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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-23) exists of draft-ietf-ospf-ospfv3-lsa-extend-09 -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE.1588.2008' -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group G. Mirsky 3 Internet-Draft S. Ruffini 4 Intended status: Standards Track E. Gray 5 Expires: July 31, 2016 Ericsson 6 J. Drake 7 Juniper Networks 8 S. Bryant 9 Cisco Systems 10 A. Vainshtein 11 ECI Telecom 12 January 28, 2016 14 Residence Time Measurement in MPLS network 15 draft-ietf-mpls-residence-time-01 17 Abstract 19 This document specifies G-ACh based Residence Time Measurement and 20 how it can be used by time synchronization protocols being 21 transported over MPLS domain. 23 Residence time is the variable part of propagation delay of timing 24 and synchronization messages and knowing what this delay is for each 25 message allows for a more accurate determination of the delay to be 26 taken into account in applying the value included in a PTP event 27 message. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on July 31, 2016. 46 Copyright Notice 48 Copyright (c) 2016 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 1.1. Conventions used in this document . . . . . . . . . . . . 3 65 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 66 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 4 67 2. Residence Time Measurement . . . . . . . . . . . . . . . . . 4 68 3. G-ACh for Residence Time Measurement . . . . . . . . . . . . 5 69 3.1. PTP Packet Sub-TLV . . . . . . . . . . . . . . . . . . . 6 70 4. Control Plane Theory of Operation . . . . . . . . . . . . . . 7 71 4.1. RTM Capability . . . . . . . . . . . . . . . . . . . . . 7 72 4.2. RTM Capability Sub-TLV . . . . . . . . . . . . . . . . . 8 73 4.3. RTM Capability Advertisement in OSPFv2 . . . . . . . . . 9 74 4.4. RTM Capability Advertisement in OSPFv3 . . . . . . . . . 9 75 4.5. RTM Capability Advertisement in IS-IS . . . . . . . . . . 9 76 4.6. RSVP-TE Control Plane Operation to Support RTM . . . . . 10 77 4.7. RTM_SET Object . . . . . . . . . . . . . . . . . . . . . 11 78 4.7.1. RSO Sub-objects . . . . . . . . . . . . . . . . . . . 12 79 5. Data Plane Theory of Operation . . . . . . . . . . . . . . . 15 80 6. Applicable PTP Scenarios . . . . . . . . . . . . . . . . . . 15 81 7. One-step Clock and Two-step Clock Modes . . . . . . . . . . . 16 82 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 83 8.1. New RTM G-ACh . . . . . . . . . . . . . . . . . . . . . . 18 84 8.2. New RTM TLV Registry . . . . . . . . . . . . . . . . . . 18 85 8.3. New RTM Sub-TLV Registry . . . . . . . . . . . . . . . . 19 86 8.4. RTM Capability sub-TLV . . . . . . . . . . . . . . . . . 19 87 8.5. IS-IS RTM Application ID . . . . . . . . . . . . . . . . 20 88 8.6. RTM_SET Object RSVP Class Number, Class Type and Sub- 89 object Types . . . . . . . . . . . . . . . . . . . . . . 20 90 9. Security Considerations . . . . . . . . . . . . . . . . . . . 21 91 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 92 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 93 11.1. Normative References . . . . . . . . . . . . . . . . . . 22 94 11.2. Informative References . . . . . . . . . . . . . . . . . 23 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 97 1. Introduction 99 Time synchronization protocols, Network Time Protocol version 4 100 (NTPv4) [RFC5905] and Precision Time Protocol (PTP) Version 2 101 [IEEE.1588.2008] can be used to synchronize clocks across network 102 domain. Measurement of the time a PTP event message spends 103 traversing a node (using precise times of receipt at an ingress 104 interface and transmission at an egress interface), called Residence 105 Time, is one of on-path support types defined in [IEEE.1588.2008] and 106 can be used to improve the accuracy of clock synchronization. This 107 document defines new Generalized Associated Channel (G-ACh) that can 108 be used in Multi-Protocol Label Switching (MPLS) network to measure 109 Residence Time over Label Switched Path (LSP). Mechanisms for 110 transport of time synchronization protocol packets over MPLS are out 111 of scope in this document. 113 Though it is possible to use RTM over LSPs instantiated using LDP 114 such scenarios are outside the scope of this document. The scope of 115 this document is on LSPs instantiated using RSVP-TE [RFC3209] because 116 the LSP's path can be determined. 118 [I-D.ietf-tictoc-1588overmpls] describes alternative method of on- 119 path support for timing distribution protocols. Comparison of 120 proposed solutions is outside the scope of this document. 122 1.1. Conventions used in this document 124 1.1.1. Terminology 126 MPLS: Multi-Protocol Label Switching 128 ACH: Associated Channel 130 TTL: Time-to-Live 132 G-ACh: Generic Associated Channel 134 GAL: Generic Associated Channel Label 136 NTP: Network Time Protocol 138 ppm: parts per million 140 PTP: Precision Time Protocol 141 LSP: Label Switched Path 143 LSR: Label Switching Router 145 OAM: Operations, Administration, and Maintenance 147 RRO: Record Route Object 149 RSO: RTM Set Object 151 RTM: Residence Time Measurement 153 IGP: Internal Gateway Protocol 155 1.1.2. Requirements Language 157 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 158 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 159 "OPTIONAL" in this document are to be interpreted as described in 160 [RFC2119]. 162 2. Residence Time Measurement 164 Packet Loss and Delay Measurement for MPLS Networks [RFC6374] can be 165 used to measure one-way or two-way end-to-end propagation delay over 166 LSP or PW. But these metrics are insufficient for use in some 167 applications, for example, time synchronization across a network as 168 defined in the Precision Time Protocol (PTP). PTPv2 [IEEE.1588.2008] 169 uses "residence time", the time it takes for a PTPv2 event packet to 170 transit a node. Residence times are accumulated in the 171 correctionField of the PTP event messages, as defined in 172 [IEEE.1588.2008], or of the associated follow-up messages (or 173 Delay_Resp message associated with the Delay_Req message) in case of 174 two-step clocks (detailed discussion in Section 7). The residence 175 time values are specific to each output PTP port and message. 177 IEEE 1588 uses this residence time to correct the propagated time, 178 effectively making these nodes transparent. 180 This document proposes mechanism to accumulate packet residence time 181 from all LSRs that support the mechanism across a particular LSP. 182 The values accumulated in scratchpad fields of MPLS RTM messages can 183 be used by the last RTM-capable LSR on an LSP to update the 184 correctionField of the corresponding PTP event packet prior to 185 performing the usual PTP processing. 187 3. G-ACh for Residence Time Measurement 189 RFC 5586 [RFC5586] and RFC 6423 [RFC6423] extended applicability of 190 PW Associated Channel (ACH) [RFC5085] to LSPs. G-ACh provides a 191 mechanism to transport OAM and other control messages. Processing by 192 arbitrary transit LSRs can be triggered through controlled use of the 193 Time-to-Live (TTL) value. In a way that is analogous to PTP 194 operations, the packet residence time can be handled by the RTM 195 capable node either as "one-step clock" or as a "two-step clock". 197 The packet format for Residence Time Measurement (RTM) is presented 198 in Figure 1 200 0 1 2 3 201 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 1 202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 203 |0 0 0 1|Version| Reserved | RTM Channel | 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | | 206 | Scratch Pad | 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | Type | Length | 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | Value | 211 ~ ~ 212 | | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 Figure 1: RTM G-ACh packet format for Residence Time Measurement 217 o First four octets are defined as G-ACh Header in [RFC5586] 219 o The Version field is set to 0, as defined in RFC 4385 [RFC4385]. 221 o The Reserved field MUST be set to 0 on transmit and ignored on 222 receipt. 224 o The RTM G-ACh field, value to be allocated by IANA, identifies the 225 packet as such. 227 o The Scratch Pad field is 8 octets in length. The first RTM- 228 capable LSR MUST initialize the Scratch Pad field, it SHOULD set 229 it to zero value. The Scratch Pad is used to accumulate the 230 residence time spent in each RTM capable LSR transited by the 231 packet on its path from ingress LSR to egress LSR. Its format is 232 IEEE double precision and its units are nanoseconds. Note: 233 depending on one-step or two-step operation (Section 7), the 234 residence time might be related to the same packet carried in the 235 Value field or to a packet carried in a different RTM packet. 237 o The Type field identifies the type of Value that the TLV carries. 238 IANA will be asked to create a sub-registry in Generic Associated 239 Channel (G-ACh) Parameters Registry called "MPLS RTM TLV 240 Registry". 242 o The Length field contains the number of octets of the Value field. 244 o The optional Value field may be used to carry a packet of a given 245 time synchronization protocol. If packet data is carried in the 246 RTM message, then this is identified by Type accordingly. The 247 data MAY be NTP [RFC5905] or PTP [IEEE.1588.2008]. It is 248 important to note that the packet may be authenticated or 249 encrypted and carried over MPLS LSP edge to edge unchanged while 250 residence time being accumulated in the Scratch Pad field. Sub- 251 TLVs MAY be included in the Value field. 253 o The TLV MUST be included in the RTM message, even if the length of 254 the Value field is zero. 256 3.1. PTP Packet Sub-TLV 258 Figure 2 presents format of a PTP sub-TLV that MUST be precede every 259 PTP packet carried in RTM TLV. 261 0 1 2 3 262 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 1 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 | Type | Length | 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 | Flags |PTPType| 267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 | Port ID | 269 | | 270 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | | Sequence ID | 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 Figure 2: PTP Sub-TLV format 276 where Flags field has format 277 0 1 2 278 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 7 279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 280 |S| Reserved | 281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 283 Figure 3: Flags field format of PTP Packet Sub-TLV 285 o The Type field identifies PTP sub-TLV defined in the Table 19 286 Values of messageType field in [IEEE.1588.2008]. 288 o The Length field of the PTP sub-TLV contains the number of octets 289 of the Value field and MUST be 20. 291 o The Flags field currently defines one bit, the S-bit, that defines 292 whether or not the current message has been processed by a 2-step 293 node, where the flag is cleared if the message has been handled 294 exclusively by 1-step nodes and there is no follow-up message, and 295 set if there has been at least one 2-step node and a follow-up 296 message is forthcoming. 298 o The PTPType indicates the type of PTP packet carried in the TLV. 299 PTPType is the messageType field of the PTPv2 packet whose values 300 are defined in the Table 19 [IEEE.1588.2008]. 302 o The 10 octets long Port ID field contains the identity of the 303 source port. 305 o The Sequence ID is the sequence ID of the PTP message carried in 306 the Value field of the message. 308 4. Control Plane Theory of Operation 310 The operation of RTM depends upon TTL expiry to deliver an RTM packet 311 from one RTM capable interface to the next along the path from 312 ingress LSR to egress LSR. This means that an LSR with RTM capable 313 interfaces MUST be able to compute a TTL which will cause the expiry 314 of an RTM packet at the next LSR with RTM capable interfaces. 316 4.1. RTM Capability 318 Note that RTM capability of a node is with respect to the pair of 319 interfaces that will be used to forward an RTM packet. In general, 320 the ingress interface of this pair must be able to capture the 321 arrival time of the packet and encode it in some way such that this 322 information will be available to the egress interface. 324 The supported modes (1-step verses 2-step) of any pair of interfaces 325 is then determined by the capability of the egress interface. In 326 both cases, the egress interface implementation MUST be able to 327 determine the precise departure time of the same packet and determine 328 from this, and the arrival time information from the corresponding 329 ingress interface, the difference representing the residence time for 330 the packet. 332 An interface with the ability to do this and update the associated 333 ScratchPad in real-time (i.e. while the packet is being forwarded) is 334 said to be 1-step capable. 336 Hence while both ingress and egress interfaces are required to 337 support RTM, for the pair to be RTM-capable, it is the egress 338 interface that determines whether or not the node is 1-step or 2-step 339 capable with respect to the interface-pair. 341 The RTM capability used in the sub-TLV shown in Figure 4 is thus 342 associated with the egress port of the node making the advertisement, 343 while the ability of any pair of interfaces that includes this egress 344 interface to support any mode of RTM depends on the ability of that 345 interface to record packet arrival time in some way that can be 346 conveyed to and used by that egress interface. 348 When an LSR uses an IGP to carry the RTM capability sub-TLV, the sub- 349 TLV MUST reflect the RTM capability (1-step or 2-step) associated 350 with egress interfaces and MUST NOT propagate this sub-TLV in IGP 351 LSAs sent from a router which describe a particular interface that 352 does not support the same capability for RTM messages it receives. 354 4.2. RTM Capability Sub-TLV 356 The format for the RTM Capabilities sub-TLV is presented in Figure 4 358 0 1 2 3 359 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 1 360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 361 | Type(TBA5) | Length | 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | RTM | Reserved | 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 Figure 4: RTM Capability sub-TLV 368 o Type value will be assigned by IANA from appropriate registries. 370 o Length MUST be set to 4. 372 o RTM (capability) - is a three-bit long bit-map field with values 373 defined as follows: 375 * 0b001 - one-step RTM supported; 377 * 0b010 - two-step RTM supported; 379 * 0b100 - reserved. 381 o Reserved field must be set to all zeroes on transmit and ignored 382 on receipt. 384 [RFC4202] explains that the Interface Switching Capability Descriptor 385 describes switching capability of an interface. For bi-directional 386 links, the switching capabilities of an interface are defined to be 387 the same in either direction. I.e., for data entering the node 388 through that interface and for data leaving the node through that 389 interface". That principle SHOULD be applied when a node advertises 390 RTM Capability. 392 A node that supports RTM MUST be able to act in two-step mode and MAY 393 also support one-step RTM mode. Detailed discussion of one-step and 394 two-step RTM modes in Section 7. 396 4.3. RTM Capability Advertisement in OSPFv2 398 The capability to support RTM on a particular link advertised in the 399 OSPFv2 Extended Link Opaque LSA described in Section 3 [RFC7684] as 400 RTM Capability sub-TLV, presented in Figure 4, of the OSPFv2 Extended 401 Link TLV. 403 Type value will be assigned by IANA from the OSPF Extended Link TLV 404 Sub-TLVs registry that will be created per [RFC7684] request. 406 4.4. RTM Capability Advertisement in OSPFv3 408 The capability to support RTM on a particular link in OSPFv3 can be 409 advertised by including an RTM Capability sub-TLV defined in 410 Section 4.3 in the following TLVs defined in 411 [I-D.ietf-ospf-ospfv3-lsa-extend] Intra-Area-Prefix TLV, IPv6 Link- 412 Local Address TLV, or IPv4 Link-Local Address TLV when these are 413 included in E-Link-LSA. 415 4.5. RTM Capability Advertisement in IS-IS 417 The RTM capability logically belongs to a group of parameters 418 characterized as "generic information not directly related to the 419 operation of the IS-IS protocol" [RFC6823]. Hence the capability to 420 process RTM messages can be advertised by including RTM Capability 421 sub-TLV in GENINFO TLV [RFC6823]. 423 With respect to the Flags field of the GENINFO TLV: 425 o The S bit MUST be cleared to prevent the RTM Capability sub-TLV 426 from leaking between levels. 428 o The D bit of the Flags field MUST be cleared as required by 429 [RFC6823]. 431 o The I bit and the V bit MUST be set accordingly depending on 432 whether RTM capability being advertised for IPv4 or IPv6 interface 433 of the node. 435 Application ID (TBA6) will be assigned from the Application 436 Identifiers for TLV 251 IANA registry. The RTM Capability sub-TLV, 437 presented in Figure 4, MUST be included in GENINFO TLV in Application 438 Specific Information. 440 4.6. RSVP-TE Control Plane Operation to Support RTM 442 Throughout this document we refer to an LSR as RTM capable LSR when 443 at least one of its interfaces is RTM capable. Figure 5 provides an 444 example of relationship between roles a network element may have in 445 PTP over MPLS scenario and RTM capability: 447 ----- ----- ----- ----- ----- ----- ----- 448 | A |-----| B |-----| C |-----| D |-----| E |-----| F |-----| G | 449 ----- ----- ----- ----- ----- ----- ----- 451 Figure 5: RTM capable roles 453 o A is a Boundary Clock with its egress port in Master state. Node 454 A transmits PTP messages; 456 o B is the ingress LER for the MPLS LSP and is not RTM capable; 458 o C is the first RTM capable LSR; it initializes the RTM Scratch Pad 459 field and encapsulates PTP messages in the RTM ACH; the 460 transmitted Scratch Pad information includes the residence time 461 measured by C; 463 o D is a transit LSR that is not RTM capable; it passes along the 464 RTM ACH encapsulated PTP message unmodified; 466 o E is the last RTM capable LSR; it updates the Correction field of 467 the PTP message with the value in the Scratch Pad field of the RTM 468 ACH, and removes the RTM ACH encapsulation; 470 o F is the egress LER for the MPLS LSP and is not RTM capable; 472 o G is a Boundary Clock with its ingress port in Slave state. Node 473 G receives PTP messages. 475 An ingress LSR that is configured to perform RTM along a path through 476 an MPLS network to an egress LSR verifies that the selected egress 477 LSR has an interface that supports RTM via the egress LSR's 478 advertisement of the RTM Capability sub-TLV. In the Path message 479 that the ingress LSR uses to instantiate the LSP to that egress LSR 480 it places initialized Record Route Object (RRO) [RFC3209] and RTM Set 481 Object (RSO) [Section 4.7], which tell the egress LSR that RTM is 482 requested for this LSP. 484 In the Resv message that the egress LSR sends in response to the 485 received Path message, it includes initialized RRO and RSO. The RSO 486 contains an ordered list, from egress LSR to ingress LSR, of the RTM 487 capable LSRs along the LSP's path. Each such LSR will use the ID of 488 the first LSR in the RSO in conjunction with the RRO to compute the 489 hop count to its downstream LSR with reachable RTM capable interface. 490 It will also insert its ID at the beginning of the RTM Set Object 491 before forwarding the Resv upstream. 493 After the ingress LSR receives the Resv, it MAY begin sending RTM 494 packets to the first RTM capable LSR on the LSP's path. Each RTM 495 packet has its Scratch Pad field initialized and its TTL set to 496 expire on that first subsequent RTM capable LSR. 498 It should be noted that RTM can also be used for LSPs instantiated 499 using [RFC3209] in an environment in which all interfaces in an IGP 500 support RTM. In this case the RSO MAY be omitted. 502 4.7. RTM_SET Object 504 RTM capable interfaces can be recorded via RTM_SET object (RSO). The 505 RTM Set Class is TBA7. This document defines one C_Type, Type TBA8 506 RTM Set. The RTM_SET object format presented in Figure 6 507 0 1 2 3 508 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 1 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | | 511 ~ Sub-objects ~ 512 | | 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 Figure 6: RTM Set object format 517 The contents of a RTM_SET object are a series of variable-length data 518 items called sub-objects. The sub-objects are defined in 519 Section 4.7.1 below. 521 The RSO can be present in both RSVP Path and Resv messages. If a 522 Path message contains multiple RSOs, only the first RSO is 523 meaningful. Subsequent RSOs SHOULD be ignored and SHOULD NOT be 524 propagated. Similarly, if in a Resv message multiple RSOs are 525 encountered following a FILTER_SPEC before another FILTER_SPEC is 526 encountered, only the first RSO is meaningful. Subsequent RSOs 527 SHOULD be ignored and SHOULD NOT be propagated. 529 4.7.1. RSO Sub-objects 531 The RTM Set object contains an ordered list, from egress LSR to 532 ingress LSR, of the RTM capable LSRs along the LSP's path. 534 The contents of a RTM_SET object are a series of variable-length data 535 items called sub-objects. Each sub-object has its own Length field. 536 The length contains the total length of the sub-object in bytes, 537 including the Type and Length fields. The length MUST always be a 538 multiple of 4, and at least 8 (smallest IPv4 sub-object). 540 Sub-objects are organized as a last-in-first-out stack. The first 541 -out sub-object relative to the beginning of RSO is considered the 542 top. The last-out sub-object is considered the bottom. When a new 543 sub-object is added, it is always added to the top. 545 Three kinds of sub-objects for RSO are currently defined. 547 4.7.1.1. IPv4 Sub-object 548 0 1 2 3 549 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 1 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | Type | Length | Flags | 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 553 | IPv4 address | 554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 Figure 7: IPv4 sub-object format 558 Type 560 0x01 IPv4 address 562 Length 564 The Length contains the total length of the sub-object in bytes, 565 including the Type and Length fields. The Length is always 8. 567 IPv4 address 569 A 32-bit unicast host address. 571 Flags 573 TBD 575 4.7.1.2. IPv6 Sub-object 577 0 1 2 3 578 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 1 579 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 580 | Type | Length | Flags | 581 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 582 | | 583 | IPv6 address | 584 | | 585 | | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 Figure 8: IPv6 sub-object format 590 Type 592 0x02 IPv6 address 594 Length 595 The Length contains the total length of the sub-object in bytes, 596 including the Type and Length fields. The Length is always 20. 598 IPv6 address 600 A 128-bit unicast host address. 602 Flags 604 TBD 606 4.7.1.3. Unnumbered Interface Sub-object 608 0 1 2 3 609 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 1 610 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 | Type | Length | Flags | 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 | Router ID | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 615 | Interface ID | 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 Figure 9: IPv4 sub-object format 620 Type 622 0x03 Unnumbered interface 624 Length 626 The Length contains the total length of the sub-object in bytes, 627 including the Type and Length fields. The Length is always 12. 629 Router ID 631 The Router ID interpreted as discussed in the Section 2 of RFC 632 3447 [RFC3477]. 634 Interface ID 636 The identifier assigned to the link by the LSR specified by the 637 Router ID. 639 Flags 641 TBD 643 5. Data Plane Theory of Operation 645 After instantiating an LSP for a path using RSVP-TE [RFC3209] as 646 described in Section 4.6 or as described in the second paragraph of 647 Section 4 and in Section 4.6, ingress LSR MAY begin sending RTM 648 packets to the first downstream RTM capable LSR on that path. Each 649 RTM packet has its Scratch Pad field initialized and its TTL set to 650 expire on the next downstream RTM-capable LSR. Each RTM-capable LSR 651 on the explicit path receives an RTM packet and records the time at 652 which it receives that packet at its ingress interface as well as the 653 time at which it transmits that packet from its egress interface; 654 this should be done as close to the physical layer as possible to 655 ensure precise accuracy in time determination. The RTM-capable LSR 656 determines the difference between those two times; for 1-step 657 operation, this difference is determined just prior to or while 658 sending the packet, and the RTM-capable egress interface adds it to 659 the value in the Scratch Pad field of the message in progress. Note, 660 for the purpose of calculating a residence time, a common free 661 running clock synchronizing all the involved interfaces may be 662 sufficient, as, for example, 4.6 ppm accuracy leads to 4.6 nanosecond 663 error for residence time on the order of 1 millisecond. 665 For 2-step operation, the difference between packet arrival time (at 666 an ingress interface) and subsequent departure time (from an egress 667 interface) is determined at some later time prior to sending a 668 subsequent follow-up message, so that this value can be used to 669 update the correctionField in the follow-up message. 671 See Section 7 for further details on the difference between 1-step 672 and 2-step operation. 674 The last RTM-capable LSR on the LSP MAY then use the value in the 675 Scratch Pad field to perform time correction, if there is no follow- 676 up message. For example, the egress LSR may be a PTP Boundary Clock 677 synchronized to a Master Clock and will use the value in the Scratch 678 Pad field to update PTP's correctionField. 680 6. Applicable PTP Scenarios 682 The proposed approach can be directly integrated in a PTP network 683 based on the IEEE 1588 delay reqest-response mechanism. The RTM 684 capable LSR nodes act as end-to-end transparent clocks, and typically 685 boundary clocks, at the edges of the MPLS network, use the value in 686 the Scratch Pad field to update the correctionField of the 687 corresponding PTP event packet prior to performing the usual PTP 688 processing. 690 7. One-step Clock and Two-step Clock Modes 692 One-step mode refers to the mode of operation where an egress 693 interface updates the correctionField value of an original event 694 message. Two-step mode refers to the mode of operation where this 695 update is made in a subsequent follow-up message. 697 Processing of the follow-up message, if present, requires the 698 downstream end-point to wait for the arrival of the follow-up message 699 in order to combine correctionField values from both the original 700 (event) message and the subsequent (follow-up) message. In a similar 701 fashion, each 2-step node needs to wait for the related follow-up 702 message, if there is one, in order to update that follow-up message 703 (as opposed to creating a new one. Hence the first node that uses 704 2-step mode MUST do two things: 706 1. Mark the original event message to indicate that a follow-up 707 message will be forthcoming (this is necessary in order to 709 Let any subsequent 2-step node know that there is already a 710 follow-up message, and 712 Let the end-point know to wait for a follow-up message; 714 2. Create a follow-up message in which to put the RTM determined as 715 an initial correctionField value. 717 IEEE 1588v2 [IEEE.1588.2008] defines this behaviour for PTP messages. 719 Thus, for example, with reference to the PTP protocol, the PTPType 720 field identifies whether the message is a Sync message, Follow_up 721 message, Delay_Req message, or Delay_Resp message. The 10 octet long 722 Port ID field contains the identity of the source port, that is, the 723 specific PTP port of the boundary clock connected to the MPLS 724 network. The Sequence ID is the sequence ID of the PTP message 725 carried in the Value field of the message. 727 PTP messages also include a bit that indicates whether or not a 728 follow-up message will be coming. This bit, once it is set by a 729 2-step mode device, MUST stay set accordingly until the original and 730 follow-up messages are combined by an end-point (such as a Boundary 731 Clock). 733 Thus, an RTM packet, containing residence time information relating 734 to an earlier packet, also contains information identifying that 735 earlier packet. 737 For compatibility with PTP, RTM (when used for PTP packets) must 738 behave in a similar fashion. To do this, a 2-step RTM capable egress 739 interface will need to examine the S-bit in the Flags field of the 740 PTP sub-TLV (for RTM messages that indicate they are for PTP) and - 741 if it is clear (set to zero), it MUST set it and create a follow-up 742 PTP Type RTM message. If the S bit is already set, then the RTM 743 capable node MUST wait for the RTM message with the PTP type of 744 follow-up and matching originator and sequence number to make the 745 corresponding residence time update to the Scratch Pad field. 747 In practice an RTM operating according to two-step clock behaves like 748 a two-steps transparent clock. 750 A 1-step capable RTM node MAY elect to operate in either 1-step mode 751 (by making an update to the Scratch Pad field of the RTM message 752 containing the PTP even message), or in 2-step mode (by making an 753 update to the Scratch Pad of a follow-up message when its presence is 754 indicated), but MUST NOT do both. 756 Two main subcases can be identified for an RTM node operating as a 757 two-step clock: 759 A) If any of the previous RTM capable node or the previous PTP clock 760 (e.g. the BC connected to the first LSR), is a two-step clock, the 761 residence time is added to the RTM packet that has been created to 762 include the associated PTP packet (i.e. follow-up message in the 763 downstream direction), if the local RTM-capable LSR is also operating 764 as a two-step clock. This RTM packet carries the related accumulated 765 residence time and the appropriate values of the Sequence Id and Port 766 Id (the same identifiers carried in the packet processed) and the 767 Two-step Flag set to 1. 769 Note that the fact that an upstream RTM-capable node operating in the 770 two-step mode has created a follow-up message does not require any 771 subsequent RTM capable LSR to also operate in the 2-step mode, as 772 long as that RTM-capable LSR forwards the follow-up message on the 773 same LSP on which it forwards the corresponding previous message. 775 A one-step capable RTM node MAY elect to update the RTM follow-up 776 message as if it were operating in two-step mode, however, it MUST 777 NOT update both messages. 779 A PTP event packet (sync) is carried in the RTM packet in order for 780 an RTM node to identify that residence time measurement must be 781 performed on that specific packet. 783 To handle the residence time of the Delay request message on the 784 upstream direction, an RTM packet must be created to carry the 785 residence time on the associated downstream Delay Resp message. 787 The last RTM node of the MPLS network in addition to update the 788 correctionField of the associated PTP packet, must also properly 789 handle the two-step flag of the PTP packets. 791 B) When the PTP network connected to the MPLS and RTM node, operates 792 in one-step clock mode, the associated RTM packet must be created by 793 the RTM node itself. The associated RTM packet including the PTP 794 event packet needs now to indicate that a follow up message will be 795 coming. 797 The last RTM node of the LSP, modeif it receives an RTM message with 798 a PTP payload indicating a follow-up message will be forthcoming, 799 must generate a follow-up message and properly set the two-step flag 800 of the PTP packets. 802 8. IANA Considerations 804 8.1. New RTM G-ACh 806 IANA is requested to reserve a new G-ACh as follows: 808 +-------+----------------------------+---------------+ 809 | Value | Description | Reference | 810 +-------+----------------------------+---------------+ 811 | TBA1 | Residence Time Measurement | This document | 812 +-------+----------------------------+---------------+ 814 Table 1: New Residence Time Measurement 816 8.2. New RTM TLV Registry 818 IANA is requested to create sub-registry in Generic Associated 819 Channel (G-ACh) Parameters Registry called "MPLS RTM TLV Registry". 820 All code points in the range 0 through 127 in this registry shall be 821 allocated according to the "IETF Review" procedure as specified in 822 [RFC5226] . Remaining code points are allocated according to the 823 table below. This document defines the following new values RTM TLV 824 type s: 826 +-----------+-------------+-------------------------+ 827 | Value | Description | Reference | 828 +-----------+-------------+-------------------------+ 829 | 0 | Reserved | This document | 830 | 1 | No payload | This document | 831 | 2 | PTPv2 | This document | 832 | 3 | NTP | This document | 833 | 4-127 | Reserved | IETF Consensus | 834 | 128 - 191 | Reserved | First Come First Served | 835 | 192 - 255 | Reserved | Private Use | 836 +-----------+-------------+-------------------------+ 838 Table 2: RTM TLV Type 840 8.3. New RTM Sub-TLV Registry 842 IANA is requested to create sub-registry in MPLS RTM TLV Registry, 843 requested in Section 8.2, called "MPLS RTM Sub-TLV Registry". All 844 code points in the range 0 through 127 in this registry shall be 845 allocated according to the "IETF Review" procedure as specified in 846 [RFC5226] . Remaining code points are allocated according to the 847 table below. This document defines the following new values RTM sub- 848 TLV types: 850 +-----------+-------------+-------------------------+ 851 | Value | Description | Reference | 852 +-----------+-------------+-------------------------+ 853 | 0 | Reserved | This document | 854 | 1 | PTP 2-step | This document | 855 | 2-127 | Reserved | IETF Consensus | 856 | 128 - 191 | Reserved | First Come First Served | 857 | 192 - 255 | Reserved | Private Use | 858 +-----------+-------------+-------------------------+ 860 Table 3: RTM Sub-TLV Type 862 8.4. RTM Capability sub-TLV 864 IANA is requested to assign a new type for RTM Capability sub-TLV 865 from future OSPF Extended Link TLV Sub-TLVs registry as follows: 867 +-------+----------------+---------------+ 868 | Value | Description | Reference | 869 +-------+----------------+---------------+ 870 | TBA2 | RTM Capability | This document | 871 +-------+----------------+---------------+ 873 Table 4: RTM Capability sub-TLV 875 8.5. IS-IS RTM Application ID 877 IANA is requested to assign a new Application ID for RTM from the 878 Application Identifiers for TLV 251 registry as follows: 880 +-------+-------------+---------------+ 881 | Value | Description | Reference | 882 +-------+-------------+---------------+ 883 | TBA3 | RTM | This document | 884 +-------+-------------+---------------+ 886 Table 5: IS-IS RTM Application ID 888 8.6. RTM_SET Object RSVP Class Number, Class Type and Sub-object Types 890 IANA is requested to assign a new Class Number for RTM_SET object as 891 follows: 893 +-------+----------------+---------------+ 894 | Value | Description | Reference | 895 +-------+----------------+---------------+ 896 | TBA4 | RTM_SET object | This document | 897 +-------+----------------+---------------+ 899 Table 6: RTM_SET object Class 901 IANA is requested to assign a new Class Type for RTM_SET object as 902 follows: 904 +-------+-------------+---------------+ 905 | Value | Description | Reference | 906 +-------+-------------+---------------+ 907 | TBA5 | RTM Set | This document | 908 +-------+-------------+---------------+ 910 Table 7: RTM_SET object Class Type 912 IANA requested to create new sub-registry for sub-object types of 913 RTM_SET object as follows: 915 +-----------+----------------------+-------------------------+ 916 | Value | Description | Reference | 917 +-----------+----------------------+-------------------------+ 918 | 0 | Reserved | | 919 | 1 | IPv4 address | This document | 920 | 2 | IPv6 address | This document | 921 | 3 | Unnumbered interface | This document | 922 | 4-127 | Reserved | IETF Consensus | 923 | 128 - 191 | Reserved | First Come First Served | 924 | 192 - 255 | Reserved | Private Use | 925 +-----------+----------------------+-------------------------+ 927 Table 8: RTM_SET object sub-object types 929 9. Security Considerations 931 Routers that support Residence Time Measurement are subject to the 932 same security considerations as defined in [RFC5586] . 934 In addition - particularly as applied to use related to PTP - there 935 is a presumed trust model that depends on the existence of a trusted 936 relationship of at least all PTP-aware nodes on the path traversed by 937 PTP messages. This is necessary as these nodes are expected to 938 correctly modify specific content of the data in PTP messages and 939 proper operation of the protocol depends on this ability. 941 As a result, the content of the PTP-related data in RTM messages that 942 will be modified by intermediate nodes cannot be authenticated, and 943 the additional information that must be accessible for proper 944 operation of PTP 1-step and 2-step modes MUST be accessible to 945 intermediate nodes (i.e. - MUST NOT be encrypted in a manner that 946 makes this data inaccessible). 948 While it is possible for a supposed compromised LSR to intercept and 949 modify the G-ACh content, this is an issue that exists for LSRs in 950 general - for any and all data that may be carried over an LSP - and 951 is therefore the basis for an additional presumed trust model 952 associated with existing LSPs and LSRs. 954 The ability for potentially authenticating and/or encrypting RTM and 955 PTP data that is not needed by intermediate RTM/PTP-capable nodes is 956 for further study. 958 Security requirements of time protocols are provided in RFC 7384 959 [RFC7384]. 961 10. Acknowledgements 963 Authors want to thank Loa Andersson for his thorough review and 964 thoghtful comments. 966 11. References 968 11.1. Normative References 970 [I-D.ietf-ospf-ospfv3-lsa-extend] 971 Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 972 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-09 973 (work in progress), November 2015. 975 [IEEE.1588.2008] 976 "Standard for a Precision Clock Synchronization Protocol 977 for Networked Measurement and Control Systems", 978 IEEE Standard 1588, March 2008. 980 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 981 Requirement Levels", BCP 14, RFC 2119, 982 DOI 10.17487/RFC2119, March 1997, 983 . 985 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 986 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 987 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 988 . 990 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 991 in Resource ReSerVation Protocol - Traffic Engineering 992 (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, 993 . 995 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, 996 "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for 997 Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, 998 February 2006, . 1000 [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual 1001 Circuit Connectivity Verification (VCCV): A Control 1002 Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085, 1003 December 2007, . 1005 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 1006 "MPLS Generic Associated Channel", RFC 5586, 1007 DOI 10.17487/RFC5586, June 2009, 1008 . 1010 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1011 "Network Time Protocol Version 4: Protocol and Algorithms 1012 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1013 . 1015 [RFC6423] Li, H., Martini, L., He, J., and F. Huang, "Using the 1016 Generic Associated Channel Label for Pseudowire in the 1017 MPLS Transport Profile (MPLS-TP)", RFC 6423, 1018 DOI 10.17487/RFC6423, November 2011, 1019 . 1021 [RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising 1022 Generic Information in IS-IS", RFC 6823, 1023 DOI 10.17487/RFC6823, December 2012, 1024 . 1026 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 1027 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 1028 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 1029 2015, . 1031 11.2. Informative References 1033 [I-D.ietf-tictoc-1588overmpls] 1034 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. 1035 Montini, "Transporting Timing messages over MPLS 1036 Networks", draft-ietf-tictoc-1588overmpls-07 (work in 1037 progress), October 2015. 1039 [RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions 1040 in Support of Generalized Multi-Protocol Label Switching 1041 (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005, 1042 . 1044 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1045 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1046 DOI 10.17487/RFC5226, May 2008, 1047 . 1049 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 1050 Measurement for MPLS Networks", RFC 6374, 1051 DOI 10.17487/RFC6374, September 2011, 1052 . 1054 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 1055 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 1056 October 2014, . 1058 Authors' Addresses 1060 Greg Mirsky 1061 Ericsson 1063 Email: gregory.mirsky@ericsson.com 1065 Stefano Ruffini 1066 Ericsson 1068 Email: stefano.ruffini@ericsson.com 1070 Eric Gray 1071 Ericsson 1073 Email: eric.gray@ericsson.com 1075 John Drake 1076 Juniper Networks 1078 Email: jdrake@juniper.net 1080 Stewart Bryant 1081 Cisco Systems 1083 Email: stbryant@cisco.com 1085 Alexander Vainshtein 1086 ECI Telecom 1088 Email: Alexander.Vainshtein@ecitele.com