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2 DetNet B. Varga, Ed.
3 Internet-Draft J. Farkas
4 Intended status: Informational Ericsson
5 Expires: August 16, 2021 A. Malis
6 Malis Consulting
7 S. Bryant
8 Futurewei Technologies
9 February 12, 2021
11 DetNet Data Plane: MPLS over IEEE 802.1 Time-Sensitive Networking (TSN)
12 draft-ietf-detnet-mpls-over-tsn-06
14 Abstract
16 This document specifies the Deterministic Networking MPLS data plane
17 when operating over an IEEE 802.1 Time-Sensitive Networking (TSN)
18 sub-network. This document does not define new procedures or
19 processes. Whenever this document makes requirements statements or
20 recommendations, these are taken from normative text in the
21 referenced RFCs.
23 Status of This Memo
25 This Internet-Draft is submitted in full conformance with the
26 provisions of BCP 78 and BCP 79.
28 Internet-Drafts are working documents of the Internet Engineering
29 Task Force (IETF). Note that other groups may also distribute
30 working documents as Internet-Drafts. The list of current Internet-
31 Drafts is at https://datatracker.ietf.org/drafts/current/.
33 Internet-Drafts are draft documents valid for a maximum of six months
34 and may be updated, replaced, or obsoleted by other documents at any
35 time. It is inappropriate to use Internet-Drafts as reference
36 material or to cite them other than as "work in progress."
38 This Internet-Draft will expire on August 16, 2021.
40 Copyright Notice
42 Copyright (c) 2021 IETF Trust and the persons identified as the
43 document authors. All rights reserved.
45 This document is subject to BCP 78 and the IETF Trust's Legal
46 Provisions Relating to IETF Documents
47 (https://trustee.ietf.org/license-info) in effect on the date of
48 publication of this document. Please review these documents
49 carefully, as they describe your rights and restrictions with respect
50 to this document. Code Components extracted from this document must
51 include Simplified BSD License text as described in Section 4.e of
52 the Trust Legal Provisions and are provided without warranty as
53 described in the Simplified BSD License.
55 Table of Contents
57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
59 2.1. Terms Used in This Document . . . . . . . . . . . . . . . 3
60 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
61 3. DetNet MPLS Data Plane Overview . . . . . . . . . . . . . . . 4
62 4. DetNet MPLS Operation Over IEEE 802.1 TSN Sub-Networks . . . 4
63 4.1. Functions for DetNet Flow to TSN Stream Mapping . . . . . 6
64 4.2. TSN requirements of MPLS DetNet nodes . . . . . . . . . . 6
65 4.3. Service protection within the TSN sub-network . . . . . . 8
66 4.4. Aggregation during DetNet flow to TSN Stream mapping . . 8
67 5. Management and Control Implications . . . . . . . . . . . . . 8
68 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
69 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
70 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
71 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
72 9.1. Normative References . . . . . . . . . . . . . . . . . . 11
73 9.2. Informative References . . . . . . . . . . . . . . . . . 11
74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
76 1. Introduction
78 Deterministic Networking (DetNet) is a service that can be offered by
79 a network to DetNet flows. DetNet provides these flows with low
80 packet loss rates and assured maximum end-to-end delivery latency.
81 General background and concepts of DetNet can be found in [RFC8655].
83 The DetNet Architecture decomposes the DetNet related data plane
84 functions into two sub-layers: a service sub-layer and a forwarding
85 sub-layer. The service sub-layer is used to provide DetNet service
86 protection and reordering. The forwarding sub-layer is used to
87 provide congestion protection (low loss, assured latency, and limited
88 reordering) leveraging MPLS Traffic Engineering mechanisms.
90 [RFC8964] specifies the DetNet data plane operation for MPLS-based
91 Packet Switched Network (PSN). MPLS encapsulated DetNet flows can be
92 carried over network technologies that can provide the DetNet
93 required level of service. This document focuses on the scenario
94 where MPLS (DetNet) nodes are interconnected by a IEEE 802.1 TSN sub-
95 network. There is close cooperation between the IETF DetNet WG and
96 the IEEE 802.1 TSN TG.
98 2. Terminology
100 2.1. Terms Used in This Document
102 This document uses the terminology established in the DetNet
103 architecture [RFC8655] and [RFC8964]. TSN specific terms are defined
104 in the TSN TG of IEEE 802.1 Working Group. The reader is assumed to
105 be familiar with these documents and their terminology.
107 2.2. Abbreviations
109 The following abbreviations are used in this document:
111 A-Label Aggregation label, a special case of an S-Label.
113 CW Control Word.
115 DetNet Deterministic Networking.
117 DF DetNet Flow.
119 F-Label Forwarding label that identifies the LSP used by a
120 DetNet flow.
122 FRER Frame Replication and Elimination for Redundancy (TSN
123 function).
125 L2 Layer 2.
127 L3 Layer 3.
129 LSR Label Switching Router.
131 MPLS Multiprotocol Label Switching.
133 PE Provider Edge.
135 PREOF Packet Replication, Elimination and Ordering Functions.
137 PSN Packet Switched Network.
139 PW PseudoWire.
141 S-PE Switching Provider Edge.
143 S-Label Service label.
145 T-PE Terminating Provider Edge.
147 TSN Time-Sensitive Network.
149 3. DetNet MPLS Data Plane Overview
151 The basic approach defined in [RFC8964] supports the DetNet service
152 sub-layer based on existing pseudowire (PW) encapsulations and
153 mechanisms, and supports the DetNet forwarding sub-layer based on
154 existing MPLS Traffic Engineering encapsulations and mechanisms.
156 A node operating on a DetNet flow in the Detnet service sub-layer,
157 i.e. a node processing a DetNet packet which has the S-Label as top
158 of stack uses the local context associated with that service label
159 (S-Label), for example a received forwarding label (F-Label), to
160 determine what local DetNet operation(s) are applied to that packet.
161 An S-Label may be unique when taken from the platform label space
162 [RFC3031], which would enable correct DetNet flow identification
163 regardless of which input interface or LSP the packet arrives on.
164 The service sub-layer functions (i.e., PREOF) use a DetNet control
165 word (d-CW).
167 The DetNet MPLS data plane builds on MPLS Traffic Engineering
168 encapsulations and mechanisms to provide a forwarding sub-layer that
169 is responsible for providing resource allocation and explicit routes.
170 The forwarding sub-layer is supported by one or more F-Labels.
172 DetNet edge/relay nodes are DetNet service sub-layer aware,
173 understand the particular needs of DetNet flows and provide both
174 DetNet service and forwarding sub-layer functions. They add, remove
175 and process d-CWs, S-Labels and F-labels as needed. MPLS DetNet
176 nodes and transit nodes include DetNet forwarding sub-layer
177 functions, support for notably explicit routes, and resources
178 allocation to eliminate (or reduce) congestion loss and jitter.
179 Unlike other DetNet node types, transit nodes provide no service sub-
180 layer processing.
182 MPLS (DetNet) nodes and transit nodes interconnected by a TSN sub-
183 network are the primary focus of this document. The mapping of
184 DetNet MPLS flows to TSN streams and TSN protection mechanisms are
185 covered in Section 4.
187 4. DetNet MPLS Operation Over IEEE 802.1 TSN Sub-Networks
189 The DetNet WG collaborates with IEEE 802.1 TSN in order to define a
190 common architecture for both Layer 2 and Layer 3, that maintains
191 consistency across diverse networks. Both DetNet MPLS and TSN use
192 the same techniques to provide their deterministic service:
194 o Service protection.
196 o Resource allocation.
198 o Explicit routes.
200 As described in the DetNet architecture [RFC8655] a sub-network
201 provides from MPLS perspective a single hop connection between MPLS
202 (DetNet) nodes. Functions used for resource allocation and explicit
203 routes are treated as domain internal functions and does not require
204 function interworking across the DetNet MPLS network and the TSN sub-
205 network.
207 In case of the service protection function due to the similarities of
208 the DetNet PREOF and TSN FRER functions some level of interworking is
209 possible. However, such interworking is out-of-scope in this
210 document and left for further study.
212 Figure 1 illustrates a scenario, where two MPLS (DetNet) nodes are
213 interconnected by a TSN sub-network. Node-1 is single homed and
214 Node-2 is dual-homed to the TSN sub-network.
216 MPLS (DetNet) MPLS (DetNet)
217 Node-1 Node-2
219 +----------+ +----------+
220 <--| Service* |-- DetNet flow ---| Service* |-->
221 +----------+ +----------+
222 |Forwarding| |Forwarding|
223 +--------.-+ <-TSN Str-> +-.-----.--+
224 \ ,-------. / /
225 +----[ TSN-Sub ]---+ /
226 [ Network ]--------+
227 `-------'
228 <---------------- DetNet MPLS --------------->
230 Note: * no service sub-layer required for transit nodes
232 Figure 1: DetNet Enabled MPLS Network Over a TSN Sub-Network
234 The Time-Sensitive Networking (TSN) Task Group of the IEEE 802.1
235 Working Group have defined (and are defining) a number of amendments
236 to IEEE 802.1Q [IEEE8021Q] that provide zero congestion loss and
237 bounded latency in bridged networks. Furthermore IEEE 802.1CB
238 [IEEE8021CB] defines frame replication and elimination functions for
239 reliability that should prove both compatible with and useful to,
240 DetNet networks. All these functions have to identify flows those
241 require TSN treatment (i.e., applying TSN functions during
242 forwarding).
244 TSN capabilities of the TSN sub-network are made available for MPLS
245 (DetNet) flows via the protocol interworking function defined in
246 Annex C.5 of IEEE 802.1CB [IEEE8021CB]. For example, applied on the
247 TSN edge port it can convert an ingress unicast MPLS (DetNet) flow to
248 use a specific Layer-2 multicast destination MAC address and a VLAN,
249 in order to direct the packet through a specific path inside the
250 bridged network. A similar interworking function pair at the other
251 end of the TSN sub-network would restore the packet to its original
252 Layer-2 destination MAC address and VLAN.
254 Placement of TSN functions depends on the TSN capabilities of the
255 nodes along the path. MPLS (DetNet) Nodes may or may not support TSN
256 functions. For a given TSN Stream (i.e., DetNet flow) an MPLS
257 (DetNet) node is treated as a Talker or a Listener inside the TSN
258 sub-network.
260 4.1. Functions for DetNet Flow to TSN Stream Mapping
262 Mapping of a DetNet MPLS flow to a TSN Stream is provided via the
263 combination of a passive and an active stream identification function
264 that operate at the frame level. The passive stream identification
265 function is used to catch the MPLS label(s) of a DetNet MPLS flow and
266 the active stream identification function is used to modify the
267 Ethernet header according to the ID of the mapped TSN Stream.
269 Clause 6.8 of IEEE P802.1CBdb [IEEEP8021CBdb] defines a Mask-and-
270 Match Stream identification function that can be used as a passive
271 function for MPLS DetNet flows.
273 Clause 6.6 of IEEE 802.1CB [IEEE8021CB] defines an Active Destination
274 MAC and VLAN Stream identification function, what can replace some
275 Ethernet header fields namely (1) the destination MAC-address, (2)
276 the VLAN-ID and (3) priority parameters with alternate values.
277 Replacement is provided for the frame passed down the stack from the
278 upper layers or up the stack from the lower layers.
280 Active Destination MAC and VLAN Stream identification can be used
281 within a Talker to set flow identity or a Listener to recover the
282 original addressing information. It can be used also in a TSN bridge
283 that is providing translation as a proxy service for an End System.
285 4.2. TSN requirements of MPLS DetNet nodes
287 This section covers required behavior of a TSN-aware MPLS (DetNet)
288 node using a TSN sub-network. The implementation of TSN packet
289 processing functions must be compliant with the relevant IEEE 802.1
290 standards.
292 From the TSN sub-network perspective MPLS (DetNet) nodes are treated
293 as Talker or Listener, that may be (1) TSN-unaware or (2) TSN-aware.
295 In cases of TSN-unaware MPLS DetNet nodes the TSN relay nodes within
296 the TSN sub-network must modify the Ethernet encapsulation of the
297 DetNet MPLS flow (e.g., MAC translation, VLAN-ID setting, Sequence
298 number addition, etc.) to allow proper TSN specific handling inside
299 the sub-network. There are no requirements defined for TSN-unaware
300 MPLS DetNet nodes in this document.
302 MPLS (DetNet) nodes being TSN-aware can be treated as a combination
303 of a TSN-unaware Talker/Listener and a TSN-Relay, as shown in
304 Figure 2. In such cases the MPLS (DetNet) node must provide the TSN
305 sub-network specific Ethernet encapsulation over the link(s) towards
306 the sub-network.
308 MPLS (DetNet)
309 Node
310 <---------------------------------->
312 +----------+
313 <--| Service* |-- DetNet flow ------------------
314 +----------+
315 |Forwarding|
316 +----------+ +---------------+
317 | L2 | | L2 Relay with |<--- TSN ---
318 | | | TSN function | Stream
319 +-----.----+ +--.------.---.-+
320 \__________/ \ \______
321 \_________
322 TSN-unaware
323 Talker / TSN-Bridge
324 Listener Relay
325 <----- TSN Sub-network -----
326 <------- TSN-aware Tlk/Lstn ------->
328 Note: * no service sub-layer required for transit nodes
330 Figure 2: MPLS (DetNet) Node with TSN Functions
332 A TSN-aware MPLS (DetNet) node implementation must support the Stream
333 Identification TSN component for recognizing flows.
335 A Stream identification component must be able to instantiate the
336 following functions (1) Active Destination MAC and VLAN Stream
337 identification function, (2) Mask-and-Match Stream identification
338 function and (3) the related managed objects in Clause 9 of IEEE
339 802.1CB [IEEE8021CB] and IEEE P802.1CBdb [IEEEP8021CBdb].
341 A TSN-aware MPLS (DetNet) node implementation must support the
342 Sequencing function and the Sequence encode/decode function as
343 defined in Clause 7.4 and 7.6 of IEEE 802.1CB [IEEE8021CB] if FRER is
344 used inside the TSN sub-network.
346 The Sequence encode/decode function must support the Redundancy tag
347 (R-TAG) format as per Clause 7.8 of IEEE 802.1CB [IEEE8021CB].
349 A TSN-aware MPLS (DetNet) node implementation must support the Stream
350 splitting function and the Individual recovery function as defined in
351 Clause 7.7 and 7.5 of IEEE 802.1CB [IEEE8021CB] when the node is a
352 replication or elimination point for FRER.
354 4.3. Service protection within the TSN sub-network
356 TSN Streams supporting DetNet flows may use Frame Replication and
357 Elimination for Redundancy (FRER) as defined in Clause 8. of IEEE
358 802.1CB [IEEE8021CB] based on the loss service requirements of the
359 TSN Stream, which is derived from the DetNet service requirements of
360 the DetNet mapped flow. The specific operation of FRER is not
361 modified by the use of DetNet and follows IEEE 802.1CB [IEEE8021CB].
363 FRER function and the provided service recovery is available only
364 within the TSN sub-network as the TSN Stream-ID and the TSN sequence
365 number are not valid outside the sub-network. An MPLS (DetNet) node
366 represents a L3 border and as such it terminates all related
367 information elements encoded in the L2 frames.
369 As the Stream-ID and the TSN sequence number are paired with the
370 similar MPLS flow parameters, FRER can be combined with PREOF
371 functions. Such service protection interworking scenarios may
372 require to move sequence number fields among TSN (L2) and PW (MPLS)
373 encapsulations and they are left for further study.
375 4.4. Aggregation during DetNet flow to TSN Stream mapping
377 Implementations of this document shall use management and control
378 information to map a DetNet flow to a TSN Stream. N:1 mapping
379 (aggregating DetNet flows in a single TSN Stream) shall be supported.
380 The management or control function that provisions flow mapping shall
381 ensure that adequate resources are allocated and configured to
382 provide proper service requirements of the mapped flows.
384 5. Management and Control Implications
386 DetNet flow and TSN Stream mapping related information are required
387 only for TSN-aware MPLS (DetNet) nodes. From the Data Plane
388 perspective there is no practical difference based on the origin of
389 flow mapping related information (management plane or control plane).
391 The following summarizes the set of information that is needed to
392 configure DetNet MPLS over TSN:
394 o DetNet MPLS related configuration information according to the
395 DetNet role of the DetNet MPLS node, as per [RFC8964].
397 o TSN related configuration information according to the TSN role of
398 the DetNet MPLS node, as per [IEEE8021Q], [IEEE8021CB] and
399 [IEEEP8021CBdb].
401 o Mapping between DetNet MPLS flow(s) (label information: A-labels,
402 S-labels and F-labels as defined in [RFC8964]) and TSN Stream(s)
403 (as stream identification information defined in [IEEEP8021CBdb]).
404 Note, that managed objects for TSN Stream identification can be
405 found in [IEEEP8021CBcv].
407 This information must be provisioned per DetNet flow.
409 Mappings between DetNet and TSN management and control planes are out
410 of scope of the document. Some of the challenges are highlighted
411 below.
413 TSN-aware MPLS DetNet nodes are member of both the DetNet domain and
414 the TSN sub-network. Within the TSN sub-network the TSN-aware MPLS
415 (DetNet) node has a TSN-aware Talker/Listener role, so TSN specific
416 management and control plane functionalities must be implemented.
417 There are many similarities in the management plane techniques used
418 in DetNet and TSN, but that is not the case for the control plane
419 protocols. For example, RSVP-TE and MSRP behaves differently.
420 Therefore management and control plane design is an important aspect
421 of scenarios, where mapping between DetNet and TSN is required.
423 In order to use a TSN sub-network between DetNet nodes, DetNet
424 specific information must be converted to TSN sub-network specific
425 ones. DetNet flow ID and flow related parameters/requirements must
426 be converted to a TSN Stream ID and stream related parameters/
427 requirements. Note that, as the TSN sub-network is just a portion of
428 the end2end DetNet path (i.e., single hop from MPLS perspective),
429 some parameters (e.g., delay) may differ significantly. Other
430 parameters (like bandwidth) also may have to be tuned due to the L2
431 encapsulation used within the TSN sub-network.
433 In some case it may be challenging to determine some TSN Stream
434 related information. For example, on a TSN-aware MPLS (DetNet) node
435 that acts as a Talker, it is quite obvious which DetNet node is the
436 Listener of the mapped TSN stream (i.e., the MPLS Next-Hop). However
437 it may be not trivial to locate the point/interface where that
438 Listener is connected to the TSN sub-network. Such attributes may
439 require interaction between control and management plane functions
440 and between DetNet and TSN domains.
442 Mapping between DetNet flow identifiers and TSN Stream identifiers,
443 if not provided explicitly, can be done by a TSN-aware MPLS (DetNet)
444 node locally based on information provided for configuration of the
445 TSN Stream identification functions (Mask-and-match Stream
446 identification and Active Stream identification function).
448 Triggering the setup/modification of a TSN Stream in the TSN sub-
449 network is an example where management and/or control plane
450 interactions are required between the DetNet and TSN sub-network.
451 TSN-unaware MPLS (DetNet) nodes make such a triggering even more
452 complicated as they are fully unaware of the sub-network and run
453 independently.
455 Configuration of TSN specific functions (e.g., FRER) inside the TSN
456 sub-network is a TSN domain specific decision and may not be visible
457 in the DetNet domain. Service protection interworking scenarios are
458 left for further study.
460 6. Security Considerations
462 Security considerations for DetNet are described in detail in
463 [I-D.ietf-detnet-security]. General security considerations are
464 described in [RFC8655]. DetNet MPLS data plane specific
465 considerations are summarized in [RFC8964]. This section considers
466 exclusively security considerations which are specific to the DetNet
467 MPLS over TSN sub-network scenario.
469 The sub-network between DetNet nodes needs to be subject to
470 appropriate confidentiality. Additionally, knowledge of what DetNet/
471 TSN services are provided by a sub-network may supply information
472 that can be used in a variety of security attacks. The ability to
473 modify information exchanges between connected DetNet nodes may
474 result in bogus operations. Therefore, it is important that the
475 interface between DetNet nodes and TSN sub-network are subject to
476 authorization, authentication, and encryption.
478 The TSN sub-network operates at Layer-2 so various security
479 mechanisms defined by IEEE can be used to secure the connection
480 between the DetNet nodes (e.g., encryption may be provided using
481 MACSec [IEEE802.1AE-2018]).
483 7. IANA Considerations
485 This document makes no IANA requests.
487 8. Acknowledgements
489 The authors wish to thank Norman Finn, Lou Berger, Craig Gunther,
490 Christophe Mangin and Jouni Korhonen for their various contributions
491 to this work.
493 9. References
495 9.1. Normative References
497 [IEEE8021CB]
498 IEEE 802.1, "Standard for Local and metropolitan area
499 networks - Frame Replication and Elimination for
500 Reliability (IEEE Std 802.1CB-2017)", 2017,
501 .
503 [IEEEP8021CBdb]
504 Mangin, C., "Extended Stream identification functions",
505 IEEE P802.1CBdb /D1.0 P802.1CBdb, September 2020,
506 .
509 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
510 Label Switching Architecture", RFC 3031,
511 DOI 10.17487/RFC3031, January 2001,
512 .
514 [RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
515 S., and J. Korhonen, "Deterministic Networking (DetNet)
516 Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
517 2021, .
519 9.2. Informative References
521 [I-D.ietf-detnet-security]
522 Grossman, E., Mizrahi, T., and A. Hacker, "Deterministic
523 Networking (DetNet) Security Considerations", draft-ietf-
524 detnet-security-13 (work in progress), December 2020.
526 [IEEE802.1AE-2018]
527 IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
528 Security (MACsec)", 2018,
529 .
531 [IEEE8021Q]
532 IEEE 802.1, "Standard for Local and metropolitan area
533 networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
534 2018)", 2018, .
536 [IEEEP8021CBcv]
537 Kehrer, S., "FRER YANG Data Model and Management
538 Information Base Module", IEEE P802.1CBcv
539 /D0.4 P802.1CBcv, August 2020,
540 .
543 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
544 "Deterministic Networking Architecture", RFC 8655,
545 DOI 10.17487/RFC8655, October 2019,
546 .
548 Authors' Addresses
550 Balazs Varga (editor)
551 Ericsson
552 Magyar Tudosok krt. 11.
553 Budapest 1117
554 Hungary
556 Email: balazs.a.varga@ericsson.com
558 Janos Farkas
559 Ericsson
560 Magyar Tudosok krt. 11.
561 Budapest 1117
562 Hungary
564 Email: janos.farkas@ericsson.com
566 Andrew G. Malis
567 Malis Consulting
569 Email: agmalis@gmail.com
571 Stewart Bryant
572 Futurewei Technologies
574 Email: stewart.bryant@gmail.com