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Bryant, Ed. 4 Intended status: Standards Track Cisco Systems 5 Expires: August 28, 2010 M. Bocci, Ed. 6 Alcatel-Lucent 7 February 24, 2010 9 MPLS Transport Profile Data Plane Architecture 10 draft-ietf-mpls-tp-data-plane-00 12 Abstract 14 The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP) 15 is the set of MPLS protocol functions applicable to the construction 16 and operation of packet-switched transport networks. This document 17 specifies the subset of these functions that comprises the MPLS-TP 18 data plane: the architectural layer concerned with the encapsulation 19 and forwarding of packets within an MPLS-TP network. 21 This document is a product of a joint Internet Engineering Task Force 22 (IETF) / International Telecommunication Union Telecommunication 23 Standardization Sector (ITU-T) effort to include an MPLS Transport 24 Profile within the IETF MPLS and PWE3 architectures to support the 25 capabilities and functionalities of a packet transport network. 27 Requirements Language 29 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 30 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 31 document are to be interpreted as described in RFC 2119 [RFC2119]. 33 Status of this Memo 35 This Internet-Draft is submitted to IETF in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF), its areas, and its working groups. Note that 40 other groups may also distribute working documents as Internet- 41 Drafts. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 The list of current Internet-Drafts can be accessed at 49 http://www.ietf.org/ietf/1id-abstracts.txt. 51 The list of Internet-Draft Shadow Directories can be accessed at 52 http://www.ietf.org/shadow.html. 54 This Internet-Draft will expire on August 28, 2010. 56 Copyright Notice 58 Copyright (c) 2010 IETF Trust and the persons identified as the 59 document authors. All rights reserved. 61 This document is subject to BCP 78 and the IETF Trust's Legal 62 Provisions Relating to IETF Documents 63 (http://trustee.ietf.org/license-info) in effect on the date of 64 publication of this document. Please review these documents 65 carefully, as they describe your rights and restrictions with respect 66 to this document. Code Components extracted from this document must 67 include Simplified BSD License text as described in Section 4.e of 68 the Trust Legal Provisions and are provided without warranty as 69 described in the BSD License. 71 Table of Contents 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 74 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 75 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 76 2. MPLS-TP Packet Encapsulation and Forwarding . . . . . . . . . 5 77 3. MPLS-TP Transport Entities . . . . . . . . . . . . . . . . . . 5 78 3.1. Label Switched Paths . . . . . . . . . . . . . . . . . . . 5 79 3.1.1. LSP Packet Encapsulation and Forwarding . . . . . . . 5 80 3.1.2. LSP Payloads . . . . . . . . . . . . . . . . . . . . . 6 81 3.1.3. LSP Types . . . . . . . . . . . . . . . . . . . . . . 6 82 3.2. Sections . . . . . . . . . . . . . . . . . . . . . . . . . 7 83 3.3. Pseudowires . . . . . . . . . . . . . . . . . . . . . . . 8 84 4. MPLS-TP Generic Associated Channel . . . . . . . . . . . . . . 8 85 5. Media-Specific Considerations . . . . . . . . . . . . . . . . 8 86 5.1. Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . 8 87 5.1.1. Destination MAC Address Determination . . . . . . . . 8 88 5.2. Other Media . . . . . . . . . . . . . . . . . . . . . . . 9 89 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 90 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 91 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 92 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 93 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 96 1. Introduction 98 The MPLS Transport Profile (MPLS-TP) [I-D.ietf-mpls-tp-framework] is 99 the set of protocol functions that meet the requirements [RFC5654] 100 for the application of MPLS to the construction and operation of 101 packet-switched transport networks. Packet transport networks are 102 defined and described in [I-D.ietf-mpls-tp-framework]. 104 This document specifies the subset of protocol functions that 105 comprises the MPLS-TP data plane: the architectural layer concerned 106 with the encapsulation and forwarding of packets within an MPLS-TP 107 network. 109 This document is a product of a joint Internet Engineering Task Force 110 (IETF) / International Telecommunication Union Telecommunication 111 Standardization Sector (ITU-T) effort to include an MPLS Transport 112 Profile within the IETF MPLS and PWE3 architectures to support the 113 capabilities and functionalities of a packet transport network. 115 1.1. Scope 117 This document has the following purposes: 119 o To identify the data-plane functions within the MPLS Transport 120 Profile 122 o To indicate which of these data-plane functions an MPLS-TP 123 implementation is required to support 125 Note that the MPLS-TP functions discussed in this document are 126 considered OPTIONAL unless stated otherwise. 128 1.2. Terminology 130 Term Definition 131 ------- ------------------------------------------ 132 G-ACh Generic Associated Channel 133 GAL G-ACh Label 134 LER Label Edge Router 135 LSP Label Switched Path 136 LSR Label Switching Router 137 MAC Media Access Control 138 MPLS-TP MPLS Transport Profile 139 OAM Operations, Administration and Maintenance 140 PW Pseudowire 141 QoS Quality of Service 143 Additional definitions and terminology can be found in 145 [I-D.ietf-mpls-tp-framework] and [RFC5654]. 147 2. MPLS-TP Packet Encapsulation and Forwarding 149 This document defines the encapsulation and forwarding functions 150 applicable to packets traversing an MPLS-TP Label Switched Path 151 (LSP), Pseudowire (PW), or Section (see Section 3 for the definitions 152 of these transport entities). Encapsulation and forwarding functions 153 for packets outside an MPLS-TP LSP, PW, or Section, and mechanisms 154 for delivering packets to or from MPLS-TP LSPs, PWs, and Sections, 155 are outside the scope of this document. 157 3. MPLS-TP Transport Entities 159 The MPLS Transport Profile includes the following data-plane 160 transport entities: 162 o Label Switched Paths (LSPs) 164 o Sections 166 o Pseudowires (PWs) 168 3.1. Label Switched Paths 170 MPLS-TP LSPs are ordinary MPLS LSPs as defined in [RFC3031] except as 171 specifically noted otherwise in this document. 173 3.1.1. LSP Packet Encapsulation and Forwarding 175 Encapsulation and forwarding of packets traversing MPLS-TP LSPs MUST 176 follow standard MPLS packet encapsulation and forwarding as defined 177 in [RFC3031] and [RFC3032], except as explicitly stated otherwise in 178 this document. 180 Data-plane support for Internet Protocol (IP) packet encapsulation, 181 addressing, and forwarding is OPTIONAL. 183 Data-plane Quality of Service capabilities are included in the 184 MPLS-TP in the form of the MPLS Differentiated Services (DiffServ) 185 architecture [RFC3270]. Both E-LSP and L-LSP MPLS DiffServ modes are 186 included. The Traffic Class field (formerly the EXP field) of an 187 MPLS label follows the definition of [RFC5462] and [RFC3270] and MUST 188 be processed according to the rules specified in those documents. 190 The Pipe and Short Pipe DiffServ tunneling and TTL processing models 191 described in [RFC3270] and [RFC3443] are included in the MPLS-TP. 192 The Uniform model is outside the scope of the MPLS-TP. 194 Per-platform, per-interface or other context-specific label space 195 [RFC5331] MAY be used for MPLS-TP LSPs. Note that the requirements 196 of a particular LSP type may dictate which label spaces it can use. 198 Per-packet Equal-Cost Multi-Path (ECMP) load-balancing is outside the 199 scope of the MPLS-TP. 201 Penultimate Hop Popping (PHP) MUST be disabled by default on MPLS-TP 202 LSPs. 204 Fragmentation procedures as specified in [RFC3032] are outside the 205 scope of the MPLS-TP. 207 3.1.2. LSP Payloads 209 The MPLS-TP includes support for the following LSP payload types: 211 o Network-layer protocol packets 213 o Pseudowire packets 215 The rules for processing LSP payloads that are network-layer protocol 216 packets SHALL be as specified in [RFC3032] except as specifically 217 noted otherwise in this document. 219 The rules for processing LSP payloads that are pseudowire packets 220 SHALL be as specified in [RFC3985] and the attendant standards 221 defined by the IETF Pseudowire Emulation Edge-to-Edge (PWE3) Working 222 Group. 224 Note that the payload of an MPLS-TP LSP may be a packet type that 225 itself contains one or more MPLS labels. This is true, for instance, 226 when the payload is a pseudowire or another MPLS-TP LSP. From the 227 data-plane perspective, however, an MPLS-TP packet is an MPLS packet 228 as specified in [RFC3032], and so in particular has precisely one 229 label stack, and one label in the stack with its S (Bottom of Stack) 230 bit set to 1. 232 3.1.3. LSP Types 234 The MPLS-TP includes the following LSP types: 236 o Point-to-point unidirectional 237 o Point-to-point associated bidirectional 239 o Point-to-point co-routed bidirectional 241 o Point-to-multipoint unidirectional 243 Point-to-point unidirectional LSPs are supported by the basic MPLS 244 architecture [RFC3031] and are REQUIRED to function in the same 245 manner in the MPLS-TP data plane except as explicitly stated 246 otherwise in this document. 248 A point-to-point associated bidirectional LSP between LSRs A and B 249 consists of two unidirectional point-to-point LSPs, one from A to B 250 and the other from B to A, which are regarded as a pair providing a 251 single logical bidirectional transport path. The nodes A and B are 252 REQUIRED to be aware of this pairing relationship, but other nodes 253 need not be. 255 A point-to-point co-routed bidirectional LSP is a point-to-point 256 associated bidirectional LSP with the additional constraint that its 257 two unidirectional component LSPs follow the same path in the 258 network. This means that if one of the component LSPs follows the 259 path through the nodes N0, ..., Nk, originating on N0 and terminating 260 on Nk, then the path of the other component LSP is Nk, ..., N0, and 261 that at each node an ingress interface of one component LSP is an 262 egress interface of the other. In addition, each node along the path 263 is REQUIRED to be aware of the pairing relationship between the 264 component LSPs. 266 A point-to-multipoint unidirectional LSP functions in the same manner 267 in the data plane, with respect to basic label processing and packet- 268 switching operations, as a point-to-point unidirectional LSP, with 269 one difference: an LSR may have more than one (egress interface, 270 outgoing label) pair associated with the LSP, and any packet it 271 transmits on the LSP is transmitted out all associated egress 272 interfaces. Point-to-multipoint LSPs are described in [RFC4875] and 273 [RFC5332]. 275 3.2. Sections 277 Two MPLS-TP LSRs are considered to be topologically adjacent at a 278 particular layer n >= 0 of the MPLS-TP LSP hierarchy if there exists 279 a link between them at the next lowest network layer. Such a link, 280 if it exists, will be either an MPLS-TP LSP (if n > 0) or a data-link 281 provided by the underlying server layer network (if n = 0), and is 282 referred to as an MPLS-TP Section at layer n of the MPLS-TP LSP 283 hierarchy. Thus, the links traversed by a layer n+1 MPLS-TP LSP are 284 layer n MPLS-TP sections. 286 Note that the MPLS label stack associated with an MPLS-TP section at 287 layer n consists of n labels, in the absence of stack optimisation 288 mechanisms such as PHP. Note also that in order for two LSRs to 289 exchange MPLS-TP control packets over a section, an additional label, 290 the Generic Associated Channel Label (GAL) (see Section 4) must 291 appear at the bottom of the label stack. 293 3.3. Pseudowires 295 The data-plane architectures for Single-Segment Pseudowires 296 [RFC3985], Multisegment Pseudowires [RFC5659] and Point-to-Multipoint 297 Pseudowires [I-D.ietf-pwe3-p2mp-pw-requirements], and the associated 298 data-plane pseudowire protocol functions, as defined by the IETF 299 Pseudowire Emulation Edge-to-Edge (PWE3) Working Group, are included 300 in the MPLS-TP. 302 This document specifies no modifications or extensions to pseudowire 303 data-plane architectures or protocols. 305 4. MPLS-TP Generic Associated Channel 307 The MPLS Generic Associated Channel (G-ACh) mechanism is specified in 308 [RFC5586] and included in the MPLS-TP. The G-ACh provides an 309 auxiliary logical data channel associated with MPLS-TP Sections, 310 LSPs, and PWs in the data plane. The primary purpose of the G-ACh in 311 the context of MPLS-TP is to support control, management, and OAM 312 traffic associated with MPLS-TP transport entities. The G-ACh MUST 313 NOT be used to transport client layer network traffic in MPLS-TP 314 networks. 316 5. Media-Specific Considerations 318 This section discusses considerations for support of the MPLS-TP data 319 plane by specific underlying server layer media. 321 5.1. Ethernet 323 5.1.1. Destination MAC Address Determination 325 When two MPLS-TP nodes are connected by a point-to-point Ethernet 326 link, the question arises as to what destination Ethernet Media 327 Access Control (MAC) address should be specified in Ethernet frames 328 transmitted to the peer node over the link. The problem of 329 determining this address does not arise in IP/MPLS networks because 330 of the presence of the Ethernet Address Resolution Protocol (ARP) 331 [RFC0826] or IP version 6 Neighbor Discovery protocol [RFC4861], 332 which allow the unicast MAC address of the peer device to be learned 333 dynamically. 335 If existing mechanisms are available in an MPLS-TP network to 336 determine the destination unicast MAC addresses of peer nodes - for 337 example if the network also happens to be an IP/MPLS network - such 338 mechanisms SHOULD be used. The remainder of this section discusses 339 the available options when this is not the case. 341 One possibility is for each node to be statically configured with the 342 MAC address of its peer. Static MAC address configuration MAY be 343 used in an MPLS-TP network, but can present an administrative burden 344 and lead to operational problems. 346 Another possibility is to use the Ethernet broadcast address, but 347 this may lead to excessive frame distribution and processing at the 348 Ethernet layer. Broadcast traffic may also be treated specially by 349 some devices and this may not be desirable for MPLS-TP data frames. 351 The preferred approach is therefore to use as the destination MAC 352 address an Ethernet multicast address reserved for MPLS-TP. The 353 address allocated for this purpose by the Internet Assigned Numbers 354 Authority (IANA) is 01-00-5E-XX-XX-XX. An MPLS-TP implementation 355 MUST process Ethernet frames received with this destination MAC 356 address by default. 358 [Editor's note: Decide what to say about multipoint Ethernet and 359 switched links. Decide if there is a need for protocol mechanisms to 360 support learning of the Ethernet unicast MAC addresses of MPLS-TP 361 peers that are not also IP peers.] 363 5.2. Other Media 365 [Editor's note: Decide whether any considerations for media other 366 than Ethernet need to be mentioned.] 368 6. Security Considerations 370 TBD 372 7. IANA Considerations 374 A future version of this document will detail IANA considerations for 375 the allocation of a standard Ethernet multicast MAC address for use 376 in MPLS-TP networks. 378 8. References 380 8.1. Normative References 382 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 383 Requirement Levels", BCP 14, RFC 2119, March 1997. 385 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 386 Label Switching Architecture", RFC 3031, January 2001. 388 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 389 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 390 Encoding", RFC 3032, January 2001. 392 [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., 393 and S. Ueno, "Requirements of an MPLS Transport Profile", 394 RFC 5654, September 2009. 396 [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic 397 Associated Channel", RFC 5586, June 2009. 399 [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, 400 P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi- 401 Protocol Label Switching (MPLS) Support of Differentiated 402 Services", RFC 3270, May 2002. 404 [RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing 405 in Multi-Protocol Label Switching (MPLS) Networks", 406 RFC 3443, January 2003. 408 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 409 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 410 Class" Field", RFC 5462, February 2009. 412 [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream 413 Label Assignment and Context-Specific Label Space", 414 RFC 5331, August 2008. 416 [RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, 417 "Extensions to Resource Reservation Protocol - Traffic 418 Engineering (RSVP-TE) for Point-to-Multipoint TE Label 419 Switched Paths (LSPs)", RFC 4875, May 2007. 421 [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS 422 Multicast Encapsulations", RFC 5332, August 2008. 424 8.2. Informative References 426 [I-D.ietf-mpls-tp-framework] 427 Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. 428 Berger, "A Framework for MPLS in Transport Networks", 429 draft-ietf-mpls-tp-framework-10 (work in progress), 430 February 2010. 432 [I-D.ietf-pwe3-p2mp-pw-requirements] 433 Heron, G., Wang, L., Aggarwal, R., Vigoureux, M., Bocci, 434 M., Jin, L., JOUNAY, F., Niger, P., Kamite, Y., DeLord, 435 S., and L. Martini, "Requirements for Point-to-Multipoint 436 Pseudowire", draft-ietf-pwe3-p2mp-pw-requirements-02 (work 437 in progress), January 2010. 439 [RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to- 440 Edge (PWE3) Architecture", RFC 3985, March 2005. 442 [RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi- 443 Segment Pseudowire Emulation Edge-to-Edge", RFC 5659, 444 October 2009. 446 [RFC0826] Plummer, D., "Ethernet Address Resolution Protocol: Or 447 converting network protocol addresses to 48.bit Ethernet 448 address for transmission on Ethernet hardware", STD 37, 449 RFC 826, November 1982. 451 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 452 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 453 September 2007. 455 Authors' Addresses 457 Dan Frost (editor) 458 Cisco Systems 460 Email: danfrost@cisco.com 462 Stewart Bryant (editor) 463 Cisco Systems 465 Email: stbryant@cisco.com 466 Matthew Bocci (editor) 467 Alcatel-Lucent 469 Email: matthew.bocci@alcatel-lucent.com