idnits 2.17.1 draft-ietf-mpls-rfc6374-sfl-05.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 07, 2020) is 1452 days in the past. Is this intentional? 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-09) exists of draft-bryant-mpls-sfl-control-06 == Outdated reference: A later version (-11) exists of draft-ietf-mpls-sfl-framework-06 -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted by RFC 9341) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group S. Bryant 3 Internet-Draft S. Bryant 4 Intended status: Standards Track Futurewei Technologies Inc. 5 Expires: October 9, 2020 M. Chen 6 Z. Li 7 Huawei 8 G. Swallow 9 Southend Technical Center 10 S. Sivabalan 11 Cisco Systems 12 G. Mirsky 13 ZTE Corp. 14 G. Fioccola 15 Huawei Technologies 16 April 07, 2020 18 RFC6374 Synonymous Flow Labels 19 draft-ietf-mpls-rfc6374-sfl-05 21 Abstract 23 This document describes a method of making RFC6374 performance 24 measurements on flows carried over an MPLS Label Switched path. This 25 allows loss and delay measurements to be made on multi-point to point 26 LSPs and allows the measurement of flows within an MPLS construct 27 using RFC6374. 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 https://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 October 9, 2020. 46 Copyright Notice 48 Copyright (c) 2020 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 (https://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 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 65 3. RFC6374 Packet Loss Measurement with SFL . . . . . . . . . . 4 66 4. RFC6374 Single Packet Delay Measurement . . . . . . . . . . . 4 67 5. Data Service Packet Delay Measurement . . . . . . . . . . . . 5 68 6. Some Simplifying Rules . . . . . . . . . . . . . . . . . . . 6 69 7. Multiple Packet Delay Characteristics . . . . . . . . . . . . 7 70 7.1. Method 1: Time Buckets . . . . . . . . . . . . . . . . . 7 71 7.2. Method 2 Classic Standard Deviation . . . . . . . . . . . 9 72 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 10 73 7.3. Per Packet Delay Measurement . . . . . . . . . . . . . . 11 74 7.4. Average Delay . . . . . . . . . . . . . . . . . . . . . . 11 75 8. Sampled Measurement . . . . . . . . . . . . . . . . . . . . . 13 76 9. Carrying RFC6374 Packets over an LSP using an SFL . . . . . . 13 77 9.1. RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . . 15 78 10. Applicability to Pro-active and On-demand Measurement . . . . 16 79 11. RFC6374 Combined Loss-Delay Measurement . . . . . . . . . . . 16 80 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16 81 13. Security Considerations . . . . . . . . . . . . . . . . . . . 17 82 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 83 14.1. Allocation of PW Associated Channel Type . . . . . . . . 17 84 14.2. MPLS Loss/Delay TLV Object . . . . . . . . . . . . . . . 17 85 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 86 15.1. Normative References . . . . . . . . . . . . . . . . . . 18 87 15.2. Informative References . . . . . . . . . . . . . . . . . 18 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 90 1. Introduction 92 [RFC6374] was originally designed for use as an OAM protocol for use 93 with MPLS Transport Profile (MPLS-TP) [RFC5921] LSPs. MPLS-TP only 94 supports point-to-point and point-to-multi-point LSPs. This document 95 describes how to use RFC6374 in the general MPLS case, and also 96 introduces a number of more sophisticated measurements of 97 applicability to both cases. 99 [RFC8372] describes the requirement for introducing flow identities 100 when using RFC6374 [RFC6374] packet Loss Measurements (LM). In 101 summary RFC6374 uses the loss-measurement (LM) packet as the packet 102 accounting demarcation point. Unfortunately this gives rise to a 103 number of problems that may lead to significant packet accounting 104 errors in certain situations. For example: 106 1. Where a flow is subjected to Equal Cost Multi-Path (ECMP) 107 treatment packets can arrive out of order with respect to the LM 108 packet. 110 2. Where a flow is subjected to ECMP treatment, packets can arrive 111 at different hardware interfaces, thus requiring reception of an 112 LM packet on one interface to trigger a packet accounting action 113 on a different interface which may not be co-located with it. 114 This is a difficult technical problem to address with the 115 required degree of accuracy. 117 3. Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs 118 and PWs) local processing may be distributed over a number of 119 processor cores, leading to synchronization problems. 121 4. Link aggregation techniques may also lead to synchronization 122 issues. 124 5. Some forwarder implementations have a long pipeline between 125 processing a packet and incrementing the associated counter again 126 leading to synchronization difficulties. 128 An approach to mitigating these synchronization issue is described in 129 [RFC8321] in which packets are batched by the sender and each batch 130 is marked in some way such that adjacent batches can be easily 131 recognized by the receiver. 133 An additional problem arises where the LSP is a multi-point to point 134 LSP, since MPLS does not include a source address in the packet. 135 Network management operations require the measurement of packet loss 136 between a source and destination. It is thus necessary to introduce 137 some source specific information into the packet to identify packet 138 batches from a specific source. 140 [I-D.ietf-mpls-sfl-framework] describes a method of encoding per flow 141 instructions in an MPLS label stack using a technique called 142 Synonymous Flow Labels (SFL) in which labels which mimic the 143 behaviour of other labels provide the packet batch identifiers and 144 enable the per batch packet accounting. This memo specifies how SFLs 145 are used to perform RFC6374 packet loss and RFC6374 delay 146 measurements. 148 2. Requirements Language 150 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 151 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 152 "OPTIONAL" in this document are to be interpreted as described in BCP 153 14 [RFC2119] [RFC8174] when, and only when, they appear in all 154 capitals, as shown here. 156 3. RFC6374 Packet Loss Measurement with SFL 158 The data service packets of the flow being instrumented are grouped 159 into batches, and all the packets within a batch are marked with the 160 SFL [RFC8372] corresponding to that batch. The sender counts the 161 number of packets in the batch. When the batch has completed and the 162 sender is confident that all of the packets in that batch will have 163 been received, the sender issues an RFC6374 Query message to 164 determine the number actually received and hence the number of 165 packets lost. The RFC6374 Query message is sent using the same SFL 166 as the co-responding batch of data service packets. The format of 167 the Query and Response packet is described in Section 9. 169 4. RFC6374 Single Packet Delay Measurement 171 RFC6374 describes how to measure the packet delay by measuring the 172 transit time of an RFC6374 packet over an LSP. Such a packet may not 173 need to be carried over an SFL since the delay over a particular LSP 174 should be a function of the TC bits. 176 However, where SFLs are being used to monitor packet loss or where 177 label inferred scheduling is used [RFC3270] then the SFL would be 178 REQUIRED to ensure that the RFC6374 packet which was being used as a 179 proxy for a data service packet experienced a representative delay. 180 The format of an RFC6374 packet carried over the LSP using an SFL is 181 shown in Section 9. 183 5. Data Service Packet Delay Measurement 185 Where it is desired to more thoroughly instrument a packet flow and 186 to determine the delay of a number of packets it is undesirable to 187 send a large number of RFC6374 packets acting as proxy data service 188 packets Section 4. A method of directly measuring the delay 189 characteristics of a batch of packets is therefore needed. 191 Given the long intervals over which it is necessary to measure packet 192 loss, it is not necessarily the case that the batch times for the two 193 measurement types would be identical. This it is proposed that the 194 two measurements are relatively independent. The notion that they 195 are relatively independent arises for the potential for the two 196 batches to overlap in time, in which case either the delay batch time 197 will need to be cut short or the loss time will need to be extended 198 to allow correct reconciliation of the various counters. 200 The problem is illustrated in Figure 1 below: 202 (1) AAAAAAAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 204 SFL Marking of a packet batch for loss measurement 206 (2) AADDDDAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 208 SFL Marking of a subset if the packets for delay 210 (3) AAAAAAAADDDDBBBBBBBBAAAAAAAAAABBBBBBBBBB 212 SFL Marking of a subset of the packets across a 213 packet loss measurement boundary 215 (4) AACDCDCDAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 217 The case of multiple delay measurements within 218 a packet loss measurement 220 Figure 1: RFC6734 Query Packet with SFL 222 In case 1 of Figure 1 we show the case were loss measurement alone is 223 being carried out on the flow under analysis. For illustrative 224 purposes consider that in the time interval being analyzed, 10 225 packets always flow. 227 Now consider case 2 of Figure 1 where a small batch of packets need 228 to analyzed for delay. These are marked with a different SFL type 229 indicating that they are to be monitored for both loss and delay. 230 The SFL=A indicates loss batch A, SFL=D indicates a batch of packets 231 that are to be instrumented for delay, but SFL D is synonymous with 232 SFL A, which in turn is synonymous with the underlying FEC. Thus, a 233 packet marked D will be accumulated into the A loss batch, into the 234 delay statistics and will be forwarded as normal. Whether the packet 235 is actually counted twice (for loss and delay) or whether the two 236 counters are reconciled during reporting is a local matter. 238 Now consider case 3 of Figure 1 where a small batch of packets are 239 marked for delay across a loss batch boundary. These packets need to 240 considered as part of batch A or a part of batch B, and any RFC6374 241 Query needs to take place after all the packets A or D (which ever 242 option is chosen) have arrived at the receiving LSR. 244 Now consider case 4 of Figure 1. Here we have a case where it is 245 required to take a number of delay measurements within a batch of 246 packets that we are measuring for loss. To do this we need two SFLs 247 for delay (C and D) and alternate between them (on a delay batch by 248 delay batch basis) for the purposes of measuring the delay 249 characteristics of the different batches of packets. 251 6. Some Simplifying Rules 253 It is possible to construct a large set of overlapping measurement 254 type, in terms of loss, delay, loss and delay and batch overlap. If 255 we allow all combination of cases, this leads to configuration, 256 testing and implementation complexity and hence increased operation 257 and capital cost. The following simplifying rules represent the 258 default case: 260 1. Any system that needs to measure delay MUST be able to measure 261 loss. 263 2. Any system that is to measure delay MUST be configured to measure 264 loss. Whether the loss statistics are collected or not is a 265 local matter. 267 3. A delay measurement MAY start at any point during a loss 268 measurement batch, subject to rule 4. 270 4. A delay measurement interval MUST be short enough that it will 271 complete before the enclosing loss batch completes. 273 5. The duration of a second delay (D in Figure 1 batch must be such 274 that all packets from the packets belonging to a first delay 275 batch (C in Figure 1)will have been received before the second 276 delay batch completes. 278 Given that the sender controls both the start and duration of a loss 279 and a delay packet batch, these rules are readily implemented in the 280 control plane. 282 7. Multiple Packet Delay Characteristics 284 A number of methods are described. The expectation is that the MPLS 285 WG possibly with the assistance of the IPPM WG will select one or 286 maybe more than one of these methods for standardization. 288 Three Methods are discussed: 290 1. Time Buckets 292 2. Classic Standard Deviation 294 3. Average Delay 296 7.1. Method 1: Time Buckets 298 In this method the receiving LSR measures the inter-packet gap, 299 classifies the delay into a number of delay buckets and records the 300 number of packets in each bucket. As an example, if the operator 301 were concerned about packets with a delay of up to 1us, 2us, 4us, 302 8us, and over 8us then there would be five buckets and packets that 303 arrived up to 1us would cause the 1us bucket counter to increase, 304 between 1us and 2us the 2us bucket counter would increase etc. In 305 practice it might be better in terms of processing and potential 306 parallelism if, when a packet had a delay relative to its predecessor 307 of 2us both the up to 1us and the 2us counter were incremented and 308 any more detailed information was calculated in the analytics system. 310 This method allows the operator to see more structure in the jitter 311 characteristics than simply measuring the average jitter, and avoids 312 the complication of needing to perform a per packet multiply, but 313 will probably need to time intervals between buckets to be 314 programmable by the operator. 316 The packet format of an RFC6374 Bucket Jitter Measurement Message is 317 shown below: 319 0 1 2 3 320 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 1 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 |Version| Flags | Control Code | Message Length | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | QTF | RTF | RPTF | Reserved | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | Session Identifier | DS | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | Number of | Reserved | 329 | Buckets | | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | Interval in 10ns units | 332 | | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 | Number pkts in Bucket | 335 | | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 ~ ~ 338 ~ ~ 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 ~ ~ 341 ~ TLV Block ~ 342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 344 Figure 2: Bucket Jitter Measurement Message Format 346 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 347 Session Identifier, and DS Fields are as defined in section 3.7 of 348 RFC6374. The remaining fields are as follows: 350 o Number of Buckets in the measurement 352 o Reserved must be sent as zero and ignored on receipt 354 o Interval in 10ns units is the inter-packet interval for 355 this bucket 357 o Number Pkts in Bucket is the number of packets found in 358 this bucket. 360 There will be a number of Interval/Number pairs depending on the 361 number of buckets being specified by the Querier. If an RFC6374 362 message is being used to configure the buckets, (i.e. the responder 363 is creating or modifying the buckets according to the intervals in 364 the Query message), then the Responder MUST respond with 0 packets in 365 each bucket until it has been configured for a full measurement 366 period. This indicates that it was configured at the time of the 367 last response message, and thus the response is valid for the whole 368 interval. As per the [RFC6374] convention the Number of pkts in 369 Bucket fields are included in the Query message and set to zero. 371 Out of band configuration is permitted by this mode of operation. 373 Note this is a departure from the normal fixed format used in 374 RFC6374. 376 This RFC6374 message is carried over an LSP in the way described in 377 [RFC6374] and over an LSP with an SFL as described in Section 9. 379 7.2. Method 2 Classic Standard Deviation 381 In this method, provision is made for reporting the following delay 382 characteristics: 384 1. Number of packets in the batch (n). 386 2. Sum of delays in a batch (S) 388 3. Maximum Delay. 390 4. Minimum Delay. 392 5. Sum of squares of Inter-packet delay (SS). 394 Characteristic's 1 and 2 give the mean delay. Measuring the delay of 395 each pair in the batch is discussed in Section 7.3. 397 Characteristics 3 and 4 give the outliers. 399 Characteristics 1, 2 and 5 can be used to calculate the variance of 400 the inter-packet gap and hence the standard deviation giving a view 401 of the distribution of packet delays and hence the jitter. The 402 equation for the variance (var) is given by: 404 var = (SS - S*S/n)/(n-1) 406 There is some concern over the use of this algorithm for measuring 407 variance, because SS and S*S/n can be similar numbers, particularly 408 where variance is low. However the method commends it self by not 409 requiring a division in the hardware. 411 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 413 The packet format of an RFC6374 Multi-Packet Delay Measurement 414 Message is shown below: 416 0 1 2 3 417 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 1 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 |Version| Flags | Control Code | Message Length | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 | QTF | RTF | RPTF | Reserved | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | Session Identifier | DS | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 | Number of Packets | 426 | | 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 | Sum of Delays for Batch | 429 | | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | Minimum Delay | 432 | | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | Maximum Delay | 435 | | 436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 | Sum of squares of Inter-packet delay | 438 | | 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 ~ ~ 441 ~ TLV Block ~ 442 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 Figure 3: Multi-packet Delay Measurement Message Format 446 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 447 Session Identifier, and DS Fields are as defined in section 3.7 of 448 RFC6374. The remaining fields are as follows: 450 o Number of Packets is the number of packets in this batch 452 o Sum of Delays for Batch is the duration of the batch in the 453 time measurement format specified in the RTF field. 455 o Minimum Delay is the minimum inter-packet gap observed during 456 the batch in the time format specified in the RTF field. 458 o Maximum Delay is the maximum inter-packet gap observed during 459 the batch in the time format specified in the RTF field. 461 This RFC6374 message is carried over an LSP in the way described in 462 [RFC6374] and over an LSP with an SFL as described in Section 9. 464 7.3. Per Packet Delay Measurement 466 If detailed packet delay measurement is required then it might be 467 possible to record the inter-packet gap for each packet pair. In 468 other that exception cases of slow flows or small batch sizes, this 469 would create a large demand on storage in the instrumentation system, 470 bandwidth to such a storage system and bandwidth to the analytics 471 system. Such a measurement technique is outside the scope of this 472 document. 474 7.4. Average Delay 476 Introduced in [RFC8321] is the concept of a one way delay measurement 477 in which the average time of arrival of a set of packets is measured. 478 In this approach the packet is time-stamped at arrival and the 479 Responder returns the sum of the time-stamps and the number of times- 480 tamps. From this the analytics engine can determine the mean delay. 481 An alternative model is that the Responder returns the time stamp of 482 the first and last packet and the number of packets. This method has 483 the advantage of allowing the average delay to be determined at a 484 number of points along the packet path and allowing the components of 485 the delay to be characterized. 487 The packet format of an RFC6374 Average Delay Measurement Message is 488 shown below: 490 0 1 2 3 491 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 1 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 |Version| Flags | Control Code | Message Length | 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 | QTF | RTF | RPTF | Reserved | 496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 497 | Session Identifier | DS | 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 | Number of Packets | 500 | | 501 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 | Time of First Packet | 503 | | 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | Time of Last Packet | 506 | | 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Sum of Timestamps of Batch | 509 | | 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 ~ ~ 513 ~ TLV Block ~ 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 Figure 4: Average Delay Measurement Message Format 518 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 519 Session Identifier, and DS Fields are as defined in section 3.7 of 520 RFC6374. The remaining fields are as follows: 522 o Number of Packets is the number of packets in this batch. 524 o Time of First Packet is the time of arrival of the first 525 packet in the batch. 527 o Time of Last Packet is the time of arrival of the last 528 packet in the batch. 530 o Sum of Timestamps of Batch. 532 This RFC6374 message is carried over an LSP in the way described in 533 [RFC6374] and over an LSP with an SFL as described in Section 9. As 534 is the convention with RFC6374, the Query message contains 535 placeholders for the Response message. The placeholders are sent as 536 zero. 538 8. Sampled Measurement 540 In the discussion so far it has been assumed that we would measure 541 the delay characteristics of every packet in a delay measurement 542 interval defined by an SL of constant colour. In [RFC8321] the 543 concept of a sampled measurement is considered. That is the 544 Responder only measures a packet at the start of a group of packets 545 being marked for delay measurement by a particular colour, rather 546 than every packet in the marked batch. A measurement interval is not 547 defined by the duration of a marked batch of packets but the interval 548 between a pair of RFC6374 packets taking a readout of the delay 549 characteristic. This approach has the advantage that the measurement 550 is not impacted by ECMP effects. 552 9. Carrying RFC6374 Packets over an LSP using an SFL 554 The packet format of an RFC6374 Query message using SFLs is shown in 555 Figure 5. 557 +-------------------------------+ 558 | | 559 | LSP | 560 | Label | 561 +-------------------------------+ 562 | | 563 | Synonymous Flow | 564 | Label | 565 +-------------------------------+ 566 | | 567 | GAL | 568 | | 569 +-------------------------------+ 570 | | 571 | ACH Type = 0xA | 572 | | 573 +-------------------------------+ 574 | | 575 | RFC6374 Measurement Message | 576 | | 577 | +-------------------------+ | 578 | | | | 579 | | RFC6374 Fixed | | 580 | | Header | | 581 | | | | 582 | +-------------------------+ | 583 | | | | 584 | | Optional SFL TLV | | 585 | | | | 586 | +-------------------------+ | 587 | | | | 588 | | Optional Return | | 589 | | Information | | 590 | | | | 591 | +-------------------------+ | 592 | | 593 +-------------------------------+ 595 Figure 5: RFC6734 Query Packet with SFL 597 The MPLS label stack is exactly the same as that used for the user 598 data service packets being instrumented except for the inclusion of 599 the GAL [RFC5586] to allow the receiver to distinguish between normal 600 data packets and OAM packets. Since the packet loss measurements are 601 being made on the data service packets, an RFC6374 direct loss 602 measurement is being made, and which is indicated by the type field 603 in the ACH (Type = 0x000A). 605 The RFC6374 measurement message consists of the three components, the 606 RFC6374 fixed header as specified in [RFC6374] carried over the ACH 607 channel type specified the type of measurement being made (currently: 608 loss, delay or loss and delay) as specified in RFC6374. 610 Two optional TLVs MAY also be carried if needed. The first is the 611 SFL TLV specified in Section 9.1. This is used to provide the 612 implementation with a reminder of the SFL that was used to carry the 613 RFC6374 message. This is needed because a number of MPLS 614 implementations do not provide the MPLS label stack to the MPLS OAM 615 handler. This TLV is required if RFC6374 messages are sent over UDP 616 [RFC7876]. This TLV MUST be included unless, by some method outside 617 the scope of this document, it is known that this information is not 618 needed by the RFC6374 Responder. 620 The second set of information that may be needed is the return 621 information that allows the responder send the RFC6374 response to 622 the Querier. This is not needed if the response is requested in-band 623 and the MPLS construct being measured is a point to point LSP, but 624 otherwise MUST be carried. The return address TLV is defined in 625 RFC6378 and the optional UDP Return Object is defined in [RFC7876]. 627 9.1. RFC6374 SFL TLV 629 Editor's Note we need to review the following in the light of further 630 thoughts on the associated signaling protocol(s). I am fairly 631 confident that we need all the fields other than SFL Batch and SFL 632 Index. The Index is useful in order to map between the label and 633 information associated with the FEC. The batch is part of the 634 lifetime management process. 636 The required RFC6374 SFL TLV is shown in Figure 6. This contains the 637 SFL that was carried in the label stack, the FEC that was used to 638 allocate the SFL and the index into the batch of SLs that were 639 allocated for the FEC that corresponds to this SFL. 641 0 1 2 3 642 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 1 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | Type | Length |MBZ| SFL Batch | SFL Index | 645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 646 | SFL | Reserved | 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 648 | FEC | 649 . . 650 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 652 Figure 6: SFL TLV 654 Where: 656 Type Type is set to Synonymous Flow Label (SFL-TLV). 658 Length The length of the TLV as specified in RFC6374. 660 MBZ MUST be sent as zero and ignored on receive. 662 SFL Batch The SFL batch that this SFL was allocated as part 663 of see [I-D.bryant-mpls-sfl-control] 665 SPL Index The index into the list of SFLs that were assigned 666 against the FEC that corresponds to the SFL. 668 SFL The SFL used to deliver this packet. This is an MPLS 669 label which is a component of a label stack entry as 670 defined in Section 2.1 of [RFC3032]. 672 Reserved MUST be sent as zero and ignored on receive. 674 FEC The Forwarding Equivalence Class that was used to 675 request this SFL. This is encoded as per 676 Section 3.4.1 of TBD 678 This information is needed to allow for operation with hardware that 679 discards the MPLS label stack before passing the remainder of the 680 stack to the OAM handler. By providing both the SFL and the FEC plus 681 index into the array of allocated SFLs a number of implementation 682 types are supported. 684 10. Applicability to Pro-active and On-demand Measurement 686 A future version of the this document will discuss the applicability 687 of the various methods to pro-active and on-demand Measurement. 689 11. RFC6374 Combined Loss-Delay Measurement 691 This mode of operation is not currently supported by this 692 specification. 694 12. Privacy Considerations 696 The inclusion of originating and/or flow information in a packet 697 provides more identity information and hence potentially degrades the 698 privacy of the communication. Whilst the inclusion of the additional 699 granularity does allow greater insight into the flow characteristics 700 it does not specifically identify which node originated the packet 701 other than by inspection of the network at the point of ingress, or 702 inspection of the control protocol packets. This privacy threat may 703 be mitigated by encrypting the control protocol packets, regularly 704 changing the synonymous labels and by concurrently using a number of 705 such labels. 707 13. Security Considerations 709 The issue noted in Section 5 is a security consideration. There are 710 no other new security issues associated with the MPLS dataplane. Any 711 control protocol used to request SFLs will need to ensure the 712 legitimacy of the request. 714 14. IANA Considerations 716 14.1. Allocation of PW Associated Channel Type 718 As per the IANA considerations in [RFC5586], IANA is requested to 719 allocate the following Channel Type in the "PW Associated Channel 720 Type" registry: 722 Value Description TLV Follows Reference 723 ----- --------------------------------- ----------- --------- 724 TBD RFC6374 Bucket Jitter Measurement No This 726 TBD RFC6374 Multi-Packet Delay No This 727 Measurement 729 TBD RFC6374 Average Delay Measurement No This 731 14.2. MPLS Loss/Delay TLV Object 733 IANA is request to allocate a new TLV from the 0-127 range on the 734 MPLS Loss/Delay Measurement TLV Object Registry: 736 Type Description Reference 737 ---- --------------------------------- --------- 738 TBD Synonymous Flow Label This 740 A value of 4 is recommended. 742 RFC Editor please delete this line 743 [RFC3032][I-D.bryant-mpls-sfl-control] 745 15. References 747 15.1. Normative References 749 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 750 Requirement Levels", BCP 14, RFC 2119, 751 DOI 10.17487/RFC2119, March 1997, 752 . 754 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 755 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 756 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, 757 . 759 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 760 "MPLS Generic Associated Channel", RFC 5586, 761 DOI 10.17487/RFC5586, June 2009, 762 . 764 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 765 Measurement for MPLS Networks", RFC 6374, 766 DOI 10.17487/RFC6374, September 2011, 767 . 769 [RFC7876] Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path 770 for Packet Loss and Delay Measurement for MPLS Networks", 771 RFC 7876, DOI 10.17487/RFC7876, July 2016, 772 . 774 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 775 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 776 May 2017, . 778 15.2. Informative References 780 [I-D.bryant-mpls-sfl-control] 781 Bryant, S., Swallow, G., and S. Sivabalan, "A Simple 782 Control Protocol for MPLS SFLs", draft-bryant-mpls-sfl- 783 control-06 (work in progress), January 2020. 785 [I-D.ietf-mpls-sfl-framework] 786 Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., 787 and G. Mirsky, "Synonymous Flow Label Framework", draft- 788 ietf-mpls-sfl-framework-06 (work in progress), October 789 2019. 791 [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, 792 P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi- 793 Protocol Label Switching (MPLS) Support of Differentiated 794 Services", RFC 3270, DOI 10.17487/RFC3270, May 2002, 795 . 797 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 798 L., and L. Berger, "A Framework for MPLS in Transport 799 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 800 . 802 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 803 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 804 "Alternate-Marking Method for Passive and Hybrid 805 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 806 January 2018, . 808 [RFC8372] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. 809 Mirsky, "MPLS Flow Identification Considerations", 810 RFC 8372, DOI 10.17487/RFC8372, May 2018, 811 . 813 Authors' Addresses 815 Stewart Bryant 816 Futurewei Technologies Inc. 818 Email: sb@stewartbryant.com 820 Stewart Bryant 821 Futurewei Technologies Inc. 823 Email: stewart.bryant@gmail.com 825 Mach Chen 826 Huawei 828 Email: mach.chen@huawei.com 830 Zhenbin Li 831 Huawei 833 Email: lizhenbin@huawei.com 834 George Swallow 835 Southend Technical Center 837 Email: swallow.ietf@gmail.com 839 Siva Sivabalan 840 Cisco Systems 842 Email: msiva@cisco.com 844 Gregory Mirsky 845 ZTE Corp. 847 Email: gregimirsky@gmail.com 849 Giuseppe Fioccola 850 Huawei Technologies 852 Email: giuseppe.fioccola@huawei.com