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2 DetNet B. Varga, Ed.
3 Internet-Draft J. Farkas
4 Intended status: Informational Ericsson
5 Expires: August 23, 2021 A. Malis
6 Malis Consulting
7 S. Bryant
8 Futurewei Technologies
9 February 19, 2021
11 DetNet Data Plane: MPLS over IEEE 802.1 Time-Sensitive Networking (TSN)
12 draft-ietf-detnet-mpls-over-tsn-07
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 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 23, 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 . . . . . . . . . . . . . . . 3
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 rate 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 d-CW DetNet Control Word.
115 DetNet Deterministic Networking.
117 F-Label Forwarding label that identifies the LSP used by a
118 DetNet flow.
120 FRER Frame Replication and Elimination for Redundancy (TSN
121 function).
123 L2 Layer 2.
125 L3 Layer 3.
127 MPLS Multiprotocol Label Switching.
129 PREOF Packet Replication, Elimination and Ordering Functions.
131 PSN Packet Switched Network.
133 PW PseudoWire.
135 RSVP-TE Resource Reservation Protocol - Traffic Engineering.
137 S-Label Service label.
139 TSN Time-Sensitive Network.
141 3. DetNet MPLS Data Plane Overview
143 The basic approach defined in [RFC8964] supports the DetNet service
144 sub-layer based on existing pseudowire (PW) encapsulations and
145 mechanisms, and supports the DetNet forwarding sub-layer based on
146 existing MPLS Traffic Engineering encapsulations and mechanisms.
148 A node operating on a DetNet flow in the Detnet service sub-layer,
149 i.e. a node processing a DetNet packet which has the S-Label as top
150 of stack uses the local context associated with that service label
151 (S-Label), for example a received forwarding label (F-Label), to
152 determine what local DetNet operation(s) are applied to that packet.
153 An S-Label may be unique when taken from the platform label space
154 [RFC3031], which would enable correct DetNet flow identification
155 regardless of which input interface or LSP the packet arrives on.
156 The service sub-layer functions (i.e., PREOF) use a DetNet control
157 word (d-CW).
159 The DetNet MPLS data plane builds on MPLS Traffic Engineering
160 encapsulations and mechanisms to provide a forwarding sub-layer that
161 is responsible for providing resource allocation and explicit routes.
162 The forwarding sub-layer is supported by one or more F-Labels.
164 DetNet edge/relay nodes are DetNet service sub-layer aware,
165 understand the particular needs of DetNet flows and provide both
166 DetNet service and forwarding sub-layer functions. They add, remove
167 and process d-CWs, S-Labels and F-labels as needed. MPLS DetNet
168 nodes and transit nodes include DetNet forwarding sub-layer
169 functions, notably support for explicit routes, and resources
170 allocation to eliminate (or reduce) congestion loss and jitter.
171 Unlike other DetNet node types, transit nodes provide no service sub-
172 layer processing.
174 MPLS (DetNet) nodes and transit nodes interconnected by a TSN sub-
175 network are the primary focus of this document. The mapping of
176 DetNet MPLS flows to TSN streams and TSN protection mechanisms are
177 covered in Section 4.
179 4. DetNet MPLS Operation Over IEEE 802.1 TSN Sub-Networks
181 The DetNet WG collaborates with IEEE 802.1 TSN in order to define a
182 common architecture for both Layer 2 and Layer 3, that maintains
183 consistency across diverse networks. Both DetNet MPLS and TSN use
184 the same techniques to provide their deterministic service:
186 o Service protection.
188 o Resource allocation.
190 o Explicit routes.
192 As described in the DetNet architecture [RFC8655] a sub-network
193 provides from MPLS perspective a single hop connection between MPLS
194 (DetNet) nodes. Functions used for resource allocation and explicit
195 routes are treated as domain internal functions and do not require
196 function interworking across the DetNet MPLS network and the TSN sub-
197 network.
199 In the case of the service protection function due to the
200 similarities of the DetNet PREOF and TSN FRER functions some level of
201 interworking is possible. However, such interworking is out-of-scope
202 in this document and left for further study.
204 Figure 1 illustrates a scenario, where two MPLS (DetNet) nodes are
205 interconnected by a TSN sub-network. Node-1 is single homed and
206 Node-2 is dual-homed to the TSN sub-network.
208 MPLS (DetNet) MPLS (DetNet)
209 Node-1 Node-2
211 +----------+ +----------+
212 <--| Service* |-- DetNet flow ---| Service* |-->
213 +----------+ +----------+
214 |Forwarding| |Forwarding|
215 +--------.-+ <-TSN Str-> +-.-----.--+
216 \ ,-------. / /
217 +----[ TSN-Sub ]---+ /
218 [ Network ]--------+
219 `-------'
220 <---------------- DetNet MPLS --------------->
222 Note: * no service sub-layer required for transit nodes
224 Figure 1: DetNet Enabled MPLS Network Over a TSN Sub-Network
226 At the time of this writing, the Time-Sensitive Networking (TSN) Task
227 Group of the IEEE 802.1 Working Group have defined (and are defining)
228 a number of amendments to [IEEE8021Q] that provide zero congestion
229 loss and bounded latency in bridged networks. Furthermore
230 [IEEE8021CB] defines frame replication and elimination functions for
231 reliability that should prove both compatible with and useful to,
232 DetNet networks. All these functions have to identify flows those
233 require TSN treatment (i.e., applying TSN functions during
234 forwarding).
236 TSN capabilities of the TSN sub-network are made available for MPLS
237 (DetNet) flows via the protocol interworking function defined in
238 Annex C.5 of [IEEE8021CB]. For example, applied on the TSN edge port
239 it can convert an ingress unicast MPLS (DetNet) flow to use a
240 specific Layer-2 multicast destination MAC address and a VLAN, in
241 order to direct the packet through a specific path inside the bridged
242 network. A similar interworking function pair at the other end of
243 the TSN sub-network would restore the packet to its original Layer-2
244 destination MAC address and VLAN.
246 Placement of TSN functions depends on the TSN capabilities of the
247 nodes along the path. MPLS (DetNet) Nodes may or may not support TSN
248 functions. For a given TSN Stream (i.e., DetNet flow) an MPLS
249 (DetNet) node is treated as a Talker or a Listener inside the TSN
250 sub-network.
252 4.1. Functions for DetNet Flow to TSN Stream Mapping
254 Mapping of a DetNet MPLS flow to a TSN Stream is provided via the
255 combination of a passive and an active stream identification function
256 that operate at the frame level. The passive stream identification
257 function is used to catch the MPLS label(s) of a DetNet MPLS flow and
258 the active stream identification function is used to modify the
259 Ethernet header according to the ID of the mapped TSN Stream.
261 Clause 6.8 of [IEEEP8021CBdb] defines a Mask-and-Match Stream
262 identification function that can be used as a passive function for
263 MPLS DetNet flows.
265 Clause 6.6 of [IEEE8021CB] defines an Active Destination MAC and VLAN
266 Stream identification function, what can replace some Ethernet header
267 fields namely (1) the destination MAC-address, (2) the VLAN-ID and
268 (3) priority parameters with alternate values. Replacement is
269 provided for the frame passed down the stack from the upper layers or
270 up the stack from the lower layers.
272 Active Destination MAC and VLAN Stream identification can be used
273 within a Talker to set flow identity or a Listener to recover the
274 original addressing information. It can be used also in a TSN bridge
275 that is providing translation as a proxy service for an End System.
277 4.2. TSN requirements of MPLS DetNet nodes
279 This section covers required behavior of a TSN-aware MPLS (DetNet)
280 node using a TSN sub-network. The implementation of TSN packet
281 processing functions must be compliant with the relevant IEEE 802.1
282 standards.
284 From the TSN sub-network perspective MPLS (DetNet) nodes are treated
285 as Talker or Listener, that may be (1) TSN-unaware or (2) TSN-aware.
287 In cases of TSN-unaware MPLS DetNet nodes the TSN relay nodes within
288 the TSN sub-network must modify the Ethernet encapsulation of the
289 DetNet MPLS flow (e.g., MAC translation, VLAN-ID setting, Sequence
290 number addition, etc.) to allow proper TSN specific handling inside
291 the sub-network. There are no requirements defined for TSN-unaware
292 MPLS DetNet nodes in this document.
294 MPLS (DetNet) nodes being TSN-aware can be treated as a combination
295 of a TSN-unaware Talker/Listener and a TSN-Relay, as shown in
296 Figure 2. In such cases the MPLS (DetNet) node must provide the TSN
297 sub-network specific Ethernet encapsulation over the link(s) towards
298 the sub-network.
300 MPLS (DetNet)
301 Node
302 <---------------------------------->
304 +----------+
305 <--| Service* |-- DetNet flow ------------------
306 +----------+
307 |Forwarding|
308 +----------+ +---------------+
309 | L2 | | L2 Relay with |<--- TSN ---
310 | | | TSN function | Stream
311 +-----.----+ +--.------.---.-+
312 \__________/ \ \______
313 \_________
314 TSN-unaware
315 Talker / TSN-Bridge
316 Listener Relay
317 <----- TSN Sub-network -----
318 <------- TSN-aware Tlk/Lstn ------->
320 Note: * no service sub-layer required for transit nodes
322 Figure 2: MPLS (DetNet) Node with TSN Functions
324 A TSN-aware MPLS (DetNet) node implementation must support the Stream
325 Identification TSN component for recognizing flows.
327 A Stream identification component must be able to instantiate the
328 following functions (1) Active Destination MAC and VLAN Stream
329 identification function, (2) Mask-and-Match Stream identification
330 function and (3) the related managed objects in Clause 9 of
331 [IEEE8021CB] and [IEEEP8021CBdb].
333 A TSN-aware MPLS (DetNet) node implementation must support the
334 Sequencing function and the Sequence encode/decode function as
335 defined in Clause 7.4 and 7.6 of [IEEE8021CB] in order for FRER to be
336 used inside the TSN sub-network.
338 The Sequence encode/decode function must support the Redundancy tag
339 (R-TAG) format as per Clause 7.8 of [IEEE8021CB].
341 A TSN-aware MPLS (DetNet) node implementation must support the Stream
342 splitting function and the Individual recovery function as defined in
343 Clause 7.7 and 7.5 of [IEEE8021CB] in order for that node to be a
344 replication or elimination point for FRER.
346 4.3. Service protection within the TSN sub-network
348 TSN Streams supporting DetNet flows may use Frame Replication and
349 Elimination for Redundancy (FRER) as defined in Clause 8. of
350 [IEEE8021CB] based on the loss service requirements of the TSN
351 Stream, which is derived from the DetNet service requirements of the
352 DetNet mapped flow. The specific operation of FRER is not modified
353 by the use of DetNet and follows [IEEE8021CB].
355 FRER function and the provided service recovery is available only
356 within the TSN sub-network as the TSN Stream-ID and the TSN sequence
357 number are not valid outside the sub-network. An MPLS (DetNet) node
358 represents a L3 border and as such it terminates all related
359 information elements encoded in the L2 frames.
361 As the Stream-ID and the TSN sequence number are paired with the
362 similar MPLS flow parameters, FRER can be combined with PREOF
363 functions. Such service protection interworking scenarios may
364 require to move sequence number fields among TSN (L2) and PW (MPLS)
365 encapsulations and they are left for further study.
367 4.4. Aggregation during DetNet flow to TSN Stream mapping
369 Implementation of this document shall use management and control
370 information to map a DetNet flow to a TSN Stream. N:1 mapping
371 (aggregating DetNet flows in a single TSN Stream) shall be supported.
372 The management or control function that provisions flow mapping shall
373 ensure that adequate resources are allocated and configured to
374 provide proper service requirements of the mapped flows.
376 5. Management and Control Implications
378 DetNet flow and TSN Stream mapping related information are required
379 only for TSN-aware MPLS (DetNet) nodes. From the Data Plane
380 perspective there is no practical difference based on the origin of
381 flow mapping related information (management plane or control plane).
383 The following summarizes the set of information that is needed to
384 configure DetNet MPLS over TSN:
386 o DetNet MPLS related configuration information according to the
387 DetNet role of the DetNet MPLS node, as per [RFC8964].
389 o TSN related configuration information according to the TSN role of
390 the DetNet MPLS node, as per [IEEE8021Q], [IEEE8021CB] and
391 [IEEEP8021CBdb].
393 o Mapping between DetNet MPLS flow(s) (label information: A-labels,
394 S-labels and F-labels as defined in [RFC8964]) and TSN Stream(s)
395 (as stream identification information defined in [IEEEP8021CBdb]).
396 Note, that managed objects for TSN Stream identification can be
397 found in [IEEEP8021CBcv].
399 This information must be provisioned per DetNet flow.
401 Mappings between DetNet and TSN management and control planes are out
402 of scope of the document. Some of the challenges are highlighted
403 below.
405 TSN-aware MPLS DetNet nodes are members of both the DetNet domain and
406 the TSN sub-network. Within the TSN sub-network the TSN-aware MPLS
407 (DetNet) node has a TSN-aware Talker/Listener role, so TSN specific
408 management and control plane functionalities must be implemented.
409 There are many similarities in the management plane techniques used
410 in DetNet and TSN, but that is not the case for the control plane
411 protocols. For example, RSVP-TE and MSRP (Multiple Stream
412 Registration Protocol) behaves differently. Therefore management and
413 control plane design is an important aspect of scenarios, where
414 mapping between DetNet and TSN is required.
416 In order to use a TSN sub-network between DetNet nodes, DetNet
417 specific information must be converted to TSN sub-network specific
418 ones. DetNet flow ID and flow related parameters/requirements must
419 be converted to a TSN Stream ID and stream related parameters/
420 requirements. Note that, as the TSN sub-network is just a portion of
421 the end-2-end DetNet path (i.e., a single hop from MPLS perspective),
422 some parameters (e.g., delay) may differ significantly. Other
423 parameters (like bandwidth) also may have to be tuned due to the L2
424 encapsulation used within the TSN sub-network.
426 In some cases it may be challenging to determine some TSN Stream
427 related information. For example, on a TSN-aware MPLS (DetNet) node
428 that acts as a Talker, it is quite obvious which DetNet node is the
429 Listener of the mapped TSN stream (i.e., the MPLS Next-Hop). However
430 it may be not trivial to locate the point/interface where that
431 Listener is connected to the TSN sub-network. Such attributes may
432 require interaction between control and management plane functions
433 and between DetNet and TSN domains.
435 Mapping between DetNet flow identifiers and TSN Stream identifiers,
436 if not provided explicitly, can be done by a TSN-aware MPLS (DetNet)
437 node locally based on information provided for configuration of the
438 TSN Stream identification functions (Mask-and-match Stream
439 identification and Active Stream identification function).
441 Triggering the setup/modification of a TSN Stream in the TSN sub-
442 network is an example where management and/or control plane
443 interactions are required between the DetNet and TSN sub-network.
444 TSN-unaware MPLS (DetNet) nodes make such a triggering even more
445 complicated as they are fully unaware of the sub-network and run
446 independently.
448 Configuration of TSN specific functions (e.g., FRER) inside the TSN
449 sub-network is a TSN domain specific decision and may not be visible
450 in the DetNet domain. Service protection interworking scenarios are
451 left for further study.
453 6. Security Considerations
455 Security considerations for DetNet are described in detail in
456 [I-D.ietf-detnet-security]. General security considerations are
457 described in [RFC8655]. DetNet MPLS data plane specific
458 considerations are summarized in [RFC8964]. This section considers
459 exclusively security considerations which are specific to the DetNet
460 MPLS over TSN sub-network scenario.
462 The sub-network between DetNet nodes needs to be subject to
463 appropriate confidentiality. Additionally, knowledge of what DetNet/
464 TSN services are provided by a sub-network may supply information
465 that can be used in a variety of security attacks. The ability to
466 modify information exchanges between connected DetNet nodes may
467 result in bogus operations. Therefore, it is important that the
468 interface between DetNet nodes and TSN sub-network are subject to
469 authorization, authentication, and encryption.
471 The TSN sub-network operates at Layer-2 so various security
472 mechanisms defined by IEEE can be used to secure the connection
473 between the DetNet nodes (e.g., encryption may be provided using
474 MACSec [IEEE802.1AE-2018]).
476 7. IANA Considerations
478 This document makes no IANA requests.
480 8. Acknowledgements
482 The authors wish to thank Norman Finn, Lou Berger, Craig Gunther,
483 Christophe Mangin and Jouni Korhonen for their various contributions
484 to this work.
486 9. References
488 9.1. Normative References
490 [IEEE8021CB]
491 IEEE 802.1, "Standard for Local and metropolitan area
492 networks - Frame Replication and Elimination for
493 Reliability (IEEE Std 802.1CB-2017)", 2017,
494 .
496 [IEEEP8021CBdb]
497 Mangin, C., "Extended Stream identification functions",
498 IEEE P802.1CBdb /D1.0 P802.1CBdb, September 2020,
499 .
502 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
503 Label Switching Architecture", RFC 3031,
504 DOI 10.17487/RFC3031, January 2001,
505 .
507 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
508 "Deterministic Networking Architecture", RFC 8655,
509 DOI 10.17487/RFC8655, October 2019,
510 .
512 [RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
513 S., and J. Korhonen, "Deterministic Networking (DetNet)
514 Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
515 2021, .
517 9.2. Informative References
519 [I-D.ietf-detnet-security]
520 Grossman, E., Mizrahi, T., and A. Hacker, "Deterministic
521 Networking (DetNet) Security Considerations", draft-ietf-
522 detnet-security-13 (work in progress), December 2020.
524 [IEEE802.1AE-2018]
525 IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
526 Security (MACsec)", 2018,
527 .
529 [IEEE8021Q]
530 IEEE 802.1, "Standard for Local and metropolitan area
531 networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
532 2018)", 2018, .
534 [IEEEP8021CBcv]
535 Kehrer, S., "FRER YANG Data Model and Management
536 Information Base Module", IEEE P802.1CBcv
537 /D0.4 P802.1CBcv, August 2020,
538 .
541 Authors' Addresses
543 Balazs Varga (editor)
544 Ericsson
545 Magyar Tudosok krt. 11.
546 Budapest 1117
547 Hungary
549 Email: balazs.a.varga@ericsson.com
551 Janos Farkas
552 Ericsson
553 Magyar Tudosok krt. 11.
554 Budapest 1117
555 Hungary
557 Email: janos.farkas@ericsson.com
559 Andrew G. Malis
560 Malis Consulting
562 Email: agmalis@gmail.com
564 Stewart Bryant
565 Futurewei Technologies
567 Email: stewart.bryant@gmail.com