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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-fioccola-rfc8321bis-03 == Outdated reference: A later version (-04) exists of draft-fioccola-rfc8889bis-03 == Outdated reference: A later version (-08) exists of draft-ietf-bier-bier-yang-07 == Outdated reference: A later version (-15) exists of draft-ietf-bier-oam-requirements-11 Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BIER Working Group G. Mirsky 3 Internet-Draft Ericsson 4 Intended status: Standards Track L. Zheng 5 Expires: 2 October 2022 Individual Contributor 6 M. Chen 7 G. Fioccola 8 Huawei Technologies 9 31 March 2022 11 Performance Measurement (PM) with Marking Method in Bit Index Explicit 12 Replication (BIER) Layer 13 draft-ietf-bier-pmmm-oam-12 15 Abstract 17 This document describes the applicability of a hybrid performance 18 measurement method for packet loss and packet delay measurements of a 19 multicast service through a Bit Index Explicit Replication domain. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on 2 October 2022. 38 Copyright Notice 40 Copyright (c) 2022 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 45 license-info) in effect on the date of publication of this document. 46 Please review these documents carefully, as they describe your rights 47 and restrictions with respect to this document. Code Components 48 extracted from this document must include Revised BSD License text as 49 described in Section 4.e of the Trust Legal Provisions and are 50 provided without warranty as described in the Revised BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Conventions used in this document . . . . . . . . . . . . . . 3 56 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 57 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 58 3. OAM Field in BIER Header . . . . . . . . . . . . . . . . . . 3 59 4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4 60 4.1. Single-Marking Enabled Measurement . . . . . . . . . . . 5 61 4.2. Double-Marking Enabled Measurement . . . . . . . . . . . 6 62 4.3. Operational Considerations . . . . . . . . . . . . . . . 7 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 68 8.2. Informative References . . . . . . . . . . . . . . . . . 9 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 71 1. Introduction 73 [RFC8279] introduces and explains the Bit Index Explicit Replication 74 (BIER) architecture and how it supports the forwarding of multicast 75 data packets. [RFC8296] specified that in the case of BIER 76 encapsulation in an MPLS network, a BIER-MPLS label, the label that 77 is at the bottom of the label stack, uniquely identifies the 78 multicast flow. [I-D.fioccola-rfc8321bis] and 79 [I-D.fioccola-rfc8889bis] describe a hybrid performance measurement 80 method, according to the classification of measurement methods in 81 [RFC7799]. The method, called Packet Network Performance Monitoring 82 (PNPM), can be used to measure packet loss, latency, and jitter on 83 live traffic complies with requirements R-5 and R-12 listed in 84 [I-D.ietf-bier-oam-requirements]. Because this method is based on 85 marking consecutive batches of packets, the method is often referred 86 to as a marking method. Terms PNPM and "marking method" in this 87 document are used interchangeably. 89 This document defines how the marking method can be used on the BIER 90 layer to measure packet loss and delay metrics of a multicast flow in 91 an MPLS network. 93 2. Conventions used in this document 95 2.1. Terminology 97 This document uses the terms related to the Alternate Marking Method 98 as defined in [I-D.fioccola-rfc8321bis], [I-D.fioccola-rfc8889bis]. 99 This document uses the terms related to the Bit Indexed Explicit 100 Replication as defined in [RFC8296]. 102 2.2. Requirements Language 104 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 105 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 106 "OPTIONAL" in this document are to be interpreted as described in BCP 107 14 [RFC2119] [RFC8174] when, and only when, they appear in all 108 capitals, as shown here. 110 3. OAM Field in BIER Header 112 [RFC8296] defined the two-bits long field, referred to as OAM. The 113 OAM field can be used for the marking performance measurement method. 114 Because the setting of the field to any value does not affect 115 forwarding and/or quality of service treatment of a packet, using the 116 OAM field for PNPM in BIER layer can be viewed as the example of the 117 hybrid performance measurement method. 119 Figure 1 displays the interpretation of the OAM field defined in this 120 specification for the use of the PNPM method. The context of 121 interpretation of the OAM field MAY be signaled via the control plane 122 or configured using an extension to the BIER YANG data model 123 [I-D.ietf-bier-bier-yang]. These extensions are outside the scope of 124 this document. 126 0 127 0 1 128 +-+-+-+-+ 129 | S | D | 130 +-+-+-+-+ 132 Figure 1: OAM field of BIER Header format 134 where: 136 * S - Single-Marking flag; 138 * D - Double-Marking flag. 140 4. Theory of Operation 142 The marking method can be used in the multicast environment supported 143 by BIER layer. Without limiting any generality consider multicast 144 network presented in Figure 2. Any combination of markings can be 145 applied to a multicast flow by the Bit Forwarding Ingress Router 146 (BFIR) at either ingress or egress point to perform node, link, 147 segment or end-to-end measurement to detect performance degradation 148 defect and localize it efficiently. 150 ----- 151 --| D | 152 ----- / ----- 153 --| B |-- 154 / ----- \ ----- 155 / --| E | 156 ----- / ----- 157 | A |--- ----- 158 ----- \ --| F | 159 \ ----- / ----- 160 --| C |-- 161 ----- \ ----- 162 --| G | 163 ----- 165 Figure 2: Multicast network 167 Using the marking method, a BFIR creates distinct sub-flows in the 168 particular multicast traffic over BIER layer. Each sub-flow consists 169 of consecutive blocks of identically marked packets. For example, a 170 block of N packets, with each packet being marked as X, is followed 171 by the block of M packets with each packet being marked as Y. These 172 blocks are unambiguously recognizable by a monitoring point at any 173 Bit Forwarding Router (BFR) and can be measured to calculate packet 174 loss and/or packet delay metrics. The marking method can be used on 175 multiple flows concurently. Demultiplexing of monitored flows might 176 be achived using n-tuple, for example, two-tuple as combination of 177 the values in the Entropy and BFIR-id fields [RFC8296]. Also, that 178 can be achieved by using an explicit Flow Identifiier. The 179 definition of the Flow Identifier is outside the scope of this 180 specification. It is expected that the marking values be set and 181 cleared at the edge of BIER domain. Thus for the scenario presented 182 in Figure 2 if the operator initially monitors the A-C-G and A-B-D 183 segments he may enable measurements on segments C-F and B-E at any 184 time. 186 4.1. Single-Marking Enabled Measurement 188 As explained in [I-D.fioccola-rfc8321bis], marking can be applied to 189 delineate blocks of packets based either on the equal number of 190 packets in a block or based on the equal time interval. The latter 191 method offers better control as it allows a better account for 192 capabilities of downstream nodes to report statistics related to 193 batches of packets and, at the same time, time resolution that 194 affects defect detection interval. 196 If the Single-Marking measurement is used to measure packet loss, 197 then the D flag MUST be set to zero on transmit and ignored by the 198 monitoring point. 200 The S flag is used to create sub-flows to measure the packet loss by 201 switching the value of the S flag every N-th packet or at certain 202 time intervals. Delay metrics MAY be calculated with the sub-flow 203 using any of the following methods: 205 * First/Last Packet Delay calculation: whenever the marking, i.e., 206 the value of S flag changes, a BFR can store the timestamp of the 207 first/last packet of the block. The timestamp can be compared 208 with the timestamp of the packet that arrived in the same order 209 through a monitoring point at a downstream BFR to compute packet 210 delay. Because timestamps collected based on the order of arrival 211 this method is sensitive to packet loss and re-ordering of packets 212 (see Section 4.3 for more details). 214 * Average Packet Delay calculation: an average delay is calculated 215 by considering the average arrival time of the packets within a 216 single block. A BFR may collect timestamps for each packet 217 received within a single block. Average of the timestamp is the 218 sum of all the timestamps divided by the total number of packets 219 received. Then the difference between the average packet arrival 220 time calculated for the downstream monitoring point and the same 221 metric but calculated at the upstream monitoring point is the 222 average packet delay on the segment between these two points. 223 This method is robust to out of order packets and also to packet 224 loss on the segment between the measurement points (packet loss 225 may cause a minor loss of accuracy in the calculated metric 226 because the number of packets used is different at each 227 measurement point). This method only provides a single metric for 228 the duration of the block, and it doesn't give the minimum and 229 maximum delay values. This limitation of producing only the 230 single metric could be overcome by reducing the duration of the 231 block. As a result, the calculated value of the average delay 232 will better reflect the minimum and maximum delay values of the 233 block's duration time. 235 4.2. Double-Marking Enabled Measurement 237 Double-Marking method allows measurement of minimum and maximum 238 delays for the monitored flow, but it requires more nodal and network 239 resources. If the Double-Marking method used, then the S flag is 240 used to create the sub-flow, i.e., mark blocks of packets. The D 241 flag is used to mark single packets within a block to measure delay 242 and jitter. 244 The first marking (S flag alternation) is needed for packet loss and 245 also for average delay measurement. The second marking (D flag is 246 put to one) creates a new set of marked packets that are fully 247 identified over the BIER network, so that a BFR can store the 248 timestamps of these packets; these timestamps can be compared with 249 the timestamps of the same packets on a second BFR to compute packet 250 delay values for each packet. The number of measurements can be 251 easily increased by changing the frequency of the second marking. On 252 the other hand, the higher frequency of the second marking will cause 253 a higher volume of the measurement data being transported through the 254 BIER domain. An operator should consider and balance both effects. 255 This method is useful to measure not only the average delay but also 256 the minimum and maximum delay values and, in wider terms, to know 257 more about the statistic distribution of delay values. 259 4.3. Operational Considerations 261 For the ease of operational procedures, the initial marking of a 262 multicast flow is performed at BFIR. and cleared, by way of removing 263 BIER encapsulation form a payload packet, at the edge of the BIER 264 domain by BFERs. 266 Since at the time of writing this specification, there are no 267 proposals to using auto-discovery or signaling mechanism to inform 268 downstream nodes what methodology is used each monitoring point MUST 269 be configured beforehand. 271 Section 5 [I-D.fioccola-rfc8321bis] provides a detailed analysis of 272 how packet re-ordering and the duration of the block in the Single- 273 Marking mode of the marking method impact the accuracy of the packet 274 loss measurement. Re-ordering of packets in the Single-Marking mode 275 will be noticeable only at the edge of a block of packets (re- 276 ordering within the block cannot be detected in the Single-Marking 277 mode). If the extra delay for some packets is much smaller than half 278 of the duration of a block, then it should be easier to attribute re- 279 ordered packets to the proper block and thus maintain the accuracy of 280 the packet loss measurement. 282 Selection of a time interval to switch the marking of a batch of 283 packets should be based on the service requirements. In the course 284 of the regular operation, reports, including performance metrics like 285 packet loss ratio, packet delay, and inter-packet delay variation, 286 are logged every 15 minutes. Thus, it is reasonable to maintain the 287 duration of the measurement interval at 5 minutes with 100 288 measurements per each interval. To support these measurements, 289 marking of the packet batch is switched every 3 seconds. In case 290 when performance metrics are required in near-real-time, the duration 291 interval of a single batch of identically marked packets will be in 292 the range of tens of milliseconds. 294 5. IANA Considerations 296 This document sets no requirements to IANA. This section can be 297 removed before the publication. 299 6. Security Considerations 301 Regarding using the marking method, [I-D.fioccola-rfc8321bis] 302 stressed two types of security concerns. First, the potential harm 303 caused by the measurements, is a lesser threat as [RFC8296] defines 304 OAM field used by the marking method so that the value of "two bits 305 have no effect on the path taken by a BIER packet and have no effect 306 on the quality of service applied to a BIER packet." Second security 307 concern, potential harm to the measurements can be mitigated by using 308 policy, suggested in [RFC8296], to accept BIER packets only from 309 trusted routers, not from customer-facing interfaces. 311 All the security considerations for BIER discussed in [RFC8296] are 312 inherited by this document. 314 7. Acknowledgement 316 Comments from Alvaro Retana helped improve the document and are much 317 appreciated. 319 Reviews and comments from Quan Xiong and Xiao Min are thankfully 320 acknowledged. 322 8. References 324 8.1. Normative References 326 [I-D.fioccola-rfc8321bis] 327 Fioccola, G., Cociglio, M., Mirsky, G., Mizrahi, T., Zhou, 328 T., and X. Min, "Alternate-Marking Method", Work in 329 Progress, Internet-Draft, draft-fioccola-rfc8321bis-03, 23 330 February 2022, . 333 [I-D.fioccola-rfc8889bis] 334 Fioccola, G., Cociglio, M., Sapio, A., Sisto, R., and T. 335 Zhou, "Multipoint Alternate-Marking Method", Work in 336 Progress, Internet-Draft, draft-fioccola-rfc8889bis-03, 23 337 February 2022, . 340 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 341 Requirement Levels", BCP 14, RFC 2119, 342 DOI 10.17487/RFC2119, March 1997, 343 . 345 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 346 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 347 May 2017, . 349 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 350 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 351 for Bit Index Explicit Replication (BIER) in MPLS and Non- 352 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 353 2018, . 355 8.2. Informative References 357 [I-D.ietf-bier-bier-yang] 358 Chen, R., Hu, F., Zhang, Z., Dai, X., and M. Sivakumar, 359 "YANG Data Model for BIER Protocol", Work in Progress, 360 Internet-Draft, draft-ietf-bier-bier-yang-07, 8 September 361 2020, . 364 [I-D.ietf-bier-oam-requirements] 365 Mirsky, G., Kumar, N., Chen, M., and S. Pallagatti, 366 "Operations, Administration and Maintenance (OAM) 367 Requirements for Bit Index Explicit Replication (BIER) 368 Layer", Work in Progress, Internet-Draft, draft-ietf-bier- 369 oam-requirements-11, 15 November 2020, 370 . 373 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 374 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 375 May 2016, . 377 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 378 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 379 Explicit Replication (BIER)", RFC 8279, 380 DOI 10.17487/RFC8279, November 2017, 381 . 383 Authors' Addresses 385 Greg Mirsky 386 Ericsson 387 Email: gregimirsky@gmail.com 389 Lianshu Zheng 390 Individual Contributor 391 Email: veronique_zheng@hotmail.com 393 Mach Chen 394 Huawei Technologies 395 Email: mach.chen@huawei.com 397 Giuseppe Fioccola 398 Huawei Technologies 399 Email: giuseppe.fioccola@huawei.com