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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DetNet N. Finn 3 Internet-Draft Huawei Technologies Co. Ltd 4 Intended status: Standards Track P. Thubert 5 Expires: May 3, 2018 Cisco 6 B. Varga 7 J. Farkas 8 Ericsson 9 October 30, 2017 11 Deterministic Networking Architecture 12 draft-ietf-detnet-architecture-04 14 Abstract 16 Deterministic Networking (DetNet) provides a capability to carry 17 specified unicast or multicast data flows for real-time applications 18 with extremely low data loss rates and bounded latency. Techniques 19 used include: 1) reserving data plane resources for individual (or 20 aggregated) DetNet flows in some or all of the intermediate nodes 21 (e.g. bridges or routers) along the path of the flow; 2) providing 22 explicit routes for DetNet flows that do not rapidly change with the 23 network topology; and 3) distributing data from DetNet flow packets 24 over time and/or space to ensure delivery of each packet's data' in 25 spite of the loss of a path. The capabilities can be managed by 26 configuration, or by manual or automatic network management. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on May 3, 2018. 45 Copyright Notice 47 Copyright (c) 2017 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 2.1. Terms used in this document . . . . . . . . . . . . . . . 4 65 2.2. IEEE 802 TSN to DetNet dictionary . . . . . . . . . . . . 6 66 3. Providing the DetNet Quality of Service . . . . . . . . . . . 7 67 3.1. Primary goals defining the DetNet QoS . . . . . . . . . . 7 68 3.2. Mechanisms to achieve DetNet Qos . . . . . . . . . . . . 9 69 3.2.1. Congestion protection . . . . . . . . . . . . . . . . 9 70 3.2.2. Explicit routes . . . . . . . . . . . . . . . . . . . 9 71 3.2.3. Jitter Reduction . . . . . . . . . . . . . . . . . . 10 72 3.2.4. Packet Replication and Elimination . . . . . . . . . 11 73 3.3. Secondary goals for DetNet . . . . . . . . . . . . . . . 12 74 3.3.1. Coexistence with normal traffic . . . . . . . . . . . 12 75 3.3.2. Fault Mitigation . . . . . . . . . . . . . . . . . . 13 76 4. DetNet Architecture . . . . . . . . . . . . . . . . . . . . . 14 77 4.1. DetNet stack model . . . . . . . . . . . . . . . . . . . 14 78 4.1.1. Representative Protocol Stack Model . . . . . . . . . 14 79 4.1.2. DetNet Data Plane Overview . . . . . . . . . . . . . 16 80 4.1.3. Network reference model . . . . . . . . . . . . . . . 18 81 4.2. DetNet systems . . . . . . . . . . . . . . . . . . . . . 19 82 4.2.1. End system . . . . . . . . . . . . . . . . . . . . . 19 83 4.2.2. DetNet edge, relay, and transit nodes . . . . . . . . 20 84 4.3. DetNet flows . . . . . . . . . . . . . . . . . . . . . . 21 85 4.3.1. DetNet flow types . . . . . . . . . . . . . . . . . . 21 86 4.3.2. Source guarantees . . . . . . . . . . . . . . . . . . 21 87 4.3.3. Incomplete Networks . . . . . . . . . . . . . . . . . 23 88 4.4. Traffic Engineering for DetNet . . . . . . . . . . . . . 23 89 4.4.1. The Application Plane . . . . . . . . . . . . . . . . 23 90 4.4.2. The Controller Plane . . . . . . . . . . . . . . . . 24 91 4.4.3. The Network Plane . . . . . . . . . . . . . . . . . . 24 92 4.5. Queuing, Shaping, Scheduling, and Preemption . . . . . . 25 93 4.6. Service instance . . . . . . . . . . . . . . . . . . . . 26 94 4.7. Flow identification at technology borders . . . . . . . . 27 95 4.7.1. Exporting flow identification . . . . . . . . . . . . 27 96 4.7.2. Flow attribute mapping between layers . . . . . . . . 29 97 4.7.3. Flow-ID mapping examples . . . . . . . . . . . . . . 30 98 4.8. Advertising resources, capabilities and adjacencies . . . 32 99 4.9. Provisioning model . . . . . . . . . . . . . . . . . . . 32 100 4.9.1. Centralized Path Computation and Installation . . . . 32 101 4.9.2. Distributed Path Setup . . . . . . . . . . . . . . . 32 102 4.10. Scaling to larger networks . . . . . . . . . . . . . . . 33 103 4.11. Connected islands vs. networks . . . . . . . . . . . . . 33 104 4.12. Compatibility with Layer-2 . . . . . . . . . . . . . . . 33 105 5. Security Considerations . . . . . . . . . . . . . . . . . . . 34 106 6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 34 107 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35 108 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35 109 9. Access to IEEE 802.1 documents . . . . . . . . . . . . . . . 35 110 10. Informative References . . . . . . . . . . . . . . . . . . . 35 111 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 113 1. Introduction 115 Deterministic Networking (DetNet) is a service that can be offered by 116 a network to DetNet flows. DetNet provides these flows extremely low 117 packet loss rates and assured maximum end-to-end delivery latency. 118 This is accomplished by dedicating network resources such as link 119 bandwidth and buffer space to DetNet flows and/or classes of DetNet 120 flows, and by replicating packets along multiple paths. Unused 121 reserved resources are available to non-DetNet packets. 123 The Deterministic Networking Problem Statement 124 [I-D.ietf-detnet-problem-statement] introduces Deterministic 125 Networking, and Deterministic Networking Use Cases 126 [I-D.ietf-detnet-use-cases] summarizes the need for it. See 127 [I-D.dt-detnet-dp-alt] for a discussion of specific techniques that 128 can be used to identify DetNet Flows and assign them to specific 129 paths through a network. 131 A goal of DetNet is a converged network in all respects. That is, 132 the presence of DetNet flows does not preclude non-DetNet flows, and 133 the benefits offered DetNet flows should not, except in extreme 134 cases, prevent existing QoS mechanisms from operating in a normal 135 fashion, subject to the bandwidth required for the DetNet flows. A 136 single source-destination pair can trade both DetNet and non-DetNet 137 flows. End systems and applications need not instantiate special 138 interfaces for DetNet flows. Networks are not restricted to certain 139 topologies; connectivity is not restricted. Any application that 140 generates a data flow that can be usefully characterized as having a 141 maximum bandwidth should be able to take advantage of DetNet, as long 142 as the necessary resources can be reserved. Reservations can be made 143 by the application itself, via network management, by an applications 144 controller, or by other means. 146 Many applications of interest to Deterministic Networking require the 147 ability to synchronize the clocks in end systems to a sub-microsecond 148 accuracy. Some of the queue control techniques defined in 149 Section 4.5 also require time synchronization among relay and transit 150 nodes. The means used to achieve time synchronization are not 151 addressed in this document. DetNet should accommodate various 152 synchronization techniques and profiles that are defined elsewhere to 153 solve exchange time in different market segments. 155 Wired and wireless media differ greatly in a number of ways, 156 including connectivity possibilities and the reliability of packet 157 transmission. While some of the techniques described in this 158 document may be applicable to wireless media, the DetNet architecture 159 assumes the use of links with characteristics typical of wired, and 160 not wireless, media. 162 2. Terminology 164 2.1. Terms used in this document 166 The following special terms are used in this document in order to 167 avoid the assumption that a given element in the architecture does or 168 does not have Internet Protocol stack, functions as a router, bridge, 169 firewall, or otherwise plays a particular role at Layer-2 or higher. 171 App-flow 172 The native format of a DetNet flow. 174 destination 175 An end system capable of receiving a DetNet flow. 177 DetNet domain 178 The portion of a network that is DetNet aware. It includes 179 end systems and other DetNet nodes. 181 DetNet flow 182 A DetNet flow is a sequence of packets to which the DetNet 183 service is to be provided. 185 DetNet compound flow and DetNet member flow 186 A DetNet compound flow is a DetNet flow that has been 187 separated into multiple duplicate DetNet member flows, which 188 are eventually merged back into a single DetNet compound 189 flow, at the DetNet transport layer. "Compound" and "member" 190 are strictly relative to each other, not absolutes; a DetNet 191 compound flow comprising multiple DetNet member flows can, in 192 turn, be a member of a higher-order compound. 194 DetNet intermediate node 195 A DetNet relay node or transit node. 197 DetNet edge node 198 An instance of a DetNet relay node that includes either a 199 DetNet service layer proxy function for DetNet service 200 protection (e.g. the addition or removal of packet sequencing 201 information) for one or more end systems, or starts or 202 terminates congestion protection at the DetNet transport 203 layer, analogous to a Label Edge Router (LER). 205 DetNet-UNI 206 User-to-Network Interface with DetNet specific 207 functionalities. It is a packet-based reference point and 208 may provide multiple functions like encapsulation, status, 209 synchronization, etc. 211 end system 212 Commonly called a "host" or "node" in IETF documents, and an 213 "end station" is IEEE 802 documents. End systems of interest 214 to this document are either sources or destinations of DetNet 215 flows. And end system may or may not be DetNet transport 216 layer aware or DetNet service layer aware. 218 link 219 A connection between two DetNet nodes. It may be composed of 220 a physical link or a sub-network technology that can provide 221 appropriate traffic delivery for DetNet flows. 223 DetNet node 224 A DetNet aware end system, transit node, or relay node. 225 "DetNet" may be omitted in some text. 227 Detnet relay node 228 A DetNet node including a service layer function that 229 interconnects different DetNet transport layer paths to 230 provide service protection. A DetNet relay node can be a 231 bridge, a router, a firewall, or any other system that 232 participates in the DetNet service layer. It typically 233 incorporates DetNet transport layer functions as well, in 234 which case it is collocated with a transit node. 236 reservation 237 A trail of configuration between source to destination(s) 238 through transit nodes and subnets associated with a DetNet 239 flow, to provide congestion protection. 241 DetNet service layer 242 The layer at which service protection is provided, packet 243 sequencing, replication, and elimination (Section 3.2.4) or 244 packet encoding. 246 source 247 An end system capable of sourcing a DetNet flow. 249 DetNet transit node 250 A node operating at the DetNet transport layer, that utilizes 251 link layer and/or network layer switching across multiple 252 links and/or sub-networks to provide paths for DetNet service 253 layer functions. Optionally provides congestion protection 254 over those paths. An MPLS LSR is an example of a DetNet 255 transit node. 257 DetNet transport layer 258 The layer that optionally provides congestion protection for 259 DetNet flows over paths provided by the underlying network. 261 TSN 262 Time-Sensitive Networking, TSN is a Task Group of the IEEE 263 802.1 Working Group. 265 2.2. IEEE 802 TSN to DetNet dictionary 267 This section also serves as a dictionary for translating from the 268 terms used by the IEEE 802 Time-Sensitive Networking (TSN) Task Group 269 to those of the DetNet WG. 271 Listener 272 The IEEE 802 term for a destination of a DetNet flow. 274 relay system 275 The IEEE 802 term for a DetNet intermediate node. 277 Stream 278 The IEEE 802 term for a DetNet flow. 280 Talker 281 The IEEE 802 term for the source of a DetNet flow. 283 3. Providing the DetNet Quality of Service 285 3.1. Primary goals defining the DetNet QoS 287 The DetNet Quality of Service can be expressed in terms of: 289 o Minimum and maximum end-to-end latency from source to destination; 290 timely delivery and jitter avoidance derive from these constraints 292 o Probability of loss of a packet, under various assumptions as to 293 the operational states of the nodes and links. A derived property 294 is whether it is acceptable to deliver a duplicate packet, which 295 is an inherent risk in highly reliable and/or broadcast 296 transmissions 298 It is a distinction of DetNet that it is concerned solely with worst- 299 case values for the end-to-end latency. Average, mean, or typical 300 values are of no interest, because they do not affect the ability of 301 a real-time system to perform its tasks. In general, a trivial 302 priority-based queuing scheme will give better average latency to a 303 data flow than DetNet, but of course, the worst-case latency can be 304 essentially unbounded. 306 Three techniques are used by DetNet to provide these qualities of 307 service: 309 o Congestion protection (Section 3.2.1). 311 o Explicit routes (Section 3.2.2). 313 o Service protection (Section 3.2.4). 315 Congestion protection operates by reserving resources along the path 316 of a DetNet Flow, e.g. buffer space or link bandwidth. Congestion 317 protection greatly reduces, or even eliminates entirely, packet loss 318 due to output packet congestion within the network, but it can only 319 be supplied to a DetNet flow that is limited at the source to a 320 maximum packet size and transmission rate. 322 Congestion protection addresses both of the DetNet QoS requirements 323 (latency and packet loss). Given that DetNet nodes have a finite 324 amount of buffer space, congestion protection necessarily results in 325 a maximum end-to-end latency. It also addresses the largest 326 contribution to packet loss, which is buffer congestion. 328 After congestion, the most important contributions to packet loss are 329 typically from random media errors and equipment failures. Service 330 protection is the name for the mechanisms used by DetNet to address 331 these losses. The mechanisms employed are constrained by the 332 requirement to meet the users' latency requirements. Packet 333 replication and elimination (Section 3.2.4) is described in this 334 document to provide service protection; others may be found. This 335 mechanism distributes the contents of DetNet flows over multiple 336 paths in time and/or space, so that the loss of some of the paths 337 does need not cause the loss of any packets. The paths are typically 338 (but not necessarily) explicit routes, so that they cannot suffer 339 temporary interruptions caused by the reconvergence of routing or 340 bridging protocols. 342 These three techniques can be applied independently, giving eight 343 possible combinations, including none (no DetNet), although some 344 combinations are of wider utility than others. This separation keeps 345 the protocol stack coherent and maximizes interoperability with 346 existing and developing standards in this (IETF) and other Standards 347 Development Organizations. Some examples of typical expected 348 combinations: 350 o Explicit routes plus service protection are exactly the techniques 351 employed by [HSR-PRP]. Explicit routes are achieved by limiting 352 the physical topology of the network, and the sequentialization, 353 replication, and duplicate elimination are facilitated by packet 354 tags added at the front or the end of Ethernet frames. 356 o Congestion protection alone is is offered by IEEE 802.1 Audio 357 Video bridging [IEEE802.1BA-2011]. As long as the network suffers 358 no failures, zero congestion loss can be achieved through the use 359 of a reservation protocol (MSRP), shapers in every bridge, and a 360 bit of network calculus. 362 o Using all three together gives maximum protection. 364 There are, of course, simpler methods available (and employed, today) 365 to achieve levels of latency and packet loss that are satisfactory 366 for many applications. Prioritization and over-provisioning is one 367 such technique. However, these methods generally work best in the 368 absence of any significant amount of non-critical traffic in the 369 network (if, indeed, such traffic is supported at all), or work only 370 if the critical traffic constitutes only a small portion of the 371 network's theoretical capacity, or work only if all systems are 372 functioning properly, or in the absence of actions by end systems 373 that disrupt the network's operations. 375 There are any number of methods in use, defined, or in progress for 376 accomplishing each of the above techniques. It is expected that this 377 DetNet Architecture will assist various vendors, users, and/or 378 "vertical" Standards Development Organizations (dedicated to a single 379 industry) to make selections among the available means of 380 implementing DetNet networks. 382 3.2. Mechanisms to achieve DetNet Qos 384 3.2.1. Congestion protection 386 The primary means by which DetNet achieves its QoS assurances is to 387 reduce, or even completely eliminate, congestion at an output port as 388 a cause of packet loss. Given that a DetNet flow cannot be 389 throttled, this can be achieved only by the provision of sufficient 390 buffer storage at each hop through the network to ensure that no 391 packets are dropped due to a lack of buffer storage. 393 Ensuring adequate buffering requires, in turn, that the source, and 394 every intermediate node along the path to the destination (or nearly 395 every node -- see Section 4.3.3) be careful to regulate its output to 396 not exceed the data rate for any DetNet flow, except for brief 397 periods when making up for interfering traffic. Any packet sent 398 ahead of its time potentially adds to the number of buffers required 399 by the next hop, and may thus exceed the resources allocated for a 400 particular DetNet flow. 402 The low-level mechanisms described in Section 4.5 provide the 403 necessary regulation of transmissions by an end system or 404 intermediate node to provide congestion protection. The reservation 405 of the bandwidth and buffers for a DetNet flow requires the 406 provisioning described in Section 4.9. A DetNet node may have other 407 resources requiring allocation and/or scheduling, that might 408 otherwise be over-subscribed and trigger the rejection of a 409 reservation. 411 3.2.2. Explicit routes 413 In networks controlled by typical peer-to-peer protocols such as IEEE 414 802.1 ISIS bridged networks or IETF OSPF routed networks, a network 415 topology event in one part of the network can impact, at least 416 briefly, the delivery of data in parts of the network remote from the 417 failure or recovery event. Thus, even redundant paths through a 418 network, if controlled by the typical peer-to-peer protocols, do not 419 eliminate the chances of brief losses of contact. 421 Many real-time networks rely on physical rings or chains of two-port 422 devices, with a relatively simple ring control protocol. This 423 supports redundant paths for service protection with a minimum of 424 wiring. As an additional benefit, ring topologies can often utilize 425 different topology management protocols than those used for a mesh 426 network, with a consequent reduction in the response time to topology 427 changes. Of course, this comes at some cost in terms of increased 428 hop count, and thus latency, for the typical path. 430 In order to get the advantages of low hop count and still ensure 431 against even very brief losses of connectivity, DetNet employs 432 explicit routes, where the path taken by a given DetNet flow does not 433 change, at least immediately, and likely not at all, in response to 434 network topology events. Service protection (Section 3.2.4) over 435 explicit routes provides a high likelihood of continuous 436 connectivity. Explicit routes are commonly used in MPLS TE LSPs. 438 3.2.3. Jitter Reduction 440 A core objective of DetNet is to enable the convergence of Non-IP 441 networks onto a common network infrastructure. This requires the 442 accurate emulation of currently deployed mission-specific networks, 443 which typically rely on point-to-point analog (e.g. 4-20mA 444 modulation) and serial-digital cables (or buses) for highly reliable, 445 synchronized and jitter-free communications. While the latency of 446 analog transmissions is basically the speed of light, legacy serial 447 links are usually slow (in the order of Kbps) compared to, say, GigE, 448 and some latency is usually acceptable. What is not acceptable is 449 the introduction of excessive jitter, which may, for instance, affect 450 the stability of control systems. 452 Applications that are designed to operate on serial links usually do 453 not provide services to recover the jitter, because jitter simply 454 does not exists there. Streams of information are expected to be 455 delivered in-order and the precise time of reception influences the 456 processes. In order to converge such existing applications, there is 457 a desire to emulate all properties of the serial cable, such as clock 458 transportation, perfect flow isolation and fixed latency. While 459 minimal jitter (in the form of specifying minimum, as well as 460 maximum, end-to-end latency) is supported by DetNet, there are 461 practical limitations on packet-based networks in this regard. In 462 general, users are encouraged to use, instead of, "do this when you 463 get the packet," a combination of: 465 o Sub-microsecond time synchronization among all source and 466 destination end systems, and 468 o Time-of-execution fields in the application packets. 470 Jitter reduction is provided by the mechanisms described in 471 Section 4.5 that also provide congestion protection. 473 3.2.4. Packet Replication and Elimination 475 After congestion loss has been eliminated, the most important causes 476 of packet loss are random media and/or memory faults, and equipment 477 failures. Both causes of packet loss can be greatly reduced by 478 spreading the data in a packet over multiple transmissions. One such 479 method for service protection is described in this section, which 480 sends the same packets over multiple paths. 482 Packet replication and elimination, also known as seamless redundancy 483 [HSR-PRP], or 1+1 hitless protection, is a function of the DetNet 484 service layer. It involves three capabilities: 486 o Providing sequencing information, once, at or near the source, to 487 the packets of a DetNet compound flow. This may be done by adding 488 a sequence number or time stamp as part of DetNet, or may be 489 inherent in the packet, e.g. in a transport protocol, or 490 associated to other physical properties such as the precise time 491 (and radio channel) of reception of the packet. Section 3.2.2. 493 o Replicating these packets into multiple DetNet member flows and, 494 typically, sending them along at least two different paths to the 495 destination(s), e.g. over the explicit routes of 497 o Eliminating duplicated packets. This may be done at any step 498 along the path to save network resources further down, in 499 particular if multiple Replication points exist. But the most 500 common case is to perform this operation at the very edge of the 501 DetNet network, preferably in or near the receiver. 503 This function is a "hitless" version of, e.g., the 1+1 linear 504 protection in [RFC6372]. That is, instead of switching from one flow 505 to the other when a failure of a flow is detected, DetNet combines 506 both flows, and performs a packet-by-packet selection of which to 507 discard, based on sequence number. 509 In the simplest case, this amounts to replicating each packet in a 510 source that has two interfaces, and conveying them through the 511 network, along separate paths, to the similarly dual-homed 512 destinations, that discard the extras. This ensures that one path 513 (with zero congestion loss) remains, even if some intermediate node 514 fails. The sequence numbers can also be used for loss detection and 515 for re-ordering. 517 Detnet relay nodes in the network can provide replication and 518 elimination facilities at various points in the network, so that 519 multiple failures can be accommodated. 521 This is shown in the following figure, where the two relay nodes each 522 replicate (R) the DetNet flow on input, sending the DetNet member 523 flows to both the other relay node and to the end system, and 524 eliminate duplicates (E) on the output interface to the right-hand 525 end system. Any one link in the network can fail, and the Detnet 526 compound flow can still get through. Furthermore, two links can 527 fail, as long as they are in different segments of the network. 529 Packet replication and elimination 531 > > > > > > > > > relay > > > > > > > > 532 > /------------+ R node E +------------\ > 533 > / v + ^ \ > 534 end R + v | ^ + E end 535 system + v | ^ + system 536 > \ v + ^ / > 537 > \------------+ R relay E +-----------/ > 538 > > > > > > > > > node > > > > > > > > 540 Figure 1 542 Packet replication and elimination does not react to and correct 543 failures; it is entirely passive. Thus, intermittent failures, 544 mistakenly created packet filters, or misrouted data is handled just 545 the same as the equipment failures that are detected handled by 546 typical routing and bridging protocols. 548 If packet replication and elimination is used over paths providing 549 congestion protection (Section 3.2.1), and member flows that take 550 different-length paths through the network are combined, a merge 551 point may require extra buffering to equalize the delays over the 552 different paths. This equalization ensures that the resultant 553 compound flow will not exceed its contracted bandwidth even after one 554 or the other of the paths is restored after a failure. 556 3.3. Secondary goals for DetNet 558 Many applications require DetNet to provide additional services, 559 including coesistence with other QoS mechanisms Section 3.3.1 and 560 protection against misbehaving transmitters Section 3.3.2. 562 3.3.1. Coexistence with normal traffic 564 A DetNet network supports the dedication of a high proportion (e.g. 565 75%) of the network bandwidth to DetNet flows. But, no matter how 566 much is dedicated for DetNet flows, it is a goal of DetNet to coexist 567 with existing Class of Service schemes (e.g., DiffServ). It is also 568 important that non-DetNet traffic not disrupt the DetNet flow, of 569 course (see Section 3.3.2 and Section 5). For these reasons: 571 o Bandwidth (transmission opportunities) not utilized by a DetNet 572 flow are available to non-DetNet packets (though not to other 573 DetNet flows). 575 o DetNet flows can be shaped or scheduled, in order to ensure that 576 the highest-priority non-DetNet packet also is ensured a worst- 577 case latency (at any given hop). 579 o When transmission opportunities for DetNet flows are scheduled in 580 detail, then the algorithm constructing the schedule should leave 581 sufficient opportunities for non-DetNet packets to satisfy the 582 needs of the users of the network. Detailed scheduling can also 583 permit the time-shared use of buffer resources by different DetNet 584 flows. 586 Ideally, the net effect of the presence of DetNet flows in a network 587 on the non-DetNet packets is primarily a reduction in the available 588 bandwidth. 590 3.3.2. Fault Mitigation 592 One key to building robust real-time systems is to reduce the 593 infinite variety of possible failures to a number that can be 594 analyzed with reasonable confidence. DetNet aids in the process by 595 providing filters and policers to detect DetNet packets received on 596 the wrong interface, or at the wrong time, or in too great a volume, 597 and to then take actions such as discarding the offending packet, 598 shutting down the offending DetNet flow, or shutting down the 599 offending interface. 601 It is also essential that filters and service remarking be employed 602 at the network edge to prevent non-DetNet packets from being mistaken 603 for DetNet packets, and thus impinging on the resources allocated to 604 DetNet packets. 606 There exist techniques, at present and/or in various stages of 607 standardization, that can perform these fault mitigation tasks that 608 deliver a high probability that misbehaving systems will have zero 609 impact on well-behaved DetNet flows, except of course, for the 610 receiving interface(s) immediately downstream of the misbehaving 611 device. Examples of such techniques include traffic policing 612 functions (e.g. [RFC2475]) and separating flows into per-flow rate- 613 limited queues. 615 4. DetNet Architecture 617 4.1. DetNet stack model 619 4.1.1. Representative Protocol Stack Model 621 Figure 2 illustrates a conceptual DetNet data plane layering model. 622 One may compare it to that in [IEEE802.1CB], Annex C, a work in 623 progress. 625 DetNet data plane protocol stack 627 | packets going | ^ packets coming ^ 628 v down the stack v | up the stack | 629 +----------------------+ +-----------------------+ 630 | Source | | Destination | 631 +----------------------+ +-----------------------+ 632 | Service layer | | Service layer | 633 | Packet sequencing | | Duplicate elimination | 634 | Flow duplication | | Flow merging | 635 | Packet encoding | | Packet decoding | 636 +----------------------+ +-----------------------+ 637 | Transport layer | | Transport layer | 638 | Congestion prot. | | Congestion prot. | 639 +----------------------+ +-----------------------+ 640 | Lower layers | | Lower layers | 641 +----------------------+ +-----------------------+ 642 v ^ 643 \_________________________/ 645 Figure 2 647 Not all layers are required for any given application, or even for 648 any given network. The layers are, from top to bottom: 650 Application 651 Shown as "source" and "destination" in the diagram. 653 OAM 654 Operations, Administration, and Maintenance leverages in-band 655 and out-of-and signaling that validates whether the service 656 is effectively obtained within QoS constraints. OAM is not 657 shown in Figure 2; it may reside in any number of the layers. 658 OAM can involve specific tagging added in the packets for 659 tracing implementation or network configuration errors; 660 traceability enables to find whether a packet is a replica, 661 which relay node performed the replication, and which segment 662 was intended for the replica. 664 Packet sequencing 665 As part of DetNet service protection, supplies the sequence 666 number for packet replication and elimination 667 (Section 3.2.4). Peers with Duplicate elimination. This 668 layer is not needed if a higher-layer transport protocol is 669 expected to perform any packet sequencing and duplicate 670 elimination required by the DetNet flow duplication. 672 Duplicate elimination 673 As part of the DetNet service layer, based on the sequenced 674 number supplied by its peer, packet sequencing, Duplicate 675 elimination discards any duplicate packets generated by 676 DetNet flow duplication. It can operate on member flows, 677 compound flows, or both. The duplication may also be 678 inferred from other information such as the precise time of 679 reception in a scheduled network. The duplicate elimination 680 layer may also perform resequencing of packets to restore 681 packet order in a flow that was disrupted by the loss of 682 packets on one or another of the multiple paths taken. 684 Flow duplication 685 As part of DetNet service protection, packets that belong to 686 a DetNet compound flow are replicated into two or more DetNet 687 member flows. This function is separate from packet 688 sequencing. Flow duplication can be an explicit duplication 689 and remarking of packets, or can be performed by, for 690 example, techniques similar to ordinary multicast 691 replication. Peers with DetNet flow merging. 693 Network flow merging 694 As part of DetNet service protection, merges DetNet member 695 flows together for packets coming up the stack belonging to a 696 specific DetNet compound flow. Peers with DetNet flow 697 duplication. DetNet flow merging, together with packet 698 sequencing, duplicate elimination, and DetNet flow 699 duplication, performs packet replication and elimination 700 (Section 3.2.4). 702 Packet encoding 703 As part of DetNet service protection, as an alternative to 704 packet sequencing and flow duplication, packet encoding 705 combines the information in multiple DetNet packets, perhaps 706 from different DetNet compound flows, and transmits that 707 information in packets on different DetNet member Flows. 708 Peers with Packet decoding. 710 Packet decoding 711 As part of DetNet service protection, as an alternative to 712 flow merging and duplicate elimination, packet decoding takes 713 packets from different DetNet member flows, and computes from 714 those packets the original DetNet packets from the compound 715 flows input to packet encoding. Peers with Packet encoding. 717 Congestion protection 718 The DetNet transport layer provides congestion protection. 719 See Section 4.5. The actual queuing and shaping mechanisms 720 are typically provided by underlying subnet layers, but since 721 these are can be closely associated with the means of 722 providing paths for DetNet flows (e.g. MPLS LSPs or {VLAN, 723 multicast destination MAC address} pairs), the path and the 724 congestion protection are conflated in this figure. 726 The packet sequencing and duplication elimination functions at the 727 source and destination ends of a DetNet compound flow may be 728 performed either in the end system or in a DetNet edge node. The 729 reader must not confuse a DetNet edge function with other kinds of 730 edge functions, e.g. an Label Edge Router, although the two functions 731 may be performed together. The DetNet edge function is concerned 732 with sequencing packets belonging to DetNet flows. The LER with 733 encapsulating/decapsulating packets for transport, and is considered 734 part of the network underlying the DetNet transport layer. 736 4.1.2. DetNet Data Plane Overview 738 A "Deterministic Network" will be composed of DetNet enabled nodes 739 i.e., End Systems, Edge Nodes, Relay Nodes and collectively deliver 740 DetNet services. DetNet enabled nodes are interconnected via Transit 741 Nodes (i.e., routers) which support DetNet, but are not DetNet 742 service aware. Transit nodes see DetNet nodes as end points. All 743 DetNet enabled nodes are connect to sub-networks, where a point-to- 744 point link is also considered as a simple sub-network. These sub- 745 networks will provide DetNet compatible service for support of DetNet 746 traffic. Examples of sub-networks include IEEE 802.1 TSN and OTN. 747 Of course, multi-layer DetNet systems may also be possible, where one 748 DetNet appears as a sub-network, and provides service to, a higher 749 layer DetNet system. A simple DetNet concept network is shown in 750 Figure 3. 752 TSN Edge Transit Relay DetNet 753 End System Node Node Node End System 755 +---------+ +.........+ +---------+ 756 | Appl. |<---:Svc Proxy:-- End to End Service ---------->| Appl. | 757 +---------+ +---------+ +---------+ +---------+ 758 | TSN | |TSN| |Svc|<-- DetNet flow ---: Service :-->| Service | 759 +---------+ +---+ +---+ +---------+ +---------+ +---------+ 760 |Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport| 761 +-------.-+ +-.-+ +-.-+ +--.----.-+ +-.-+ +-.-+ +---.-----+ 762 : Link : / ,-----. \ : Link : / ,-----. \ 763 +........+ +-[ Sub ]-+ +........+ +-[ Sub ]-+ 764 [Network] [Network] 765 `-----' `-----' 767 Figure 3: A Simple DetNet Enabled Network 769 Distinguishing the function of these two DetNet data plane layers, 770 the DetNet service layer and the DetNet transport layer, helps to 771 explore and evaluate various combinations of the data plane solutions 772 available. This separation of DetNet layers, while helpful, should 773 not be considered as formal requirement. For example, some 774 technologies may violate these strict layers and still be able to 775 deliver a DetNet service. 777 . 778 . 779 +-----------+ 780 | Service | PW, RTP/(UDP), GRE 781 +-----------+ 782 | Transport | (UDP)/IPv6, (UDP)/IPv4, MPLS LSPs, BIER 783 +-----------+ 784 . 785 . 787 Figure 4: DetNet adaptation to data plane 789 In some networking scenarios, the end system initially provides a 790 DetNet flow encapsulation, which contains all information needed by 791 DetNet nodes (e.g., Real-time Transport Protocol (RTP) [RFC3550] 792 based DetNet flow transported over a native UDP/IP network or 793 PseudoWire). In other scenarios, the encapsulation formats might 794 differ significantly. As an example, a CPRI "application's" I/Q data 795 mapped directly to Ethernet frames may have to be transported over an 796 MPLS-based packet switched network (PSN). 798 There are many valid options to create a data plane solution for 799 DetNet traffic by selecting a technology approach for the DetNet 800 service layer and also selecting a technology approach for the DetNet 801 transport layer. There are a high number of valid combinations. 803 One of the most fundamental differences between different potential 804 data plane options is the basic addressing and headers used by DetNet 805 end systems. For example, is the basic service a Layer 2 (e.g., 806 Ethernet) or Layer 3 (i.e., IP) service. This decision impacts how 807 DetNet end systems are addressed, and the basic forwarding logic for 808 the DetNet service layer. 810 4.1.3. Network reference model 812 The figure below shows another view of the DetNet service related 813 reference points and main components (Figure 5). 815 DetNet DetNet 816 end system end system 817 _ _ 818 / \ +----DetNet-UNI (U) / \ 819 /App\ | /App\ 820 /-----\ | /-----\ 821 | NIC | v ________ | NIC | 822 +--+--+ _____ / \ DetNet-UNI (U) --+ +--+--+ 823 | / \__/ \ | | 824 | / +----+ +----+ \_____ | | 825 | / | | | | \_______ | | 826 +------U PE +----+ P +----+ \ _ v | 827 | | | | | | | ___/ \ | 828 | +--+-+ +----+ | +----+ | / \_ | 829 \ | | | | | / \ | 830 \ | +----+ +--+-+ +--+PE |-------- U------+ 831 \ | | | | | | | | | \_ _/ 832 \ +---+ P +----+ P +--+ +----+ | \____/ 833 \___ | | | | / 834 \ +----+__ +----+ DetNet-1 DetNet-2 835 | \_____/ \___________/ | 836 | | 837 | | End-to-End-Service | | | | 838 <----------------------------------------------------------------> 839 | | DetNet-Service | | | | 840 | <--------------------------------------------------> | 841 | | | | | | 843 Figure 5: DetNet Service Reference Model (multi-domain) 845 DetNet-UNIs ("U" in Figure 5) are assumed in this document to be 846 packet-based reference points and provide connectivity over the 847 packet network. A DetNet-UNI may provide multiple functions, e.g., 848 it may add networking technology specific encapsulation to the DetNet 849 flows if necessary; it may provide status of the availability of the 850 connection associated to a reservation; it may provide a 851 synchronization service for the end system; it may carry enough 852 signaling to place the reservation in a network without a controller, 853 or if the controller only deals with the network but not the end 854 points. Internal reference points of end systems (between the 855 application and the NIC) are more challenging from control 856 perspective and they may have extra requirements (e.g., in-order 857 delivery is expected in end system internal reference points, whereas 858 it is considered optional over the DetNet-UNI), therefore not covered 859 in this document. 861 4.2. DetNet systems 863 4.2.1. End system 865 The native data flow between the source/destination end systems is 866 referred to as application-flow (App-flow). The traffic 867 characteristics of an App-flow can be CBR (constant bit rate) or VBR 868 (variable bit rate) and can have L1 or L2 or L3 encapsulation (e.g., 869 TDM (time-division multiplexing), Ethernet, IP). These 870 characteristics are considered as input for resource reservation and 871 might be simplified to ensure determinism during transport (e.g., 872 making reservations for the peak rate of VBR traffic, etc.). 874 An end system may or may not be DetNet transport layer aware or 875 DetNet service layer aware. That is, an end system may or may not 876 contain DetNet specific functionality. End systems with DetNet 877 functionalities may have the same or different transport layer as the 878 connected DetNet domain. Grouping of end systems are shown in 879 Figure 6. 881 End system 882 | 883 | 884 | DetNet aware ? 885 / \ 886 +------< >------+ 887 NO | \ / | YES 888 | v | 889 DetNet unaware | 890 End system | 891 | Service/ 892 | Transport 893 / \ aware ? 894 +--------< >-------------+ 895 t-aware | \ / | s-aware 896 | v | 897 | | both | 898 | | | 899 DetNet t-aware | DetNet s-aware 900 End system | End system 901 v 902 DetNet st-aware 903 End system 905 Figure 6: Grouping of end systems 907 Note some known use cases for end systems: 909 o DetNet unaware: The classic case requiring network proxies. 911 o DetNet t-aware: An extant TSN system. It knows about some TSN 912 functions (e.g., reservation), but not about replication/ 913 elimination. 915 o DetNet s-aware: An extant IEC 62439-3 system. It supplies 916 sequence numbers, but doesn't know about zero congestion loss. 918 o DetNet st-aware: A full functioning DetNet end station, it has 919 DetNet functionalities and usually the same forwarding paradigm as 920 the connected DetNet domain. It can be treated as an integral 921 part of the DetNet domain . 923 4.2.2. DetNet edge, relay, and transit nodes 925 As shown in Figure 3, DetNet edge nodes providing proxy service and 926 DetNet relay nodes providing the DetNet service layer are DetNet- 927 aware, and DetNet transit nodes need only be aware of the DetNet 928 transport layer. 930 In general, if a DetNet flow passes through one or more DetNet- 931 unaware network node between two DetNet nodes providing the DetNet 932 transport layer for that flow, there is a potential for disruption or 933 failure of the DetNet QoS. A network administrator needs to ensure 934 that the DetNet-unaware network nodes are configured to minimize the 935 chances of packet loss and delay, and provision enough exra buffer 936 space in the DetNet transit node following the DetNet-unaware network 937 nodes to absorb the induced latency variations. 939 4.3. DetNet flows 941 4.3.1. DetNet flow types 943 A DetNet flow can have different formats during while it is 944 transported between the peer end systems. Therefore, the following 945 possible types / formats of a DetNet flow are distinguished in this 946 document: 948 o App-flow: native format of a DetNet flow. It does not contain any 949 DetNet related attributes. 951 o DetNet-t-flow: specific format of a DetNet flow. Only requires 952 the congestion / latency features provided by the Detnet transport 953 layer. 955 o DetNet-s-flow: specific format of a DetNet flow. Only requires 956 the replication/elimination feature ensured by the DetNet service 957 layer. 959 o DetNet-st-flow: specific format of a DetNet flow. It requires 960 both DetNet service layer and DetNet transport layer functions 961 during forwarding. 963 4.3.2. Source guarantees 965 For the purposes of congestion protection, DetNet flows can be 966 synchronous or asynchronous. In synchronous DetNet flows, at least 967 the intermediate nodes (and possibly the end systems) are closely 968 time synchronized, typically to better than 1 microsecond. By 969 transmitting packets from different DetNet flows or classes of DetNet 970 flows at different times, using repeating schedules synchronized 971 among the intermediate nodes, resources such as buffers and link 972 bandwidth can be shared over the time domain among different DetNet 973 flows. There is a tradeoff among techniques for synchronous DetNet 974 flows between the burden of fine-grained scheduling and the benefit 975 of reducing the required resources, especially buffer space. 977 In contrast, asynchronous DetNet flows are not coordinated with a 978 fine-grained schedule, so relay and end systems must assume worst- 979 case interference among DetNet flows contending for buffer resources. 980 Asynchronous DetNet flows are characterized by: 982 o A maximum packet size; 984 o An observation interval; and 986 o A maximum number of transmissions during that observation 987 interval. 989 These parameters, together with knowledge of the protocol stack used 990 (and thus the size of the various headers added to a packet), limit 991 the number of bit times per observation interval that the DetNet flow 992 can occupy the physical medium. 994 The source promises that these limits will not be exceeded. If the 995 source transmits less data than this limit allows, the unused 996 resources such as link bandwidth can be made available by the system 997 to non-DetNet packets. However, making those resources available to 998 DetNet packets in other DetNet flows would serve no purpose. Those 999 other DetNet flows have their own dedicated resources, on the 1000 assumption that all DetNet flows can use all of their resources over 1001 a long period of time. 1003 There is no provision in DetNet for throttling DetNet flows (reducing 1004 the transmission rate via feedback); the assumption is that a DetNet 1005 flow, to be useful, must be delivered in its entirety. That is, 1006 while any useful application is written to expect a certain number of 1007 lost packets, the real-time applications of interest to DetNet demand 1008 that the loss of data due to the network is extraordinarily 1009 infrequent. 1011 Although DetNet strives to minimize the changes required of an 1012 application to allow it to shift from a special-purpose digital 1013 network to an Internet Protocol network, one fundamental shift in the 1014 behavior of network applications is impossible to avoid: the 1015 reservation of resources before the application starts. In the first 1016 place, a network cannot deliver finite latency and practically zero 1017 packet loss to an arbitrarily high offered load. Secondly, achieving 1018 practically zero packet loss for unthrottled (though bandwidth 1019 limited) DetNet flows means that bridges and routers have to dedicate 1020 buffer resources to specific DetNet flows or to classes of DetNet 1021 flows. The requirements of each reservation have to be translated 1022 into the parameters that control each system's queuing, shaping, and 1023 scheduling functions and delivered to the hosts, bridges, and 1024 routers. 1026 4.3.3. Incomplete Networks 1028 The presence in the network of transit nodes or subnets that are not 1029 fully capable of offering DetNet services complicates the ability of 1030 the intermediate nodes and/or controller to allocate resources, as 1031 extra buffering, and thus extra latency, must be allocated at points 1032 downstream from the non-DetNet intermediate node for a DetNet flow. 1034 4.4. Traffic Engineering for DetNet 1036 Traffic Engineering Architecture and Signaling (TEAS) [TEAS] defines 1037 traffic-engineering architectures for generic applicability across 1038 packet and non-packet networks. From TEAS perspective, Traffic 1039 Engineering (TE) refers to techniques that enable operators to 1040 control how specific traffic flows are treated within their networks. 1042 Because if its very nature of establishing explicit optimized paths, 1043 Deterministic Networking can be seen as a new, specialized branch of 1044 Traffic Engineering, and inherits its architecture with a separation 1045 into planes. 1047 The Deterministic Networking architecture is thus composed of three 1048 planes, a (User) Application Plane, a Controller Plane, and a Network 1049 Plane, which echoes that of Figure 1 of Software-Defined Networking 1050 (SDN): Layers and Architecture Terminology [RFC7426].: 1052 4.4.1. The Application Plane 1054 Per [RFC7426], the Application Plane includes both applications and 1055 services. In particular, the Application Plane incorporates the User 1056 Agent, a specialized application that interacts with the end user / 1057 operator and performs requests for Deterministic Networking services 1058 via an abstract Flow Management Entity, (FME) which may or may not be 1059 collocated with (one of) the end systems. 1061 At the Application Plane, a management interface enables the 1062 negotiation of flows between end systems. An abstraction of the flow 1063 called a Traffic Specification (TSpec) provides the representation. 1064 This abstraction is used to place a reservation over the (Northbound) 1065 Service Interface and within the Application plane. It is associated 1066 with an abstraction of location, such as IP addresses and DNS names, 1067 to identify the end systems and eventually specify intermediate 1068 nodes. 1070 4.4.2. The Controller Plane 1072 The Controller Plane corresponds to the aggregation of the Control 1073 and Management Planes in [RFC7426], though Common Control and 1074 Measurement Plane (CCAMP) [CCAMP] makes an additional distinction 1075 between management and measurement. When the logical separation of 1076 the Control, Measurement and other Management entities is not 1077 relevant, the term Controller Plane is used for simplicity to 1078 represent them all, and the term controller refers to any device 1079 operating in that plane, whether is it a Path Computation entity or a 1080 Network Management entity (NME). The Path Computation Element (PCE) 1081 [PCE] is a core element of a controller, in charge of computing 1082 Deterministic paths to be applied in the Network Plane. 1084 A (Northbound) Service Interface enables applications in the 1085 Application Plane to communicate with the entities in the Controller 1086 Plane. 1088 One or more PCE(s) collaborate to implement the requests from the FME 1089 as Per-Flow Per-Hop Behaviors installed in the intermediate nodes for 1090 each individual flow. The PCEs place each flow along a deterministic 1091 sequence of intermediate nodes so as to respect per-flow constraints 1092 such as security and latency, and optimize the overall result for 1093 metrics such as an abstract aggregated cost. The deterministic 1094 sequence can typically be more complex than a direct sequence and 1095 include redundancy path, with one or more packet replication and 1096 elimination points. 1098 4.4.3. The Network Plane 1100 The Network Plane represents the network devices and protocols as a 1101 whole, regardless of the Layer at which the network devices operate. 1102 It includes Forwarding Plane (data plane), Application, and 1103 Operational Plane (control plane) aspects. 1105 The network Plane comprises the Network Interface Cards (NIC) in the 1106 end systems, which are typically IP hosts, and intermediate nodes, 1107 which are typically IP routers and switches. Network-to-Network 1108 Interfaces such as used for Traffic Engineering path reservation in 1109 [RFC5921], as well as User-to-Network Interfaces (UNI) such as 1110 provided by the Local Management Interface (LMI) between network and 1111 end systems, are both part of the Network Plane, both in the control 1112 plane and the data plane. 1114 A Southbound (Network) Interface enables the entities in the 1115 Controller Plane to communicate with devices in the Network Plane. 1116 This interface leverages and extends TEAS to describe the physical 1117 topology and resources in the Network Plane. 1119 Flow Management Entity 1121 End End 1122 System System 1124 -+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1126 PCE PCE PCE PCE 1128 -+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1130 intermediate intermed. intermed. intermed. 1131 Node Node Node Node 1132 NIC NIC 1133 intermediate intermed. intermed. intermed. 1134 Node Node Node Node 1136 Figure 7 1138 The intermediate nodes (and eventually the end systems NIC) expose 1139 their capabilities and physical resources to the controller (the 1140 PCE), and update the PCE with their dynamic perception of the 1141 topology, across the Southbound Interface. In return, the PCE(s) set 1142 the per-flow paths up, providing a Flow Characterization that is more 1143 tightly coupled to the intermediate node Operation than a TSpec. 1145 At the Network plane, intermediate nodes may exchange information 1146 regarding the state of the paths, between adjacent systems and 1147 eventually with the end systems, and forward packets within 1148 constraints associated to each flow, or, when unable to do so, 1149 perform a last resort operation such as drop or declassify. 1151 This specification focuses on the Southbound interface and the 1152 operation of the Network Plane. 1154 4.5. Queuing, Shaping, Scheduling, and Preemption 1156 DetNet achieves congestion protection and bounded delivery latency by 1157 reserving bandwidth and buffer resources at every hop along the path 1158 of the DetNet flow. The reservation itself is not sufficient, 1159 however. Implementors and users of a number of proprietary and 1160 standard real-time networks have found that standards for specific 1161 data plane techniques are required to enable these assurances to be 1162 made in a multi-vendor network. The fundamental reason is that 1163 latency variation in one system results in the need for extra buffer 1164 space in the next-hop system(s), which in turn, increases the worst- 1165 case per-hop latency. 1167 Standard queuing and transmission selection algorithms allow a 1168 central controller to compute the latency contribution of each 1169 transit node to the end-to-end latency, to compute the amount of 1170 buffer space required in each transit node for each incremental 1171 DetNet flow, and most importantly, to translate from a flow 1172 specification to a set of values for the managed objects that control 1173 each relay or end system. The IEEE 802 has specified (and is 1174 specifying) a set of queuing, shaping, and scheduling algorithms that 1175 enable each transit node (bridge or router), and/or a central 1176 controller, to compute these values. These algorithms include: 1178 o A credit-based shaper [IEEE802.1Q-2014] Clause 34. 1180 o Time-gated queues governed by a rotating time schedule, 1181 synchronized among all transit nodes [IEEE802.1Qbv]. 1183 o Synchronized double (or triple) buffers driven by synchronized 1184 time ticks. [IEEE802.1Qch]. 1186 o Pre-emption of an Ethernet packet in transmission by a packet with 1187 a more stringent latency requirement, followed by the resumption 1188 of the preempted packet [IEEE802.1Qbu], [IEEE802.3br]. 1190 While these techniques are currently embedded in Ethernet and 1191 bridging standards, we can note that they are all, except perhaps for 1192 packet preemption, equally applicable to other media than Ethernet, 1193 and to routers as well as bridges. 1195 4.6. Service instance 1197 A Service instance represents all the functions required on a node to 1198 allow the end-to-end service between the UNIs. 1200 The DetNet network reference model is shown in Figure 8 for a DetNet- 1201 Service scenario (i.e. between two DetNet-UNIs). In this figure, the 1202 end systems ("A" and "B") are connected directly to the edge nodes of 1203 the IP/MPLS network ("PE1" and "PE2"). End-systems participating 1204 DetNet communication may require connectivity before setting up an 1205 App-flow that requires the DetNet service. Such a connectivity 1206 related service instance and the one dedicated for DetNet service 1207 share the same access. Packets belonging to a DetNet flow are 1208 selected by a filter configured on the access ("F1" and "F2"). As a 1209 result, data flow specific access ("access-A + F1" and "access-B + 1210 F2") are terminated in the flow specific service instance ("SI-1" and 1211 "SI-2"). A tunnel is used to provide connectivity between the 1212 service instances. 1214 The tunnel is used to transport exclusively the packets of the DetNet 1215 flow between "SI-1" and "SI-2". The service instances are configured 1216 to implement DetNet functions and a flow specific routing or bridging 1217 function depending on what connectivity the participating end systems 1218 require (L3 or L2). The service instance and the tunnel may or may 1219 not be shared by multiple DetNet flows. Sharing the service instance 1220 by multiple DetNet flows requires properly populated forwarding 1221 tables of the service instance. 1223 access-A access-B 1224 <-----> <---------- tunnel ----------> <-----> 1226 +---------+ ___ _ +---------+ 1227 End system | +----+ | / \/ \_ | +----+ | End system 1228 "A" -------F1+ | | / \ | | +F2----- "B" 1229 | | +==========+ IP/MPLS +========+ | | 1230 | |SI-1| | \__ Net._/ | |SI-2| | 1231 | +----+ | \____/ | +----+ | 1232 |PE1 | | PE2| 1233 +---------+ +---------+ 1235 Figure 8: DetNet network reference model 1237 The tunnel between the service instances may have some special 1238 characteristics. For example, in case of a "packet PW" based tunnel, 1239 there are differences in the usage of the packet PW for DetNet 1240 traffic compared to the network model described in [RFC6658]. In the 1241 DetNet scenario, the packet PW is used exclusively by the DetNet 1242 flow, whereas [RFC6658] states: "The packet PW appears as a single 1243 point-to-point link to the client layer. Network-layer adjacency 1244 formation and maintenance between the client equipments will follow 1245 the normal practice needed to support the required relationship in 1246 the client layer ... This packet pseudowire is used to transport all 1247 of the required layer 2 and layer 3 protocols between LSR1 and LSR2". 1249 4.7. Flow identification at technology borders 1251 4.7.1. Exporting flow identification 1253 An interesting feature of DetNet, and one that invites 1254 implementations that can be accused of "layering violations", is the 1255 need for lower layers to be aware of specific flows at higher layers, 1256 in order to provide specific queuing and shaping services for 1257 specific flows. For example: 1259 o A non-IP, strictly L2 source end system X may be sending multiple 1260 flows to the same L2 destination end system Y. Those flows may 1261 include DetNet flows with different QoS requirements, and may 1262 include non-DetNet flows. 1264 o A router may be sending any number of flows to another router. 1265 Again, those flows may include DetNet flows with different QoS 1266 requirements, and may include non-DetNet flows. 1268 o Two routers may be separated by bridges. For these bridges to 1269 perform any required per-flow queuing and shaping, they must be 1270 able to identify the individual flows. 1272 o A Label Edge Router (LERs) may have a Label Switched Path (LSP) 1273 set up for handling traffic destined for a particular IP address 1274 carrying only non-DetNet flows. If a DetNet flow to that same 1275 address is requested, a separate LSP may be needed, in order that 1276 all of the Label Switch Routers (LSRs) along the path to the 1277 destination give that flow special queuing and shaping. 1279 The need for a lower-level DetNet node to be aware of individual 1280 higher-layer flows is not unique to DetNet. But, given the endless 1281 complexity of layering and relayering over tunnels that is available 1282 to network designers, DetNet needs to provide a model for flow 1283 identification that is at least somewhat better than packet 1284 inspection. That is not to say that packet inspection to layer 4 or 1285 5 addresses will not be used, or the capability standardized; but, 1286 there are alternatives. 1288 A DetNet relay node can connect DetNet flows on different paths using 1289 different flow identification methods. For example: 1291 o A single unicast DetNet flow passing from router A through a 1292 bridged network to router B may be assigned a {VLAN, multicast 1293 destination MAC address} pair that is unique within that bridged 1294 network. The bridges can then identify the flow without accessing 1295 higher-layer headers. Of course, the receiving router must 1296 recognize and accept that multicast MAC address. 1298 o A DetNet flow passing from LSR A to LSR B may be assigned a 1299 different label than that used for other flows to the same IP 1300 destination. 1302 In any of the above cases, it is possible that an existing DetNet 1303 flow can be used as a carrier for multiple DetNet sub-flows. (Not to 1304 be confused with DetNet compound vs. member flows.) Of course, this 1305 requires that the aggregate DetNet flow be provisioned properly to 1306 carry the sub-flows. 1308 Thus, rather than packet inspection, there is the option to export 1309 higher-layer information to the lower layer. The requirement to 1310 support one or the other method for flow identification (or both) is 1311 the essential complexity that DetNet brings to existing control plane 1312 models. 1314 4.7.2. Flow attribute mapping between layers 1316 Transport of DetNet flows over multiple technology domains may 1317 require that lower layers are aware of specific flows of higher 1318 layers. Such an "exporting of flow identification" is needed each 1319 time when the forwarding paradigm is changed on the transport path 1320 (e.g., two LSRs are interconnected by a L2 bridged domain, etc.). 1321 The three main forwarding methods considered for deterministic 1322 networking are: 1324 o IP routing 1326 o MPLS label switching 1328 o Ethernet bridging 1330 add/remove add/remove 1331 Eth Flow-ID IP Flow-ID 1332 | | 1333 v v 1334 +-----------------------------------------------------------+ 1335 | | | | | 1336 | Eth | MPLS | IP | Application data | 1337 | | | | | 1338 +-----------------------------------------------------------+ 1339 ^ 1340 | 1341 add/remove 1342 MPLS Flow-ID 1344 Figure 9: Packet with multiple Flow-IDs 1346 The additional (domain specific) Flow-ID can be 1348 o created by a domain specific function or 1350 o derived from the Flow-ID added to the App-flow, 1352 so that it must be unique inside the given domain. Note that the 1353 Flow-ID added to the App-flow is still present in the packet, but 1354 transport nodes may lack the function to recognize it; that's why the 1355 additional Flow-ID is added (pushed). 1357 4.7.3. Flow-ID mapping examples 1359 IP nodes and MPLS nodes are assumed to be configured to push such an 1360 additional (domain specific) Flow-ID when sending traffic to an 1361 Ethernet switch (as shown in the examples below). 1363 Figure 10 shows a scenario where an IP end system ("IP-A") is 1364 connected via two Ethernet switches ("ETH-n") to an IP router ("IP- 1365 1"). 1367 IP domain 1368 <----------------------------------------------- 1370 +======+ +======+ 1371 |L3-ID | |L3-ID | 1372 +======+ /\ +-----+ +======+ 1373 / \ Forward as | | 1374 /IP-A\ per ETH-ID |IP-1 | Recognize 1375 Push ------> +-+----+ | +---+-+ <----- ETH-ID 1376 ETH-ID | +----+-----+ | 1377 | v v | 1378 | +-----+ +-----+ | 1379 +------+ | | +---------+ 1380 +......+ |ETH-1+----+ETH-2| +======+ 1381 .L3-ID . +-----+ +-----+ |L3-ID | 1382 +======+ +......+ +======+ 1383 |ETH-ID| .L3-ID . |ETH-ID| 1384 +======+ +======+ +------+ 1385 |ETH-ID| 1386 +======+ 1388 Ethernet domain 1389 <----------------> 1391 Figure 10: IP nodes interconnected by an Ethernet domain 1393 End system "IP-A" uses the original App-flow specific ID ("L3-ID"), 1394 but as it is connected to an Ethernet domain it has to push an 1395 Ethernet-domain specific flow-ID ("VID + multicast MAC address", 1396 referred as "ETH-ID") before sending the packet to "ETH-1" node. 1397 Ethernet switch "ETH-1" can recognize the data flow based on the 1398 "ETH-ID" and it does forwarding toward "ETH-2". "ETH-2" switches the 1399 packet toward the IP router. "IP-1" must be configured to receive 1400 the Ethernet Flow-ID specific multicast stream, but (as it is an L3 1401 node) it decodes the data flow ID based on the "L3-ID" fields of the 1402 received packet. 1404 Figure 11 shows a scenario where MPLS domain nodes ("PE-n" and "P-m") 1405 are connected via two Ethernet switches ("ETH-n"). 1407 MPLS domain 1408 <-----------------------------------------------> 1410 +=======+ +=======+ 1411 |MPLS-ID| |MPLS-ID| 1412 +=======+ +-----+ +-----+ +=======+ +-----+ 1413 | | Forward as | | | | 1414 |PE-1 | per ETH-ID | P-2 +-----------+ PE-2| 1415 Push -----> +-+---+ | +---+-+ +-----+ 1416 ETH-ID | +-----+----+ | \ Recognize 1417 | v v | +-- ETH-ID 1418 | +-----+ +-----+ | 1419 +---+ | | +----+ 1420 +.......+ |ETH-1+----+ETH-2| +=======+ 1421 .MPLS-ID. +-----+ +-----+ |MPLS-ID| 1422 +=======+ +=======+ 1423 |ETH-ID | +.......+ |ETH-ID | 1424 +=======+ .MPLS-ID. +-------+ 1425 +=======+ 1426 |ETH-ID | 1427 +=======+ 1428 Ethernet domain 1429 <----------------> 1431 Figure 11: MPLS nodes interconnected by an Ethernet domain 1433 "PE-1" uses the MPLS specific ID ("MPLS-ID"), but as it is connected 1434 to an Ethernet domain it has to push an Ethernet-domain specific 1435 flow-ID ("VID + multicast MAC address", referred as "ETH-ID") before 1436 sending the packet to "ETH-1". Ethernet switch "ETH-1" can recognize 1437 the data flow based on the "ETH-ID" and it does forwarding toward 1438 "ETH-2". "ETH-2" switches the packet toward the MPLS node ("P-2"). 1439 "P-2" must be configured to receive the Ethernet Flow-ID specific 1440 multicast stream, but (as it is an MPLS node) it decodes the data 1441 flow ID based on the "MPLS-ID" fields of the received packet. 1443 One can appreciate from the above example that, when the means used 1444 for DetNet flow identifcation is altered or exported, the means for 1445 encoding the sequence number information must similarly be altered or 1446 exported. 1448 4.8. Advertising resources, capabilities and adjacencies 1450 There are three classes of information that a central controller or 1451 decentralized control plane needs to know that can only be obtained 1452 from the end systems and/or transit nodes in the network. When using 1453 a peer-to-peer control plane, some of this information may be 1454 required by a system's neighbors in the network. 1456 o Details of the system's capabilities that are required in order to 1457 accurately allocate that system's resources, as well as other 1458 systems' resources. This includes, for example, which specific 1459 queuing and shaping algorithms are implemented (Section 4.5), the 1460 number of buffers dedicated for DetNet allocation, and the worst- 1461 case forwarding delay. 1463 o The dynamic state of an end or transit node's DetNet resources. 1465 o The identity of the system's neighbors, and the characteristics of 1466 the link(s) between the systems, including the length (in 1467 nanoseconds) of the link(s). 1469 4.9. Provisioning model 1471 4.9.1. Centralized Path Computation and Installation 1473 A centralized routing model, such as provided with a PCE (RFC 4655 1474 [RFC4655]), enables global and per-flow optimizations. (See 1475 Section 4.4.) The model is attractive but a number of issues are 1476 left to be solved. In particular: 1478 o Whether and how the path computation can be installed by 1) an end 1479 device or 2) a Network Management entity, 1481 o And how the path is set up, either by installing state at each hop 1482 with a direct interaction between the forwarding device and the 1483 PCE, or along a path by injecting a source-routed request at one 1484 end of the path. 1486 4.9.2. Distributed Path Setup 1488 Significant work on distributed path setup can be leveraged from MPLS 1489 Traffic Engineering, in both its GMPLS and non-GMPLS forms. The 1490 protocols within scope are Resource ReSerVation Protocol [RFC3209] 1491 [RFC3473](RSVP-TE), OSPF-TE [RFC4203] [RFC5392] and ISIS-TE [RFC5307] 1492 [RFC5316]. These should be viewed as starting points as there are 1493 feature specific extensions defined that may be applicable to DetNet. 1495 In a Layer-2 only environment, or as part of a layered approach to a 1496 mixed environment, IEEE 802.1 also has work, either completed or in 1497 progress. [IEEE802.1Q-2014] Clause 35 describes SRP, a peer-to-peer 1498 protocol for Layer-2 roughly analogous to RSVP [RFC2205]. 1499 [IEEE802.1Qca] defines how ISIS can provide multiple disjoint paths 1500 or distribution trees. Also in progress is [IEEE802.1Qcc], which 1501 expands the capabilities of SRP. 1503 The integration/interaction of the DetNet control layer with an 1504 underlying IEEE 802.1 sub-network control layer will need to be 1505 defined. 1507 4.10. Scaling to larger networks 1509 Reservations for individual DetNet flows require considerable state 1510 information in each transit node, especially when adequate fault 1511 mitigation (Section 3.3.2) is required. The DetNet data plane, in 1512 order to support larger numbers of DetNet flows, must support the 1513 aggregation of DetNet flows into tunnels, which themselves can be 1514 viewed by the transit nodes' data planes largely as individual DetNet 1515 flows. Without such aggregation, the per-relay system may limit the 1516 scale of DetNet networks. 1518 4.11. Connected islands vs. networks 1520 Given that users have deployed examples of the IEEE 802.1 TSN TG 1521 standards, which provide capabilities similar to DetNet, it is 1522 obvious to ask whether the IETF DetNet effort can be limited to 1523 providing Layer-2 connections (VPNs) between islands of bridged TSN 1524 networks. While this capability is certainly useful to some 1525 applications, and must not be precluded by DetNet, tunneling alone is 1526 not a sufficient goal for the DetNet WG. As shown in the 1527 Deterministic Networking Use Cases draft [I-D.ietf-detnet-use-cases], 1528 there are already deployments of Layer-2 TSN networks that are 1529 encountering the well-known problems of over-large broadcast domains. 1530 Routed solutions, and combinations routed/bridged solutions, are both 1531 required. 1533 4.12. Compatibility with Layer-2 1535 Standards providing similar capabilities for bridged networks (only) 1536 have been and are being generated in the IEEE 802 LAN/MAN Standards 1537 Committee. The present architecture describes an abstract model that 1538 can be applicable both at Layer-2 and Layer-3, and over links not 1539 defined by IEEE 802. It is the intention of the authors (and 1540 hopefully, as this draft progresses, of the DetNet Working Group) 1541 that IETF and IEEE 802 will coordinate their work, via the 1542 participation of common individuals, liaisons, and other means, to 1543 maximize the compatibility of their outputs. 1545 DetNet enabled end systems and intermediate nodes can be 1546 interconnected by sub-networks, i.e., Layer-2 technologies. These 1547 sub-networks will provide DetNet compatible service for support of 1548 DetNet traffic. Examples of sub-networks include 802.1TSN and a 1549 point-to-point OTN link. Of course, multi-layer DetNet systems may 1550 be possible too, where one DetNet appears as a sub-network, and 1551 provides service to, a higher layer DetNet system. 1553 5. Security Considerations 1555 Security in the context of Deterministic Networking has an added 1556 dimension; the time of delivery of a packet can be just as important 1557 as the contents of the packet, itself. A man-in-the-middle attack, 1558 for example, can impose, and then systematically adjust, additional 1559 delays into a link, and thus disrupt or subvert a real-time 1560 application without having to crack any encryption methods employed. 1561 See [RFC7384] for an exploration of this issue in a related context. 1563 Furthermore, in a control system where millions of dollars of 1564 equipment, or even human lives, can be lost if the DetNet QoS is not 1565 delivered, one must consider not only simple equipment failures, 1566 where the box or wire instantly becomes perfectly silent, but bizarre 1567 errors such as can be caused by software failures. Because there is 1568 essential no limit to the kinds of failures that can occur, 1569 protecting against realistic equipment failures is indistinguishable, 1570 in most cases, from protecting against malicious behavior, whether 1571 accidental or intentional. See also Section 3.3.2. 1573 Security must cover: 1575 o the protection of the signaling protocol 1577 o the authentication and authorization of the controlling systems 1579 o the identification and shaping of the DetNet flows 1581 6. Privacy Considerations 1583 DetNet is provides a Quality of Service (QoS), and as such, does not 1584 directly raise any new privacy considerations. 1586 However, the requirement for every (or almost every) node along the 1587 path of a DetNet flow to identify DetNet flows may present an 1588 additional attack surface for privacy, should the DetNet paradigm be 1589 found useful in broader environments. 1591 7. IANA Considerations 1593 This document does not require an action from IANA. 1595 8. Acknowledgements 1597 The authors wish to thank Jouni Korhonen, Erik Nordmark, George 1598 Swallow, Rudy Klecka, Anca Zamfir, David Black, Thomas Watteyne, 1599 Shitanshu Shah, Craig Gunther, Rodney Cummings, Balazs Varga, 1600 Wilfried Steiner, Marcel Kiessling, Karl Weber, Janos Farkas, Ethan 1601 Grossman, Pat Thaler, Lou Berger, and especially Michael Johas 1602 Teener, for their various contribution with this work. 1604 9. Access to IEEE 802.1 documents 1606 To access password protected IEEE 802.1 drafts, see the IETF IEEE 1607 802.1 information page at https://www.ietf.org/proceedings/52/slides/ 1608 bridge-0/tsld003.htm. 1610 10. Informative References 1612 [AVnu] http://www.avnu.org/, "The AVnu Alliance tests and 1613 certifies devices for interoperability, providing a simple 1614 and reliable networking solution for AV network 1615 implementation based on the Audio Video Bridging (AVB) 1616 standards.". 1618 [CCAMP] IETF, "Common Control and Measurement Plane", 1619 . 1621 [HSR-PRP] IEC, "High availability seamless redundancy (HSR) is a 1622 further development of the PRP approach, although HSR 1623 functions primarily as a protocol for creating media 1624 redundancy while PRP, as described in the previous 1625 section, creates network redundancy. PRP and HSR are both 1626 described in the IEC 62439 3 standard.", 1627 . 1630 [I-D.dt-detnet-dp-alt] 1631 Korhonen, J., Farkas, J., Mirsky, G., Thubert, P., 1632 Zhuangyan, Z., and L. Berger, "DetNet Data Plane Protocol 1633 and Solution Alternatives", draft-dt-detnet-dp-alt-04 1634 (work in progress), September 2016. 1636 [I-D.ietf-6tisch-architecture] 1637 Thubert, P., "An Architecture for IPv6 over the TSCH mode 1638 of IEEE 802.15.4", draft-ietf-6tisch-architecture-12 (work 1639 in progress), August 2017. 1641 [I-D.ietf-6tisch-tsch] 1642 Watteyne, T., Palattella, M., and L. Grieco, "Using 1643 IEEE802.15.4e TSCH in an IoT context: Overview, Problem 1644 Statement and Goals", draft-ietf-6tisch-tsch-06 (work in 1645 progress), March 2015. 1647 [I-D.ietf-detnet-problem-statement] 1648 Finn, N. and P. Thubert, "Deterministic Networking Problem 1649 Statement", draft-ietf-detnet-problem-statement-02 (work 1650 in progress), September 2017. 1652 [I-D.ietf-detnet-use-cases] 1653 Grossman, E., Gunther, C., Thubert, P., Wetterwald, P., 1654 Raymond, J., Korhonen, J., Kaneko, Y., Das, S., Zha, Y., 1655 Varga, B., Farkas, J., Goetz, F., Schmitt, J., Vilajosana, 1656 X., Mahmoodi, T., Spirou, S., Vizarreta, P., Huang, D., 1657 Geng, X., Dujovne, D., and M. Seewald, "Deterministic 1658 Networking Use Cases", draft-ietf-detnet-use-cases-13 1659 (work in progress), September 2017. 1661 [I-D.ietf-roll-rpl-industrial-applicability] 1662 Phinney, T., Thubert, P., and R. Assimiti, "RPL 1663 applicability in industrial networks", draft-ietf-roll- 1664 rpl-industrial-applicability-02 (work in progress), 1665 October 2013. 1667 [I-D.svshah-tsvwg-deterministic-forwarding] 1668 Shah, S. and P. Thubert, "Deterministic Forwarding PHB", 1669 draft-svshah-tsvwg-deterministic-forwarding-04 (work in 1670 progress), August 2015. 1672 [I-D.varga-detnet-service-model] 1673 Varga, B. and J. Farkas, "DetNet Service Model", draft- 1674 varga-detnet-service-model-02 (work in progress), May 1675 2017. 1677 [IEEE802.1AS-2011] 1678 IEEE, "IEEE Std 802.1AS Timing and Synchronization for 1679 Time-Sensitive Applications in Bridged Local Area 1680 Networks", 2011, 1681 . 1683 [IEEE802.1BA-2011] 1684 IEEE, "IEEE Std 802.1BA Audio Video Bridging (AVB) 1685 Systems", 2011, 1686 . 1688 [IEEE802.1CB] 1689 IEEE, "Frame Replication and Elimination for Reliability 1690 (IEEE Draft P802.1CB)", 2017, 1691 . 1693 [IEEE802.1Q-2014] 1694 IEEE, "IEEE Std 802.1Q Bridges and Bridged Networks", 1695 2014, . 1697 [IEEE802.1Qbu] 1698 IEEE, "IEEEE Std 802.1Qbu Bridges and Bridged Networks - 1699 Amendment 26: Frame Preemption", 2016, 1700 . 1702 [IEEE802.1Qbv] 1703 IEEE, "IEEEE Std 802.1Qbu Bridges and Bridged Networks - 1704 Amendment 25: Enhancements for Scheduled Traffic", 2015, 1705 . 1707 [IEEE802.1Qca] 1708 IEEE, "IEEE Std 802.1Qca Bridges and Bridged Networks - 1709 Amendment 24: Path Control and Reservation", June 2015, 1710 . 1712 [IEEE802.1Qcc] 1713 IEEE, "Stream Reservation Protocol (SRP) Enhancements and 1714 Performance Improvements (IEEE Draft P802.1Qcc)", 2017, 1715 . 1717 [IEEE802.1Qch] 1718 IEEE, "Cyclic Queuing and Forwarding (IEEE Draft 1719 P802.1Qch)", 2017, 1720 . 1722 [IEEE802.1TSNTG] 1723 IEEE Standards Association, "IEEE 802.1 Time-Sensitive 1724 Networks Task Group", 2013, 1725 . 1727 [IEEE802.3-2015] 1728 IEEE, "IEEE Std 802.3 Standard for Ethernet", 2015, 1729 . 1731 [IEEE802.3br] 1732 IEEE, "IEEE Std 802.3br Standard for Ethernet Amendment 5: 1733 Specification and Management Parameters for Interspersing 1734 Express Traffic", 2016, 1735 . 1737 [ISA95] ANSI/ISA, "Enterprise-Control System Integration Part 1: 1738 Models and Terminology", 2000, 1739 . 1741 [ODVA] http://www.odva.org/, "The organization that supports 1742 network technologies built on the Common Industrial 1743 Protocol (CIP) including EtherNet/IP.". 1745 [PCE] IETF, "Path Computation Element", 1746 . 1748 [Profinet] 1749 http://us.profinet.com/technology/profinet/, "PROFINET is 1750 a standard for industrial networking in automation.", 1751 . 1753 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. 1754 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 1755 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, 1756 September 1997, . 1758 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 1759 and W. Weiss, "An Architecture for Differentiated 1760 Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, 1761 . 1763 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 1764 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 1765 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 1766 . 1768 [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label 1769 Switching (GMPLS) Signaling Resource ReserVation Protocol- 1770 Traffic Engineering (RSVP-TE) Extensions", RFC 3473, 1771 DOI 10.17487/RFC3473, January 2003, 1772 . 1774 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 1775 Jacobson, "RTP: A Transport Protocol for Real-Time 1776 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 1777 July 2003, . 1779 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 1780 Support of Generalized Multi-Protocol Label Switching 1781 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 1782 . 1784 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1785 Element (PCE)-Based Architecture", RFC 4655, 1786 DOI 10.17487/RFC4655, August 2006, 1787 . 1789 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 1790 in Support of Generalized Multi-Protocol Label Switching 1791 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 1792 . 1794 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 1795 Support of Inter-Autonomous System (AS) MPLS and GMPLS 1796 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 1797 December 2008, . 1799 [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in 1800 Support of Inter-Autonomous System (AS) MPLS and GMPLS 1801 Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392, 1802 January 2009, . 1804 [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. 1805 Phinney, "Industrial Routing Requirements in Low-Power and 1806 Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October 1807 2009, . 1809 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 1810 L., and L. Berger, "A Framework for MPLS in Transport 1811 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 1812 . 1814 [RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport 1815 Profile (MPLS-TP) Survivability Framework", RFC 6372, 1816 DOI 10.17487/RFC6372, September 2011, 1817 . 1819 [RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis, 1820 "Packet Pseudowire Encapsulation over an MPLS PSN", 1821 RFC 6658, DOI 10.17487/RFC6658, July 2012, 1822 . 1824 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 1825 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 1826 October 2014, . 1828 [RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S., 1829 Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software- 1830 Defined Networking (SDN): Layers and Architecture 1831 Terminology", RFC 7426, DOI 10.17487/RFC7426, January 1832 2015, . 1834 [TEAS] IETF, "Traffic Engineering Architecture and Signaling", 1835 . 1837 Authors' Addresses 1839 Norman Finn 1840 Huawei Technologies Co. Ltd 1841 3755 Avocado Blvd. 1842 PMB 436 1843 La Mesa, California 91941 1844 US 1846 Phone: +1 925 980 6430 1847 Email: norman.finn@mail01.huawei.com 1849 Pascal Thubert 1850 Cisco Systems 1851 Village d'Entreprises Green Side 1852 400, Avenue de Roumanille 1853 Batiment T3 1854 Biot - Sophia Antipolis 06410 1855 FRANCE 1857 Phone: +33 4 97 23 26 34 1858 Email: pthubert@cisco.com 1860 Balazs Varga 1861 Ericsson 1862 Konyves Kalman krt. 11/B 1863 Budapest 1097 1864 Hungary 1866 Email: balazs.a.varga@ericsson.com 1867 Janos Farkas 1868 Ericsson 1869 Konyves Kalman krt. 11/B 1870 Budapest 1097 1871 Hungary 1873 Email: janos.farkas@ericsson.com