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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group K. Kompella 3 Internet-Draft Juniper Networks 4 Obsoletes: 4379, 6829 (if approved) C. Pignataro 5 Intended status: Standards Track N. Kumar 6 Expires: June 20, 2016 Cisco 7 S. Aldrin 8 Google 9 M. Chen 10 Huawei 11 December 18, 2015 13 Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures 14 draft-smack-mpls-rfc4379bis-09 16 Abstract 18 This document describes a simple and efficient mechanism that can be 19 used to detect data plane failures in Multi-Protocol Label Switching 20 (MPLS) Label Switched Paths (LSPs). There are two parts to this 21 document: information carried in an MPLS "echo request" and "echo 22 reply" for the purposes of fault detection and isolation, and 23 mechanisms for reliably sending the echo reply. 25 This document obsoletes RFC 4379. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on June 20, 2016. 44 Copyright Notice 46 Copyright (c) 2015 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4 63 1.2. Structure of This Document . . . . . . . . . . . . . . . 4 64 1.3. Contributors . . . . . . . . . . . . . . . . . . . . . . 4 65 1.4. Scope of RFC4379bis work . . . . . . . . . . . . . . . . 5 66 1.5. ToDo . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 2.1. Use of Address Range 127/8 . . . . . . . . . . . . . . . 6 69 2.2. Router Alert Option . . . . . . . . . . . . . . . . . . . 8 70 3. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . 8 71 3.1. Return Codes . . . . . . . . . . . . . . . . . . . . . . 13 72 3.2. Target FEC Stack . . . . . . . . . . . . . . . . . . . . 13 73 3.2.1. LDP IPv4 Prefix . . . . . . . . . . . . . . . . . . . 15 74 3.2.2. LDP IPv6 Prefix . . . . . . . . . . . . . . . . . . . 15 75 3.2.3. RSVP IPv4 LSP . . . . . . . . . . . . . . . . . . . . 15 76 3.2.4. RSVP IPv6 LSP . . . . . . . . . . . . . . . . . . . . 16 77 3.2.5. VPN IPv4 Prefix . . . . . . . . . . . . . . . . . . . 16 78 3.2.6. VPN IPv6 Prefix . . . . . . . . . . . . . . . . . . . 17 79 3.2.7. L2 VPN Endpoint . . . . . . . . . . . . . . . . . . . 18 80 3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated) . . . . . . . 18 81 3.2.9. FEC 128 Pseudowire - IPv4 (Current) . . . . . . . . . 18 82 3.2.10. FEC 129 Pseudowire - IPv4 . . . . . . . . . . . . . . 19 83 3.2.11. BGP Labeled IPv4 Prefix . . . . . . . . . . . . . . . 20 84 3.2.12. BGP Labeled IPv6 Prefix . . . . . . . . . . . . . . . 20 85 3.2.13. Generic IPv4 Prefix . . . . . . . . . . . . . . . . . 21 86 3.2.14. Generic IPv6 Prefix . . . . . . . . . . . . . . . . . 21 87 3.2.15. Nil FEC . . . . . . . . . . . . . . . . . . . . . . . 22 88 3.2.16. FEC 128 Pseudowire - IPv6 . . . . . . . . . . . . . . 22 89 3.2.17. FEC 129 Pseudowire - IPv6 . . . . . . . . . . . . . . 23 90 3.3. Downstream Mapping (Deprecated) . . . . . . . . . . . . . 24 91 3.4. Downstream Detailed Mapping . . . . . . . . . . . . . . . 24 92 3.4.1. Multipath Information Encoding . . . . . . . . . . . 24 93 3.4.2. Downstream Router and Interface . . . . . . . . . . . 26 94 3.5. Pad TLV . . . . . . . . . . . . . . . . . . . . . . . . . 27 95 3.6. Vendor Enterprise Number . . . . . . . . . . . . . . . . 27 96 3.7. Interface and Label Stack . . . . . . . . . . . . . . . . 27 97 3.8. Errored TLVs . . . . . . . . . . . . . . . . . . . . . . 29 98 3.9. Reply TOS Byte TLV . . . . . . . . . . . . . . . . . . . 29 99 4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 29 100 4.1. Dealing with Equal-Cost Multi-Path (ECMP) . . . . . . . . 30 101 4.2. Testing LSPs That Are Used to Carry MPLS Payloads . . . . 31 102 4.3. Sending an MPLS Echo Request . . . . . . . . . . . . . . 31 103 4.4. Receiving an MPLS Echo Request . . . . . . . . . . . . . 32 104 4.4.1. FEC Validation . . . . . . . . . . . . . . . . . . . 38 105 4.5. Sending an MPLS Echo Reply . . . . . . . . . . . . . . . 39 106 4.6. Receiving an MPLS Echo Reply . . . . . . . . . . . . . . 40 107 4.7. Issue with VPN IPv4 and IPv6 Prefixes . . . . . . . . . . 40 108 4.8. Non-compliant Routers . . . . . . . . . . . . . . . . . . 41 109 5. Security Considerations . . . . . . . . . . . . . . . . . . . 41 110 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 111 6.1. Message Types, Reply Modes, Return Codes . . . . . . . . 43 112 6.2. TLVs . . . . . . . . . . . . . . . . . . . . . . . . . . 43 113 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 44 114 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 45 115 8.1. Normative References . . . . . . . . . . . . . . . . . . 45 116 8.2. Informative References . . . . . . . . . . . . . . . . . 46 117 Appendix A. Deprecated TLVs . . . . . . . . . . . . . . . . . . 47 118 A.1. FEC 128 Pseudowire . . . . . . . . . . . . . . . . . . . 47 119 A.2. Downstream Mapping(DSMAP) . . . . . . . . . . . . . . . . 48 120 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51 122 1. Introduction 124 This document describes a simple and efficient mechanism that can be 125 used to detect data plane failures in MPLS Label Switched Paths 126 (LSPs). There are two parts to this document: information carried in 127 an MPLS "echo request" and "echo reply", and mechanisms for 128 transporting the echo reply. The first part aims at providing enough 129 information to check correct operation of the data plane, as well as 130 a mechanism to verify the data plane against the control plane, and 131 thereby localize faults. The second part suggests two methods of 132 reliable reply channels for the echo request message for more robust 133 fault isolation. 135 An important consideration in this design is that MPLS echo requests 136 follow the same data path that normal MPLS packets would traverse. 137 MPLS echo requests are meant primarily to validate the data plane, 138 and secondarily to verify the data plane against the control plane. 139 Mechanisms to check the control plane are valuable, but are not 140 covered in this document. 142 This document makes special use of the address range 127/8. This is 143 an exception to the behavior defined in RFC 1122 [RFC1122] and 144 updates that RFC. The motivation for this change and the details of 145 this exceptional use are discussed in section 2.1 below. 147 1.1. Conventions 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 151 document are to be interpreted as described in RFC 2119 [RFC2119]. 153 The term "Must Be Zero" (MBZ) is used in object descriptions for 154 reserved fields. These fields MUST be set to zero when sent and 155 ignored on receipt. 157 Terminology pertaining to L2 and L3 Virtual Private Networks (VPNs) 158 is defined in [RFC4026]. 160 Since this document refers to the MPLS Time to Live (TTL) far more 161 frequently than the IP TTL, the authors have chosen the convention of 162 using the unqualified "TTL" to mean "MPLS TTL" and using "IP TTL" for 163 the TTL value in the IP header. 165 1.2. Structure of This Document 167 The body of this memo contains four main parts: motivation, MPLS echo 168 request/reply packet format, LSP ping operation, and a reliable 169 return path. It is suggested that first-time readers skip the actual 170 packet formats and read the Theory of Operation first; the document 171 is structured the way it is to avoid forward references. 173 1.3. Contributors 175 A mechanism used to detect data plane failures in Multi-Protocol 176 Label Switching (MPLS) Label Switched Paths (LSPs) was originally 177 published as RFC 4379 in February 2006. It was produced by the MPLS 178 Working Group of the IETF and was jointly authored by Kireeti 179 Kompella and George Swallow. 181 The following made vital contributions to all aspects of the original 182 RFC 4379, and much of the material came out of debate and discussion 183 among this group. 185 Ronald P. Bonica, Juniper Networks, Inc. 186 Dave Cooper, Global Crossing 187 Ping Pan, Hammerhead Systems 188 Nischal Sheth, Juniper Networks, Inc. 189 Sanjay Wadhwa, Juniper Networks, Inc. 191 1.4. Scope of RFC4379bis work 193 The goal of this document is to take LSP Ping to an Internet 194 Standard. 196 [RFC4379] defines the basic mechanism for MPLS LSP validation that 197 can be used for fault detection and isolation. The scope of this 198 document also is to address various updates to MPLS LSP Ping, 199 including: 201 1. Updates to all references and citations. Obsoleted RFCs 2434, 202 2030, and 3036 are respectively replaced with RFCs 5226, 5905, 203 and 5036. Additionally, these three documents published as RFCs: 204 RFCs 4447, 5085, and 4761. 205 2. Incorporate all outstanding Errata. These include Erratum with 206 IDs: 108, 1418, 1714, 1786, 3399, 742, and 2978. 207 3. Replace EXP with Traffic Class (TC), based on the update from RFC 208 5462. 209 4. Incorporate the updates from RFC 6829, adding the PW FECs 210 advertised over IPv6. 211 5. Incorporate the updates from RFC 7506, adding IPv6 Router Alert 212 Option for MPLS OAM. 214 1.5. ToDo 216 This section should be empty, and removed, prior to publication. 217 ToDos: 219 1. Evaluation of which of the RFCs that updated RFC 4379 need to be 220 incorporated into this 4379bis document. Specifically, these 221 RFCs updated RFC 4379: 6424, 6425, 6426 and 7537. RFCs that 222 updated RFC 4379 and are incorporated into this 4379bis, will be 223 Obsoleted by 4379bis. 224 2. Review IANA Allocations 226 2. Motivation 228 When an LSP fails to deliver user traffic, the failure cannot always 229 be detected by the MPLS control plane. There is a need to provide a 230 tool that would enable users to detect such traffic "black holes" or 231 misrouting within a reasonable period of time, and a mechanism to 232 isolate faults. 234 In this document, we describe a mechanism that accomplishes these 235 goals. This mechanism is modeled after the ping/traceroute paradigm: 236 ping (ICMP echo request [RFC0792]) is used for connectivity checks, 237 and traceroute is used for hop-by-hop fault localization as well as 238 path tracing. This document specifies a "ping" mode and a 239 "traceroute" mode for testing MPLS LSPs. 241 The basic idea is to verify that packets that belong to a particular 242 Forwarding Equivalence Class (FEC) actually end their MPLS path on a 243 Label Switching Router (LSR) that is an egress for that FEC. This 244 document proposes that this test be carried out by sending a packet 245 (called an "MPLS echo request") along the same data path as other 246 packets belonging to this FEC. An MPLS echo request also carries 247 information about the FEC whose MPLS path is being verified. This 248 echo request is forwarded just like any other packet belonging to 249 that FEC. In "ping" mode (basic connectivity check), the packet 250 should reach the end of the path, at which point it is sent to the 251 control plane of the egress LSR, which then verifies whether it is 252 indeed an egress for the FEC. In "traceroute" mode (fault 253 isolation), the packet is sent to the control plane of each transit 254 LSR, which performs various checks that it is indeed a transit LSR 255 for this path; this LSR also returns further information that helps 256 check the control plane against the data plane, i.e., that forwarding 257 matches what the routing protocols determined as the path. 259 One way these tools can be used is to periodically ping an FEC to 260 ensure connectivity. If the ping fails, one can then initiate a 261 traceroute to determine where the fault lies. One can also 262 periodically traceroute FECs to verify that forwarding matches the 263 control plane; however, this places a greater burden on transit LSRs 264 and thus should be used with caution. 266 2.1. Use of Address Range 127/8 268 As described above, LSP ping is intended as a diagnostic tool. It is 269 intended to enable providers of an MPLS-based service to isolate 270 network faults. In particular, LSP ping needs to diagnose situations 271 where the control and data planes are out of sync. It performs this 272 by routing an MPLS echo request packet based solely on its label 273 stack. That is, the IP destination address is never used in a 274 forwarding decision. In fact, the sender of an MPLS echo request 275 packet may not know, a priori, the address of the router at the end 276 of the LSP. 278 Providers of MPLS-based services also need the ability to trace all 279 of the possible paths that an LSP may take. Since most MPLS services 280 are based on IP unicast forwarding, these paths are subject to equal- 281 cost multi-path (ECMP) load sharing. 283 This leads to the following requirements: 285 1. Although the LSP in question may be broken in unknown ways, the 286 likelihood of a diagnostic packet being delivered to a user of an 287 MPLS service MUST be held to an absolute minimum. 289 2. If an LSP is broken in such a way that it prematurely terminates, 290 the diagnostic packet MUST NOT be IP forwarded. 292 3. A means of varying the diagnostic packets such that they exercise 293 all ECMP paths is thus REQUIRED. 295 Clearly, using general unicast addresses satisfies neither of the 296 first two requirements. A number of other options for addresses were 297 considered, including a portion of the private address space (as 298 determined by the network operator) and the newly designated IPv4 299 link local addresses. Use of the private address space was deemed 300 ineffective since the leading MPLS-based service is an IPv4 Virtual 301 Private Network (VPN). VPNs often use private addresses. 303 The IPv4 link local addresses are more attractive in that the scope 304 over which they can be forwarded is limited. However, if one were to 305 use an address from this range, it would still be possible for the 306 first recipient of a diagnostic packet that "escaped" from a broken 307 LSP to have that address assigned to the interface on which it 308 arrived and thus could mistakenly receive such a packet. 309 Furthermore, the IPv4 link local address range has only recently been 310 allocated. Many deployed routers would forward a packet with an 311 address from that range toward the default route. 313 The 127/8 range for IPv4 and that same range embedded in as 314 IPv4-mapped IPv6 addresses for IPv6 was chosen for a number of 315 reasons. 317 RFC 1122 allocates the 127/8 as "Internal host loopback address" and 318 states: "Addresses of this form MUST NOT appear outside a host." 319 Thus, the default behavior of hosts is to discard such packets. This 320 helps to ensure that if a diagnostic packet is misdirected to a host, 321 it will be silently discarded. 323 RFC 1812 [RFC1812] states: 325 A router SHOULD NOT forward, except over a loopback interface, any 326 packet that has a destination address on network 127. A router 327 MAY have a switch that allows the network manager to disable these 328 checks. If such a switch is provided, it MUST default to 329 performing the checks. 331 This helps to ensure that diagnostic packets are never IP forwarded. 333 The 127/8 address range provides 16M addresses allowing wide 334 flexibility in varying addresses to exercise ECMP paths. Finally, as 335 an implementation optimization, the 127/8 provides an easy means of 336 identifying possible LSP packets. 338 2.2. Router Alert Option 340 This document requires the use of the Router Alert Option (RAO) set 341 in IP header in order to have the transit node process the MPLS OAM 342 payload. 344 [RFC2113] defines a generic Option Value 0x0 for IPv4 RAO that alerts 345 transit router to examine the IPv4 packet. [RFC7506] defines MPLS 346 OAM Option Value 69 for IPv6 RAO to alert transit routers to examine 347 the IPv6 packet more closely for MPLS OAM purposes. 349 The use of the Router Alert IP Option in this document is as follows: 351 In case of an IPv4 header, the generic IPv4 RAO value 0x0 352 [RFC2113] SHOULD be used. In case of an IPv6 header, the IPv6 RAO 353 value (69) for MPLS OAM [RFC7506] MUST be used. 355 3. Packet Format 357 An MPLS echo request is a (possibly labeled) IPv4 or IPv6 UDP packet; 358 the contents of the UDP packet have the following format: 360 0 1 2 3 361 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 1 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | Version Number | Global Flags | 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 | Message Type | Reply mode | Return Code | Return Subcode| 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | Sender's Handle | 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 369 | Sequence Number | 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | TimeStamp Sent (seconds) | 372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 | TimeStamp Sent (seconds fraction) | 374 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 375 | TimeStamp Received (seconds) | 376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 | TimeStamp Received (seconds fraction) | 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 | TLVs ... | 380 . . 381 . . 382 . . 383 | | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 The Version Number is currently 1. (Note: the version number is to 387 be incremented whenever a change is made that affects the ability of 388 an implementation to correctly parse or process an MPLS echo request/ 389 reply. These changes include any syntactic or semantic changes made 390 to any of the fixed fields, or to any Type-Length-Value (TLV) or sub- 391 TLV assignment or format that is defined at a certain version number. 392 The version number may not need to be changed if an optional TLV or 393 sub-TLV is added.) 395 The Global Flags field is a bit vector with the following format: 397 0 1 398 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 | MBZ |V| 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 403 One flag is defined for now, the V bit; the rest MUST be set to zero 404 when sending and ignored on receipt. 406 The V (Validate FEC Stack) flag is set to 1 if the sender wants the 407 receiver to perform FEC Stack validation; if V is 0, the choice is 408 left to the receiver. 410 The Message Type is one of the following: 412 Value Meaning 413 ----- ------- 414 1 MPLS echo request 415 2 MPLS echo reply 417 The Reply Mode can take one of the following values: 419 Value Meaning 420 ----- ------- 421 1 Do not reply 422 2 Reply via an IPv4/IPv6 UDP packet 423 3 Reply via an IPv4/IPv6 UDP packet with Router Alert 424 4 Reply via application level control channel 426 An MPLS echo request with 1 (Do not reply) in the Reply Mode field 427 may be used for one-way connectivity tests; the receiving router may 428 log gaps in the Sequence Numbers and/or maintain delay/jitter 429 statistics. An MPLS echo request would normally have 2 (Reply via an 430 IPv4/IPv6 UDP packet) in the Reply Mode field. If the normal IP 431 return path is deemed unreliable, one may use 3 (Reply via an IPv4/ 432 IPv6 UDP packet with Router Alert). Note that this requires that all 433 intermediate routers understand and know how to forward MPLS echo 434 replies. The echo reply uses the same IP version number as the 435 received echo request, i.e., an IPv4 encapsulated echo reply is sent 436 in response to an IPv4 encapsulated echo request. 438 Some applications support an IP control channel. One such example is 439 the associated control channel defined in Virtual Circuit 440 Connectivity Verification (VCCV) [RFC5085]. Any application that 441 supports an IP control channel between its control entities may set 442 the Reply Mode to 4 (Reply via application level control channel) to 443 ensure that replies use that same channel. Further definition of 444 this codepoint is application specific and thus beyond the scope of 445 this document. 447 Return Codes and Subcodes are described in the next section. 449 The Sender's Handle is filled in by the sender, and returned 450 unchanged by the receiver in the echo reply (if any). There are no 451 semantics associated with this handle, although a sender may find 452 this useful for matching up requests with replies. 454 The Sequence Number is assigned by the sender of the MPLS echo 455 request and can be (for example) used to detect missed replies. 457 The TimeStamp Sent is the time-of-day (according to the sender's 458 clock) in NTP format [RFC5905] when the MPLS echo request is sent. 459 The TimeStamp Received in an echo reply is the time-of-day (according 460 to the receiver's clock) in NTP format that the corresponding echo 461 request was received. 463 TLVs (Type-Length-Value tuples) have the following format: 465 0 1 2 3 466 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 1 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 468 | Type | Length | 469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 | Value | 471 . . 472 . . 473 . . 474 | | 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 Types are defined below; Length is the length of the Value field in 478 octets. The Value field depends on the Type; it is zero padded to 479 align to a 4-octet boundary. TLVs may be nested within other TLVs, 480 in which case the nested TLVs are called sub-TLVs. Sub-TLVs have 481 independent types and MUST also be 4-octet aligned. 483 Two examples of how TLV and sub-TLV length are computed, and of how 484 sub-TLVs are padded to be 4-octet aligned as follows: 486 0 1 2 3 487 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 1 488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 | Type = 1 (LDP IPv4 FEC) | Length = 5 | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | IPv4 prefix | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 | Prefix Length | Must Be Zero | 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 The Length for this TLV is 5. A Target FEC Stack TLV that contains 497 an LDP IPv4 FEC sub-TLV and a VPN IPv4 prefix sub-TLV has the 498 following format: 500 0 1 2 3 501 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 1 502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 503 | Type = 1 (FEC TLV) | Length = 32 | 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | sub-Type = 1 (LDP IPv4 FEC) | Length = 5 | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | IPv4 prefix | 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 | Prefix Length | Must Be Zero | 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | sub-Type = 6 (VPN IPv4 prefix)| Length = 13 | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 | Route Distinguisher | 514 | (8 octets) | 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 | IPv4 prefix | 517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 | Prefix Length | Must Be Zero | 519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 A description of the Types and Values of the top-level TLVs for LSP 522 ping are given below: 524 Type # Value Field 525 ------ ----------- 526 1 Target FEC Stack 527 2 Downstream Mapping 528 3 Pad 529 4 Not Assigned 530 5 Vendor Enterprise Number 531 6 Not Assigned 532 7 Interface and Label Stack 533 8 Not Assigned 534 9 Errored TLVs 535 10 Reply TOS Byte 537 Types less than 32768 (i.e., with the high-order bit equal to 0) are 538 mandatory TLVs that MUST either be supported by an implementation or 539 result in the return code of 2 ("One or more of the TLVs was not 540 understood") being sent in the echo response. 542 Types greater than or equal to 32768 (i.e., with the high-order bit 543 equal to 1) are optional TLVs that SHOULD be ignored if the 544 implementation does not understand or support them. 546 3.1. Return Codes 548 The Return Code is set to zero by the sender. The receiver can set 549 it to one of the values listed below. The notation refers to 550 the Return Subcode. This field is filled in with the stack-depth for 551 those codes that specify that. For all other codes, the Return 552 Subcode MUST be set to zero. 554 Value Meaning 555 ----- ------- 556 0 No return code 557 1 Malformed echo request received 558 2 One or more of the TLVs was not understood 559 3 Replying router is an egress for the FEC at stack- 560 depth 561 4 Replying router has no mapping for the FEC at stack- 562 depth 563 5 Downstream Mapping Mismatch (See Note 1) 564 6 Upstream Interface Index Unknown (See Note 1) 565 7 Reserved 566 8 Label switched at stack-depth 567 9 Label switched but no MPLS forwarding at stack-depth 568 569 10 Mapping for this FEC is not the given label at stack- 570 depth 571 11 No label entry at stack-depth 572 12 Protocol not associated with interface at FEC stack- 573 depth 574 13 Premature termination of ping due to label stack 575 shrinking to a single label 577 Note 1 579 The Return Subcode contains the point in the label stack where 580 processing was terminated. If the RSC is 0, no labels were 581 processed. Otherwise the packet would have been label switched at 582 depth RSC. 584 3.2. Target FEC Stack 586 A Target FEC Stack is a list of sub-TLVs. The number of elements is 587 determined by looking at the sub-TLV length fields. 589 Sub-Type Length Value Field 590 -------- ------ ----------- 591 1 5 LDP IPv4 prefix 592 2 17 LDP IPv6 prefix 593 3 20 RSVP IPv4 LSP 594 4 56 RSVP IPv6 LSP 595 5 Not Assigned 596 6 13 VPN IPv4 prefix 597 7 25 VPN IPv6 prefix 598 8 14 L2 VPN endpoint 599 9 10 "FEC 128" Pseudowire - IPv4 (deprecated) 600 10 14 "FEC 128" Pseudowire - IPv4 601 11 16+ "FEC 129" Pseudowire - IPv4 602 12 5 BGP labeled IPv4 prefix 603 13 17 BGP labeled IPv6 prefix 604 14 5 Generic IPv4 prefix 605 15 17 Generic IPv6 prefix 606 16 4 Nil FEC 607 24 38 "FEC 128" Pseudowire - IPv6 608 25 40+ "FEC 129" Pseudowire - IPv6 610 Other FEC Types will be defined as needed. 612 Note that this TLV defines a stack of FECs, the first FEC element 613 corresponding to the top of the label stack, etc. 615 An MPLS echo request MUST have a Target FEC Stack that describes the 616 FEC Stack being tested. For example, if an LSR X has an LDP mapping 617 [RFC5036] for 192.168.1.1 (say, label 1001), then to verify that 618 label 1001 does indeed reach an egress LSR that announced this prefix 619 via LDP, X can send an MPLS echo request with an FEC Stack TLV with 620 one FEC in it, namely, of type LDP IPv4 prefix, with prefix 621 192.168.1.1/32, and send the echo request with a label of 1001. 623 Say LSR X wanted to verify that a label stack of <1001, 23456> is the 624 right label stack to use to reach a VPN IPv4 prefix [see 625 Section 3.2.5] of 10/8 in VPN foo. Say further that LSR Y with 626 loopback address 192.168.1.1 announced prefix 10/8 with Route 627 Distinguisher RD-foo-Y (which may in general be different from the 628 Route Distinguisher that LSR X uses in its own advertisements for VPN 629 foo), label 23456 and BGP next hop 192.168.1.1 [RFC4271]. Finally, 630 suppose that LSR X receives a label binding of 1001 for 192.168.1.1 631 via LDP. X has two choices in sending an MPLS echo request: X can 632 send an MPLS echo request with an FEC Stack TLV with a single FEC of 633 type VPN IPv4 prefix with a prefix of 10/8 and a Route Distinguisher 634 of RD-foo-Y. Alternatively, X can send an FEC Stack TLV with two 635 FECs, the first of type LDP IPv4 with a prefix of 192.168.1.1/32 and 636 the second of type of IP VPN with a prefix 10/8 with Route 637 Distinguisher of RD-foo-Y. In either case, the MPLS echo request 638 would have a label stack of <1001, 23456>. (Note: in this example, 639 1001 is the "outer" label and 23456 is the "inner" label.) 641 3.2.1. LDP IPv4 Prefix 643 The IPv4 Prefix FEC is defined in [RFC5036]. When an LDP IPv4 prefix 644 is encoded in a label stack, the following format is used. The value 645 consists of 4 octets of an IPv4 prefix followed by 1 octet of prefix 646 length in bits; the format is given below. The IPv4 prefix is in 647 network byte order; if the prefix is shorter than 32 bits, trailing 648 bits SHOULD be set to zero. See [RFC5036] for an example of a 649 Mapping for an IPv4 FEC. 651 0 1 2 3 652 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 1 653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 | IPv4 prefix | 655 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 | Prefix Length | Must Be Zero | 657 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 3.2.2. LDP IPv6 Prefix 661 The IPv6 Prefix FEC is defined in [RFC5036]. When an LDP IPv6 prefix 662 is encoded in a label stack, the following format is used. The value 663 consists of 16 octets of an IPv6 prefix followed by 1 octet of prefix 664 length in bits; the format is given below. The IPv6 prefix is in 665 network byte order; if the prefix is shorter than 128 bits, the 666 trailing bits SHOULD be set to zero. See [RFC5036] for an example of 667 a Mapping for an IPv6 FEC. 669 0 1 2 3 670 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 1 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 | IPv6 prefix | 673 | (16 octets) | 674 | | 675 | | 676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 | Prefix Length | Must Be Zero | 678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 680 3.2.3. RSVP IPv4 LSP 682 The value has the format below. The value fields are taken from RFC 683 3209, sections 4.6.1.1 and 4.6.2.1. See [RFC3209]. 685 0 1 2 3 686 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 1 687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 688 | IPv4 tunnel end point address | 689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 690 | Must Be Zero | Tunnel ID | 691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 692 | Extended Tunnel ID | 693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 694 | IPv4 tunnel sender address | 695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 696 | Must Be Zero | LSP ID | 697 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 699 3.2.4. RSVP IPv6 LSP 701 The value has the format below. The value fields are taken from RFC 702 3209, sections 4.6.1.2 and 4.6.2.2. See [RFC3209]. 704 0 1 2 3 705 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 1 706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 | IPv6 tunnel end point address | 708 | | 709 | | 710 | | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | Must Be Zero | Tunnel ID | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | Extended Tunnel ID | 715 | | 716 | | 717 | | 718 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 719 | IPv6 tunnel sender address | 720 | | 721 | | 722 | | 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 724 | Must Be Zero | LSP ID | 725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 3.2.5. VPN IPv4 Prefix 729 VPN-IPv4 Network Layer Routing Information (NLRI) is defined in 730 [RFC4365]. This document uses the term VPN IPv4 prefix for a VPN- 731 IPv4 NLRI that has been advertised with an MPLS label in BGP. See 732 [RFC3107]. 734 When a VPN IPv4 prefix is encoded in a label stack, the following 735 format is used. The value field consists of the Route Distinguisher 736 advertised with the VPN IPv4 prefix, the IPv4 prefix (with trailing 0 737 bits to make 32 bits in all), and a prefix length, as follows: 739 0 1 2 3 740 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 1 741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 742 | Route Distinguisher | 743 | (8 octets) | 744 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 745 | IPv4 prefix | 746 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 747 | Prefix Length | Must Be Zero | 748 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 750 The Route Distinguisher (RD) is an 8-octet identifier; it does not 751 contain any inherent information. The purpose of the RD is solely to 752 allow one to create distinct routes to a common IPv4 address prefix. 753 The encoding of the RD is not important here. When matching this 754 field to the local FEC information, it is treated as an opaque value. 756 3.2.6. VPN IPv6 Prefix 758 VPN-IPv6 Network Layer Routing Information (NLRI) is defined in 759 [RFC4365]. This document uses the term VPN IPv6 prefix for a VPN- 760 IPv6 NLRI that has been advertised with an MPLS label in BGP. See 761 [RFC3107]. 763 When a VPN IPv6 prefix is encoded in a label stack, the following 764 format is used. The value field consists of the Route Distinguisher 765 advertised with the VPN IPv6 prefix, the IPv6 prefix (with trailing 0 766 bits to make 128 bits in all), and a prefix length, as follows: 768 0 1 2 3 769 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 1 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 771 | Route Distinguisher | 772 | (8 octets) | 773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 | IPv6 prefix | 775 | | 776 | | 777 | | 778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 779 | Prefix Length | Must Be Zero | 780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 782 The Route Distinguisher is identical to the VPN IPv4 Prefix RD, 783 except that it functions here to allow the creation of distinct 784 routes to IPv6 prefixes. See Section 3.2.5. When matching this 785 field to local FEC information, it is treated as an opaque value. 787 3.2.7. L2 VPN Endpoint 789 VPLS stands for Virtual Private LAN Service. The terms VPLS BGP NLRI 790 and VE ID (VPLS Edge Identifier) are defined in [RFC4761]. This 791 document uses the simpler term L2 VPN endpoint when referring to a 792 VPLS BGP NLRI. The Route Distinguisher is an 8-octet identifier used 793 to distinguish information about various L2 VPNs advertised by a 794 node. The VE ID is a 2-octet identifier used to identify a 795 particular node that serves as the service attachment point within a 796 VPLS. The structure of these two identifiers is unimportant here; 797 when matching these fields to local FEC information, they are treated 798 as opaque values. The encapsulation type is identical to the PW Type 799 in section 3.2.8 below. 801 When an L2 VPN endpoint is encoded in a label stack, the following 802 format is used. The value field consists of a Route Distinguisher (8 803 octets), the sender (of the ping)'s VE ID (2 octets), the receiver's 804 VE ID (2 octets), and an encapsulation type (2 octets), formatted as 805 follows: 807 0 1 2 3 808 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 1 809 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 810 | Route Distinguisher | 811 | (8 octets) | 812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 813 | Sender's VE ID | Receiver's VE ID | 814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 815 | Encapsulation Type | Must Be Zero | 816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 818 3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated) 820 See Appendix A.1 for details 822 3.2.9. FEC 128 Pseudowire - IPv4 (Current) 824 FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID 825 (Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero 826 32-bit connection ID. The PW Type is a 15-bit number indicating the 827 encapsulation type. It is carried right justified in the field below 828 termed encapsulation type with the high-order bit set to zero. 830 Both of these fields are treated in this protocol as opaque values. 831 When matching these field to the local FEC information, the match 832 MUST be exact. 834 When an FEC 128 is encoded in a label stack, the following format is 835 used. The value field consists of the sender's PE IPv4 address (the 836 source address of the targeted LDP session), the remote PE IPv4 837 address (the destination address of the targeted LDP session), the PW 838 ID, and the encapsulation type as follows: 840 0 1 2 3 841 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 1 842 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 843 | Sender's PE IPv4 Address | 844 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 845 | Remote PE IPv4 Address | 846 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 847 | PW ID | 848 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 849 | PW Type | Must Be Zero | 850 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 852 3.2.10. FEC 129 Pseudowire - IPv4 854 FEC 129 (0x81) and the terms PW Type, Attachment Group Identifier 855 (AGI), Attachment Group Identifier Type (AGI Type), Attachment 856 Individual Identifier Type (AII Type), Source Attachment Individual 857 Identifier (SAII), and Target Attachment Individual Identifier (TAII) 858 are defined in [RFC4447]. The PW Type is a 15-bit number indicating 859 the encapsulation type. It is carried right justified in the field 860 below PW Type with the high-order bit set to zero. All the other 861 fields are treated as opaque values and copied directly from the FEC 862 129 format. All of these values together uniquely define the FEC 863 within the scope of the LDP session identified by the source and 864 remote PE IPv4 addresses. 866 When an FEC 129 is encoded in a label stack, the following format is 867 used. The Length of this TLV is 16 + AGI length + SAII length + TAII 868 length. Padding is used to make the total length a multiple of 4; 869 the length of the padding is not included in the Length field. 871 0 1 2 3 872 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 1 873 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 874 | Sender's PE IPv4 Address | 875 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 876 | Remote PE IPv4 Address | 877 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 878 | PW Type | AGI Type | AGI Length | 879 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 880 ~ AGI Value ~ 881 | | 882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 883 | AII Type | SAII Length | SAII Value | 884 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 885 ~ SAII Value (continued) ~ 886 | | 887 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 888 | AII Type | TAII Length | TAII Value | 889 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 890 ~ TAII Value (continued) ~ 891 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 892 | TAII (cont.) | 0-3 octets of zero padding | 893 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 895 3.2.11. BGP Labeled IPv4 Prefix 897 BGP labeled IPv4 prefixes are defined in [RFC3107]. When a BGP 898 labeled IPv4 prefix is encoded in a label stack, the following format 899 is used. The value field consists the IPv4 prefix (with trailing 0 900 bits to make 32 bits in all), and the prefix length, as follows: 902 0 1 2 3 903 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 1 904 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 905 | IPv4 Prefix | 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 907 | Prefix Length | Must Be Zero | 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 910 3.2.12. BGP Labeled IPv6 Prefix 912 BGP labeled IPv6 prefixes are defined in [RFC3107]. When a BGP 913 labeled IPv6 prefix is encoded in a label stack, the following format 914 is used. The value consists of 16 octets of an IPv6 prefix followed 915 by 1 octet of prefix length in bits; the format is given below. The 916 IPv6 prefix is in network byte order; if the prefix is shorter than 917 128 bits, the trailing bits SHOULD be set to zero. 919 0 1 2 3 920 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 1 921 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 922 | IPv6 prefix | 923 | (16 octets) | 924 | | 925 | | 926 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 927 | Prefix Length | Must Be Zero | 928 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 930 3.2.13. Generic IPv4 Prefix 932 The value consists of 4 octets of an IPv4 prefix followed by 1 octet 933 of prefix length in bits; the format is given below. The IPv4 prefix 934 is in network byte order; if the prefix is shorter than 32 bits, 935 trailing bits SHOULD be set to zero. This FEC is used if the 936 protocol advertising the label is unknown or may change during the 937 course of the LSP. An example is an inter-AS LSP that may be 938 signaled by LDP in one Autonomous System (AS), by RSVP-TE [RFC3209] 939 in another AS, and by BGP between the ASes, such as is common for 940 inter-AS VPNs. 942 0 1 2 3 943 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 1 944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 945 | IPv4 prefix | 946 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 947 | Prefix Length | Must Be Zero | 948 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 950 3.2.14. Generic IPv6 Prefix 952 The value consists of 16 octets of an IPv6 prefix followed by 1 octet 953 of prefix length in bits; the format is given below. The IPv6 prefix 954 is in network byte order; if the prefix is shorter than 128 bits, the 955 trailing bits SHOULD be set to zero. 957 0 1 2 3 958 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 1 959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 960 | IPv6 prefix | 961 | (16 octets) | 962 | | 963 | | 964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 965 | Prefix Length | Must Be Zero | 966 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 968 3.2.15. Nil FEC 970 At times, labels from the reserved range, e.g., Router Alert and 971 Explicit-null, may be added to the label stack for various diagnostic 972 purposes such as influencing load-balancing. These labels may have 973 no explicit FEC associated with them. The Nil FEC Stack is defined 974 to allow a Target FEC Stack sub-TLV to be added to the Target FEC 975 Stack to account for such labels so that proper validation can still 976 be performed. 978 The Length is 4. Labels are 20-bit values treated as numbers. 980 0 1 2 3 981 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 1 982 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 983 | Label | MBZ | 984 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 986 Label is the actual label value inserted in the label stack; the MBZ 987 fields MUST be zero when sent and ignored on receipt. 989 3.2.16. FEC 128 Pseudowire - IPv6 991 The FEC 128 Pseudowire IPv6 sub-TLV has a structure consistent with 992 the FEC 128 Pseudowire IPv4 sub-TLV as described in Section 3.2.9. 993 The value field consists of the Sender's PE IPv6 address (the source 994 address of the targeted LDP session), the remote PE IPv6 address (the 995 destination address of the targeted LDP session), the PW ID, and the 996 encapsulation type as follows: 998 0 1 2 3 999 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 1000 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1001 ~ Sender's PE IPv6 Address ~ 1002 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1003 ~ Remote PE IPv6 Address ~ 1004 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1005 | PW ID | 1006 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1007 | PW Type | Must Be Zero | 1008 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1010 Sender's PE IPv6 Address: The source IP address of the target IPv6 1011 LDP session. 16 octets. 1013 Remote PE IPv6 Address: The destination IP address of the target IPv6 1014 LDP session. 16 octets. 1016 PW ID: Same as FEC 128 Pseudowire IPv4 in Section 3.2.9. 1018 PW Type: Same as FEC 128 Pseudowire IPv4 in Section 3.2.9. 1020 3.2.17. FEC 129 Pseudowire - IPv6 1022 The FEC 129 Pseudowire IPv6 sub-TLV has a structure consistent with 1023 the FEC 129 Pseudowire IPv4 sub-TLV as described in Section 3.2.10. 1024 When an FEC 129 is encoded in a label stack, the following format is 1025 used. The length of this TLV is 40 + AGI (Attachment Group 1026 Identifier) length + SAII (Source Attachment Individual Identifier) 1027 length + TAII (Target Attachment Individual Identifier) length. 1028 Padding is used to make the total length a multiple of 4; the length 1029 of the padding is not included in the Length field. 1031 0 1 2 3 1032 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 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 ~ Sender's PE IPv6 Address ~ 1035 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 ~ Remote PE IPv6 Address ~ 1037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1038 | PW Type | AGI Type | AGI Length | 1039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1040 ~ AGI Value ~ 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1042 | AII Type | SAII Length | SAII Value | 1043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 ~ SAII Value (continued) ~ 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1046 | AII Type | TAII Length | TAII Value | 1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1048 ~ TAII Value (continued) ~ 1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1050 | TAII (cont.) | 0-3 octets of zero padding | 1051 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1053 Sender's PE IPv6 Address: The source IP address of the target IPv6 1054 LDP session. 16 octets. 1056 Remote PE IPv6 Address: The destination IP address of the target IPv6 1057 LDP session. 16 octets. 1059 The other fields are the same as FEC 129 Pseudowire IPv4 in 1060 Section 3.2.10. 1062 3.3. Downstream Mapping (Deprecated) 1064 See Appendix A.2 for more details. 1066 3.4. Downstream Detailed Mapping 1068 The format of this TLV is defined in section 3.3 of [RFC6424] 1070 3.4.1. Multipath Information Encoding 1072 The Multipath Information encodes labels or addresses that will 1073 exercise this path. The Multipath Information depends on the 1074 Multipath Type. The contents of the field are shown in the table 1075 above. IPv4 addresses are drawn from the range 127/8; IPv6 addresses 1076 are drawn from the range 0:0:0:0:0:FFFF:7F00/104. Labels are treated 1077 as numbers, i.e., they are right justified in the field. For Type 4, 1078 ranges indicated by Address pairs MUST NOT overlap and MUST be in 1079 ascending sequence. 1081 Type 8 allows a more dense encoding of IP addresses. The IP prefix 1082 is formatted as a base IP address with the non-prefix low-order bits 1083 set to zero. The maximum prefix length is 27. Following the prefix 1084 is a mask of length 2^(32-prefix length) bits for IPv4 and 1085 2^(128-prefix length) bits for IPv6. Each bit set to 1 represents a 1086 valid address. The address is the base IPv4 address plus the 1087 position of the bit in the mask where the bits are numbered left to 1088 right beginning with zero. For example, the IPv4 addresses 1089 127.2.1.0, 127.2.1.5-127.2.1.15, and 127.2.1.20-127.2.1.29 would be 1090 encoded as follows: 1092 0 1 2 3 1093 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 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1095 |0 1 1 1 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0| 1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1097 |1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0| 1098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1100 Those same addresses embedded in IPv6 would be encoded as follows: 1102 0 1 2 3 1103 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 1104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1105 |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0| 1106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1107 |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0| 1108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1109 |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1| 1110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1111 |0 1 1 1 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0| 1112 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1113 |1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0| 1114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 Type 9 allows a more dense encoding of labels. The label prefix is 1117 formatted as a base label value with the non-prefix low-order bits 1118 set to zero. The maximum prefix (including leading zeros due to 1119 encoding) length is 27. Following the prefix is a mask of length 1120 2^(32-prefix length) bits. Each bit set to one represents a valid 1121 label. The label is the base label plus the position of the bit in 1122 the mask where the bits are numbered left to right beginning with 1123 zero. Label values of all the odd numbers between 1152 and 1279 1124 would be encoded as follows: 1126 0 1 2 3 1127 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 1128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1129 |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0| 1130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1131 |0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1| 1132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1133 |0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1| 1134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1135 |0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1| 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 |0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1| 1138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1140 If the received Multipath Information is non-null, the labels and IP 1141 addresses MUST be picked from the set provided. If none of these 1142 labels or addresses map to a particular downstream interface, then 1143 for that interface, the type MUST be set to 0. If the received 1144 Multipath Information is null (i.e., Multipath Length = 0, or for 1145 Types 8 and 9, a mask of all zeros), the type MUST be set to 0. 1147 For example, suppose LSR X at hop 10 has two downstream LSRs, Y and 1148 Z, for the FEC in question. The received X could return Multipath 1149 Type 4, with low/high IP addresses of 127.1.1.1->127.1.1.255 for 1150 downstream LSR Y and 127.2.1.1->127.2.1.255 for downstream LSR Z. 1151 The head end reflects this information to LSR Y. Y, which has three 1152 downstream LSRs, U, V, and W, computes that 127.1.1.1->127.1.1.127 1153 would go to U and 127.1.1.128-> 127.1.1.255 would go to V. Y would 1154 then respond with 3 "Downstream Detailed Mapping" TLVs: to U, with 1155 Multipath Type 4 (127.1.1.1->127.1.1.127); to V, with Multipath Type 1156 4 (127.1.1.127->127.1.1.255); and to W, with Multipath Type 0. 1158 Note that computing Multipath Information may impose a significant 1159 processing burden on the receiver. A receiver MAY thus choose to 1160 process a subset of the received prefixes. The sender, on receiving 1161 a reply to a Downstream Detailed Mapping with partial information, 1162 SHOULD assume that the prefixes missing in the reply were skipped by 1163 the receiver, and MAY re-request information about them in a new echo 1164 request. 1166 The encoding of Multipath information in scenarios where few LSRs 1167 apply Entropy label based load balancing while other LSRs are non-EL 1168 (IP based) load balancing will be defined in a different document. 1170 The encoding of multipath information in scenarios where LSR have 1171 Layer 2 ECMP over Link Aggregation Group (LAG) interfaces will be 1172 defined in different document. 1174 3.4.2. Downstream Router and Interface 1176 The notion of "downstream router" and "downstream interface" should 1177 be explained. Consider an LSR X. If a packet that was originated 1178 with TTL n>1 arrived with outermost label L and TTL=1 at LSR X, X 1179 must be able to compute which LSRs could receive the packet if it was 1180 originated with TTL=n+1, over which interface the request would 1181 arrive and what label stack those LSRs would see. (It is outside the 1182 scope of this document to specify how this computation is done.) The 1183 set of these LSRs/interfaces consists of the downstream routers/ 1184 interfaces (and their corresponding labels) for X with respect to L. 1185 Each pair of downstream router and interface requires a separate 1186 Downstream Detailed Mapping to be added to the reply. 1188 The case where X is the LSR originating the echo request is a special 1189 case. X needs to figure out what LSRs would receive the MPLS echo 1190 request for a given FEC Stack that X originates with TTL=1. 1192 The set of downstream routers at X may be alternative paths (see the 1193 discussion below on ECMP) or simultaneous paths (e.g., for MPLS 1194 multicast). In the former case, the Multipath Information is used as 1195 a hint to the sender as to how it may influence the choice of these 1196 alternatives. 1198 3.5. Pad TLV 1200 The value part of the Pad TLV contains a variable number (>= 1) of 1201 octets. The first octet takes values from the following table; all 1202 the other octets (if any) are ignored. The receiver SHOULD verify 1203 that the TLV is received in its entirety, but otherwise ignores the 1204 contents of this TLV, apart from the first octet. 1206 Value Meaning 1207 ----- ------- 1208 1 Drop Pad TLV from reply 1209 2 Copy Pad TLV to reply 1210 3-255 Reserved for future use 1212 3.6. Vendor Enterprise Number 1214 SMI Private Enterprise Numbers are maintained by IANA. The Length is 1215 always 4; the value is the SMI Private Enterprise code, in network 1216 octet order, of the vendor with a Vendor Private extension to any of 1217 the fields in the fixed part of the message, in which case this TLV 1218 MUST be present. If none of the fields in the fixed part of the 1219 message have Vendor Private extensions, inclusion of this TLV is 1220 OPTIONAL. Vendor Private ranges for Message Types, Reply Modes, and 1221 Return Codes have been defined. When any of these are used, the 1222 Vendor Enterprise Number TLV MUST be included in the message. 1224 3.7. Interface and Label Stack 1226 The Interface and Label Stack TLV MAY be included in a reply message 1227 to report the interface on which the request message was received and 1228 the label stack that was on the packet when it was received. Only 1229 one such object may appear. The purpose of the object is to allow 1230 the upstream router to obtain the exact interface and label stack 1231 information as it appears at the replying LSR. 1233 The Length is K + 4*N octets; N is the number of labels in the label 1234 stack. Values for K are found in the description of Address Type 1235 below. The Value field of this TLV has the following format: 1237 0 1 2 3 1238 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 1239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1240 | Address Type | Must Be Zero | 1241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1242 | IP Address (4 or 16 octets) | 1243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1244 | Interface (4 or 16 octets) | 1245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1246 . . 1247 . . 1248 . Label Stack . 1249 . . 1250 . . 1251 . . 1252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1254 Address Type 1256 The Address Type indicates if the interface is numbered or 1257 unnumbered. It also determines the length of the IP Address and 1258 Interface fields. The resulting total for the initial part of the 1259 TLV is listed in the table below as "K Octets". The Address Type 1260 is set to one of the following values: 1262 Type # Address Type K Octets 1263 ------ ------------ -------- 1264 1 IPv4 Numbered 12 1265 2 IPv4 Unnumbered 12 1266 3 IPv6 Numbered 36 1267 4 IPv6 Unnumbered 24 1269 IP Address and Interface 1271 IPv4 addresses and interface indices are encoded in 4 octets; IPv6 1272 addresses are encoded in 16 octets. 1274 If the interface upon which the echo request message was received 1275 is numbered, then the Address Type MUST be set to IPv4 or IPv6, 1276 the IP Address MUST be set to either the LSR's Router ID or the 1277 interface address, and the Interface MUST be set to the interface 1278 address. 1280 If the interface is unnumbered, the Address Type MUST be either 1281 IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the 1282 LSR's Router ID, and the Interface MUST be set to the index 1283 assigned to the interface. 1285 Label Stack 1287 The label stack of the received echo request message. If any TTL 1288 values have been changed by this router, they SHOULD be restored. 1290 3.8. Errored TLVs 1292 The following TLV is a TLV that MAY be included in an echo reply to 1293 inform the sender of an echo request of mandatory TLVs either not 1294 supported by an implementation or parsed and found to be in error. 1296 The Value field contains the TLVs that were not understood, encoded 1297 as sub-TLVs. 1299 0 1 2 3 1300 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 1301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1302 | Type = 9 | Length | 1303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1304 | Value | 1305 . . 1306 . . 1307 . . 1308 | | 1309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1311 3.9. Reply TOS Byte TLV 1313 This TLV MAY be used by the originator of the echo request to request 1314 that an echo reply be sent with the IP header TOS byte set to the 1315 value specified in the TLV. This TLV has a length of 4 with the 1316 following value field. 1318 0 1 2 3 1319 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 1320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1321 | Reply-TOS Byte| Must Be Zero | 1322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1324 4. Theory of Operation 1326 An MPLS echo request is used to test a particular LSP. The LSP to be 1327 tested is identified by the "FEC Stack"; for example, if the LSP was 1328 set up via LDP, and is to an egress IP address of 10.1.1.1, the FEC 1329 Stack contains a single element, namely, an LDP IPv4 prefix sub-TLV 1330 with value 10.1.1.1/32. If the LSP being tested is an RSVP LSP, the 1331 FEC Stack consists of a single element that captures the RSVP Session 1332 and Sender Template that uniquely identifies the LSP. 1334 FEC Stacks can be more complex. For example, one may wish to test a 1335 VPN IPv4 prefix of 10.1/8 that is tunneled over an LDP LSP with 1336 egress 10.10.1.1. The FEC Stack would then contain two sub-TLVs, the 1337 bottom being a VPN IPv4 prefix, and the top being an LDP IPv4 prefix. 1338 If the underlying (LDP) tunnel were not known, or was considered 1339 irrelevant, the FEC Stack could be a single element with just the VPN 1340 IPv4 sub-TLV. 1342 When an MPLS echo request is received, the receiver is expected to 1343 verify that the control plane and data plane are both healthy (for 1344 the FEC Stack being pinged) and that the two planes are in sync. The 1345 procedures for this are in section 4.4 below. 1347 4.1. Dealing with Equal-Cost Multi-Path (ECMP) 1349 LSPs need not be simple point-to-point tunnels. Frequently, a single 1350 LSP may originate at several ingresses, and terminate at several 1351 egresses; this is very common with LDP LSPs. LSPs for a given FEC 1352 may also have multiple "next hops" at transit LSRs. At an ingress, 1353 there may also be several different LSPs to choose from to get to the 1354 desired endpoint. Finally, LSPs may have backup paths, detour paths, 1355 and other alternative paths to take should the primary LSP go down. 1357 To deal with the last two first: it is assumed that the LSR sourcing 1358 MPLS echo requests can force the echo request into any desired LSP, 1359 so choosing among multiple LSPs at the ingress is not an issue. The 1360 problem of probing the various flavors of backup paths that will 1361 typically not be used for forwarding data unless the primary LSP is 1362 down will not be addressed here. 1364 Since the actual LSP and path that a given packet may take may not be 1365 known a priori, it is useful if MPLS echo requests can exercise all 1366 possible paths. This, although desirable, may not be practical, 1367 because the algorithms that a given LSR uses to distribute packets 1368 over alternative paths may be proprietary. 1370 To achieve some degree of coverage of alternate paths, there is a 1371 certain latitude in choosing the destination IP address and source 1372 UDP port for an MPLS echo request. This is clearly not sufficient; 1373 in the case of traceroute, more latitude is offered by means of the 1374 Multipath Information of the Downstream Detailed Mapping TLV. This 1375 is used as follows. An ingress LSR periodically sends an MPLS 1376 traceroute message to determine whether there are multipaths for a 1377 given LSP. If so, each hop will provide some information how each of 1378 its downstream paths can be exercised. The ingress can then send 1379 MPLS echo requests that exercise these paths. If several transit 1380 LSRs have ECMP, the ingress may attempt to compose these to exercise 1381 all possible paths. However, full coverage may not be possible. 1383 4.2. Testing LSPs That Are Used to Carry MPLS Payloads 1385 To detect certain LSP breakages, it may be necessary to encapsulate 1386 an MPLS echo request packet with at least one additional label when 1387 testing LSPs that are used to carry MPLS payloads (such as LSPs used 1388 to carry L2VPN and L3VPN traffic. For example, when testing LDP or 1389 RSVP-TE LSPs, just sending an MPLS echo request packet may not detect 1390 instances where the router immediately upstream of the destination of 1391 the LSP ping may forward the MPLS echo request successfully over an 1392 interface not configured to carry MPLS payloads because of the use of 1393 penultimate hop popping. Since the receiving router has no means to 1394 differentiate whether the IP packet was sent unlabeled or implicitly 1395 labeled, the addition of labels shimmed above the MPLS echo request 1396 (using the Nil FEC) will prevent a router from forwarding such a 1397 packet out unlabeled interfaces. 1399 4.3. Sending an MPLS Echo Request 1401 An MPLS echo request is a UDP packet. The IP header is set as 1402 follows: the source IP address is a routable address of the sender; 1403 the destination IP address is a (randomly chosen) IPv4 address from 1404 the range 127/8 or IPv6 address from the range 1405 0:0:0:0:0:FFFF:7F00/104. The IP TTL is set to 1. The source UDP 1406 port is chosen by the sender; the destination UDP port is set to 3503 1407 (assigned by IANA for MPLS echo requests). The Router Alert IP 1408 option of value 0x0 [RFC2113] for IPv4 or value 69 [RFC7506] for IPv6 1409 MUST be set in IP header. 1411 An MPLS echo request is sent with a label stack corresponding to the 1412 FEC Stack being tested. Note that further labels could be applied 1413 if, for example, the normal route to the topmost FEC in the stack is 1414 via a Traffic Engineered Tunnel [RFC3209]. If all of the FECs in the 1415 stack correspond to Implicit Null labels, the MPLS echo request is 1416 considered unlabeled even if further labels will be applied in 1417 sending the packet. 1419 If the echo request is labeled, one MAY (depending on what is being 1420 pinged) set the TTL of the innermost label to 1, to prevent the ping 1421 request going farther than it should. Examples of where this SHOULD 1422 be done include pinging a VPN IPv4 or IPv6 prefix, an L2 VPN endpoint 1423 or a pseudowire. Preventing the ping request from going too far can 1424 also be accomplished by inserting a Router Alert label above this 1425 label; however, this may lead to the undesired side effect that MPLS 1426 echo requests take a different data path than actual data. For more 1427 information on how these mechanisms can be used for pseudowire 1428 connectivity verification, see [RFC5085]. 1430 In "ping" mode (end-to-end connectivity check), the TTL in the 1431 outermost label is set to 255. In "traceroute" mode (fault isolation 1432 mode), the TTL is set successively to 1, 2, and so on. 1434 The sender chooses a Sender's Handle and a Sequence Number. When 1435 sending subsequent MPLS echo requests, the sender SHOULD increment 1436 the Sequence Number by 1. However, a sender MAY choose to send a 1437 group of echo requests with the same Sequence Number to improve the 1438 chance of arrival of at least one packet with that Sequence Number. 1440 The TimeStamp Sent is set to the time-of-day in NTP format that the 1441 echo request is sent. The TimeStamp Received is set to zero. 1443 An MPLS echo request MUST have an FEC Stack TLV. Also, the Reply 1444 Mode must be set to the desired reply mode; the Return Code and 1445 Subcode are set to zero. In the "traceroute" mode, the echo request 1446 SHOULD include a Downstream Detailed Mapping TLV. 1448 4.4. Receiving an MPLS Echo Request 1450 Sending an MPLS echo request to the control plane is triggered by one 1451 of the following packet processing exceptions: Router Alert option, 1452 IP TTL expiration, MPLS TTL expiration, MPLS Router Alert label, or 1453 the destination address in the 127/8 address range. The control 1454 plane further identifies it by UDP destination port 3503. 1456 For reporting purposes the bottom of stack is considered to be stack- 1457 depth of 1. This is to establish an absolute reference for the case 1458 where the actual stack may have more labels than there are FECs in 1459 the Target FEC Stack. 1461 Furthermore, in all the error codes listed in this document, a stack- 1462 depth of 0 means "no value specified". This allows compatibility 1463 with existing implementations that do not use the Return Subcode 1464 field. 1466 An LSR X that receives an MPLS echo request then processes it as 1467 follows. 1469 1. General packet sanity is verified. If the packet is not well- 1470 formed, LSR X SHOULD send an MPLS Echo Reply with the Return Code 1471 set to "Malformed echo request received" and the Subcode to zero. 1472 If there are any TLVs not marked as "Ignore" that LSR X does not 1473 understand, LSR X SHOULD send an MPLS "TLV not understood" (as 1474 appropriate), and the Subcode set to zero. In the latter case, 1475 the misunderstood TLVs (only) are included as sub-TLVs in an 1476 Errored TLVs TLV in the reply. The header fields Sender's 1477 Handle, Sequence Number, and Timestamp Sent are not examined, but 1478 are included in the MPLS echo reply message. 1480 The algorithm uses the following variables and identifiers: 1482 Interface-I: the interface on which the MPLS echo request was 1483 received. 1485 Stack-R: the label stack on the packet as it was received. 1487 Stack-D: the label stack carried in the "Label Stack sub- 1488 TLV" in Downstream Detailed Mapping TLV (not 1489 always present) 1491 Label-L: the label from the actual stack currently being 1492 examined. Requires no initialization. 1494 Label-stack-depth: the depth of label being verified. Initialized 1495 to the number of labels in the received label 1496 stack S. 1498 FEC-stack-depth: depth of the FEC in the Target FEC Stack that 1499 should be used to verify the current actual 1500 label. Requires no initialization. 1502 Best-return-code: contains the return code for the echo reply 1503 packet as currently best known. As the algorithm 1504 progresses, this code may change depending on the 1505 results of further checks that it performs. 1507 Best-rtn-subcode: similar to Best-return-code, but for the Echo 1508 Reply Subcode. 1510 FEC-status: result value returned by the FEC Checking 1511 algorithm described in section 4.4.1. 1513 /* Save receive context information */ 1515 2. If the echo request is good, LSR X stores the interface over 1516 which the echo was received in Interface-I, and the label stack 1517 with which it came in Stack-R. 1519 /* The rest of the algorithm iterates over the labels in Stack-R, 1520 verifies validity of label values, reports associated label switching 1521 operations (for traceroute), verifies correspondence between the 1522 Stack-R and the Target FEC Stack description in the body of the echo 1523 request, and reports any errors. */ 1524 /* The algorithm iterates as follows. */ 1526 3. Label Validation: 1528 If Label-stack-depth is 0 { 1530 /* The LSR needs to report its being a tail-end for the LSP */ 1532 Set FEC-stack-depth to 1, set Label-L to 3 (Implicit Null). 1533 Set Best-return-code to 3 ("Replying router is an egress for 1534 the FEC at stack depth"), set Best-rtn-subcode to the value of 1535 FEC-stack-depth (1) and go to step 5 (Egress Processing). 1537 } 1539 /* This step assumes there is always an entry for well-known label 1540 values */ 1542 Set Label-L to the value extracted from Stack-R at depth Label- 1543 stack-depth. Look up Label-L in the Incoming Label Map (ILM) to 1544 determine if the label has been allocated and an operation is 1545 associated with it. 1547 If there is no entry for L { 1549 /* Indicates a temporary or permanent label synchronization 1550 problem the LSR needs to report an error */ 1552 Set Best-return-code to 11 ("No label entry at stack-depth") 1553 and Best-rtn-subcode to Label-stack-depth. Go to step 7 (Send 1554 Reply Packet). 1556 } 1558 Else { 1560 Retrieve the associated label operation from the corresponding 1561 NHLFE and proceed to step 4 (Label Operation check). 1563 } 1565 4. Label Operation Check 1567 If the label operation is "Pop and Continue Processing" { 1569 /* Includes Explicit Null and Router Alert label cases */ 1570 Iterate to the next label by decrementing Label-stack-depth and 1571 loop back to step 3 (Label Validation). 1573 } 1575 If the label operation is "Swap or Pop and Switch based on Popped 1576 Label" { 1578 Set Best-return-code to 8 ("Label switched at stack-depth") and 1579 Best-rtn-subcode to Label-stack-depth to report transit 1580 switching. 1582 If a Downstream Detailed Mapping TLV is present in the received 1583 echo request { 1585 If the IP address in the TLV is 127.0.0.1 or 0::1 { 1587 Set Best-return-code to 6 ("Upstream Interface Index 1588 Unknown"). An Interface and Label Stack TLV SHOULD be 1589 included in the reply and filled with Interface-I and 1590 Stack-R. 1592 } 1594 Else { 1596 Verify that the IP address, interface address, and label 1597 stack in the Downstream Detailed Mapping TLV match 1598 Interface-I and Stack-R. If there is a mismatch, set 1599 Best-return-code to 5, "Downstream Mapping Mismatch". An 1600 Interface and Label Stack TLV SHOULD be included in the 1601 reply and filled in based on Interface-I and Stack-R. Go 1602 to step 7 (Send Reply Packet). 1604 } 1606 } 1608 For each available downstream ECMP path { 1610 Retrieve output interface from the NHLFE entry. 1612 /* Note: this return code is set even if Label-stack-depth 1613 is one */ 1615 If the output interface is not MPLS enabled { 1616 Set Best-return-code to Return Code 9, "Label switched 1617 but no MPLS forwarding at stack-depth" and set Best-rtn- 1618 subcode to Label-stack-depth and goto Send_Reply_Packet. 1620 } 1622 If a Downstream Detailed Mapping TLV is present { 1624 A Downstream Detailed Mapping TLV SHOULD be included in 1625 the echo reply (see Section 3.4) filled in with 1626 information about the current ECMP path. 1628 } 1630 } 1632 If no Downstream Detailed Mapping TLV is present, or the 1633 Downstream IP Address is set to the ALLROUTERS multicast 1634 address, go to step 7 (Send Reply Packet). 1636 If the "Validate FEC Stack" flag is not set and the LSR is not 1637 configured to perform FEC checking by default, go to step 7 1638 (Send Reply Packet). 1640 /* Validate the Target FEC Stack in the received echo request. 1642 First determine FEC-stack-depth from the Downstream Detailed 1643 Mapping TLV. This is done by walking through Stack-D (the 1644 Downstream labels) from the bottom, decrementing the number of 1645 labels for each non-Implicit Null label, while incrementing 1646 FEC-stack-depth for each label. If the Downstream Detailed 1647 Mapping TLV contains one or more Implicit Null labels, FEC- 1648 stack-depth may be greater than Label-stack-depth. To be 1649 consistent with the above stack-depths, the bottom is 1650 considered to be entry 1. 1651 */ 1653 Set FEC-stack-depth to 0. Set i to Label-stack-depth. 1655 While (i > 0 ) do { 1657 ++FEC-stack-depth. 1658 if Stack-D[FEC-stack-depth] != 3 (Implicit Null) 1659 --i. 1660 } 1662 If the number of FECs in the FEC stack is greater than or equal 1663 to FEC-stack-depth { 1664 Perform the FEC Checking procedure (see subsection 4.4.1 1665 below). 1667 If FEC-status is 2, set Best-return-code to 10 ("Mapping for 1668 this FEC is not the given label at stack-depth"). 1670 If the return code is 1, set Best-return-code to FEC-return- 1671 code and Best-rtn-subcode to FEC-stack-depth. 1672 } 1674 Go to step 7 (Send Reply Packet). 1675 } 1677 5. Egress Processing: 1679 /* These steps are performed by the LSR that identified itself as 1680 the tail-end LSR for an LSP. */ 1682 If received echo request contains no Downstream Detailed Mapping 1683 TLV, or the Downstream IP Address is set to 127.0.0.1 or 0::1 go 1684 to step 6 (Egress FEC Validation). 1686 Verify that the IP address, interface address, and label stack in 1687 the Downstream Detailed Mapping TLV match Interface-I and Stack-R. 1688 If not, set Best-return-code to 5, "Downstream Mapping Mis-match". 1689 A Received Interface and Label Stack TLV SHOULD be created for the 1690 echo response packet. Go to step 7 (Send Reply Packet). 1692 6. Egress FEC Validation: 1694 /* This is a loop for all entries in the Target FEC Stack starting 1695 with FEC-stack-depth. */ 1697 Perform FEC checking by following the algorithm described in 1698 subsection 4.4.1 for Label-L and the FEC at FEC-stack-depth. 1700 Set Best-return-code to FEC-code and Best-rtn-subcode to the value 1701 in FEC-stack-depth. 1703 If FEC-status (the result of the check) is 1, 1704 go to step 7 (Send Reply Packet). 1706 /* Iterate to the next FEC entry */ 1708 ++FEC-stack-depth. 1709 If FEC-stack-depth > the number of FECs in the FEC-stack, 1710 go to step 7 (Send Reply Packet). 1712 If FEC-status is 0 { 1714 ++Label-stack-depth. 1715 If Label-stack-depth > the number of labels in Stack-R, 1716 Go to step 7 (Send Reply Packet). 1718 Label-L = extracted label from Stack-R at depth 1719 Label-stack-depth. 1720 Loop back to step 6 (Egress FEC Validation). 1721 } 1723 7. Send Reply Packet: 1725 Send an MPLS echo reply with a Return Code of Best-return-code, 1726 and a Return Subcode of Best-rtn-subcode. Include any TLVs 1727 created during the above process. The procedures for sending the 1728 echo reply are found in subsection 4.5. 1730 4.4.1. FEC Validation 1732 /* This subsection describes validation of an FEC entry within the 1733 Target FEC Stack and accepts an FEC, Label-L, and Interface-I. The 1734 algorithm performs the following steps. */ 1736 1. Two return values, FEC-status and FEC-return-code, are 1737 initialized to 0. 1739 2. If the FEC is the Nil FEC { 1741 If Label-L is either Explicit_Null or Router_Alert, return. 1743 Else { 1745 Set FEC-return-code to 10 ("Mapping for this FEC is not the 1746 given label at stack-depth"). 1747 Set FEC-status to 1 1748 Return. 1749 } 1751 } 1753 3. Check the FEC label mapping that describes how traffic received 1754 on the LSP is further switched or which application it is 1755 associated with. If no mapping exists, set FEC-return-code to 1756 Return 4, "Replying router has no mapping for the FEC at stack- 1757 depth". Set FEC-status to 1. Return. 1759 4. If the label mapping for FEC is Implicit Null, set FEC-status to 1760 2 and proceed to step 5. Otherwise, if the label mapping for FEC 1761 is Label-L, proceed to step 5. Otherwise, set FEC-return-code to 1762 10 ("Mapping for this FEC is not the given label at stack- 1763 depth"), set FEC-status to 1, and return. 1765 5. This is a protocol check. Check what protocol would be used to 1766 advertise FEC. If it can be determined that no protocol 1767 associated with Interface-I would have advertised an FEC of that 1768 FEC-Type, set FEC-return-code to 12 ("Protocol not associated 1769 with interface at FEC stack-depth"). Set FEC-status to 1. 1771 6. Return. 1773 4.5. Sending an MPLS Echo Reply 1775 An MPLS echo reply is a UDP packet. It MUST ONLY be sent in response 1776 to an MPLS echo request. The source IP address is a routable address 1777 of the replier; the source port is the well-known UDP port for LSP 1778 ping. The destination IP address and UDP port are copied from the 1779 source IP address and UDP port of the echo request. The IP TTL is 1780 set to 255. If the Reply Mode in the echo request is "Reply via an 1781 IPv4 UDP packet with Router Alert", then the IP header MUST contain 1782 the Router Alert IP option of value 0x0 [RFC2113] for IPv4 or 69 1783 [RFC7506] for IPv6. If the reply is sent over an LSP, the topmost 1784 label MUST in this case be the Router Alert label (1) (see 1785 [RFC3032]). 1787 The format of the echo reply is the same as the echo request. The 1788 Sender's Handle, the Sequence Number, and TimeStamp Sent are copied 1789 from the echo request; the TimeStamp Received is set to the time-of- 1790 day that the echo request is received (note that this information is 1791 most useful if the time-of-day clocks on the requester and the 1792 replier are synchronized). The FEC Stack TLV from the echo request 1793 MAY be copied to the reply. 1795 The replier MUST fill in the Return Code and Subcode, as determined 1796 in the previous subsection. 1798 If the echo request contains a Pad TLV, the replier MUST interpret 1799 the first octet for instructions regarding how to reply. 1801 If the replying router is the destination of the FEC, then Downstream 1802 Detailed Mapping TLVs SHOULD NOT be included in the echo reply. 1804 If the echo request contains a Downstream Detailed Mapping TLV, and 1805 the replying router is not the destination of the FEC, the replier 1806 SHOULD compute its downstream routers and corresponding labels for 1807 the incoming label, and add Downstream Detailed Mapping TLVs for each 1808 one to the echo reply it sends back. 1810 If the Downstream Detailed Mapping TLV contains Multipath Information 1811 requiring more processing than the receiving router is willing to 1812 perform, the responding router MAY choose to respond with only a 1813 subset of multipaths contained in the echo request Downstream 1814 Detailed Mapping. (Note: The originator of the echo request MAY send 1815 another echo request with the Multipath Information that was not 1816 included in the reply.) 1818 Except in the case of Reply Mode 4, "Reply via application level 1819 control channel", echo replies are always sent in the context of the 1820 IP/MPLS network. 1822 4.6. Receiving an MPLS Echo Reply 1824 An LSR X should only receive an MPLS echo reply in response to an 1825 MPLS echo request that it sent. Thus, on receipt of an MPLS echo 1826 reply, X should parse the packet to ensure that it is well-formed, 1827 then attempt to match up the echo reply with an echo request that it 1828 had previously sent, using the destination UDP port and the Sender's 1829 Handle. If no match is found, then X jettisons the echo reply; 1830 otherwise, it checks the Sequence Number to see if it matches. 1832 If the echo reply contains Downstream Detailed Mappings, and X wishes 1833 to traceroute further, it SHOULD copy the Downstream Detailed 1834 Mapping(s) into its next echo request(s) (with TTL incremented by 1835 one). 1837 4.7. Issue with VPN IPv4 and IPv6 Prefixes 1839 Typically, an LSP ping for a VPN IPv4 prefix or VPN IPv6 prefix is 1840 sent with a label stack of depth greater than 1, with the innermost 1841 label having a TTL of 1. This is to terminate the ping at the egress 1842 PE, before it gets sent to the customer device. However, under 1843 certain circumstances, the label stack can shrink to a single label 1844 before the ping hits the egress PE; this will result in the ping 1845 terminating prematurely. One such scenario is a multi-AS Carrier's 1846 Carrier VPN. 1848 To get around this problem, one approach is for the LSR that receives 1849 such a ping to realize that the ping terminated prematurely, and send 1850 back error code 13. In that case, the initiating LSR can retry the 1851 ping after incrementing the TTL on the VPN label. In this fashion, 1852 the ingress LSR will sequentially try TTL values until it finds one 1853 that allows the VPN ping to reach the egress PE. 1855 4.8. Non-compliant Routers 1857 If the egress for the FEC Stack being pinged does not support MPLS 1858 ping, then no reply will be sent, resulting in possible "false 1859 negatives". If in "traceroute" mode, a transit LSR does not support 1860 LSP ping, then no reply will be forthcoming from that LSR for some 1861 TTL, say, n. The LSR originating the echo request SHOULD try sending 1862 the echo request with TTL=n+1, n+2, ..., n+k to probe LSRs further 1863 down the path. In such a case, the echo request for TTL > n SHOULD 1864 be sent with Downstream Detailed Mapping TLV "Downstream IP Address" 1865 field set to the ALLROUTERs multicast address until a reply is 1866 received with a Downstream Detailed Mapping TLV. The label stack TLV 1867 MAY be omitted from the Downstream Detailed Mapping TLV. 1868 Furthermore, the "Validate FEC Stack" flag SHOULD NOT be set until an 1869 echo reply packet with a Downstream Detailed Mapping TLV is received. 1871 5. Security Considerations 1873 Overall, the security needs for LSP ping are similar to those of ICMP 1874 ping. 1876 There are at least three approaches to attacking LSRs using the 1877 mechanisms defined here. One is a Denial-of-Service attack, by 1878 sending MPLS echo requests/replies to LSRs and thereby increasing 1879 their workload. The second is obfuscating the state of the MPLS data 1880 plane liveness by spoofing, hijacking, replaying, or otherwise 1881 tampering with MPLS echo requests and replies. The third is an 1882 unauthorized source using an LSP ping to obtain information about the 1883 network. 1885 To avoid potential Denial-of-Service attacks, it is RECOMMENDED that 1886 implementations regulate the LSP ping traffic going to the control 1887 plane. A rate limiter SHOULD be applied to the well-known UDP port 1888 defined below. 1890 Unsophisticated replay and spoofing attacks involving faking or 1891 replaying MPLS echo reply messages are unlikely to be effective. 1892 These replies would have to match the Sender's Handle and Sequence 1893 Number of an outstanding MPLS echo request message. A non-matching 1894 replay would be discarded as the sequence has moved on, thus a spoof 1895 has only a small window of opportunity. However, to provide a 1896 stronger defense, an implementation MAY also validate the TimeStamp 1897 Sent by requiring an exact match on this field. 1899 To protect against unauthorized sources using MPLS echo request 1900 messages to obtain network information, it is RECOMMENDED that 1901 implementations provide a means of checking the source addresses of 1902 MPLS echo request messages against an access list before accepting 1903 the message. 1905 It is not clear how to prevent hijacking (non-delivery) of echo 1906 requests or replies; however, if these messages are indeed hijacked, 1907 LSP ping will report that the data plane is not working as it should. 1909 It does not seem vital (at this point) to secure the data carried in 1910 MPLS echo requests and replies, although knowledge of the state of 1911 the MPLS data plane may be considered confidential by some. 1912 Implementations SHOULD, however, provide a means of filtering the 1913 addresses to which echo reply messages may be sent. 1915 Although this document makes special use of 127/8 address, these are 1916 used only in conjunction with the UDP port 3503. Furthermore, these 1917 packets are only processed by routers. All other hosts MUST treat 1918 all packets with a destination address in the range 127/8 in 1919 accordance to RFC 1122. Any packet received by a router with a 1920 destination address in the range 127/8 without a destination UDP port 1921 of 3503 MUST be treated in accordance to RFC 1812. In particular, 1922 the default behavior is to treat packets destined to a 127/8 address 1923 as "martians". 1925 6. IANA Considerations 1927 The TCP and UDP port number 3503 has been allocated by IANA for LSP 1928 echo requests and replies. 1930 The following sections detail the new name spaces to be managed by 1931 IANA. For each of these name spaces, the space is divided into 1932 assignment ranges; the following terms are used in describing the 1933 procedures by which IANA allocates values: "Standards Action" (as 1934 defined in [RFC5226]), "Specification Required", and "Vendor Private 1935 Use". 1937 Values from "Specification Required" ranges MUST be registered with 1938 IANA. The request MUST be made via an Experimental RFC that 1939 describes the format and procedures for using the code point; the 1940 actual assignment is made during the IANA actions for the RFC. 1942 Values from "Vendor Private" ranges MUST NOT be registered with IANA; 1943 however, the message MUST contain an enterprise code as registered 1944 with the IANA SMI Private Network Management Private Enterprise 1945 Numbers. For each name space that has a Vendor Private range, it 1946 must be specified where exactly the SMI Private Enterprise Number 1947 resides; see below for examples. In this way, several enterprises 1948 (vendors) can use the same code point without fear of collision. 1950 6.1. Message Types, Reply Modes, Return Codes 1952 The IANA has created and will maintain registries for Message Types, 1953 Reply Modes, and Return Codes. Each of these can take values in the 1954 range 0-255. Assignments in the range 0-191 are via Standards 1955 Action; assignments in the range 192-251 are made via "Specification 1956 Required"; values in the range 252-255 are for Vendor Private Use, 1957 and MUST NOT be allocated. 1959 If any of these fields fall in the Vendor Private range, a top-level 1960 Vendor Enterprise Number TLV MUST be present in the message. 1962 Message Types defined in this document are the following: 1964 Value Meaning 1965 ----- ------- 1966 1 MPLS echo request 1967 2 MPLS echo reply 1969 Reply Modes defined in this document are the following: 1971 Value Meaning 1972 ----- ------- 1973 1 Do not reply 1974 2 Reply via an IPv4/IPv6 UDP packet 1975 3 Reply via an IPv4/IPv6 UDP packet with Router Alert 1976 4 Reply via application level control channel 1978 Return Codes defined in this document are listed in section 3.1. 1980 6.2. TLVs 1982 The IANA has created and will maintain a registry for the Type field 1983 of top-level TLVs as well as for any associated sub-TLVs. Note the 1984 meaning of a sub-TLV is scoped by the TLV. The number spaces for the 1985 sub-TLVs of various TLVs are independent. 1987 The valid range for TLVs and sub-TLVs is 0-65535. Assignments in the 1988 range 0-16383 and 32768-49161 are made via Standards Action as 1989 defined in [RFC5226]; assignments in the range 16384-31743 and 1990 49162-64511 are made via "Specification Required" as defined above; 1991 values in the range 31744-32767 and 64512-65535 are for Vendor 1992 Private Use, and MUST NOT be allocated. 1994 If a TLV or sub-TLV has a Type that falls in the range for Vendor 1995 Private Use, the Length MUST be at least 4, and the first four octets 1996 MUST be that vendor's SMI Private Enterprise Number, in network octet 1997 order. The rest of the Value field is private to the vendor. 1999 TLVs and sub-TLVs defined in this document are the following: 2001 Type Sub-Type Value Field 2002 ---- -------- ----------- 2003 1 Target FEC Stack 2004 1 LDP IPv4 prefix 2005 2 LDP IPv6 prefix 2006 3 RSVP IPv4 LSP 2007 4 RSVP IPv6 LSP 2008 5 Not Assigned 2009 6 VPN IPv4 prefix 2010 7 VPN IPv6 prefix 2011 8 L2 VPN endpoint 2012 9 "FEC 128" Pseudowire - IPv4 (Deprecated) 2013 10 "FEC 128" Pseudowire - IPv4 2014 11 "FEC 129" Pseudowire - IPv4 2015 12 BGP labeled IPv4 prefix 2016 13 BGP labeled IPv6 prefix 2017 14 Generic IPv4 prefix 2018 15 Generic IPv6 prefix 2019 16 Nil FEC 2020 24 "FEC 128" Pseudowire - IPv6 2021 25 "FEC 129" Pseudowire - IPv6 2022 2 Downstream Mapping 2023 3 Pad 2024 4 Not Assigned 2025 5 Vendor Enterprise Number 2026 6 Not Assigned 2027 7 Interface and Label Stack 2028 8 Not Assigned 2029 9 Errored TLVs 2030 Any value The TLV not understood 2031 10 Reply TOS Byte 2033 7. Acknowledgements 2035 The original acknowledgements from RFC 4379 state the following: 2037 This document is the outcome of many discussions among many 2038 people, including Manoj Leelanivas, Paul Traina, Yakov Rekhter, 2039 Der-Hwa Gan, Brook Bailey, Eric Rosen, Ina Minei, Shivani 2040 Aggarwal, and Vanson Lim. 2042 The description of the Multipath Information sub-field of the 2043 Downstream Mapping TLV was adapted from text suggested by Curtis 2044 Villamizar. 2046 We would like to thank Loa Andersson for motivating the advancement 2047 of this bis specification. 2049 We also would like to thank Alexander Vainshtein, Yimin Shen, Curtis 2050 Villamizar, David Allan for their review and comments. 2052 8. References 2054 8.1. Normative References 2056 [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - 2057 Communication Layers", STD 3, RFC 1122, 2058 DOI 10.17487/RFC1122, October 1989, 2059 . 2061 [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", 2062 RFC 1812, DOI 10.17487/RFC1812, June 1995, 2063 . 2065 [RFC2113] Katz, D., "IP Router Alert Option", RFC 2113, 2066 DOI 10.17487/RFC2113, February 1997, 2067 . 2069 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2070 Requirement Levels", BCP 14, RFC 2119, 2071 DOI 10.17487/RFC2119, March 1997, 2072 . 2074 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 2075 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 2076 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, 2077 . 2079 [RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual 2080 Private Network (VPN) Terminology", RFC 4026, 2081 DOI 10.17487/RFC4026, March 2005, 2082 . 2084 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 2085 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 2086 DOI 10.17487/RFC4271, January 2006, 2087 . 2089 [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol 2090 Label Switched (MPLS) Data Plane Failures", RFC 4379, 2091 DOI 10.17487/RFC4379, February 2006, 2092 . 2094 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2095 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2096 DOI 10.17487/RFC5226, May 2008, 2097 . 2099 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 2100 "Network Time Protocol Version 4: Protocol and Algorithms 2101 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 2102 . 2104 [RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for 2105 Performing Label Switched Path Ping (LSP Ping) over MPLS 2106 Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011, 2107 . 2109 [RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert 2110 Option for MPLS Operations, Administration, and 2111 Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April 2112 2015, . 2114 8.2. Informative References 2116 [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, 2117 RFC 792, DOI 10.17487/RFC0792, September 1981, 2118 . 2120 [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in 2121 BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001, 2122 . 2124 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 2125 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 2126 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 2127 . 2129 [RFC4365] Rosen, E., "Applicability Statement for BGP/MPLS IP 2130 Virtual Private Networks (VPNs)", RFC 4365, 2131 DOI 10.17487/RFC4365, February 2006, 2132 . 2134 [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and 2135 G. Heron, "Pseudowire Setup and Maintenance Using the 2136 Label Distribution Protocol (LDP)", RFC 4447, 2137 DOI 10.17487/RFC4447, April 2006, 2138 . 2140 [RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private 2141 LAN Service (VPLS) Using BGP for Auto-Discovery and 2142 Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007, 2143 . 2145 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 2146 "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, 2147 October 2007, . 2149 [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual 2150 Circuit Connectivity Verification (VCCV): A Control 2151 Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085, 2152 December 2007, . 2154 Appendix A. Deprecated TLVs 2156 A.1. FEC 128 Pseudowire 2158 FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID 2159 (Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero 2160 32-bit connection ID. The PW Type is a 15-bit number indicating the 2161 encapsulation type. It is carried right justified in the field below 2162 termed encapsulation type with the high-order bit set to zero. Both 2163 of these fields are treated in this protocol as opaque values. 2165 When an FEC 128 is encoded in a label stack, the following format is 2166 used. The value field consists of the remote PE IPv4 address (the 2167 destination address of the targeted LDP session), the PW ID, and the 2168 encapsulation type as follows: 2170 0 1 2 3 2171 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 2172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2173 | Remote PE IPv4 Address | 2174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2175 | PW ID | 2176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2177 | PW Type | Must Be Zero | 2178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2180 This FEC is deprecated and is retained only for backward 2181 compatibility. Implementations of LSP ping SHOULD accept and process 2182 this TLV, but SHOULD send LSP ping echo requests with the new TLV 2183 (see next section), unless explicitly configured to use the old TLV. 2185 An LSR receiving this TLV SHOULD use the source IP address of the LSP 2186 echo request to infer the sender's PE address. 2188 A.2. Downstream Mapping(DSMAP) 2190 The Downstream Mapping object is a TLV that MAY be included in an 2191 echo request message. Only one Downstream Mapping object may appear 2192 in an echo request. The presence of a Downstream Mapping object is a 2193 request that Downstream Mapping objects be included in the echo 2194 reply. If the replying router is the destination of the FEC, then a 2195 Downstream Mapping TLV SHOULD NOT be included in the echo reply. 2196 Otherwise the replying router SHOULD include a Downstream Mapping 2197 object for each interface over which this FEC could be forwarded. 2198 For a more precise definition of the notion of "downstream", see 2199 section 3.3.2, "Downstream Router and Interface". 2201 The Length is K + M + 4*N octets, where M is the Multipath Length, 2202 and N is the number of Downstream Labels. Values for K are found in 2203 the description of Address Type below. The Value field of a 2204 Downstream Mapping has the following format: 2206 0 1 2 3 2207 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 2208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2209 | MTU | Address Type | DS Flags | 2210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2211 | Downstream IP Address (4 or 16 octets) | 2212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2213 | Downstream Interface Address (4 or 16 octets) | 2214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2215 | Multipath Type| Depth Limit | Multipath Length | 2216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2217 . . 2218 . (Multipath Information) . 2219 . . 2220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2221 | Downstream Label | Protocol | 2222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2223 . . 2224 . . 2225 . . 2226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2227 | Downstream Label | Protocol | 2228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2230 Maximum Transmission Unit (MTU) 2232 The MTU is the size in octets of the largest MPLS frame (including 2233 label stack) that fits on the interface to the Downstream LSR. 2235 Address Type 2236 The Address Type indicates if the interface is numbered or 2237 unnumbered. It also determines the length of the Downstream IP 2238 Address and Downstream Interface fields. The resulting total for 2239 the initial part of the TLV is listed in the table below as "K 2240 Octets". The Address Type is set to one of the following values: 2242 Type # Address Type K Octets 2243 ------ ------------ -------- 2244 1 IPv4 Numbered 16 2245 2 IPv4 Unnumbered 16 2246 3 IPv6 Numbered 40 2247 4 IPv6 Unnumbered 28 2249 DS Flags 2251 The DS Flags field is a bit vector with the following format: 2253 0 1 2 3 4 5 6 7 2254 +-+-+-+-+-+-+-+-+ 2255 | Rsvd(MBZ) |I|N| 2256 +-+-+-+-+-+-+-+-+ 2258 Two flags are defined currently, I and N. The remaining flags MUST 2259 be set to zero when sending and ignored on receipt. 2261 Flag Name and Meaning 2262 ---- ---------------- 2263 I Interface and Label Stack Object Request 2265 When this flag is set, it indicates that the replying 2266 router SHOULD include an Interface and Label Stack 2267 Object in the echo reply message. 2269 N Treat as a Non-IP Packet 2271 Echo request messages will be used to diagnose non-IP 2272 flows. However, these messages are carried in IP 2273 packets. For a router that alters its ECMP algorithm 2274 based on the FEC or deep packet examination, this flag 2275 requests that the router treat this as it would if the 2276 determination of an IP payload had failed. 2278 Downstream IP Address and Downstream Interface Address 2280 IPv4 addresses and interface indices are encoded in 4 octets; IPv6 2281 addresses are encoded in 16 octets. 2283 If the interface to the downstream LSR is numbered, then the 2284 Address Type MUST be set to IPv4 or IPv6, the Downstream IP 2285 Address MUST be set to either the downstream LSR's Router ID or 2286 the interface address of the downstream LSR, and the Downstream 2287 Interface Address MUST be set to the downstream LSR's interface 2288 address. 2290 If the interface to the downstream LSR is unnumbered, the Address 2291 Type MUST be IPv4 Unnumbered or IPv6 Unnumbered, the Downstream IP 2292 Address MUST be the downstream LSR's Router ID, and the Downstream 2293 Interface Address MUST be set to the index assigned by the 2294 upstream LSR to the interface. 2296 If an LSR does not know the IP address of its neighbor, then it 2297 MUST set the Address Type to either IPv4 Unnumbered or IPv6 2298 Unnumbered. For IPv4, it must set the Downstream IP Address to 2299 127.0.0.1; for IPv6 the address is set to 0::1. In both cases, 2300 the interface index MUST be set to 0. If an LSR receives an Echo 2301 Request packet with either of these addresses in the Downstream IP 2302 Address field, this indicates that it MUST bypass interface 2303 verification but continue with label validation. 2305 If the originator of an Echo Request packet wishes to obtain 2306 Downstream Mapping information but does not know the expected 2307 label stack, then it SHOULD set the Address Type to either IPv4 2308 Unnumbered or IPv6 Unnumbered. For IPv4, it MUST set the 2309 Downstream IP Address to 224.0.0.2; for IPv6 the address MUST be 2310 set to FF02::2. In both cases, the interface index MUST be set to 2311 0. If an LSR receives an Echo Request packet with the all-routers 2312 multicast address, then this indicates that it MUST bypass both 2313 interface and label stack validation, but return Downstream 2314 Mapping TLVs using the information provided. 2316 Multipath Type 2318 The following Multipath Types are defined: 2320 Key Type Multipath Information 2321 --- ---------------- --------------------- 2322 0 no multipath Empty (Multipath Length = 0) 2323 2 IP address IP addresses 2324 4 IP address range low/high address pairs 2325 8 Bit-masked IP IP address prefix and bit mask 2326 address set 2327 9 Bit-masked label set Label prefix and bit mask 2329 Type 0 indicates that all packets will be forwarded out this one 2330 interface. 2332 Types 2, 4, 8, and 9 specify that the supplied Multipath 2333 Information will serve to exercise this path. 2335 Depth Limit 2337 The Depth Limit is applicable only to a label stack and is the 2338 maximum number of labels considered in the hash; this SHOULD be 2339 set to zero if unspecified or unlimited. 2341 Multipath Length 2343 The length in octets of the Multipath Information. 2345 Multipath Information 2347 Address or label values encoded according to the Multipath Type. 2348 See the next section below for encoding details. 2350 Downstream Label(s) 2352 The set of labels in the label stack as it would have appeared if 2353 this router were forwarding the packet through this interface. 2354 Any Implicit Null labels are explicitly included. Labels are 2355 treated as numbers, i.e., they are right justified in the field. 2357 A Downstream Label is 24 bits, in the same format as an MPLS label 2358 minus the TTL field, i.e., the MSBit of the label is bit 0, the 2359 LSBit is bit 19, the Traffic Class (TC) bits are bits 20-22, and 2360 bit 23 is the S bit. The replying router SHOULD fill in the TC 2361 and S bits; the LSR receiving the echo reply MAY choose to ignore 2362 these bits. Protocol 2364 The Protocol is taken from the following table: 2366 Protocol # Signaling Protocol 2367 ---------- ------------------ 2368 0 Unknown 2369 1 Static 2370 2 BGP 2371 3 LDP 2372 4 RSVP-TE 2374 Authors' Addresses 2376 Kireeti Kompella 2377 Juniper Networks, Inc. 2379 Email: kireeti.kompella@gmail.com 2380 Carlos Pignataro 2381 Cisco Systems, Inc. 2383 Email: cpignata@cisco.com 2385 Nagendra Kumar 2386 Cisco Systems, Inc. 2388 Email: naikumar@cisco.com 2390 Sam Aldrin 2391 Google 2393 Email: aldrin.ietf@gmail.com 2395 Mach(Guoyi) Chen 2396 Huawei 2398 Email: mach.chen@huawei.com