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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-09) exists of draft-bryant-mpls-sfl-control-07 == Outdated reference: A later version (-11) exists of draft-ietf-mpls-sfl-framework-07 -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted by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 (Ed) 3 Internet-Draft Futurewei Technologies Inc. 4 Intended status: Standards Track G. Swallow 5 Expires: December 10, 2020 Southend Technical Center 6 M. Chen 7 Huawei 8 G. Fioccola 9 Huawei Technologies 10 G. Mirsky 11 ZTE Corp. 12 June 08, 2020 14 RFC6374 Synonymous Flow Labels 15 draft-ietf-mpls-rfc6374-sfl-07 17 Abstract 19 This document describes a method of making RFC6374 performance 20 measurements on flows carried over an MPLS Label Switched path. This 21 allows loss and delay measurements to be made on multi-point to point 22 LSPs and allows the measurement of flows within an MPLS construct 23 using RFC6374. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on December 10, 2020. 42 Copyright Notice 44 Copyright (c) 2020 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 61 3. RFC6374 Packet Loss Measurement with SFL . . . . . . . . . . 4 62 4. RFC6374 Single Packet Delay Measurement . . . . . . . . . . . 4 63 5. Data Service Packet Delay Measurement . . . . . . . . . . . . 4 64 6. Some Simplifying Rules . . . . . . . . . . . . . . . . . . . 6 65 7. Multiple Packet Delay Characteristics . . . . . . . . . . . . 6 66 7.1. Method 1: Time Buckets . . . . . . . . . . . . . . . . . 7 67 7.2. Method 2 Classic Standard Deviation . . . . . . . . . . . 9 68 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 10 69 7.3. Per Packet Delay Measurement . . . . . . . . . . . . . . 11 70 7.4. Average Delay . . . . . . . . . . . . . . . . . . . . . . 11 71 8. Sampled Measurement . . . . . . . . . . . . . . . . . . . . . 13 72 9. Carrying RFC6374 Packets over an LSP using an SFL . . . . . . 13 73 9.1. RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . . 15 74 10. Applicability to Pro-active and On-demand Measurement . . . . 16 75 11. RFC6374 Combined Loss-Delay Measurement . . . . . . . . . . . 16 76 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16 77 13. Security Considerations . . . . . . . . . . . . . . . . . . . 17 78 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 79 14.1. Allocation of PW Associated Channel Type . . . . . . . . 17 80 14.2. MPLS Loss/Delay TLV Object . . . . . . . . . . . . . . . 17 81 15. Contributing Authors . . . . . . . . . . . . . . . . . . . . 18 82 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 83 16.1. Normative References . . . . . . . . . . . . . . . . . . 18 84 16.2. Informative References . . . . . . . . . . . . . . . . . 18 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 87 1. Introduction 89 [RFC6374] was originally designed for use as an OAM protocol for use 90 with MPLS Transport Profile (MPLS-TP) [RFC5921] LSPs. MPLS-TP only 91 supports point-to-point and point-to-multi-point LSPs. This document 92 describes how to use RFC6374 in the general MPLS case, and also 93 introduces a number of more sophisticated measurements of 94 applicability to both cases. 96 [RFC8372] describes the requirement for introducing flow identities 97 when using RFC6374 [RFC6374] packet Loss Measurements (LM). In 98 summary RFC6374 uses the loss-measurement (LM) packet as the packet 99 accounting demarcation point. Unfortunately this gives rise to a 100 number of problems that may lead to significant packet accounting 101 errors in certain situations. For example: 103 1. Where a flow is subjected to Equal Cost Multi-Path (ECMP) 104 treatment packets can arrive out of order with respect to the LM 105 packet. 107 2. Where a flow is subjected to ECMP treatment, packets can arrive 108 at different hardware interfaces, thus requiring reception of an 109 LM packet on one interface to trigger a packet accounting action 110 on a different interface which may not be co-located with it. 111 This is a difficult technical problem to address with the 112 required degree of accuracy. 114 3. Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs 115 and PWs) local processing may be distributed over a number of 116 processor cores, leading to synchronization problems. 118 4. Link aggregation techniques may also lead to synchronization 119 issues. 121 5. Some forwarder implementations have a long pipeline between 122 processing a packet and incrementing the associated counter again 123 leading to synchronization difficulties. 125 An approach to mitigating these synchronization issue is described in 126 [RFC8321] in which packets are batched by the sender and each batch 127 is marked in some way such that adjacent batches can be easily 128 recognized by the receiver. 130 An additional problem arises where the LSP is a multi-point to point 131 LSP, since MPLS does not include a source address in the packet. 132 Network management operations require the measurement of packet loss 133 between a source and destination. It is thus necessary to introduce 134 some source specific information into the packet to identify packet 135 batches from a specific source. 137 [I-D.ietf-mpls-sfl-framework] describes a method of encoding per flow 138 instructions in an MPLS label stack using a technique called 139 Synonymous Flow Labels (SFL) in which labels which mimic the 140 behaviour of other labels provide the packet batch identifiers and 141 enable the per batch packet accounting. This memo specifies how SFLs 142 are used to perform RFC6374 packet loss and RFC6374 delay 143 measurements. 145 2. Requirements Language 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 149 "OPTIONAL" in this document are to be interpreted as described in BCP 150 14 [RFC2119] [RFC8174] when, and only when, they appear in all 151 capitals, as shown here. 153 3. RFC6374 Packet Loss Measurement with SFL 155 The data service packets of the flow being instrumented are grouped 156 into batches, and all the packets within a batch are marked with the 157 SFL [RFC8372] corresponding to that batch. The sender counts the 158 number of packets in the batch. When the batch has completed and the 159 sender is confident that all of the packets in that batch will have 160 been received, the sender issues an RFC6374 Query message to 161 determine the number actually received and hence the number of 162 packets lost. The RFC6374 Query message is sent using the same SFL 163 as the co-responding batch of data service packets. The format of 164 the Query and Response packet is described in Section 9. 166 4. RFC6374 Single Packet Delay Measurement 168 RFC6374 describes how to measure the packet delay by measuring the 169 transit time of an RFC6374 packet over an LSP. Such a packet may not 170 need to be carried over an SFL since the delay over a particular LSP 171 should be a function of the TC bits. 173 However, where SFLs are being used to monitor packet loss or where 174 label inferred scheduling is used [RFC3270] then the SFL would be 175 REQUIRED to ensure that the RFC6374 packet which was being used as a 176 proxy for a data service packet experienced a representative delay. 177 The format of an RFC6374 packet carried over the LSP using an SFL is 178 shown in Section 9. 180 5. Data Service Packet Delay Measurement 182 Where it is desired to more thoroughly instrument a packet flow and 183 to determine the delay of a number of packets it is undesirable to 184 send a large number of RFC6374 packets acting as proxy data service 185 packets Section 4. A method of directly measuring the delay 186 characteristics of a batch of packets is therefore needed. 188 Given the long intervals over which it is necessary to measure packet 189 loss, it is not necessarily the case that the batch times for the two 190 measurement types would be identical. This it is proposed that the 191 two measurements are relatively independent. The notion that they 192 are relatively independent arises for the potential for the two 193 batches to overlap in time, in which case either the delay batch time 194 will need to be cut short or the loss time will need to be extended 195 to allow correct reconciliation of the various counters. 197 The problem is illustrated in Figure 1 below: 199 (1) AAAAAAAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 201 SFL Marking of a packet batch for loss measurement 203 (2) AADDDDAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 205 SFL Marking of a subset if the packets for delay 207 (3) AAAAAAAADDDDBBBBBBBBAAAAAAAAAABBBBBBBBBB 209 SFL Marking of a subset of the packets across a 210 packet loss measurement boundary 212 (4) AACDCDCDAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 214 The case of multiple delay measurements within 215 a packet loss measurement 217 Figure 1: RFC6734 Query Packet with SFL 219 In case 1 of Figure 1 we show the case were loss measurement alone is 220 being carried out on the flow under analysis. For illustrative 221 purposes consider that in the time interval being analyzed, 10 222 packets always flow. 224 Now consider case 2 of Figure 1 where a small batch of packets need 225 to analyzed for delay. These are marked with a different SFL type 226 indicating that they are to be monitored for both loss and delay. 227 The SFL=A indicates loss batch A, SFL=D indicates a batch of packets 228 that are to be instrumented for delay, but SFL D is synonymous with 229 SFL A, which in turn is synonymous with the underlying FEC. Thus, a 230 packet marked D will be accumulated into the A loss batch, into the 231 delay statistics and will be forwarded as normal. Whether the packet 232 is actually counted twice (for loss and delay) or whether the two 233 counters are reconciled during reporting is a local matter. 235 Now consider case 3 of Figure 1 where a small batch of packets are 236 marked for delay across a loss batch boundary. These packets need to 237 considered as part of batch A or a part of batch B, and any RFC6374 238 Query needs to take place after all the packets A or D (which ever 239 option is chosen) have arrived at the receiving LSR. 241 Now consider case 4 of Figure 1. Here we have a case where it is 242 required to take a number of delay measurements within a batch of 243 packets that we are measuring for loss. To do this we need two SFLs 244 for delay (C and D) and alternate between them (on a delay batch by 245 delay batch basis) for the purposes of measuring the delay 246 characteristics of the different batches of packets. 248 6. Some Simplifying Rules 250 It is possible to construct a large set of overlapping measurement 251 type, in terms of loss, delay, loss and delay and batch overlap. If 252 we allow all combination of cases, this leads to configuration, 253 testing and implementation complexity and hence increased operation 254 and capital cost. The following simplifying rules represent the 255 default case: 257 1. Any system that needs to measure delay MUST be able to measure 258 loss. 260 2. Any system that is to measure delay MUST be configured to measure 261 loss. Whether the loss statistics are collected or not is a 262 local matter. 264 3. A delay measurement MAY start at any point during a loss 265 measurement batch, subject to rule 4. 267 4. A delay measurement interval MUST be short enough that it will 268 complete before the enclosing loss batch completes. 270 5. The duration of a second delay (D in Figure 1 batch must be such 271 that all packets from the packets belonging to a first delay 272 batch (C in Figure 1)will have been received before the second 273 delay batch completes. 275 Given that the sender controls both the start and duration of a loss 276 and a delay packet batch, these rules are readily implemented in the 277 control plane. 279 7. Multiple Packet Delay Characteristics 281 A number of methods are described. The expectation is that the MPLS 282 WG possibly with the assistance of the IPPM WG will select one or 283 maybe more than one of these methods for standardization. 285 Three Methods are discussed: 287 1. Time Buckets 288 2. Classic Standard Deviation 290 3. Average Delay 292 7.1. Method 1: Time Buckets 294 In this method the receiving LSR measures the inter-packet gap, 295 classifies the delay into a number of delay buckets and records the 296 number of packets in each bucket. As an example, if the operator 297 were concerned about packets with a delay of up to 1us, 2us, 4us, 298 8us, and over 8us then there would be five buckets and packets that 299 arrived up to 1us would cause the 1us bucket counter to increase, 300 between 1us and 2us the 2us bucket counter would increase etc. In 301 practice it might be better in terms of processing and potential 302 parallelism if, when a packet had a delay relative to its predecessor 303 of 2us both the up to 1us and the 2us counter were incremented and 304 any more detailed information was calculated in the analytics system. 306 This method allows the operator to see more structure in the jitter 307 characteristics than simply measuring the average jitter, and avoids 308 the complication of needing to perform a per packet multiply, but 309 will probably need to time intervals between buckets to be 310 programmable by the operator. 312 The packet format of an RFC6374 Bucket Jitter Measurement Message is 313 shown below: 315 0 1 2 3 316 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 1 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 |Version| Flags | Control Code | Message Length | 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | QTF | RTF | RPTF | Reserved | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | Session Identifier | DS | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | Number of | Reserved | 325 | Buckets | | 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 | Interval in 10ns units | 328 | | 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 330 | Number pkts in Bucket | 331 | | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 ~ ~ 334 ~ ~ 335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 336 ~ ~ 337 ~ TLV Block ~ 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 Figure 2: Bucket Jitter Measurement Message Format 342 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 343 Session Identifier, and DS Fields are as defined in section 3.7 of 344 RFC6374. The remaining fields are as follows: 346 o Number of Buckets in the measurement 348 o Reserved must be sent as zero and ignored on receipt 350 o Interval in 10ns units is the inter-packet interval for 351 this bucket 353 o Number Pkts in Bucket is the number of packets found in 354 this bucket. 356 There will be a number of Interval/Number pairs depending on the 357 number of buckets being specified by the Querier. If an RFC6374 358 message is being used to configure the buckets, (i.e. the responder 359 is creating or modifying the buckets according to the intervals in 360 the Query message), then the Responder MUST respond with 0 packets in 361 each bucket until it has been configured for a full measurement 362 period. This indicates that it was configured at the time of the 363 last response message, and thus the response is valid for the whole 364 interval. As per the [RFC6374] convention the Number of pkts in 365 Bucket fields are included in the Query message and set to zero. 367 Out of band configuration is permitted by this mode of operation. 369 Note this is a departure from the normal fixed format used in 370 RFC6374. 372 This RFC6374 message is carried over an LSP in the way described in 373 [RFC6374] and over an LSP with an SFL as described in Section 9. 375 7.2. Method 2 Classic Standard Deviation 377 In this method, provision is made for reporting the following delay 378 characteristics: 380 1. Number of packets in the batch (n). 382 2. Sum of delays in a batch (S) 384 3. Maximum Delay. 386 4. Minimum Delay. 388 5. Sum of squares of Inter-packet delay (SS). 390 Characteristic's 1 and 2 give the mean delay. Measuring the delay of 391 each pair in the batch is discussed in Section 7.3. 393 Characteristics 3 and 4 give the outliers. 395 Characteristics 1, 2 and 5 can be used to calculate the variance of 396 the inter-packet gap and hence the standard deviation giving a view 397 of the distribution of packet delays and hence the jitter. The 398 equation for the variance (var) is given by: 400 var = (SS - S*S/n)/(n-1) 402 There is some concern over the use of this algorithm for measuring 403 variance, because SS and S*S/n can be similar numbers, particularly 404 where variance is low. However the method commends it self by not 405 requiring a division in the hardware. 407 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 409 The packet format of an RFC6374 Multi-Packet Delay Measurement 410 Message is shown below: 412 0 1 2 3 413 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 1 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 |Version| Flags | Control Code | Message Length | 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | QTF | RTF | RPTF | Reserved | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 | Session Identifier | DS | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 | Number of Packets | 422 | | 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 424 | Sum of Delays for Batch | 425 | | 426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 427 | Minimum Delay | 428 | | 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 | Maximum Delay | 431 | | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | Sum of squares of Inter-packet delay | 434 | | 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 436 ~ ~ 437 ~ TLV Block ~ 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 Figure 3: Multi-packet Delay Measurement Message Format 442 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 443 Session Identifier, and DS Fields are as defined in section 3.7 of 444 RFC6374. The remaining fields are as follows: 446 o Number of Packets is the number of packets in this batch 448 o Sum of Delays for Batch is the duration of the batch in the 449 time measurement format specified in the RTF field. 451 o Minimum Delay is the minimum inter-packet gap observed during 452 the batch in the time format specified in the RTF field. 454 o Maximum Delay is the maximum inter-packet gap observed during 455 the batch in the time format specified in the RTF field. 457 This RFC6374 message is carried over an LSP in the way described in 458 [RFC6374] and over an LSP with an SFL as described in Section 9. 460 7.3. Per Packet Delay Measurement 462 If detailed packet delay measurement is required then it might be 463 possible to record the inter-packet gap for each packet pair. In 464 other that exception cases of slow flows or small batch sizes, this 465 would create a large demand on storage in the instrumentation system, 466 bandwidth to such a storage system and bandwidth to the analytics 467 system. Such a measurement technique is outside the scope of this 468 document. 470 7.4. Average Delay 472 Introduced in [RFC8321] is the concept of a one way delay measurement 473 in which the average time of arrival of a set of packets is measured. 474 In this approach the packet is time-stamped at arrival and the 475 Responder returns the sum of the time-stamps and the number of times- 476 tamps. From this the analytics engine can determine the mean delay. 477 An alternative model is that the Responder returns the time stamp of 478 the first and last packet and the number of packets. This method has 479 the advantage of allowing the average delay to be determined at a 480 number of points along the packet path and allowing the components of 481 the delay to be characterized. 483 The packet format of an RFC6374 Average Delay Measurement Message is 484 shown below: 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 |Version| Flags | Control Code | Message Length | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | QTF | RTF | RPTF | Reserved | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 | Session Identifier | DS | 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 | Number of Packets | 496 | | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 | Time of First Packet | 499 | | 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 501 | Time of Last Packet | 502 | | 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 504 | Sum of Timestamps of Batch | 505 | | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 ~ ~ 509 ~ TLV Block ~ 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 Figure 4: Average Delay Measurement Message Format 514 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 515 Session Identifier, and DS Fields are as defined in section 3.7 of 516 RFC6374. The remaining fields are as follows: 518 o Number of Packets is the number of packets in this batch. 520 o Time of First Packet is the time of arrival of the first 521 packet in the batch. 523 o Time of Last Packet is the time of arrival of the last 524 packet in the batch. 526 o Sum of Timestamps of Batch. 528 This RFC6374 message is carried over an LSP in the way described in 529 [RFC6374] and over an LSP with an SFL as described in Section 9. As 530 is the convention with RFC6374, the Query message contains 531 placeholders for the Response message. The placeholders are sent as 532 zero. 534 8. Sampled Measurement 536 In the discussion so far it has been assumed that we would measure 537 the delay characteristics of every packet in a delay measurement 538 interval defined by an SL of constant colour. In [RFC8321] the 539 concept of a sampled measurement is considered. That is the 540 Responder only measures a packet at the start of a group of packets 541 being marked for delay measurement by a particular colour, rather 542 than every packet in the marked batch. A measurement interval is not 543 defined by the duration of a marked batch of packets but the interval 544 between a pair of RFC6374 packets taking a readout of the delay 545 characteristic. This approach has the advantage that the measurement 546 is not impacted by ECMP effects. 548 9. Carrying RFC6374 Packets over an LSP using an SFL 550 The packet format of an RFC6374 Query message using SFLs is shown in 551 Figure 5. 553 +-------------------------------+ 554 | | 555 | LSP | 556 | Label | 557 +-------------------------------+ 558 | | 559 | Synonymous Flow | 560 | Label | 561 +-------------------------------+ 562 | | 563 | GAL | 564 | | 565 +-------------------------------+ 566 | | 567 | ACH Type = 0xA | 568 | | 569 +-------------------------------+ 570 | | 571 | RFC6374 Measurement Message | 572 | | 573 | +-------------------------+ | 574 | | | | 575 | | RFC6374 Fixed | | 576 | | Header | | 577 | | | | 578 | +-------------------------+ | 579 | | | | 580 | | Optional SFL TLV | | 581 | | | | 582 | +-------------------------+ | 583 | | | | 584 | | Optional Return | | 585 | | Information | | 586 | | | | 587 | +-------------------------+ | 588 | | 589 +-------------------------------+ 591 Figure 5: RFC6734 Query Packet with SFL 593 The MPLS label stack is exactly the same as that used for the user 594 data service packets being instrumented except for the inclusion of 595 the GAL [RFC5586] to allow the receiver to distinguish between normal 596 data packets and OAM packets. Since the packet loss measurements are 597 being made on the data service packets, an RFC6374 direct loss 598 measurement is being made, and which is indicated by the type field 599 in the ACH (Type = 0x000A). 601 The RFC6374 measurement message consists of the three components, the 602 RFC6374 fixed header as specified in [RFC6374] carried over the ACH 603 channel type specified the type of measurement being made (currently: 604 loss, delay or loss and delay) as specified in RFC6374. 606 Two optional TLVs MAY also be carried if needed. The first is the 607 SFL TLV specified in Section 9.1. This is used to provide the 608 implementation with a reminder of the SFL that was used to carry the 609 RFC6374 message. This is needed because a number of MPLS 610 implementations do not provide the MPLS label stack to the MPLS OAM 611 handler. This TLV is required if RFC6374 messages are sent over UDP 612 [RFC7876]. This TLV MUST be included unless, by some method outside 613 the scope of this document, it is known that this information is not 614 needed by the RFC6374 Responder. 616 The second set of information that may be needed is the return 617 information that allows the responder send the RFC6374 response to 618 the Querier. This is not needed if the response is requested in-band 619 and the MPLS construct being measured is a point to point LSP, but 620 otherwise MUST be carried. The return address TLV is defined in 621 RFC6378 and the optional UDP Return Object is defined in [RFC7876]. 623 9.1. RFC6374 SFL TLV 625 Editor's Note we need to review the following in the light of further 626 thoughts on the associated signaling protocol(s). I am fairly 627 confident that we need all the fields other than SFL Batch and SFL 628 Index. The Index is useful in order to map between the label and 629 information associated with the FEC. The batch is part of the 630 lifetime management process. 632 The required RFC6374 SFL TLV is shown in Figure 6. This contains the 633 SFL that was carried in the label stack, the FEC that was used to 634 allocate the SFL and the index into the batch of SLs that were 635 allocated for the FEC that corresponds to this SFL. 637 0 1 2 3 638 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 1 639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 | Type | Length |MBZ| SFL Batch | SFL Index | 641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 | SFL | Reserved | 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | FEC | 645 . . 646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 648 Figure 6: SFL TLV 650 Where: 652 Type Type is set to Synonymous Flow Label (SFL-TLV). 654 Length The length of the TLV as specified in RFC6374. 656 MBZ MUST be sent as zero and ignored on receive. 658 SFL Batch The SFL batch that this SFL was allocated as part 659 of see [I-D.bryant-mpls-sfl-control] 661 SPL Index The index into the list of SFLs that were assigned 662 against the FEC that corresponds to the SFL. 664 SFL The SFL used to deliver this packet. This is an MPLS 665 label which is a component of a label stack entry as 666 defined in Section 2.1 of [RFC3032]. 668 Reserved MUST be sent as zero and ignored on receive. 670 FEC The Forwarding Equivalence Class that was used to 671 request this SFL. This is encoded as per 672 Section 3.4.1 of TBD 674 This information is needed to allow for operation with hardware that 675 discards the MPLS label stack before passing the remainder of the 676 stack to the OAM handler. By providing both the SFL and the FEC plus 677 index into the array of allocated SFLs a number of implementation 678 types are supported. 680 10. Applicability to Pro-active and On-demand Measurement 682 A future version of the this document will discuss the applicability 683 of the various methods to pro-active and on-demand Measurement. 685 11. RFC6374 Combined Loss-Delay Measurement 687 This mode of operation is not currently supported by this 688 specification. 690 12. Privacy Considerations 692 The inclusion of originating and/or flow information in a packet 693 provides more identity information and hence potentially degrades the 694 privacy of the communication. Whilst the inclusion of the additional 695 granularity does allow greater insight into the flow characteristics 696 it does not specifically identify which node originated the packet 697 other than by inspection of the network at the point of ingress, or 698 inspection of the control protocol packets. This privacy threat may 699 be mitigated by encrypting the control protocol packets, regularly 700 changing the synonymous labels and by concurrently using a number of 701 such labels. 703 13. Security Considerations 705 The issue noted in Section 5 is a security consideration. There are 706 no other new security issues associated with the MPLS dataplane. Any 707 control protocol used to request SFLs will need to ensure the 708 legitimacy of the request. 710 14. IANA Considerations 712 14.1. Allocation of PW Associated Channel Type 714 As per the IANA considerations in [RFC5586], IANA is requested to 715 allocate the following Channel Type in the "PW Associated Channel 716 Type" registry: 718 Value Description TLV Follows Reference 719 ----- --------------------------------- ----------- --------- 720 TBD RFC6374 Bucket Jitter Measurement No This 722 TBD RFC6374 Multi-Packet Delay No This 723 Measurement 725 TBD RFC6374 Average Delay Measurement No This 727 14.2. MPLS Loss/Delay TLV Object 729 IANA is request to allocate a new TLV from the 0-127 range on the 730 MPLS Loss/Delay Measurement TLV Object Registry: 732 Type Description Reference 733 ---- --------------------------------- --------- 734 TBD Synonymous Flow Label This 736 A value of 4 is recommended. 738 RFC Editor please delete this line 739 [RFC3032][I-D.bryant-mpls-sfl-control] 741 15. Contributing Authors 743 Zhenbin Li 744 Huawei 745 Email: lizhenbin@huawei.com 747 Siva Sivabalan 748 Ciena Corporation 749 Email: ssivabal@ciena.com 751 16. References 753 16.1. Normative References 755 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 756 Requirement Levels", BCP 14, RFC 2119, 757 DOI 10.17487/RFC2119, March 1997, 758 . 760 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 761 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 762 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, 763 . 765 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 766 "MPLS Generic Associated Channel", RFC 5586, 767 DOI 10.17487/RFC5586, June 2009, 768 . 770 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 771 Measurement for MPLS Networks", RFC 6374, 772 DOI 10.17487/RFC6374, September 2011, 773 . 775 [RFC7876] Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path 776 for Packet Loss and Delay Measurement for MPLS Networks", 777 RFC 7876, DOI 10.17487/RFC7876, July 2016, 778 . 780 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 781 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 782 May 2017, . 784 16.2. Informative References 786 [I-D.bryant-mpls-sfl-control] 787 Bryant, S., Swallow, G., and S. Sivabalan, "A Simple 788 Control Protocol for MPLS SFLs", draft-bryant-mpls-sfl- 789 control-07 (work in progress), June 2020. 791 [I-D.ietf-mpls-sfl-framework] 792 Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., 793 and G. Mirsky, "Synonymous Flow Label Framework", draft- 794 ietf-mpls-sfl-framework-07 (work in progress), June 2020. 796 [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, 797 P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi- 798 Protocol Label Switching (MPLS) Support of Differentiated 799 Services", RFC 3270, DOI 10.17487/RFC3270, May 2002, 800 . 802 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 803 L., and L. Berger, "A Framework for MPLS in Transport 804 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 805 . 807 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 808 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 809 "Alternate-Marking Method for Passive and Hybrid 810 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 811 January 2018, . 813 [RFC8372] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. 814 Mirsky, "MPLS Flow Identification Considerations", 815 RFC 8372, DOI 10.17487/RFC8372, May 2018, 816 . 818 Authors' Addresses 820 Stewart Bryant 821 Futurewei Technologies Inc. 823 Email: sb@stewartbryant.com 825 George Swallow 826 Southend Technical Center 828 Email: swallow.ietf@gmail.com 829 Mach Chen 830 Huawei 832 Email: mach.chen@huawei.com 834 Giuseppe Fioccola 835 Huawei Technologies 837 Email: giuseppe.fioccola@huawei.com 839 Gregory Mirsky 840 ZTE Corp. 842 Email: gregimirsky@gmail.com