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Xiong 3 Internet-Draft ZTE Corporation 4 Intended status: Standards Track October 2021 5 Expires: 27 April 2022 7 The Requirements for Wide-area IP Deterministic Networking 8 draft-xiong-detnet-wide-area-ip-requirements-00 10 Abstract 12 In wide-area IP networks, more requirements need to be taken into 13 considerations such as differentiated DetNet QoS of multiple 14 services, high-efficiency of resources utilization and routes 15 steering, integration of large-scale heterogeneous network and 16 guarantees of multiple dynamic deterministic flows. This document 17 describes the requirements in wide-area applications and proposes the 18 solution with deterministic resources, routes and QoS. 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 4 April 2022. 37 Copyright Notice 39 Copyright (c) 2021 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 (https://trustee.ietf.org/ 44 license-info) in effect on the date of publication of this document. 45 Please review these documents carefully, as they describe your rights 46 and restrictions with respect to this document. Code Components 47 extracted from this document must include Simplified BSD License text 48 as described in Section 4.e of the Trust Legal Provisions and are 49 provided without warranty as described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions used in this document . . . . . . . . . . . . . . 4 55 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 56 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 57 3. Requirements for Wide-area IP Deterministic Networking . . . 4 58 3.1. Differentiated DetNet QoS of Multiple Services . . . . . 4 59 3.2. Integration of Large-scale Heterogeneous Network . . . . 5 60 3.3. Efficiency of Resources Utilization and Routes 61 Steering . . . . . . . . . . . . . . . . . . . . . . . . 6 62 3.4. Guarantees of Multiple Dynamic Deterministic Flows . . . 6 63 4. Solutions Considerations of Wide-area IP Deterministic 64 Networking . . . . . . . . . . . . . . . . . . . . . . . 7 65 4.1. The Deterministic Resources . . . . . . . . . . . . . . . 7 66 4.2. The Deterministic Routes . . . . . . . . . . . . . . . . 7 67 4.3. The Deterministic QoS . . . . . . . . . . . . . . . . . . 8 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 69 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 70 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 71 8. Normative References . . . . . . . . . . . . . . . . . . . . 8 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 74 1. Introduction 76 5G network is oriented to the internet of everything. In addition to 77 the Enhanced Mobile Broadband (eMBB) and Massive Machine Type 78 Communications(mMTC) services, it also supports the Ultra-reliable 79 Low Latency Communications (uRLLC) services. The uRLLC services 80 cover the industries such as intelligent electrical network, 81 intelligent factory, internet of vehicles, industry automation and 82 other industrial internet scenarios, which is the key demand of 83 digital transformation of vertical domains. These uRLLC services 84 demand SLA guarantees such as low latency and high reliability and 85 other deterministic and precise properties. 87 For the intelligent electrical network, there are deterministic 88 requirements for communication delay, jitter and packet loss rate. 89 For example, in the electrical current difference model, a delay of 90 3~10ms and a jitter variation is no more than 100us are required. 91 The isolation requirement is also important. For example, the 92 automatic operation, control of a process, isochronous data and low 93 priority service need to meet the requirements of hard isolation. In 94 addition to the requirements of delay and jitter, the differential 95 protection (DP) service needs to be isolated from other services. 97 The industrial internet is the key infrastructure that coordinate 98 various units of work over various system components, e.g. people, 99 machines and things in the industrial environment including big data, 100 cloud computing, Internet of Things (IOT), Augment Reality (AR), 101 industrial robots, Artificial Intelligence (AI) and other basic 102 technologies. For example, automation control is one of the basic 103 application and the the core is closed-loop control system. The 104 control process cycle is as low as millisecond level, so the system 105 communication delay needs to reach millisecond level or even lower to 106 ensure the realization of precise control. There are three levels of 107 real-time requirements for industrial interconnection: factory level 108 is about 1s, and process level is 10~100ms, and the highest real-time 109 requirement is motion control, which requires less than 1ms. 111 The applications in 5G networks demand much more deterministic and 112 precise properties. But traditional Ethernet, IP and MPLS networks 113 which is based on statistical multiplexing provides best-effort 114 packet service and offers no delivery and SLA guarantee. The 115 deterministic forwarding can only apply to flows with such well- 116 defined characteristics as periodicity and burstiness. Technologies 117 to provide deterministic service has been proposed to provide bounded 118 latency and jitter based on a best-effort packet network. IEEE 802.1 119 Time-Sensitive Networking (TSN) has been proposed to provide bounded 120 latency and jitter in L2 LAN networks. According to [RFC8655], 121 Deterministic Networking (DetNet) operates at the IP layer and 122 delivers service which provides extremely low data loss rates and 123 bounded latency within a network domain. 125 The deterministic networks not only need to offer the Service Level 126 Agreements (SLA) guarantees such as low latency and jitter, low 127 packet loss and high reliability, but also need to support the 128 precise services such as flexible resource allocation and service 129 isolation. However, under the existing IP network architecture with 130 statistical multiplexing characteristics, the existing deterministic 131 technologies are facing large scale number of nodes and long-distance 132 transmission, traffic scheduling, dynamic flows, and other 133 controversial issues especially in Wide Area Network (WAN) 134 applications. 136 In wide-area IP networks, more requirements need to be taken into 137 considerations such as differentiated DetNet QoS of multiple 138 services, high-efficiency of resources utilization and routes 139 steering, integration of large-scale heterogeneous network and 140 guarantees of multiple dynamic deterministic flows. This document 141 describes the requirements in wide-area applications and proposes the 142 solution with deterministic resources, routes and QoS. 144 2. Conventions used in this document 146 2.1. Terminology 148 The terminology is defined as [RFC8655]. 150 2.2. Requirements Language 152 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 153 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 154 "OPTIONAL" in this document are to be interpreted as described in BCP 155 14 [RFC2119] [RFC8174] when, and only when, they appear in all 156 capitals, as shown here. 158 3. Requirements for Wide-area IP Deterministic Networking 160 3.1. Differentiated DetNet QoS of Multiple Services 162 As defined in [RFC8655], the DetNet QoS can be expressed in terms of 163 : Minimum and maximum end-to-end latency, bounded jitter (packet 164 delay variation), packet loss ratio and an upper bound on out-of- 165 order packet delivery. As described in [RFC8578], DetNet 166 applications differ in their network topologies and specific desired 167 behavior and different services requires differentiated DetNet QoS. 168 In the WAN scenarios, multiple services with differentiated DetNet 169 QoS is co-existed in the same DetNet network. The classification of 170 the deterministic flows is should be taken into considerations. It 171 is required to provide Latency, bounded jitter and packet loss 172 dynamically and flexibly in all scenarios for each characterizd flow. 174 As the Figure 1 shown, the services is divided into 4 levels and 175 level 1~3 is the DetNet flows and level-4 is non-DetNet flow. DetNet 176 applications and DetNet QoS is differentiated within each level. 178 +--------------+---------------+------------+-----------+-----------+ 179 | Item | Level-1 | Level-2 | Level-3 | Level-4 | 180 +--------------+---------------+------------+-----------+-----------+ 181 | Applications | Industrial | VR/AR | Audio and | Broadcast | 182 | Examples | | | Video | | 183 +--------------+---------------+------------+-----------+-----------+ 184 | DetNet QoS | Ultra-low | Low | Low | Best | 185 | | latency and | latency | latency | Effort | 186 | | jitter | and jitter | | | 187 +--------------+---------------+------------+-----------+-----------+ 189 Figure 1: Figure 1: The classification of multiple services 191 Moreover, different DetNet services is required to tolerate different 192 percentage of packet loss ratio such as 99.9%, 99.99%, 99.999%, and 193 so on. It is also required to provide service isolation. In some 194 scenarios, such as intelligent electrical network, the isolation 195 requirements are very important. For example, the automatic 196 operation or control of a process or isochronous data and service 197 with different priorities need to meet the requirements of hard 198 isolation. In addition to the requirements of delay and jitter, the 199 differential protection (DP) service needs to be isolated from other 200 services and hard isolated tunnel is required. 202 3.2. Integration of Large-scale Heterogeneous Network 204 In WAN application, large-scale number of nodes and long-distance 205 transmission in the network will lead to latency and jitter, such as 206 increasing transmission latency, jitter and packet loss. It is to 207 required reduce the scale of the network topology by establishing 208 cutthrough channels. The existing technologies such as FlexE and SR 209 tunnels should be taken into consideration. And multiple 210 capabilities is also provided by the nodes and links within the 211 network topology such as FlexE tunnels, TSN sub-network and IP/MPLS/ 212 SRv6 tunnels. It is required to integrate the multi-capability 213 resources to achieve the optimal DetNet QoS. 215 Another option is to divide the network into several domains and 216 segments. And the deadline of latency and jitter of each domain and 217 segment should be determined and controlled. It is required to 218 control the DetNet QoS at the inter-domain boundary nodes and achieve 219 the end-to-end latency, bounded jitter and packet loss ratio across. 221 3.3. Efficiency of Resources Utilization and Routes Steering 223 Traditional Ethernet, IP and MPLS networks which is based on 224 statistical multiplexing provides best-effort packet service and 225 offers no delivery and SLA guarantee. As described in [RFC8655], the 226 primary technique by which DetNet achieves its QoS is to allocate 227 sufficient resources. But it can not be achieved by not sufficient 228 resource which can be allocated due to practical and cost reason. So 229 it is required to achieve the high-efficiency of resources 230 utilization when provide the DetNet service. 232 Network resources include nodes, links, ports, bandwidth, queues, 233 etc. The congestion control, shaping and queue scheduling and other 234 traffic mechanisms which have been proposed in IEEE 802.1 TSN such as 235 IEEE802.1Qbv, IEEE802.1Qch, IEEE802.1Qav, IEEE802.1Qcr and so on. 236 Heterogeneous resource should be used and unified and simplified 237 resources mechanism under the selection of existing multiple 238 technical methods to realize the elastic of deterministic capability. 240 Resource classification and modeling is required along with the 241 explicit path with more SLA guarantee parameters like bandwidth, 242 latency, jitter, packet loss and so on. On the basic of the 243 resources, the steering path and routes for deterministic flows 244 should be programmed before the flows coming and able to provide SLA 245 capability. And the routes should be considered to be established in 246 distributed and centralized control Plane. 248 3.4. Guarantees of Multiple Dynamic Deterministic Flows 250 As described in [RFC8557], deterministic forwarding can only apply to 251 flows with such well-defined characteristics as periodicity and 252 burstiness. As defined in DetNet architecture [RFC8655], the traffic 253 characteristics of an App-flow can be CBR (constant bit rate) or VBR 254 (variable bit rate) of L1, L2 and L3 layers (VBR takes the maximum 255 value when reserving resources). But the current scenarios and 256 technical solutions only consider CBR flow, without considering the 257 coexistence of VBR and CBR, the burst and aperiodicity of flows. The 258 operations such as shaping or scheduling have not been specified. 259 Even TSN mechanisms are based on a constant and forecastable traffic 260 characteristics. 262 It will be more complicated in WAN applications where much more flows 263 coexist and the traffic characteristics is more dynamic. It is 264 required to offer reliable delivery and SLA guarantee for dynamic 265 flows. For example, periodic flow and aperiodic flow (including 266 micro burst flow, etc.), CBR and VBR flow, flow with different 267 periods or phases, etc. When the network needs to forward these 268 deterministic flows at the same time, it must solve the problems of 269 time window selection, queue processing and aggregation of multiple 270 flows. It is required to classify the dynamic deterministic flows 271 and map them into different virtual topologies to limit the number of 272 the concurrent flows and reduce the micro bursts. 274 4. Solutions Considerations of Wide-area IP Deterministic Networking 276 4.1. The Deterministic Resources 278 As defined in RFC8655, the resource allocation is one of the 279 techniques to achieve the DetNet QoS. Network resources include 280 nodes, links, ports, bandwidth, queues, etc. The deterministic 281 resources require planning and arrangement of network resources, 282 resources modeling, resource allocation and reservation, resource 283 isolation and resource scheduling, etc. In order to meet the 284 requirements of deterministic service, resources need to be 285 classified, including ultra-low delay resources, low delay resources, 286 low jitter resources, etc. 288 Deterministic resources guarantee the delay, jitter and other 289 requirements of deterministic services by reserving resources for 290 flows. If the network resources are sufficient, congestion and 291 packet loss can be eliminated to meet the requirements of low delay 292 jitter. If the network resources are insufficient, congestion 293 control, queue mechanisms of deterministic flows need to be carried 294 out. The nodes with different queue mechanisms provide different 295 latency and bounded jitter. Moreover, network resources could to be 296 reconstructed to provide ultra-low latency, for example, L1 layer 297 resources could be used to provide cutthrough channels, FlexE pipes, 298 etc. 300 4.2. The Deterministic Routes 302 The deterministic routes is based on the provision of deterministic 303 resources. The deterministic routes refers to the requirements to 304 select the network routes for the deterministic flows to guarantee 305 the stability of the routing at least during the packets 306 transmission, and the path will not change within the real-time 307 change of network topology. Moreover, the deterministic routes 308 should provide the capability including the latency, jitter and 309 packet loss ratio. 311 Routes generally perform forwarding function including receiving the 312 incoming packets and forwarding the packets to a Router based on the 313 header information and a forwarding information base. It is 314 necessary to provide pre-routes with SLA capability and generate 315 endogenous deterministic routing with deterministic capability. The 316 deterministic routes perform the functions of forwarding and QoS 317 guarantee at the same time. The types of deterministic routes can be 318 classified into ultra-low delay routes, low delay routes, low jitter 319 routes, and so on. There can also has replication routes and 320 aggregation routes. 322 The mechanisms of path establishment include traffic engineering 323 technology (MPLS-TE, SR-TE, static configuration, etc.), IGP 324 technology, etc. Explicit strict routing can guarantee the delay 325 jitter and other requirements of services. Loose routing only 326 generates some endogenous deterministic routes, and other routes 327 still need forwarding and scheduling, such as dynamic resource-aware 328 routing and queue scheduling. 330 4.3. The Deterministic QoS 332 The deterministic QoS is to arrange and schedule the deterministic 333 flows on the basis of providing deterministic resources and routes, 334 so as to control of each flow and meet the DetNet QoS goals. 336 The scheduling and control include the classification of the 337 deterministic flows, queue scheduling mechanism for each class of 338 deterministic flow, deterministic shaping at boundary nodes, limiting 339 the number of concurrent flows and reducing micro bursts, mapping the 340 dynamic concurrent flows into different virtual topologies. 341 Moreover, flow aggregation is performed at the aggregation node to 342 reduce flow state maintenance and replication or elimination is 343 performed at the relay node to achieve reliability. 345 If the deterministic flows crosses multiple domains, the end-to-end 346 latency is the sum of delay from all domains. It is required to 347 control the deadline delay of each domain. Moreover, bounded jitter 348 (packet delay variation) should be adjusted and scheduled at the 349 inter-domain boundary nodes. 351 5. Security Considerations 353 TBA 355 6. Acknowledgements 357 TBA 359 7. IANA Considerations 361 TBA 363 8. Normative References 365 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 366 Requirement Levels", BCP 14, RFC 2119, 367 DOI 10.17487/RFC2119, March 1997, 368 . 370 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 371 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 372 May 2017, . 374 [RFC8557] Finn, N. and P. Thubert, "Deterministic Networking Problem 375 Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019, 376 . 378 [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", 379 RFC 8578, DOI 10.17487/RFC8578, May 2019, 380 . 382 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, 383 "Deterministic Networking Architecture", RFC 8655, 384 DOI 10.17487/RFC8655, October 2019, 385 . 387 Author's Address 389 Quan Xiong 390 ZTE Corporation 391 No.6 Huashi Park Rd 392 Wuhan 393 Hubei, 430223 394 China 396 Email: xiong.quan@zte.com.cn