DetNet B. Varga, Ed.
Internet-Draft J. Farkas
Intended status: Standards Track Ericsson
Expires: April 29, 2020 A. Malis
Independent
S. Bryant
Futurewei Technologies
October 27, 2019
DetNet Data Plane: IP over IEEE 802.1 Time Sensitive Networking (TSN)
draft-ietf-detnet-ip-over-tsn-01
Abstract
This document specifies the Deterministic Networking IP data plane
when operating over a TSN sub-network.
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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
2.3. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. DetNet IP Data Plane Overview . . . . . . . . . . . . . . . . 3
4. DetNet IP Flows over an IEEE 802.1 TSN sub-network . . . . 5
4.1. Functions for DetNet Flow to TSN Stream Mapping . . . . . 6
4.2. TSN requirements of IP 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 . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative references . . . . . . . . . . . . . . . . . . 10
9.2. Informative references . . . . . . . . . . . . . . . . . 10
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 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 [I-D.ietf-detnet-architecture].
[I-D.ietf-detnet-ip] 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 [I-D.ietf-detnet-ip] no DetNet
specific headers are added to support DetNet IP flows, only the
forwarding sub-layer functions are supported inside the DetNet
domain. Service protection can be provided on a per sub-network
basis as shown here for the IEEE802.1 TSN sub-network scenario.
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2. Terminology
[Editor's note: Needs clean up.].
2.1. Terms Used In This Document
This document uses the terminology and concepts established in the
DetNet architecture [I-D.ietf-detnet-architecture], and the reader is
assumed to be familiar with that document and its terminology.
2.2. Abbreviations
The following abbreviations used in this document:
DetNet Deterministic Networking.
DF DetNet Flow.
L2 Layer-2.
L3 Layer-3.
PREOF Packet Replication, Ordering and Elimination Function.
TSN Time-Sensitive Networking, TSN is a Task Group of the
IEEE 802.1 Working Group.
2.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. DetNet IP Data Plane Overview
[Editor's note: this section and highlights that DetNet IP over
subnets scenario being the focus in the remaining part of the
document.].
[I-D.ietf-detnet-ip] 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.
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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
replication and packet elimination functions) are not provided at the
DetNet layer end to end due 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.
Edge Transit Relay
Node Node Node
+.........+
<--:Svc Proxy:-- End to End Service ----------->
+-----....+ +..........+
|IP | :Svc:<-- DetNet flow ---: Service :--->
+---+ +---+ +---------+ +---------+
|Fwd| |Fwd| | Fwd | |Fwd| |Fwd|
+-.-+ +-.-+ +--.----.-+ +-.-+ +-.-+
: / ,-----. \ : Link : :
.....+ +-[TSN Sub]-+ +........+ +.....
[Network]
`-----'
<------------- DetNet IP -------------
Figure 1: Part of a Simple DetNet (DN) Enabled IP Network using a TSN
sub-net
Figure 1 illustrates an extract of a DetNet enabled IP network, that
uses a TSN sub-network as interconnection between two DetNet Nodes.
In this figure, an Edge Node sits at the boundary of the DetNet
domain and provide DetNet service proxies for the end applications by
initiating and terminating DetNet service for the application's IP
flows. Node and interface resources are allocated to ensure DetNet
service requirements. Dotted lines around the Service components of
the Edge and Relay Nodes indicate that they are DetNet service aware
but do not perform any DetNet service sub-layer function, e.g., PREOF
(Packet Replication, Elimination, and Ordering Functions). In this
example the Edge Node and the Transit Node are interconnected by a
TSN sub-network, being the primary focus of this document.
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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. 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
[Authors note: how do we handle control protocols such as ICMP,
IPsec, etc.? If such protocols are part of the DetNet flow they can
be identified by the Mask-and-match Stream identification function of
P802.1CBdb.]
This section covers how DetNet IP flows operate over an IEEE 802.1
TSN sub-network. Figure 2 illustrates such a scenario, where two IP
(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.
IP (DetNet) IP (DetNet)
Node-1 Node-2
............ ............
<--: Service :-- DetNet flow ---: Service :-->
+----------+ +----------+
|Forwarding| |Forwarding|
+--------.-+ <-TSN Str-> +-.-----.--+
\ ,-------. / /
+----[ TSN-Sub ]---+ /
[ Network ]--------+
`-------'
<----------------- DetNet IP ----------------->
Figure 2: DetNet (DN) Enabled IP Network over a TSN sub-network
The Time-Sensitive Networking (TSN) Task Group of the IEEE 802.1
Working Group have defined (and are defining) a number of amendments
to IEEE 802.1Q [IEEE8021Q] that provide zero congestion loss and
bounded latency in bridged networks. Furthermore IEEE 802.1CB
[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 that
require TSN treatment.
TSN capabilities of the TSN sub-network are made available for IP
(DetNet) flows via the protocol interworking function defined in IEEE
802.1CB [IEEE8021CB]. For example, applied on the TSN edge port it
can convert an ingress unicast IP (DetNet) flow to use a specific
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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 nodes.
IP (DetNet) Nodes may or may not support TSN functions. For a given
TSN Stream (i.e., 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. 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 ID of the mapped TSN Stream.
IEEE 802.1CB [IEEE8021CB] defines an IP Stream identification
function that can be used as a passive function for IP DetNet flows
using UDP or TCP. IEEE P802.1CBdb [IEEEP8021CBdb] defines a Mask-
and-Match Stream identification function that can be used as a
passive function for any IP DetNet flows.
IEEE 802.1CB [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 IP DetNet nodes
This section covers required behavior of a TSN-aware DetNet node
using a TSN sub-network.
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
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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 3.
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 3: IP (DetNet) node with TSN functions
A TSN-aware IP (DetNet) node impementations 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) IP Stream identification function, (3)
Mask-and-Match Stream identification function and (4) the related
managed objects in Clause 9 of IEEE 802.1CB [IEEE8021CB] and IEEE
P802.1CBdb [IEEEP8021CBdb].
A TSN-aware IP (DetNet) node implementations MUST support the
Sequencing function and the Sequence encode/decode function as
defined in IEEE 802.1CB [IEEE8021CB] if FRER is used inside the TSN
sub-network.
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The Sequence encode/decode function MUST support the Redundancy tag
(R-TAG) format as per Clause 7.8 of IEEE 802.1CB [IEEE8021CB].
A TSN-aware IP (DetNet) node implementations MUST support the Stream
splitting function and the Individual recovery function as defined in
IEEE 802.1CB [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 IEEE 802.1CB
[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 IEEE 802.1CB [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
[Editor's note: This section covers management/control plane related
implications of creation, mapping, removal of TSN Stream IDs, their
related parameters and, when needed, the configuration of FRER.]
DetNet flow and TSN Stream mapping related information are required
only for TSN-aware IP (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).
TSN-aware IP DetNet nodes are member 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
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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 end2end 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.
In some case 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
The security considerations of DetNet in general are discussed in
[I-D.ietf-detnet-architecture] and [I-D.ietf-detnet-security].
DetNet IP data plane specific considerations are summarized in
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[I-D.ietf-detnet-ip]. Encryption may provided by an underlying sub-
net using MACSec [IEEE802.1AE-2018] for DetNet IP over TSN flows.
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
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative references
[G.8275.1]
International Telecommunication Union, "Precision time
protocol telecom profile for phase/time synchronization
with full timing support from the network", ITU-T
G.8275.1/Y.1369.1 G.8275.1, June 2016,
<https://www.itu.int/rec/T-REC-G.8275.1/en>.
[G.8275.2]
International Telecommunication Union, "Precision time
protocol telecom profile for phase/time synchronization
with partial timing support from the network", ITU-T
G.8275.2/Y.1369.2 G.8275.2, June 2016,
<https://www.itu.int/rec/T-REC-G.8275.2/en>.
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-13 (work in progress), May 2019.
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[I-D.ietf-detnet-flow-information-model]
Farkas, J., Varga, B., Cummings, R., Jiang, Y., and D.
Fedyk, "DetNet Flow Information Model", draft-ietf-detnet-
flow-information-model-05 (work in progress), September
2019.
[I-D.ietf-detnet-ip]
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
Bryant, S., and J. Korhonen, "DetNet Data Plane: IP",
draft-ietf-detnet-ip-01 (work in progress), July 2019.
[I-D.ietf-detnet-security]
Mizrahi, T., Grossman, E., Hacker, A., Das, S., Dowdell,
J., Austad, H., Stanton, K., and N. Finn, "Deterministic
Networking (DetNet) Security Considerations", draft-ietf-
detnet-security-05 (work in progress), August 2019.
[IEEE1588]
IEEE, "IEEE 1588 Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems Version 2", 2008.
[IEEE802.1AE-2018]
IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
Security (MACsec)", 2018,
<https://ieeexplore.ieee.org/document/8585421>.
[IEEE8021CB]
Finn, N., "Draft Standard for Local and metropolitan area
networks - Seamless Redundancy", IEEE P802.1CB
/D2.1 P802.1CB, December 2015,
<http://www.ieee802.org/1/files/private/cb-drafts/d2/802-
1CB-d2-1.pdf>.
[IEEE8021Q]
IEEE 802.1, "Standard for Local and metropolitan area
networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
2014)", 2014, <http://standards.ieee.org/about/get/>.
[IEEEP8021CBdb]
Mangin, C., "Extended Stream identification functions",
IEEE P802.1CBdb /D0.2 P802.1CBdb, August 2019,
<http://www.ieee802.org/1/files/private/cb-drafts/d2/802-
1CB-d2-1.pdf>.
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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
Independent
Email: agmalis@gmail.com
Stewart Bryant
Futurewei Technologies
Email: stewart.bryant@gmail.com
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