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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references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Experimental RFC: RFC 8321 == Outdated reference: A later version (-07) exists of draft-ietf-bier-bier-yang-05 == Outdated reference: A later version (-11) exists of draft-ietf-bier-oam-requirements-08 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--).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: July 6, 2020 M. Chen 6 G. Fioccola 7 Huawei Technologies 8 January 3, 2020 10 Performance Measurement (PM) with Marking Method in Bit Index Explicit 11 Replication (BIER) Layer 12 draft-ietf-bier-pmmm-oam-07 14 Abstract 16 This document describes a hybrid performance measurement method for 17 multicast service through a Bit Index Explicit Replication domain. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on July 6, 2020. 36 Copyright Notice 38 Copyright (c) 2020 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions used in this document . . . . . . . . . . . . . . 2 55 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 56 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 57 3. OAM Field in BIER Header . . . . . . . . . . . . . . . . . . 3 58 4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4 59 4.1. Single-Marking Enabled Measurement . . . . . . . . . . . 5 60 4.2. Double-Marking Enabled Measurement . . . . . . . . . . . 6 61 4.3. Operational Considerations . . . . . . . . . . . . . . . 6 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 63 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 64 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 65 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 67 8.2. Informative References . . . . . . . . . . . . . . . . . 8 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 70 1. Introduction 72 [RFC8279] introduces and explains the Bit Index Explicit Replication 73 (BIER) architecture and how it supports the forwarding of multicast 74 data packets. [RFC8296] specified that in the case of BIER 75 encapsulation in an MPLS network, a BIER-MPLS label, the label that 76 is at the bottom of the label stack, uniquely identifies the 77 multicast flow. [RFC8321] describes a hybrid performance measurement 78 method, per RFC7799's classification of measurement methods 79 [RFC7799]. The method, called Packet Network Performance Monitoring 80 (PNPM), can be used to measure packet loss, latency, and jitter on 81 live traffic complies with requirements #5 and #12 listed in 82 [I-D.ietf-bier-oam-requirements]. Because this method is based on 83 marking consecutive batches of packets, the method is often referred 84 to as a marking method. 86 This document defines how the marking method can be used on the BIER 87 layer to measure packet loss and delay metrics of a multicast flow in 88 an MPLS network. 90 2. Conventions used in this document 91 2.1. Terminology 93 BFR: Bit-Forwarding Router 95 BFER: Bit-Forwarding Egress Router 97 BFIR: Bit-Forwarding Ingress Router 99 BIER: Bit Index Explicit Replication 101 OAM: Operations, Administration and Maintenance 103 PNPM: Packet Network Performance Monitoring 105 2.2. Requirements Language 107 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 108 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 109 "OPTIONAL" in this document are to be interpreted as described in BCP 110 14 [RFC2119] [RFC8174] when, and only when, they appear in all 111 capitals, as shown here. 113 3. OAM Field in BIER Header 115 [RFC8296] defined the two-bits long field, referred to as OAM. The 116 OAM field can be used for the marking performance measurement method. 117 Because the setting of the field to any value does not affect 118 forwarding and/or quality of service treatment of a packet, using the 119 OAM field for PNPM in BIER layer can be viewed as the example of the 120 hybrid performance measurement method. 122 Figure 1 displays the interpretation of the OAM field defined in this 123 specification for the use of the PNPM method. The context of 124 interpretation of the OAM field MAY be signaled via the control plane 125 or configured using an extension to the BIER YANG data model 126 [I-D.ietf-bier-bier-yang]. These extensions are outside the scope of 127 this document. 129 0 130 0 1 131 +-+-+-+-+ 132 | S | D | 133 +-+-+-+-+ 135 Figure 1: OAM field of BIER Header format 137 where: 139 o S - Single-Marking flag; 141 o D - Double-Marking flag. 143 4. Theory of Operation 145 The marking method can be used in the multicast environment supported 146 by BIER layer. Without limiting any generality consider multicast 147 network presented in Figure 2. Any combination of markings can be 148 applied to a multicast flow by the Bit Forwarding Ingress Router 149 (BFIR) at either ingress or egress point to perform node, link, 150 segment or end-to-end measurement to detect performance degradation 151 defect and localize it efficiently. 153 ----- 154 --| D | 155 ----- / ----- 156 --| B |-- 157 / ----- \ ----- 158 / --| E | 159 ----- / ----- 160 | A |--- ----- 161 ----- \ --| F | 162 \ ----- / ----- 163 --| C |-- 164 ----- \ ----- 165 --| G | 166 ----- 168 Figure 2: Multicast network 170 Using the marking method, a BFIR creates distinct sub-flows in the 171 particular multicast traffic over BIER layer. Each sub-flow consists 172 of consecutive blocks of identically marked packets. For example, a 173 block of N packets, with each packet being marked as X, is followed 174 by the block of M packets with each packet being marked as Y. These 175 blocks are unambiguously recognizable by a monitoring point at any 176 Bit Forwarding Router (BFR) and can be measured to calculate packet 177 loss and/or packet delay metrics. It is expected that the marking 178 values be set and cleared at the edge of BIER domain. Thus for the 179 scenario presented in Figure 2 if the operator initially monitors the 180 A-C-G and A-B-D segments he may enable measurements on segments C-F 181 and B-E at any time. 183 4.1. Single-Marking Enabled Measurement 185 As explained in [RFC8321], marking can be applied to delineate blocks 186 of packets based either on the equal number of packets in a block or 187 based on the equal time interval. The latter method offers better 188 control as it allows a better account for capabilities of downstream 189 nodes to report statistics related to batches of packets and, at the 190 same time, time resolution that affects defect detection interval. 192 If the Single-Marking measurement is used to measure packet loss, 193 then the D flag MUST be set to zero on transmit and ignored by the 194 monitoring point. 196 The S flag is used to create sub-flows to measure the packet loss by 197 switching the value of the S flag every N-th packet or at certain 198 time intervals. Delay metrics MAY be calculated with the sub-flow 199 using any of the following methods: 201 o First/Last Packet Delay calculation: whenever the marking, i.e., 202 the value of S flag changes, a BFR can store the timestamp of the 203 first/last packet of the block. The timestamp can be compared 204 with the timestamp of the packet that arrived in the same order 205 through a monitoring point at a downstream BFR to compute packet 206 delay. Because timestamps collected based on the order of arrival 207 this method is sensitive to packet loss and re-ordering of packets 208 (see Section 4.3 for more details). 210 o Average Packet Delay calculation: an average delay is calculated 211 by considering the average arrival time of the packets within a 212 single block. A BFR may collect timestamps for each packet 213 received within a single block. Average of the timestamp is the 214 sum of all the timestamps divided by the total number of packets 215 received. Then the difference between the average packet arrival 216 time calculated for the downstream monitoring point and the same 217 metric but calculated at the upstream monitoring point is the 218 average packet delay on the segment between these two points. 219 This method is robust to out of order packets and also to packet 220 loss on the segment between the measurement points (packet loss 221 may cause a minor loss of accuracy in the calculated metric 222 because the number of packets used is different at each 223 measurement point). This method only provides a single metric for 224 the duration of the block, and it doesn't give the minimum and 225 maximum delay values. This limitation of producing only the 226 single metric could be overcome by reducing the duration of the 227 block. As a result, the calculated value of the average delay 228 will better reflect the minimum and maximum delay values of the 229 block's duration time. 231 4.2. Double-Marking Enabled Measurement 233 Double-Marking method allows measurement of minimum and maximum 234 delays for the monitored flow, but it requires more nodal and network 235 resources. If the Double-Marking method used, then the S flag is 236 used to create the sub-flow, i.e., mark blocks of packets. The D 237 flag is used to mark single packets within a block to measure delay 238 and jitter. 240 The first marking (S flag alternation) is needed for packet loss and 241 also for average delay measurement. The second marking (D flag is 242 put to one) creates a new set of marked packets that are fully 243 identified over the BIER network, so that a BFR can store the 244 timestamps of these packets; these timestamps can be compared with 245 the timestamps of the same packets on a second BFR to compute packet 246 delay values for each packet. The number of measurements can be 247 easily increased by changing the frequency of the second marking. On 248 the other hand, the higher frequency of the second marking will cause 249 a higher volume of the measurement data being transported through the 250 BIER domain. An operator should consider and balance both effects. 251 This method is useful to measure not only the average delay but also 252 the minimum and maximum delay values and, in wider terms, to know 253 more about the statistic distribution of delay values. 255 4.3. Operational Considerations 257 For the ease of operational procedures, the initial marking of a 258 multicast flow is performed at BFIR. and cleared, by way of removing 259 BIER encapsulation form a payload packet, at the edge of the BIER 260 domain by BFERs. 262 Since at the time of writing this specification, there are no 263 proposals to using auto-discovery or signaling mechanism to inform 264 downstream nodes what methodology is used each monitoring point MUST 265 be configured beforehand. 267 Section 4.3 [RFC8321] provides a detailed analysis of how packet re- 268 ordering and the duration of the block in the Single-Marking mode of 269 the marking method impact the accuracy of the packet loss 270 measurement. Re-ordering of packets in the Single-Marking mode will 271 be noticeable only at the edge of a block of packets (re-ordering 272 within the block cannot be detected in the Single-Marking mode). If 273 the extra delay for some packets is much smaller than half of the 274 duration of a block, then it should be easier to attribute re-ordered 275 packets to the proper block and thus maintain the accuracy of the 276 packet loss measurement. 278 Selection of a time interval to switch the marking of a batch of 279 packets should be based on the service requirements. In the course 280 of the regular operation, reports, including performance metrics like 281 packet loss ratio, packet delay, and inter-packet delay variation, 282 are logged every 15 minutes. Thus, it is reasonable to maintain the 283 duration of the measurement interval at 5 minutes with 100 284 measurements per each interval. To support these measurements, 285 marking of the packet batch is switched every 3 seconds. In case 286 when performance metrics are required in near-real-time, the duration 287 interval of a single batch of identically marked packets will be in 288 the range of tens of milliseconds. 290 5. IANA Considerations 292 This document sets no requirements to IANA. This section can be 293 removed before the publication. 295 6. Security Considerations 297 Regarding using the marking method, [RFC8321] stressed two types of 298 security concerns. First, the potential harm caused by the 299 measurements, is a lesser threat as [RFC8296] defines OAM field used 300 by the marking method so that the value of "two bits have no effect 301 on the path taken by a BIER packet and have no effect on the quality 302 of service applied to a BIER packet." Second security concern, 303 potential harm to the measurements can be mitigated by using policy, 304 suggested in [RFC8296], to accept BIER packets only from trusted 305 routers, not from customer-facing interfaces. 307 All the security considerations for BIER discussed in [RFC8296] are 308 inherited by this document. 310 7. Acknowledgement 312 TBD 314 8. References 316 8.1. Normative References 318 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 319 Requirement Levels", BCP 14, RFC 2119, 320 DOI 10.17487/RFC2119, March 1997, 321 . 323 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 324 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 325 May 2017, . 327 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 328 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 329 for Bit Index Explicit Replication (BIER) in MPLS and Non- 330 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 331 2018, . 333 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 334 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 335 "Alternate-Marking Method for Passive and Hybrid 336 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 337 January 2018, . 339 8.2. Informative References 341 [I-D.ietf-bier-bier-yang] 342 Chen, R., hu, f., Zhang, Z., dai.xianxian@zte.com.cn, d., 343 and M. Sivakumar, "YANG Data Model for BIER Protocol", 344 draft-ietf-bier-bier-yang-05 (work in progress), May 2019. 346 [I-D.ietf-bier-oam-requirements] 347 Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N., 348 Aldrin, S., Zheng, L., Chen, M., Akiya, N., and S. 349 Pallagatti, "Operations, Administration and Maintenance 350 (OAM) Requirements for Bit Index Explicit Replication 351 (BIER) Layer", draft-ietf-bier-oam-requirements-08 (work 352 in progress), August 2019. 354 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 355 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 356 May 2016, . 358 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 359 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 360 Explicit Replication (BIER)", RFC 8279, 361 DOI 10.17487/RFC8279, November 2017, 362 . 364 Authors' Addresses 366 Greg Mirsky 367 ZTE Corp. 369 Email: gregimirsky@gmail.com 370 Lianshu Zheng 371 Huawei Technologies 373 Email: vero.zheng@huawei.com 375 Mach Chen 376 Huawei Technologies 378 Email: mach.chen@huawei.com 380 Giuseppe Fioccola 381 Huawei Technologies 383 Email: giuseppe.fioccola@huawei.com