown 156 in Figure 1. In this example, the P2MP-TE LSP tree consists of 3 S2L 157 sub-LSPs, to destinations (i.e. leafs) R10, R11 and R12 from the 158 ingress node (i.e. source) R1. Nodes R2 and R5 are branch nodes and 159 nodes ABR3, ABR4, ABR7, ABR8 and ABR9 are area border routers. For 160 the S2L sub-LSP to destination R10, nodes ABR3, ABR7 and R10 are 161 defined as loose hops. For the S2L sub-LSP to destination R11, nodes 162 ABR3, ABR8 and R11 are defined as loose hops. For the S2L sub-LSP to 163 destination R12, nodes ABR4, ABR9 and R12 are defined as loose hops. 165 <--area1--><--area0--><-area2-> 167 ABR7---R10 168 / 169 / 170 ABR3---R5 171 / \ 172 / \ 173 R1---R2 ABR8---R11 174 \ 175 \ 176 ABR4---R6 177 \ 178 \ 179 ABR9---R12 181 Figure 1: An Example of Loosely Routed Inter-domain P2MP-TE LSP Tree 183 1.2. Existing Mechanism For Tree-Based P2MP-TE LSP Re-optimization 185 Mechanisms defined in [RFC4736] can be easily applied to trigger the 186 re-optimization of individual or group of S2L sub-LSP(s). However, 187 to apply these [RFC4736] mechanisms for triggering the 188 re-optimization of an entire P2MP-TE LSP tree, an ingress node needs 189 to send path re-evaluation requests on all (typically 100s of) S2L 190 sub-LSPs and the mid-point LSR needs to send notify PathErrs for all 191 S2L sub-LSPs. Such mechanisms may lead to the following issues: 193 o A mid-point LSR that expands loose next-hop(s) may have to 194 accumulate the received path re-evaluation request(s) for all S2L 195 sub-LSPs (e.g. by using a wait timer) and interpret them as a 196 re-optimization request for the whole P2MP-TE LSP tree. Otherwise, a 197 mid-point LSR may prematurely notify "Preferable Path Exists" for one 198 or a sub-set of S2L sub-LSPs. 200 o Similarly, the ingress node may have to heuristically determine 201 when to perform entire P2MP-TE LSP tree re-optimization and when to 202 perform S2L sub-LSP re-optimization. For example, an implementation 203 may choose to delay re-optimization long enough to allow all 204 PathErr(s) to be received. Such timer-based procedures may produce 205 undesired results. 207 o The ingress node that receives (un)solicited PathErr 208 notification(s) for individual S2L sub-LSP(s), may prematurely start 209 re-optimizing the sub-set of S2L sub-LSPs. However, as mentioned in 210 [RFC4875] Section 14.2, such sub-group based re-optimization 211 procedure may result in data duplication that can be avoided if the 212 entire P2MP-TE LSP tree is re-optimized using a different LSP-ID, 213 especially if the ingress node eventually receives PathErr 214 notifications for all S2L sub-LSPs of the P2MP-TE LSP tree. 216 In order to address above mentioned issues and to align 217 re-optimization of P2MP-TE LSP with P2P LSP [RFC4736], there is a 218 need for a mechanism to trigger re-optimization of the LSP tree by 219 re-signaling all S2L sub-LSPs with a different LSP-ID. To meet this 220 requirement, this document defines RSVP-TE signaling extensions for 221 the ingress node to trigger the re-evaluation of the P2MP LSP tree on 222 every hop that has a next-hop defined as a loose or abstract hop for 223 one or more S2L sub-LSP path, and a mid-point LSR to signal to the 224 ingress node that a preferable LSP tree exists (compared to the 225 current path) or that the whole P2MP-TE LSP must be re-optimized 226 (because of maintenance required on the TE LSP path). 228 1.3. Existing Mechanism For Sub-Group-Based P2MP-TE LSP Re-optimization 230 Applying the procedures discussed in RFC4736 in conjunction with the 231 Sub-Group-Based Re-Optimization procedures ([RFC4875], Section 14.2), 232 an ingress node MAY trigger path re-evaluation requests for a set of 233 S2L sub-LSPs in a single Path message using S2L sub-LSP descriptor 234 list. Similarly, a mid-point LSR may send a PathErr message (with 235 Error code 25, sub-code 6) containing a list of S2L sub-LSPs 236 transiting through the LSR using an S2L sub-LSP descriptor list to 237 notify the ingress node. This method can be used for re-optimizing a 238 sub-group of S2L sub-LSPs within an LSP tree using the same LSP-ID. 239 This method can alleviate the scale issue associated with sending 240 RSVP messages for individual S2L sub-LSPs. However, this procedure 241 can lead to the following issues when used to re-optimize the LSP 242 tree: 244 o Path message that is intended to carry the path re-evaluation 245 request as defined in [RFC4736] with a full list of S2L sub-LSPs in 246 S2L sub-LSPs descriptor list will be decomposed at branching LSRs, 247 and only a subset of the S2L sub-LSPs that are routed over the same 248 next-hop will be added in the descriptor list of the Path message 249 propagated to downstream mid-point LSRs. Consequently, when a 250 preferable path exists at such mid-point LSRs, the PathErr can only 251 include the sub-set of S2L sub-LSPs traversing the LSR. In this 252 case, at the ingress node there is no way to distinguish which mode 253 of re-optimization to invoke, i.e. sub-group based re-optimization 254 using the same LSP-ID or tree based re-optimization using a different 255 LSP-ID. 257 o An LSR may fragment a large RSVP message (when a combined message 258 may not be large enough to fit all S2L sub-LSPs). In this case, the 259 ingress node may receive multiple PathErrs with sub-sets of S2L sub- 260 LSPs in each (due to either the combined Path message getting 261 fragmented or the combined PathErr message getting fragmented) and 262 would require additional logic to determine how to re-optimize the 263 LSP tree (for example, waiting for some time to aggregate all 264 possible PathErr messages before taking an action). When fragmented, 265 RSVP messages may arrive out of order, and the receiver has no way of 266 knowing the beginning and end of the S2L sub-LSP list. 268 In order to address the above mentioned issues caused by RSVP message 269 fragmentation, this document proposes the use of fragment identifier 270 for the S2L sub-LSP descriptor list when combining large number of 271 S2L sub-LSPs in an RSVP message. 273 2. Conventions Used in This Document 275 2.1. Key Word Definitions 277 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 278 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 279 document are to be interpreted as described in [RFC2119]. 281 2.2. Abbreviations 283 ABR: Area Border Router. 285 AS: Autonomous System. 287 ERO: Explicit Route Object. 289 LSR: Label Switching Router. 291 TE LSP: Traffic Engineering Label Switched Path. 293 TE LSP ingress: Head-end/source of the TE LSP. 295 TE LSP egress: Tail-end/destination of the TE LSP. 297 2.3. Terminology 299 Domain: Routing or administrative domain such as an IGP area and an 300 autonomous system. 302 Interior Gateway Protocol Area (IGP Area): OSPF area or IS-IS level. 304 Inter-area TE LSP: A TE LSP whose path transits across at least two 305 different IGP areas. 307 Inter-AS MPLS TE LSP: A TE LSP whose path transits across at least 308 two different Autonomous Systems (ASes) or sub-ASes (BGP 309 confederations). 311 S2L sub-LSP: Source-to-leaf sub Label Switched Path. 313 The reader is assumed to be familiar with the terminology in 314 [RFC4875] and [RFC4736]. 316 3. Signaling Procedure For Loosely Routed P2MP-TE LSP Re-optimization 318 3.1. Tree-Based Re-optimization 320 To evaluate an entire P2MP-TE LSP tree on mid-point LSRs that expand 321 loose next-hop(s), an ingress node MAY send a Path message with 322 "P2MP-TE Tree Re-evaluation Request" defined in this document. The 323 ingress node SHOULD select one of the S2L sub-LSPs of the P2MP-TE LSP 324 tree transiting a mid-point LSR to trigger the re-evaluation request. 325 The ingress node MAY send a re-evaluation request to each border LSR 326 on the path of the LSP tree. 328 A mid-point LSR that expands loose next-hop(s) for one or more S2L 329 sub-LSP path(s) SHOULD do the following upon receiving a Path message 330 with the "P2MP-TE Tree Re-evaluation Request" bit set: 332 o The mid-point LSR SHOULD check for a preferable P2MP-TE LSP tree 333 by re-evaluating all S2L sub-LSP(s) that are expanded paths of the 334 loose next-hops of the P2MP-TE LSP. 336 o If a preferable P2MP-TE LSP tree is found, the mid-point LSR MAY 337 send an RSVP PathErr to the ingress node with Error code 25 (Notify 338 Error) defined in [RFC3209] and sub-code "Preferable P2MP-TE Tree 339 Exists" defined in this document. The mid-point LSR, in turn, SHOULD 340 NOT propagate the "P2MP-TE Tree Re-evaluation Request" bit in 341 subsequent RSVP Path messages sent downstream for the re-evaluated 342 P2MP-TE LSP. 344 o If no preferable tree for P2MP-TE LSP can be found, the 345 recommended mode is that the mid-point LSR that expands loose next- 346 hop(s) for one or more S2L sub-LSP path(s) SHOULD propagate the 347 request downstream by setting the "P2MP-TE Tree Re-evaluation 348 Request" bit in the LSP_ATTRIBUTES Object of RSVP Path message. 350 A mid-point LSR MAY send an unsolicited PathErr message with 351 "Preferable P2MP-TE Tree Exists" PathErr to the ingress node to 352 notify of a preferred P2MP-TE LSP tree when it determines it exists. 353 In this case, the mid-point LSR that expands loose next-hop(s) for 354 one or more S2L sub-LSP path(s) SHOULD select one of the S2L sub- 355 LSP(s) of the P2MP-TE LSP tree to send this PathErr message to the 356 ingress node. 358 The sending of an RSVP PathErr Notify message "Preferable P2MP-TE 359 Tree Exists" to the ingress node SHALL notify the ingress node of the 360 existence of a preferable P2MP-TE LSP tree and upon receiving this 361 PathErr, the ingress node MAY trigger re-optimization of the LSP 362 using a different LSP-ID. 364 3.2. Sub-Group-Based Re-optimization Using Fragment Identifier 366 It might be preferable, as per [RFC4875], to re-optimize the entire 367 P2MP-TE LSP by re-signaling all of its S2L sub-LSP(s) (Section 14.1, 368 "Make-before-Break") or to re-optimize individual or group of S2L 369 sub-LSP(s) i.e. individual or group of destination(s) (Section 14.2 370 "Sub-Group-Based Re-Optimization" in [RFC4875]), both using the same 371 LSP-ID. For loosely routed S2L sub-LSPs, this can be achieved by 372 using the procedures defined in [RFC4736] to re-optimize one or more 373 S2L sub-LSP(s) of the P2MP-TE LSP. 375 An ingress node may trigger path re-evaluation requests using the 376 procedures defined in [RFC4736] for a set of S2L sub-LSPs by 377 combining multiple Path messages using an S2L sub-LSP descriptor list 378 [RFC4875]. An S2L sub-LSP descriptor list is created using a series 379 of S2L_SUB_LSP Objects as defined in [RFC4875]. Similarly, a mid- 380 point LSR may send a PathErr message (with Error code 25, sub-code 6, 381 Preferable Path Exists) containing a list of S2L sub-LSPs transiting 382 through the LSR using an S2L sub-LSP descriptor list to notify the 383 ingress node of preferable paths available. 385 As per [RFC4875] (Section 5.2.3, "Transit Fragmentation of Path State 386 Information"), when a Path message is not large enough to fit all S2L 387 sub-LSPs in the descriptor list, an LSR may fragment the message. In 388 this case, the LSR MAY add S2L_SUB_LSP_FRAG Object defined in this 389 document in the S2L sub-LSP descriptor list to be able to rebuild the 390 list from the received fragments that may arrive out of order. 392 The S2L_SUB_LSP_FRAG Object defined in this document is optional. 393 However, a node MUST add the S2L_SUB_LSP_FRAG Object for each 394 fragment in S2L sub-LSP descriptor list when the RSVP message needs 395 to be fragmented. 397 A mid-point LSR SHOULD wait to accumulate all S2L sub-LSPs before 398 attempting to re-evaluate preferable path when a Path message for 399 "Path Re-evaluation Request" is received with S2L_SUB_LSP_FRAG 400 Object. If a mid-point LSR does not receive all fragments of the 401 Path message (for example, when fragments are lost), it SHOULD 402 trigger re-evaluation of all S2L sub-LSPs of the P2MP-TE LSP 403 transiting on the node. An ingress node SHOULD wait to accumulate 404 all S2L sub-LSPs before attempting to trigger re-optimization when a 405 PathErr message with "Preferable Path Exists" is received with a 406 S2L_SUB_LSP_FRAG Object. If an ingress node does not receive all 407 fragments of the PathErr message (for example, when fragments are 408 lost), it SHOULD trigger re-optimization of all S2L sub-LSPs of the 409 P2MP-TE LSP transiting on the mid-point node that had sent the 410 PathErr message. 412 The new object S2L_SUB_LSP_FRAG defined in this document has a wider 413 applicability other than the P2MP-TE LSP re-optimization but it is 414 outside the scope of this document. 416 4. Message and Object Definitions 418 4.1. P2MP-TE Tree Re-evaluation Request Flag 420 In order to trigger a tree re-evaluation request, a new flag is 421 defined in Attributes Flags TLV of the LSP_ATTRIBUTES Object 422 [RFC5420] as follows: 424 Bit Number (to be assigned by IANA): P2MP-TE Tree Re-evaluation 425 Request flag 427 The "P2MP-TE Tree Re-evaluation Request" flag is meaningful in a Path 428 message of a P2MP-TE S2L sub-LSP and is inserted by the ingress node. 430 4.2. Preferable P2MP-TE Tree Exists Path Error Sub-code 431 In order to indicate to an ingress node that a preferable P2MP-TE LSP 432 tree exists, the following new sub-code for PathErr code 25 (Notify 433 Error) [RFC3209] is defined: 435 Sub-code (to be assigned by IANA): Preferable P2MP-TE Tree Exists 436 sub-code 438 When a preferable path for P2MP-TE LSP tree exists, the mid-point LSR 439 sends a solicited or unsolicited "Preferable P2MP-TE Tree Exists" 440 PathErr notification to the ingress node of the P2MP-TE LSP. 442 4.3. Fragment Identifier For S2L sub-LSP Descriptor 444 An S2L_SUB_LSP Object [RFC4875] identifies a particular S2L sub-LSP 445 belonging to the P2MP-TE LSP. An S2L sub-LSP descriptor list is 446 created using a series of S2L_SUB_LSP Objects as defined in 447 [RFC4875]. The RSVP message may need to be fragmented due to large 448 number of S2L sub-LSPs added in the descriptor list, and such 449 fragments may be received our of order. To be able to rebuild the 450 fragmented S2L sub-LSP descriptor list correctly, the following new 451 type is defined for the S2L_SUB_LSP Object [RFC4875] to identify the 452 fragments. 454 S2L_SUB_LSP_FRAG: Class-Num 50, C-Type TBA3 by IANA 456 +---------------+---------------+---------------+---------------+ 457 | Length (12 bytes) | Class-Num 50 | C-Type TBA3 | 458 +---------------+---------------+---------------+---------------+ 459 | Reserved | Fragment ID | 460 +---------------+---------------+---------------+---------------+ 461 | Fragments Total | Fragment Number | 462 +---------------+---------------+---------------+---------------+ 464 Fragment ID: 16-bit integer in the range of 1 to 65535. This value 465 is incremented for each new RSVP message that needs to be 466 fragmented. The scope of the fragment ID is limited to the RSVP 467 message type (e.g. Path) carrying the fragment. In other words, 468 fragment IDs do not have any correlation between different RSVP 469 message types (e.g. Path and PathErr). 471 Fragments Total: 16-bit integer in the range of 1 to 65535. This 472 value indicates the number of fragments sent for the given RSVP 473 message. 475 Fragment Number: 16-bit integer in the range of 1 to 65535. This 476 value indicates the position of this fragment in the given RSVP 477 message. 479 The S2L_SUB_LSP_FRAG Object is added before adding the 480 S2L_SUB_LSP_IPv4 or S2L_SUB_LSP_IPv6 Object in the fragmented RSVP 481 message. 483 5. Compatibility 485 The LSP_ATTRIBUTES Object has been defined in [RFC5420] with class 486 numbers in the form 11bbbbbb, which ensures compatibility with 487 non-supporting nodes. Per [RFC2205], nodes not supporting this 488 extension will ignore the new flag defined in this document but 489 forward it without modification. 491 The S2L_SUB_LSP_FRAG Object has been defined with class numbers in 492 the form 11bbbbbb, which ensures compatibility with non-supporting 493 nodes. Per [RFC2205], nodes not supporting new S2L_SUB_LSP_FRAG 494 Object will ignore them but forward it without modification. 496 6. IANA Considerations 498 IANA is requested to administer assignment of new values for 499 namespace defined in this document and summarized in this section. 501 6.1. P2MP-TE Tree Re-evaluation Request Flag 503 IANA maintains a name space for RSVP-TE TE parameters "Resource 504 Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters" (see 505 http://www.iana.org/assignments/rsvp-te-parameters). From the 506 registries in this name space "Attribute Flags", allocation of new 507 flag is requested (Section 4.1). 509 The following new flag is defined for the Attributes Flags TLV in the 510 LSP_ATTRIBUTES Object [RFC5420]. The numeric value is to be assigned 511 by IANA. 513 o P2MP-TE Tree Re-evaluation Request Flag: 515 +--------+---------------+---------+---------+---------+------------+ 516 | Bit No | Attribute | Carried | Carried | Carried | Reference | 517 | | Flag Name | in Path | in Resv | in RRO | | 518 +--------+---------------+---------+---------+---------+------------+ 519 | TBA1 by| P2MP-TE Tree | Yes | No | No | This | 520 | IANA | Re-evaluation | | | | document | 521 +--------+---------------+---------+---------+---------+------------+ 523 6.2. Preferable P2MP-TE Tree Exists Path Error Sub-code 525 IANA maintains a name space for RSVP protocol parameters "Resource 526 Reservation Protocol (RSVP) Parameters" (see 527 http://www.iana.org/assignments/rsvp-parameters). From the 528 sub-registry "Sub-Codes - 25 Notify Error" in registry "Error Codes 529 and Globally-Defined Error Value Sub-Codes", allocation of a new 530 error code is requested (Section 4.2). 532 As defined in [RFC3209], the Error Code 25 in the ERROR SPEC Object 533 corresponds to a Notify Error PathErr. This document adds a new 534 sub-code for this PathErr as follows: 536 o Preferable P2MP-TE Tree Exists sub-code: 538 +----------+--------------------+---------+---------+-----------+ 539 | Sub-code | Sub-code | PathErr | PathErr | Reference | 540 | value | Description | Code | Name | | 541 +----------+--------------------+---------+---------+-----------+ 542 | TBA2 by | Preferable P2MP-TE | 25 | Notify | This | 543 | IANA | Tree Exists | | Error | document | 544 +----------+--------------------+---------+---------+-----------+ 546 6.3. Fragment Identifier For S2L sub-LSP Descriptor 548 IANA maintains a name space for RSVP protocol parameters "Resource 549 Reservation Protocol (RSVP) Parameters" (see 550 http://www.iana.org/assignments/rsvp-parameters). From the 551 sub-registry "Class Types or C-Types 50 S2L_SUB_LSP" in registry 552 "Class Names, Class Numbers, and Class Types", allocation of new 553 C-Types is requested (Section 4.3). 555 As defined in [RFC4875], S2L_SUB_LSP Object is defined with 556 Class-Number 50 to identify a particular S2L sub-LSP belonging to the 557 P2MP-TE LSP. This document adds one new object type for this object 558 as follows: 560 o S2L_SUB_LSP_FRAG Object type: 562 +-----------------+---------------------------+-----------------+ 563 | C-Type value | Description | Reference | 564 +-----------------+---------------------------+-----------------+ 565 | TBA3 by IANA | S2L_SUB_LSP_FRAG | This document | 566 +-----------------+---------------------------+-----------------+ 568 7. Security Considerations 570 This document defines RSVP-TE signaling extensions to allow an 571 ingress node of a P2MP-TE LSP to request the re-evaluation of the 572 entire LSP tree, and for a mid-point LSR to notify the ingress node 573 of the existence of a preferable tree by sending a PathErr. As per 574 [RFC4736], in the case of a P2MP-TE LSP S2L sub-LSP spanning multiple 575 domains, it may be desirable for a mid-point LSR to modify the RSVP 576 PathErr message defined in this document to preserve confidentiality 577 across domains. Furthermore, an ingress node may decide to ignore 578 this PathErr message coming from a mid-point LSR residing in another 579 domain. Similarly, a mid-point LSR may decide to ignore the P2MP-TE 580 tree re-evaluation request originating from another ingress domain. 582 This document also defines fragment identifier for the S2L sub-LSP 583 descriptor list when combining large number of S2L sub-LSPs in an 584 RSVP message and the message needs to be fragmented. The 585 introduction of the fragment identifier, by itself, introduce no 586 additional information to signaling. For a general discussions on 587 MPLS and GMPLS related security issues, see the MPLS/GMPLS security 588 framework [RFC5920]. 590 8. References 592 8.1. Normative References 594 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 595 Requirement Levels", BCP 14, RFC 2119, March 1997. 597 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. 598 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 599 Functional Specification", RFC 2205, September 1997. 601 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 602 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 603 Tunnels", RFC 3209, December 2001. 605 [RFC4736] Vasseur, JP., Ikejiri, Y. and Zhang, R, "Reoptimization of 606 Multiprotocol Label Switching (MPLS) Traffic Engineering 607 (TE) Loosely Routed Label Switched Path (LSP)", RFC 4736, 608 November 2006. 610 [RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, 611 "Extensions to Resource Reservation Protocol Traffic 612 Engineering (RSVP-TE) for Point-to-Multipoint TE Label 613 Switched Paths (LSPs)", RFC 4875, May 2007. 615 [RFC5420] Farrel, A., Papadimitriou, D., Vasseur, JP., and Ayyangar, 616 A., "Encoding of Attributes for MPLS LSP Establishment 617 Using Resource Reservation Protocol Traffic Engineering 618 (RSVP-TE)", RFC 5420, February 2009. 620 8.2. Informative References 622 [RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation 623 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 624 March 2009. 626 [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS 627 Networks", RFC 5920, July 2010. 629 Acknowledgments 631 The authors would like to thank Loa Andersson, Sriganesh Kini, Curtis 632 Villamizar, Dimitri Papadimitriou, Nobo Akiya and Vishnu Pavan Beeram 633 for reviewing this document and providing many useful comments and 634 suggestions. The authors would also like to thank Ling Zeng with 635 Cisco Systems for implementing mechanisms defined in this document. 637 Author's Addresses 639 Tarek Saad (editor) 640 Cisco Systems 642 EMail: tsaad@cisco.com 644 Rakesh Gandhi (editor) 645 Cisco Systems 647 EMail: rgandhi@cisco.com 649 Zafar Ali 650 Cisco Systems 652 EMail: zali@cisco.com 654 Robert H. Venator 655 Defense Information Systems Agency 657 EMail: robert.h.venator.civ@mail.mil 659 Yuji Kamite 660 NTT Communications Corporation 662 EMail: y.kamite@ntt.com