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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 8321 (Obsoleted by RFC 9341) == Outdated reference: A later version (-08) exists of draft-ietf-bier-bier-yang-07 == Outdated reference: A later version (-15) exists of draft-ietf-bier-oam-requirements-11 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--).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 ZTE Corp. 4 Intended status: Standards Track L. Zheng 5 Expires: June 5, 2021 M. Chen 6 G. Fioccola 7 Huawei Technologies 8 December 2, 2020 10 Performance Measurement (PM) with Marking Method in Bit Index Explicit 11 Replication (BIER) Layer 12 draft-ietf-bier-pmmm-oam-09 14 Abstract 16 This document describes the applicability of a hybrid performance 17 measurement method for packet loss and packet delay measurements of a 18 multicast service through a Bit Index Explicit Replication domain. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on June 5, 2021. 37 Copyright Notice 39 Copyright (c) 2020 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Conventions used in this document . . . . . . . . . . . . . . 2 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 . . . . . . . . . . . . . . . 6 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 67 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 68 8.2. Informative References . . . . . . . . . . . . . . . . . 8 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. [RFC8321] describes a hybrid performance measurement 79 method, according to the classification of measurement methods in 80 [RFC7799]. The method, called Packet Network Performance Monitoring 81 (PNPM), can be used to measure packet loss, latency, and jitter on 82 live traffic complies with requirements #5 and #12 listed in 83 [I-D.ietf-bier-oam-requirements]. Because this method is based on 84 marking consecutive batches of packets, the method is often referred 85 to as a marking method. Terms PNPM and "marking method" in this 86 document are used interchangeably. 88 This document defines how the marking method can be used on the BIER 89 layer to measure packet loss and delay metrics of a multicast flow in 90 an MPLS network. 92 2. Conventions used in this document 93 2.1. Terminology 95 BFR: Bit-Forwarding Router 97 BFER: Bit-Forwarding Egress Router 99 BFIR: Bit-Forwarding Ingress Router 101 BIER: Bit Index Explicit Replication 103 OAM: Operations, Administration and Maintenance 105 PNPM: Packet Network Performance Monitoring 107 2.2. Requirements Language 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 111 "OPTIONAL" in this document are to be interpreted as described in BCP 112 14 [RFC2119] [RFC8174] when, and only when, they appear in all 113 capitals, as shown here. 115 3. OAM Field in BIER Header 117 [RFC8296] defined the two-bits long field, referred to as OAM. The 118 OAM field can be used for the marking performance measurement method. 119 Because the setting of the field to any value does not affect 120 forwarding and/or quality of service treatment of a packet, using the 121 OAM field for PNPM in BIER layer can be viewed as the example of the 122 hybrid performance measurement method. 124 Figure 1 displays the interpretation of the OAM field defined in this 125 specification for the use of the PNPM method. The context of 126 interpretation of the OAM field MAY be signaled via the control plane 127 or configured using an extension to the BIER YANG data model 128 [I-D.ietf-bier-bier-yang]. These extensions are outside the scope of 129 this document. 131 0 132 0 1 133 +-+-+-+-+ 134 | S | D | 135 +-+-+-+-+ 137 Figure 1: OAM field of BIER Header format 139 where: 141 o S - Single-Marking flag; 143 o D - Double-Marking flag. 145 4. Theory of Operation 147 The marking method can be used in the multicast environment supported 148 by BIER layer. Without limiting any generality consider multicast 149 network presented in Figure 2. Any combination of markings can be 150 applied to a multicast flow by the Bit Forwarding Ingress Router 151 (BFIR) at either ingress or egress point to perform node, link, 152 segment or end-to-end measurement to detect performance degradation 153 defect and localize it efficiently. 155 ----- 156 --| D | 157 ----- / ----- 158 --| B |-- 159 / ----- \ ----- 160 / --| E | 161 ----- / ----- 162 | A |--- ----- 163 ----- \ --| F | 164 \ ----- / ----- 165 --| C |-- 166 ----- \ ----- 167 --| G | 168 ----- 170 Figure 2: Multicast network 172 Using the marking method, a BFIR creates distinct sub-flows in the 173 particular multicast traffic over BIER layer. Each sub-flow consists 174 of consecutive blocks of identically marked packets. For example, a 175 block of N packets, with each packet being marked as X, is followed 176 by the block of M packets with each packet being marked as Y. These 177 blocks are unambiguously recognizable by a monitoring point at any 178 Bit Forwarding Router (BFR) and can be measured to calculate packet 179 loss and/or packet delay metrics. The marking method can be used on 180 multiple flows concurently. Demultiplexing of monitored flows might 181 be achived using n-tuple, for example, two-tuple as combination of 182 the values in the Entropy and BFIR-id fields [RFC8296]. Also, that 183 can be achieved by using an explicit Flow Identifiier. The 184 definition of the Flow Identifier is outside the scope of this 185 specification. It is expected that the marking values be set and 186 cleared at the edge of BIER domain. Thus for the scenario presented 187 in Figure 2 if the operator initially monitors the A-C-G and A-B-D 188 segments he may enable measurements on segments C-F and B-E at any 189 time. 191 4.1. Single-Marking Enabled Measurement 193 As explained in [RFC8321], marking can be applied to delineate blocks 194 of packets based either on the equal number of packets in a block or 195 based on the equal time interval. The latter method offers better 196 control as it allows a better account for capabilities of downstream 197 nodes to report statistics related to batches of packets and, at the 198 same time, time resolution that affects defect detection interval. 200 If the Single-Marking measurement is used to measure packet loss, 201 then the D flag MUST be set to zero on transmit and ignored by the 202 monitoring point. 204 The S flag is used to create sub-flows to measure the packet loss by 205 switching the value of the S flag every N-th packet or at certain 206 time intervals. Delay metrics MAY be calculated with the sub-flow 207 using any of the following methods: 209 o First/Last Packet Delay calculation: whenever the marking, i.e., 210 the value of S flag changes, a BFR can store the timestamp of the 211 first/last packet of the block. The timestamp can be compared 212 with the timestamp of the packet that arrived in the same order 213 through a monitoring point at a downstream BFR to compute packet 214 delay. Because timestamps collected based on the order of arrival 215 this method is sensitive to packet loss and re-ordering of packets 216 (see Section 4.3 for more details). 218 o Average Packet Delay calculation: an average delay is calculated 219 by considering the average arrival time of the packets within a 220 single block. A BFR may collect timestamps for each packet 221 received within a single block. Average of the timestamp is the 222 sum of all the timestamps divided by the total number of packets 223 received. Then the difference between the average packet arrival 224 time calculated for the downstream monitoring point and the same 225 metric but calculated at the upstream monitoring point is the 226 average packet delay on the segment between these two points. 227 This method is robust to out of order packets and also to packet 228 loss on the segment between the measurement points (packet loss 229 may cause a minor loss of accuracy in the calculated metric 230 because the number of packets used is different at each 231 measurement point). This method only provides a single metric for 232 the duration of the block, and it doesn't give the minimum and 233 maximum delay values. This limitation of producing only the 234 single metric could be overcome by reducing the duration of the 235 block. As a result, the calculated value of the average delay 236 will better reflect the minimum and maximum delay values of the 237 block's duration time. 239 4.2. Double-Marking Enabled Measurement 241 Double-Marking method allows measurement of minimum and maximum 242 delays for the monitored flow, but it requires more nodal and network 243 resources. If the Double-Marking method used, then the S flag is 244 used to create the sub-flow, i.e., mark blocks of packets. The D 245 flag is used to mark single packets within a block to measure delay 246 and jitter. 248 The first marking (S flag alternation) is needed for packet loss and 249 also for average delay measurement. The second marking (D flag is 250 put to one) creates a new set of marked packets that are fully 251 identified over the BIER network, so that a BFR can store the 252 timestamps of these packets; these timestamps can be compared with 253 the timestamps of the same packets on a second BFR to compute packet 254 delay values for each packet. The number of measurements can be 255 easily increased by changing the frequency of the second marking. On 256 the other hand, the higher frequency of the second marking will cause 257 a higher volume of the measurement data being transported through the 258 BIER domain. An operator should consider and balance both effects. 259 This method is useful to measure not only the average delay but also 260 the minimum and maximum delay values and, in wider terms, to know 261 more about the statistic distribution of delay values. 263 4.3. Operational Considerations 265 For the ease of operational procedures, the initial marking of a 266 multicast flow is performed at BFIR. and cleared, by way of removing 267 BIER encapsulation form a payload packet, at the edge of the BIER 268 domain by BFERs. 270 Since at the time of writing this specification, there are no 271 proposals to using auto-discovery or signaling mechanism to inform 272 downstream nodes what methodology is used each monitoring point MUST 273 be configured beforehand. 275 Section 4.3 [RFC8321] provides a detailed analysis of how packet re- 276 ordering and the duration of the block in the Single-Marking mode of 277 the marking method impact the accuracy of the packet loss 278 measurement. Re-ordering of packets in the Single-Marking mode will 279 be noticeable only at the edge of a block of packets (re-ordering 280 within the block cannot be detected in the Single-Marking mode). If 281 the extra delay for some packets is much smaller than half of the 282 duration of a block, then it should be easier to attribute re-ordered 283 packets to the proper block and thus maintain the accuracy of the 284 packet loss measurement. 286 Selection of a time interval to switch the marking of a batch of 287 packets should be based on the service requirements. In the course 288 of the regular operation, reports, including performance metrics like 289 packet loss ratio, packet delay, and inter-packet delay variation, 290 are logged every 15 minutes. Thus, it is reasonable to maintain the 291 duration of the measurement interval at 5 minutes with 100 292 measurements per each interval. To support these measurements, 293 marking of the packet batch is switched every 3 seconds. In case 294 when performance metrics are required in near-real-time, the duration 295 interval of a single batch of identically marked packets will be in 296 the range of tens of milliseconds. 298 5. IANA Considerations 300 This document sets no requirements to IANA. This section can be 301 removed before the publication. 303 6. Security Considerations 305 Regarding using the marking method, [RFC8321] stressed two types of 306 security concerns. First, the potential harm caused by the 307 measurements, is a lesser threat as [RFC8296] defines OAM field used 308 by the marking method so that the value of "two bits have no effect 309 on the path taken by a BIER packet and have no effect on the quality 310 of service applied to a BIER packet." Second security concern, 311 potential harm to the measurements can be mitigated by using policy, 312 suggested in [RFC8296], to accept BIER packets only from trusted 313 routers, not from customer-facing interfaces. 315 All the security considerations for BIER discussed in [RFC8296] are 316 inherited by this document. 318 7. Acknowledgement 320 Comments from Alvaro Retana helped improve the document and are much 321 appreciated. 323 Reviews and comments from Quan Xiong and Xiao Min are thankfully 324 acknowledged. 326 8. References 327 8.1. Normative References 329 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 330 Requirement Levels", BCP 14, RFC 2119, 331 DOI 10.17487/RFC2119, March 1997, 332 . 334 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 335 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 336 May 2017, . 338 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 339 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 340 for Bit Index Explicit Replication (BIER) in MPLS and Non- 341 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 342 2018, . 344 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 345 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 346 "Alternate-Marking Method for Passive and Hybrid 347 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 348 January 2018, . 350 8.2. Informative References 352 [I-D.ietf-bier-bier-yang] 353 Chen, R., hu, f., Zhang, Z., dai.xianxian@zte.com.cn, d., 354 and M. Sivakumar, "YANG Data Model for BIER Protocol", 355 draft-ietf-bier-bier-yang-07 (work in progress), September 356 2020. 358 [I-D.ietf-bier-oam-requirements] 359 Mirsky, G., Nainar, N., Chen, M., and S. Pallagatti, 360 "Operations, Administration and Maintenance (OAM) 361 Requirements for Bit Index Explicit Replication (BIER) 362 Layer", draft-ietf-bier-oam-requirements-11 (work in 363 progress), November 2020. 365 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 366 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 367 May 2016, . 369 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 370 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 371 Explicit Replication (BIER)", RFC 8279, 372 DOI 10.17487/RFC8279, November 2017, 373 . 375 Authors' Addresses 377 Greg Mirsky 378 ZTE Corp. 380 Email: gregimirsky@gmail.com 382 Lianshu Zheng 383 Huawei Technologies 385 Email: vero.zheng@huawei.com 387 Mach Chen 388 Huawei Technologies 390 Email: mach.chen@huawei.com 392 Giuseppe Fioccola 393 Huawei Technologies 395 Email: giuseppe.fioccola@huawei.com