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'MPLS-MCAST-ENCAPS' ** Obsolete normative reference: RFC 3036 (Obsoleted by RFC 5036) == Outdated reference: A later version (-01) exists of draft-minei-mpls-ldp-p2mp-00 Summary: 7 errors (**), 0 flaws (~~), 8 warnings (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Aggarwal 3 Internet Draft Juniper Networks 4 Expiration Date: September 2006 5 J. L. Le Roux 6 France Telecom 8 March 2006 10 MPLS Upstream Label Assignment for LDP 12 draft-ietf-mpls-ldp-upstream-00.txt 14 Status of this Memo 16 By submitting this Internet-Draft, each author represents that any 17 applicable patent or other IPR claims of which he or she is aware 18 have been or will be disclosed, and any of which he or she becomes 19 aware will be disclosed, in accordance with Section 6 of BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt. 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 Abstract 39 This document describes procedures for distributing upstream-assigned 40 labels for Label Distribution Protocol (LDP). It also describes how 41 these procedures can be used for avoiding branch LSR traffic 42 replication on a LAN for LDP point-to-multipoint (P2MP)LSPs. 44 Table of Contents 46 1 Specification of requirements ......................... 2 47 2 Introduction .......................................... 2 48 3 LDP Upstream Label Assignment Capability .............. 3 49 4 Distributing Upstream-Assigned Labels in LDP .......... 4 50 4.1 Procedures ............................................ 4 51 5 LDP Tunnel Identifier Exchange ........................ 5 52 6 LDP Point-to-Multipoint LSPs on a LAN ................. 6 53 7 Acknowledgements ...................................... 7 54 8 References ............................................ 7 55 8.1 Normative References .................................. 7 56 8.2 Informative References ................................ 8 57 9 Author Information .................................... 8 58 10 Intellectual Property Statement ....................... 8 59 11 Full Copyright Statement .............................. 9 61 1. Specification of requirements 63 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 64 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 65 document are to be interpreted as described in [RFC2119]. 67 2. Introduction 69 This document describes procedures for distributing upstream-assigned 70 labels [MPLS-UPSTREAM] for Label Distribution Protocol (LDP). These 71 procedures follow the architecture for MPLS Upstream Label Assignment 72 described in [MPLS-UPSTREAM]. 74 This document describes extensions to LDP that a LSR can use to 75 advertise to its neighboring LSRs whether the LSR supports upstream 76 label assignment. 78 This document also describes extensions to LDP to distribute 79 upstream-assigned labels. 81 The usage of MPLS upstream label assignment using LDP for avoiding 82 branch LSR traffic replication on a LAN for LDP P2MP LSPs [LDP-P2MP1, 83 LDP-P2MP2] is also described. 85 3. LDP Upstream Label Assignment Capability 87 According to [MPLS-UPSTREAM], upstream-assigned label bindings MUST 88 NOT be used unless it is known that a downstream LSR supports them. 89 This implies that there MUST be a mechanism to enable a LSR to adver- 90 tise to its LDP neighbor LSR(s) its support of upstream-assigned 91 labels. 93 A new optional parameter, the LDP Capability TLV, is introduced to 94 allow LDP peers to exchange capabilities as part of LDP Initializa- 95 tion messages. This TLV contains one or more sub-TLVs, each to sig- 96 nal a specific capability. LDP Capability TLV and detailed procedures 97 for supporting LDP Capability signaling will be described in a sepa- 98 rate document. 100 A Upstream Label Assignment Capability sub-TLV is introduced to sig- 101 nal a LSR's support of upstream label assignment, to its LDP peers. 102 This sub-TLV is carried in the LDP Capability TLV. 104 Following is the format of the LDP Capability TLV: 106 0 1 2 3 107 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 1 108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 109 |1|0| Capability TLV (TBD) | Length (= 4) | 110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 111 | Sub-TLVs... | 112 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 114 Following is the format of the Upstream Label Assignment Capability 115 sub-TLV: 117 0 1 2 3 118 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 1 119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 |Upstream Lbl Ass Cap = 1 | Length (= 4) | 121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 | Reserved | 123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 If a LSR includes the Upstream Label Assignment Capability sub-TLV in 126 LDP Initialization Messages it implies that the LSR is capable of 127 both distributing upstream-assigned label bindings and receiving 128 upstream-assigned label bindings. Reserved bits MUST be set to zero 129 on transmission and MUST be ignored on receipt. 131 4. Distributing Upstream-Assigned Labels in LDP 133 An optional LDP TLV, Upstream-Assigned Label Request TLV, is intro- 134 duced. This TLV MUST be carried in a Label Request message if an 135 upstream-assigned label is being requested. 137 0 1 2 3 138 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 1 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 |0|0| Upstream Ass Lbl Req (TBD)| Length | 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 | Reserved | 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 An optional LDP TLV, Upstream-Assigned Label TLV is introduced to 146 signal an upstream-assigned label. Upstream-Assigned Label TLVs are 147 carried by the messages used to advertise, release and withdraw 148 upstream assigned label mappings. 150 0 1 2 3 151 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 1 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 |0|0| Upstream Ass Label (TBD) | Length | 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 | Reserved | 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 | Label | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 Label 162 This is a 20-bit label value as specified in [RFC3032] represented as 163 a 20-bit number in a 4 octet field. 165 4.1. Procedures 167 Procedures for Label Mapping, Label Request, Label Abort, Label With- 168 draw and Label Release follow [RFC3036] other than the modifications 169 pointed out in this section. 171 A LDP LSR MUST NOT distribute the Upstream Assigned Label TLV to a 172 neighboring LSR if the neighboring LSR had not previously advertised 173 the Upstream Label Assignment Capability in its LDP Initialization 174 messages. A LDP LSR MUST NOT send the Upstream Assigned Label 175 Request TLV to a neighboring LSR if the neighboring LSR had not pre- 176 viously advertised the Upstream Label Assignment Capability in its 177 LDP Initialization messages. 179 As described in [MPLS-UPSTREAM] the distribution of upstream-assigned 180 labels is similar to either ordered LSP control or independent LSP 181 control of the downstream assigned labels. 183 When the label distributed in a Label Mapping message is an upstream- 184 assigned label, the Upstream Assigned Label TLV MUST be included in 185 the Label Mapping message. When a LSR receives a Label Mapping mes- 186 sage with an Upstream Assigned Label TLV and if it does not recognize 187 the TLV, it MUST generate a Notification message with a status code 188 of "Unknown TLV" [RFC3036]. If it does recognize the TLV but is 189 unable to process the upstream label, it MUST generate a Notification 190 message with a status code of "No Label Resources". If the Label Map- 191 ping message was generated in response to a Label Request message, 192 the Label Request message MUST contain an Upstream Assigned Label 193 Request TLV. A LSR that generates an upstream assigned label request 194 to a neighbor LSR, for a given FEC, MUST NOT send a downstream label 195 mapping to the neighbor LSR for that FEC unless it withdraws the 196 upstream-assigned label binding. Similarly if a LSR generates a down- 197 stream assigned label request to a neighbor LSR, for a given FEC, it 198 MUST NOT send an upstream label mapping to that LSR for that FEC, 199 unless it aborts the downstream assigned label request. 201 The Upstream Assigned Label TLV may be optionally included in Label 202 Withdraw and Label Release messages that withdraw/release a particu- 203 lar upstream assigned label binding. 205 5. LDP Tunnel Identifier Exchange 207 As described in [MPLS-UPSTREAM] an upstream LSR Ru MAY transmit a 208 MPLS packet, the top label of which (L) is upstream-assigned, to a 209 downstream LSR Rd, by encapsulating it in an IP or MPLS tunnel. In 210 this case the fact that L is upstream-assigned is determined by Rd by 211 the tunnel on which the packet is received. There must be a mechanism 212 for Ru to inform Rd that a particular tunnel from Ru to Rd will be 213 used by Ru for transmitting MPLS packets with upstream-assigned MPLS 214 labels. 216 When LDP is used for upstream label assignment, the Interface ID TLV 217 [RFC3472] is used for signaling the Tunnel Identifier. If Ru uses an 218 IP or MPLS tunnel to transmit MPLS packets with upstream assigned 219 labels to Rd, Ru MUST include the Interface ID TLV in the Label Map- 220 ping messages along with the Upstream Assigned Label TLV. Two new 221 Interface ID TLVs are introduced to support RSVP-TE P2MP LSPs and IP 222 Multicast Tunnels. The TLV value acts as the tunnel identifier. 224 1. RSVP-TE P2MP LSP TLV. Type = TBD. Value of the TLV is the RSVP-TE 225 P2MP Session Object and optionally the P2MP Sender Template Object 226 [RSVP-TE-P2MP]. The TLV value identifies the RSVP-TE P2MP LSP. It 227 allows Ru to tunnel an "inner" LDP P2MP LSP, the label for which is 228 upstream assigned, over an "outer" RSVP-TE P2MP LSP that has leaves 229 . The P2MP LSP IF_ID TLV allows Ru to signal to 230 the binding of the inner LDP P2MP LSP to the outer RSVP- 231 TE P2MP LSP. The control plane signaling between Ru and 232 for the inner P2MP LSP uses targeted LDP signaling messages 234 2. IP Multicast Tunnel TLV. Type = TBD. In this case the TLV value is 235 a tuple. 237 6. LDP Point-to-Multipoint LSPs on a LAN 239 This section describes one application of upstream label assignment 240 using LDP. Further applications are to be described in separate docu- 241 ments. 243 [LDP-P2MP1, LDP-P2MP2] describe how to setup P2MP LSPs using LDP. On 244 a LAN the solution relies on "ingress replication". A LSR on a LAN, 245 that is a branch LSR for a P2MP LSP, (say Ru) sends a separate copy 246 of a packet that it receives on the P2MP LSP to each of the down- 247 stream LSRs on the LAN (say that are adjacent to it in 248 the P2MP LSP. 250 It is desirable for Ru to send a single copy of the packet for the 251 LDP P2MP LSP on the LAN, when there are multiple downstream routers 252 on the LAN that are adjacent to Ru in that LDP P2MP LSP. This 253 requires that each of must be able to associate the label 254 L, used by Ru to transmit packets for the P2MP LSP on the LAN, with 255 that P2MP LSP. It is possible to achieve this using LDP upstream- 256 assigned labels with the following procedures. 258 Consider a LSR Rd that receives the LDP P2MP FEC [LDP-P2MP1, LDP- 259 P2MP2] from its downstream LDP peer. Further the upstream interface 260 to reach LSR Ru which is the next-hop to the P2MP LSP root address, 261 Pr, in the LDP P2MP FEC, is a LAN interface. Further Rd and Ru sup- 262 port upstream-assigned labels. In this case Rd instead of sending a 263 Label Mapping message as described in [LDP-P2MP1, LDP-P2MP2] sends a 264 Label Request message to Ru. This Label Request message MUST contain 265 an Upstream Assigned Label Request TLV. Ru on receiving this message 266 sends back a Label Mapping message to Rd with an upstream-assigned 267 label. Processing of the Label Request and Label Mapping messages for 268 LDP upstream-assigned labels is as described in section 4.2. If Ru 269 receives a Label Request for an upstream assigned label for the same 270 P2MP FEC from multiple downstream LSRs on the LAN, , it 271 MUST send the same upstream-assigned label to each of . Ru 272 transmits the MPLS packet with an upstream-assigned label on the LAN 273 using the procedures defined in [MPLS-UPSTREAM] and [MPLS-MCAST- 274 ENCAPS]. 276 Note that may have more than one equal cost next-hop on 277 the LAN to reach Pr. In this case they MAY be configured to send the 278 upstream assigned label request to the next-hop LSR with the lowest 279 Router ID, if it is desirable for all of them to send the label 280 request to the same upstream LSR. It is also to be noted that these 281 procedures can still be used by Rd and Ru if other LSRs on the LAN do 282 not support upstream label assignment. Ingress replication and down- 283 stream label assignment will continue to be used for LSRs that do not 284 support upstream label assignment. 286 7. Acknowledgements 288 Thanks to Yakov Rekhter for his contribution. Thanks to Ina Minei and 289 Thomas Morin for their comments. 291 8. References 293 8.1. Normative References 295 [RFC3031] "MPLS Architecture", E. Rosen, A. Viswanathan, R. Callon, 296 RFC 3031. 298 [MPLS-UPSTREAM] R. Aggarwal, Y. Rekhter, E. Rosen, "MPLS Upstream 299 Label Assignment and Context Specific Label Space", draft-ietf-mpls- 300 upstream-label-00.txt 302 [MPLS-MCAST-ENCAPS] T. Eckert, E. Rosen, R. Aggarwal, Y. Rekhter, 303 draft-ietf-mpls-codepoint-00.txt 305 [RFC2119] "Key words for use in RFCs to Indicate Requirement Lev- 306 els.", Bradner, March 1997 308 [RFC3472] Ashwood-Smith, P. and L. Berger, Editors, " Generalized 309 Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based 310 Routed Label Distribution Protocol (CR-LDP) Extensions", RFC 3472, 311 January 2003. 313 [RFC3471] Berger, L. Editor, "Generalized Multi-Protocol Label 314 Switching (GMPLS) Signaling Functional Description", RFC 3471 January 315 2003. 317 [RFC3036] L. Andersson, et. al., "LDP Specification", January 2001. 319 8.2. Informative References 321 [MVPN] E. Rosen, R. Aggarwal [Editors], "Multicast in BGP/MPLS VPNs" 323 [RSVP-TE-P2MP] R. Aggarwal, D. Papadimitriou, S. Yasukawa [Editors], 324 "Extensions to RSVP-TE for Point to Multipoint TE LSPs" 326 [LDP-P2MP1] I. Minei et. al, "Label Distribution Protocol Extensions 327 for Point-to-Multipoint Label Switched Paths", draft-minei-mpls-ldp- 328 p2mp-00.txt 330 [LDP-P2MP2] I. Wijnands et. al., "Multicast Extensions for LDP", 331 draft-wijnands-mpls-ldp-mcast-ext-00.txt 333 9. Author Information 335 Rahul Aggarwal 336 Juniper Networks 337 1194 North Mathilda Ave. 338 Sunnyvale, CA 94089 339 Email: rahul@juniper.net 341 Jean-Louis Le Roux 342 France Telecom 343 2, avenue Pierre-Marzin 344 22307 Lannion Cedex 345 France 346 E-mail: jeanlouis.leroux@francetelecom.com 348 10. Intellectual Property Statement 350 The IETF takes no position regarding the validity or scope of any 351 Intellectual Property Rights or other rights that might be claimed to 352 pertain to the implementation or use of the technology described in 353 this document or the extent to which any license under such rights 354 might or might not be available; nor does it represent that it has 355 made any independent effort to identify any such rights. Information 356 on the procedures with respect to rights in RFC documents can be 357 found in BCP 78 and BCP 79. 359 Copies of IPR disclosures made to the IETF Secretariat and any assur- 360 ances of licenses to be made available, or the result of an attempt 361 made to obtain a general license or permission for the use of such 362 proprietary rights by implementers or users of this specification can 363 be obtained from the IETF on-line IPR repository at 364 http://www.ietf.org/ipr. 366 The IETF invites any interested party to bring to its attention any 367 copyrights, patents or patent applications, or other proprietary 368 rights that may cover technology that may be required to implement 369 this standard. Please address the information to the IETF at ietf- 370 ipr@ietf.org. 372 11. Full Copyright Statement 374 Copyright (C) The Internet Society (2006). This document is subject 375 to the rights, licenses and restrictions contained in BCP 78, and 376 except as set forth therein, the authors retain all their rights. 378 This document and the information contained herein are provided on an 379 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 380 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 381 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 382 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFOR- 383 MATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES 384 OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.