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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 8321 (Obsoleted by RFC 9341) == Outdated reference: A later version (-15) exists of draft-ietf-bier-oam-requirements-07 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: January 2, 2020 M. Chen 6 G. Fioccola 7 Huawei Technologies 8 July 1, 2019 10 Performance Measurement (PM) with Marking Method in Bit Index Explicit 11 Replication (BIER) Layer 12 draft-ietf-bier-pmmm-oam-06 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 January 2, 2020. 36 Copyright Notice 38 Copyright (c) 2019 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 . . . . . . . . . . . 4 60 4.2. Double-Marking Enabled Measurement . . . . . . . . . . . 5 61 4.3. Operational Considerations . . . . . . . . . . . . . . . 6 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 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 2.2. Requirements Language 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 107 "OPTIONAL" in this document are to be interpreted as described in BCP 108 14 [RFC2119] [RFC8174] when, and only when, they appear in all 109 capitals, as shown here. 111 3. OAM Field in BIER Header 113 [RFC8296] defined the two-bits long field, referred to as OAM. The 114 OAM field can be used for the marking performance measurement method. 115 Because the setting of the field to any value does not affect 116 forwarding and/or quality of service treatment of a packet, using the 117 OAM field for PNPM in BIER layer can be viewed as the example of the 118 hybrid performance measurement method. 120 Figure 1 displays the interpretation of the OAM field defined in this 121 specification for the use by PNPM method. 123 0 124 0 1 125 +-+-+-+-+ 126 | S | D | 127 +-+-+-+-+ 129 Figure 1: OAM field of BIER Header format 131 where: 133 o S - Single-Marking flag; 135 o D - Double-Marking flag. 137 4. Theory of Operation 139 The marking method can be used in the multicast environment supported 140 by BIER layer. Without limiting any generality consider multicast 141 network presented in Figure 2. Any combination of markings can be 142 applied to a multicast flow by the Bit Forwarding Ingress Router 143 (BFIR) at either ingress or egress point to perform node, link, 144 segment or end-to-end measurement to detect performance degradation 145 defect and localize it efficiently. 147 ----- 148 --| D | 149 ----- / ----- 150 --| B |-- 151 / ----- \ ----- 152 / --| E | 153 ----- / ----- 154 | A |--- ----- 155 ----- \ --| F | 156 \ ----- / ----- 157 --| C |-- 158 ----- \ ----- 159 --| G | 160 ----- 162 Figure 2: Multicast network 164 Using the marking method, a BFIR creates distinct sub-flows in the 165 particular multicast traffic over BIER layer. Each sub-flow consists 166 of consecutive blocks of identically marked packets. For example, a 167 block of N packets, with each packet being marked as X, is followed 168 by the block of M packets with each packet being marked as Y. These 169 blocks are unambiguously recognizable by a monitoring point at any 170 Bit Forwarding Router (BFR) and can be measured to calculate packet 171 loss and/or packet delay metrics. It is expected that the marking 172 values be set and cleared at the edge of BIER domain. Thus for the 173 scenario presented in Figure 2 if the operator initially monitors the 174 A-C-G and A-B-D segments he may enable measurements on segments C-F 175 and B-E at any time. 177 4.1. Single-Marking Enabled Measurement 179 As explained in [RFC8321], marking can be applied to delineate blocks 180 of packets based either on the equal number of packets in a block or 181 based on the equal time interval. The latter method offers better 182 control as it allows a better account for capabilities of downstream 183 nodes to report statistics related to batches of packets and, at the 184 same time, time resolution that affects defect detection interval. 186 If the Single-Marking measurement is used to measure packet loss, 187 then the D flag MUST be set to zero on transmit and ignored by the 188 monitoring point. 190 The S flag is used to create sub-flows to measure the packet loss by 191 switching the value of the S flag every N-th packet or at certain 192 time intervals. Delay metrics MAY be calculated with the sub-flow 193 using any of the following methods: 195 o First/Last Packet Delay calculation: whenever the marking, i.e., 196 the value of S flag changes, a BFR can store the timestamp of the 197 first/last packet of the block. The timestamp can be compared 198 with the timestamp of the packet that arrived in the same order 199 through a monitoring point at a downstream BFR to compute packet 200 delay. Because timestamps collected based on the order of arrival 201 this method is sensitive to packet loss and re-ordering of packets 202 (see Section 4.3 for more details). 204 o Average Packet Delay calculation: an average delay is calculated 205 by considering the average arrival time of the packets within a 206 single block. A BFR may collect timestamps for each packet 207 received within a single block. Average of the timestamp is the 208 sum of all the timestamps divided by the total number of packets 209 received. Then the difference between the average packet arrival 210 time calculated for the downstream monitoring point and the same 211 metric but calculated at the upstream monitoring point is the 212 average packet delay on the segment between these two points. 213 This method is robust to out of order packets and also to packet 214 loss on the segment between the measurement points (packet loss 215 may cause a minor loss of accuracy in the calculated metric 216 because the number of packets used is different at each 217 measurement point). This method only provides a single metric for 218 the duration of the block, and it doesn't give the minimum and 219 maximum delay values. This limitation of producing only the 220 single metric could be overcome by reducing the duration of the 221 block. As a result, the calculated value of the average delay 222 will better reflect the minimum and maximum delay values of the 223 block's duration time. 225 4.2. Double-Marking Enabled Measurement 227 Double-Marking method allows measurement of minimum and maximum 228 delays for the monitored flow, but it requires more nodal and network 229 resources. If the Double-Marking method used, then the S flag is 230 used to create the sub-flow, i.e., mark blocks of packets. The D 231 flag is used to mark single packets within a block to measure delay 232 and jitter. 234 The first marking (S flag alternation) is needed for packet loss and 235 also for average delay measurement. The second marking (D flag is 236 put to one) creates a new set of marked packets that are fully 237 identified over the BIER network, so that a BFR can store the 238 timestamps of these packets; these timestamps can be compared with 239 the timestamps of the same packets on a second BFR to compute packet 240 delay values for each packet. The number of measurements can be 241 easily increased by changing the frequency of the second marking. On 242 the other hand, the higher frequency of the second marking will cause 243 a higher volume of the measurement data being transported through the 244 BIER domain. An operator should consider and balance both effects. 245 This method is useful to measure not only the average delay but also 246 the minimum and maximum delay values and, in wider terms, to know 247 more about the statistic distribution of delay values. 249 4.3. Operational Considerations 251 For the ease of operational procedures, the initial marking of a 252 multicast flow is performed at BFIR. and cleared, by way of removing 253 BIER encapsulation form a payload packet, at the edge of the BIER 254 domain by BFERs. 256 Since at the time of writing this specification, there are no 257 proposals to using auto-discovery or signaling mechanism to inform 258 downstream nodes what methodology is used each monitoring point MUST 259 be configured beforehand. 261 Section 4.3 [RFC8321] provides a detailed analysis of how packet re- 262 ordering and the duration of the block in the Single-Marking mode of 263 the marking method impact the accuracy of the packet loss 264 measurement. Re-ordering of packets in the Single-Marking mode will 265 be noticeable only at the edge of a block of packets (re-ordering 266 within the block cannot be detected in the Single-Marking mode). If 267 the extra delay for some packets is much smaller than half of the 268 duration of a block, then it should be easier to attribute re-ordered 269 packets to the proper block and thus maintain the accuracy of the 270 packet loss measurement. 272 5. IANA Considerations 274 This document requests IANA to register format of the OAM field of 275 BIER Header as the following: 277 +--------------+---------+-----------------+---------------+ 278 | Bit Position | Marking | Description | Reference | 279 +--------------+---------+-----------------+---------------+ 280 | 0 | S | Single-Marking | This document | 281 | 1 | D | Double-Marking | This document | 282 +--------------+---------+-----------------+---------------+ 284 Table 1: OAM field of BIER Header 286 6. Security Considerations 288 Regarding using the marking method, [RFC8321] stressed two types of 289 security concerns. First, the potential harm caused by the 290 measurements, is a lesser threat as [RFC8296] defines OAM field used 291 by the marking method so that the value of "two bits have no effect 292 on the path taken by a BIER packet and have no effect on the quality 293 of service applied to a BIER packet." Second security concern, 294 potential harm to the measurements can be mitigated by using policy, 295 suggested in [RFC8296], to accept BIER packets only from trusted 296 routers, not from customer-facing interfaces. 298 All the security considerations for BIER discussed in [RFC8296] are 299 inherited by this document. 301 7. Acknowledgement 303 TBD 305 8. References 307 8.1. Normative References 309 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 310 Requirement Levels", BCP 14, RFC 2119, 311 DOI 10.17487/RFC2119, March 1997, 312 . 314 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 315 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 316 May 2017, . 318 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 319 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 320 for Bit Index Explicit Replication (BIER) in MPLS and Non- 321 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 322 2018, . 324 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 325 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 326 "Alternate-Marking Method for Passive and Hybrid 327 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 328 January 2018, . 330 8.2. Informative References 332 [I-D.ietf-bier-oam-requirements] 333 Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N., 334 Aldrin, S., Zheng, L., Chen, M., Akiya, N., and S. 335 Pallagatti, "Operations, Administration and Maintenance 336 (OAM) Requirements for Bit Index Explicit Replication 337 (BIER) Layer", draft-ietf-bier-oam-requirements-07 (work 338 in progress), February 2019. 340 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 341 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 342 May 2016, . 344 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 345 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 346 Explicit Replication (BIER)", RFC 8279, 347 DOI 10.17487/RFC8279, November 2017, 348 . 350 Authors' Addresses 352 Greg Mirsky 353 ZTE Corp. 355 Email: gregimirsky@gmail.com 357 Lianshu Zheng 358 Huawei Technologies 360 Email: vero.zheng@huawei.com 362 Mach Chen 363 Huawei Technologies 365 Email: mach.chen@huawei.com 366 Giuseppe Fioccola 367 Huawei Technologies 369 Email: giuseppe.fioccola@huawei.com