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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-09) exists of draft-bryant-mpls-sfl-control-02 == Outdated reference: A later version (-11) exists of draft-ietf-mpls-sfl-framework-03 -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted by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 M. Chen 4 Intended status: Standards Track Z. Li 5 Expires: June 15, 2019 Huawei 6 G. Swallow 7 Southend Technical Center 8 S. Sivabalan 9 Cisco Systems 10 G. Mirsky 11 ZTE Corp. 12 G. Fioccola 13 Huawei Technologies 14 December 12, 2018 16 RFC6374 Synonymous Flow Labels 17 draft-ietf-mpls-rfc6374-sfl-03 19 Abstract 21 This document describes a method of making RFC6374 performance 22 measurements on flows carried over an MPLS Label Switched path. This 23 allows loss and delay measurements to be made on multi-point to point 24 LSPs and allows the measurement of flows within an MPLS construct 25 using RFC6374. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on June 15, 2019. 44 Copyright Notice 46 Copyright (c) 2018 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 63 3. RFC6374 Packet Loss Measurement with SFL . . . . . . . . . . 4 64 4. RFC6374 Single Packet Delay Measurement . . . . . . . . . . . 4 65 5. Data Service Packet Delay Measurement . . . . . . . . . . . . 4 66 6. Some Simplifying Rules . . . . . . . . . . . . . . . . . . . 6 67 7. Multiple Packet Delay Characteristics . . . . . . . . . . . . 6 68 7.1. Method 1: Time Buckets . . . . . . . . . . . . . . . . . 7 69 7.2. Method 2 Classic Standard Deviation . . . . . . . . . . . 9 70 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 10 71 7.3. Per Packet Delay Measurement . . . . . . . . . . . . . . 11 72 7.4. Average Delay . . . . . . . . . . . . . . . . . . . . . . 11 73 8. Sampled Measurement . . . . . . . . . . . . . . . . . . . . . 13 74 9. Carrying RFC6374 Packets over an LSP using an SFL . . . . . . 13 75 9.1. RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . . 15 76 10. Applicability to Pro-active and On-demand Measurement . . . . 16 77 11. RFC6374 Combined Loss-Delay Measurement . . . . . . . . . . . 16 78 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16 79 13. Security Considerations . . . . . . . . . . . . . . . . . . . 17 80 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 81 14.1. Allocation of PW Associated Channel Type . . . . . . . . 17 82 14.2. MPLS Loss/Delay TLV Object . . . . . . . . . . . . . . . 17 83 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 84 15.1. Normative References . . . . . . . . . . . . . . . . . . 18 85 15.2. Informative References . . . . . . . . . . . . . . . . . 18 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 88 1. Introduction 90 [RFC6374] was originally designed for use as an OAM protocol for use 91 with MPLS Transport Profile (MPLS-TP) [RFC5921] LSPs. MPLS-TP only 92 supports point-to-point and point-to-multi-point LSPs. This document 93 describes how to use RFC6374 in the general MPLS case, and also 94 introduces a number of more sophisticated measurements of 95 applicability to both cases. 97 [RFC8372] describes the requirement for introducing flow identities 98 when using RFC6374 [RFC6374] packet Loss Measurements (LM). In 99 summary RFC6374 uses the loss-measurement (LM) packet as the packet 100 accounting demarcation point. Unfortunately this gives rise to a 101 number of problems that may lead to significant packet accounting 102 errors in certain situations. For example: 104 1. Where a flow is subjected to Equal Cost Multi-Path (ECMP) 105 treatment packets can arrive out of order with respect to the LM 106 packet. 108 2. Where a flow is subjected to ECMP treatment, packets can arrive 109 at different hardware interfaces, thus requiring reception of an 110 LM packet on one interface to trigger a packet accounting action 111 on a different interface which may not be co-located with it. 112 This is a difficult technical problem to address with the 113 required degree of accuracy. 115 3. Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs 116 and PWs) local processing may be distributed over a number of 117 processor cores, leading to synchronization problems. 119 4. Link aggregation techniques may also lead to synchronization 120 issues. 122 5. Some forwarder implementations have a long pipeline between 123 processing a packet and incrementing the associated counter again 124 leading to synchronization difficulties. 126 An approach to mitigating these synchronization issue is described in 127 [RFC8321] in which packets are batched by the sender and each batch 128 is marked in some way such that adjacent batches can be easily 129 recognized by the receiver. 131 An additional problem arises where the LSP is a multi-point to point 132 LSP, since MPLS does not include a source address in the packet. 133 Network management operations require the measurement of packet loss 134 between a source and destination. It is thus necessary to introduce 135 some source specific information into the packet to identify packet 136 batches from a specific source. 138 [I-D.ietf-mpls-sfl-framework] describes a method of encoding per flow 139 instructions in an MPLS label stack using a technique called 140 Synonymous Flow Labels (SFL) in which labels which mimic the 141 behaviour of other labels provide the packet batch identifiers and 142 enable the per batch packet accounting. This memo specifies how SFLs 143 are used to perform RFC6374 packet loss and RFC6374 delay 144 measurements. 146 2. Requirements Language 148 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 149 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 150 "OPTIONAL" in this document are to be interpreted as described in BCP 151 14 [RFC2119] [RFC8174] when, and only when, they appear in all 152 capitals, as shown here. 154 3. RFC6374 Packet Loss Measurement with SFL 156 The data service packets of the flow being instrumented are grouped 157 into batches, and all the packets within a batch are marked with the 158 SFL [RFC8372] corresponding to that batch. The sender counts the 159 number of packets in the batch. When the batch has completed and the 160 sender is confident that all of the packets in that batch will have 161 been received, the sender issues an RFC6374 Query message to 162 determine the number actually received and hence the number of 163 packets lost. The RFC6374 Query message is sent using the same SFL 164 as the co-responding batch of data service packets. The format of 165 the Query and Response packet is described in Section 9. 167 4. RFC6374 Single Packet Delay Measurement 169 RFC6374 describes how to measure the packet delay by measuring the 170 transit time of an RFC6374 packet over an LSP. Such a packet may not 171 need to be carried over an SFL since the delay over a particular LSP 172 should be a function of the TC bits. 174 However, where SFLs are being used to monitor packet loss or where 175 label inferred scheduling is used [RFC3270] then the SFL would be 176 REQUIRED to ensure that the RFC6374 packet which was being used as a 177 proxy for a data service packet experienced a representative delay. 178 The format of an RFC6374 packet carried over the LSP using an SFL is 179 shown in Section 9. 181 5. Data Service Packet Delay Measurement 183 Where it is desired to more thoroughly instrument a packet flow and 184 to determine the delay of a number of packets it is undesirable to 185 send a large number of RFC6374 packets acting as proxy data service 186 packets Section 4. A method of directly measuring the delay 187 characteristics of a batch of packets is therefore needed. 189 Given the long intervals over which it is necessary to measure packet 190 loss, it is not necessarily the case that the batch times for the two 191 measurement types would be identical. This it is proposed that the 192 two measurements are relatively independent. The notion that they 193 are relatively independent arises for the potential for the two 194 batches to overlap in time, in which case either the delay batch time 195 will need to be cut short or the loss time will need to be extended 196 to allow correct reconciliation of the various counters. 198 The problem is illustrated in Figure 1 below: 200 (1) AAAAAAAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 202 SFL Marking of a packet batch for loss measurement 204 (2) AADDDDAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 206 SFL Marking of a subset if the packets for delay 208 (3) AAAAAAAADDDDBBBBBBBBAAAAAAAAAABBBBBBBBBB 210 SFL Marking of a subset of the packets across a 211 packet loss measurement boundary 213 (4) AACDCDCDAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB 215 The case of multiple delay measurements within 216 a packet loss measurement 218 Figure 1: RFC6734 Query Packet with SFL 220 In case 1 of Figure 1 we show the case were loss measurement alone is 221 being carried out on the flow under analysis. For illustrative 222 purposes consider that in the time interval being analyzed, 10 223 packets always flow. 225 Now consider case 2 of Figure 1 where a small batch of packets need 226 to analyzed for delay. These are marked with a different SFL type 227 indicating that they are to be monitored for both loss and delay. 228 The SFL=A indicates loss batch A, SFL=D indicates a batch of packets 229 that are to be instrumented for delay, but SFL D is synonymous with 230 SFL A, which in turn is synonymous with the underlying FEC. Thus, a 231 packet marked D will be accumulated into the A loss batch, into the 232 delay statistics and will be forwarded as normal. Whether the packet 233 is actually counted twice (for loss and delay) or whether the two 234 counters are reconciled during reporting is a local matter. 236 Now consider case 3 of Figure 1 where a small batch of packets are 237 marked for delay across a loss batch boundary. These packets need to 238 considered as part of batch A or a part of batch B, and any RFC6374 239 Query needs to take place after all the packets A or D (which ever 240 option is chosen) have arrived at the receiving LSR. 242 Now consider case 4 of Figure 1. Here we have a case where it is 243 required to take a number of delay measurements within a batch of 244 packets that we are measuring for loss. To do this we need two SFLs 245 for delay (C and D) and alternate between them (on a delay batch by 246 delay batch basis) for the purposes of measuring the delay 247 characteristics of the different batches of packets. 249 6. Some Simplifying Rules 251 It is possible to construct a large set of overlapping measurement 252 type, in terms of loss, delay, loss and delay and batch overlap. If 253 we allow all combination of cases, this leads to configuration, 254 testing and implementation complexity and hence increased operation 255 and capital cost. The following simplifying rules represent the 256 default case: 258 1. Any system that needs to measure delay MUST be able to measure 259 loss. 261 2. Any system that is to measure delay MUST be configured to measure 262 loss. Whether the loss statistics are collected or not is a 263 local matter. 265 3. A delay measurement MAY start at any point during a loss 266 measurement batch, subject to rule 4. 268 4. A delay measurement interval MUST be short enough that it will 269 complete before the enclosing loss batch completes. 271 5. The duration of a second delay (D in Figure 1 batch must be such 272 that all packets from the packets belonging to a first delay 273 batch (C in Figure 1)will have been received before the second 274 delay batch completes. 276 Given that the sender controls both the start and duration of a loss 277 and a delay packet batch, these rules are readily implemented in the 278 control plane. 280 7. Multiple Packet Delay Characteristics 282 A number of methods are described. The expectation is that the MPLS 283 WG possibly with the assistance of the IPPM WG will select one or 284 maybe more than one of these methods for standardization. 286 Three Methods are discussed: 288 1. Time Buckets 289 2. Classic Standard Deviation 291 3. Average Delay 293 7.1. Method 1: Time Buckets 295 In this method the receiving LSR measures the inter-packet gap, 296 classifies the delay into a number of delay buckets and records the 297 number of packets in each bucket. As an example, if the operator 298 were concerned about packets with a delay of up to 1us, 2us, 4us, 299 8us, and over 8us then there would be five buckets and packets that 300 arrived up to 1us would cause the 1us bucket counter to increase, 301 between 1us and 2us the 2us bucket counter would increase etc. In 302 practice it might be better in terms of processing and potential 303 parallelism if, when a packet had a delay relative to its predecessor 304 of 2us both the up to 1us and the 2us counter were incremented and 305 any more detailed information was calculated in the analytics system. 307 This method allows the operator to see more structure in the jitter 308 characteristics than simply measuring the average jitter, and avoids 309 the complication of needing to perform a per packet multiply, but 310 will probably need to time intervals between buckets to be 311 programmable by the operator. 313 The packet format of an RFC6374 Bucket Jitter Measurement Message is 314 shown below: 316 0 1 2 3 317 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 1 318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 319 |Version| Flags | Control Code | Message Length | 320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 321 | QTF | RTF | RPTF | Reserved | 322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 | Session Identifier | DS | 324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 | Number of | Reserved | 326 | Buckets | | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | Interval in 10ns units | 329 | | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | Number pkts in Bucket | 332 | | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 ~ ~ 335 ~ ~ 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 ~ ~ 338 ~ TLV Block ~ 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 Figure 2: Bucket Jitter Measurement Message Format 343 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 344 Session Identifier, and DS Fields are as defined in section 3.7 of 345 RFC6374. The remaining fields are as follows: 347 o Number of Buckets in the measurement 349 o Reserved must be sent as zero and ignored on receipt 351 o Interval in 10ns units is the inter-packet interval for 352 this bucket 354 o Number Pkts in Bucket is the number of packets found in 355 this bucket. 357 There will be a number of Interval/Number pairs depending on the 358 number of buckets being specified by the Querier. If an RFC6374 359 message is being used to configure the buckets, (i.e. the responder 360 is creating or modifying the buckets according to the intervals in 361 the Query message), then the Responder MUST respond with 0 packets in 362 each bucket until it has been configured for a full measurement 363 period. This indicates that it was configured at the time of the 364 last response message, and thus the response is valid for the whole 365 interval. As per the [RFC6374] convention the Number of pkts in 366 Bucket fields are included in the Query message and set to zero. 368 Out of band configuration is permitted by this mode of operation. 370 Note this is a departure from the normal fixed format used in 371 RFC6374. 373 This RFC6374 message is carried over an LSP in the way described in 374 [RFC6374] and over an LSP with an SFL as described in Section 9. 376 7.2. Method 2 Classic Standard Deviation 378 In this method, provision is made for reporting the following delay 379 characteristics: 381 1. Number of packets in the batch (n). 383 2. Sum of delays in a batch (S) 385 3. Maximum Delay. 387 4. Minimum Delay. 389 5. Sum of squares of Inter-packet delay (SS). 391 Characteristic's 1 and 2 give the mean delay. Measuring the delay of 392 each pair in the batch is discussed in Section 7.3. 394 Characteristics 3 and 4 give the outliers. 396 Characteristics 1, 2 and 5 can be used to calculate the variance of 397 the inter-packet gap and hence the standard deviation giving a view 398 of the distribution of packet delays and hence the jitter. The 399 equation for the variance (var) is given by: 401 var = (SS - S*S/n)/(n-1) 403 There is some concern over the use of this algorithm for measuring 404 variance, because SS and S*S/n can be similar numbers, particularly 405 where variance is low. However the method commends it self by not 406 requiring a division in the hardware. 408 7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 410 The packet format of an RFC6374 Multi-Packet Delay Measurement 411 Message is shown below: 413 0 1 2 3 414 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 1 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 |Version| Flags | Control Code | Message Length | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | QTF | RTF | RPTF | Reserved | 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 | Session Identifier | DS | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 422 | Number of Packets | 423 | | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 | Sum of Delays for Batch | 426 | | 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 | Minimum Delay | 429 | | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | Maximum Delay | 432 | | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | Sum of squares of Inter-packet delay | 435 | | 436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 ~ ~ 438 ~ TLV Block ~ 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 441 Figure 3: Multi-packet Delay Measurement Message Format 443 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 444 Session Identifier, and DS Fields are as defined in section 3.7 of 445 RFC6374. The remaining fields are as follows: 447 o Number of Packets is the number of packets in this batch 449 o Sum of Delays for Batch is the duration of the batch in the 450 time measurement format specified in the RTF field. 452 o Minimum Delay is the minimum inter-packet gap observed during 453 the batch in the time format specified in the RTF field. 455 o Maximum Delay is the maximum inter-packet gap observed during 456 the batch in the time format specified in the RTF field. 458 This RFC6374 message is carried over an LSP in the way described in 459 [RFC6374] and over an LSP with an SFL as described in Section 9. 461 7.3. Per Packet Delay Measurement 463 If detailed packet delay measurement is required then it might be 464 possible to record the inter-packet gap for each packet pair. In 465 other that exception cases of slow flows or small batch sizes, this 466 would create a large demand on storage in the instrumentation system, 467 bandwidth to such a storage system and bandwidth to the analytics 468 system. Such a measurement technique is outside the scope of this 469 document. 471 7.4. Average Delay 473 Introduced in [RFC8321] is the concept of a one way delay measurement 474 in which the average time of arrival of a set of packets is measured. 475 In this approach the packet is time-stamped at arrival and the 476 Responder returns the sum of the time-stamps and the number of times- 477 tamps. From this the analytics engine can determine the mean delay. 478 An alternative model is that the Responder returns the time stamp of 479 the first and last packet and the number of packets. This method has 480 the advantage of allowing the average delay to be determined at a 481 number of points along the packet path and allowing the components of 482 the delay to be characterized. 484 The packet format of an RFC6374 Average Delay Measurement Message is 485 shown below: 487 0 1 2 3 488 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 1 489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 490 |Version| Flags | Control Code | Message Length | 491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 492 | QTF | RTF | RPTF | Reserved | 493 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 | Session Identifier | DS | 495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 | Number of Packets | 497 | | 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 | Time of First Packet | 500 | | 501 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 | Time of Last Packet | 503 | | 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | Sum of Timestamps of Batch | 506 | | 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 ~ ~ 510 ~ TLV Block ~ 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 Figure 4: Average Delay Measurement Message Format 515 The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF, 516 Session Identifier, and DS Fields are as defined in section 3.7 of 517 RFC6374. The remaining fields are as follows: 519 o Number of Packets is the number of packets in this batch. 521 o Time of First Packet is the time of arrival of the first 522 packet in the batch. 524 o Time of Last Packet is the time of arrival of the last 525 packet in the batch. 527 o Sum of Timestamps of Batch. 529 This RFC6374 message is carried over an LSP in the way described in 530 [RFC6374] and over an LSP with an SFL as described in Section 9. As 531 is the convention with RFC6374, the Query message contains 532 placeholders for the Response message. The placeholders are sent as 533 zero. 535 8. Sampled Measurement 537 In the discussion so far it has been assumed that we would measure 538 the delay characteristics of every packet in a delay measurement 539 interval defined by an SL of constant colour. In [RFC8321] the 540 concept of a sampled measurement is considered. That is the 541 Responder only measures a packet at the start of a group of packets 542 being marked for delay measurement by a particular colour, rather 543 than every packet in the marked batch. A measurement interval is not 544 defined by the duration of a marked batch of packets but the interval 545 between a pair of RFC6374 packets taking a readout of the delay 546 characteristic. This approach has the advantage that the measurement 547 is not impacted by ECMP effects. 549 9. Carrying RFC6374 Packets over an LSP using an SFL 551 The packet format of an RFC6374 Query message using SFLs is shown in 552 Figure 5. 554 +-------------------------------+ 555 | | 556 | LSP | 557 | Label | 558 +-------------------------------+ 559 | | 560 | Synonymous Flow | 561 | Label | 562 +-------------------------------+ 563 | | 564 | GAL | 565 | | 566 +-------------------------------+ 567 | | 568 | ACH Type = 0xA | 569 | | 570 +-------------------------------+ 571 | | 572 | RFC6374 Measurement Message | 573 | | 574 | +-------------------------+ | 575 | | | | 576 | | RFC6374 Fixed | | 577 | | Header | | 578 | | | | 579 | +-------------------------+ | 580 | | | | 581 | | Optional SFL TLV | | 582 | | | | 583 | +-------------------------+ | 584 | | | | 585 | | Optional Return | | 586 | | Information | | 587 | | | | 588 | +-------------------------+ | 589 | | 590 +-------------------------------+ 592 Figure 5: RFC6734 Query Packet with SFL 594 The MPLS label stack is exactly the same as that used for the user 595 data service packets being instrumented except for the inclusion of 596 the GAL [RFC5586] to allow the receiver to distinguish between normal 597 data packets and OAM packets. Since the packet loss measurements are 598 being made on the data service packets, an RFC6374 direct loss 599 measurement is being made, and which is indicated by the type field 600 in the ACH (Type = 0x000A). 602 The RFC6374 measurement message consists of the three components, the 603 RFC6374 fixed header as specified in [RFC6374] carried over the ACH 604 channel type specified the type of measurement being made (currently: 605 loss, delay or loss and delay) as specified in RFC6374. 607 Two optional TLVs MAY also be carried if needed. The first is the 608 SFL TLV specified in Section 9.1. This is used to provide the 609 implementation with a reminder of the SFL that was used to carry the 610 RFC6374 message. This is needed because a number of MPLS 611 implementations do not provide the MPLS label stack to the MPLS OAM 612 handler. This TLV is required if RFC6374 messages are sent over UDP 613 [RFC7876]. This TLV MUST be included unless, by some method outside 614 the scope of this document, it is known that this information is not 615 needed by the RFC6374 Responder. 617 The second set of information that may be needed is the return 618 information that allows the responder send the RFC6374 response to 619 the Querier. This is not needed if the response is requested in-band 620 and the MPLS construct being measured is a point to point LSP, but 621 otherwise MUST be carried. The return address TLV is defined in 622 RFC6378 and the optional UDP Return Object is defined in [RFC7876]. 624 9.1. RFC6374 SFL TLV 626 Editor's Note we need to review the following in the light of further 627 thoughts on the associated signaling protocol(s). I am fairly 628 confident that we need all the fields other than SFL Batch and SFL 629 Index. The Index is useful in order to map between the label and 630 information associated with the FEC. The batch is part of the 631 lifetime management process. 633 The required RFC6374 SFL TLV is shown in Figure 6. This contains the 634 SFL that was carried in the label stack, the FEC that was used to 635 allocate the SFL and the index into the batch of SLs that were 636 allocated for the FEC that corresponds to this SFL. 638 0 1 2 3 639 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 1 640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 | Type | Length |MBZ| SFL Batch | SFL Index | 642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 | SFL | Reserved | 644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 645 | FEC | 646 . . 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 Figure 6: SFL TLV 651 Where: 653 Type Type is set to Synonymous Flow Label (SFL-TLV). 655 Length The length of the TLV as specified in RFC6374. 657 MBZ MUST be sent as zero and ignored on receive. 659 SFL Batch The SFL batch that this SFL was allocated as part 660 of see [I-D.bryant-mpls-sfl-control] 662 SPL Index The index into the list of SFLs that were assigned 663 against the FEC that corresponds to the SFL. 665 SFL The SFL used to deliver this packet. This is an MPLS 666 label which is a component of a label stack entry as 667 defined in Section 2.1 of [RFC3032]. 669 Reserved MUST be sent as zero and ignored on receive. 671 FEC The Forwarding Equivalence Class that was used to 672 request this SFL. This is encoded as per 673 Section 3.4.1 of TBD 675 This information is needed to allow for operation with hardware that 676 discards the MPLS label stack before passing the remainder of the 677 stack to the OAM handler. By providing both the SFL and the FEC plus 678 index into the array of allocated SFLs a number of implementation 679 types are supported. 681 10. Applicability to Pro-active and On-demand Measurement 683 A future version of the this document will discuss the applicability 684 of the various methods to pro-active and on-demand Measurement. 686 11. RFC6374 Combined Loss-Delay Measurement 688 This mode of operation is not currently supported by this 689 specification. 691 12. Privacy Considerations 693 The inclusion of originating and/or flow information in a packet 694 provides more identity information and hence potentially degrades the 695 privacy of the communication. Whilst the inclusion of the additional 696 granularity does allow greater insight into the flow characteristics 697 it does not specifically identify which node originated the packet 698 other than by inspection of the network at the point of ingress, or 699 inspection of the control protocol packets. This privacy threat may 700 be mitigated by encrypting the control protocol packets, regularly 701 changing the synonymous labels and by concurrently using a number of 702 such labels. 704 13. Security Considerations 706 The issue noted in Section 5 is a security consideration. There are 707 no other new security issues associated with the MPLS dataplane. Any 708 control protocol used to request SFLs will need to ensure the 709 legitimacy of the request. 711 14. IANA Considerations 713 14.1. Allocation of PW Associated Channel Type 715 As per the IANA considerations in [RFC5586], IANA is requested to 716 allocate the following Channel Type in the "PW Associated Channel 717 Type" registry: 719 Value Description TLV Follows Reference 720 ----- --------------------------------- ----------- --------- 721 TBD RFC6374 Bucket Jitter Measurement No This 723 TBD RFC6374 Multi-Packet Delay No This 724 Measurement 726 TBD RFC6374 Average Delay Measurement No This 728 14.2. MPLS Loss/Delay TLV Object 730 IANA is request to allocate a new TLV from the 0-127 range on the 731 MPLS Loss/Delay Measurement TLV Object Registry: 733 Type Description Reference 734 ---- --------------------------------- --------- 735 TBD Synonymous Flow Label This 737 A value of 4 is recommended. 739 RFC Editor please delete this line 740 [RFC3032][I-D.bryant-mpls-sfl-control] 742 15. References 744 15.1. Normative References 746 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 747 Requirement Levels", BCP 14, RFC 2119, 748 DOI 10.17487/RFC2119, March 1997, . 751 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 752 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 753 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, 754 . 756 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 757 "MPLS Generic Associated Channel", RFC 5586, 758 DOI 10.17487/RFC5586, June 2009, . 761 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 762 Measurement for MPLS Networks", RFC 6374, 763 DOI 10.17487/RFC6374, September 2011, . 766 [RFC7876] Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path 767 for Packet Loss and Delay Measurement for MPLS Networks", 768 RFC 7876, DOI 10.17487/RFC7876, July 2016, 769 . 771 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 772 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 773 May 2017, . 775 15.2. Informative References 777 [I-D.bryant-mpls-sfl-control] 778 Bryant, S., Swallow, G., and S. Sivabalan, "MPLS Flow 779 Identification Considerations", draft-bryant-mpls-sfl- 780 control-02 (work in progress), October 2017. 782 [I-D.ietf-mpls-sfl-framework] 783 Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., 784 and G. Mirsky, "Synonymous Flow Label Framework", draft- 785 ietf-mpls-sfl-framework-03 (work in progress), June 2018. 787 [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, 788 P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi- 789 Protocol Label Switching (MPLS) Support of Differentiated 790 Services", RFC 3270, DOI 10.17487/RFC3270, May 2002, 791 . 793 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 794 L., and L. Berger, "A Framework for MPLS in Transport 795 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 796 . 798 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 799 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 800 "Alternate-Marking Method for Passive and Hybrid 801 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 802 January 2018, . 804 [RFC8372] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. 805 Mirsky, "MPLS Flow Identification Considerations", 806 RFC 8372, DOI 10.17487/RFC8372, May 2018, 807 . 809 Authors' Addresses 811 Stewart Bryant 812 Huawei 814 Email: stewart.bryant@gmail.com 816 Mach Chen 817 Huawei 819 Email: mach.chen@huawei.com 821 Zhenbin Li 822 Huawei 824 Email: lizhenbin@huawei.com 826 George Swallow 827 Southend Technical Center 829 Email: swallow.ietf@gmail.com 830 Siva Sivabalan 831 Cisco Systems 833 Email: msiva@cisco.com 835 Gregory Mirsky 836 ZTE Corp. 838 Email: gregimirsky@gmail.com 840 Giuseppe Fioccola 841 Huawei Technologies 843 Email: giuseppe.fioccola@huawei.com