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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 632, 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: 10 February 2022 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 9 August 2021 15 Simple Two-Way Direct Loss Measurement Procedure 16 draft-gandhi-ippm-simple-direct-loss-01 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 10 February 2022. 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 (https://trustee.ietf.org/ 50 license-info) in effect on the date of publication of this document. 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. Code Components 53 extracted from this document must include Simplified BSD License text 54 as described in Section 4.e of the Trust Legal Provisions and are 55 provided without warranty as described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 61 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 62 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 63 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 5 64 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4. Session-Sender Direct Loss Measurement Probe Packet . . . . . 6 66 5. Session-Reflector Direct Loss Measurement Probe Packet . . . 9 67 6. Data Loss Calculation . . . . . . . . . . . . . . . . . . . . 12 68 7. Optional Extensions . . . . . . . . . . . . . . . . . . . . . 12 69 8. Integrity Protection and Confidentiality Protection . . . . . 12 70 9. Operational Considerations . . . . . . . . . . . . . . . . . 13 71 10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 72 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 73 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 74 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 75 12.2. Informative References . . . . . . . . . . . . . . . . . 14 76 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 79 1. Introduction 81 Many Service Provider Service Level Agreements (SLAs) depend on the 82 ability to measure performance loss metric experienced by the 83 Customer data traffic flow. Accurate Customer data packet loss can 84 be measured by using a Direct Loss Measurement (DLM) procedure. 85 Currently there is no efficient active measurement procedure 86 available for accurate data packet loss detection in IP networks. 87 Note that an approach for conducting packet loss measurement in IP 88 networks is documented in [RFC7680]. This approach requires clock 89 synchronization between the measurement points and lacks support for 90 accurate data packet loss measurement. 92 [ITU-Y1731] defines procedures for performance loss monitoring for 93 Ethernet-based networks. Specifically, the Loss Measurement Message 94 (LMM) defined in Section 9.12 of [ITU-Y1731] can be used for accurate 95 frame loss measurement as described in Appendix II of that document. 96 The procedure is specific to the Ethernet-based networks and does not 97 apply to the IP networks. 99 The Simple Two-Way Active Measurement Protocol (STAMP) provides 100 capabilities for the measurement of various performance metrics in IP 101 networks [RFC8762] without the use of a control channel to pre-signal 102 session parameters. The STAMP can be used for (synthetic or 103 inferred) packet loss measurement based on the Sequence Number in the 104 test packets, however, this method can only provide approximate 105 packet loss metrics. 107 [RFC8972] defines optional extensions for STAMP. The STAMP test 108 packet with the "Direct Measurement" TLV (Type 5) [RFC8972] can be 109 used for combined timestamps and data packet counters collection. 110 This method, however, has the following limitations when used for 111 detecting data packet loss: 113 * For only direct measurement, the STAMP "Direct Measurement" TLV in 114 the test packet requires the hardware to support timestamps, in 115 addition to data packet counters. One-way delay measurement also 116 requires clock synchronization between the Session-Sender and 117 Session-Reflector nodes. 119 * The location of the transmit counter is not at the fixed location 120 in the STAMP test packet with the "Direct Measurement" TLV. Also, 121 the location of the transmit counter on the STAMP Session- 122 Reflector reply test packet is not at the same location as the 123 STAMP Session-Sender test packet using the "Direct Measurement" 124 TLV. This makes it difficult to implement in hardware, e.g., for 125 point-to-point links and circuits. 127 * 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 and also there can be multiple 131 TLV Types present. 133 * The STAMP "Direct Measurement" TLV does not support 64-bit 134 counters. 136 * The STAMP "Direct Measurement" TLV does not support counters for 137 bytes. 139 * The STAMP "Direct Measurement" TLV does not support counters per 140 traffic class. 142 * The STAMP "Direct Measurement" TLV also does not identify the 143 Block Number of the Direct Measurement, which is required for 144 Alternate-Marking Method [RFC8321] for data packet loss 145 measurement. The AMM also handles the case of out-of-order data 146 packets. 148 This document defines Simple Two-Way Direct Loss Measurement (DLM) 149 procedure that can be used for Alternate-Marking Method [RFC8321] for 150 detecting accurate data packet loss in a network. Specifically, DLM 151 probe packets are defined for both unauthenticated and authenticated 152 modes and they are efficient for hardware-based implementation. 154 2. Conventions Used in This Document 156 2.1. Requirements Language 158 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 159 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 160 document are to be interpreted as described in [RFC2119] [RFC8174] 161 when, and only when, they appear in all capitals, as shown here. 163 2.2. Abbreviations 165 AMM: Alternate-Marking Method. 167 DLM: Direct Loss Measurement. 169 HMAC: Hashed Message Authentication Code. 171 MBZ: Must be Zero. 173 PM: Performance Measurement. 175 SHA: Secure Hash Algorithm. 177 SSID: Sender Session Identifier. 179 STAMP: Simple Two-Way Active Measurement Protocol. 181 TTL: Time To Live. 183 2.3. Reference Topology 185 As shown in the reference topology, the Session-Sender S1 initiates a 186 Direct Loss Measurement (DLM) probe packet over UDP transport. The 187 Session-Reflector R1 receives the Session-Sender's DLM probe packet 188 and acts according to the local configuration. The Session-Reflector 189 R1 transmits a DLM reply probe packet to the Session-Sender S1. 191 C1 C2 192 / \ 193 +-------+ DLM Probe Packet +-------+ 194 | | - - - - - - - - - - - ->| | 195 | S1 |=========================| R1 | 196 | |<- - - - - - - - - - - - | | 197 +-------+ DLM Reply Probe Packet +-------+ 198 \ / 199 C4 C3 201 Session-Sender Session-Reflector 203 Reference Topology 205 3. Overview 207 For accurate data packet loss detection, the DLM probe packets are 208 transmitted by the Session-Sender over UDP transport, and are used to 209 collect the transmit and receive counters for the data traffic flow 210 under measurement. The DLM reply probe packets are transmitted by 211 the Session-Reflector to collect the transmit and receive counters 212 for the data traffic flow under measurement in the reverse direction. 214 The DLM probe packets carry user-configured destination UDP port. 215 The destination UDP port 862 is not used for the DLM probe packets. 216 The user-configured destination UDP port follows the guidelines 217 described in Section 4.1 of [RFC8762]. Different destination UDP 218 port is used for DLM probe packets than the STAMP test packets 219 defined in [RFC8762]. Hence, the Session-Sender and the Session- 220 Reflector do not require backwards compatibility and support for 221 STAMP. 223 A DLM session is identified by the 4-tuple (source and destination IP 224 addresses, source and destination UDP port numbers). A DLM Session- 225 Sender MAY generate a locally unique Sender Session Identifier 226 (SSID). The SSID is a two-octet, non-zero unsigned integer. The 227 SSID generation policy is implementation specific. An implementation 228 MUST NOT assign the same identifier to different DLM sessions. A 229 Session-Sender MAY use the SSID to identify a DLM session. If the 230 SSID is used, it MUST be present in each probe packet of the given 231 DLM session. 233 The DLM Session-Reflector operates in the Stateless mode. The DLM 234 Session-Reflector does not maintain session state and will use the 235 value in the Sequence Number field in the received probe packet as 236 the value for the Sequence Number field in the reply probe packet. 237 As a result, values in the Sequence Number and Session-Sender 238 Sequence Number fields are the same in this mode. 240 In this document, the examples of DLM probe packets are shown with 241 UDP header, however, the packets can be encapsuated with a different 242 header based on the the transport protocol used in the network. 244 4. Session-Sender Direct Loss Measurement Probe Packet 246 In this document, base Session-Sender DLM probe packet formats are 247 defined as shown in Figure 1 and Figure 2 for unauthenticated and 248 authenticated modes, respectively. They are stand-alone DLM probe 249 packet formats to carry the counters for the data traffic flow under 250 measurement. The DLM probe packet formats are similar to the base 251 STAMP test packet formats (for example the locations of the Counters 252 and Timestamps). 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 | Sequence Number | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 | Transmit Counter (C1) | 260 | | 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 |X|B|T| DSCP | Block Number| SSID | 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 | | 265 | | 266 | MBZ (28 octets) | 267 | | 268 | | 269 | | 270 | | 271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 273 Figure 1: Session-Sender Direct Loss Measurement Probe Packet - 274 Unauthenticated Mode 276 0 1 2 3 277 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 1 278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 279 | Sequence Number | 280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 281 | MBZ (12 octets) | 282 | | 283 | | 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 285 | Transmit Counter (C1) | 286 | | 287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 288 |X|B|T| DSCP | Block Number| SSID | 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | | 291 | MBZ (68 octets) | 292 . . 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 | | 295 | HMAC (16 octets) | 296 | | 297 | | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 Figure 2: Session-Sender Direct Loss Measurement Probe Packet - 301 Authenticated Mode 303 Fields are defined as the following: 305 Sequence Number (32-bit): For each new DLM session, its value starts 306 at zero and is incremented by one with each transmitted DLM probe 307 packet. The Sequence Number helps to check the DLM session state as 308 active or not active, as well as detect probe packet drops. 310 Transmit Counter (64-bit): The number of packets or octets 311 transmitted by the Session-Sender in the DLM probe packet. The 312 counter is always written at the well-known fixed location in the DLM 313 probe packet. This is an important property for hardware-based 314 implementation, e.g., for point-to-point links and circuits. Counter 315 is for the data traffic flow under measurement. 317 XBT Flags (3-bit): The meanings of the Flag bits are: 318 X: Extended counter format indicator. Indicates the use of 319 extended (64-bit) counter values. Initialized to 1 upon creation 320 (and prior to transmission) of a DLM probe packet. Set to 0 when 321 the DLM probe packet is transmitted or received over an interface 322 that writes 32-bit counter values. 324 B: Octet (byte) count. When set to 1, indicates that the Counter 325 fields represent octet counts. The octet count applies to all 326 packets within the DLM scope, and the octet count of a packet 327 transmitted or received includes the total length of that packet 328 (but excludes headers, labels, or framing of the channel itself). 329 When set to 0, indicates that the Counter fields represent packet 330 counts. 332 T: Traffic-class-specific measurement indicator. Set to 1 when 333 the DLM session is scoped to data packets of a particular traffic 334 class (DSCP value), and 0 otherwise. When set to 1, the DSCP 335 field of the DLM probe packet indicates the measured traffic 336 class. 338 DSCP (6-bit): DSCP of the data traffic flow being measured when T 339 flag is set. 341 Block Number (7-bit): The Direct Loss Measurement using Alternate- 342 Marking Method [RFC8321] requires to collect Block Number of the 343 counters for the data traffic flow under measurement. To be able to 344 correlate the transmit and receive counters of the matching Block 345 Number, the Block Number of the counters carried in the DLM probe 346 packets. 348 SSID (16-bit): DLM Sender Session Identifier. 350 HMAC: The use of the HMAC field is described in Section 4.4 of 351 [RFC8762]. HMAC uses its own key and the mechanism to distribute the 352 HMAC key is outside the scope of this document. 354 MBZ: Must be Zero. It MUST be all zeroed on the transmission and 355 MUST be ignored on receipt. 357 5. Session-Reflector Direct Loss Measurement Probe Packet 359 The Session-Reflector receives the DLM Session-Sender probe packet 360 and verifies it. If the DLM probe packet is validated, the Session- 361 Reflector that supports this specification prepares and transmits the 362 DLM reply probe packet. In this document, Session-Reflector DLM 363 reply probe packet formats are defined as shown in Figure 3 and 364 Figure 4, for unauthenticated and authenticated modes, respectively. 366 0 1 2 3 367 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 1 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 369 | Sequence Number | 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | Transmit Counter (C3) | 372 | | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 |X|B|T| DSCP | Block Number| SSID | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 376 | Receive Counter (C2) | 377 | | 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 | Session-Sender Sequence Number | 380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 381 | Session-Sender Counter (C1) | 382 | | 383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 384 |FLAGS| Ses-DSCP |Ses-Block Num| MBZ (2 octets) | 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 |Ses-Sender TTL | MBZ | 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 Figure 3: Session-Reflector Direct Loss Measurement Probe Packet - 390 Unauthenticated Mode 392 0 1 2 3 393 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 1 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | Sequence Number | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | MBZ (12 octets) | 398 | | 399 | | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | Transmit Counter (C3) | 402 | | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 404 |X|B|T| DSCP | Block Number| SSID | 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 | MBZ (4 octets) | 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 | Receive Counter (C2) | 409 | | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | MBZ (8 octets) | 412 | | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Session-Sender Sequence Number | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | MBZ (12 octets) | 417 | | 418 | | 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 | Session-Sender Counter (C1) | 421 | | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 |FLAGS| Ses-DSCP |Ses-Block Num| MBZ (2 octets) | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 | MBZ (4 octets) | 426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 427 |Ses-Sender TTL | | 428 +-+-+-+-+-+-+-+-+ | 429 | MBZ (15 octets) | 430 | | 431 | | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | | 434 | HMAC (16 octets) | 435 | | 436 | | 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 438 Figure 4: Session-Reflector Direct Loss Measurement Probe Packet - 439 Authenticated Mode 441 Fields are defined as the following: 443 Sequence Number (32-bit): This is the exact copy of the Sequence 444 Number from the received Session-Sender DLM probe packet that allows 445 Stateless mode of Session-Reflector. 447 Transmit Counter (64-bit): The number of packets or octets 448 transmitted by the Session-Reflector in the DLM reply probe packet. 449 Counter is for the reverse direction data traffic flow under 450 measurement. The Session-Reflector writes the Transmit Counter at 451 the same location in the DLM reply probe packet as the Session-Sender 452 DLM probe packet. This is an important property for hardware-based 453 implementation. 455 XBT Flags (3-bit): The XBT Flags for the reverse direction data 456 traffic flow under measurement set using the same procedure defined 457 for the Session-Sender DLM probe packet. 459 DSCP (6-bit): Set for the reverse direction data traffic flow under 460 measurement using the same procedure defined for the Session-Sender 461 DLM probe packet. 463 Block Number (7-bit): Set for the reverse direction data traffic flow 464 under measurement using the same procedure defined for the Session- 465 Sender DLM probe packet. 467 SSID: SSID is the exact copy of the SSID in the received Session- 468 Sender DLM probe packet. 470 Receive Counter (64-bit): The number of packets or octets received at 471 the Session-Reflector. It is written by the Session-Reflector in the 472 DLM reply probe packet. Counter is for the data traffic flow under 473 measurement. 475 Session-Sender Counter (64-bit): This is the exact copy of the 476 Transmit Counter from the received Session-Sender DLM probe packet. 478 Session-Sender Sequence Number (32-bit): This is the exact copy of 479 the Sequence Number from the received Session-Sender DLM probe 480 packet. 482 Session-Sender Block Number: This is the exact copy of the Block 483 Number from the received Session-Sender DLM probe packet. 485 Session-Sender FLAGS: This is the exact copy of the XBT Flags from 486 the received Session-Sender DLM probe packet. 488 Session-Sender DSCP: This is the exact copy of the DSCP from the 489 received Session-Sender DLM probe packet. 491 Session-Sender TTL: The Session-Sender TTL field is one octet long, 492 and its value is the copy of the TTL field in IPv4 (or Hop Limit in 493 IPv6) from the received Session-Sender DLM probe packet. 495 6. Data Loss Calculation 497 Using the Counters C1, C2, C3 and C4 as per reference topology, from 498 the nth and (n-1)th DLM probe packets, packet loss and byte loss for 499 the data traffic flow can be calculated as follows: 501 Transmit Loss TxL[ n-1, n] = (C1[ n] - C1[ n-1]) - (C2[ n] - C2[ 502 n-1]) 504 Receive Loss RxL[ n-1, n] = (C3[ n] - C3[ n-1]) - (C4[ n] - C4[ n-1]) 506 The Total Transmit and Receive Loss are calculated as follows: 508 Total Transmit Loss = TxL[ 1, 2] + TxL[ 2, 3] + ... 510 Total Receive Loss = RxL[ 1, 2] + RxL[ 2, 3] + ... 512 These values are updated each time a DLM reply probe packet is 513 received and processed at the Session-Sender, and they represent the 514 Total Transmit and Total Receive Loss since the DLM session was 515 initiated. When computing the values TxL[n-1,n] and RxL[n-1,n], the 516 possibility of counter wrap must be taken into account. 518 When using Alternate-Marking Method, all Counters used for loss 519 calculation belongs to the same Block Number, as described in 520 Section 3.1 of [RFC8321]. 522 7. Optional Extensions 524 There are currently no optional (TLV) extensions defined for the DLM 525 probe packets. 527 8. Integrity Protection and Confidentiality Protection 529 The integrity protection and confidentiality protection specified in 530 [RFC8762] also apply to the procedures defined in this document. 532 9. Operational Considerations 534 The operational considerations specified in [RFC8762] also apply to 535 the procedures defined in this document. 537 10. Security Considerations 539 The DLM protocol is intended for deployment in limited domains 540 [RFC8799]. As such, it assumes that a node involved in DLM protocol 541 operation has previously verified the integrity of the path and the 542 identity of the far-end Session-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 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 probe packet to a single probe 549 cycle. 551 The security considerations specified in [RFC8762] and [RFC8972] also 552 apply to the protocol defined in this document. Specifically, the 553 message integrity protection using HMAC, as defined in [RFC8762] 554 Section 4.4, also apply to the procedure described in this document. 556 11. IANA Considerations 558 This document has no IANA actions. 560 12. References 562 12.1. Normative References 564 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 565 Requirement Levels", BCP 14, RFC 2119, 566 DOI 10.17487/RFC2119, March 1997, 567 . 569 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 570 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 571 May 2017, . 573 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 574 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 575 "Alternate-Marking Method for Passive and Hybrid 576 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 577 January 2018, . 579 [RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple 580 Two-Way Active Measurement Protocol", RFC 8762, 581 DOI 10.17487/RFC8762, March 2020, 582 . 584 12.2. Informative References 586 [RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, 587 Ed., "A One-Way Loss Metric for IP Performance Metrics 588 (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 589 2016, . 591 [RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet 592 Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020, 593 . 595 [RFC8972] Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A., 596 and E. Ruffini, "Simple Two-Way Active Measurement 597 Protocol Optional Extensions", RFC 8972, 598 DOI 10.17487/RFC8972, January 2021, 599 . 601 [ITU-Y1731] 602 Recommendation ITU-TG.8013/Y.1731: 603 https://www.itu.int/rec/T-REC-G.8013-201508-I/en, "G.8013/ 604 Y.1731 : Operations, administration and maintenance (OAM) 605 functions and mechanisms for Ethernet-based networks", 606 August 2015. 608 [SRV6-PM-TNSM] 609 Loreti, P., Mayer, A., Lungaroni, P., Lombardo, F., 610 Scarpitta, C., Sidoretti, G., Bracciale, L., Ferrari, M., 611 Salsano, S., Abdelsalam, A., Gandhi, R., and C. Filsfils, 612 IEEE Transactions on Network and Service Management, 613 "SRv6-PM: Performance Monitoring of SRv6 Networks with a 614 Cloud-Native Architecture: 615 https://arxiv.org/pdf/2007.08633.pdf", February 2021. 617 [SRV6-PM-IEEE] 618 Loreti, P., Mayer, A., Lungaroni, P., Salsano, S., Gandhi, 619 R., and C. Filsfils, IEEE International Conference on High 620 Performance Switching and Routing, "Implementation of 621 Accurate Per-Flow Packet Loss Monitoring in Segment 622 Routing over IPv6 Networks: 623 https://arxiv.org/pdf/2004.11414.pdf", May 2020. 625 Acknowledgments 627 The authors would like to thank Greg Mirsky, Tianran Zhou, Gyan 628 Mishra, Zhenqiang Li, Reshad Rahman, Cheng Li, and Yali Wang for the 629 comments on Direct Loss Measurement. The authors would like to thank 630 Pierpaolo Loreti and the team for the Open Source implementation of 631 SRv6-PM Loss Monitoring and its publications in [SRV6-PM-TNSM] and 632 [SRV6-PM-IEEE]. The authors would like to acknowledge the earlier 633 work on the loss measurement using TWAMP described in draft-xiao- 634 ippm-twamp-ext-direct-loss. 636 Authors' Addresses 638 Rakesh Gandhi (editor) 639 Cisco Systems, Inc. 640 Canada 642 Email: rgandhi@cisco.com 644 Clarence Filsfils 645 Cisco Systems, Inc. 647 Email: cfilsfil@cisco.com 649 Daniel Voyer 650 Bell Canada 652 Email: daniel.voyer@bell.ca 654 Mach(Guoyi) Chen 655 Huawei 657 Email: mach.chen@huawei.com 659 Bart Janssens 660 Colt 662 Email: Bart.Janssens@colt.net 664 Stefano Salsano 665 Universita di Roma "Tor Vergata" 666 Italy 667 Email: stefano.salsano@uniroma2.it