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2 DetNet N. Finn
3 Internet-Draft Huawei
4 Intended status: Standards Track P. Thubert
5 Expires: April 25, 2019 Cisco
6 B. Varga
7 J. Farkas
8 Ericsson
9 October 22, 2018
11 Deterministic Networking Architecture
12 draft-ietf-detnet-architecture-09
14 Abstract
16 This document provides the overall architecture for Deterministic
17 Networking (DetNet), which provides a capability to carry specified
18 unicast or multicast data flows for real-time applications with
19 extremely low data loss rates and bounded latency within a network
20 domain. Techniques used include: 1) reserving data plane resources
21 for individual (or aggregated) DetNet flows in some or all of the
22 intermediate nodes along the path of the flow; 2) providing explicit
23 routes for DetNet flows that do not immediately change with the
24 network topology; and 3) distributing data from DetNet flow packets
25 over time and/or space to ensure delivery of each packet's data in
26 spite of the loss of a path. DetNet operates at the IP layer and
27 delivers service over sub-network technologies such as MPLS and IEEE
28 802.1 Time-Sensitive Networking (TSN).
30 Status of This Memo
32 This Internet-Draft is submitted in full conformance with the
33 provisions of BCP 78 and BCP 79.
35 Internet-Drafts are working documents of the Internet Engineering
36 Task Force (IETF). Note that other groups may also distribute
37 working documents as Internet-Drafts. The list of current Internet-
38 Drafts is at https://datatracker.ietf.org/drafts/current/.
40 Internet-Drafts are draft documents valid for a maximum of six months
41 and may be updated, replaced, or obsoleted by other documents at any
42 time. It is inappropriate to use Internet-Drafts as reference
43 material or to cite them other than as "work in progress."
45 This Internet-Draft will expire on April 25, 2019.
47 Copyright Notice
49 Copyright (c) 2018 IETF Trust and the persons identified as the
50 document authors. All rights reserved.
52 This document is subject to BCP 78 and the IETF Trust's Legal
53 Provisions Relating to IETF Documents
54 (https://trustee.ietf.org/license-info) in effect on the date of
55 publication of this document. Please review these documents
56 carefully, as they describe your rights and restrictions with respect
57 to this document. Code Components extracted from this document must
58 include Simplified BSD License text as described in Section 4.e of
59 the Trust Legal Provisions and are provided without warranty as
60 described in the Simplified BSD License.
62 Table of Contents
64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
65 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
66 2.1. Terms used in this document . . . . . . . . . . . . . . . 4
67 2.2. IEEE 802.1 TSN to DetNet dictionary . . . . . . . . . . . 7
68 3. Providing the DetNet Quality of Service . . . . . . . . . . . 7
69 3.1. Primary goals defining the DetNet QoS . . . . . . . . . . 7
70 3.2. Mechanisms to achieve DetNet QoS . . . . . . . . . . . . 10
71 3.2.1. Congestion protection . . . . . . . . . . . . . . . . 10
72 3.2.1.1. Eliminate congestion loss . . . . . . . . . . . . 10
73 3.2.1.2. Jitter Reduction . . . . . . . . . . . . . . . . 10
74 3.2.2. Service Protection . . . . . . . . . . . . . . . . . 11
75 3.2.2.1. In-Order Delivery . . . . . . . . . . . . . . . . 11
76 3.2.2.2. Packet Replication and Elimination . . . . . . . 12
77 3.2.2.3. Packet encoding for service protection . . . . . 14
78 3.2.3. Explicit routes . . . . . . . . . . . . . . . . . . . 14
79 3.3. Secondary goals for DetNet . . . . . . . . . . . . . . . 15
80 3.3.1. Coexistence with normal traffic . . . . . . . . . . . 15
81 3.3.2. Fault Mitigation . . . . . . . . . . . . . . . . . . 15
82 4. DetNet Architecture . . . . . . . . . . . . . . . . . . . . . 16
83 4.1. DetNet stack model . . . . . . . . . . . . . . . . . . . 16
84 4.1.1. Representative Protocol Stack Model . . . . . . . . . 16
85 4.1.2. DetNet Data Plane Overview . . . . . . . . . . . . . 19
86 4.1.3. Network reference model . . . . . . . . . . . . . . . 21
87 4.2. DetNet systems . . . . . . . . . . . . . . . . . . . . . 22
88 4.2.1. End system . . . . . . . . . . . . . . . . . . . . . 22
89 4.2.2. DetNet edge, relay, and transit nodes . . . . . . . . 23
90 4.3. DetNet flows . . . . . . . . . . . . . . . . . . . . . . 24
91 4.3.1. DetNet flow types . . . . . . . . . . . . . . . . . . 24
92 4.3.2. Source transmission behavior . . . . . . . . . . . . 24
93 4.3.3. Incomplete Networks . . . . . . . . . . . . . . . . . 26
94 4.4. Traffic Engineering for DetNet . . . . . . . . . . . . . 26
95 4.4.1. The Application Plane . . . . . . . . . . . . . . . . 26
96 4.4.2. The Controller Plane . . . . . . . . . . . . . . . . 27
97 4.4.3. The Network Plane . . . . . . . . . . . . . . . . . . 27
98 4.5. Queuing, Shaping, Scheduling, and Preemption . . . . . . 28
99 4.6. Service instance . . . . . . . . . . . . . . . . . . . . 29
100 4.7. Flow identification at technology borders . . . . . . . . 31
101 4.7.1. Exporting flow identification . . . . . . . . . . . . 31
102 4.7.2. Flow attribute mapping between layers . . . . . . . . 32
103 4.7.3. Flow-ID mapping examples . . . . . . . . . . . . . . 33
104 4.8. Advertising resources, capabilities and adjacencies . . . 35
105 4.9. Scaling to larger networks . . . . . . . . . . . . . . . 36
106 4.10. Compatibility with Layer-2 . . . . . . . . . . . . . . . 36
107 5. Security Considerations . . . . . . . . . . . . . . . . . . . 36
108 6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 37
109 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
110 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 37
111 9. Informative References . . . . . . . . . . . . . . . . . . . 38
112 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
114 1. Introduction
116 This document provides the overall architecture for Deterministic
117 Networking (DetNet), which provides a capability for the delivery of
118 data flows with extremely low packet loss rates and bounded end-to-
119 end delivery latency. DetNet is for networks that are under a single
120 administrative control or within a closed group of administrative
121 control; these include campus-wide networks and private WANs. DetNet
122 is not for large groups of domains such as the Internet.
124 DetNet operates at the IP layer and delivers service over sub-network
125 technologies such as MPLS and IEEE 802.1 Time-Sensitive Networking
126 (TSN). DetNet accomplishes these goals by dedicating network
127 resources such as link bandwidth and buffer space to DetNet flows
128 and/or classes of DetNet flows, and by replicating packets along
129 multiple paths. Unused reserved resources are available to non-
130 DetNet packets as long as all guarantees are fulfilled.
132 The Deterministic Networking Problem Statement
133 [I-D.ietf-detnet-problem-statement] introduces Deterministic
134 Networking, and Deterministic Networking Use Cases
135 [I-D.ietf-detnet-use-cases] summarizes the need for it. See
136 [I-D.ietf-detnet-dp-sol-mpls] and [I-D.ietf-detnet-dp-sol-ip] for
137 specific techniques that can be used to identify DetNet flows and
138 assign them to specific paths through a network.
140 A goal of DetNet is a converged network in all respects. That is,
141 the presence of DetNet flows does not preclude non-DetNet flows, and
142 the benefits offered DetNet flows should not, except in extreme
143 cases, prevent existing Quality of Service (QoS) mechanisms from
144 operating in a normal fashion, subject to the bandwidth required for
145 the DetNet flows. A single source-destination pair can trade both
146 DetNet and non-DetNet flows. End systems and applications need not
147 instantiate special interfaces for DetNet flows. Networks are not
148 restricted to certain topologies; connectivity is not restricted.
149 Any application that generates a data flow that can be usefully
150 characterized as having a maximum bandwidth should be able to take
151 advantage of DetNet, as long as the necessary resources can be
152 reserved. Reservations can be made by the application itself, via
153 network management, by an application's controller, or by other
154 means, e.g., a dynamic control plane (e.g., [RFC2205]). Network
155 nodes supporting DetNet flows have to implement some of the DetNet
156 capabilities (not necessarily all) in order to treat DetNet flows
157 such that their QoS requirements are met.
159 Many applications that are intended to be served by Deterministic
160 Networking require the ability to synchronize the clocks in end
161 systems to a sub-microsecond accuracy. Some of the queue control
162 techniques defined in Section 4.5 also require time synchronization
163 among network nodes. The means used to achieve time synchronization
164 are not addressed in this document. DetNet can accommodate various
165 time synchronization techniques and profiles that are defined
166 elsewhere to address the needs of different market segments.
168 2. Terminology
170 2.1. Terms used in this document
172 The following terms are used in the context of DetNet in this
173 document:
175 allocation
176 Resources are dedicated to support a DetNet flow. Depending
177 on an implementation, the resource may be reused by non-
178 DetNet flows when it is not used by the DetNet flow.
180 App-flow
181 The native format of a DetNet flow.
183 DetNet compound flow and DetNet member flow
184 A DetNet compound flow is a DetNet flow that has been
185 separated into multiple duplicate DetNet member flows for
186 service protection at the DetNet service sub-layer. Member
187 flows are merged back into a single DetNet compound flow such
188 that there are no duplicate packets. "Compound" and "member"
189 are strictly relative to each other, not absolutes; a DetNet
190 compound flow comprising multiple DetNet member flows can, in
191 turn, be a member of a higher-order compound.
193 DetNet destination
194 An end system capable of terminating a DetNet flow.
196 DetNet domain
197 The portion of a network that is DetNet aware. It includes
198 end systems and DetNet nodes.
200 DetNet edge node
201 An instance of a DetNet relay node that acts as a source and/
202 or destination at the DetNet service sub-layer. For example,
203 it can include a DetNet service sub-layer proxy function for
204 DetNet service protection (e.g., the addition or removal of
205 packet sequencing information) for one or more end systems,
206 or starts or terminates congestion protection at the DetNet
207 transport sub-layer, or aggregates DetNet services into new
208 DetNet flows. It is analogous to a Label Edge Router (LER)
209 or a Provider Edge (PE) router.
211 DetNet flow
212 A DetNet flow is a sequence of packets from one source to one
213 or more destinations, which conform uniquely to a flow
214 identifier, and to which the DetNet service is to be
215 provided.
217 DetNet intermediate node
218 A DetNet relay node or DetNet transit node.
220 DetNet node
221 A DetNet edge node, a DetNet relay node, or a DetNet transit
222 node.
224 DetNet relay node
225 A DetNet node including a service sub-layer function that
226 interconnects different DetNet transport sub-layer paths to
227 provide service protection. A DetNet relay node participates
228 in the DetNet service sub-layer. It typically incorporates
229 DetNet transport sub-layer functions as well, in which case
230 it is collocated with a transit node.
232 DetNet service sub-layer
233 The DetNet sub-layer at which A DetNet service, e.g., service
234 protection is provided.
236 DetNet service proxy
237 Maps between App-flows and DetNet flows.
239 DetNet source
240 An end system capable of originating a DetNet flow.
242 DetNet system
243 A DetNet aware end system, transit node, or relay node.
244 "DetNet" may be omitted in some text.
246 DetNet transit node
247 A DetNet node operating at the DetNet transport sub-layer,
248 that utilizes link layer and/or network layer switching
249 across multiple links and/or sub-networks to provide paths
250 for DetNet service sub-layer functions. Typically provides
251 congestion protection over those paths. An MPLS LSR is an
252 example of a DetNet transit node.
254 DetNet transport sub-layer
255 The DetNet layer that optionally provides congestion
256 protection for DetNet flows over paths provided by the
257 underlying network.
259 DetNet-UNI
260 User-to-Network Interface with DetNet specific
261 functionalities. It is a packet-based reference point and
262 may provide multiple functions like encapsulation, status,
263 synchronization, etc.
265 end system
266 Commonly called a "host" in IETF documents, and an "end
267 station" is IEEE 802 documents. End systems of interest to
268 this document are either sources or destinations of DetNet
269 flows. And end system may or may not be DetNet transport
270 sub-layer aware or DetNet service sub-layer aware.
272 link
273 A connection between two DetNet nodes. It may be composed of
274 a physical link or a sub-network technology that can provide
275 appropriate traffic delivery for DetNet flows.
277 PEF A Packet Elimination Function (PEF) eliminates duplicate
278 copies of packets to prevent excess packets flooding the
279 network or duplicate packets being sent out of the DetNet
280 domain. PEF can be implemented by a DetNet edge node, a
281 DetNet relay node, or an end system.
283 PRF A Packet Replication Function (PRF) replicates DetNet flow
284 packets and forwards them to one or more next hops in the
285 DetNet domain. The number of packet copies sent to the next
286 hops is a DetNet flow specific parameter at the point of
287 replication. PRF can be implemented by a DetNet edge node, a
288 DetNet relay node, or an end system.
290 PREOF Collective name for Packet Replication, Elimination, and
291 Ordering Functions.
293 POF A Packet Ordering Function (POF) re-orders packets within a
294 DetNet flow that are received out of order. This function
295 can be implemented by a DetNet edge node, a DetNet relay
296 node, or an end system.
298 reservation
299 The set of resources allocated between a source and one or
300 more destinations through DetNet nodes and subnets associated
301 with a DetNet flow, to provide the provisioned DetNet
302 service.
304 2.2. IEEE 802.1 TSN to DetNet dictionary
306 This section also serves as a dictionary for translating from the
307 terms used by the Time-Sensitive Networking (TSN) Task Group
308 [IEEE802.1TSNTG] of the IEEE 802.1 WG to those of the DetNet WG.
310 Listener
311 The IEEE 802.1 term for a destination of a DetNet flow.
313 relay system
314 The IEEE 802.1 term for a DetNet intermediate node.
316 Stream
317 The IEEE 802.1 term for a DetNet flow.
319 Talker
320 The IEEE 802.1 term for the source of a DetNet flow.
322 3. Providing the DetNet Quality of Service
324 3.1. Primary goals defining the DetNet QoS
326 The DetNet Quality of Service can be expressed in terms of:
328 o Minimum and maximum end-to-end latency from source to destination;
329 timely delivery, and bounded jitter (packet delay variation)
330 derived from these constraints.
332 o Packet loss ratio, under various assumptions as to the operational
333 states of the nodes and links.
335 o An upper bound on out-of-order packet delivery. It is worth
336 noting that some DetNet applications are unable to tolerate any
337 out-of-order delivery.
339 It is a distinction of DetNet that it is concerned solely with worst-
340 case values for the end-to-end latency, jitter, and misordering.
341 Average, mean, or typical values are of little interest, because they
342 do not affect the ability of a real-time system to perform its tasks.
343 In general, a trivial priority-based queuing scheme will give better
344 average latency to a data flow than DetNet; however, it may not be a
345 suitable option for DetNet because of its worst-case latency.
347 Three techniques are used by DetNet to provide these qualities of
348 service:
350 o Congestion protection (Section 3.2.1).
352 o Service protection (Section 3.2.2).
354 o Explicit routes (Section 3.2.3).
356 Congestion protection operates by allocating resources along the path
357 of a DetNet flow, e.g., buffer space or link bandwidth. Congestion
358 protection greatly reduces, or even eliminates entirely, packet loss
359 due to output packet congestion within the network, but it can only
360 be supplied to a DetNet flow that is limited at the source to a
361 maximum packet size and transmission rate. Note that congestion
362 protection provided via congestion detection and notification is
363 explicitly excluded from consideration in DetNet, as it serves a
364 different set of applications.
366 Congestion protection addresses two of the DetNet QoS requirements:
367 latency and packet loss. Given that DetNet nodes have a finite
368 amount of buffer space, congestion protection necessarily results in
369 a maximum end-to-end latency. It also addresses the largest
370 contribution to packet loss, which is buffer congestion.
372 After congestion, the most important contributions to packet loss are
373 typically from random media errors and equipment failures. Service
374 protection is the name for the mechanisms used by DetNet to address
375 these losses. The mechanisms employed are constrained by the
376 requirement to meet the users' latency requirements. Packet
377 replication and elimination (Section 3.2.2) and packet encoding
378 (Section 3.2.2.3) are described in this document to provide service
379 protection; others may be found. For instance, packet encoding can
380 be used to provide service protection against random media errors,
381 packet replication and elimination can be used to provide service
382 protection against equipment failures. This mechanism distributes
383 the contents of DetNet flows over multiple paths in time and/or
384 space, so that the loss of some of the paths does need not cause the
385 loss of any packets.
387 The paths are typically (but not necessarily) explicit routes, so
388 that they do not normally suffer temporary interruptions caused by
389 the convergence of routing or bridging protocols.
391 These three techniques can be applied independently, giving eight
392 possible combinations, including none (no DetNet), although some
393 combinations are of wider utility than others. This separation keeps
394 the protocol stack coherent and maximizes interoperability with
395 existing and developing standards in this (IETF) and other Standards
396 Development Organizations. Some examples of typical expected
397 combinations:
399 o Explicit routes plus service protection are exactly the techniques
400 employed by seamless redundancy mechanisms applied on a ring
401 topology as described, e.g., in [IEC62439-3-2016]. In this
402 example, explicit routes are achieved by limiting the physical
403 topology of the network to a ring. Sequentialization,
404 replication, and duplicate elimination are facilitated by packet
405 tags added at the front or the end of Ethernet frames. [RFC8227]
406 provides another example in the context of MPLS.
408 o Congestion protection alone is offered by IEEE 802.1 Audio Video
409 bridging [IEEE802.1BA]. As long as the network suffers no
410 failures, zero congestion loss can be achieved through the use of
411 a reservation protocol (e.g., Multiple Stream Registration
412 Protocol [IEEE802.1Q-2018]), shapers in every bridge, and proper
413 dimensioning.
415 o Using all three together gives maximum protection.
417 There are, of course, simpler methods available (and employed, today)
418 to achieve levels of latency and packet loss that are satisfactory
419 for many applications. Prioritization and over-provisioning is one
420 such technique. However, these methods generally work best in the
421 absence of any significant amount of non-critical traffic in the
422 network (if, indeed, such traffic is supported at all), or work only
423 if the critical traffic constitutes only a small portion of the
424 network's theoretical capacity, or work only if all systems are
425 functioning properly, or in the absence of actions by end systems
426 that disrupt the network's operations.
428 There are any number of methods in use, defined, or in progress for
429 accomplishing each of the above techniques. It is expected that this
430 DetNet Architecture will assist various vendors, users, and/or
431 "vertical" Standards Development Organizations (dedicated to a single
432 industry) to make selections among the available means of
433 implementing DetNet networks.
435 3.2. Mechanisms to achieve DetNet QoS
437 3.2.1. Congestion protection
439 3.2.1.1. Eliminate congestion loss
441 The primary means by which DetNet achieves its QoS assurances is to
442 reduce, or even completely eliminate, congestion within a DetNet node
443 as a cause of packet loss. This can be achieved only by the
444 provision of sufficient buffer storage at each node through the
445 network to ensure that no packets are dropped due to a lack of buffer
446 storage. Note that a DetNet flow cannot be throttled, i.e., its
447 transmission rate cannot be reduced via explicit congestion
448 notification.
450 Ensuring adequate buffering requires, in turn, that the source, and
451 every DetNet node along the path to the destination (or nearly every
452 node, see Section 4.3.3) be careful to regulate its output to not
453 exceed the data rate for any DetNet flow, except for brief periods
454 when making up for interfering traffic. Any packet sent ahead of its
455 time potentially adds to the number of buffers required by the next
456 hop DetNet node and may thus exceed the resources allocated for a
457 particular DetNet flow.
459 The low-level mechanisms described in Section 4.5 provide the
460 necessary regulation of transmissions by an end system or DetNet node
461 to provide congestion protection. The allocation of the bandwidth
462 and buffers for a DetNet flow requires provisioning. A DetNet node
463 may have other resources requiring allocation and/or scheduling, that
464 might otherwise be over-subscribed and trigger the rejection of a
465 reservation.
467 3.2.1.2. Jitter Reduction
469 A core objective of DetNet is to enable the convergence of sensitive
470 non-IP networks onto a common network infrastructure. This requires
471 the accurate emulation of currently deployed mission-specific
472 networks, which for example rely on point-to-point analog (e.g.,
473 4-20mA modulation) and serial-digital cables (or buses) for highly
474 reliable, synchronized and jitter-free communications. While the
475 latency of analog transmissions is basically the speed of light,
476 legacy serial links are usually slow (in the order of Kbps) compared
477 to, say, GigE, and some latency is usually acceptable. What is not
478 acceptable is the introduction of excessive jitter, which may, for
479 instance, affect the stability of control systems.
481 Applications that are designed to operate on serial links usually do
482 not provide services to recover the jitter, because jitter simply
483 does not exist there. DetNet flows are generally expected to be
484 delivered in-order and the precise time of reception influences the
485 processes. In order to converge such existing applications, there is
486 a desire to emulate all properties of the serial cable, such as clock
487 transportation, perfect flow isolation and fixed latency. While
488 minimal jitter (in the form of specifying minimum, as well as
489 maximum, end-to-end latency) is supported by DetNet, there are
490 practical limitations on packet-based networks in this regard. In
491 general, users are encouraged to use, instead of, "do this when you
492 get the packet," a combination of:
494 o Sub-microsecond time synchronization among all source and
495 destination end systems, and
497 o Time-of-execution fields in the application packets.
499 Jitter reduction is provided by the mechanisms described in
500 Section 4.5 that also provide congestion protection.
502 3.2.2. Service Protection
504 Service protection aims to mitigate or eliminate packet loss due to
505 equipment failures, random media and/or memory faults. These types
506 of packet loss can be greatly reduced by spreading the data over
507 multiple disjoint forwarding paths. Various service protection
508 methods are described in [RFC6372], e.g., 1+1 linear protection.
509 This section describes the functional details of an additional method
510 in Section 3.2.2.2, which can be implemented as described in
511 Section 3.2.2.3 or as specified in [I-D.ietf-detnet-dp-sol-mpls] in
512 order to provide 1+n hitless protection. The appropriate service
513 protection mechanism depends on the scenario and the requirements.
515 3.2.2.1. In-Order Delivery
517 Out-of-order packet delivery can be a side effect of service
518 protection. Packets delivered out-of-order impact the amount of
519 buffering needed at the destination to properly process the received
520 data. Such packets also influence the jitter of a flow. The DetNet
521 service includes maximum allowed misordering as a constraint. Zero
522 misordering would be a valid service constraint to reflect that the
523 end system(s) of the flow cannot tolerate any out-of-order delivery.
524 DetNet Packet Ordering Functionality (POF) (Section 3.2.2.2) can be
525 used to provide in-order delivery.
527 3.2.2.2. Packet Replication and Elimination
529 This section describes a service protection method that sends copies
530 of the same packets over multiple paths.
532 The DetNet service sub-layer includes the packet replication (PRF),
533 the packet elimination (PEF), and the packet ordering functionality
534 (POF) for use in DetNet edge, relay node, and end system packet
535 processing. Either of these functions can be enabled in a DetNet
536 edge node, relay node or end system. The collective name for all
537 three functions is PREOF. The packet replication and elimination
538 service protection method altogether involves four capabilities:
540 o Providing sequencing information to the packets of a DetNet
541 compound flow. This may be done by adding a sequence number or
542 time stamp as part of DetNet, or may be inherent in the packet,
543 e.g., in a Layer-4 transport protocol, or associated to other
544 physical properties such as the precise time (and radio channel)
545 of reception of the packet. This is typically done once, at or
546 near the source.
548 o The Packet Replication Function (PRF) replicates these packets
549 into multiple DetNet member flows and typically sends them along
550 multiple different paths to the destination(s), e.g., over the
551 explicit routes of Section 3.2.3. The location within a DetNet
552 node, and the mechanism used for the PRF is implementation
553 specific.
555 o The Packet Elimination Function (PEF) eliminates duplicate packets
556 of a DetNet flow based on the sequencing information and a history
557 of received packets. The output of the PEF is always a single
558 packet. This may be done at any DetNet node along the path to
559 save network resources further downstream, in particular if
560 multiple Replication points exist. But the most common case is to
561 perform this operation at the very edge of the DetNet network,
562 preferably in or near the receiver. The location within a DetNet
563 node, and mechanism used for the PEF is implementation specific.
565 o The Packet Ordering Function (POF) uses the sequencing information
566 to re-order a DetNet flow's packets that are received out of
567 order.
569 The order in which a DetNet node applies PEF, POF, and PRF to a
570 DetNet flow is implementation specific.
572 Some service protection mechanisms rely on switching from one flow to
573 another when a failure of a flow is detected. Contrarily, packet
574 replication and elimination combines the DetNet member flows sent
575 along multiple different paths, and performs a packet-by-packet
576 selection of which to discard, e.g., based on sequencing information.
578 In the simplest case, this amounts to replicating each packet in a
579 source that has two interfaces, and conveying them through the
580 network, along separate (SRLG disjoint) paths, to the similarly dual-
581 homed destinations, that discard the extras. This ensures that one
582 path (with zero congestion loss) remains, even if some DetNet
583 intermediate node fails. The sequencing information can also be used
584 for loss detection and for re-ordering.
586 DetNet relay nodes in the network can provide replication and
587 elimination facilities at various points in the network, so that
588 multiple failures can be accommodated.
590 This is shown in Figure 1, where the two relay nodes each replicate
591 (R) the DetNet flow on input, sending the DetNet member flows to both
592 the other relay node and to the end system, and eliminate duplicates
593 (E) on the output interface to the right-hand end system. Any one
594 link in the network can fail, and the DetNet compound flow can still
595 get through. Furthermore, two links can fail, as long as they are in
596 different segments of the network.
598 > > > > > > > > > relay > > > > > > > >
599 > /------------+ R node E +------------\ >
600 > / v + ^ \ >
601 end R + v | ^ + E end
602 system + v | ^ + system
603 > \ v + ^ / >
604 > \------------+ R relay E +-----------/ >
605 > > > > > > > > > node > > > > > > > >
607 Figure 1: Packet replication and elimination
609 Packet replication and elimination does not react to and correct
610 failures; it is entirely passive. Thus, intermittent failures,
611 mistakenly created packet filters, or misrouted data is handled just
612 the same as the equipment failures that are handled by typical
613 routing and bridging protocols.
615 If packet replication and elimination is used over paths providing
616 congestion protection (Section 3.2.1), and member flows that take
617 different-length paths through the network are combined, a merge
618 point may require extra buffering to equalize the delays over the
619 different paths. This equalization ensures that the resultant
620 compound flow will not exceed its contracted bandwidth even after one
621 or the other of the paths is restored after a failure. The extra
622 buffering can be also used to provide in-order delivery.
624 3.2.2.3. Packet encoding for service protection
626 There are methods for using multiple paths to provide service
627 protection that involve encoding the information in a packet
628 belonging to a DetNet flow into multiple transmission units,
629 combining information from multiple packets into any given
630 transmission unit. Such techniques, also known as "network coding",
631 can be used as a DetNet service protection technique.
633 3.2.3. Explicit routes
635 In networks controlled by typical dynamic control protocols such as
636 IS-IS or OSPF, a network topology event in one part of the network
637 can impact, at least briefly, the delivery of data in parts of the
638 network remote from the failure or recovery event. Even the use of
639 redundant paths through a network, e.g., as defined by [RFC6372] do
640 not eliminate the chances of packet loss. Furthermore, out-of-order
641 packet delivery can be a side effect of route changes.
643 Many real-time networks rely on physical rings of two-port devices,
644 with a relatively simple ring control protocol. This supports
645 redundant paths for service protection with a minimum of wiring. As
646 an additional benefit, ring topologies can often utilize different
647 topology management protocols than those used for a mesh network,
648 with a consequent reduction in the response time to topology changes.
649 Of course, this comes at some cost in terms of increased hop count,
650 and thus latency, for the typical path.
652 In order to get the advantages of low hop count and still ensure
653 against even very brief losses of connectivity, DetNet employs
654 explicit routes, where the path taken by a given DetNet flow does not
655 change, at least immediately, and likely not at all, in response to
656 network topology events. Service protection (Section 3.2.2 or
657 Section 3.2.2.3) over explicit routes provides a high likelihood of
658 continuous connectivity. Explicit routes can be established in
659 various ways, e.g., with RSVP-TE [RFC3209], with Segment Routing (SR)
660 [RFC8402], via a Software Defined Networking approach [RFC7426], with
661 IS-IS [RFC7813], etc. Explicit routes are typically used in MPLS TE
662 LSPs.
664 Out-of-order packet delivery can be a side effect of distributing a
665 single flow over multiple paths especially when there is a change
666 from one path to another when combining the flow. This is
667 irrespective of the distribution method used, and also applies to
668 service protection over explicit routes. As described in
669 Section 3.2.2.1, out-of-order packets influence the jitter of a flow
670 and impact the amount of buffering needed to process the data;
671 therefore, DetNet service includes maximum allowed misordering as a
672 constraint. The use of explicit routes helps to provide in-order
673 delivery because there is no immediate route change with the network
674 topology, but the changes are plannable as they are between the
675 different explicit routes.
677 3.3. Secondary goals for DetNet
679 Many applications require DetNet to provide additional services,
680 including coexistence with other QoS mechanisms Section 3.3.1 and
681 protection against misbehaving transmitters Section 3.3.2.
683 3.3.1. Coexistence with normal traffic
685 A DetNet network supports the dedication of a high proportion of the
686 network bandwidth to DetNet flows. But, no matter how much is
687 dedicated for DetNet flows, it is a goal of DetNet to coexist with
688 existing Class of Service schemes (e.g., DiffServ). It is also
689 important that non-DetNet traffic not disrupt the DetNet flow, of
690 course (see Section 3.3.2 and Section 5). For these reasons:
692 o Bandwidth (transmission opportunities) not utilized by a DetNet
693 flow is available to non-DetNet packets (though not to other
694 DetNet flows).
696 o DetNet flows can be shaped or scheduled, in order to ensure that
697 the highest-priority non-DetNet packet is also ensured a worst-
698 case latency.
700 o When transmission opportunities for DetNet flows are scheduled in
701 detail, then the algorithm constructing the schedule should leave
702 sufficient opportunities for non-DetNet packets to satisfy the
703 needs of the users of the network. Detailed scheduling can also
704 permit the time-shared use of buffer resources by different DetNet
705 flows.
707 Traffic policing functions (e.g., [RFC2475]) are used to avoid the
708 starvation of non-DetNet traffic. Thus, the net effect of the
709 presence of DetNet flows in a network on the non-DetNet flows is
710 primarily a reduction in the available bandwidth.
712 3.3.2. Fault Mitigation
714 Robust real-time systems require to reduce the number of possible
715 failures. Filters and policers should be used in a DetNet network to
716 detect if DetNet packets are received on the wrong interface, or at
717 the wrong time, or in too great a volume. Furthermore, filters and
718 policers can take actions to discard the offending packets or flows,
719 or trigger shutting down the offending flow or the offending
720 interface.
722 It is also essential that filters and service remarking be employed
723 at the network edge to prevent non-DetNet packets from being mistaken
724 for DetNet packets, and thus impinging on the resources allocated to
725 DetNet packets.
727 There exist techniques, at present and/or in various stages of
728 standardization, that can perform these fault mitigation tasks that
729 deliver a high probability that misbehaving systems will have zero
730 impact on well-behaved DetNet flows, except of course, for the
731 receiving interface(s) immediately downstream of the misbehaving
732 device. Examples of such techniques include traffic policing
733 functions (e.g., [RFC2475]) and separating flows into per-flow rate-
734 limited queues.
736 4. DetNet Architecture
738 4.1. DetNet stack model
740 DetNet functionality (Section 3) is implemented in two adjacent sub-
741 layers in the protocol stack: the DetNet service sub-layer and the
742 DetNet transport sub-layer. The DetNet service sub-layer provides
743 DetNet service, e.g., service protection, to higher layers in the
744 protocol stack and applications. The DetNet transport sub-layer
745 supports DetNet service in the underlying network, e.g., by providing
746 explicit routes and congestion protection to DetNet flows.
748 4.1.1. Representative Protocol Stack Model
750 Figure 2 illustrates a conceptual DetNet data plane layering model.
751 One may compare it to that in [IEEE802.1CB], Annex C.
753 | packets going | ^ packets coming ^
754 v down the stack v | up the stack |
755 +----------------------+ +-----------------------+
756 | Source | | Destination |
757 +----------------------+ +-----------------------+
758 | Service sub-layer: | | Service sub-layer: |
759 | Packet sequencing | | Duplicate elimination |
760 | Flow replication | | Flow merging |
761 | Packet encoding | | Packet decoding |
762 +----------------------+ +-----------------------+
763 | Transport sub-layer: | | Transport sub-layer: |
764 | Congestion prot. | | Congestion prot. |
765 | Explicit routes | | Explicit routes |
766 +----------------------+ +-----------------------+
767 | Lower layers | | Lower layers |
768 +----------------------+ +-----------------------+
769 v ^
770 \_________________________/
772 Figure 2: DetNet data plane protocol stack
774 Not all sub-layers are required for any given application, or even
775 for any given network. The functionality shown in Figure 2 is:
777 Application
778 Shown as "source" and "destination" in the diagram.
780 Packet sequencing
781 As part of DetNet service protection, supplies the sequence
782 number for packet replication and elimination
783 (Section 3.2.2). Peers with Duplicate elimination. This
784 sub-layer is not needed if a Layer-4 transport protocol is
785 expected to perform any packet sequencing and duplicate
786 elimination required by the DetNet flow replication.
788 Duplicate elimination
789 As part of the DetNet service sub-layer, based on the
790 sequenced number supplied by its peer, packet sequencing,
791 Duplicate elimination discards any duplicate packets
792 generated by DetNet flow replication. It can operate on
793 member flows, compound flows, or both. The replication may
794 also be inferred from other information such as the precise
795 time of reception in a scheduled network. The duplicate
796 elimination sub-layer may also perform resequencing of
797 packets to restore packet order in a flow that was disrupted
798 by the loss of packets on one or another of the multiple
799 paths taken.
801 Flow replication
802 As part of DetNet service protection, packets that belong to
803 a DetNet compound flow are replicated into two or more DetNet
804 member flows. This function is separate from packet
805 sequencing. Flow replication can be an explicit replication
806 and remarking of packets, or can be performed by, for
807 example, techniques similar to ordinary multicast
808 replication, albeit with resource allocation implications.
809 Peers with DetNet flow merging.
811 Flow merging
812 As part of DetNet service protection, merges DetNet member
813 flows together for packets coming up the stack belonging to a
814 specific DetNet compound flow. Peers with DetNet flow
815 replication. DetNet flow merging, together with packet
816 sequencing, duplicate elimination, and DetNet flow
817 replication perform packet replication and elimination
818 (Section 3.2.2).
820 Packet encoding
821 As part of DetNet service protection, as an alternative to
822 packet sequencing and flow replication, packet encoding
823 combines the information in multiple DetNet packets, perhaps
824 from different DetNet compound flows, and transmits that
825 information in packets on different DetNet member Flows.
826 Peers with Packet decoding.
828 Packet decoding
829 As part of DetNet service protection, as an alternative to
830 flow merging and duplicate elimination, packet decoding takes
831 packets from different DetNet member flows, and computes from
832 those packets the original DetNet packets from the compound
833 flows input to packet encoding. Peers with Packet encoding.
835 Congestion protection
836 The DetNet transport sub-layer provides congestion
837 protection. See Section 4.5. The actual queuing and shaping
838 mechanisms are typically provided by underlying subnet, these
839 can be closely associated with the means of providing paths
840 for DetNet flows, the path and the congestion protection are
841 conflated in this figure.
843 Explicit routes
844 The DetNet transport sub-layer provides mechanisms to ensure
845 that fixed paths are provided for DetNet flows. These
846 explicit paths avoid the impact of network convergence.
848 Operations, Administration, and Maintenance (OAM) leverages in-band
849 and out-of-band signaling that validates whether the service is
850 effectively obtained within QoS constraints. OAM is not shown in
851 Figure 2; it may reside in any number of the layers. OAM can involve
852 specific tagging added in the packets for tracing implementation or
853 network configuration errors; traceability enables to find whether a
854 packet is a replica, which DetNet relay node performed the
855 replication, and which segment was intended for the replica. Active
856 and hybrid OAM methods require additional bandwidth to perform fault
857 management and performance monitoring of the DetNet domain. OAM may,
858 for instance, generate special test probes or add OAM information
859 into the data packet.
861 The packet sequencing and replication elimination functions at the
862 source and destination ends of a DetNet compound flow may be
863 performed either in the end system or in a DetNet relay node.
865 4.1.2. DetNet Data Plane Overview
867 A "Deterministic Network" will be composed of DetNet enabled end
868 systems, DetNet edge nodes, DetNet relay nodes and collectively
869 deliver DetNet services. DetNet relay and edge nodes are
870 interconnected via DetNet transit nodes (e.g., LSRs) which support
871 DetNet, but are not DetNet service aware. All DetNet nodes are
872 connected to sub-networks, where a point-to-point link is also
873 considered as a simple sub-network. These sub-networks will provide
874 DetNet compatible service for support of DetNet traffic. Examples of
875 sub-networks include MPLS TE, IEEE 802.1 TSN and OTN. Of course,
876 multi-layer DetNet systems may also be possible, where one DetNet
877 appears as a sub-network, and provides service to, a higher layer
878 DetNet system. A simple DetNet concept network is shown in Figure 3.
879 Note that in this and following figures "Transport" and "Trp" refer
880 to the DetNet transport sub-layer, "Service" and "Svc" refer to the
881 DetNet service sub-layer, which are described in detail in
882 Section 4.1.
884 TSN Edge Transit Relay DetNet
885 End System Node Node Node End System
887 +---------+ +.........+ +---------+
888 | Appl. |<--:Svc Proxy:-- End to End Service ---------->| Appl. |
889 +---------+ +---------+ +---------+ +---------+
890 | TSN | |TSN| |Svc|<-- DetNet flow ---: Service :-->| Service |
891 +---------+ +---+ +---+ +---------+ +---------+ +---------+
892 |Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
893 +-------.-+ +-.-+ +-.-+ +--.----.-+ +-.-+ +-.-+ +---.-----+
894 : Link : / ,-----. \ : Link : / ,-----. \
895 +.......+ +-[ Sub ]-+ +........+ +-[ Sub ]-+
896 [Network] [Network]
897 `-----' `-----'
899 Figure 3: A Simple DetNet Enabled Network
901 Distinguishing the function of two DetNet data plane sub-layers, the
902 DetNet service sub-layer and the DetNet transport sub-layer, helps to
903 explore and evaluate various combinations of the data plane solutions
904 available, some are illustrated in Figure 4. This separation of
905 DetNet sub-layers, while helpful, should not be considered as formal
906 requirement. For example, some technologies may violate these strict
907 sub-layers and still be able to deliver a DetNet service.
909 .
910 .
911 +----------------------------+
912 | DetNet Service sub-layer | PW, UDP, GRE
913 +----------------------------+
914 | DetNet Transport sub-layer | IPv6, IPv4, MPLS TE LSPs, MPLS SR
915 +----------------------------+
916 .
917 .
919 Figure 4: DetNet adaptation to data plane
921 In some networking scenarios, the end system initially provides a
922 DetNet flow encapsulation, which contains all information needed by
923 DetNet nodes (e.g., Real-time Transport Protocol (RTP) [RFC3550]
924 based DetNet flow carried over a native UDP/IP network or
925 PseudoWire). In other scenarios, the encapsulation formats might
926 differ significantly.
928 There are many valid options to create a data plane solution for
929 DetNet traffic by selecting a technology approach for the DetNet
930 service sub-layer and also selecting a technology approach for the
931 DetNet transport sub-layer. There are a high number of valid
932 combinations.
934 One of the most fundamental differences between different potential
935 data plane options is the basic headers used by DetNet nodes. For
936 example, the basic service can be delivered based on an MPLS label or
937 an IP header. This decision impacts the basic forwarding logic for
938 the DetNet service sub-layer. Note that in both cases, IP addresses
939 are used to address DetNet nodes. The selected DetNet transport sub-
940 layer technology also needs to be mapped to the sub-net technology
941 used to interconnect DetNet nodes. For example, DetNet flows will
942 need to be mapped to TSN Streams.
944 4.1.3. Network reference model
946 Figure 5 shows another view of the DetNet service related reference
947 points and main components.
949 DetNet DetNet
950 end system end system
951 _ _
952 / \ +----DetNet-UNI (U) / \
953 /App\ | /App\
954 /-----\ | /-----\
955 | NIC | v ________ | NIC |
956 +--+--+ _____ / \ DetNet-UNI (U) --+ +--+--+
957 | / \__/ \ | |
958 | / +----+ +----+ \_____ | |
959 | / | | | | \_______ | |
960 +------U PE +----+ P +----+ \ _ v |
961 | | | | | | | ___/ \ |
962 | +--+-+ +----+ | +----+ | / \_ |
963 \ | | | | | / \ |
964 \ | +----+ +--+-+ +--+PE |------ U-----+
965 \ | | | | | | | | | \_ _/
966 \ +---+ P +----+ P +--+ +----+ | \____/
967 \___ | | | | /
968 \ +----+__ +----+ DetNet-1 DetNet-2
969 | \_____/ \___________/ |
970 | |
971 | | End-to-End service | | | |
972 <------------------------------------------------------------->
973 | | DetNet service | | | |
974 | <------------------------------------------------> |
975 | | | | | |
977 Figure 5: DetNet Service Reference Model (multi-domain)
979 DetNet-UNIs ("U" in Figure 5) are assumed in this document to be
980 packet-based reference points and provide connectivity over the
981 packet network. A DetNet-UNI may provide multiple functions, e.g.,
982 it may add networking technology specific encapsulation to the DetNet
983 flows if necessary; it may provide status of the availability of the
984 resources associated with a reservation; it may provide a
985 synchronization service for the end system; it may carry enough
986 signaling to place the reservation in a network without a controller,
987 or if the controller only deals with the network but not the end
988 systems. Internal reference points of end systems (between the
989 application and the NIC) are more challenging from control
990 perspective and they may have extra requirements (e.g., in-order
991 delivery is expected in end system internal reference points, whereas
992 it is considered optional over the DetNet-UNI).
994 4.2. DetNet systems
996 4.2.1. End system
998 The native data flow between the source/destination end systems is
999 referred to as application-flow (App-flow). The traffic
1000 characteristics of an App-flow can be CBR (constant bit rate) or VBR
1001 (variable bit rate) and can have L1 or L2 or L3 encapsulation (e.g.,
1002 TDM (time-division multiplexing), Ethernet, IP). These
1003 characteristics are considered as input for resource reservation and
1004 might be simplified to ensure determinism during transport (e.g.,
1005 making reservations for the peak rate of VBR traffic, etc.).
1007 An end system may or may not be DetNet transport sub-layer aware or
1008 DetNet service sub-layer aware. That is, an end system may or may
1009 not contain DetNet specific functionality. End systems with DetNet
1010 functionalities may have the same or different transport sub-layer as
1011 the connected DetNet domain. Categorization of end systems are shown
1012 in Figure 6.
1014 End system
1015 |
1016 |
1017 | DetNet aware ?
1018 / \
1019 +------< >------+
1020 NO | \ / | YES
1021 | v |
1022 DetNet unaware |
1023 End system |
1024 | Service/Transport
1025 | sub-layer
1026 / \ aware ?
1027 +--------< >-------------+
1028 t-aware | \ / | s-aware
1029 | v |
1030 | | both |
1031 | | |
1032 DetNet t-aware | DetNet s-aware
1033 End system | End system
1034 v
1035 DetNet st-aware
1036 End system
1038 Figure 6: Categorization of end systems
1040 Note some known use case examples for end systems:
1042 o DetNet unaware: The classic case requiring service proxies.
1044 o DetNet t-aware: A DetNet transport sub-layer aware system. It
1045 knows about some TSN functions (e.g., reservation), but not about
1046 service protection.
1048 o DetNet s-aware: A DetNet service sub-layer aware system. It
1049 supplies sequence numbers, but doesn't know about zero congestion
1050 loss.
1052 o DetNet st-aware: A full functioning DetNet end system, it has
1053 DetNet functionalities and usually the same forwarding paradigm as
1054 the connected DetNet domain. It can be treated as an integral
1055 part of the DetNet domain.
1057 4.2.2. DetNet edge, relay, and transit nodes
1059 As shown in Figure 3, DetNet edge nodes providing proxy service and
1060 DetNet relay nodes providing the DetNet service sub-layer are DetNet-
1061 aware, and DetNet transit nodes need only be aware of the DetNet
1062 transport sub-layer.
1064 In general, if a DetNet flow passes through one or more DetNet-
1065 unaware network nodes between two DetNet nodes providing the DetNet
1066 transport sub-layer for that flow, there is a potential for
1067 disruption or failure of the DetNet QoS. A network administrator
1068 needs to ensure that the DetNet-unaware network nodes are configured
1069 to minimize the chances of packet loss and delay, and provision
1070 enough extra buffer space in the DetNet transit node following the
1071 DetNet-unaware network nodes to absorb the induced latency
1072 variations.
1074 4.3. DetNet flows
1076 4.3.1. DetNet flow types
1078 A DetNet flow can have different formats while it is transported
1079 between the peer end systems. Therefore, the following possible
1080 types / formats of a DetNet flow are distinguished in this document:
1082 o App-flow: native format of the data carried over a DetNet flow.
1083 It does not contain any DetNet related attributes.
1085 o DetNet-t-flow: specific format of a DetNet flow. Only requires
1086 the congestion / latency features provided by the DetNet transport
1087 sub-layer.
1089 o DetNet-s-flow: specific format of a DetNet flow. Only requires
1090 the service protection feature ensured by the DetNet service sub-
1091 layer.
1093 o DetNet-st-flow: specific format of a DetNet flow. It requires
1094 both DetNet service sub-layer and DetNet transport sub-layer
1095 functions during forwarding.
1097 4.3.2. Source transmission behavior
1099 For the purposes of congestion protection, DetNet flows can be
1100 synchronous or asynchronous. In synchronous DetNet flows, at least
1101 the DetNet nodes (and possibly the end systems) are closely time
1102 synchronized, typically to better than 1 microsecond. By
1103 transmitting packets from different DetNet flows or classes of DetNet
1104 flows at different times, using repeating schedules synchronized
1105 among the DetNet nodes, resources such as buffers and link bandwidth
1106 can be shared over the time domain among different DetNet flows.
1107 There is a tradeoff among techniques for synchronous DetNet flows
1108 between the burden of fine-grained scheduling and the benefit of
1109 reducing the required resources, especially buffer space.
1111 In contrast, asynchronous DetNet flows are not coordinated with a
1112 fine-grained schedule, so relay and end systems must assume worst-
1113 case interference among DetNet flows contending for buffer resources.
1114 Asynchronous DetNet flows are characterized by:
1116 o A maximum packet size;
1118 o An observation interval; and
1120 o A maximum number of transmissions during that observation
1121 interval.
1123 These parameters, together with knowledge of the protocol stack used
1124 (and thus the size of the various headers added to a packet), limit
1125 the number of bit times per observation interval that the DetNet flow
1126 can occupy the physical medium.
1128 The source is required not to exceed these limits in order to obtain
1129 DetNet service. If the source transmits less data than this limit
1130 allows, the unused resource such as link bandwidth can be made
1131 available by the DetNet system to non-DetNet packets as long as all
1132 guarantees are fulfilled. However, making those resources available
1133 to DetNet packets in other DetNet flows would serve no purpose.
1134 Those other DetNet flows have their own dedicated resources, on the
1135 assumption that all DetNet flows can use all of their resources over
1136 a long period of time.
1138 There is no provision in DetNet for throttling DetNet flows, i.e.,
1139 the transmission rate cannot be reduced via explicit congestion
1140 notification. The assumption is that a DetNet flow, to be useful,
1141 must be delivered in its entirety. That is, while any useful
1142 application is written to expect a certain number of lost packets,
1143 the real-time applications of interest to DetNet demand that the loss
1144 of data due to the network is a rare event.
1146 Although DetNet strives to minimize the changes required of an
1147 application to allow it to shift from a special-purpose digital
1148 network to an Internet Protocol network, one fundamental shift in the
1149 behavior of network applications is impossible to avoid: the
1150 reservation of resources before the application starts. In the first
1151 place, a network cannot deliver finite latency and practically zero
1152 packet loss to an arbitrarily high offered load. Secondly, achieving
1153 practically zero packet loss for unthrottled (though bandwidth
1154 limited) DetNet flows means that DetNet nodes have to dedicate buffer
1155 resources to specific DetNet flows or to classes of DetNet flows.
1157 The requirements of each reservation have to be translated into the
1158 parameters that control each DetNet system's queuing, shaping, and
1159 scheduling functions and delivered to the DetNet nodes and end
1160 systems.
1162 4.3.3. Incomplete Networks
1164 The presence in the network of intermediate nodes or subnets that are
1165 not fully capable of offering DetNet services complicates the ability
1166 of the intermediate nodes and/or controller to allocate resources, as
1167 extra buffering must be allocated at points downstream from the non-
1168 DetNet intermediate node for a DetNet flow. This extra buffering may
1169 increase latency and/or jitter.
1171 4.4. Traffic Engineering for DetNet
1173 Traffic Engineering Architecture and Signaling (TEAS) [TEAS] defines
1174 traffic-engineering architectures for generic applicability across
1175 packet and non-packet networks. From a TEAS perspective, Traffic
1176 Engineering (TE) refers to techniques that enable operators to
1177 control how specific traffic flows are treated within their networks.
1179 Because if its very nature of establishing explicit optimized paths,
1180 Deterministic Networking can be seen as a new, specialized branch of
1181 Traffic Engineering, and inherits its architecture with a separation
1182 into planes.
1184 The Deterministic Networking architecture is thus composed of three
1185 planes, a (User) Application Plane, a Controller Plane, and a Network
1186 Plane, which echoes that of Figure 1 of Software-Defined Networking
1187 (SDN): Layers and Architecture Terminology [RFC7426].:
1189 4.4.1. The Application Plane
1191 Per [RFC7426], the Application Plane includes both applications and
1192 services. In particular, the Application Plane incorporates the User
1193 Agent, a specialized application that interacts with the end user /
1194 operator and performs requests for Deterministic Networking services
1195 via an abstract Flow Management Entity, (FME) which may or may not be
1196 collocated with (one of) the end systems.
1198 At the Application Plane, a management interface enables the
1199 negotiation of flows between end systems. An abstraction of the flow
1200 called a Traffic Specification (TSpec) provides the representation.
1201 This abstraction is used to place a reservation over the (Northbound)
1202 Service Interface and within the Application plane. It is associated
1203 with an abstraction of location, such as IP addresses and DNS names,
1204 to identify the end systems and possibly specify DetNet nodes.
1206 4.4.2. The Controller Plane
1208 The Controller Plane corresponds to the aggregation of the Control
1209 and Management Planes in [RFC7426], though Common Control and
1210 Measurement Plane (CCAMP) [CCAMP] makes an additional distinction
1211 between management and measurement. When the logical separation of
1212 the Control, Measurement and other Management entities is not
1213 relevant, the term Controller Plane is used for simplicity to
1214 represent them all, and the term Controller Plane Function (CPF)
1215 refers to any device operating in that plane, whether is it a Path
1216 Computation Element (PCE) [RFC4655], or a Network Management entity
1217 (NME), or a distributed control plane. The CPF is a core element of
1218 a controller, in charge of computing Deterministic paths to be
1219 applied in the Network Plane.
1221 A (Northbound) Service Interface enables applications in the
1222 Application Plane to communicate with the entities in the Controller
1223 Plane as illustrated in Figure 7.
1225 One or more CPF(s) collaborate to implement the requests from the FME
1226 as Per-Flow Per-Hop Behaviors installed in the DetNet nodes for each
1227 individual flow. The CPFs place each flow along a deterministic
1228 sequence of DetNet nodes so as to respect per-flow constraints such
1229 as security and latency, and optimize the overall result for metrics
1230 such as an abstract aggregated cost. The deterministic sequence can
1231 typically be more complex than a direct sequence and include
1232 redundancy path, with one or more packet replication and elimination
1233 points. Scaling to larger networks is discussed in Section 4.9.
1235 4.4.3. The Network Plane
1237 The Network Plane represents the network devices and protocols as a
1238 whole, regardless of the Layer at which the network devices operate.
1239 It includes Forwarding Plane (data plane), Application, and
1240 Operational Plane (e.g., OAM) aspects.
1242 The network Plane comprises the Network Interface Cards (NIC) in the
1243 end systems, which are typically IP hosts, and DetNet nodes, which
1244 are typically IP routers and MPLS switches. Network-to-Network
1245 Interfaces such as used for Traffic Engineering path reservation in
1246 [RFC5921], as well as User-to-Network Interfaces (UNI) such as
1247 provided by the Local Management Interface (LMI) between network and
1248 end systems, are both part of the Network Plane, both in the control
1249 plane and the data plane.
1251 A Southbound (Network) Interface enables the entities in the
1252 Controller Plane to communicate with devices in the Network Plane as
1253 illustrated in Figure 7. This interface leverages and extends TEAS
1254 to describe the physical topology and resources in the Network Plane.
1256 End End
1257 System System
1259 -+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
1261 CPF CPF CPF CPF
1263 -+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
1265 DetNet DetNet DetNet DetNet
1266 Node Node Node Node
1267 NIC NIC
1268 DetNet DetNet DetNet DetNet
1269 Node Node Node Node
1271 Figure 7: Northbound and Southbound interfaces
1273 The DetNet nodes (and possibly the end systems NIC) expose their
1274 capabilities and physical resources to the controller (the CPF), and
1275 update the CPFs with their dynamic perception of the topology, across
1276 the Southbound Interface. In return, the CPFs set the per-flow paths
1277 up, providing a Flow Characterization that is more tightly coupled to
1278 the DetNet node Operation than a TSpec.
1280 At the Network plane, DetNet nodes may exchange information regarding
1281 the state of the paths, between adjacent DetNet nodes and possibly
1282 with the end systems, and forward packets within constraints
1283 associated to each flow, or, when unable to do so, perform a last
1284 resort operation such as drop or declassify.
1286 This document focuses on the Southbound interface and the operation
1287 of the Network Plane.
1289 4.5. Queuing, Shaping, Scheduling, and Preemption
1291 DetNet achieves congestion protection and bounded delivery latency by
1292 reserving bandwidth and buffer resources at each DetNet node along
1293 the path of the DetNet flow. The reservation itself is not
1294 sufficient, however. Implementors and users of a number of
1295 proprietary and standard real-time networks have found that standards
1296 for specific data plane techniques are required to enable these
1297 assurances to be made in a multi-vendor network. The fundamental
1298 reason is that latency variation in one DetNet system results in the
1299 need for extra buffer space in the next-hop DetNet system(s), which
1300 in turn, increases the worst-case per-hop latency.
1302 Standard queuing and transmission selection algorithms allow traffic
1303 engineering Section 4.4 to compute the latency contribution of each
1304 DetNet node to the end-to-end latency, to compute the amount of
1305 buffer space required in each DetNet node for each incremental DetNet
1306 flow, and most importantly, to translate from a flow specification to
1307 a set of values for the managed objects that control each relay or
1308 end system. For example, the IEEE 802.1 WG has specified (and is
1309 specifying) a set of queuing, shaping, and scheduling algorithms that
1310 enable each DetNet node, and/or a central controller, to compute
1311 these values. These algorithms include:
1313 o A credit-based shaper [IEEE802.1Qav] (superseded by
1314 [IEEE802.1Q-2018]).
1316 o Time-gated queues governed by a rotating time schedule based on
1317 synchronized time [IEEE802.1Qbv] (superseded by
1318 [IEEE802.1Q-2018]).
1320 o Synchronized double (or triple) buffers driven by synchronized
1321 time ticks. [IEEE802.1Qch] (superseded by [IEEE802.1Q-2018]).
1323 o Pre-emption of an Ethernet packet in transmission by a packet with
1324 a more stringent latency requirement, followed by the resumption
1325 of the preempted packet [IEEE802.1Qbu] (superseded by
1326 [IEEE802.1Q-2018]), [IEEE802.3br] (superseded by
1327 [IEEE802.3-2018]).
1329 While these techniques are currently embedded in Ethernet
1330 [IEEE802.3-2018] and bridging standards, we can note that they are
1331 all, except perhaps for packet preemption, equally applicable to
1332 other media than Ethernet, and to routers as well as bridges. Other
1333 media may have its own methods, see, e.g.,
1334 [I-D.ietf-6tisch-architecture], [RFC7554]. DetNet may include such
1335 definitions in the future, or may define how these techniques can be
1336 used by DetNet nodes.
1338 4.6. Service instance
1340 A Service instance represents all the functions required on a DetNet
1341 node to allow the end-to-end service between the UNIs.
1343 The DetNet network general reference model is shown in Figure 8 for a
1344 DetNet service scenario (i.e., between two DetNet-UNIs). In this
1345 figure, end systems ("A" and "B") are connected directly to the edge
1346 nodes of an IP/MPLS network ("PE1" and "PE2"). End systems
1347 participating in DetNet communication may require connectivity before
1348 setting up an App-flow that requires the DetNet service. Such a
1349 connectivity related service instance and the one dedicated for
1350 DetNet service share the same access. Packets belonging to a DetNet
1351 flow are selected by a filter configured on the access ("F1" and
1352 "F2"). As a result, data flow specific access ("access-A + F1" and
1353 "access-B + F2") are terminated in the flow specific service instance
1354 ("SI-1" and "SI-2"). A tunnel is used to provide connectivity
1355 between the service instances.
1357 The tunnel is exclusively used for the packets of the DetNet flow
1358 between "SI-1" and "SI-2". The service instances are configured to
1359 implement DetNet functions and a flow specific DetNet forwarding.
1360 The service instance and the tunnel may or may not be shared by
1361 multiple DetNet flows. Sharing the service instance by multiple
1362 DetNet flows requires properly populated forwarding tables of the
1363 service instance.
1365 access-A access-B
1366 <-----> <-------- tunnel ----------> <----->
1368 +---------+ ___ _ +---------+
1369 End system | +----+ | / \/ \_ | +----+ | End system
1370 "A" -------F1+ | | / \ | | +F2----- "B"
1371 | | +========+ IP/MPLS +=======+ | |
1372 | |SI-1| | \__ Net._/ | |SI-2| |
1373 | +----+ | \____/ | +----+ |
1374 |PE1 | | PE2|
1375 +---------+ +---------+
1377 Figure 8: DetNet network general reference model
1379 The tunnel between the service instances may have some special
1380 characteristics. For example, in case of a DetNet L3 service, there
1381 are differences in the usage of the PW for DetNet traffic compared to
1382 the network model described in [RFC6658]. In the DetNet scenario,
1383 the PW is likely to be used exclusively by the DetNet flow, whereas
1384 [RFC6658] states: "The packet PW appears as a single point-to-point
1385 link to the client layer. Network-layer adjacency formation and
1386 maintenance between the client equipment will follow the normal
1387 practice needed to support the required relationship in the client
1388 layer ... This packet PseudoWire is used to transport all of the
1389 required Layer-2 and Layer-3 protocols between LSR1 and LSR2".
1390 Further details are network technology specific and can be found in
1391 [I-D.ietf-detnet-dp-sol-mpls] and [I-D.ietf-detnet-dp-sol-ip].
1393 4.7. Flow identification at technology borders
1395 4.7.1. Exporting flow identification
1397 A DetNet node may need to map specific flows to lower layer flows (or
1398 Streams) in order to provide specific queuing and shaping services
1399 for specific flows. For example:
1401 o A non-IP, strictly L2 source end system X may be sending multiple
1402 flows to the same L2 destination end system Y. Those flows may
1403 include DetNet flows with different QoS requirements, and may
1404 include non-DetNet flows.
1406 o A router may be sending any number of flows to another router.
1407 Again, those flows may include DetNet flows with different QoS
1408 requirements, and may include non-DetNet flows.
1410 o Two routers may be separated by bridges. For these bridges to
1411 perform any required per-flow queuing and shaping, they must be
1412 able to identify the individual flows.
1414 o A Label Edge Router (LER) may have a Label Switched Path (LSP) set
1415 up for handling traffic destined for a particular IP address
1416 carrying only non-DetNet flows. If a DetNet flow to that same
1417 address is requested, a separate LSP may be needed, in order that
1418 all of the Label Switch Routers (LSRs) along the path to the
1419 destination give that flow special queuing and shaping.
1421 The need for a lower-layer node to be aware of individual higher-
1422 layer flows is not unique to DetNet. But, given the endless
1423 complexity of layering and relayering over tunnels that is available
1424 to network designers, DetNet needs to provide a model for flow
1425 identification that is better than packet inspection. That is not to
1426 say that packet inspection to Layer-4 or Layer-5 addresses will not
1427 be used, or the capability standardized; but, there are alternatives.
1429 A DetNet relay node can connect DetNet flows on different paths using
1430 different flow identification methods. For example:
1432 o A single unicast DetNet flow passing from router A through a
1433 bridged network to router B may be assigned a TSN Stream
1434 identifier that is unique within that bridged network. The
1435 bridges can then identify the flow without accessing higher-layer
1436 headers. Of course, the receiving router must recognize and
1437 accept that TSN Stream.
1439 o A DetNet flow passing from LSR A to LSR B may be assigned a
1440 different label than that used for other flows to the same IP
1441 destination.
1443 In any of the above cases, it is possible that an existing DetNet
1444 flow can be an aggregate carrying multiple other DetNet flows. (Not
1445 to be confused with DetNet compound vs. member flows.) Of course,
1446 this requires that the aggregate DetNet flow be provisioned properly
1447 to carry the aggregated flows.
1449 Thus, rather than packet inspection, there is the option to export
1450 higher-layer information to the lower layer. The requirement to
1451 support one or the other method for flow identification (or both) is
1452 a complexity that is part of DetNet control models.
1454 4.7.2. Flow attribute mapping between layers
1456 Transport of DetNet flows over multiple technology domains may
1457 require that lower layers are aware of specific flows of higher
1458 layers. Such an "exporting of flow identification" is needed each
1459 time when the forwarding paradigm is changed on the forwarding path
1460 (e.g., two LSRs are interconnected by a L2 bridged domain, etc.).
1461 The three representative forwarding methods considered for
1462 deterministic networking are:
1464 o IP routing
1466 o MPLS label switching
1468 o Ethernet bridging
1470 A packet with corresponding Flow-IDs is illustrated in Figure 9,
1471 which also indicates where each Flow-ID can be added or removed.
1473 add/remove add/remove
1474 Eth Flow-ID IP Flow-ID
1475 | |
1476 v v
1477 +-----------------------------------------------------------+
1478 | | | | |
1479 | Eth | MPLS | IP | Application data |
1480 | | | | |
1481 +-----------------------------------------------------------+
1482 ^
1483 |
1484 add/remove
1485 MPLS Flow-ID
1487 Figure 9: Packet with multiple Flow-IDs
1489 The additional (domain specific) Flow-ID can be
1491 o created by a domain specific function or
1493 o derived from the Flow-ID added to the App-flow.
1495 The Flow-ID must be unique inside a given domain. Note that the
1496 Flow-ID added to the App-flow is still present in the packet, but
1497 transport nodes may lack the function to recognize it; that's why the
1498 additional Flow-ID is added.
1500 4.7.3. Flow-ID mapping examples
1502 IP nodes and MPLS nodes are assumed to be configured to push such an
1503 additional (domain specific) Flow-ID when sending traffic to an
1504 Ethernet switch (as shown in the examples below).
1506 Figure 10 shows a scenario where an IP end system ("IP-A") is
1507 connected via two Ethernet switches ("ETH-n") to an IP router ("IP-
1508 1").
1510 IP domain
1511 <-----------------------------------------------
1513 +======+ +======+
1514 |L3-ID | |L3-ID |
1515 +======+ /\ +-----+ +======+
1516 / \ Forward as | |
1517 /IP-A\ per ETH-ID |IP-1 | Recognize
1518 Push ------> +-+----+ | +---+-+ <----- ETH-ID
1519 ETH-ID | +----+-----+ |
1520 | v v |
1521 | +-----+ +-----+ |
1522 +------+ | | +---------+
1523 +......+ |ETH-1+----+ETH-2| +======+
1524 .L3-ID . +-----+ +-----+ |L3-ID |
1525 +======+ +......+ +======+
1526 |ETH-ID| .L3-ID . |ETH-ID|
1527 +======+ +======+ +------+
1528 |ETH-ID|
1529 +======+
1531 Ethernet domain
1532 <---------------->
1534 Figure 10: IP nodes interconnected by an Ethernet domain
1536 End system "IP-A" uses the original App-flow specific ID ("L3-ID"),
1537 but as it is connected to an Ethernet domain it has to push an
1538 Ethernet-domain specific flow-ID ("ETH-ID") before sending the packet
1539 to "ETH-1" node. Ethernet switch "ETH-1" can recognize the data flow
1540 based on the "ETH-ID" and it does forwarding toward "ETH-2". "ETH-2"
1541 switches the packet toward the IP router. "IP-1" must be configured
1542 to receive the Ethernet Flow-ID specific multicast flow, but (as it
1543 is an L3 node) it decodes the data flow ID based on the "L3-ID"
1544 fields of the received packet.
1546 Figure 11 shows a scenario where MPLS domain nodes ("PE-n" and "P-m")
1547 are connected via two Ethernet switches ("ETH-n").
1549 MPLS domain
1550 <----------------------------------------------->
1552 +=======+ +=======+
1553 |MPLS-ID| |MPLS-ID|
1554 +=======+ +-----+ +-----+ +=======+ +-----+
1555 | | Forward as | | | |
1556 |PE-1 | per ETH-ID | P-2 +-----------+ PE-2|
1557 Push -----> +-+---+ | +---+-+ +-----+
1558 ETH-ID | +-----+----+ | \ Recognize
1559 | v v | +-- ETH-ID
1560 | +-----+ +-----+ |
1561 +---+ | | +----+
1562 +.......+ |ETH-1+----+ETH-2| +=======+
1563 .MPLS-ID. +-----+ +-----+ |MPLS-ID|
1564 +=======+ +=======+
1565 |ETH-ID | +.......+ |ETH-ID |
1566 +=======+ .MPLS-ID. +-------+
1567 +=======+
1568 |ETH-ID |
1569 +=======+
1570 Ethernet domain
1571 <---------------->
1573 Figure 11: MPLS nodes interconnected by an Ethernet domain
1575 "PE-1" uses the MPLS specific ID ("MPLS-ID"), but as it is connected
1576 to an Ethernet domain it has to push an Ethernet-domain specific
1577 flow-ID ("ETH-ID") before sending the packet to "ETH-1". Ethernet
1578 switch "ETH-1" can recognize the data flow based on the "ETH-ID" and
1579 it does forwarding toward "ETH-2". "ETH-2" switches the packet
1580 toward the MPLS node ("P-2"). "P-2" must be configured to receive
1581 the Ethernet Flow-ID specific multicast flow, but (as it is an MPLS
1582 node) it decodes the data flow ID based on the "MPLS-ID" fields of
1583 the received packet.
1585 One can appreciate from the above example that, when the means used
1586 for DetNet flow identification is altered or exported, the means for
1587 encoding the sequence number information must similarly be altered or
1588 exported.
1590 4.8. Advertising resources, capabilities and adjacencies
1592 Provisioning of DetNet requires knowledge about:
1594 o Details of the DetNet system's capabilities that are required in
1595 order to accurately allocate that DetNet system's resources, as
1596 well as other DetNet systems' resources. This includes, for
1597 example, which specific queuing and shaping algorithms are
1598 implemented (Section 4.5), the number of buffers dedicated for
1599 DetNet allocation, and the worst-case forwarding delay and
1600 misordering.
1602 o The dynamic state of a DetNet node's DetNet resources.
1604 o The identity of the DetNet system's neighbors, and the
1605 characteristics of the link(s) between the DetNet systems,
1606 including the latency of the links (in nanoseconds).
1608 4.9. Scaling to larger networks
1610 Reservations for individual DetNet flows require considerable state
1611 information in each DetNet node, especially when adequate fault
1612 mitigation (Section 3.3.2) is required. The DetNet data plane, in
1613 order to support larger numbers of DetNet flows, must support the
1614 aggregation of DetNet flows. Such aggregated flows can be viewed by
1615 the DetNet nodes' data plane largely as individual DetNet flows.
1616 Without such aggregation, the per-relay system may limit the scale of
1617 DetNet networks. Example techniques that may be used include MPLS
1618 hierarchy and IP DiffServ Code Points (DSCPs).
1620 4.10. Compatibility with Layer-2
1622 Standards providing similar capabilities for bridged networks (only)
1623 have been and are being generated in the IEEE 802 LAN/MAN Standards
1624 Committee. The present architecture describes an abstract model that
1625 can be applicable both at Layer-2 and Layer-3, and over links not
1626 defined by IEEE 802.
1628 DetNet enabled end systems and DetNet nodes can be interconnected by
1629 sub-networks, i.e., Layer-2 technologies. These sub-networks will
1630 provide DetNet compatible service for support of DetNet traffic.
1631 Examples of sub-networks include MPLS TE, 802.1 TSN, and a point-to-
1632 point OTN link. Of course, multi-layer DetNet systems may be
1633 possible too, where one DetNet appears as a sub-network, and provides
1634 service to, a higher layer DetNet system.
1636 5. Security Considerations
1638 Security in the context of Deterministic Networking has an added
1639 dimension; the time of delivery of a packet can be just as important
1640 as the contents of the packet, itself. A man-in-the-middle attack,
1641 for example, can impose, and then systematically adjust, additional
1642 delays into a link, and thus disrupt or subvert a real-time
1643 application without having to crack any encryption methods employed.
1644 See [RFC7384] for an exploration of this issue in a related context.
1646 Furthermore, in a control system where millions of dollars of
1647 equipment, or even human lives, can be lost if the DetNet QoS is not
1648 delivered, one must consider not only simple equipment failures,
1649 where the box or wire instantly becomes perfectly silent, but complex
1650 errors such as can be caused by software failures. Because there is
1651 essential no limit to the kinds of failures that can occur,
1652 protecting against realistic equipment failures is indistinguishable,
1653 in most cases, from protecting against malicious behavior, whether
1654 accidental or intentional. See also Section 3.3.2.
1656 Security must cover:
1658 o the protection of the signaling protocol
1660 o the authentication and authorization of the controlling systems
1662 o the identification and shaping of the DetNet flows
1664 Security considerations for DetNet are described in detail in
1665 [I-D.ietf-detnet-security].
1667 6. Privacy Considerations
1669 DetNet is provides a Quality of Service (QoS), and as such, does not
1670 directly raise any new privacy considerations.
1672 However, the requirement for every (or almost every) node along the
1673 path of a DetNet flow to identify DetNet flows may present an
1674 additional attack surface for privacy, should the DetNet paradigm be
1675 found useful in broader environments.
1677 7. IANA Considerations
1679 This document does not require an action from IANA.
1681 8. Acknowledgements
1683 The authors wish to thank Lou Berger, David Black, Stewart Bryant,
1684 Rodney Cummings, Ethan Grossman, Craig Gunther, Marcel Kiessling,
1685 Rudy Klecka, Jouni Korhonen, Erik Nordmark, Shitanshu Shah, Wilfried
1686 Steiner, George Swallow, Michael Johas Teener, Pat Thaler, Thomas
1687 Watteyne, Patrick Wetterwald, Karl Weber, Anca Zamfir, for their
1688 various contribution with this work.
1690 9. Informative References
1692 [CCAMP] IETF, "Common Control and Measurement Plane Working
1693 Group",
1694 .
1696 [I-D.ietf-6tisch-architecture]
1697 Thubert, P., "An Architecture for IPv6 over the TSCH mode
1698 of IEEE 802.15.4", draft-ietf-6tisch-architecture-15 (work
1699 in progress), October 2018.
1701 [I-D.ietf-detnet-dp-sol-ip]
1702 Korhonen, J. and B. Varga, "DetNet IP Data Plane
1703 Encapsulation", draft-ietf-detnet-dp-sol-ip-01 (work in
1704 progress), October 2018.
1706 [I-D.ietf-detnet-dp-sol-mpls]
1707 Korhonen, J. and B. Varga, "DetNet MPLS Data Plane
1708 Encapsulation", draft-ietf-detnet-dp-sol-mpls-01 (work in
1709 progress), October 2018.
1711 [I-D.ietf-detnet-problem-statement]
1712 Finn, N. and P. Thubert, "Deterministic Networking Problem
1713 Statement", draft-ietf-detnet-problem-statement-07 (work
1714 in progress), October 2018.
1716 [I-D.ietf-detnet-security]
1717 Mizrahi, T., Grossman, E., Hacker, A., Das, S., Dowdell,
1718 J., Austad, H., Stanton, K., and N. Finn, "Deterministic
1719 Networking (DetNet) Security Considerations", draft-ietf-
1720 detnet-security-03 (work in progress), October 2018.
1722 [I-D.ietf-detnet-use-cases]
1723 Grossman, E., "Deterministic Networking Use Cases", draft-
1724 ietf-detnet-use-cases-19 (work in progress), October 2018.
1726 [IEC62439-3-2016]
1727 International Electrotechnical Commission (IEC) TC 65/SC
1728 65C - Industrial networks, "IEC 62439-3:2016 Industrial
1729 communication networks - High availability automation
1730 networks - Part 3: Parallel Redundancy Protocol (PRP) and
1731 High-availability Seamless Redundancy (HSR)", 2016,
1732 .
1734 [IEEE802.1BA]
1735 IEEE Standards Association, "IEEE Std 802.1BA-2011 Audio
1736 Video Bridging (AVB) Systems", 2011,
1737 .
1739 [IEEE802.1CB]
1740 IEEE Standards Association, "IEEE Std 802.1CB-2017 Frame
1741 Replication and Elimination for Reliability", 2017,
1742 .
1744 [IEEE802.1Q-2018]
1745 IEEE Standards Association, "IEEE Std 802.1Q-2018 Bridges
1746 and Bridged Networks", 2018,
1747 .
1749 [IEEE802.1Qav]
1750 IEEE Standards Association, "IEEE Std 802.1Qav-2009
1751 Bridges and Bridged Networks - Amendment 12: Forwarding
1752 and Queuing Enhancements for Time-Sensitive Streams",
1753 2009, .
1755 [IEEE802.1Qbu]
1756 IEEE Standards Association, "IEEE Std 802.1Qbu-2016
1757 Bridges and Bridged Networks - Amendment 26: Frame
1758 Preemption", 2016,
1759 .
1761 [IEEE802.1Qbv]
1762 IEEE Standards Association, "IEEE Std 802.1Qbv-2015
1763 Bridges and Bridged Networks - Amendment 25: Enhancements
1764 for Scheduled Traffic", 2015,
1765 .
1767 [IEEE802.1Qch]
1768 IEEE Standards Association, "IEEE Std 802.1Qch-2017
1769 Bridges and Bridged Networks - Amendment 29: Cyclic
1770 Queuing and Forwarding", 2017,
1771 .
1773 [IEEE802.1TSNTG]
1774 IEEE Standards Association, "IEEE 802.1 Time-Sensitive
1775 Networking Task Group", 2013,
1776 .
1778 [IEEE802.3-2018]
1779 IEEE Standards Association, "IEEE Std 802.3-2018 Standard
1780 for Ethernet", 2018,
1781 .
1783 [IEEE802.3br]
1784 IEEE Standards Association, "IEEE Std 802.3br-2016
1785 Standard for Ethernet Amendment 5: Specification and
1786 Management Parameters for Interspersing Express Traffic",
1787 2016, .
1789 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
1790 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
1791 Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
1792 September 1997, .
1794 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
1795 and W. Weiss, "An Architecture for Differentiated
1796 Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
1797 .
1799 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
1800 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
1801 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
1802 .
1804 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
1805 Jacobson, "RTP: A Transport Protocol for Real-Time
1806 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
1807 July 2003, .
1809 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
1810 Element (PCE)-Based Architecture", RFC 4655,
1811 DOI 10.17487/RFC4655, August 2006,
1812 .
1814 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
1815 L., and L. Berger, "A Framework for MPLS in Transport
1816 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
1817 .
1819 [RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport
1820 Profile (MPLS-TP) Survivability Framework", RFC 6372,
1821 DOI 10.17487/RFC6372, September 2011,
1822 .
1824 [RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
1825 "Packet Pseudowire Encapsulation over an MPLS PSN",
1826 RFC 6658, DOI 10.17487/RFC6658, July 2012,
1827 .
1829 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
1830 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
1831 October 2014, .
1833 [RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
1834 Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
1835 Defined Networking (SDN): Layers and Architecture
1836 Terminology", RFC 7426, DOI 10.17487/RFC7426, January
1837 2015, .
1839 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
1840 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
1841 Internet of Things (IoT): Problem Statement", RFC 7554,
1842 DOI 10.17487/RFC7554, May 2015,
1843 .
1845 [RFC7813] Farkas, J., Ed., Bragg, N., Unbehagen, P., Parsons, G.,
1846 Ashwood-Smith, P., and C. Bowers, "IS-IS Path Control and
1847 Reservation", RFC 7813, DOI 10.17487/RFC7813, June 2016,
1848 .
1850 [RFC8227] Cheng, W., Wang, L., Li, H., van Helvoort, H., and J.
1851 Dong, "MPLS-TP Shared-Ring Protection (MSRP) Mechanism for
1852 Ring Topology", RFC 8227, DOI 10.17487/RFC8227, August
1853 2017, .
1855 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
1856 Decraene, B., Litkowski, S., and R. Shakir, "Segment
1857 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
1858 July 2018, .
1860 [TEAS] IETF, "Traffic Engineering Architecture and Signaling
1861 Working Group",
1862 .
1864 Authors' Addresses
1866 Norman Finn
1867 Huawei
1868 3101 Rio Way
1869 Spring Valley, California 91977
1870 US
1872 Phone: +1 925 980 6430
1873 Email: norman.finn@mail01.huawei.com
1874 Pascal Thubert
1875 Cisco Systems
1876 Village d'Entreprises Green Side
1877 400, Avenue de Roumanille
1878 Batiment T3
1879 Biot - Sophia Antipolis 06410
1880 FRANCE
1882 Phone: +33 4 97 23 26 34
1883 Email: pthubert@cisco.com
1885 Balazs Varga
1886 Ericsson
1887 Magyar tudosok korutja 11
1888 Budapest 1117
1889 Hungary
1891 Email: balazs.a.varga@ericsson.com
1893 Janos Farkas
1894 Ericsson
1895 Magyar tudosok korutja 11
1896 Budapest 1117
1897 Hungary
1899 Email: janos.farkas@ericsson.com