idnits 2.17.1 draft-gandhi-spring-rfc6374-srpm-udp-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (May 15, 2019) is 1807 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- 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 SPRING Working Group R. Gandhi, Ed. 3 Internet-Draft C. Filsfils 4 Intended Status: Standards Track Cisco Systems, Inc. 5 Expires: November 16, 2019 D. Voyer 6 Bell Canada 7 S. Salsano 8 Universita di Roma "Tor Vergata" 9 P. L. Ventre 10 CNIT 11 M. Chen 12 Huawei 13 May 15, 2019 15 Performance Measurement Using UDP Path 16 for Segment Routing Networks 17 draft-gandhi-spring-rfc6374-srpm-udp-01 19 Abstract 21 Segment Routing (SR) is applicable to both Multiprotocol Label 22 Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document 23 specifies procedures for using UDP path for sending and processing 24 synthetic probe query and response messages for Performance 25 Measurement (PM). The procedure uses the RFC 6374 defined mechanisms 26 for Performance Delay and Loss Measurement. The procedure specified 27 is applicable to SR-MPLS and SRv6 data planes for both links and 28 end-to-end measurement for SR Policies. In addition, this document 29 defines Return Path TLV for two-way performance measurement and Block 30 Number TLV for loss measurement. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at http://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 Copyright Notice 49 Copyright (c) 2019 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 66 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 67 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 68 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 5 69 3. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . . 7 70 3.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 7 71 3.1.1. Delay Measurement Probe Query Message . . . . . . . . 7 72 3.1.2. Loss Measurement Probe Query Message . . . . . . . . . 7 73 3.1.2.1. Block Number TLV . . . . . . . . . . . . . . . . . 8 74 3.1.3. Probe Query for SR Links . . . . . . . . . . . . . . . 9 75 3.1.4. Probe Query for End-to-end Measurement for SR Policy . 9 76 3.1.4.1. Probe Query Message for SR-MPLS Policy . . . . . . 9 77 3.1.4.2. Probe Query Message for SRv6 Policy . . . . . . . 10 78 3.2. Probe Response Message . . . . . . . . . . . . . . . . . . 10 79 3.2.1. One-way Measurement Mode . . . . . . . . . . . . . . . 11 80 3.2.1.1. SR Links and End-to-end Measurement for SR 81 Policy . . . . . . . . . . . . . . . . . . . . . . 11 82 3.2.1.2. Probe Response Message to Controller . . . . . . . 12 83 3.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 12 84 3.2.2.1. SR Links . . . . . . . . . . . . . . . . . . . . . 12 85 3.2.2.2. End-to-end Measurement for SR Policy . . . . . . . 12 86 3.2.2.3. Return Path TLV . . . . . . . . . . . . . . . . . 12 87 3.2.2.4. Probe Response Message for SR-MPLS Policy . . . . 14 88 3.2.2.5. Probe Response Message for SRv6 Policy . . . . . . 14 89 3.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 15 90 3.3. Checksum Complement . . . . . . . . . . . . . . . . . . . 15 91 4. Performance Measurement for P2MP SR Policies . . . . . . . . . 15 92 5. ECMP Support for SR Policies . . . . . . . . . . . . . . . . . 16 93 6. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 16 94 6.1. Sequence Number TLV in Unauthenticated Mode . . . . . . . 17 95 6.2. Sequence Number TLV in Authenticated Mode . . . . . . . . 17 96 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 97 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 98 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 99 9.1. Normative References . . . . . . . . . . . . . . . . . . . 20 100 9.2. Informative References . . . . . . . . . . . . . . . . . . 20 101 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 23 102 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 105 1. Introduction 107 Segment Routing (SR) technology greatly simplifies network operations 108 for Software Defined Networks (SDNs). SR is applicable to both 109 Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes. 110 SR takes advantage of the Equal-Cost Multipaths (ECMPs) between 111 source, transit and destination nodes. SR Policies as defined in 112 [I-D.spring-segment-routing-policy] are used to steer traffic through 113 a specific, user-defined path using a stack of Segments. Built-in SR 114 Performance Measurement (PM) is one of the essential requirements to 115 provide Service Level Agreements (SLAs). 117 The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656] 118 and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357] 119 provide capabilities for the measurement of various performance 120 metrics in IP networks. These protocols rely on control channel 121 signaling to establish a test channel over an UDP path. These 122 protocols lack support for IEEE 1588 timestamp [IEEE1588] format and 123 direct-mode Loss Measurement (LM), which are required in SR networks 124 [RFC6374]. The Simple Two-way Active Measurement Protocol (STAMP) 125 [I-D.ippm-stamp] alleviates the control channel signaling by using 126 configuration data model to provision test channels. In addition, 127 the STAMP supports IEEE 1588 timestamp format for Delay Measurement 128 (DM). The TWAMP Light from broadband forum [BBF.TR-390] provides 129 simplified mechanisms for active performance measurement in Customer 130 Edge IP networks. [Y1731] specifies the mechanisms to carry OAM 131 messages specifically for Ethernet networks that include Ethernet 132 Frame Delay and Loss measurements. 134 [RFC6374] specifies protocol mechanisms to enable the efficient and 135 accurate measurement of performance metrics and can be used in SR 136 networks with MPLS data plane [I-D.spring-rfc6374-srpm-mpls]. 137 [RFC6374] addresses the limitations of the IP based performance 138 measurement protocols as specified in Section 1 of [RFC6374]. The 139 [RFC6374] requires data plane to support MPLS Generic Associated 140 Channel Label (GAL) and Generic Associated Channel (G-Ach), which may 141 not be supported on all nodes in the network. 143 [RFC7876] specifies the procedures to be used when sending and 144 processing out-of-band performance measurement probe response 145 messages over an UDP return path for RFC 6374 based probe queries. 146 [RFC7876] can be used to send out-of-band PM probe responses in both 147 SR-MPLS and SRv6 networks for one-way performance measurement. 149 For SR Policies, there are ECMPs between the source and transit 150 nodes, between transit nodes and between transit and destination 151 nodes. Existing PM protocols (e.g. RFC 6374) do not define handling 152 for ECMP forwarding paths in SR networks. 154 For two-way measurements for SR Policies, there is a need to specify 155 a return path in the form of a Segment List in PM probe query 156 messages without requiring any SR Policy state on the destination 157 node. Existing protocols do not have such mechanisms to specify 158 return path in the PM probe query messages. 160 This document specifies a procedure for using UDP path for sending 161 and processing synthetic probe query and response messages for 162 Performance Measurement that does not require to bootstrap PM 163 sessions. The procedure uses RFC 6374 defined mechanisms for 164 Performance Delay and Loss Measurement and unless otherwise 165 specified, the procedures from RFC 6374 are not modified. The 166 procedure specified is applicable to both SR-MPLS and SRv6 data 167 planes. The procedure can be used for both SR links and end-to-end 168 performance measurement for SR Policies. This document also defines 169 mechanisms for handling Equal Cost Multi-Paths (ECMPs) of SR Policies 170 for performance delay measurement. In addition, this document 171 defines Return Path TLV for two-way performance measurement, Block 172 Number TLV for loss measurement and Sequence Number TLV. 174 2. Conventions Used in This Document 176 2.1. Requirements Language 178 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 179 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 180 document are to be interpreted as described in [RFC2119] [RFC8174] 181 when, and only when, they appear in all capitals, as shown here. 183 2.2. Abbreviations 185 ACH: Associated Channel Header. 187 BSID: Binding Segment ID. 189 DFLag: Data Format Flag. 191 DM: Delay Measurement. 193 ECMP: Equal Cost Multi-Path. 195 G-ACh: Generic Associated Channel (G-ACh). 197 GAL: Generic Associated Channel (G-ACh) Label. 199 LM: Loss Measurement. 201 MPLS: Multiprotocol Label Switching. 203 NTP: Network Time Protocol. 205 OWAMP: One-Way Active Measurement Protocol. 207 PM: Performance Measurement. 209 PSID: Path Segment Identifier. 211 PTP: Precision Time Protocol. 213 SID: Segment ID. 215 SL: Segment List. 217 SR: Segment Routing. 219 SR-MPLS: Segment Routing with MPLS data plane. 221 SRv6: Segment Routing with IPv6 data plane. 223 STAMP: Simple Two-way Active Measurement Protocol. 225 TC: Traffic Class. 227 TWAMP: Two-Way Active Measurement Protocol. 229 URO: UDP Return Object. 231 2.3. Reference Topology 233 In the reference topology, the querier node R1 initiates a probe 234 query for performance measurement and the responder node R5 sends a 235 probe response for the query message received. The probe response 236 may be sent to the querier node R1 or to a controller node R100. The 237 nodes R1 and R5 may be directly connected via a link enabled with 238 Segment Routing or there exists a Point-to-Point (P2P) SR Policy 239 [I-D.spring-segment-routing-policy] on node R1 with destination to 240 node R5. In case of Point-to-Multipoint (P2MP), SR Policy 241 originating from source node R1 may terminate on multiple destination 242 leaf nodes [I-D.spring-sr-p2mp-policy]. 244 ------ 245 |R100| 246 ------ 247 ^ 248 | Response 249 | 250 +-------+ Query +-------+ 251 | | - - - - - - - - - ->| | 252 | R1 |---------------------| R5 | 253 | |<- - - - - - - - - - | | 254 +-------+ Response +-------+ 256 Reference Topology 258 For delay and loss measurements, for both links and end-to-end SR 259 Policies, no PM session is created on the responder node R5. One-way 260 delay and two-way delay measurements are defined in Section 2.4 of 261 [RFC6374]. Transmit and Receive packet loss measurements are defined 262 in Section 2.2 and Section 2.6 of [RFC6374]. One-way loss 263 measurement provides receive packet loss whereas two-way loss 264 measurement provides both transmit and receive packet loss. 266 For Performance Measurement, synthetic probe query and response 267 messages are used as following: 269 o For Delay Measurement, the probe messages are sent on the 270 congruent path of the data traffic by the querier node, and are 271 used to measure the delay experienced by the actual data traffic 272 flowing on the links and SR Policies. 274 o For Loss Measurement, the probe messages are sent on the congruent 275 path of the data traffic by the querier node, and are used to 276 collect the receive traffic counters for the incoming link or 277 incoming SID where the probe query messages are received at the 278 responder node (incoming link or incoming SID used as the 279 responder node has no PM session state present). 281 The In-Situ Operations, Administration, and Maintenance (IOAM) 282 mechanisms for SR-MPLS defined in [I-D.spring-ioam-sr-mpls] and for 283 SRv6 defined in [I-D.spring-srv6-oam] are used to carry PM 284 information in-band as part of the data traffic, and are outside the 285 scope of this document. 287 3. Probe Messages 289 3.1. Probe Query Message 291 In this document, UDP path is used for Delay and Loss measurements 292 for SR links and end-to-end SR Policies. The user-configured UDP 293 ports are used for identifying PM probe packets and to avoid 294 signaling to bootstrap PM sessions. This approach is similar to the 295 one defined in STAMP protocol [I-D.ippm-stamp]. The IPv4 TTL or IPv6 296 Hop Limit field of the IP header MUST be set to 255. 298 3.1.1. Delay Measurement Probe Query Message 300 The message content for Delay Measurement for probe query message 301 using UDP header [RFC768] is shown in Figure 1. The DM probe query 302 message is sent with user-configured Destination UDP port number for 303 DM. The Destination UDP port can also be used as Source port for 304 two-way delay measurement, since the message has a flag to 305 distinguish between query and response. The DM probe query message 306 contains the payload for delay measurement defined in Section 3.2 of 307 [RFC6374]. 309 +---------------------------------------------------------------+ 310 | IP Header | 311 . Source IP Address = Querier IPv4 or IPv6 Address . 312 . Destination IP Address = Responder IPv4 or IPv6 Address . 313 . Protocol = UDP . 314 . Router Alert Option Not Set . 315 . . 316 +---------------------------------------------------------------+ 317 | UDP Header | 318 . Source Port = As chosen by Querier . 319 . Destination Port = User-configured Port for Delay Measurement. 320 . . 321 +---------------------------------------------------------------+ 322 | Payload = Message as specified in Section 3.2 of RFC 6374 | 323 . . 324 +---------------------------------------------------------------+ 326 Figure 1: DM Probe Query Message 328 3.1.2. Loss Measurement Probe Query Message 329 The message content for Loss measurement probe query message using 330 UDP header [RFC768] is shown in Figure 2. As shown, the LM probe 331 query message is sent with user-configured Destination UDP port 332 number for LM. Different Destination UDP ports are used for direct- 333 mode and inferred-mode loss measurements. The Destination UDP port 334 can also be used as Source port for two-way loss measurement, since 335 the message has a flag to distinguish between query and response. 336 The LM probe query message contains the payload for loss measurement 337 defined in Section 3.1 of [RFC6374]. 339 +---------------------------------------------------------------+ 340 | IP Header | 341 . Source IP Address = Querier IPv4 or IPv6 Address . 342 . Destination IP Address = Responder IPv4 or IPv6 Address . 343 . Protocol = UDP . 344 . Router Alert Option Not Set . 345 . . 346 +---------------------------------------------------------------+ 347 | UDP Header | 348 . Source Port = As chosen by Querier . 349 . Destination Port = User-configured Port for Loss Measurement . 350 . . 351 +---------------------------------------------------------------+ 352 | Payload = Message as specified in Section 3.1 of RFC 6374 | 353 . . 354 +---------------------------------------------------------------+ 356 Figure 2: LM Probe Query Message 358 3.1.2.1. Block Number TLV 360 The Loss Measurement using Alternate-Marking method defined in 361 [RFC8321] requires to identify the Block Number (or color) of the 362 traffic counters carried by the probe query and response messages. 363 Probe query and response messages specified in [RFC6374] for Loss 364 Measurement do not define any means to carry the Block Number. 366 [RFC6374] defines probe query and response messages that can include 367 one or more optional TLVs. New TLV Type (value TBA2) is defined in 368 this document to carry Block Number (16-bit) for the traffic counters 369 in the probe query and response messages for loss measurement. The 370 format of the Block Number TLV is shown in Figure 11: 372 0 1 2 3 373 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 1 374 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 375 | Type TBA2 | Length | Reserved | 376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 | Reserved | Block Number | 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 Figure 11: Block Number TLV 382 The Block Number TLV is optional. The PM querier node SHOULD only 383 insert one Block Number TLV in the probe query message and the 384 responder node in the probe response message SHOULD return the first 385 Block Number TLV from the probe query messages and ignore other Block 386 Number TLVs if present. In both probe query and response messages, 387 the counters MUST belong to the same Block Number. 389 3.1.3. Probe Query for SR Links 391 The probe query message as defined in Figure 1 is sent on the 392 congruent path of the data traffic for performance Delay measurement. 393 Similarly, the probe query message as defined in Figure 2 is sent on 394 the congruent path of the data traffic for performance Loss 395 measurement. 397 3.1.4. Probe Query for End-to-end Measurement for SR Policy 399 3.1.4.1. Probe Query Message for SR-MPLS Policy 401 The message content for the probe query message using UDP header for 402 end-to-end performance measurement of SR-MPLS Policy is shown in 403 Figure 3. 405 0 1 2 3 406 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 1 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 | Segment List(1) | TC |S| TTL | 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 410 . . 411 . . 412 . . 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Segment List(n) | TC |S| TTL | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | PSID | TC |S| TTL | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | Message as shown in Figure 1 for DM or Figure 2 for LM | 419 . . 420 +---------------------------------------------------------------+ 421 Figure 3: Probe Query Message for SR-MPLS Policy 423 The Segment List (SL) can be empty to indicate Implicit NULL label 424 case. 426 The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of 427 the SR-MPLS Policy is used for accounting received traffic on the 428 egress node for loss measurement. The PSID is not required for delay 429 measurement. 431 3.1.4.2. Probe Query Message for SRv6 Policy 433 An SRv6 Policy is setup using the SRv6 Segment Routing Header (SRH) 434 and a Segment List as defined in [I-D.6man-segment-routing-header]. 435 The probe query messages using UDP header for end-to-end performance 436 measurement of an SRv6 Policy is sent using its SRv6 Segment Routing 437 Header (SRH) and Segment List as shown in Figure 4. 439 0 1 2 3 440 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 1 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 | SRH | 443 . END.OTP (DM) or END.OP (LM) with Target SRv6 SID . 444 . . 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | Message as shown in Figure 1 for DM or Figure 2 for LM | 447 . (Using IPv6 Addresses) . 448 . . 449 +---------------------------------------------------------------+ 451 Figure 4: Probe Query Message for SRv6 Policy 453 For delay measurement of SRv6 Policy using SRH, END function END.OTP 454 [I-D.spring-srv6-oam] is used with the target SRv6 SID to punt probe 455 messages on the target node, as shown in Figure 4. Similarly, for 456 loss measurement of SRv6 Policy, END function END.OP 457 [I-D.spring-srv6-oam] is used with target SRv6 SID to punt probe 458 messages on the target node. 460 3.2. Probe Response Message 462 When the received probe query message does not contain any UDP Return 463 Object (URO) TLV [RFC7876], the probe response message is sent using 464 the IP/UDP information from the probe query message. The content of 465 the probe response message is shown in Figure 5. 467 +---------------------------------------------------------------+ 468 | IP Header | 469 . Source IP Address = Responder IPv4 or IPv6 Address . 470 . Destination IP Address = Source IP Address from Query . 471 . Protocol = UDP . 472 . Router Alert Option Not Set . 473 . . 474 +---------------------------------------------------------------+ 475 | UDP Header | 476 . Source Port = As chosen by Responder . 477 . Destination Port = Source Port from Query . 478 . . 479 +---------------------------------------------------------------+ 480 | Message as specified in Section 3.2 of RFC 6374 for DM, or | 481 . Message as specified in Section 3.1 of RFC 6374 for LM . 482 . . 483 +---------------------------------------------------------------+ 485 Figure 5: Probe Response Message 487 When the received probe query message contains UDP Return Object 488 (URO) TLV [RFC7876], the probe response message uses the IP/UDP 489 information from the URO in the probe query message. The content of 490 the probe response message is shown in Figure 6. 492 +---------------------------------------------------------------+ 493 | IP Header | 494 . Source IP Address = Responder IPv4 or IPv6 Address . 495 . Destination IP Address = URO.Address . 496 . Protocol = UDP . 497 . Router Alert Option Not Set . 498 . . 499 +---------------------------------------------------------------+ 500 | UDP Header | 501 . Source Port = As chosen by Responder . 502 . Destination Port = URO.UDP-Destination-Port . 503 . . 504 +---------------------------------------------------------------+ 505 | Message as specified in Section 3.2 of RFC 6374 for DM, or | 506 . Message as specified in Section 3.1 of RFC 6374 for LM . 507 . . 508 +---------------------------------------------------------------+ 510 Figure 6: Probe Response Message Using URO from Probe Query 512 3.2.1. One-way Measurement Mode 514 3.2.1.1. SR Links and End-to-end Measurement for SR Policy 516 In one-way performance measurement mode, the probe response message 517 as defined in Figure 5 or Figure 6 is sent out-of-band for both SR 518 links and SR Policies. 520 The PM querier node can receive probe response message back by 521 setting its own IP address as Source Address of the header or by 522 adding URO TLV in the probe query message and setting its own IP 523 address in the IP Address in the URO TLV (Type=131) [RFC7876]. The 524 "control code" in the probe query message is set to "out-of-band 525 response requested". The "Source Address" TLV (Type 130), and 526 "Return Address" TLV (Type 1), if present in the probe query message, 527 are not used to send probe response message. 529 3.2.1.2. Probe Response Message to Controller 531 As shown in the Reference Topology, if the querier node requires the 532 probe response message to be sent to the controller R100, it adds URO 533 TLV in the probe query message and sets the IP address of R100 in the 534 IP Address field and user-configured UDP port for DM and for LM in 535 the UDP-Destination-Port field of the URO TLV (Type=131) [RFC7876]. 537 3.2.2. Two-way Measurement Mode 539 3.2.2.1. SR Links 541 In two-way performance measurement mode, when using a bidirectional 542 link, the probe response message as defined in Figure 5 or Figure 6 543 is sent back on the congruent path of the data traffic to the querier 544 node for SR links. In this case, the "control code" in the probe 545 query message is set to "in-band response requested" [RFC6374]. 547 3.2.2.2. End-to-end Measurement for SR Policy 549 In two-way performance measurement mode, when using a bidirectional 550 path, the probe response message is sent back on the congruent path 551 of the data traffic to the querier node for end-to-end measurement of 552 SR Policies. In this case, the "control code" in the probe query 553 message is set to "in-band response requested" [RFC6374]. 555 3.2.2.3. Return Path TLV 557 For two-way performance measurement, the responder node needs to send 558 the probe response message on a specific reverse SR path. This way 559 the destination node does not require any additional SR Policy state. 560 The querier node can request in the probe query message to the 561 responder node to send a response back on a given reverse path 562 (typically co-routed path for two-way measurement). 564 [RFC6374] defines DM and LM probe query messages that can include one 565 or more optional TLVs. New TLV Type (TBA1) is defined in this 566 document for Return Path to carry reverse SR path for probe response 567 messages (in the payload of the message). The format of the Return 568 Path TLV is shown in Figure 7A and 7B: 570 0 1 2 3 571 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 1 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 | Type = TBA1 | Length | Reserved | 574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 | Return Path Sub-TLVs | 576 . . 577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 579 Figure 7A: Return Path TLV 581 0 1 2 3 582 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 1 583 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 | Type | Length | Reserved | 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 | Segment List(1) | 587 . . 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 . . 590 . . 591 . . 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | Segment List(n) | 594 . . 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 Figure 7B: Segment List Sub-TLV in Return Path TLV 599 The Sub-TLV in the Return Path TLV can be one of the following Types: 601 o Type (value 1): SR-MPLS Label Stack of the Reverse SR Policy 603 o Type (value 2): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of 604 the Reverse SR Policy 606 o Type (value 3): SRv6 Segment List of the Reverse SR Policy 608 o Type (value 4): SRv6 Binding SID [I-D.pce-binding-label-sid] of 609 the Reverse SR Policy 611 With sub-TLV Type 1, the Segment List(1) can be used by the responder 612 node to compute the next-hop IP address and outgoing interface to 613 send the probe response messages. 615 The Return Path TLV is optional. The PM querier node MUST only 616 insert one Return Path TLV in the probe query message and the 617 responder node MUST only process the first Return Path TLV in the 618 probe query message and ignore other Return Path TLVs if present. 619 The responder node MUST send probe response message back on the 620 reverse path specified in the Return Path TLV and MUST NOT add Return 621 Path TLV in the probe response message. 623 3.2.2.4. Probe Response Message for SR-MPLS Policy 625 The message content for sending probe response message on the 626 congruent path of the data traffic using UDP header for two-way 627 end-to-end performance measurement of an SR-MPLS Policy is shown in 628 Figure 8. The SR-MPLS label stack in the packet header is built 629 using the Segment List received in the Return Path TLV in the probe 630 query message. 632 0 1 2 3 633 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 1 634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 | Segment List(1) | TC |S| TTL | 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 . . 638 . . 639 . . 640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 | Segment List(n) | TC |S| TTL | 642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 | Message as shown in Figure 5 or 6 | 644 . . 645 +---------------------------------------------------------------+ 647 Figure 8: Probe Response Message for SR-MPLS Policy 649 The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of 650 the forward SR-MPLS Policy can be used to find the reverse SR-MPLS 651 Policy to send the probe response message for two-way measurement in 652 the absence of Return Path TLV defined in the following Section. 654 3.2.2.5. Probe Response Message for SRv6 Policy 656 The message content for sending probe response message on the 657 congruent path of the data traffic using UDP header for two-way 658 end-to-end performance measurement of an SRv6 Policy is shown in 659 Figure 9. For SRv6 Policy using SRH, the SRv6 SID list in the SRH of 660 the probe response message is built using the SRv6 Segment List 661 received in the Return Path TLV in the probe query message. 663 0 1 2 3 664 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 1 665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 | SRH | 667 . END.OTP (DM) or END.OP (LM) with Target SRv6 SID . 668 . . 669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | Message as shown in Figure 5 or 6 (with IPv6 Addresses) | 671 . . 672 +---------------------------------------------------------------+ 674 Figure 9: Probe Response Message for SRv6 Policy 676 3.2.3. Loopback Measurement Mode 678 The Loopback measurement mode defined in Section 2.8 of [RFC6374] can 679 be used to measure round-trip delay of a bidirectional Path. The 680 probe query messages in this case either carry the reverse Path 681 information as part of the SR header or set the querier address in 682 the destination address in the IP header. The responder node does 683 not process the PM probe messages and generate response messages. 685 3.3. Checksum Complement 687 For both delay and loss measurement, when the probe packets are 688 updated with timestamp or counter, UDP Checksum field also need 689 updating since these packets are transported over UDP. As an 690 alternative, the Checksum Complement field (2 Bytes) can be 691 optionally updated using the procedure defined in [RFC7820]. The 692 Checksum Complement field can be any unused field in the probe 693 message and is a local behavior. 695 4. Performance Measurement for P2MP SR Policies 697 The procedures for delay and loss measurement described in this 698 document for Point-to-Point (P2P) SR Policies 699 [I-D.spring-segment-routing-policy] are also equally applicable to 700 the Point-to-Multipoint (P2MP) SR Policies 701 [I-D.spring-sr-p2mp-policy] as following: 703 o The querier root node sends probe query messages using the either 704 Spray P2MP segment or TreeSID P2MP segment defined in 706 [I-D.spring-sr-p2mp-policy] over the P2MP SR Policy. 708 o Each responder leaf node sends its IP address in the Source 709 Address of the probe response messages. This allows the querier 710 root node to identify the responder leaf nodes of the P2MP SR 711 Policy. 713 o The P2MP root node measures the end-to-end delay and loss 714 performance for each P2MP leaf node. 716 5. ECMP Support for SR Policies 718 An SR Policy can have ECMPs between the source and transit nodes, 719 between transit nodes and between transit and destination nodes. 720 Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP 721 paths via transit nodes part of that Anycast group. The PM probe 722 messages need to be sent to traverse different ECMP paths to measure 723 performance delay of an SR Policy. 725 Forwarding plane has various hashing functions available to forward 726 packets on specific ECMP paths. Following mechanisms can be used in 727 PM probe messages to take advantage of the hashing function in 728 forwarding plane to influence the path taken by them. 730 o The mechanisms described in [RFC8029] and [RFC5884] for handling 731 ECMPs are also applicable to the performance measurement. In the 732 IP/UDP header of the PM probe messages, Destination Addresses in 733 127/8 range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can 734 be used to exercise a particular ECMP path. As specified in 735 [RFC6437], 3-tuple of Flow Label, Source Address and Destination 736 Address fields in the IPv6 header can also be used. 738 o For SR-MPLS Policy, entropy label [RFC6790] can be used in the PM 739 probe messages. 741 o For SRv6 Policy using SRH, Flow Label in the SRH 742 [I-D.6man-segment-routing-header] of the PM probe messages can be 743 used. 745 6. Sequence Numbers 747 The message formats for DM and LM [RFC6374] can carry either 748 timestamp or sequence number but not both. There are case where both 749 timestamp and sequence number are desired for both DM and LM. 750 Sequence numbers can be useful when some probe query messages are 751 lost or they arrive out of order. In addition, the sequence numbers 752 can be useful for detecting denial-of-service (DoS) attacks on UDP 753 ports. 755 6.1. Sequence Number TLV in Unauthenticated Mode 757 [RFC6374] defines DM and LM probe query and response messages that 758 can include one or more optional TLVs. New TLV Type (value TBA3) is 759 defined in this document to carry sequence number for probe query and 760 response messages for delay and loss measurement. The format of the 761 Sequence Number TLV is shown in Figure 10: 763 0 1 2 3 764 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 1 765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 766 | Type TBA3 | Length | Reserved | 767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 768 | Sequence Number | 769 ~ ~ 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 772 Figure 10: Sequence Number TLV - Unauthenticated Mode 774 o The sequence numbers start with 0 and are incremented by one for 775 each subsequent probe query packet. 777 o The sequence number are independent for DM and LM messages. 779 o The sequence number can be of any length determined by the querier 780 node. 782 o The Sequence Number TLV is optional. 784 o The PM querier node SHOULD only insert one Sequence Number TLV in 785 the probe query message and the responder node in the probe 786 response message SHOULD return the first Sequence Number TLV from 787 the probe query message and ignore the other Sequence Number TLVs 788 if present. 790 o When Sequence Number TLV is added, the DM and LM messages SHOULD 791 NOT carry sequence number in the timestamp field of the message. 793 6.2. Sequence Number TLV in Authenticated Mode 795 The PM probe query and response packet format in authenticated mode 796 includes a key Hashed Message Authentication Code (HMAC) ([RFC2104]) 797 hash. Each probe query and response messages are authenticated by 798 adding Sequence Number with Hashed Message Authentication Code (HMAC) 799 TLV. It can use HMAC-SHA-256 truncated to 128 bits (similarly to the 800 use of it in IPSec defined in [RFC4868]); hence the length of the 801 HMAC field is 16 octets. 803 In authenticated mode, only the sequence number is encrypted, and the 804 other payload fields are sent in clear text. The probe packet MAY 805 include Comp.MBZ (Must Be Zero) variable length field to align the 806 packet on 16 octets boundary. 808 The OWAMP and TWAMP compute HMAC field using HMAC-SHA1 and can also 809 be used with the procedure defined in this document. 811 HMAC uses own key and the definition of the mechanism to distribute 812 the HMAC key is outside the scope of this document. Both the 813 authentication type and key can be user-configured on both the 814 querier and responder nodes. 816 0 1 2 3 817 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 1 818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 819 | Type TBA4 | Length | Reserved | 820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 821 | Sequence Number | 822 ~ ~ 823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 824 ~ Comp.MBZ ~ 825 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 826 | HMAC (16 octets) | 827 | | 828 | | 829 | | 830 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 832 Figure 11: Sequence Number TLV - Authenticated Mode 834 o This TLV is mandatory in the authenticated mode. 836 o The node MUST discard the probe message if HMAC is invalid. 838 o The Sequence Number follows the same processing rule as defined in 839 the unauthenticated mode. 841 7. Security Considerations 843 The performance measurement is intended for deployment in 844 well-managed private and service provider networks. As such, it 845 assumes that a node involved in a measurement operation has 846 previously verified the integrity of the path and the identity of the 847 far end responder node. The security considerations described in 848 Section 8 of [RFC6374] are applicable to this specification, and 849 particular attention should be paid to the last three paragraphs. 851 Use of HMAC-SHA-256 in the authenticated mode defined in this 852 document protects the data integrity of the probe messages. SRv6 has 853 HMAC protection authentication defined for SRH 854 [I-D.6man-segment-routing-header]. Hence, PM probe messages for SRv6 855 may not need authentication mode. Cryptographic measures may be 856 enhanced by the correct configuration of access-control lists and 857 firewalls. 859 8. IANA Considerations 861 IANA is requested to allocate values for the following Return Path 862 TLV Type for RFC 6374 to be carried in PM probe query messages: 864 o Type TBA1: Return Path TLV 866 IANA is requested to allocate the values for the following Sub-TLV 867 Types for the Return Path TLV. 869 o Type 1: SR-MPLS Label Stack of the Reverse SR Policy 871 o Type 2: SR-MPLS Binding SID of the Reverse SR Policy 873 o Type 3: SRv6 Segment List of the Reverse SR Policy 875 o Type 4: SRv6 Binding SID of the Reverse SR Policy 877 IANA is also requested to allocate a value for the following Block 878 Number TLV Type for RFC 6374 to be carried in the PM probe query and 879 response messages for loss measurement: 881 o Type TBA2: Block Number TLV 883 IANA is also requested to allocate a value for the following Sequence 884 Number TLV Types for RFC 6374 to be carried in the PM probe query and 885 response messages for delay and loss measurement: 887 o Type TBA3: Sequence Number TLV in Unauthenticated Mode 888 o Type TBA4: Sequence Number TLV in Authenticated Mode 890 9. References 892 9.1. Normative References 894 [RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 895 August 1980. 897 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 898 Requirement Levels", RFC 2119, March 1997. 900 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 901 Measurement for MPLS networks', RFC 6374, September 2011. 903 [RFC7876] Bryant, S., Sivabalan, S., and Soni, S., "UDP Return Path 904 for Packet Loss and Delay Measurement for MPLS Networks", 905 RFC 7876, July 2016. 907 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 908 2119 Key Words", RFC 8174, May 2017. 910 [I-D.spring-srv6-oam] Ali, Z., et al., "Operations, Administration, 911 and Maintenance (OAM) in Segment Routing Networks with 912 IPv6 Data plane (SRv6)", draft-ali-spring-srv6-oam. 914 9.2. Informative References 916 [IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock 917 Synchronization Protocol for Networked Measurement and 918 Control Systems", March 2008. 920 [Y1731] ITU-T Recommendation Y.1731 (02/08), "OAM functions and 921 mechanisms for Ethernet based networks", February 2008. 923 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 924 Hashing for Message Authentication", RFC 2104, DOI 925 10.17487/RFC2104, February 1997, . 928 [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. 929 Zekauskas, "A One-way Active Measurement Protocol 930 (OWAMP)", RFC 4656, September 2006. 932 [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA- 933 384, and HMAC-SHA-512 with IPsec", RFC 4868,DOI 934 10.17487/RFC4868, May 2007, . 937 [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. 938 Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", 939 RFC 5357, October 2008. 941 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 942 "Bidirectional Forwarding Detection (BFD) for MPLS Label 943 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 944 June 2010. 946 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 947 "IPv6 Flow Label Specification", RFC 6437, November 2011. 949 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 950 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 951 RFC 6790, November 2012. 953 [RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way 954 Active Measurement Protocol (OWAMP) and Two-Way Active 955 Measurement Protocol (TWAMP)", RFC 7820, March 2016. 957 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N., 958 Aldrin, S. and M. Chen, "Detecting Multiprotocol Label 959 Switched (MPLS) Data-Plane Failures", RFC 8029, March 960 2017. 962 [RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive 963 and Hybrid Performance Monitoring", RFC 8321, January 964 2018. 966 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 967 Decraene, B., Litkowski, S., and R. Shakir, "Segment 968 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 969 July 2018, . 971 [I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment 972 Routing Policy Architecture", 973 draft-ietf-spring-segment-routing-policy, work in 974 progress. 976 [I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication 977 Policy for P2MP Service Delivery", 978 draft-voyer-spring-sr-p2mp-policy, work in progress. 980 [I-D.6man-segment-routing-header] Filsfils, C., et al., "IPv6 981 Segment Routing Header (SRH)", 982 draft-ietf-6man-segment-routing-header, work in progress. 984 [I-D.spring-rfc6374-srpm-mpls] Filsfils, C., Gandhi, R. Ed., et al. 985 "Performance Measurement in Segment Routing Networks with 986 MPLS Data Plane", draft-gandhi-spring-rfc6374-srpm-mpls, 987 work in progress. 989 [I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding 990 Label Segment-ID in PCE-based Networks", 991 draft-sivabalan-pce-binding-label-sid, work in progress. 993 [I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in 994 MPLS Based Segment Routing Network", 995 draft-ietf-spring-mpls-path-segment, work in progress. 997 [I-D.ippm-stamp] Mirsky, G. et al. "Simple Two-way Active 998 Measurement Protocol", draft-ietf-ippm-stamp, work in 999 progress. 1001 [BBF.TR-390] "Performance Measurement from IP Edge to Customer 1002 Equipment using TWAMP Light", BBF TR-390, May 2017. 1004 [I-D.spring-ioam-sr-mpls] Gandhi, R. Ed., et al., "Segment Routing 1005 with MPLS Data Plane Encapsulation for In-situ OAM Data", 1006 draft-gandhi-spring-ioam-sr-mpls, work in progress. 1008 Acknowledgments 1010 The authors would like to thank Nagendra Kumar and Carlos Pignataro 1011 for the discussion on SRv6 Performance Measurement. The authors 1012 would like to thank Thierry Couture for various discussions on the 1013 use-cases for the performance measurement in segment routing 1014 networks. The authors would also like to thank Stewart Bryant for 1015 the discussion on UDP port allocation for Performance Measurement and 1016 Greg Mirsky for providing useful comments and suggestions. 1018 Contributors 1020 Sagar Soni 1021 Cisco Systems, Inc. 1022 Email: sagsoni@cisco.com 1024 Patrick Khordoc 1025 Cisco Systems, Inc. 1026 Email: pkhordoc@cisco.com 1028 Zafar Ali 1029 Cisco Systems, Inc. 1030 Email: zali@cisco.com 1032 Authors' Addresses 1034 Rakesh Gandhi (editor) 1035 Cisco Systems, Inc. 1036 Canada 1037 Email: rgandhi@cisco.com 1039 Clarence Filsfils 1040 Cisco Systems, Inc. 1041 Email: cfilsfil@cisco.com 1043 Daniel Voyer 1044 Bell Canada 1045 Email: daniel.voyer@bell.ca 1047 Stefano Salsano 1048 Universita di Roma "Tor Vergata" 1049 Italy 1050 Email: stefano.salsano@uniroma2.it 1052 Pier Luigi Ventre 1053 CNIT 1054 Italy 1055 Email: pierluigi.ventre@cnit.it 1057 Mach(Guoyi) Chen 1058 Huawei 1059 Email: mach.chen@huawei.com