DetNet Data Plane: MPLS over IEEE 802.1 Time-Sensitive Networking (TSN)
draft-ietf-detnet-mpls-over-tsn-07
| Document | Type | Active Internet-Draft (detnet WG) | ||
|---|---|---|---|---|
| Authors | Balazs Varga , János Farkas , Andy Malis , Stewart Bryant | |||
| Last updated | 2021-03-01 (latest revision 2021-02-19) | |||
| Stream | Internet Engineering Task Force (IETF) | |||
| Intended RFC status | Informational | |||
| Formats | plain text xml pdf htmlized (tools) htmlized bibtex | |||
| Reviews | ||||
| Stream | WG state | Submitted to IESG for Publication | ||
| Document shepherd | Lou Berger | |||
| Shepherd write-up | Show (last changed 2020-12-22) | |||
| IESG | IESG state | RFC Ed Queue | ||
| Action Holders |
(None)
|
|||
| Consensus Boilerplate | Yes | |||
| Telechat date | ||||
| Responsible AD | Deborah Brungard | |||
| Send notices to | Lou Berger <lberger@labn.net> | |||
| IANA | IANA review state | IANA OK - No Actions Needed | ||
| IANA action state | No IANA Actions | |||
| RFC Editor | RFC Editor state | RFC-EDITOR | ||
| Details | ||||
DetNet B. Varga, Ed.
Internet-Draft J. Farkas
Intended status: Informational Ericsson
Expires: August 23, 2021 A. Malis
Malis Consulting
S. Bryant
Futurewei Technologies
February 19, 2021
DetNet Data Plane: MPLS over IEEE 802.1 Time-Sensitive Networking (TSN)
draft-ietf-detnet-mpls-over-tsn-07
Abstract
This document specifies the Deterministic Networking MPLS data plane
when operating over an IEEE 802.1 Time-Sensitive Networking (TSN)
sub-network. This document does not define new procedures or
processes. Whenever this document makes statements or
recommendations, these are taken from normative text in the
referenced RFCs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 23, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Terms Used in This Document . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
3. DetNet MPLS Data Plane Overview . . . . . . . . . . . . . . . 3
4. DetNet MPLS Operation Over IEEE 802.1 TSN Sub-Networks . . . 4
4.1. Functions for DetNet Flow to TSN Stream Mapping . . . . . 6
4.2. TSN requirements of MPLS DetNet nodes . . . . . . . . . . 6
4.3. Service protection within the TSN sub-network . . . . . . 8
4.4. Aggregation during DetNet flow to TSN Stream mapping . . 8
5. Management and Control Implications . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Deterministic Networking (DetNet) is a service that can be offered by
a network to DetNet flows. DetNet provides these flows with low
packet loss rate and assured maximum end-to-end delivery latency.
General background and concepts of DetNet can be found in [RFC8655].
The DetNet Architecture decomposes the DetNet related data plane
functions into two sub-layers: a service sub-layer and a forwarding
sub-layer. The service sub-layer is used to provide DetNet service
protection and reordering. The forwarding sub-layer is used to
provide congestion protection (low loss, assured latency, and limited
reordering) leveraging MPLS Traffic Engineering mechanisms.
[RFC8964] specifies the DetNet data plane operation for MPLS-based
Packet Switched Network (PSN). MPLS encapsulated DetNet flows can be
carried over network technologies that can provide the DetNet
required level of service. This document focuses on the scenario
where MPLS (DetNet) nodes are interconnected by a IEEE 802.1 TSN sub-
network. There is close cooperation between the IETF DetNet WG and
the IEEE 802.1 TSN TG.
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2. Terminology
2.1. Terms Used in This Document
This document uses the terminology established in the DetNet
architecture [RFC8655] and [RFC8964]. TSN specific terms are defined
in the TSN TG of IEEE 802.1 Working Group. The reader is assumed to
be familiar with these documents and their terminology.
2.2. Abbreviations
The following abbreviations are used in this document:
A-Label Aggregation label, a special case of an S-Label.
d-CW DetNet Control Word.
DetNet Deterministic Networking.
F-Label Forwarding label that identifies the LSP used by a
DetNet flow.
FRER Frame Replication and Elimination for Redundancy (TSN
function).
L2 Layer 2.
L3 Layer 3.
MPLS Multiprotocol Label Switching.
PREOF Packet Replication, Elimination and Ordering Functions.
PSN Packet Switched Network.
PW PseudoWire.
RSVP-TE Resource Reservation Protocol - Traffic Engineering.
S-Label Service label.
TSN Time-Sensitive Network.
3. DetNet MPLS Data Plane Overview
The basic approach defined in [RFC8964] supports the DetNet service
sub-layer based on existing pseudowire (PW) encapsulations and
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mechanisms, and supports the DetNet forwarding sub-layer based on
existing MPLS Traffic Engineering encapsulations and mechanisms.
A node operating on a DetNet flow in the Detnet service sub-layer,
i.e. a node processing a DetNet packet which has the S-Label as top
of stack uses the local context associated with that service label
(S-Label), for example a received forwarding label (F-Label), to
determine what local DetNet operation(s) are applied to that packet.
An S-Label may be unique when taken from the platform label space
[RFC3031], which would enable correct DetNet flow identification
regardless of which input interface or LSP the packet arrives on.
The service sub-layer functions (i.e., PREOF) use a DetNet control
word (d-CW).
The DetNet MPLS data plane builds on MPLS Traffic Engineering
encapsulations and mechanisms to provide a forwarding sub-layer that
is responsible for providing resource allocation and explicit routes.
The forwarding sub-layer is supported by one or more F-Labels.
DetNet edge/relay nodes are DetNet service sub-layer aware,
understand the particular needs of DetNet flows and provide both
DetNet service and forwarding sub-layer functions. They add, remove
and process d-CWs, S-Labels and F-labels as needed. MPLS DetNet
nodes and transit nodes include DetNet forwarding sub-layer
functions, notably support for explicit routes, and resources
allocation to eliminate (or reduce) congestion loss and jitter.
Unlike other DetNet node types, transit nodes provide no service sub-
layer processing.
MPLS (DetNet) nodes and transit nodes interconnected by a TSN sub-
network are the primary focus of this document. The mapping of
DetNet MPLS flows to TSN streams and TSN protection mechanisms are
covered in Section 4.
4. DetNet MPLS Operation Over IEEE 802.1 TSN Sub-Networks
The DetNet WG collaborates with IEEE 802.1 TSN in order to define a
common architecture for both Layer 2 and Layer 3, that maintains
consistency across diverse networks. Both DetNet MPLS and TSN use
the same techniques to provide their deterministic service:
o Service protection.
o Resource allocation.
o Explicit routes.
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As described in the DetNet architecture [RFC8655] a sub-network
provides from MPLS perspective a single hop connection between MPLS
(DetNet) nodes. Functions used for resource allocation and explicit
routes are treated as domain internal functions and do not require
function interworking across the DetNet MPLS network and the TSN sub-
network.
In the case of the service protection function due to the
similarities of the DetNet PREOF and TSN FRER functions some level of
interworking is possible. However, such interworking is out-of-scope
in this document and left for further study.
Figure 1 illustrates a scenario, where two MPLS (DetNet) nodes are
interconnected by a TSN sub-network. Node-1 is single homed and
Node-2 is dual-homed to the TSN sub-network.
MPLS (DetNet) MPLS (DetNet)
Node-1 Node-2
+----------+ +----------+
<--| Service* |-- DetNet flow ---| Service* |-->
+----------+ +----------+
|Forwarding| |Forwarding|
+--------.-+ <-TSN Str-> +-.-----.--+
\ ,-------. / /
+----[ TSN-Sub ]---+ /
[ Network ]--------+
`-------'
<---------------- DetNet MPLS --------------->
Note: * no service sub-layer required for transit nodes
Figure 1: DetNet Enabled MPLS Network Over a TSN Sub-Network
At the time of this writing, the Time-Sensitive Networking (TSN) Task
Group of the IEEE 802.1 Working Group have defined (and are defining)
a number of amendments to [IEEE8021Q] that provide zero congestion
loss and bounded latency in bridged networks. Furthermore
[IEEE8021CB] defines frame replication and elimination functions for
reliability that should prove both compatible with and useful to,
DetNet networks. All these functions have to identify flows those
require TSN treatment (i.e., applying TSN functions during
forwarding).
TSN capabilities of the TSN sub-network are made available for MPLS
(DetNet) flows via the protocol interworking function defined in
Annex C.5 of [IEEE8021CB]. For example, applied on the TSN edge port
it can convert an ingress unicast MPLS (DetNet) flow to use a
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specific Layer-2 multicast destination MAC address and a VLAN, in
order to direct the packet through a specific path inside the bridged
network. A similar interworking function pair at the other end of
the TSN sub-network would restore the packet to its original Layer-2
destination MAC address and VLAN.
Placement of TSN functions depends on the TSN capabilities of the
nodes along the path. MPLS (DetNet) Nodes may or may not support TSN
functions. For a given TSN Stream (i.e., DetNet flow) an MPLS
(DetNet) node is treated as a Talker or a Listener inside the TSN
sub-network.
4.1. Functions for DetNet Flow to TSN Stream Mapping
Mapping of a DetNet MPLS flow to a TSN Stream is provided via the
combination of a passive and an active stream identification function
that operate at the frame level. The passive stream identification
function is used to catch the MPLS label(s) of a DetNet MPLS flow and
the active stream identification function is used to modify the
Ethernet header according to the ID of the mapped TSN Stream.
Clause 6.8 of [IEEEP8021CBdb] defines a Mask-and-Match Stream
identification function that can be used as a passive function for
MPLS DetNet flows.
Clause 6.6 of [IEEE8021CB] defines an Active Destination MAC and VLAN
Stream identification function, what can replace some Ethernet header
fields namely (1) the destination MAC-address, (2) the VLAN-ID and
(3) priority parameters with alternate values. Replacement is
provided for the frame passed down the stack from the upper layers or
up the stack from the lower layers.
Active Destination MAC and VLAN Stream identification can be used
within a Talker to set flow identity or a Listener to recover the
original addressing information. It can be used also in a TSN bridge
that is providing translation as a proxy service for an End System.
4.2. TSN requirements of MPLS DetNet nodes
This section covers required behavior of a TSN-aware MPLS (DetNet)
node using a TSN sub-network. The implementation of TSN packet
processing functions must be compliant with the relevant IEEE 802.1
standards.
From the TSN sub-network perspective MPLS (DetNet) nodes are treated
as Talker or Listener, that may be (1) TSN-unaware or (2) TSN-aware.
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In cases of TSN-unaware MPLS DetNet nodes the TSN relay nodes within
the TSN sub-network must modify the Ethernet encapsulation of the
DetNet MPLS flow (e.g., MAC translation, VLAN-ID setting, Sequence
number addition, etc.) to allow proper TSN specific handling inside
the sub-network. There are no requirements defined for TSN-unaware
MPLS DetNet nodes in this document.
MPLS (DetNet) nodes being TSN-aware can be treated as a combination
of a TSN-unaware Talker/Listener and a TSN-Relay, as shown in
Figure 2. In such cases the MPLS (DetNet) node must provide the TSN
sub-network specific Ethernet encapsulation over the link(s) towards
the sub-network.
MPLS (DetNet)
Node
<---------------------------------->
+----------+
<--| Service* |-- DetNet flow ------------------
+----------+
|Forwarding|
+----------+ +---------------+
| L2 | | L2 Relay with |<--- TSN ---
| | | TSN function | Stream
+-----.----+ +--.------.---.-+
\__________/ \ \______
\_________
TSN-unaware
Talker / TSN-Bridge
Listener Relay
<----- TSN Sub-network -----
<------- TSN-aware Tlk/Lstn ------->
Note: * no service sub-layer required for transit nodes
Figure 2: MPLS (DetNet) Node with TSN Functions
A TSN-aware MPLS (DetNet) node implementation must support the Stream
Identification TSN component for recognizing flows.
A Stream identification component must be able to instantiate the
following functions (1) Active Destination MAC and VLAN Stream
identification function, (2) Mask-and-Match Stream identification
function and (3) the related managed objects in Clause 9 of
[IEEE8021CB] and [IEEEP8021CBdb].
A TSN-aware MPLS (DetNet) node implementation must support the
Sequencing function and the Sequence encode/decode function as
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defined in Clause 7.4 and 7.6 of [IEEE8021CB] in order for FRER to be
used inside the TSN sub-network.
The Sequence encode/decode function must support the Redundancy tag
(R-TAG) format as per Clause 7.8 of [IEEE8021CB].
A TSN-aware MPLS (DetNet) node implementation must support the Stream
splitting function and the Individual recovery function as defined in
Clause 7.7 and 7.5 of [IEEE8021CB] in order for that node to be a
replication or elimination point for FRER.
4.3. Service protection within the TSN sub-network
TSN Streams supporting DetNet flows may use Frame Replication and
Elimination for Redundancy (FRER) as defined in Clause 8. of
[IEEE8021CB] based on the loss service requirements of the TSN
Stream, which is derived from the DetNet service requirements of the
DetNet mapped flow. The specific operation of FRER is not modified
by the use of DetNet and follows [IEEE8021CB].
FRER function and the provided service recovery is available only
within the TSN sub-network as the TSN Stream-ID and the TSN sequence
number are not valid outside the sub-network. An MPLS (DetNet) node
represents a L3 border and as such it terminates all related
information elements encoded in the L2 frames.
As the Stream-ID and the TSN sequence number are paired with the
similar MPLS flow parameters, FRER can be combined with PREOF
functions. Such service protection interworking scenarios may
require to move sequence number fields among TSN (L2) and PW (MPLS)
encapsulations and they are left for further study.
4.4. Aggregation during DetNet flow to TSN Stream mapping
Implementation of this document shall use management and control
information to map a DetNet flow to a TSN Stream. N:1 mapping
(aggregating DetNet flows in a single TSN Stream) shall be supported.
The management or control function that provisions flow mapping shall
ensure that adequate resources are allocated and configured to
provide proper service requirements of the mapped flows.
5. Management and Control Implications
DetNet flow and TSN Stream mapping related information are required
only for TSN-aware MPLS (DetNet) nodes. From the Data Plane
perspective there is no practical difference based on the origin of
flow mapping related information (management plane or control plane).
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The following summarizes the set of information that is needed to
configure DetNet MPLS over TSN:
o DetNet MPLS related configuration information according to the
DetNet role of the DetNet MPLS node, as per [RFC8964].
o TSN related configuration information according to the TSN role of
the DetNet MPLS node, as per [IEEE8021Q], [IEEE8021CB] and
[IEEEP8021CBdb].
o Mapping between DetNet MPLS flow(s) (label information: A-labels,
S-labels and F-labels as defined in [RFC8964]) and TSN Stream(s)
(as stream identification information defined in [IEEEP8021CBdb]).
Note, that managed objects for TSN Stream identification can be
found in [IEEEP8021CBcv].
This information must be provisioned per DetNet flow.
Mappings between DetNet and TSN management and control planes are out
of scope of the document. Some of the challenges are highlighted
below.
TSN-aware MPLS DetNet nodes are members of both the DetNet domain and
the TSN sub-network. Within the TSN sub-network the TSN-aware MPLS
(DetNet) node has a TSN-aware Talker/Listener role, so TSN specific
management and control plane functionalities must be implemented.
There are many similarities in the management plane techniques used
in DetNet and TSN, but that is not the case for the control plane
protocols. For example, RSVP-TE and MSRP (Multiple Stream
Registration Protocol) behaves differently. Therefore management and
control plane design is an important aspect of scenarios, where
mapping between DetNet and TSN is required.
In order to use a TSN sub-network between DetNet nodes, DetNet
specific information must be converted to TSN sub-network specific
ones. DetNet flow ID and flow related parameters/requirements must
be converted to a TSN Stream ID and stream related parameters/
requirements. Note that, as the TSN sub-network is just a portion of
the end-2-end DetNet path (i.e., a single hop from MPLS perspective),
some parameters (e.g., delay) may differ significantly. Other
parameters (like bandwidth) also may have to be tuned due to the L2
encapsulation used within the TSN sub-network.
In some cases it may be challenging to determine some TSN Stream
related information. For example, on a TSN-aware MPLS (DetNet) node
that acts as a Talker, it is quite obvious which DetNet node is the
Listener of the mapped TSN stream (i.e., the MPLS Next-Hop). However
it may be not trivial to locate the point/interface where that
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Listener is connected to the TSN sub-network. Such attributes may
require interaction between control and management plane functions
and between DetNet and TSN domains.
Mapping between DetNet flow identifiers and TSN Stream identifiers,
if not provided explicitly, can be done by a TSN-aware MPLS (DetNet)
node locally based on information provided for configuration of the
TSN Stream identification functions (Mask-and-match Stream
identification and Active Stream identification function).
Triggering the setup/modification of a TSN Stream in the TSN sub-
network is an example where management and/or control plane
interactions are required between the DetNet and TSN sub-network.
TSN-unaware MPLS (DetNet) nodes make such a triggering even more
complicated as they are fully unaware of the sub-network and run
independently.
Configuration of TSN specific functions (e.g., FRER) inside the TSN
sub-network is a TSN domain specific decision and may not be visible
in the DetNet domain. Service protection interworking scenarios are
left for further study.
6. Security Considerations
Security considerations for DetNet are described in detail in
[I-D.ietf-detnet-security]. General security considerations are
described in [RFC8655]. DetNet MPLS data plane specific
considerations are summarized in [RFC8964]. This section considers
exclusively security considerations which are specific to the DetNet
MPLS over TSN sub-network scenario.
The sub-network between DetNet nodes needs to be subject to
appropriate confidentiality. Additionally, knowledge of what DetNet/
TSN services are provided by a sub-network may supply information
that can be used in a variety of security attacks. The ability to
modify information exchanges between connected DetNet nodes may
result in bogus operations. Therefore, it is important that the
interface between DetNet nodes and TSN sub-network are subject to
authorization, authentication, and encryption.
The TSN sub-network operates at Layer-2 so various security
mechanisms defined by IEEE can be used to secure the connection
between the DetNet nodes (e.g., encryption may be provided using
MACSec [IEEE802.1AE-2018]).
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7. IANA Considerations
This document makes no IANA requests.
8. Acknowledgements
The authors wish to thank Norman Finn, Lou Berger, Craig Gunther,
Christophe Mangin and Jouni Korhonen for their various contributions
to this work.
9. References
9.1. Normative References
[IEEE8021CB]
IEEE 802.1, "Standard for Local and metropolitan area
networks - Frame Replication and Elimination for
Reliability (IEEE Std 802.1CB-2017)", 2017,
<http://standards.ieee.org/about/get/>.
[IEEEP8021CBdb]
Mangin, C., "Extended Stream identification functions",
IEEE P802.1CBdb /D1.0 P802.1CBdb, September 2020,
<http://www.ieee802.org/1/files/private/db-drafts/d1/802-
1CBdb-d1-0.pdf>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
9.2. Informative References
[I-D.ietf-detnet-security]
Grossman, E., Mizrahi, T., and A. Hacker, "Deterministic
Networking (DetNet) Security Considerations", draft-ietf-
detnet-security-13 (work in progress), December 2020.
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[IEEE802.1AE-2018]
IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
Security (MACsec)", 2018,
<https://ieeexplore.ieee.org/document/8585421>.
[IEEE8021Q]
IEEE 802.1, "Standard for Local and metropolitan area
networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
2018)", 2018, <http://standards.ieee.org/about/get/>.
[IEEEP8021CBcv]
Kehrer, S., "FRER YANG Data Model and Management
Information Base Module", IEEE P802.1CBcv
/D0.4 P802.1CBcv, August 2020,
<https://www.ieee802.org/1/files/private/cv-drafts/d0/802-
1CBcv-d0-4.pdf>.
Authors' Addresses
Balazs Varga (editor)
Ericsson
Magyar Tudosok krt. 11.
Budapest 1117
Hungary
Email: balazs.a.varga@ericsson.com
Janos Farkas
Ericsson
Magyar Tudosok krt. 11.
Budapest 1117
Hungary
Email: janos.farkas@ericsson.com
Andrew G. Malis
Malis Consulting
Email: agmalis@gmail.com
Stewart Bryant
Futurewei Technologies
Email: stewart.bryant@gmail.com
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