Deterministic Networking (DetNet) Data Plane: IP over IEEE 802.1 Time‑Sensitive Networking (TSN)EricssonMagyar Tudosok krt. 11.BudapestHungary1117balazs.a.varga@ericsson.comEricssonMagyar Tudosok krt. 11.BudapestHungary1117janos.farkas@ericsson.comMalis Consultingagmalis@gmail.comFuturewei Technologiessb@stewartbryant.comDetNetsub-networkflow mapping
This document specifies the Deterministic Networking IP data plane when
operating over a 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 document is not an Internet Standards Track specification; it is
published for informational purposes.
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Table of Contents
. Introduction
. Terminology
. Terms Used in This Document
. Abbreviations
. DetNet IP Data Plane Overview
. DetNet IP Flows over an IEEE 802.1 TSN Sub-network
. Functions for DetNet Flow to TSN Stream Mapping
. TSN Requirements of IP DetNet Nodes
. Service Protection within the TSN Sub-network
. Aggregation during DetNet Flow to TSN Stream Mapping
. Management and Control Implications
. Security Considerations
. IANA Considerations
. References
. Normative References
. Informative References
Acknowledgements
Authors' Addresses
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 .
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 Time-Sensitive Networking (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 provide
congestion protection (low loss, assured latency, and limited
reordering). As described in , 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 domain.
Service protection can be
provided on a per-sub-network basis as shown here for the IEEE 802.1
TSN sub-network scenario.
TerminologyTerms Used in This Document
This document uses the terminology and concepts established in the
DetNet Architecture .
TSN-specific terms are defined by the TSN Task Group of the IEEE 802.1 Working
Group. The reader is assumed to be familiar with these documents
and their terminology.
Abbreviations
The following abbreviations are 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.
DetNet IP Data Plane Overview 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 flow identification based on
a "6-tuple", where "6-tuple" refers to information carried in IP- and
higher-layer protocol headers as defined in .
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, and shaping) are supported using the underlying
link / sub-net-specific mechanisms. Service protections
(packet-replication and packet-elimination functions) are not provided
at the IP DetNet layer end to end due to the lack of unified
end-to-end sequencing information that would be available for
intermediate nodes. However, such service protection can be provided
per underlying L2 link and per sub-network.
DetNet routers ensure that DetNet service requirements are met per hop by
allocating local resources, by both receiving and transmitting, 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 .
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.
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 the TSN perspective, dual-homed
characteristics of Talker or Listener nodes are transparent to the IP
Layer.
DetNet-Enabled IP Network over a TSN Sub-network
IP (DetNet) IP (DetNet)
Node-1 Node-2
............ ............
<--: Service :-- DetNet flow ---: Service :-->
+----------+ +----------+
|Forwarding| |Forwarding|
+--------.-+ <-TSN Str-> +-.-----.--+
\ ,-------. / /
+----[ TSN Sub-]---+ /
[ Network ]--------+
`-------'
<----------------- DetNet IP ----------------->
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 that
provide zero congestion loss and bounded latency in bridged
networks. Furthermore,
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 described in Annex C.5 of
. For example,
applied on the TSN edge port it can convert an ingress unicast
IP (DetNet) flow to use a specific L2 multicast destination
Media Access Control (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.
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 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 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 defines an Active Destination MAC
and VLAN Stream identification function that can
replace some Ethernet header fields: (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 within 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.
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 a 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 . 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 with TSN Functions
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 ------->
A TSN-aware IP (DetNet) node implementation must
support the Stream identification TSN component for
recognizing flows.
A Stream identification component must be able to instantiate
the following: (1) Active Destination MAC and VLAN Stream
identification, (2) IP Stream identification, (3) Mask-and-Match
Stream identification, and (4) the related managed objects in
Clause 9 of and
.
A TSN-aware IP (DetNet) node implementation must support the
Sequencing function and the Sequence encode/decode function as
defined in Clauses 7.4 and 7.6 of 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 .
A TSN-aware IP (DetNet) node implementation must support the
Stream splitting
function and the Individual recovery function as defined in Clauses 7.7 and 7.5 of
when the node is
a replication or elimination point for FRER.
Service Protection within the TSN Sub-network
TSN Streams supporting DetNet flows may use FRER as defined in Clause 8 of
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 .
The FRER function and the provided service recovery are 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 an L3 border and as such, it terminates
all related information elements encoded in the L2 frames.
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.
Management and Control Implications
DetNet flows 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).
The following summarizes the set of information that is needed to
configure DetNet IP over TSN:
DetNet-IP-related configuration information according to the
DetNet role of the DetNet IP node, as per .
TSN-related configuration information according to the TSN role of
the DetNet IP node, as per , , and
.
Mapping between DetNet IP flow(s) and TSN Stream(s). DetNet IP
flow identification is summarized in and includes all wildcards, port
ranges, and the ability to ignore specific IP fields. Information on
TSN Stream identification information is defined in and . Note that managed
objects for TSN Stream identification can be found in .
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
highlighted 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 the Multiple
Stream Registration Protocol (MSRP) of IEEE 802.1 behave
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 information.
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 an 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 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 not be 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
the 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.
Security Considerations
Security considerations for DetNet are described in detail in
. General security considerations
are described in .
Considerations specific to the DetNet IP data plane are summarized in
.
This section discusses security considerations that 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 the 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
).
IANA Considerations
This document has no IANA actions.
ReferencesNormative ReferencesIEEE Standard for Local and metropolitan area networks--Frame Replication and Elimination for ReliabilityIEEEIEEE 802.1CB-2017Draft Standard for Local and metropolitan area networks -- Frame Replication and Elimination for Reliability -- Amendment: Extended Stream Identification FunctionsIEEEIEEE P802.1CBdb / D1.3Deterministic Networking ArchitectureThis document provides the overall architecture for Deterministic Networking (DetNet), which provides a capability to carry specified unicast or multicast data flows for real-time applications with extremely low data loss rates and bounded latency within a network domain. Techniques used include 1) reserving data-plane resources for individual (or aggregated) DetNet flows in some or all of the intermediate nodes along the path of the flow, 2) providing explicit routes for DetNet flows that do not immediately change with the network topology, and 3) distributing data from DetNet flow packets over time and/or space to ensure delivery of each packet's data in spite of the loss of a path. DetNet operates at the IP layer and delivers service over lower-layer technologies such as MPLS and Time- Sensitive Networking (TSN) as defined by IEEE 802.1.Deterministic Networking (DetNet) Data Plane: IPThis document specifies the Deterministic Networking (DetNet) data plane operation for IP hosts and routers that provide DetNet service to IP-encapsulated data. No DetNet-specific encapsulation is defined to support IP flows; instead, the existing IP-layer and higher-layer protocol header information is used to support flow identification and DetNet service delivery. This document builds on the DetNet architecture (RFC 8655) and data plane framework (RFC 8938).Informative ReferencesDeterministic Networking (DetNet) Security ConsiderationsWork in ProgressIEEE Standard for Local and metropolitan area networks--Media Access Control (MAC) SecurityIEEEIEEE 802.1AE-2018IEEE Standard for Local and Metropolitan Area Network--Bridges and Bridged NetworksIEEEIEEE Std 802.1Q-2018Draft Standard for Local and metropolitan area networks--Frame Replication and Elimination for Reliability--Amendment: Information Model, YANG Data Model and Management Information Base ModuleIEEE 802.1IEEE P802.1CBcv, Draft 1.1Acknowledgements
The authors wish to thank ,
, , , and
for their various
contributions to this work.
Authors' AddressesEricssonMagyar Tudosok krt. 11.BudapestHungary1117balazs.a.varga@ericsson.comEricssonMagyar Tudosok krt. 11.BudapestHungary1117janos.farkas@ericsson.comMalis Consultingagmalis@gmail.comFuturewei Technologiessb@stewartbryant.com