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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) ** Obsolete normative reference: RFC 4447 (ref. '6') (Obsoleted by RFC 8077) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group M. Bocci 3 Internet-Draft Alcatel-Lucent 4 Intended status: Standards Track G. Swallow 5 Expires: January 22, 2012 Cisco 6 E. Gray 7 Ericsson 8 July 21, 2011 10 MPLS-TP Identifiers 11 draft-ietf-mpls-tp-identifiers-07 13 Abstract 15 This document specifies an initial set of identifiers to be used in 16 the Transport Profile of Multiprotocol Label Switching (MPLS-TP). 17 The MPLS-TP requirements (RFC 5654) require that the elements and 18 objects in an MPLS-TP environment are able to be configured and 19 managed without a control plane. In such an environment many 20 conventions for defining identifiers are possible. This document 21 defines identifiers for MPLS-TP management and OAM functions 22 compatible with IP/MPLS conventions. 24 This document is a product of a joint Internet Engineering Task Force 25 (IETF) / International Telecommunication Union Telecommunication 26 Standardization Sector (ITU-T) effort to include an MPLS Transport 27 Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge 28 (PWE3) architectures to support the capabilities and functionalities 29 of a packet transport network as defined by the ITU-T. 31 Status of this Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on January 22, 2012. 48 Copyright Notice 49 Copyright (c) 2011 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 67 1.3. Notational Conventions . . . . . . . . . . . . . . . . . . 4 68 2. Named Entities . . . . . . . . . . . . . . . . . . . . . . . . 5 69 3. Uniquely Identifying an Operator - the Global_ID . . . . . . . 5 70 4. Node and Interface Identifiers . . . . . . . . . . . . . . . . 6 71 5. MPLS-TP Tunnel and LSP Identifiers . . . . . . . . . . . . . . 7 72 5.1. MPLS-TP Point to Point Tunnel Identifiers . . . . . . . . 8 73 5.2. MPLS-TP LSP Identifiers . . . . . . . . . . . . . . . . . 8 74 5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers . . . 9 75 5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers . . . 9 76 5.3. Mapping to RSVP Signaling . . . . . . . . . . . . . . . . 10 77 6. Pseudowire Path Identifiers . . . . . . . . . . . . . . . . . 11 78 7. Maintenance Identifiers . . . . . . . . . . . . . . . . . . . 12 79 7.1. Maintenance Entity Group Identifiers . . . . . . . . . . . 13 80 7.1.1. MPLS-TP Section MEG_IDs . . . . . . . . . . . . . . . 13 81 7.1.2. MPLS-TP LSP MEG_IDs . . . . . . . . . . . . . . . . . 13 82 7.1.3. Pseudowire MEG_IDs . . . . . . . . . . . . . . . . . . 13 83 7.2. Maintenance Entity Group End Point Identifiers . . . . . . 14 84 7.2.1. MPLS-TP Section MEP_IDs . . . . . . . . . . . . . . . 14 85 7.2.2. MPLS-TP LSP_MEP_ID . . . . . . . . . . . . . . . . . . 14 86 7.2.3. MEP_IDs for Pseudowires . . . . . . . . . . . . . . . 15 87 7.3. Maintenance Entity Group Intermediate Point Identifiers . 15 88 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 89 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 90 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 91 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16 92 10.2. Informative References . . . . . . . . . . . . . . . . . . 16 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 95 1. Introduction 97 This document specifies an initial set of identifiers to be used in 98 the Transport Profile of Multiprotocol Label Switching (MPLS-TP). 99 The MPLS-TP requirements (RFC 5654) [7] require that the elements and 100 objects in an MPLS-TP environment are able to be configured and 101 managed without a control plane. In such an environment many 102 conventions for defining identifiers are possible. This document 103 defines identifiers for MPLS-TP management and OAM functions 104 compatible with IP/MPLS conventions. That is, the identifiers have 105 been chosen to be compatible with existing IP, MPLS, GMPLS, and 106 Pseudowire definitions. 108 This document is a product of a joint Internet Engineering Task Force 109 (IETF) / International Telecommunication Union Telecommunication 110 Standardization Sector (ITU-T) effort to include an MPLS Transport 111 Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge 112 (PWE3) architectures to support the capabilities and functionalities 113 of a packet transport network as defined by the ITU-T. 115 1.1. Terminology 117 AII: Attachment Interface Identifier 119 ASN: Autonomous System Number 121 EGP: Exterior Gateway Protocol 123 FEC: Forwarding Equivalence Class 125 GMPLS: Generalized Multi-Protocol Label Switching 127 IGP: Interior Gateway Protocol 129 LSP: Label Switched Path 131 LSR: Label Switching Router 133 MEG: Maintenance Entity Group 135 MEP: Maintenance Entity Group End Point 137 MIP: Maintenance Entity Group Intermediate Point 139 MPLS: Multi-Protocol Label Switching 141 NNI: Network-to-Network Interface 142 OAM: Operations, Administration and Maintenance 144 P2P: Point to Point 146 PW: Pseudowire 148 RSVP: Resource Reservation Protocol 150 RSVP-TE: RSVP Traffic Engineering 152 SPME: Sub Path Maintenance Entities 154 S-PE: Switching Provider Edge 156 T-PE: Terminating Provider Edge 158 1.2. Requirements Language 160 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 161 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 162 document are to be interpreted as described in RFC 2119 [1]. 164 1.3. Notational Conventions 166 All multiple-word atomic identifiers use underscores (_) between the 167 words to join the words. Many of the identifiers are composed of a 168 set of other identifiers. These are expressed by listing the latter 169 identifiers joined with double-colon, "::", notation. 171 Where the same identifier type is used multiple times in a 172 concatenation, they are qualified by a prefix joined to the 173 identifier by a dash (-). For example A1-Node_ID is the Node_ID of a 174 node referred to as A1. 176 The notation defines a preferred ordering of the fields. 177 Specifically the designation A1 is used to indicate the lower sort 178 order of a field or set of fields and Z9 is used to indicate the 179 higher sort order of the same. The sort is either alphanumeric or 180 numeric depending on the field's definition. Where the sort applies 181 to a group of fields, those fields are grouped with {...}. 183 Note, however, that the uniqueness of an identifier does not depend 184 on the ordering, but rather, upon the uniqueness and scoping of the 185 fields that compose the identifier. Further the preferred ordering 186 is not intended to constrain protocol designs by dictating a 187 particular field sequence (for example see Section 5.2.1) or even 188 what fields appear in which objects (for example see Section 5.3). 190 2. Named Entities 192 In order to configure, operate and manage a transport network based 193 on the MPLS Transport Profile, a number of entities require 194 identification. Identifiers for the following entities are defined 195 in this document: 197 * Global_ID 199 * Node 201 * Interface 203 * Tunnel 205 * LSP 207 * PW 209 * MEG 211 * MEP 213 * MIP 215 Note that we have borrowed the term tunnel from RSVP-TE (RFC 3209) 216 [2] where it is used to describe an entity that provides a logical 217 association between a source and destination LSR. The tunnel in turn 218 is instantiated by one or more LSPs, where the additional LSPs are 219 used for protection or re-grooming of the tunnel. 221 3. Uniquely Identifying an Operator - the Global_ID 223 The Global_ID is defined to uniquely identify an operator. RFC 5003 224 [3] defines a globally unique Attachment Interface Identifier (AII). 225 That AII is composed of three parts, a Global_ID which uniquely 226 identifies an operator, a prefix, and finally, an attachment circuit 227 identifier. We have chosen to use that Global ID for MPLS-TP. 228 Quoting from RFC 5003, section 3.2, "The global ID can contain the 229 2-octet or 4-octet value of the operator's Autonomous System Number 230 (ASN). It is expected that the global ID will be derived from the 231 globally unique ASN of the autonomous system hosting the PEs 232 containing the actual AIIs. The presence of a global ID based on the 233 operator's ASN ensures that the AII will be globally unique." 235 A Global_ID is an unsigned 32-bit value and MUST be derived from a 236 4-octet AS number assigned to the operator. Note that 2-octet AS 237 numbers have been incorporated in the 4-octet by placing the 2-octet 238 AS number, in the low-order octets and setting the two high-order 239 octets to zero. 241 ASN 0 is reserved and cannot be assigned to an operator. An 242 identifier containing a Global_ID of zero means that no Global_ID is 243 specified. Note that a Global_ID of zero is limited to entities 244 contained within a single operator and MUST NOT be used across an 245 NNI. 247 The Global_ID is used solely to provide a globally unique context for 248 other MPLS-TP identifiers. While the AS Number used in the Global_ID 249 MUST be one which the operator is entitled to use, the use of the 250 Global_ID is not related to the use of the ASN in protocols such as 251 BGP. 253 4. Node and Interface Identifiers 255 An LSR requires identification of the node itself and of its 256 interfaces. An interface is the attachment point to a server 257 (sub-)layer, e.g., MPLS-TP section or MPLS-TP tunnel. 259 We call the identifier associated with a node a Node Identifier 260 (Node_ID). The Node_ID is a unique 32-bit value assigned by the 261 operator within the scope of a Global_ID. The structure of the 262 Node_ID is operator specific and is outside the scope of this 263 document. However, the value zero is reserved and MUST NOT be used. 264 Where IPv4 addresses are used, it may be convenient to use the Node's 265 IPv4 loopback address as the Node_ID, however the Node_ID does not 266 need to have any association with the IPv4 address space used in the 267 operator's IGP or EGP. Where IPv6 addresses are used exclusively, a 268 32-bit value unique within the scope of a Global_ID is assigned. 270 An LSR can support multiple layers (e.g. hierarchical LSPs) and the 271 Node_ID belongs to the multiple layer context i.e. it is applicable 272 to all LSPs or PWs that originate on, have a intermediate point on, 273 or terminate on the node. 275 In situations where a Node_ID needs to be globally unique, this is 276 accomplished by prefixing the identifier with the operator's 277 Global_ID. 279 The term interface is used for the attachment point to an MPLS-TP 280 section. Within the context of a particular node, we call the 281 identifier associated with an interface an Interface Number (IF_Num). 282 The IF_Num is a 32-bit unsigned integer assigned by the operator and 283 MUST be unique within the scope of a Node_ID. The IF_Num value 0 has 284 special meaning (see Section 7.3, MIP Identifiers) and MUST NOT be 285 used to identify an MPLS-TP interface. 287 Note that IF_Num has no relation with the ifNum object defined in RFC 288 2863 [8]. Further, no mapping is mandated between IF_Num and ifIndex 289 in RFC 2863. 291 An Interface Identifier (IF_ID) identifies an interface uniquely 292 within the context of a Global_ID. It is formed by concatenating the 293 Node_ID with the IF_Num. That is, an IF_ID is a 64-bit identifier 294 formed as Node_ID::IF_Num. 296 This convention was chosen to allow compatibility with GMPLS. The 297 GMPLS signaling functional description [4] requires interface 298 identification. GMPLS allows three formats for the Interface_ID. 299 The third format consists of an IPv4 Address plus a 32-bit unsigned 300 integer for the specific interface. The format defined for MPLS-TP 301 is consistent with this format, but uses the Node_ID instead of an 302 IPv4 Address. 304 If an IF_ID needs to be globally unique, this is accomplished by 305 prefixing the identifier with the operator's Global_ID. 307 Note that MPLS-TP supports hierarchical sections. The attachment 308 point to a MPLS-TP Section at any (sub-)layer requires a node-unique 309 IF_Num. 311 5. MPLS-TP Tunnel and LSP Identifiers 313 In MPLS the actual transport of packets is provided by label switched 314 paths (LSPs). A transport service may be composed of multiple LSPs. 315 Further the LSPs providing a service may change over time due to 316 protection and restoration events. In order to clearly identify the 317 service we use the term "MPLS-TP Tunnel" or simply "tunnel" for a 318 service provided by (for example) a working LSP and protected by a 319 protection LSP. The Tunnel Identifier (Tunnel_ID) identifies the 320 transport service and provides a stable binding to the client in the 321 face of changes in the data plane LSPs used to provide the service 322 due to protection or restoration events. This section defines an 323 MPLS-TP Tunnel_ID to uniquely identify a tunnel, and an MPLS-TP LSP 324 Identifier (LSP_ID) to uniquely identify an LSP associated with a 325 tunnel. 327 For the case where multiple LSPs (for example) are used to support a 328 single service with a common set of end-points, using the Tunnel_ID 329 allows for a trivial mapping between the server and client layers, 330 providing a common service identifier which may be either defined by, 331 or used by, the client. 333 Note that this usage is not intended to constrain protection schemes, 334 and may be used to identify any service (protected or unprotected) 335 that may appear to the client as a single service attachment point. 336 Keeping the Tunnel_ID consistent across working and protection LSPs 337 is a useful construct currently employed within GMPLS. However, the 338 Tunnel_ID for a protection LSP MAY differ from that used by its 339 corresponding working LSP. 341 5.1. MPLS-TP Point to Point Tunnel Identifiers 343 At each endpoint a tunnel is uniquely identified by the endpoint's 344 Node_ID and a locally assigned tunnel number. Specifically a Tunnel 345 Number (Tunnel_Num) is a 16-bit unsigned integer unique within the 346 context of the Node_ID. The motivation for each endpoint having its 347 own tunnel number is to allow a compact form for the MEP_ID. See 348 Section 7.2.2. 350 Having two tunnel numbers also serves to simplify other signaling 351 (e.g., setup of associated bidirectional tunnels as described in 352 Section 5.3). 354 The concatenation of the two endpoint identifiers serves as the full 355 identifier. Using the A1/Z9 convention the format of a Tunnel_ID is: 357 A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num} 359 Where the Tunnel_ID needs to be globally unique, this is accomplished 360 by using globally unique Node_IDs as defined above. Thus a globally 361 unique Tunnel_ID becomes: 363 A1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_ID::Node_ID:: 364 Tunnel_Num} 366 When an MPLS-TP Tunnel is configured, it MUST be assigned a unique 367 IF_ID at each endpoint. As usual, the IF_ID is composed of the local 368 Node_ID concatenated with a 32-bit IF_Num. 370 5.2. MPLS-TP LSP Identifiers 372 This section defines identifiers for MPLS-TP co-routed bidirectional 373 and associated bidirectional LSPs. Note that MPLS-TP Sub Path 374 Maintenance Entities (SPMEs) as defined in RFC 5921 [9] are also LSPs 375 and use these same forms of identifiers. 377 5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers 379 A co-routed bidirectional LSP can be uniquely identified by a single 380 LSP number within the scope of an MPLS-TP Tunnel_ID. Specifically an 381 LSP Number (LSP_Num) is a 16-bit unsigned integer unique within the 382 Tunnel_ID. Thus the format of an MPLS-TP co-routed bidirectional 383 LSP_ID is: 385 A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num}::LSP_Num 387 Note that the uniqueness of identifiers does not depend on the A1/Z9 388 sort ordering. Thus the identifier 390 Z9-{Node_ID::Tunnel_Num}::A1-{Node_ID::Tunnel_Num}::LSP_Num 392 is synonymous with the one above. 394 At the dataplane level, a co-routed bidirectional LSP is composed of 395 two unidirectional LSPs traversing the same links in opposite 396 directions. Since a co-routed bidirectional LSP is provisioned or 397 signaled as a single entity, a single LSP_Num is used for both 398 unidirectional LSPs. The unidirectional LSPs can be referenced by 399 the identifiers: 401 A1-Node_ID::A1-Tunnel_Num::LSP_Num::Z9-Node_ID and 403 Z9-Node_ID::Z9-Tunnel_Num::LSP_Num::A1-Node_ID respectively. 405 Where the LSP_ID needs to be globally unique, this is accomplished by 406 using globally unique Node_IDs as defined above. Thus a globally 407 unique LSP_ID becomes: 409 A1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_ID:: 410 Node_ID::Tunnel_Num}::LSP_Num 412 5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers 414 For an associated bidirectional LSP each of the unidirectional LSPs 415 from A1 to Z9 and Z9 to A1 require LSP_Nums. Each unidirectional LSP 416 is uniquely identified by a single LSP number within the scope of the 417 ingress's Tunnel_Num. Specifically an LSP Number (LSP_Num) is a 16- 418 bit unsigned integer unique within the scope of the ingress's 419 Tunnel_Num. Thus the format of an MPLS-TP associated bidirectional 420 LSP_ID is: 422 A1-{Node_ID::Tunnel_Num::LSP_Num}:: 424 Z9-{Node_ID::Tunnel_Num::LSP_Num} 426 At the dataplane level, an associated bidirectional LSP is composed 427 of two unidirectional LSPs between two nodes in opposite directions. 428 The unidirectional LSPs may be referenced by the identifiers: 430 A1-Node_ID::A1-Tunnel_Num::A1-LSP_Num::Z9-Node_ID and 432 Z9-Node_ID::Z9-Tunnel_Num::Z9-LSP_Num::A1-Node_ID respectively. 434 Where the LSP_ID needs to be globally unique, this is accomplished by 435 using globally unique Node_IDs as defined above. Thus a globally 436 unique LSP_ID becomes: 438 A1-{Global_ID::Node_ID::Tunnel_Num::LSP_Num}:: 439 Z9-{Global_ID::Node_ID::Tunnel_Num::LSP_Num} 441 5.3. Mapping to RSVP Signaling 443 This section is informative and exists to help understand the 444 structure of the LSP IDs. 446 GMPLS [5] is based on RSVP-TE [2]. This section defines the mapping 447 from an MPLS-TP LSP_ID to RSVP-TE. At this time, RSVP-TE has yet to 448 be extended to accommodate Global_IDs. Thus a mapping is only made 449 for the network unique form of the LSP_ID and assumes that the 450 operator has chosen to derive its Node_IDs from valid IPv4 addresses. 452 GMPLS and RSVP-TE signaling use a 5-tuple to uniquely identify an LSP 453 within a operator's network. This tuple is composed of a Tunnel 454 Endpoint Address, Tunnel_ID, Extended Tunnel ID, and Tunnel Sender 455 Address and (RSVP) LSP_ID. RFC 3209 allows some flexibility in how 456 the Extended Tunnel ID is chosen and a direct mapping is not 457 mandated. One convention that is often used, however, is to populate 458 this field with the same value as the Tunnel Sender Address. The 459 examples below follow that convention. Note that these are only 460 examples. 462 For a co-routed bidirectional LSP signaled from A1 to Z9, the mapping 463 to the GMPLS 5-tuple is as follows: 465 * Tunnel Endpoint Address = Z9-Node_ID 467 * Tunnel_ID = A1-Tunnel_Num 469 * Extended Tunnel_ID = A1-Node_ID 470 * Tunnel Sender Address = A1-Node_ID 472 * (RSVP) LSP_ID = LSP_Num 474 An associated bidirectional LSP between two nodes A1 and Z9 consists 475 of two unidirectional LSPs, one from A1 to Z9 and one from Z9 to A1. 477 In situations where a mapping to the RSVP-TE 5-tuples is required, 478 the following mappings are used. For the A1 to Z9 LSP the mapping 479 would be: 481 * Tunnel Endpoint Address = Z9-Node_ID 483 * Tunnel_ID = A1-Tunnel_Num 485 * Extended Tunnel_ID = A1-Node_ID 487 * Tunnel Sender Address = A1-Node_ID 489 * (RSVP) LSP_ID = A1-LSP_Num 491 Likewise, the Z9 to A1 LSP, the mapping would be: 493 * Tunnel Endpoint Address = A1-Node_ID 495 * Tunnel_ID = Z9-Tunnel_Num 497 * Extended Tunnel_ID = Z9-Node_ID 499 * Tunnel Sender Address = Z9-Node_ID 501 * (RSVP) LSP_ID = Z9-LSP_Num 503 6. Pseudowire Path Identifiers 505 Pseudowire signaling (RFC 4447 [6]) defines two FECs used to signal 506 pseudowires. Of these, FEC Type 129 along with AII Type 2 as defined 507 in RFC 5003 [3] fits the identification requirements of MPLS-TP. 509 In an MPLS-TP environment, a PW is identified by a set of identifiers 510 which can be mapped directly to the elements required by FEC 129 and 511 AII Type 2. To distinguish this identifier from other Pseudowire 512 Identifiers, we call this a Pseudowire Path Identifier (PW_Path_ID). 514 The AII Type 2 is composed of three fields. These are the Global_ID, 515 the Prefix, and the AC_ID. The Global_ID used in this document is 516 identical to the Global_ID defined in RFC 5003. The Node_ID is used 517 as the Prefix. The AC_ID is as defined in RFC 5003. 519 To complete the FEC 129, all that is required is an Attachment Group 520 Identifier (AGI). That field is exactly as specified in RFC 4447. A 521 (bidirectional) pseudowire consists of a pair of unidirectional LSPs, 522 one in each direction. Thus for signaling, FEC 129 has a notion of 523 Source AII (SAII) and Target AII (TAII). These terms are used 524 relative to the direction of the LSP. 526 In a purely configured environment when referring to the entire PW, 527 this distinction is not critical. That is a FEC 129 of AGIa::AIIb:: 528 AIIc is equivalent to AGIa::AIIc::AIIb. 530 We note that in a signaled environment, the required convention in 531 RFC 4447 is that at a particular endpoint, the AII associated with 532 that endpoint comes first. The complete PW_Path_ID is: 534 AGI::A1-{Global_ID::Node_ID::AC_ID}:: 535 Z9-{Global_ID::Node_ID::AC_ID}. 537 In a signaled environment the LSP from A1 to Z9 would be initiated 538 with a label request from A1 to Z9 with the fields of the FEC 129 539 completed as follows: 541 AGI = AGI 542 SAII = A1-{Global_ID::Node_ID::AC_ID} 543 TAII = Z9-{Global_ID::Node_ID::AC_ID} 545 The LSP from Z9 to A1 would signaled with: 547 AGI = AGI 548 SAII = Z9-{Global_ID::Node_ID::AC_ID} 549 TAII = A1-{Global_ID::Node_ID::AC_ID} 551 7. Maintenance Identifiers 553 In MPLS-TP a Maintenance Entity Group (MEG) represents an Entity that 554 requires management and defines a relationship between a set of 555 maintenance points. A maintenance point is either a Maintenance 556 Entity Group End-point (MEP), a Maintenance Entity Group Intermediate 557 Point (MIP), or a Pseudowire Segment Endpoint. Within the context of 558 a MEG, MEPs and MIPs must be uniquely identified. This section 559 defines a means of uniquely identifying Maintenance Entity Groups, 560 Maintenance Entities and uniquely defining MEPs and MIPs within the 561 context of a Maintenance Entity Group. 563 7.1. Maintenance Entity Group Identifiers 565 Maintenance Entity Group Identifiers (MEG_IDs) are required for 566 MPLS-TP sections, LSPs and Pseudowires. The formats were chosen to 567 follow the IP compatible identifiers defined above. 569 7.1.1. MPLS-TP Section MEG_IDs 571 MPLS-TP allows a hierarchy of sections. See "MPLS-TP Data Plane 572 Architecture" (RFC 5960)[10]. Sections above layer 0 are MPLS-TP 573 LSPs. These use their MPLS-TP LSP MEG IDs defined in Section 7.1.2. 575 IP compatible MEG_IDs for MPLS-TP sections at layer 0 are formed by 576 concatenating the two IF_IDs of the corresponding section using the 577 A1/Z9 ordering. For example: 579 A1-IF_ID::Z9-IF_ID 581 Where the Section_MEG_ID needs to be globally unique, this is 582 accomplished by using globally unique Node_IDs as defined above. 583 Thus a globally unique Section_MEG_ID becomes: 585 A1-{Global_ID::IF_ID}::Z9-{Global_ID::IF_ID} 587 7.1.2. MPLS-TP LSP MEG_IDs 589 A MEG pertains to a unique MPLS-TP LSP. IP compatible MEG_IDs for 590 MPLS-TP LSPs are simply the corresponding LSP_IDs, however, the A1/Z9 591 ordering MUST be used. For bidirectional co-routed LSPs the format 592 of the LSP_ID is found in Section 5.2.1. For associated 593 bidirectional LSPs the format is in Section 5.2.2. 595 We note that while the two identifiers are syntactically identical, 596 they have different semantics. This semantic difference needs to be 597 made clear. For instance if both a MPLS-TP LSP_ID and MPLS-TP LSP 598 MEG_IDs are to be encoded in TLVs, different types need to be 599 assigned for these two identifiers. 601 7.1.3. Pseudowire MEG_IDs 603 For Pseudowires a MEG pertains to a single PW. The IP compatible 604 MEG_ID for a PW is simply the corresponding PW_Path_ID, however, the 605 A1/Z9 ordering MUST be used. The PW_Path_ID is described in 606 Section 6. We note that while the two identifiers are syntactically 607 identical, they have different semantics. This semantic difference 608 needs to be made clear. For instance if both a PW_Path_ID and a 609 PW_MEG_ID are to be encoded in TLVs, different types need to be 610 assigned for these two identifiers. 612 7.2. Maintenance Entity Group End Point Identifiers 614 7.2.1. MPLS-TP Section MEP_IDs 616 IP compatible MEP_IDs for MPLS-TP sections above layer 0 are their 617 MPLS-TP LSP_MEP_IDs. See Section 7.2.2. 619 IP compatible MEP_IDs for MPLS-TP sections at layer 0 are simply the 620 IF_IDs of each end of the section. For example, for a section whose 621 MEG_ID is 623 A1-IF_ID::Z9-IF_ID 625 the Section MEP_ID at A1 would be 627 A1-IF_ID 629 and the Section MEP_ID at Z9 would be 631 Z9-IF_ID. 633 Where the Section MEP_ID needs to be globally unique, this is 634 accomplished by using globally unique Node_IDs as defined above. 635 Thus a globally unique Section MEP_ID becomes 637 Global_ID::IF_ID. 639 7.2.2. MPLS-TP LSP_MEP_ID 641 In order to automatically generate MEP_IDs for MPLS-TP LSPs, we use 642 the elements of identification that are unique to an endpoint. This 643 ensures that MEP_IDs are unique for all LSPs within a operator. When 644 Tunnels or LSPs cross operator boundaries, these are made unique by 645 pre-pending them with the operator's Global_ID. 647 The MPLS-TP LSP_MEP_ID is 649 Node_ID::Tunnel_Num::LSP_Num 651 where the Node_ID is the node in which the MEP is located and 652 Tunnel_Num is the tunnel number unique to that node. In the case of 653 co-routed bidirectional LSPs, the single LSP_Num is used at both 654 ends. In the case of associated bidirectional LSPs, the LSP_Num is 655 the one unique to where the MEP resides. 657 In situations where global uniqueness is required this becomes: 659 Global_ID::Node_ID::Tunnel_Num::LSP_Num 661 7.2.3. MEP_IDs for Pseudowires 663 Like MPLS-TP LSPs, Pseudowire endpoints (T-PEs) require MEP_IDs. In 664 order to automatically generate MEP_IDs for PWs, we simply use the 665 AGI plus the AII associated with that end of the PW. Thus a MEP_ID 666 for a Pseudowire T-PE takes the form 668 AGI::Global_ID::Node_ID::AC_ID 670 where the Node_ID is the node in which the MEP is located and the 671 AC_ID is the AC_ID of the Pseudowire at that node. 673 7.3. Maintenance Entity Group Intermediate Point Identifiers 675 For a MIP which is associated with particular interface, we simply 676 use the IF_ID (see Section 4) of the interfaces which are cross- 677 connected. This allows, MIPs to be independently identified in one 678 node where a per-interface MIP model is used. If only a per node MIP 679 model is used then one MIP is configured. In this case the MIP_ID is 680 formed using the Node_ID and an IF_Num of 0. 682 8. IANA Considerations 684 There are no IANA actions resulting from this document. 686 9. Security Considerations 688 This document describes an information model and, as such, does not 689 introduce security concerns. Protocol specifications that describe 690 use of this information model, however, may introduce security risks 691 and concerns about authentication of participants. For this reason, 692 the writers of protocol specifications for the purpose of describing 693 implementation of this information model need to describe security 694 and authentication concerns that may be raised by the particular 695 mechanisms defined and how those concerns may be addressed. 697 Uniqueness of the identifiers from this document is guaranteed by the 698 assigner (e.g., a Global_ID is unique based on the assignment of ASNs 699 from IANA and both a Node_ID and a IF_Num are unique based on the 700 assignment by an operator). Failure by an assigner to use unique 701 values within the specified scoping for any of the identifiers 702 defined herein could result in operational problems. For example and 703 non-unique MEP value could result in failure to detect a mis-merged 704 LSP. 706 Protocol specifications that utilize the identifiers defined herein 707 need to consider the implications of guessable identifiers and, where 708 there is a security implication, SHOULD give advice on how to make 709 identifiers less guessable. 711 10. References 713 10.1. Normative References 715 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 716 Levels", BCP 14, RFC 2119, March 1997. 718 [2] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and 719 G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", 720 RFC 3209, December 2001. 722 [3] Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment 723 Individual Identifier (AII) Types for Aggregation", RFC 5003, 724 September 2007. 726 [4] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) 727 Signaling Functional Description", RFC 3471, January 2003. 729 [5] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) 730 Signaling Resource ReserVation Protocol-Traffic Engineering 731 (RSVP-TE) Extensions", RFC 3473, January 2003. 733 [6] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, 734 "Pseudowire Setup and Maintenance Using the Label Distribution 735 Protocol (LDP)", RFC 4447, April 2006. 737 10.2. Informative References 739 [7] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and 740 S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, 741 September 2009. 743 [8] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", 744 RFC 2863, June 2000. 746 [9] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, "A 747 Framework for MPLS in Transport Networks", RFC 5921, July 2010. 749 [10] Frost, D., Bryant, S., and M. Bocci, "MPLS Transport Profile 750 Data Plane Architecture", RFC 5960, August 2010. 752 Authors' Addresses 754 Matthew Bocci 755 Alcatel-Lucent 756 Voyager Place, Shoppenhangers Road 757 Maidenhead, Berks SL6 2PJ 758 UK 760 Email: matthew.bocci@alcatel-lucent.com 762 George Swallow 763 Cisco 765 Email: swallow@cisco.com 767 Eric Gray 768 Ericsson 769 900 Chelmsford Street 770 Lowell, Massachussetts 01851-8100 772 Email: eric.gray@ericsson.com