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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC8186' is defined on line 371, but no explicit reference was found in the text Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Li 3 Internet-Draft H. Yang 4 Intended status: Informational T. Sun 5 Expires: January 9, 2022 China Mobile 6 July 8, 2021 8 One-way Delay Measurement Based on Deterministic Networking 9 draft-li-ippm-deterministic-owd-measurement-00 11 Abstract 13 One-way delay is a key indicator to measure network quality. Some 14 applications are one-way transmission in the network, such as some 15 high-definition video services, and are very sensitive to one-way 16 delay. Excessive delay will affect user experience greatly. To some 17 extent, the network can't even be used, so it is very important to 18 accurately measure the network transmission delay. The current one- 19 way delay measurement method has problems such as high complexity and 20 low measurement accuracy. In order to solve the problem of high- 21 precision one-way delay measurement, a one-way delay measurement 22 method based on deterministic networking is proposed in this 23 document. The method takes advantage of the delay characteristics of 24 the deterministic networking and does not depend on precise time 25 synchronization. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on January 9, 2022. 44 Copyright Notice 46 Copyright (c) 2021 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 63 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 64 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 65 3. One-way Delay Measurement Method Based on Deterministic 66 Networking . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 4. Procedures of the One-way Delay Measurement Method . . . . . 6 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 69 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 70 7. Normative References . . . . . . . . . . . . . . . . . . . . 8 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 73 1. Introduction 75 One-way transmission delay is a key indicator to measure network 76 quality. Some applications are based on one-way transmission in the 77 network, such as some high-definition video services, and are very 78 sensitive to one-way delay. Excessive one-way delay will affect user 79 experience dramatically, so it is very important to accurately 80 measure the one-way transmission delay of the network. 82 There are several kinds of methods to measure one-way delay. The 83 first kind of methods is active measurement. A sender will send 84 measurement protocol messages, such as Two-Way Active Measurement 85 Protocol (TWAMP) [RFC8186]messages, to the network to measure the 86 one-way delay of the sender and receiver. The advantage of active 87 measurement is that it is flexible in application. The disadvantage 88 is that the measurement messages cannot measure the delay of real 89 services, and the measurement of one-way delay requires sender and 90 receiver to support time synchronization protocol, such as NTP 91 [RFC5905]and PTP [IEEE.1588.2008]. The first kind of methods is 92 passive measurement. The passive measurement devices will calculate 93 network delay by collecting actual business traffic. The advantage 94 of passive measurement is that it can measure the one-way delay of 95 real services. The disadvantage is that two passive measurement 96 devices need to be deployed, and the two devices require time 97 synchronization, which is difficult to implement. The third kind of 98 methods is hybrid measurement. Hybrid measurement is a combination 99 of active and passive measurements, that is, inserting some fields or 100 flags in the service message to realize the delay measurement of the 101 actual service. The disadvantage is that the message format of the 102 actual service is changed, which will affect the forwarding behavior 103 of the service and have observer effect. The network element needs 104 to be able to recognize and forward the modified service message, and 105 time synchronization of the network element is also required. 107 The above-mentioned one-way delay measurement methods have the 108 following shortcomings. Firstly, if the measurement message is 109 injected into actual network, it will occupy network bandwidth 110 resources and interfere with the actual service flow, so the measured 111 delay is not the delay of the actual service. Secondly, the 112 measurement equipment or network elements need to support time 113 synchronization protocols, which is difficult to implement and 114 costly. 116 To address the following shortcomings of existing methods, this 117 document presents the following technical solution. A high-precision 118 one-way delay measurement method is proposed, which can be used to 119 measure the one-way delay of actual service packets, without sending 120 measurement messages, without changing the actual network status, 121 without changing service messages, and without the need for network 122 elements to support time synchronization protocols. 124 2. Conventions Used in This Document 126 2.1. Terminology 128 NTP Network Time Protocol 130 PTP Precision Time Protocol 132 TWAMP Two-Way Active Measurement Protocol 134 SLA Service Level Agreement 136 2.2. Requirements Language 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 140 "OPTIONAL" in this document are to be interpreted as described in BCP 141 14[RFC2119][RFC8174] when, and only when, they appear in all 142 capitals, as shown here. 144 3. One-way Delay Measurement Method Based on Deterministic Networking 146 +-----------------------------------------------------------+ 147 | Centralized Control Node | 148 +----+-------------+---------------+---------+---------+----+ 149 ^ ^ ^ ^ ^ 150 | | T4 | T3 | | Tn 151 | | | +----+----+ | 152 | | | | Network | | 153 T1 | T2 | +----------------->Element 3+-+ | 154 | | | | | | | | 155 | | | | +---------+ | | 156 | | | | | | 157 | | | | | | 158 | | | | | | 159 | | | | | | 160 +----+----+ +----+--+-+ +----+----+ +-v--+----+ 161 | Network | | Network | | Network | | Network | 162 |Element 1+--->Element 2+----->Element 4+--------->Element n| 163 | | | | | | | | 164 +---------+ +---------+ +---------+ +---------+ 166 Figure 1: A schematic diagram of the network topology structure 168 A schematic diagram of the network topology structure to describe the 169 proposed method is shown in Figure 1. The network may be a SDN 170 (Software Defined Network) or a traditional network. Whether it is 171 SDN or traditional network, there is a centralized control node (or 172 called a centralized management unit) for collecting network 173 information sent by network elements and sending control information 174 to the network. Taking SDN as an example, the centralized control 175 node can be a SDN controller. For traditional networks, the 176 centralized control node can be a network management system. The 177 information from the network element to the centralized control node 178 generally passes through the management network. In our solution, 179 the management network from each network element to the centralized 180 control node is required to use a delay deterministic network. As an 181 example, the delay deterministic network may be a time sensitive 182 network (TSN) or a deterministic Internet (Deterministic Internet 183 Network, DIP) [RFC8655], etc. Through the delay deterministic 184 network, the transmission delay of the network element information 185 from the network element to the centralized control node can be 186 guaranteed to be fixed. T1~Tn in Figure 1 represent the network 187 element information delay from the network element to the centralized 188 control node of network element 1 to n respectively. 190 As shown in Figure 1, suppose network traffic of a real service flow 191 passes through network element 1, network element 2, ..., network 192 element n in turn, and the time when network traffic passes through 193 the network element is recorded as t1, t2, ..., tn. The timestamp 194 maybe the ingress timestamp of network traffic entering the network 195 element or the egress timestamp of network traffic flowing out of the 196 network element after the forwarding is completed. Each network 197 element transmits the flow information to the centralized control 198 node through the delay deterministic network when real traffic 199 passes, and the transmission delays of each network element to 200 transmit the flow information to the centralized control node through 201 the delay deterministic network are denoted as T1, T2, ..., Tn, 202 respectively. The timestamps when the centralized control node 203 receives the flow information of each network element are t1', t2', 204 ..., tn'. 206 Taking the calculation of the one-way transmission delay of traffic 207 from network element 1 to network element 2 as an example, the one- 208 way transmission delay can be calculated in the following way. 209 Firstly, because the clocks of network element 1 and network element 210 2 are not synchronized, suppose the time deviation between the two is 211 delta_t. Then the one-way transmission delay of traffic from network 212 element 1 to network element 2 satisfies the following formula (1). 213 Among them, Delay represents the one-way transmission delay of 214 traffic from network element 1 to network element 2. 216 Formula (1): Delay = t2 - t1 - delta_t 218 Secondly, because the clocks between network element 1 and the 219 centralized control node are not synchronized, assuming that the time 220 deviation between the two is delta_t', the time for the traffic 221 information collected from the network element 1 to reach the 222 centralized control node through the delay deterministic network 223 satisfies the following formula (2). 225 Formula (2): t1' = t1 + T1 + delta_t' 227 Thirdly, the clocks between network element 2 and the centralized 228 control node are not synchronized, and the time deviation between 229 network element 2 and the centralized control node is delta_t'- 230 delta_t. The time t2' for the collected traffic to reach the 231 centralized control node satisfies the following formula (3). 233 Formula (3): t2' = t2 + T2 + delta_t' - delta_t 235 Forthly, subtracting the formula (2) from the above formula (3), we 236 can obtain the following formula (4). 238 Formula (4): t2 - t1 - delta_t = t2' - t1' + T1 - T2 239 Fifthly, substituting the above formula (4) into the above formula 240 (1), the following formula (5) can be obtained. 242 Formula (5): Delay = t2' - t1' + T1 - T2 244 So far, the one-way transmission delay of traffic from network 245 element 1 to network element 2 is obtained. Taking the calculation 246 of one-way transmission delay of traffic from network element 1 to 247 network element 3 as an example, the one-way transmission delay can 248 be calculated in the following way: I) Referring to the above formula 249 (5), the one-way transmission delay of traffic from network element 1 250 to network element 2 is: Delay12 = t2' - t1' + T1 - T2. II) 251 Referring to the above formula (5), the one-way transmission delay of 252 traffic from network element 2 to network element 3 is: Delay23 = t3' 253 - t2' + T2 - T3. III) The one-way transmission delay of traffic from 254 network element 1 to network element 3 is: Delay13 = Delay12 + 255 Delay23 = t2' - t1' + T1 - T2 + t3' -t2' +T2 - T3 = t3' - t1' + T1 - 256 T3. It can be seen that the one-way transmission delay between any 257 two network elements can be calculated similarly to the above formula 258 (5). For example, taking network element m and network element n as 259 an example, the transmission delay of traffic from network element m 260 to network element n is: Delay = tn' - tm' + Tm - Tn, where tn' and 261 tm' are the time when the traffic information of network element m 262 and network n reaches the centralized control node, and Tm and Tn are 263 transmission delay of the traffic information from network element m 264 and network element n to the centralized control node respectively 265 through delay deterministic network. 267 4. Procedures of the One-way Delay Measurement Method 269 In this section, the procedures of the proposed one-way delay 270 measurement method will be elaborated. Assume there are two network 271 element. It is determined that the time when the centralized control 272 node receives the first flow information is the first time, and the 273 time when the second flow information is received by the centralized 274 control node is determined to be the second time. The first flow 275 information is sent to the centralized control node via delay 276 deterministic network, and the second flow information is also sent 277 to the centralized control node via delay deterministic network. The 278 procedures of the one-way delay measurement method is shown in 279 Figure 2. 281 +-----------+ +-----------+ +---------------------+ +--------------+ 282 | Network | | Network | | Delay Deterministic | | Centralized | 283 | Element m | | Element n | | Network | | Control Node | 284 +-----+-----+ +-----+-----+ +---------------------+ +-------+------+ 285 | | | 286 | | | 287 | | | 288 | | The first transmission +-------+--------+ 289 | | delay is Tm | tm' represents | 290 +----------------------------------------------> the first time | 291 | | +-------+--------+ 292 | | | 293 | | | 294 | | The second transmission +-------+--------+ 295 | | delay is Tn | tn' represents | 296 | +-------------------------------> the second time| 297 | | +-------+--------+ 298 | | | 299 | | | 300 | | | 301 + + + 303 Figure 2: Procedures of the one-way delay measurement method 305 The transmission delay of traffic from the first network element to 306 the second network element can be determined based on the first time, 307 the second time, the first transmission delay, and the second 308 transmission delay. 310 The first traffic information is sent by the first network element to 311 the centralized control node via a delay deterministic network at the 312 moment when the traffic passes through the first network element. 313 And the time when the traffic passes through the first network 314 element refers to the moment when traffic enters the first network 315 element or the time when traffic flows out of the first network 316 element. 318 The second traffic information is sent by the second network element 319 to the centralized control node via a delay deterministic network at 320 the moment when the traffic passes through the second network 321 element. And the time when the traffic passes through the second 322 network element refers to the moment when traffic enters the second 323 network element or the time when traffic flows out of the second 324 network element. 326 It is determined that the transmission delay of the first traffic 327 information from the first network element to the centralized control 328 node is the first transmission delay, and it is determined that the 329 transmission delay of the second traffic information from the second 330 network element to the centralized control node is the second 331 transmission delay. The transmission delay of traffic from the first 332 network element to the second network element can be determined based 333 on the following formula: Delay=tn'-tm'+Tm-Tn. Wherein, tn' 334 represents the second time, tm' represents the first time, Tm 335 represents the first transmission delay, Tn represents the second 336 transmission delay, and Delay represents transmission delay of the 337 traffic from the first network element to the second network element. 338 In the above method, the delay deterministic network is used to 339 ensure that the first transmission delay and the second transmission 340 delay are fixed delays. 342 5. Security Considerations 344 TBD. 346 6. IANA Considerations 348 TBD. 350 7. Normative References 352 [IEEE.1588.2008] 353 IEEE, "IEEE Standard for a Precision Clock Synchronization 354 Protocol for Networked Measurement and Control Systems", 355 July 2008. 357 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 358 Requirement Levels", BCP 14, RFC 2119, 359 DOI 10.17487/RFC2119, March 1997, 360 . 362 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 363 "Network Time Protocol Version 4: Protocol and Algorithms 364 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 365 . 367 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 368 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 369 May 2017, . 371 [RFC8186] Mirsky, G. and I. Meilik, "Support of the IEEE 1588 372 Timestamp Format in a Two-Way Active Measurement Protocol 373 (TWAMP)", RFC 8186, DOI 10.17487/RFC8186, June 2017, 374 . 376 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, 377 "Deterministic Networking Architecture", RFC 8655, 378 DOI 10.17487/RFC8655, October 2019, 379 . 381 Authors' Addresses 383 Yang Li 384 China Mobile 385 Beijing 100053 386 China 388 Email: liyangzn@chinamobile.com 390 Hongwei Yang 391 China Mobile 392 Beijing 100053 393 China 395 Email: yanghongwei@chinamobile.com 397 Tao Sun 398 China Mobile 399 Beijing 100053 400 China 402 Email: suntao@chinamobile.com