Internet DRAFT - draft-ietf-detnet-ip-over-tsn
draft-ietf-detnet-ip-over-tsn
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: IP over IEEE 802.1 Time Sensitive Networking (TSN)
draft-ietf-detnet-ip-over-tsn-07
Abstract
This document specifies the Deterministic Networking IP data plane
when operating over a 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Terms Used In This Document . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
3. DetNet IP Data Plane Overview . . . . . . . . . . . . . . . . 3
4. DetNet IP Flows over an IEEE 802.1 TSN sub-network . . . . 4
4.1. Functions for DetNet Flow to TSN Stream Mapping . . . . . 5
4.2. TSN requirements of IP DetNet nodes . . . . . . . . . . . 6
4.3. Service protection within the TSN sub-network . . . . . . 7
4.4. Aggregation during DetNet flow to TSN Stream mapping . . 7
5. Management and Control Implications . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative references . . . . . . . . . . . . . . . . . . 10
9.2. Informative references . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Deterministic Networking (DetNet) is a service that can be offered by
a network to DetNet flows. DetNet provides these flows extremely low
packet loss rates and assured maximum end-to-end delivery latency.
General background and concepts of DetNet can be found in the DetNet
Architecture [RFC8655].
[RFC8939] specifies the DetNet data plane operation for IP hosts and
routers that provide DetNet service to IP encapsulated data. This
document focuses on the scenario where DetNet IP nodes are
interconnected by a TSN sub-network.
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
provides congestion protection (low loss, assured latency, and
limited reordering). As described in [RFC8939] no DetNet specific
headers are added to support DetNet IP flows. So, only the
forwarding sub-layer functions can be supported inside the DetNet IP
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domain. Service protection can be provided on a per sub-network
basis as shown here for the IEEE802.1 TSN sub-network scenario.
2. Terminology
2.1. Terms Used In This Document
This document uses the terminology and concepts established in the
DetNet architecture [RFC8655]. TSN (Time-Sensitive Networking)
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 used in this document:
DetNet Deterministic Networking.
FRER Frame Replication and Elimination for Redundancy (TSN
function).
L2 Layer-2.
L3 Layer-3.
TSN Time-Sensitive Networking, TSN is a Task Group of the
IEEE 802.1 Working Group.
3. DetNet IP Data Plane Overview
[RFC8939] describes how IP is used by DetNet nodes, i.e., hosts and
routers, to identify DetNet flows and provide a DetNet service. From
a data plane perspective, an end-to-end IP model is followed. DetNet
uses "6-tuple" based flow identification, where "6-tuple" refers to
information carried in IP and higher layer protocol headers as
defined in [RFC8939]. .
DetNet flow aggregation may be enabled via the use of wildcards,
masks, prefixes and ranges. IP tunnels may also be used to support
flow aggregation. In these cases, it is expected that DetNet aware
intermediate nodes will provide DetNet service assurance on the
aggregate through resource allocation and congestion control
mechanisms.
Congestion protection, latency control and the resource allocation
(queuing, policing, shaping) are supported using the underlying link
/ sub-net specific mechanisms. Service protections (packet
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replication and packet elimination functions) are not provided at the
IP DetNet layer end-to-end due to the lack of a unified end-to-end
sequencing information that would be available for intermediate
nodes. However, such service protection can be provided on a per
underlying L2 link and sub-network basis.
DetNet routers ensure that DetNet service requirements are met per
hop by allocating local resources, both receive and transmit, and by
mapping the service requirements of each flow to appropriate sub-
network mechanisms. Such mappings are sub-network technology
specific. DetNet nodes interconnected by a TSN sub-network are the
primary focus of this document. The mapping of DetNet IP flows to
TSN streams and TSN protection mechanisms are covered in Section 4.
4. DetNet IP Flows over an IEEE 802.1 TSN sub-network
This section covers how DetNet IP flows operate over an IEEE 802.1
TSN sub-network. Figure 1 illustrates such a scenario, where two IP
(DetNet) nodes are interconnected by a TSN sub-network. Dotted lines
around the Service components of the IP (DetNet) Nodes indicate that
they are DetNet service aware but do not perform any DetNet service
sub-layer function. Node-1 is single homed and Node-2 is dual-homed
to the TSN sub-network and they are treated as Talker or Listener
inside the TSN sub-network. Note, that from TSN perspective dual-
homed characteristics of Talker or Listener nodes are transparent to
the IP Layer.
IP (DetNet) IP (DetNet)
Node-1 Node-2
............ ............
<--: Service :-- DetNet flow ---: Service :-->
+----------+ +----------+
|Forwarding| |Forwarding|
+--------.-+ <-TSN Str-> +-.-----.--+
\ ,-------. / /
+----[ TSN-Sub ]---+ /
[ Network ]--------+
`-------'
<----------------- DetNet IP ----------------->
Figure 1: DetNet (DN) Enabled IP 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
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reliability that should prove both compatible with and useful to
DetNet networks. All these functions have to identify flows that
require TSN treatment.
TSN capabilities of the TSN sub-network are made available for IP
(DetNet) flows via the protocol interworking function described in
Annex C.5 of [IEEE8021CB]. For example, applied on the TSN edge port
it can convert an ingress unicast IP (DetNet) flow to use a specific
L2 multicast destination MAC address and a VLAN, in order to forward
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 L2 destination MAC
address and VLAN.
Placement of TSN functions depends on the TSN capabilities of nodes.
IP (DetNet) Nodes may or may not support TSN functions. For a given
TSN Stream (i.e., a mapped DetNet flow) an IP (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 IP 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 (Layer-2). The passive stream
identification function is used to catch the 6-tuple of a DetNet IP
flow and the active stream identification function is used to modify
the Ethernet header according to the ID of the mapped TSN Stream.
Clause 6.7 of [IEEE8021CB] defines an IP Stream identification
function that can be used as a passive function for IP DetNet flows
using UDP or TCP. Clause 6.8 of [IEEEP8021CBdb] defines a Mask-and-
Match Stream identification function that can be used as a passive
function for any IP 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.
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4.2. TSN requirements of IP DetNet nodes
This section covers the required behavior of a TSN-aware 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 DetNet IP nodes are treated as
Talker or Listener, that may be (1) TSN-unaware or (2) TSN-aware.
In cases of TSN-unaware IP DetNet nodes the TSN relay nodes within
the TSN sub-network must modify the Ethernet encapsulation of the
DetNet IP 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
IP DetNet nodes in this document.
IP (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 IP (DetNet) node must provide the TSN sub-network
specific Ethernet encapsulation over the link(s) towards the sub-
network.
IP (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 ------->
Figure 2: IP (DetNet) node with TSN functions
A TSN-aware IP (DetNet) node impementations must support the Stream
Identification TSN component for recognizing flows.
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A Stream identification component must be able to instantiate the
following functions (1) Active Destination MAC and VLAN Stream
identification function, (2) IP Stream identification function, (3)
Mask-and-Match Stream identification function and (4) the related
managed objects in Clause 9 of [IEEE8021CB] and [IEEEP8021CBdb].
A TSN-aware IP (DetNet) node implementation must support the
Sequencing function and the Sequence encode/decode function as
defined in Clause 7.4 and 7.6 of [IEEE8021CB] if FRER is 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 IP (DetNet) node implementations must support the Stream
splitting function and the Individual recovery function as defined in
Clause 7.7 and 7.5 of [IEEE8021CB] when the node is 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 IP (DetNet) node
represents a L3 border and as such it terminates all related
information elements encoded in the L2 frames.
4.4. Aggregation during DetNet flow to TSN Stream mapping
Implementations 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 IP (DetNet) nodes. From the Data Plane
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perspective there is no practical difference based on the origin of
flow mapping related information (management plane or control plane).
The following summarizes the set of information that is needed to
configure DetNet IP over TSN:
o DetNet IP related configuration information according to the
DetNet role of the DetNet IP node, as per [RFC8939].
o TSN related configuration information according to the TSN role of
the DetNet IP node, as per [IEEE8021Q], [IEEE8021CB] and
[IEEEP8021CBdb].
o Mapping between DetNet IP flow(s) and TSN Stream(s). DetNet IP
flow identification is summarized in Section 5.1 of [RFC8939], and
includes all wildcards, port ranges and the ability to ignore
specific IP fields). For TSN Streams stream identification
information are defined in [IEEE8021CB] and [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 this document. Some of the challenges are highligthed
below.
TSN-aware IP DetNet nodes are members of both the DetNet domain and
the TSN sub-network. Within the TSN sub-network the TSN-aware IP
(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 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-to-end DetNet path (i.e., single hop from IP 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.
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In some cases it may be challenging to determine some TSN Stream
related information. For example, on a TSN-aware IP (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 IP Next-Hop). However
it may be not trivial to locate the point/interface where that
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 IP (DetNet)
node locally based on information provided for configuration of the
TSN Stream identification functions (IP Stream identification, 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 IP (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.
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 IP data plane specific considerations
are summarized in [RFC8939]. This section considers exclusively
security considerations which are specific to the DetNet IP 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
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between the DetNet nodes (e.g., encryption may be provided using
MACSec [IEEE802.1AE-2018]).
7. IANA Considerations
None.
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>.
[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>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
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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