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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) -- Obsolete informational reference (is this intentional?): RFC 8321 (Obsoleted by RFC 9341) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group R. Gandhi, Ed. 3 Internet-Draft C. Filsfils 4 Intended Status: Standards Track Cisco Systems, Inc. 5 Expires: April 20, 2020 D. Voyer 6 Bell Canada 7 S. Salsano 8 Universita di Roma "Tor Vergata" 9 M. Chen 10 Huawei 11 October 18, 2019 13 Performance Measurement for 14 Segment Routing Networks with MPLS Data Plane 15 draft-gandhi-mpls-rfc6374-sr-00 17 Abstract 19 Segment Routing (SR) leverages the source routing paradigm. RFC 6374 20 specifies protocol mechanisms to enable the efficient and accurate 21 measurement of packet loss, one-way and two-way delay, as well as 22 related metrics such as delay variation in MPLS networks using probe 23 messages. This document utilizes these mechanisms for Performance 24 Delay and Loss Measurements in Segment Routing (SR) networks with 25 MPLS data plane (SR-MPLS), for both SR links and end-to-end SR 26 Policies. In addition, this document defines Return Path TLV for 27 two-way performance measurement and Block Number TLV for loss 28 measurement. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 Copyright Notice 46 Copyright (c) 2019 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 63 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 64 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 65 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 5 66 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 4. Probe Query and Response Packets . . . . . . . . . . . . . . . 6 68 4.1. Probe Packet Header for SR-MPLS Policies . . . . . . . . . 6 69 4.2. Probe Packet Header for SR-MPLS Links . . . . . . . . . . 6 70 4.3. Probe Response Message for SR-MPLS Links and Policies . . 7 71 4.3.1. One-way Measurement Mode . . . . . . . . . . . . . . . 7 72 4.3.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 7 73 4.3.2.1. Return Path TLV . . . . . . . . . . . . . . . . . 7 74 4.3.3. Loopback Measurement Mode . . . . . . . . . . . . . . 9 75 5. Performance Delay Measurement . . . . . . . . . . . . . . . . 9 76 5.1. Delay Measurement Message Format . . . . . . . . . . . . . 9 77 5.2. Timestamps . . . . . . . . . . . . . . . . . . . . . . . . 9 78 6. Performance Loss Measurement . . . . . . . . . . . . . . . . . 10 79 6.1. Loss Measurement Message Format . . . . . . . . . . . . . 10 80 6.1.1. Block Number TLV . . . . . . . . . . . . . . . . . . . 11 81 7. Performance Measurement for P2MP SR Policies . . . . . . . . . 11 82 8. ECMP for SR-MPLS Policies . . . . . . . . . . . . . . . . . . 12 83 9. SR Link Extended TE Metrics Advertisements . . . . . . . . . . 12 84 10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 85 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 86 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 87 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 88 12.2. Informative References . . . . . . . . . . . . . . . . . 14 89 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17 90 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 93 1. Introduction 95 Service provider's ability to satisfy Service Level Agreements (SLAs) 96 depend on the ability to measure and monitor performance metrics for 97 packet loss and one-way and two-way delay, as well as related metrics 98 such as delay variation. The ability to monitor these performance 99 metrics also provides operators with greater visibility into the 100 performance characteristics of their networks, thereby facilitating 101 planning, troubleshooting, and network performance evaluation. 103 Segment Routing (SR) leverages the source routing paradigm and 104 greatly simplifies network operations for Software Defined Networks 105 (SDNs). SR is applicable to both Multiprotocol Label Switching 106 (SR-MPLS) and IPv6 (SRv6) data planes. SR takes advantage of the 107 Equal-Cost Multipaths (ECMPs) between source and transit nodes, 108 between transit nodes and between transit and destination nodes. SR 109 Policies as defined in [I-D.spring-segment-routing-policy] are used 110 to steer traffic through a specific, user-defined paths using a stack 111 of Segments. Built-in SR Performance Measurement (PM) is one of the 112 essential requirements to provide Service Level Agreements (SLAs). 114 [RFC6374] specifies protocol mechanisms to enable the efficient and 115 accurate measurement of performance metrics in MPLS networks using 116 probe messages. The One-Way Active Measurement Protocol (OWAMP) 117 defined in [RFC4656] and Two-Way Active Measurement Protocol (TWAMP) 118 defined in [RFC5357] provide capabilities for the measurement of 119 various performance metrics in IP networks. However, mechanisms 120 defined in [RFC6374] are more suitable for Segment Routing (SR) when 121 using MPLS data plane (SR-MPLS). [RFC6374] also supports IEEE 1588 122 timestamps [IEEE1588] and "direct mode" Loss Measurement (LM), which 123 are required in SR networks. 125 [RFC7876] specifies the procedures to be used when sending and 126 processing out-of-band performance measurement probe replies over an 127 UDP return path when receiving RFC 6374 based probe queries. These 128 procedures can be used to send out-of-band PM replies for both 129 SR-MPLS links and Policies [I-D.spring-segment-routing-policy] for 130 one-way measurement. 132 This document utilizes the probe-based mechanisms defined in 133 [RFC6374] for Performance Delay and Loss Measurements in SR networks 134 with MPLS data plane, for both SR links and end-to-end SR Policies. 135 In addition, this document defines Return Path TLV for two-way 136 performance measurement and Block Number TLV for loss measurement. 137 The Performance Measurements (PM) for SR links are used to compute 138 extended Traffic Engineering (TE) metrics for delay and loss and can 139 be advertised in the network using the routing protocol extensions. 141 2. Conventions Used in This Document 143 2.1. Requirements Language 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 147 document are to be interpreted as described in [RFC2119] [RFC8174] 148 when, and only when, they appear in all capitals, as shown here. 150 2.2. Abbreviations 152 ACH: Associated Channel Header. 154 DM: Delay Measurement. 156 ECMP: Equal Cost Multi-Path. 158 G-ACh: Generic Associated Channel (G-ACh). 160 GAL: Generic Associated Channel (G-ACh) Label. 162 LM: Loss Measurement. 164 MPLS: Multiprotocol Label Switching. 166 NTP: Network Time Protocol. 168 PM: Performance Measurement. 170 PSID: Path Segment Identifier. 172 PTP: Precision Time Protocol. 174 SID: Segment ID. 176 SL: Segment List. 178 SR: Segment Routing. 180 SR-MPLS: Segment Routing with MPLS data plane. 182 TC: Traffic Class. 184 TE: Traffic Engineering. 186 URO: UDP Return Object. 188 2.3. Reference Topology 190 In the reference topology shown in Figure 1, the sender node R1 191 initiates a performance measurement probe query and the responder 192 node R5 sends a probe response for the query message received. The 193 probe response is typically sent back to the sender node R1. The 194 nodes R1 and R5 may be directly connected via a link enabled with 195 Segment Routing or there exists a Point-to-Point (P2P) SR Policy 196 [I-D.spring-segment-routing-policy] on node R1 with destination to 197 node R5. In case of Point-to-Multipoint (P2MP), SR Policy 198 originating from source node R1 may terminate on multiple destination 199 leaf nodes [I-D.spring-sr-p2mp-policy]. 201 +-------+ Query +-------+ 202 | | - - - - - - - - - ->| | 203 | R1 |---------------------| R5 | 204 | |<- - - - - - - - - - | | 205 +-------+ Response +-------+ 206 Sender Responder 208 Figure 1: Reference Topology 210 3. Overview 212 One-way delay and two-way delay measurement procedure defined in 213 Section 2.4 of [RFC6374] are used. Transmit and Receive packet loss 214 measurement procedures defined in Section 2.2 and Section 2.6 of 215 [RFC6374] are used. One-way loss measurement provides receive packet 216 loss whereas two-way loss measurement provides both transmit and 217 receive packet loss. For both links and end-to-end SR Policies, no 218 PM session for delay or loss measurement is created on the responder 219 node R5 [RFC6374]. 221 For Performance Measurement, probe query and response messages are 222 sent as following: 224 o For Delay Measurement, the probe messages are sent on the 225 congruent path of the data traffic by the sender node, and are 226 used to measure the delay experienced by the actual data traffic 227 flowing on the links and SR Policies. 229 o For Loss Measurement, the probe messages are sent on the congruent 230 path of the data traffic by the sender node, and are used to 231 collect the receive traffic counters for the incoming link or 232 incoming SID where the probe query messages are received at the 233 responder node (incoming link or incoming SID needed since the 234 responder node does not have PM session state present). 236 The In-Situ Operations, Administration, and Maintenance (IOAM) 237 mechanisms for SR-MPLS defined in [I-D.mpls-ioam-sr] are used to 238 carry PM information in-band as part of the data traffic, and are 239 outside the scope of this document. 241 4. Probe Query and Response Packets 243 4.1. Probe Packet Header for SR-MPLS Policies 245 As described in Section 2.9.1 of [RFC6374], MPLS PM probe query and 246 response messages flow over the MPLS Generic Associated Channel 247 (G-ACh). A probe packet for an end-to-end measurement for SR Policy 248 contains SR-MPLS label stack [I-D.spring-segment-routing-policy], 249 with the G-ACh Label (GAL) at the bottom of the stack (with S=1). 250 The GAL is followed by an Associated Channel Header (ACH), which 251 identifies the message type, and the message payload following the 252 ACH as shown in Figure 2. 254 0 1 2 3 255 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 1 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | Label(1) | TC |S| TTL | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 . . 260 . . 261 . . 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 | Label(n) | TC |S| TTL | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | GAL (value 13) | TC |S| TTL | 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 267 |0 0 0 1|Version| Reserved | GAL Channel Type | 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 270 Figure 2: Probe Packet Header for an End-to-end SR-MPLS Policy 272 The SR-MPLS label stack can be empty (as shown in Figure 3) to 273 indicate Implicit NULL label case. 275 4.2. Probe Packet Header for SR-MPLS Links 277 As described in Section 2.9.1 of [RFC6374], MPLS PM probe query and 278 response messages flow over the MPLS Generic Associated Channel 279 (G-ACh). A probe packet for SR-MPLS links contains G-ACh Label (GAL) 280 (with S=1). The GAL is followed by an Associated Channel Header 281 (ACH), which identifies the message type, and the message payload 282 following the ACH as shown in Figure 3. 284 0 1 2 3 285 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 1 286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 287 | GAL (value 13) | TC |S| TTL | 288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 289 |0 0 0 1|Version| Reserved | GAL Channel Type | 290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 Figure 3: Probe Packet Header for an SR-MPLS Link 294 4.3. Probe Response Message for SR-MPLS Links and Policies 296 4.3.1. One-way Measurement Mode 298 In one-way performance measurement mode [RFC7679], the PM sender node 299 can receive "out-of-band" probe replies by properly setting the UDP 300 Return Object (URO) TLV in the probe query message. The URO TLV 301 (Type=131) is defined in [RFC7876] and includes the 302 UDP-Destination-Port and IP Address. In particular, if the sender 303 sets its own IP address in the URO TLV, the probe response is sent 304 back by the responder node to the sender node. In addition, the 305 "control code" in the probe query message is set to "out-of-band 306 response requested". The "Source Address" TLV (Type 130), and 307 "Return Address" TLV (Type 1), if present in the probe query message, 308 are not used to send probe response message. 310 4.3.2. Two-way Measurement Mode 312 In two-way performance measurement mode [RFC6374], when using a 313 bidirectional path, the probe response message is sent back to the 314 sender node on the congruent path of the data traffic on the reverse 315 direction SR Link or SR Policy using a message with format similar to 316 their probe query message. In this case, the "control code" in the 317 probe query message is set to "in-band response requested". 319 A Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of 320 the forward SR-MPLS Policy can be used to find the reverse SR-MPLS 321 Policy and to send back the probe response message for two-way 322 measurement. 324 4.3.2.1. Return Path TLV 326 For two-way performance measurement, the responder node needs to send 327 the probe response message on a specific reverse path. This way the 328 destination node does not require any additional SR Policy state. 329 The sender node can request the responder node to send a response 330 message back on a given reverse path (e.g. co-routed path for two-way 331 measurement). 333 [RFC6374] defines DM and LM probe query messages that can include one 334 or more optional TLVs. New TLV Type (TBA1) is defined in this 335 document for Return Path to carry reverse path for probe response 336 messages (in the payload of the message). The format of the Return 337 Path TLV is shown in Figure 7A and 7B: 339 0 1 2 3 340 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 1 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | Type = TBA1 | Length | Reserved | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 344 | Return Path Sub-TLVs | 345 . . 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 348 Figure 7A: Return Path TLV 350 0 1 2 3 351 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 1 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 | Type | Length | Reserved | 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 | Segment List(1) | 356 . . 357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 358 . . 359 . . 360 . . 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 362 | Segment List(n) | 363 . . 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 Figure 7B: Segment List Sub-TLV in Return Path TLV 368 The Segment List Sub-TLV in the Return Path TLV can be one of the 369 following Types: 371 o Type (value 1): Respond back on Incoming Interface (Layer-3 and 372 Layer-2) (Segment List is Empty) 374 o Type (value 2): SR-MPLS Segment List (Label Stack) of the Reverse 375 SR Path 377 o Type (value 3): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of 378 the Reverse SR Policy 380 The Return Path TLV is optional. The PM sender node MUST only insert 381 one Return Path TLV in the probe query message and the responder node 382 MUST only process the first Return Path TLV in the probe query 383 message and ignore other Return Path TLVs if present. The responder 384 node MUST send probe response message back on the reverse path 385 specified in the Return Path TLV and MUST NOT add Return Path TLV in 386 the probe response message. 388 4.3.3. Loopback Measurement Mode 390 The Loopback measurement mode defined in Section 2.8 of [RFC6374] can 391 be used to measure round-trip delay for a bidirectional SR Path. The 392 probe query messages in this case carries the reverse SR Path label 393 stack as part of the MPLS header. The GAL is still carried at the 394 bottom of the label stack (with S=1). The responder node does not 395 process the PM probe messages and generate response messages. 397 5. Performance Delay Measurement 399 5.1. Delay Measurement Message Format 401 As defined in [RFC6374], MPLS DM probe query and response messages 402 use Associated Channel Header (ACH) (value 0x000C for delay 403 measurement) [RFC6374], which identifies the message type, and the 404 message payload following the ACH. For both SR links and end-to-end 405 measurement for SR-MPLS Policies, the same MPLS DM ACH value is used. 407 The DM message payload as defined in Section 3.2 of [RFC6374] is used 408 for SR-MPLS delay measurement, for both SR links and end-to-end SR 409 Policies. 411 5.2. Timestamps 413 The Section 3.4 of [RFC6374] defines timestamp format that can be 414 used for delay measurement. The IEEE 1588 Precision Time Protocol 415 (PTP) timestamp format [IEEE1588] is used by default as described in 416 Appendix A of [RFC6374], preferred with hardware support. As an 417 alternative, Network Time Protocol (NTP) timestamp format can also be 418 used [RFC6374]. 420 Note that for one-way delay measurement mode, clock synchronization 421 between the sender and responder nodes using the methods detailed in 422 [RFC6374] is required. The two-way delay measurement mode and 423 loopback measurement mode do not require clock synchronization 424 between the sender and responder nodes. 426 6. Performance Loss Measurement 428 The LM protocol can perform two distinct kinds of loss measurement as 429 described in Section 2.9.8 of [RFC6374]. 431 o In inferred mode, LM will measure the loss of specially generated 432 test messages in order to infer the approximate data plane loss 433 level. Inferred mode LM provides only approximate loss 434 accounting. 436 o In direct mode, LM will directly measure data plane packet loss. 437 Direct mode LM provides perfect loss accounting, but may require 438 hardware support. 440 For both of these modes of LM, Path Segment Identifier (PSID) 441 [I-D.spring-mpls-path-segment] is used for accounting received 442 traffic on the egress node of the SR-MPLS Policy as shown in Figure 443 4. Different values of PSID can be used to measure packet loss per 444 SR-MPLS Policy, per Candidate Path or per Segment List of the SR 445 Policy. 447 0 1 2 3 448 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 1 449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 450 | PSID | TC |S| TTL | 451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 452 | GAL (value 13) | TC |S| TTL | 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 |0 0 0 1|Version| Reserved | GAL Channel Type | 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 457 Figure 4: With Path Segment Identifier for SR-MPLS Policy 459 6.1. Loss Measurement Message Format 461 As defined in [RFC6374], MPLS LM probe query and response messages 462 use Associated Channel Header (ACH) (value 0x000A for direct loss 463 measurement or value 0x000B for inferred loss measurement), which 464 identifies the message type, and the message payload following the 465 ACH. For both SR links and end-to-end measurement for SR-MPLS 466 Policies, the same MPLS LM ACH value is used. 468 The LM message payload as defined in Section 3.1 of [RFC6374] is used 469 for SR-MPLS loss measurement, for both SR links and end-to-end SR 470 Policies. 472 6.1.1. Block Number TLV 474 The Loss Measurement using Alternate-Marking method defined in 475 [RFC8321] requires to identify the Block Number (or color) of the 476 traffic counters carried by the probe query and response messages. 477 Probe query and response messages specified in [RFC6374] for Loss 478 Measurement do not define any means to carry the Block Number. 480 [RFC6374] defines probe query and response messages that can include 481 one or more optional TLVs. New TLV Type (value TBA2) is defined in 482 this document to carry Block Number (16-bit) for the traffic counters 483 in the probe query and response messages for loss measurement. The 484 format of the Block Number TLV is shown in Figure 5: 486 0 1 2 3 487 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 | Type TBA2 | Length | Reserved | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | Reserved | Block Number | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 Figure 5: Block Number TLV 496 The Block Number TLV is optional. The PM sender node SHOULD only 497 insert one Block Number TLV in the probe query message and the 498 responder node in the probe response message SHOULD return the first 499 Block Number TLV from the probe query messages and ignore other Block 500 Number TLVs if present. In both probe query and response messages, 501 the counters MUST belong to the same Block Number. 503 7. Performance Measurement for P2MP SR Policies 505 The procedures for delay and loss measurement reviewed in this 506 document for Point-to-Point (P2P) SR-MPLS Policies 507 [I-D.spring-segment-routing-policy] are also equally applicable to 508 the Point-to-Multipoint (P2MP) SR-MPLS Policies 509 [I-D.spring-sr-p2mp-policy] as following: 511 o The sender root node sends probe query messages using the either 512 Spray P2MP segment or TreeSID P2MP segment defined in 513 [I-D.spring-sr-p2mp-policy] over the P2MP SR Policy as shown in 514 Figure 6. 516 o Each responder leaf node adds the "Source Address" TLV (Type 130) 517 [RFC6374] with its IP address in the probe response messages. 518 This TLV allows the sender root node to identify the responder 519 leaf nodes of the P2MP SR Policy. 521 o The P2MP root node measures the end-to-end delay and loss 522 performance for each P2MP leaf node. 524 0 1 2 3 525 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 1 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | TreeSID OR Spray SID | TC |S| TTL | 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 529 | GAL (value 13) | TC |S| TTL | 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 |0 0 0 1|Version| Reserved | GAL Channel Type | 532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 534 Figure 6: With P2MP Segment Identifier for SR-MPLS Policy 536 8. ECMP for SR-MPLS Policies 538 An SR Policy can have ECMPs between the source and transit nodes, 539 between transit nodes and between transit and destination nodes. 540 Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP 541 paths via transit nodes part of that Anycast group. The PM probe 542 messages need to be sent to traverse different ECMP paths to measure 543 performance delay of an SR Policy. 545 Forwarding plane has various hashing functions available to forward 546 packets on specific ECMP paths. For SR-MPLS Policy, entropy label 547 [RFC6790] can be used in PM probe messages to take advantage of the 548 hashing function in forwarding plane to influence the ECMP path taken 549 by them. 551 9. SR Link Extended TE Metrics Advertisements 553 The extended TE metrics for SR link delay and loss computed using the 554 performance measurement procedures reviewed in this document can be 555 advertised in the routing domain as follows: 557 o For OSPF, ISIS, and BGP-LS, protocol extensions defined in 558 [RFC7471], [RFC8570], and [RFC8571] are used, respectively for 559 advertising the extended TE link metrics in the network. 561 o The extended TE link delay metrics advertised are minimum-delay, 562 maximum-delay, average-delay, and delay-variance for one-way. 564 o The delay-variance metric is computed as specified in Section 4.2 565 of [RFC5481]. 567 o The one-way delay metrics can be computed using two-way delay 568 measurement or round-trip delay measurement from loopback mode by 569 dividing the measured delay values by 2. 571 o The extended TE link loss metric advertised is one-way percentage 572 packet loss. 574 o Similarly, the extended TE link delay and loss metrics are 575 advertised for Layer 2 bundle members in ISIS 576 [I-D.lsr-ospf-l2bundles] and OSPF [I-D.isis-l2bundles] using the 577 same mechanisms defined in [RFC8570] and [RFC7471], respectively. 579 10. Security Considerations 581 This document reviews the procedures for performance delay and loss 582 measurement for SR-MPLS networks, for both links and end-to-end SR 583 Policies using the mechanisms defined in [RFC6374] and [RFC7876]. 584 This document does not introduce any additional security 585 considerations other than those covered in [RFC6374], [RFC7471], 586 [RFC8570], [RFC8571], and [RFC7876]. 588 11. IANA Considerations 590 IANA is requested to allocate a value for the following Return Path 591 TLV Type for RFC 6374 to be carried in PM probe query messages: 593 o Type TBA1: Return Path TLV 595 IANA is requested to allocate the values for the following Sub-TLV 596 Types for the Return Path TLV for RFC 6374. 598 o Type (value 1): Respond back on Incoming Interface (Layer-3 and 599 Layer-2) (Segment List is Empty) 601 o Type (value 2): SR-MPLS Segment List (Label Stack) of the Reverse 602 SR Path 604 o Type (value 3): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of 605 the Reverse SR Policy 607 IANA is also requested to allocate a value for the following Block 608 Number TLV Type for RFC 6374 to be carried in the PM probe query and 609 response messages for loss measurement: 611 o Type TBA2: Block Number TLV 613 12. References 615 12.1. Normative References 617 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 618 Requirement Levels", RFC 2119, March 1997. 620 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 621 Measurement for MPLS networks', RFC 6374, September 2011. 623 [RFC7876] Bryant, S., Sivabalan, S., and Soni, S., "UDP Return Path 624 for Packet Loss and Delay Measurement for MPLS Networks", 625 RFC 7876, July 2016. 627 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 628 2119 Key Words", RFC 8174, May 2017. 630 12.2. Informative References 632 [IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock 633 Synchronization Protocol for Networked Measurement and 634 Control Systems", March 2008. 636 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 637 Zekauskas, "A One-way Active Measurement Protocol 638 (OWAMP)", RFC 4656, September 2006. 640 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 641 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 642 RFC 5357, October 2008. 644 [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation 645 Applicability Statement", RFC 5481, March 2009. 647 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 648 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 649 RFC 6790, November 2012. 651 [RFC7679] Almes, G., et al., "A One-Way Delay Metric for IP 652 Performance Metrics (IPPM)', RFC 7679, January 2016. 654 [RFC7471] Giacalone, S., et al., "OSPF Traffic Engineering (TE) 655 Metric Extensions", RFC 7471, March 2015. 657 [RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive 658 and Hybrid Performance Monitoring", RFC 8321, January 659 2018. 661 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 662 Decraene, B., Litkowski, S., and R. Shakir, "Segment 663 Routing Architecture", RFC 8402, July 2018. 665 [RFC8570] Ginsberg, L. Ed., et al., "IS-IS Traffic Engineering (TE) 666 Metric Extensions", RFC 8570, March 2019. 668 [RFC8571] Ginsberg, L. Ed., et al., "BGP - Link State (BGP-LS) 669 Advertisement of IGP Traffic Engineering Performance 670 Metric Extensions", RFC 8571, March 2019. 672 [I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment 673 Routing Policy Architecture", 674 draft-ietf-spring-segment-routing-policy, work in 675 progress. 677 [I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication 678 Policy for P2MP Service Delivery", 679 draft-voyer-spring-sr-p2mp-policy, work in progress. 681 [I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding 682 Label/Segment-ID in PCE-based Networks", 683 draft-ietf-pce-binding-label-sid, work in progress. 685 [I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in 686 MPLS Based Segment Routing Network", 687 draft-ietf-spring-mpls-path-segment, work in progress. 689 [I-D.mpls-ioam-sr] Gandhi, R. Ed., et al., "Segment Routing with 690 MPLS Data Plane Encapsulation for In-situ OAM Data", 691 draft-gandhi-mpls-ioam-sr, work in progress. 693 [I-D.lsr-ospf-l2bundles] Talaulikar, K., et al., "Advertising L2 694 Bundle Member Link Attributes in OSPF", 695 draft-ketant-lsr-ospf-l2bundles, work in progress. 697 [I-D.isis-l2bundles] Ginsberg, L., et al., "Advertising L2 Bundle 698 Member Link Attributes in IS-IS", 699 draft-ietf-isis-l2bundles, work in progress. 701 Acknowledgments 703 The authors would like to thank Thierry Couture for the discussions 704 on the use-cases for the performance measurement in segment routing 705 networks. The authors would like to thank Greg Mirsky for providing 706 many useful comments and suggestions. The authors would also like to 707 thank Stewart Bryant, Sam Aldrin, and Rajiv Asati for their review 708 comments. 710 Contributors 712 Sagar Soni 713 Cisco Systems, Inc. 714 Email: sagsoni@cisco.com 716 Patrick Khordoc 717 Cisco Systems, Inc. 718 Email: pkhordoc@cisco.com 720 Zafar Ali 721 Cisco Systems, Inc. 722 Email: zali@cisco.com 724 Pier Luigi Ventre 725 CNIT 726 Italy 727 Email: pierluigi.ventre@cnit.it 729 Authors' Addresses 731 Rakesh Gandhi (editor) 732 Cisco Systems, Inc. 733 Canada 734 Email: rgandhi@cisco.com 736 Clarence Filsfils 737 Cisco Systems, Inc. 738 Email: cfilsfil@cisco.com 740 Daniel Voyer 741 Bell Canada 742 Email: daniel.voyer@bell.ca 744 Stefano Salsano 745 Universita di Roma "Tor Vergata" 746 Italy 747 Email: stefano.salsano@uniroma2.it 749 Mach(Guoyi) Chen 750 Huawei 751 Email: mach.chen@huawei.com