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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) == Unused Reference: 'SRV6-PM-IEEE' is defined on line 631, but no explicit reference was found in the text ** Obsolete normative reference: RFC 8321 (Obsoleted by RFC 9341) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPPM Working Group R. Gandhi, Ed. 3 Internet-Draft C. Filsfils 4 Intended status: Standards Track Cisco Systems, Inc. 5 Expires: August 16, 2021 D. Voyer 6 Bell Canada 7 M. Chen 8 Huawei 9 B. Janssens 10 Colt 11 S. Salsano 12 Universita di Roma "Tor Vergata" 13 February 12, 2021 15 Simple Two-Way Direct Loss Measurement Procedure 16 draft-gandhi-ippm-simple-direct-loss-00 18 Abstract 20 This document defines Simple Two-Way Direct Loss Measurement (DLM) 21 procedure that can be used for Alternate-Marking Method for detecting 22 accurate data packet loss in a network. Specifically, DLM probe 23 packets are defined for both unauthenticated and authenticated modes 24 and they are efficient for hardware-based implementation. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on August 16, 2021. 43 Copyright Notice 45 Copyright (c) 2021 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 62 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 63 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 64 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4 65 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 66 4. Session-Sender Direct Loss Measurement Probe Packet . . . . . 6 67 5. Session-Reflector Direct Loss Measurement Probe Packet . . . 8 68 6. Data Loss Calculation . . . . . . . . . . . . . . . . . . . . 11 69 7. Optional Extensions . . . . . . . . . . . . . . . . . . . . . 12 70 8. Integrity Protection and Confidentiality Protection . . . . . 12 71 9. Operational Considerations . . . . . . . . . . . . . . . . . 12 72 10. Security Considerations . . . . . . . . . . . . . . . . . . . 12 73 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 74 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 75 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 76 12.2. Informative References . . . . . . . . . . . . . . . . . 13 77 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 80 1. Introduction 82 Many Service Provider Service Level Agreements (SLAs) depend on the 83 ability to measure performance loss metric experienced by the 84 Customer data traffic flow. The accurate Customer data packet loss 85 can be measured by using the Direct Loss Measurement (DLM) 86 procedures. Currently there is no efficient active measurement 87 procedure available for accurate data packet loss detection in IP 88 networks. Note that an approach for conducting packet loss 89 measurement in IP networks is documented in [RFC7680]. This approach 90 requires clock synchronization between the measurement points and 91 lacks support for accurate data packet loss measurement. 93 [ITU-Y1731] defines procedures for performance loss monitoring for 94 Ethernet-based networks. Specifically, the Loss Measurement Message 95 (LMM) defined in Section 9.12 of [ITU-Y1731] can be used for accurate 96 frame loss measurement as described in Appendix II of that document. 97 The procedure is specific to the Ethernet-based networks and does not 98 apply to the IP networks. 100 The Simple Two-Way Active Measurement Protocol (STAMP) [RFC8762] 101 provides capabilities for the measurement of various performance 102 metrics in IP networks using test packets. It eliminates the need 103 for control protocol by using configuration data model to provision 104 test sessions. The STAMP can be used for (synthetic or inferred) 105 packet loss measurement based on the Sequence Number in the test 106 packets, however, this method does not provide accurate data packet 107 loss metrics. 109 [RFC8972] defines optional extensions for STAMP. The STAMP test 110 packet with the "Direct Measurement" TLV (Type 5) [RFC8972] can be 111 used for combined timestamp and data packet counter collection. This 112 method, however, has the following limitations when used for 113 detecting data packet loss: 115 o For only direct measurement, the STAMP "Direct Measurement" TLV in 116 the test packet requires the hardware to support timestamps, in 117 addition to data packet counters. One-way delay measurement also 118 requires clock synchronization. 120 o The location of the transmit counter is not at the fixed location 121 in the STAMP test packet with the "Direct Measurement" TLV. Also, 122 the location of the transmit counter on the STAMP Session- 123 Reflector reply test packet is not at the same location as the 124 STAMP Session-Sender test packet using the "Direct Measurement" 125 TLV. This makes it difficult to implement in hardware. 127 o Furthermore, for hardware-based implementation, the optional 128 "Direct Measurement" TLV adds unnecessary processing overhead on 129 the Session-Reflector as not all STAMP Session-Sender test packets 130 carry the "Direct Measurement" TLV. The Session-Reflector needs 131 to search for the presence of this TLV, as there can be multiple 132 TLVs present. 134 o The STAMP "Direct Measurement" TLV does not support 64-bit 135 counters. 137 o The STAMP "Direct Measurement" TLV does not support counters for 138 bytes. 140 o The STAMP "Direct Measurement" TLV does not support counters per 141 traffic class. 143 o The STAMP "Direct Measurement" TLV also does not identify the 144 Block Number of the Direct Measurement, which is required for 145 Alternate-Marking Method [RFC8321] for data packet loss 146 measurement. The AMM also handles the case of the out-of-order 147 data packets. 149 This document defines Simple Two-Way Direct Loss Measurement (DLM) 150 procedure that can be used for Alternate-Marking Method [RFC8321] for 151 detecting accurate data packet loss in a network. Specifically, DLM 152 probe packets are defined for both unauthenticated and authenticated 153 modes and they are efficient for hardware-based implementation. 155 2. Conventions Used in This Document 157 2.1. Requirements Language 159 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 160 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 161 document are to be interpreted as described in [RFC2119] [RFC8174] 162 when, and only when, they appear in all capitals, as shown here. 164 2.2. Abbreviations 166 AMM: Alternate-Marking Method. 168 DLM: Direct Loss Measurement. 170 HMAC: Hashed Message Authentication Code. 172 MBZ: Must be Zero. 174 PM: Performance Measurement. 176 SHA: Secure Hash Algorithm. 178 SSID: Sender Session Identifier. 180 STAMP: Simple Two-Way Active Measurement Protocol. 182 TTL: Time To Live. 184 2.3. Reference Topology 186 As shown in the reference topology, the Session-Sender R1 initiates a 187 Direct Loss Measurement (DLM) probe packet over UDP transport. The 188 Session-Reflector R3 receives the Session-Sender's DLM probe packet 189 and acts according to the local configuration. The Session-Reflector 190 R3 transmits a DLM reply probe packet to the Session-Sender R1. 192 C1 C2 193 / \ 194 +-------+ DLM Probe Packet +-------+ 195 | | - - - - - - - - - - - ->| | 196 | R1 |=========================| R3 | 197 | |<- - - - - - - - - - - - | | 198 +-------+ DLM Reply Probe Packet +-------+ 199 \ / 200 C4 C3 202 Session-Sender Session-Reflector 204 Reference Topology 206 3. Overview 208 For accurate data packet loss detection, the DLM probe packets are 209 transmitted by the Session-Sender over UDP transport, and are used to 210 collect the transmit and receive counters for the data traffic flow 211 under measurement. The DLM reply probe packets are transmitted by 212 the Session-Reflector to collect the transmit and receive counters 213 for the data traffic flow under measurement in the reverse direction. 215 The DLM probe packets carry user-configured destination UDP port. 216 The destination UDP port 862 is not used for the DLM probe packets. 217 The user-configured destination UDP port follows the guidelines 218 described in Section 4.1 of [RFC8762]. Different destination UDP 219 port is used for DLM probe packets than the STAMP test packets 220 defined in [RFC8762]. Hence, the Session-Sender and the Session- 221 Reflector do not require backwards compatibility and support for 222 STAMP. 224 A DLM session is identified by the 4-tuple (source and destination IP 225 addresses, source and destination UDP port numbers). A DLM Session- 226 Sender MAY generate a locally unique Sender Session Identifier 227 (SSID). The SSID is a two-octet, non-zero unsigned integer. The 228 SSID generation policy is implementation specific. An implementation 229 MUST NOT assign the same identifier to different DLM sessions. A 230 Session-Sender MAY use the SSID to identify a DLM session. If the 231 SSID is used, it MUST be present in each probe packet of the given 232 DLM session. 234 The DLM Session-Reflector operates in the Stateless mode. The DLM 235 Session-Reflector does not maintain session state and will use the 236 value in the Sequence Number field in the received probe packet as 237 the value for the Sequence Number field in the reply probe packet. 238 As a result, values in the Sequence Number and Session-Sender 239 Sequence Number fields are the same in this mode. 241 4. Session-Sender Direct Loss Measurement Probe Packet 243 In this document, base Session-Sender DLM probe packet formats are 244 defined as shown in Figure 1 and Figure 2 for unauthenticated and 245 authenticated modes, respectively. They are stand-alone DLM probe 246 packet formats to carry the counters for the data traffic flow under 247 measurement. The DLM probe packet formats are similar to the base 248 STAMP test packet formats (for example the locations of the Counters 249 and Timestamps). 251 0 1 2 3 252 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 1 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | Sequence Number | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | Transmit Counter (C1) | 257 | | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 |X|B|T| DSCP | Block Number| SSID | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | | 262 | | 263 | MBZ (28 octets) | 264 | | 265 | | 266 | | 267 | | 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 270 Figure 1: Session-Sender Direct Loss Measurement Probe Packet - 271 Unauthenticated Mode 273 0 1 2 3 274 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 1 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | Sequence Number | 277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 | MBZ (12 octets) | 279 | | 280 | | 281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 282 | Transmit Counter (C1) | 283 | | 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 285 |X|B|T| DSCP | Block Number| SSID | 286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 287 | | 288 | MBZ (68 octets) | 289 . . 290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 291 | | 292 | HMAC (16 octets) | 293 | | 294 | | 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 Figure 2: Session-Sender Direct Loss Measurement Probe Packet - 298 Authenticated Mode 300 Fields are defined as the following: 302 Sequence Number (32-bit): For each new DLM session, its value starts 303 at zero and is incremented by one with each transmitted DLM probe 304 packet. The Sequence Number helps to check the DLM session status as 305 active or not active. 307 Transmit Counter (64-bit): The number of packets or octets 308 transmitted by the Session-Sender in the DLM probe packet. The 309 counter is always written at the well-known fixed location in the DLM 310 probe packet. This is an important property for hardware-based 311 implementation. Counter is for the data traffic flow under 312 measurement. 314 XBT Flags (3-bit): The meanings of the Flag bits are: 316 X: Extended counter format indicator. Indicates the use of 317 extended (64-bit) counter values. Initialized to 1 upon creation 318 (and prior to transmission) of a DLM probe packet. Set to 0 when 319 the DLM probe packet is transmitted or received over an interface 320 that writes 32-bit counter values. 322 B: Octet (byte) count. When set to 1, indicates that the Counter 323 fields represent octet counts. The octet count applies to all 324 packets within the DLM scope, and the octet count of a packet 325 transmitted or received includes the total length of that packet 326 (but excludes headers, labels, or framing of the channel itself). 327 When set to 0, indicates that the Counter fields represent packet 328 counts. 330 T: Traffic-class-specific measurement indicator. Set to 1 when 331 the DLM session is scoped to data packets of a particular traffic 332 class (DSCP value), and 0 otherwise. When set to 1, the DSCP 333 field of the DLM probe packet indicates the measured traffic 334 class. 336 DSCP (6-bit): DSCP of the data traffic flow being measured when T 337 flag is set. 339 Block Number (7-bit): The Direct Loss Measurement using Alternate- 340 Marking Method [RFC8321] requires to collect Block Number of the 341 counters for the data traffic flow under measurement. To be able to 342 correlate the transmit and receive counters of the matching Block 343 Number, the Block Number of the counters carried in the DLM probe 344 packets. 346 SSID (16-bit): DLM Sender Session Identifier. 348 HMAC: The use of the HMAC field is described in Section 4.4 of 349 [RFC8762]. HMAC uses its own key and the mechanism to distribute the 350 HMAC key is outside the scope of this document. 352 MBZ: Must be Zero. It MUST be all zeroed on the transmission and 353 MUST be ignored on receipt. 355 5. Session-Reflector Direct Loss Measurement Probe Packet 357 The Session-Reflector receives the DLM Session-Sender probe packet 358 and verifies it. If the DLM probe packet is validated, the Session- 359 Reflector that supports this specification prepares and transmits the 360 DLM reply probe packet. In this document, Session-Reflector DLM 361 reply probe packet formats are defined as shown in Figure 3 and 362 Figure 4, for unauthenticated and authenticated modes, respectively. 364 0 1 2 3 365 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 1 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | Sequence Number | 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 369 | Transmit Counter (C3) | 370 | | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 |X|B|T| DSCP | Block Number| SSID | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 | Receive Counter (C2) | 375 | | 376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 | Session-Sender Sequence Number | 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 | Session-Sender Counter (C1) | 380 | | 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 |FLAGS| Ses-DSCP |Ses-Block Num| MBZ (2 octets) | 383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 384 |Ses-Sender TTL | MBZ | 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 Figure 3: Session-Reflector Direct Loss Measurement Probe Packet - 388 Unauthenticated Mode 390 0 1 2 3 391 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 1 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | Sequence Number | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | MBZ (12 octets) | 396 | | 397 | | 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | Transmit Counter (C3) | 400 | | 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 402 |X|B|T| DSCP | Block Number| SSID | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 404 | MBZ (4 octets) | 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 | Receive Counter (C2) | 407 | | 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 | MBZ (8 octets) | 410 | | 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 412 | Session-Sender Sequence Number | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | MBZ (12 octets) | 415 | | 416 | | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | Session-Sender Counter (C1) | 419 | | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 |FLAGS| Ses-DSCP |Ses-Block Num| MBZ (2 octets) | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | MBZ (4 octets) | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 |Ses-Sender TTL | | 426 +-+-+-+-+-+-+-+-+ | 427 | MBZ (15 octets) | 428 | | 429 | | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | | 432 | HMAC (16 octets) | 433 | | 434 | | 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 Figure 4: Session-Reflector Direct Loss Measurement Probe Packet - 438 Authenticated Mode 440 Fields are defined as the following: 442 Sequence Number (32-bit): This is the exact copy of the Sequence 443 Number from the received Session-Sender DLM probe packet that allows 444 Stateless mode of Session-Reflector. 446 Transmit Counter (64-bit): The number of packets or octets 447 transmitted by the Session-Reflector in the DLM reply probe packet. 448 Counter is for the reverse direction data traffic flow under 449 measurement. The Session-Reflector writes the Transmit Counter at 450 the same location in the DLM reply probe packet as the Session-Sender 451 DLM probe packet. This is an important property for hardware-based 452 implementation. 454 FLAGS (3-bit): The XBT Flags for the reverse direction data traffic 455 flow under measurement set using the same procedure defined for the 456 Session-Sender DLM probe packet. 458 DSCP (6-bit): Set for the reverse direction data traffic flow under 459 measurement using the same procedure defined for the Session-Sender 460 DLM probe packet. 462 Block Number (7-bit): Set for the reverse direction data traffic flow 463 under measurement using the same procedure defined for the Session- 464 Sender DLM probe packet. 466 SSID: SSID is the exact copy of the SSID in the received Session- 467 Sender DLM probe packet. 469 Receive Counter (64-bit): The number of packets or octets received at 470 the Session-Reflector. It is written by the Session-Reflector in the 471 DLM reply probe packet. Counter is for the data traffic flow under 472 measurement. 474 Session-Sender Counter (64-bit): This is the exact copy of the 475 Transmit Counter from the received Session-Sender DLM probe packet. 477 Session-Sender Sequence Number (32-bit): This is the exact copy of 478 the Sequence Number from the received Session-Sender DLM probe 479 packet. 481 Session-Sender Block Number: This is the exact copy of the Block 482 Number from the received Session-Sender DLM probe packet. 484 Session-Sender FLAGS: This is the exact copy of the XBT Flags from 485 the received Session-Sender DLM probe packet. 487 Session-Sender DSCP: This is the exact copy of the DSCP from the 488 received Session-Sender DLM probe packet. 490 Session-Sender TTL: The Session-Sender TTL field is one octet long, 491 and its value is the copy of the TTL field in IPv4 (or Hop Limit in 492 IPv6) from the received Session-Sender DLM probe packet. 494 6. Data Loss Calculation 496 Using the Counters C1, C2, C3 and C4 as per reference topology, from 497 the nth and (n-1)th DLM probe packets, packet loss and byte loss for 498 the data traffic flow can be calculated as follows: 500 Transmit Loss TxL[ n-1, n] = (C1[ n] - C1[ n-1]) - (C2[ n] - C2[ 501 n-1]) 503 Receive Loss RxL[ n-1, n] = (C3[ n] - C3[ n-1]) - (C4[ n] - C4[ n-1]) 505 The Total Transmit and Receive Loss are calculated as follows: 507 Total Transmit Loss = TxL[ 1, 2] + TxL[ 2, 3] + ... 509 Total Receive Loss = RxL[ 1, 2] + RxL[ 2, 3] + ... 511 These values are updated each time a DLM reply probe packet is 512 received and processed at the Session-Sender, and they represent the 513 Total Transmit and Total Receive Loss since the DLM session was 514 initiated. When computing the values TxL[n-1,n] and RxL[n-1,n], the 515 possibility of counter wrap must be taken into account. 517 When using Alternate-Marking Method, all Counters used for loss 518 calculation belongs to the same Block Number, as described in 519 Section 3.1 of [RFC8321]. 521 7. Optional Extensions 523 There are currently no optional (TLV) extensions defined for the DLM 524 probe packets. 526 8. Integrity Protection and Confidentiality Protection 528 The integrity protection and confidentiality protection specified in 529 [RFC8762] also apply to the procedures defined in this document. 531 9. Operational Considerations 533 The operational considerations specified in [RFC8762] also apply to 534 the procedures defined in this document. 536 10. Security Considerations 538 The performance measurement is intended for deployment in well- 539 managed private and service provider networks. As such, it assumes 540 that a node involved in a measurement operation has previously 541 verified the integrity of the path and the identity of the Session- 542 Reflector. 544 If desired, attacks can be mitigated by performing basic validation 545 and sanity checks, at the Session-Sender, of the Counter fields in 546 received DLM reply probe packets. The minimal state associated with 547 these protocols also limits the extent of measurement disruption that 548 can be caused by a corrupt or invalid packet to a single measurement 549 cycle. 551 Use of HMAC-SHA-256 in the authenticated mode protects the data 552 integrity of the probe packets. Cryptographic measures may be 553 enhanced by the correct configuration of access-control lists and 554 firewalls. 556 The security considerations specified in [RFC8762] also apply to the 557 procedure defined in this document. 559 11. IANA Considerations 561 This document has no IANA actions. 563 12. References 565 12.1. Normative References 567 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 568 Requirement Levels", BCP 14, RFC 2119, 569 DOI 10.17487/RFC2119, March 1997, 570 . 572 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 573 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 574 May 2017, . 576 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 577 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 578 "Alternate-Marking Method for Passive and Hybrid 579 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 580 January 2018, . 582 [RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple 583 Two-Way Active Measurement Protocol", RFC 8762, 584 DOI 10.17487/RFC8762, March 2020, 585 . 587 12.2. Informative References 589 [RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, 590 Ed., "A One-Way Loss Metric for IP Performance Metrics 591 (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 592 2016, . 594 [RFC8972] Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A., 595 and E. Ruffini, "Simple Two-Way Active Measurement 596 Protocol Optional Extensions", RFC 8972, 597 DOI 10.17487/RFC8972, January 2021, 598 . 600 [ITU-Y1731] 601 Recommendation ITU-TG.8013/Y.1731: 602 https://www.itu.int/rec/T-REC-G.8013-201508-I/en, "G.8013/ 603 Y.1731 : Operations, administration and maintenance (OAM) 604 functions and mechanisms for Ethernet-based networks", 605 August 2015. 607 [SRV6-PM-TNSM] 608 Loreti, P., Mayer, A., Lungaroni, P., Lombardo, F., 609 Scarpitta, C., Sidoretti, G., Bracciale, L., Ferrari, M., 610 Salsano, S., Abdelsalam, A., Gandhi, R., and C. Filsfils, 611 IEEE Transactions on Network and Service Management, 612 "SRv6-PM: Performance Monitoring of SRv6 Networks with a 613 Cloud-Native Architecture: 614 https://arxiv.org/pdf/2007.08633.pdf", February 2021. 616 [SRV6-PM-IEEE] 617 Loreti, P., Mayer, A., Lungaroni, P., Salsano, S., Gandhi, 618 R., and C. Filsfils, IEEE International Conference on High 619 Performance Switching and Routing, "Implementation of 620 Accurate Per-Flow Packet Loss Monitoring in Segment 621 Routing over IPv6 Networks: 622 https://arxiv.org/pdf/2004.11414.pdf", May 2020. 624 Acknowledgments 626 The authors would like to thank Greg Mirsky, Tianran Zhou, Gyan 627 Mishra, Zhenqiang Li, Reshad Rahman, Cheng Li, and Yali Wang for the 628 comments on Direct Loss Measurement. The authors would like to thank 629 Pierpaolo Loreti and the team for the Open Source implementation of 630 SRv6-PM Loss Monitoring and its publications in [SRV6-PM-TNSM] and 631 [SRV6-PM-IEEE]. The authors would like to acknowledge the earlier 632 work on the loss measurement using TWAMP described in draft-xiao- 633 ippm-twamp-ext-direct-loss. 635 Authors' Addresses 637 Rakesh Gandhi (editor) 638 Cisco Systems, Inc. 639 Canada 641 Email: rgandhi@cisco.com 643 Clarence Filsfils 644 Cisco Systems, Inc. 646 Email: cfilsfil@cisco.com 647 Daniel Voyer 648 Bell Canada 650 Email: daniel.voyer@bell.ca 652 Mach(Guoyi) Chen 653 Huawei 655 Email: mach.chen@huawei.com 657 Bart Janssens 658 Colt 660 Email: Bart.Janssens@colt.net 662 Stefano Salsano 663 Universita di Roma "Tor Vergata" 664 Italy 666 Email: stefano.salsano@uniroma2.it