Internet DRAFT - draft-ietf-detnet-architecture
draft-ietf-detnet-architecture
DetNet N. Finn
Internet-Draft Huawei
Intended status: Standards Track P. Thubert
Expires: November 7, 2019 Cisco
B. Varga
J. Farkas
Ericsson
May 6, 2019
Deterministic Networking Architecture
draft-ietf-detnet-architecture-13
Abstract
This 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 IEEE
802.1 Time-Sensitive Networking (TSN).
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
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This Internet-Draft will expire on November 7, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Terms used in this document . . . . . . . . . . . . . . . 4
2.2. IEEE 802.1 TSN to DetNet dictionary . . . . . . . . . . . 7
3. Providing the DetNet Quality of Service . . . . . . . . . . . 7
3.1. Primary goals defining the DetNet QoS . . . . . . . . . . 8
3.2. Mechanisms to achieve DetNet QoS . . . . . . . . . . . . 10
3.2.1. Resource allocation . . . . . . . . . . . . . . . . . 10
3.2.1.1. Eliminate contention loss . . . . . . . . . . . . 10
3.2.1.2. Jitter Reduction . . . . . . . . . . . . . . . . 11
3.2.2. Service Protection . . . . . . . . . . . . . . . . . 11
3.2.2.1. In-Order Delivery . . . . . . . . . . . . . . . . 12
3.2.2.2. Packet Replication and Elimination . . . . . . . 12
3.2.2.3. Packet encoding for service protection . . . . . 14
3.2.3. Explicit routes . . . . . . . . . . . . . . . . . . . 14
3.3. Secondary goals for DetNet . . . . . . . . . . . . . . . 15
3.3.1. Coexistence with normal traffic . . . . . . . . . . . 15
3.3.2. Fault Mitigation . . . . . . . . . . . . . . . . . . 16
4. DetNet Architecture . . . . . . . . . . . . . . . . . . . . . 17
4.1. DetNet stack model . . . . . . . . . . . . . . . . . . . 17
4.1.1. Representative Protocol Stack Model . . . . . . . . . 17
4.1.2. DetNet Data Plane Overview . . . . . . . . . . . . . 20
4.1.3. Network reference model . . . . . . . . . . . . . . . 22
4.2. DetNet systems . . . . . . . . . . . . . . . . . . . . . 23
4.2.1. End system . . . . . . . . . . . . . . . . . . . . . 23
4.2.2. DetNet edge, relay, and transit nodes . . . . . . . . 24
4.3. DetNet flows . . . . . . . . . . . . . . . . . . . . . . 25
4.3.1. DetNet flow types . . . . . . . . . . . . . . . . . . 25
4.3.2. Source transmission behavior . . . . . . . . . . . . 25
4.3.3. Incomplete Networks . . . . . . . . . . . . . . . . . 27
4.4. Traffic Engineering for DetNet . . . . . . . . . . . . . 27
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4.4.1. The Application Plane . . . . . . . . . . . . . . . . 28
4.4.2. The Controller Plane . . . . . . . . . . . . . . . . 28
4.4.3. The Network Plane . . . . . . . . . . . . . . . . . . 29
4.5. Queuing, Shaping, Scheduling, and Preemption . . . . . . 30
4.6. Service instance . . . . . . . . . . . . . . . . . . . . 31
4.7. Flow identification at technology borders . . . . . . . . 32
4.7.1. Exporting flow identification . . . . . . . . . . . . 32
4.7.2. Flow attribute mapping between layers . . . . . . . . 34
4.7.3. Flow-ID mapping examples . . . . . . . . . . . . . . 35
4.8. Advertising resources, capabilities and adjacencies . . . 36
4.9. Scaling to larger networks . . . . . . . . . . . . . . . 37
4.10. Compatibility with Layer-2 . . . . . . . . . . . . . . . 37
5. Security Considerations . . . . . . . . . . . . . . . . . . . 37
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 39
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39
9. Informative References . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
This document provides the overall architecture for Deterministic
Networking (DetNet), which provides a capability for the delivery of
data flows with extremely low packet loss rates and bounded end-to-
end delivery latency. DetNet is for networks that are under a single
administrative control or within a closed group of administrative
control; these include campus-wide networks and private WANs. DetNet
is not for large groups of domains such as the Internet.
DetNet operates at the IP layer and delivers service over lower layer
technologies such as MPLS and IEEE 802.1 Time-Sensitive Networking
(TSN). DetNet accomplishes these goals by dedicating network
resources such as link bandwidth and buffer space to DetNet flows
and/or classes of DetNet flows, and by replicating packets along
multiple paths. Unused reserved resources are available to non-
DetNet packets as long as all guarantees are fulfilled.
The Deterministic Networking Problem Statement
[I-D.ietf-detnet-problem-statement] introduces Deterministic
Networking, and Deterministic Networking Use Cases
[I-D.ietf-detnet-use-cases] summarizes the need for it. See
[I-D.ietf-detnet-dp-sol-mpls] and [I-D.ietf-detnet-dp-sol-ip] for
specific techniques that can be used to identify DetNet flows and
assign them to specific paths through a network.
A goal of DetNet is a converged network in all respects including the
convergence of sensitive non-IP networks onto a common network
infrastructure. The presence of DetNet flows does not preclude non-
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DetNet flows, and the benefits offered DetNet flows should not,
except in extreme cases, prevent existing Quality of Service (QoS)
mechanisms from operating in a normal fashion, subject to the
bandwidth required for the DetNet flows. A single source-destination
pair can trade both DetNet and non-DetNet flows. End systems and
applications need not instantiate special interfaces for DetNet
flows. Networks are not restricted to certain topologies;
connectivity is not restricted. Any application that generates a
data flow that can be usefully characterized as having a maximum
bandwidth should be able to take advantage of DetNet, as long as the
necessary resources can be reserved. Reservations can be made by the
application itself, via network management, by an application's
controller, or by other means, e.g., a dynamic control plane (e.g.,
[RFC2205]). QoS requirements of DetNet flows can be met if all
network nodes in a DetNet domain implement DetNet capabilities.
DetNet nodes can be interconnected with different sub-network
technologies (Section 4.1.2), where the nodes of the subnet are not
DetNet aware (Section 4.1.3).
Many applications that are intended to be served by Deterministic
Networking require the ability to synchronize the clocks in end
systems to a sub-microsecond accuracy. Some of the queue control
techniques defined in Section 4.5 also require time synchronization
among network nodes. The means used to achieve time synchronization
are not addressed in this document. DetNet can accommodate various
time synchronization techniques and profiles that are defined
elsewhere to address the needs of different market segments.
2. Terminology
2.1. Terms used in this document
The following terms are used in the context of DetNet in this
document:
allocation
Resources are dedicated to support a DetNet flow. Depending
on an implementation, the resource may be reused by non-
DetNet flows when it is not used by the DetNet flow.
App-flow
The payload (data) carried over a DetNet service.
DetNet compound flow and DetNet member flow
A DetNet compound flow is a DetNet flow that has been
separated into multiple duplicate DetNet member flows for
service protection at the DetNet service sub-layer. Member
flows are merged back into a single DetNet compound flow such
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that there are no duplicate packets. "Compound" and "member"
are strictly relative to each other, not absolutes; a DetNet
compound flow comprising multiple DetNet member flows can, in
turn, be a member of a higher-order compound.
DetNet destination
An end system capable of terminating a DetNet flow.
DetNet domain
The portion of a network that is DetNet aware. It includes
end systems and DetNet nodes.
DetNet edge node
An instance of a DetNet relay node that acts as a source and/
or destination at the DetNet service sub-layer. For example,
it can include a DetNet service sub-layer proxy function for
DetNet service protection (e.g., the addition or removal of
packet sequencing information) for one or more end systems,
or starts or terminates resource allocation at the DetNet
forwarding sub-layer, or aggregates DetNet services into new
DetNet flows. It is analogous to a Label Edge Router (LER)
or a Provider Edge (PE) router.
DetNet flow
A DetNet flow is a sequence of packets which conform uniquely
to a flow identifier, and to which the DetNet service is to
be provided. It includes any DetNet headers added to support
the DetNet service and forwarding sub-layers.
DetNet forwarding sub-layer
DetNet functionality is divided into two sub-layers. One of
them is the DetNet forwarding sub-layer, which optionally
provides resource allocation for DetNet flows over paths
provided by the underlying network.
DetNet intermediate node
A DetNet relay node or DetNet transit node.
DetNet node
A DetNet edge node, a DetNet relay node, or a DetNet transit
node.
DetNet relay node
A DetNet node including a service sub-layer function that
interconnects different DetNet forwarding sub-layer paths to
provide service protection. A DetNet relay node participates
in the DetNet service sub-layer. It typically incorporates
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DetNet forwarding sub-layer functions as well, in which case
it is collocated with a transit node.
DetNet service sub-layer
DetNet functionality is divided into two sub-layers. One of
them is the DetNet service sub-layer, at which a DetNet
service, e.g., service protection is provided.
DetNet service proxy
Maps between App-flows and DetNet flows.
DetNet source
An end system capable of originating a DetNet flow.
DetNet system
A DetNet aware end system, transit node, or relay node.
"DetNet" may be omitted in some text.
DetNet transit node
A DetNet node operating at the DetNet forwarding sub-layer,
that utilizes link layer and/or network layer switching
across multiple links and/or sub-networks to provide paths
for DetNet service sub-layer functions. Typically provides
resource allocation over those paths. An MPLS LSR is an
example of a DetNet transit node.
DetNet-UNI
User-to-Network Interface with DetNet specific
functionalities. It is a packet-based reference point and
may provide multiple functions like encapsulation, status,
synchronization, etc.
end system
Commonly called a "host" in IETF documents, and an "end
station" is IEEE 802 documents. End systems of interest to
this document are either sources or destinations of DetNet
flows. And end system may or may not be DetNet forwarding
sub-layer aware or DetNet service sub-layer aware.
link
A connection between two DetNet nodes. It may be composed of
a physical link or a sub-network technology that can provide
appropriate traffic delivery for DetNet flows.
PEF A Packet Elimination Function (PEF) eliminates duplicate
copies of packets to prevent excess packets flooding the
network or duplicate packets being sent out of the DetNet
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domain. PEF can be implemented by a DetNet edge node, a
DetNet relay node, or an end system.
PRF A Packet Replication Function (PRF) replicates DetNet flow
packets and forwards them to one or more next hops in the
DetNet domain. The number of packet copies sent to the next
hops is a DetNet flow specific parameter at the point of
replication. PRF can be implemented by a DetNet edge node, a
DetNet relay node, or an end system.
PREOF Collective name for Packet Replication, Elimination, and
Ordering Functions.
POF A Packet Ordering Function (POF) re-orders packets within a
DetNet flow that are received out of order. This function
can be implemented by a DetNet edge node, a DetNet relay
node, or an end system.
reservation
The set of resources allocated between a source and one or
more destinations through DetNet nodes and subnets associated
with a DetNet flow, to provide the provisioned DetNet
service.
2.2. IEEE 802.1 TSN to DetNet dictionary
This section also serves as a dictionary for translating from the
terms used by the Time-Sensitive Networking (TSN) Task Group
[IEEE802.1TSNTG] of the IEEE 802.1 WG to those of the DetNet WG.
Listener
The IEEE 802.1 term for a destination of a DetNet flow.
relay system
The IEEE 802.1 term for a DetNet intermediate node.
Stream
The IEEE 802.1 term for a DetNet flow.
Talker
The IEEE 802.1 term for the source of a DetNet flow.
3. Providing the DetNet Quality of Service
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3.1. Primary goals defining the DetNet QoS
The DetNet Quality of Service can be expressed in terms of:
o Minimum and maximum end-to-end latency from source to destination;
timely delivery, and bounded jitter (packet delay variation)
derived from these constraints.
o Packet loss ratio, under various assumptions as to the operational
states of the nodes and links.
o An upper bound on out-of-order packet delivery. It is worth
noting that some DetNet applications are unable to tolerate any
out-of-order delivery.
It is a distinction of DetNet that it is concerned solely with worst-
case values for the end-to-end latency, jitter, and misordering.
Average, mean, or typical values are of little interest, because they
do not affect the ability of a real-time system to perform its tasks.
In general, a trivial priority-based queuing scheme will give better
average latency to a data flow than DetNet; however, it may not be a
suitable option for DetNet because of its worst-case latency.
Three techniques are used by DetNet to provide these qualities of
service:
o Resource allocation (Section 3.2.1).
o Service protection (Section 3.2.2).
o Explicit routes (Section 3.2.3).
Resource allocation operates by assigning resources, e.g., buffer
space or link bandwidth, to a DetNet flow (or flow aggregate) along
its path. Resource allocation greatly reduces, or even eliminates
entirely, packet loss due to output packet contention within the
network, but it can only be supplied to a DetNet flow that is limited
at the source to a maximum packet size and transmission rate. As
DetNet flows are assumed to be rate-limited and DetNet is designed to
provide sufficient allocated resources (including provisioned
capacity), the use of transport layer congestion control [RFC2914]
for App-flows is not required; however, if resources are allocated
appropriately, use of congestion control should not impact
transmission negatively.
Resource allocation addresses two of the DetNet QoS requirements:
latency and packet loss. Given that DetNet nodes have a finite
amount of buffer space, resource allocation necessarily results in a
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maximum end-to-end latency. It also addresses contention related
packet loss.
Other important contribution to packet loss are random media errors
and equipment failures. Service protection is the name for the
mechanisms used by DetNet to address these losses. The mechanisms
employed are constrained by the requirement to meet the users'
latency requirements. Packet replication and elimination
(Section 3.2.2) and packet encoding (Section 3.2.2.3) are described
in this document to provide service protection; others may be found.
For instance, packet encoding can be used to provide service
protection against random media errors, packet replication and
elimination can be used to provide service protection against
equipment failures. This mechanism distributes the contents of
DetNet flows over multiple paths in time and/or space, so that the
loss of some of the paths does need not cause the loss of any
packets.
The paths are typically (but not necessarily) explicit routes, so
that they do not normally suffer temporary interruptions caused by
the convergence of routing or bridging protocols.
These three techniques can be applied independently, giving eight
possible combinations, including none (no DetNet), although some
combinations are of wider utility than others. This separation keeps
the protocol stack coherent and maximizes interoperability with
existing and developing standards in this (IETF) and other Standards
Development Organizations. Some examples of typical expected
combinations:
o Explicit routes plus service protection are exactly the techniques
employed by seamless redundancy mechanisms applied on a ring
topology as described, e.g., in [IEC62439-3-2016]. In this
example, explicit routes are achieved by limiting the physical
topology of the network to a ring. Sequentialization,
replication, and duplicate elimination are facilitated by packet
tags added at the front or the end of Ethernet frames. [RFC8227]
provides another example in the context of MPLS.
o Resource allocation alone was originally offered by IEEE 802.1
Audio Video bridging [IEEE802.1BA]. As long as the network
suffers no failures, packet loss due to output packet contention
can be eliminated through the use of a reservation protocol (e.g.,
Multiple Stream Registration Protocol [IEEE802.1Q-2018]), shapers
in every bridge, and proper dimensioning.
o Using all three together gives maximum protection.
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There are, of course, simpler methods available (and employed, today)
to achieve levels of latency and packet loss that are satisfactory
for many applications. Prioritization and over-provisioning is one
such technique. However, these methods generally work best in the
absence of any significant amount of non-critical traffic in the
network (if, indeed, such traffic is supported at all), or work only
if the critical traffic constitutes only a small portion of the
network's theoretical capacity, or work only if all systems are
functioning properly, or in the absence of actions by end systems
that disrupt the network's operations.
There are any number of methods in use, defined, or in progress for
accomplishing each of the above techniques. It is expected that this
DetNet Architecture will assist various vendors, users, and/or
"vertical" Standards Development Organizations (dedicated to a single
industry) to make selections among the available means of
implementing DetNet networks.
3.2. Mechanisms to achieve DetNet QoS
3.2.1. Resource allocation
3.2.1.1. Eliminate contention loss
The primary means by which DetNet achieves its QoS assurances is to
reduce, or even completely eliminate packet loss due to output packet
contention within a DetNet node as a cause of packet loss. This can
be achieved only by the provision of sufficient buffer storage at
each node through the network to ensure that no packets are dropped
due to a lack of buffer storage. Note that App-flows are generally
not expected to be responsive to implicit [RFC2914] or explicit
congestion notification [RFC3168].
Ensuring adequate buffering requires, in turn, that the source, and
every DetNet node along the path to the destination (or nearly every
node, see Section 4.3.3) be careful to regulate its output to not
exceed the data rate for any DetNet flow, except for brief periods
when making up for interfering traffic. Any packet sent ahead of its
time potentially adds to the number of buffers required by the next
hop DetNet node and may thus exceed the resources allocated for a
particular DetNet flow. Furthermore, rate limiting, e.g., using
traffic policing and shaping functions, e.g., [RFC2475], at the
ingress of the DetNet domain must be applied. This is needed for
meeting the requirements of DetNet flows as well as for protecting
non-DetNet traffic from potentially misbehaving DetNet traffic
sources. Note that large buffers have some issues, see, e.g.,
[BUFFERBLOAT].
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The low-level mechanisms described in Section 4.5 provide the
necessary regulation of transmissions by an end system or DetNet node
to provide resource allocation. The allocation of the bandwidth and
buffers for a DetNet flow requires provisioning. A DetNet node may
have other resources requiring allocation and/or scheduling, that
might otherwise be over-subscribed and trigger the rejection of a
reservation.
3.2.1.2. Jitter Reduction
A core objective of DetNet is to enable the convergence of sensitive
non-IP networks onto a common network infrastructure. This requires
the accurate emulation of currently deployed mission-specific
networks, which for example rely on point-to-point analog (e.g.,
4-20mA modulation) and serial-digital cables (or buses) for highly
reliable, synchronized and jitter-free communications. While the
latency of analog transmissions is basically the speed of light,
legacy serial links are usually slow (in the order of Kbps) compared
to, say, Gigabit Ethernet, and some latency is usually acceptable.
What is not acceptable is the introduction of excessive jitter, which
may, for instance, affect the stability of control systems.
Applications that are designed to operate on serial links usually do
not provide services to recover the jitter, because jitter simply
does not exist there. DetNet flows are generally expected to be
delivered in-order and the precise time of reception influences the
processes. In order to converge such existing applications, there is
a desire to emulate all properties of the serial cable, such as clock
transportation, perfect flow isolation and fixed latency. While
minimal jitter (in the form of specifying minimum, as well as
maximum, end-to-end latency) is supported by DetNet, there are
practical limitations on packet-based networks in this regard. In
general, users are encouraged to use a combination of:
o Sub-microsecond time synchronization among all source and
destination end systems, and
o Time-of-execution fields in the application packets.
Jitter reduction is provided by the mechanisms described in
Section 4.5 that also provide resource allocation.
3.2.2. Service Protection
Service protection aims to mitigate or eliminate packet loss due to
equipment failures, including random media and/or memory faults.
These types of packet loss can be greatly reduced by spreading the
data over multiple disjoint forwarding paths. Various service
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protection methods are described in [RFC6372], e.g., 1+1 linear
protection. This section describes the functional details of an
additional method in Section 3.2.2.2, which can be implemented as
described in Section 3.2.2.3 or as specified in
[I-D.ietf-detnet-dp-sol-mpls] in order to provide 1+n hitless
protection. The appropriate service protection mechanism depends on
the scenario and the requirements.
3.2.2.1. In-Order Delivery
Out-of-order packet delivery can be a side effect of service
protection. Packets delivered out-of-order impact the amount of
buffering needed at the destination to properly process the received
data. Such packets also influence the jitter of a flow. The DetNet
service includes maximum allowed misordering as a constraint. Zero
misordering would be a valid service constraint to reflect that the
end system(s) of the flow cannot tolerate any out-of-order delivery.
DetNet Packet Ordering Functionality (POF) (Section 3.2.2.2) can be
used to provide in-order delivery.
3.2.2.2. Packet Replication and Elimination
This section describes a service protection method that sends copies
of the same packets over multiple paths.
The DetNet service sub-layer includes the packet replication (PRF),
the packet elimination (PEF), and the packet ordering functionality
(POF) for use in DetNet edge, relay node, and end system packet
processing. These functions can be enabled in a DetNet edge node,
relay node or end system. The collective name for all three
functions is Packet Replication, Elimination, and Ordering Functions
(PREOF). The packet replication and elimination service protection
method altogether involves four capabilities:
o Providing sequencing information to the packets of a DetNet
compound flow. This may be done by adding a sequence number or
time stamp as part of DetNet, or may be inherent in the packet,
e.g., in a higher layer protocol, or associated to other physical
properties such as the precise time (and radio channel) of
reception of the packet. This is typically done once, at or near
the source.
o The Packet Replication Function (PRF) replicates these packets
into multiple DetNet member flows and typically sends them along
multiple different paths to the destination(s), e.g., over the
explicit routes of Section 3.2.3. The location within a DetNet
node, and the mechanism used for the PRF is left open for
implementations.
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o The Packet Elimination Function (PEF) eliminates duplicate packets
of a DetNet flow based on the sequencing information and a history
of received packets. The output of the PEF is always a single
packet. This may be done at any DetNet node along the path to
save network resources further downstream, in particular if
multiple Replication points exist. But the most common case is to
perform this operation at the very edge of the DetNet network,
preferably in or near the receiver. The location within a DetNet
node, and mechanism used for the PEF is left open for
implementations.
o The Packet Ordering Function (POF) uses the sequencing information
to re-order a DetNet flow's packets that are received out of
order.
The order in which a DetNet node applies PEF, POF, and PRF to a
DetNet flow is left open for implementations.
Some service protection mechanisms rely on switching from one flow to
another when a failure of a flow is detected. Contrarily, packet
replication and elimination combines the DetNet member flows sent
along multiple different paths, and performs a packet-by-packet
selection of which to discard, e.g., based on sequencing information.
In the simplest case, this amounts to replicating each packet in a
source that has two interfaces, and conveying them through the
network, along separate (Shared Risk Link Group (SRLG) disjoint)
paths, to the similarly dual-homed destinations, that discard the
extras. This ensures that one path remains, even if some DetNet
intermediate node fails. The sequencing information can also be used
for loss detection and for re-ordering.
DetNet relay nodes in the network can provide replication and
elimination facilities at various points in the network, so that
multiple failures can be accommodated.
This is shown in Figure 1, where the two relay nodes each replicate
(R) the DetNet flow on input, sending the DetNet member flows to both
the other relay node and to the end system, and eliminate duplicates
(E) on the output interface to the right-hand end system. Any one
link in the network can fail, and the DetNet compound flow can still
get through. Furthermore, two links can fail, as long as they are in
different segments of the network.
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> > > > > > > > > relay > > > > > > > >
> /------------+ R node E +------------\ >
> / v + ^ \ >
end R + v | ^ + E end
system + v | ^ + system
> \ v + ^ / >
> \------------+ R relay E +-----------/ >
> > > > > > > > > node > > > > > > > >
Figure 1: Packet replication and elimination
Packet replication and elimination does not react to and correct
failures; it is entirely passive. Thus, intermittent failures,
mistakenly created packet filters, or misrouted data is handled just
the same as the equipment failures that are handled by typical
routing and bridging protocols.
If member flows that take different-length paths through the network
are combined, a merge point may require extra buffering to equalize
the delays over the different paths. This equalization ensures that
the resultant compound flow will not exceed its contracted bandwidth
even after one or the other of the paths is restored after a failure.
The extra buffering can be also used to provide in-order delivery.
3.2.2.3. Packet encoding for service protection
There are methods for using multiple paths to provide service
protection that involve encoding the information in a packet
belonging to a DetNet flow into multiple transmission units,
combining information from multiple packets into any given
transmission unit. Such techniques, also known as "network coding",
can be used as a DetNet service protection technique.
3.2.3. Explicit routes
In networks controlled by typical dynamic control protocols such as
IS-IS or OSPF, a network topology event in one part of the network
can impact, at least briefly, the delivery of data in parts of the
network remote from the failure or recovery event. Even the use of
redundant paths through a network, e.g., as defined by [RFC6372] do
not eliminate the chances of packet loss. Furthermore, out-of-order
packet delivery can be a side effect of route changes.
Many real-time networks rely on physical rings of two-port devices,
with a relatively simple ring control protocol. This supports
redundant paths for service protection with a minimum of wiring. As
an additional benefit, ring topologies can often utilize different
topology management protocols than those used for a mesh network,
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with a consequent reduction in the response time to topology changes.
Of course, this comes at some cost in terms of increased hop count,
and thus latency, for the typical path.
In order to get the advantages of low hop count and still ensure
against even very brief losses of connectivity, DetNet employs
explicit routes, where the path taken by a given DetNet flow does not
change, at least immediately, and likely not at all, in response to
network topology events. Service protection (Section 3.2.2 or
Section 3.2.2.3) over explicit routes provides a high likelihood of
continuous connectivity. Explicit routes can be established in
various ways, e.g., with RSVP-TE [RFC3209], with Segment Routing (SR)
[RFC8402], via a Software Defined Networking approach [RFC8453], with
IS-IS [RFC7813], etc. Explicit routes are typically used in MPLS TE
LSPs.
Out-of-order packet delivery can be a side effect of distributing a
single flow over multiple paths, especially when there is a change
from one path to another when combining the flow. This is
irrespective of the distribution method used, and also applies to
service protection over explicit routes. As described in
Section 3.2.2.1, out-of-order packets influence the jitter of a flow
and impact the amount of buffering needed to process the data;
therefore, DetNet service includes maximum allowed misordering as a
constraint. The use of explicit routes helps to provide in-order
delivery because there is no immediate route change with the network
topology, but the changes are plannable as they are between the
different explicit routes.
3.3. Secondary goals for DetNet
Many applications require DetNet to provide additional services,
including coexistence with other QoS mechanisms Section 3.3.1 and
protection against misbehaving transmitters Section 3.3.2.
3.3.1. Coexistence with normal traffic
A DetNet network supports the dedication of a high proportion of the
network bandwidth to DetNet flows. But, no matter how much is
dedicated for DetNet flows, it is a goal of DetNet to coexist with
existing Class of Service schemes (e.g., DiffServ). It is also
important that non-DetNet traffic not disrupt the DetNet flow, of
course (see Section 3.3.2 and Section 5). For these reasons:
o Bandwidth (transmission opportunities) not utilized by a DetNet
flow is available to non-DetNet packets (though not to other
DetNet flows).
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o DetNet flows can be shaped or scheduled, in order to ensure that
the highest-priority non-DetNet packet is also ensured a worst-
case latency.
o When transmission opportunities for DetNet flows are scheduled in
detail, then the algorithm constructing the schedule should leave
sufficient opportunities for non-DetNet packets to satisfy the
needs of the users of the network. Detailed scheduling can also
permit the time-shared use of buffer resources by different DetNet
flows.
Starvation of non-DetNet traffic must be avoided, e.g., by traffic
policing and shaping functions (e.g., [RFC2475]). Thus, the net
effect of the presence of DetNet flows in a network on the non-DetNet
flows is primarily a reduction in the available bandwidth.
3.3.2. Fault Mitigation
Robust real-time systems require reducing the number of possible
failures. Filters and policers should be used in a DetNet network to
detect if DetNet packets are received on the wrong interface, or at
the wrong time, or in too great a volume. Furthermore, filters and
policers can take actions to discard the offending packets or flows,
or trigger shutting down the offending flow or the offending
interface.
It is also essential that filters and service remarking be employed
at the network edge to prevent non-DetNet packets from being mistaken
for DetNet packets, and thus impinging on the resources allocated to
DetNet packets. In particular, sending DetNet traffic into networks
that have not been provisioned in advance to handle that DetNet
traffic has to be treated as a fault. The use of egress traffic
filters, or equivalent mechanisms, to prevent this from happening are
strongly recommended at the edges of a DetNet networks and DetNet
supporting networks. In this context, the term 'provisioned' has a
broad meaning, e.g., provisioning could be performed via an
administrative decision that the downstream network has the available
capacity to carry the DetNet traffic that is being sent into it.
Note that the sending of App-flows that do not use transport layer
congestion control per [RFC2914] into a network that is not
provisioned to handle such DetNet traffic has to be treated as a
fault and prevented. PRF generated DetNet member flows also need to
be treated as not using transport layer congestion control even if
the original App-flow supports transport layer congestion control
because PREOF can remove congestion indications at the PEF and
thereby hide such indications (e.g., drops, ECN markings, increased
latency) from end systems.
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The mechanisms to support these requirements are both data plane and
implementation specific. Data plane specific solutions will be
specified in the relevant data plane solution document. There also
exist techniques, at present and/or in various stages of
standardization, that can support these fault mitigation tasks that
deliver a high probability that misbehaving systems will have zero
impact on well-behaved DetNet flows, except of course, for the
receiving interface(s) immediately downstream of the misbehaving
device. Examples of such techniques include traffic policing and
shaping functions (e.g., [RFC2475]) and separating flows into per-
flow rate-limited queues, and potentially apply active queue
management [RFC7567].
4. DetNet Architecture
4.1. DetNet stack model
DetNet functionality (Section 3) is implemented in two adjacent sub-
layers in the protocol stack: the DetNet service sub-layer and the
DetNet forwarding sub-layer. The DetNet service sub-layer provides
DetNet service, e.g., service protection, to higher layers in the
protocol stack and applications. The DetNet forwarding sub-layer
supports DetNet service in the underlying network, e.g., by providing
explicit routes and resource allocation to DetNet flows.
4.1.1. Representative Protocol Stack Model
Figure 2 illustrates a conceptual DetNet data plane layering model.
One may compare it to that in [IEEE802.1CB], Annex C.
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| packets going | ^ packets coming ^
v down the stack v | up the stack |
+-----------------------+ +-----------------------+
| Source | | Destination |
+-----------------------+ +-----------------------+
| Service sub-layer: | | Service sub-layer: |
| Packet sequencing | | Duplicate elimination |
| Flow replication | | Flow merging |
| Packet encoding | | Packet decoding |
+-----------------------+ +-----------------------+
| Forwarding sub-layer: | | Forwarding sub-layer: |
| Resource allocation | | Resource allocation |
| Explicit routes | | Explicit routes |
+-----------------------+ +-----------------------+
| Lower layers | | Lower layers |
+-----------------------+ +-----------------------+
v ^
\_________________________/
Figure 2: DetNet data plane protocol stack
Not all sub-layers are required for any given application, or even
for any given network. The functionality shown in Figure 2 is:
Application
Shown as "source" and "destination" in the diagram.
Packet sequencing
As part of DetNet service protection, supplies the sequence
number for packet replication and elimination
(Section 3.2.2), thus peers with Duplicate elimination. This
sub-layer is not needed if a higher layer protocol is
expected to perform any packet sequencing and duplicate
elimination required by the DetNet flow replication.
Duplicate elimination
As part of the DetNet service sub-layer, based on the
sequenced number supplied by its peer, packet sequencing,
Duplicate elimination discards any duplicate packets
generated by DetNet flow replication. It can operate on
member flows, compound flows, or both. The replication may
also be inferred from other information such as the precise
time of reception in a scheduled network. The duplicate
elimination sub-layer may also perform resequencing of
packets to restore packet order in a flow that was disrupted
by the loss of packets on one or another of the multiple
paths taken.
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Flow replication
As part of DetNet service protection, packets that belong to
a DetNet compound flow are replicated into two or more DetNet
member flows. This function is separate from packet
sequencing. Flow replication can be an explicit replication
and remarking of packets, or can be performed by, for
example, techniques similar to ordinary multicast
replication, albeit with resource allocation implications.
Peers with DetNet flow merging.
Flow merging
As part of DetNet service protection, merges DetNet member
flows together for packets coming up the stack belonging to a
specific DetNet compound flow. Peers with DetNet flow
replication. DetNet flow merging, together with packet
sequencing, duplicate elimination, and DetNet flow
replication perform packet replication and elimination
(Section 3.2.2).
Packet encoding
As part of DetNet service protection, as an alternative to
packet sequencing and flow replication, packet encoding
combines the information in multiple DetNet packets, perhaps
from different DetNet compound flows, and transmits that
information in packets on different DetNet member Flows.
Peers with Packet decoding.
Packet decoding
As part of DetNet service protection, as an alternative to
flow merging and duplicate elimination, packet decoding takes
packets from different DetNet member flows, and computes from
those packets the original DetNet packets from the compound
flows input to packet encoding. Peers with Packet encoding.
Resource allocation
The DetNet forwarding sub-layer provides resource allocation.
See Section 4.5. The actual queuing and shaping mechanisms
are typically provided by underlying subnet. These can be
closely associated with the means of providing paths for
DetNet flows. The path and the resource allocation are
conflated in this figure.
Explicit routes
The DetNet forwarding sub-layer provides mechanisms to ensure
that fixed paths are provided for DetNet flows. These
explicit paths avoid the impact of network convergence.
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Operations, Administration, and Maintenance (OAM) leverages in-band
and out-of-band signaling that validates whether the service is
effectively obtained within QoS constraints. OAM is not shown in
Figure 2; it may reside in any number of the layers. OAM can involve
specific tagging added in the packets for tracing implementation or
network configuration errors; traceability enables to find whether a
packet is a replica, which DetNet relay node performed the
replication, and which segment was intended for the replica. Active
and hybrid OAM methods require additional bandwidth to perform fault
management and performance monitoring of the DetNet domain. OAM may,
for instance, generate special test probes or add OAM information
into the data packet.
The packet sequencing and replication elimination functions at the
source and destination ends of a DetNet compound flow may be
performed either in the end system or in a DetNet relay node.
4.1.2. DetNet Data Plane Overview
A "Deterministic Network" will be composed of DetNet enabled end
systems, DetNet edge nodes, and DetNet relay nodes, which
collectively deliver DetNet services. DetNet relay and edge nodes
are interconnected via DetNet transit nodes (e.g., LSRs) which
support DetNet, but are not DetNet service aware. All DetNet nodes
are connected to sub-networks, where a point-to-point link is also
considered as a simple sub-network. These sub-networks will provide
DetNet compatible service for support of DetNet traffic. Examples of
sub-network technologies include MPLS TE, IEEE 802.1 TSN and OTN. Of
course, multi-layer DetNet systems may also be possible, where one
DetNet appears as a sub-network, and provides service to, a higher
layer DetNet system. A simple DetNet concept network is shown in
Figure 3. Note that in this and following figures "Forwarding" and
"Fwd" refer to the DetNet forwarding sub-layer, "Service" and "Svc"
refer to the DetNet service sub-layer, which are described in detail
in Section 4.1.
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TSN Edge Transit Relay DetNet
End System Node Node Node End System
+----------+ +.........+ +----------+
| Appl. |<--:Svc Proxy:-- End to End Service -------->| Appl. |
+----------+ +---------+ +---------+ +----------+
| TSN | |TSN| |Svc|<- DetNet flow --: Service :-->| Service |
+----------+ +---+ +---+ +--------+ +---------+ +----------+
|Forwarding| |Fwd| |Fwd| | Fwd | |Fwd| |Fwd| |Forwarding|
+-------.--+ +-.-+ +-.-+ +--.----.+ +-.-+ +-.-+ +---.------+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +.......+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
Figure 3: A Simple DetNet Enabled Network
DetNet data plane is divided into two sub-layers: the DetNet service
sub-layer and the DetNet forwarding sub-layer. This helps to explore
and evaluate various combinations of the data plane solutions
available. Some of them are illustrated in Figure 4. This
separation of DetNet sub-layers, while helpful, should not be
considered as formal requirement. For example, some technologies may
violate these strict sub-layers and still be able to deliver a DetNet
service.
.
.
+-----------------------------+
| DetNet Service sub-layer | PW, UDP, GRE
+-----------------------------+
| DetNet Forwarding sub-layer | IPv6, IPv4, MPLS TE LSPs, MPLS SR
+-----------------------------+
.
.
Figure 4: DetNet adaptation to data plane
In some networking scenarios, the end system initially provides a
DetNet flow encapsulation, which contains all information needed by
DetNet nodes (e.g., Real-time Transport Protocol (RTP) [RFC3550]
based DetNet flow carried over a native UDP/IP network or
PseudoWire). In other scenarios, the encapsulation formats might
differ significantly.
There are many valid options to create a data plane solution for
DetNet traffic by selecting a technology approach for the DetNet
service sub-layer and also selecting a technology approach for the
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DetNet forwarding sub-layer. There are a large number of valid
combinations.
One of the most fundamental differences between different potential
data plane options is the basic headers used by DetNet nodes. For
example, the basic service can be delivered based on an MPLS label or
an IP header. This decision impacts the basic forwarding logic for
the DetNet service sub-layer. Note that in both cases, IP addresses
are used to address DetNet nodes. The selected DetNet forwarding
sub-layer technology also needs to be mapped to the sub-net
technology used to interconnect DetNet nodes. For example, DetNet
flows will need to be mapped to TSN Streams.
4.1.3. Network reference model
Figure 5 shows another view of the DetNet service related reference
points and main components.
DetNet DetNet
end system end system
_ _
/ \ +----DetNet-UNI (U) / \
/App\ | /App\
/-----\ | /-----\
| NIC | v ________ | NIC |
+--+--+ _____ / \ DetNet-UNI (U) --+ +--+--+
| / \__/ \ | |
| / +----+ +----+ \_____ | |
| / | | | | \_______ | |
+------U PE +----+ P +----+ \ _ v |
| | | | | | | ___/ \ |
| +--+-+ +----+ | +----+ | / \_ |
\ | | | | | / \ |
\ | +----+ +--+-+ +--+PE |------ U-----+
\ | | | | | | | | | \_ _/
\ +---+ P +----+ P +--+ +----+ | \____/
\___ | | | | /
\ +----+__ +----+ DetNet-1 DetNet-2
| \_____/ \___________/ |
| |
| | End-to-End service | | | |
<------------------------------------------------------------->
| | DetNet service | | | |
| <------------------------------------------------> |
| | | | | |
Figure 5: DetNet Service Reference Model (multi-domain)
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DetNet User Network Interfaces (DetNet-UNIs) ("U" in Figure 5) are
assumed in this document to be packet-based reference points and
provide connectivity over the packet network. A DetNet-UNI may
provide multiple functions, e.g., it may add networking technology
specific encapsulation to the DetNet flows if necessary; it may
provide status of the availability of the resources associated with a
reservation; it may provide a synchronization service for the end
system; it may carry enough signaling to place the reservation in a
network without a controller, or if the controller only deals with
the network but not the end systems. Internal reference points of
end systems (between the application and the NIC) are more
challenging from control perspective and they may have extra
requirements (e.g., in-order delivery is expected in end system
internal reference points, whereas it is considered optional over the
DetNet-UNI).
4.2. DetNet systems
4.2.1. End system
The traffic characteristics of an App-flow can be CBR (constant bit
rate) or VBR (variable bit rate) and can have Layer-1 or Layer-2 or
Layer-3 encapsulation (e.g., TDM (time-division multiplexing),
Ethernet, IP). These characteristics are considered as input for
resource reservation and might be simplified to ensure determinism
during packet forwarding (e.g., making reservations for the peak rate
of VBR traffic, etc.).
An end system may or may not be DetNet forwarding sub-layer aware or
DetNet service sub-layer aware. That is, an end system may or may
not contain DetNet specific functionality. End systems with DetNet
functionalities may have the same or different forwarding sub-layer
as the connected DetNet domain. Categorization of end systems are
shown in Figure 6.
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End system
|
|
| DetNet aware ?
/ \
+------< >------+
NO | \ / | YES
| v |
DetNet unaware |
End system |
| Service/Forwarding
| sub-layer
/ \ aware ?
+--------< >-------------+
f-aware | \ / | s-aware
| v |
| | both |
| | |
DetNet f-aware | DetNet s-aware
End system | End system
v
DetNet sf-aware
End system
Figure 6: Categorization of end systems
Note some known use case examples for end systems:
o DetNet unaware: The classic case requiring service proxies.
o DetNet f-aware: A DetNet forwarding sub-layer aware system. It
knows about some TSN functions (e.g., reservation), but not about
service protection.
o DetNet s-aware: A DetNet service sub-layer aware system. It
supplies sequence numbers, but doesn't know about resource
allocation.
o DetNet sf-aware: A full functioning DetNet end system, it has
DetNet functionalities and usually the same forwarding paradigm as
the connected DetNet domain. It can be treated as an integral
part of the DetNet domain.
4.2.2. DetNet edge, relay, and transit nodes
As shown in Figure 3, DetNet edge nodes providing proxy service and
DetNet relay nodes providing the DetNet service sub-layer are DetNet-
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aware, and DetNet transit nodes need only be aware of the DetNet
forwarding sub-layer.
In general, if a DetNet flow passes through one or more DetNet-
unaware network nodes between two DetNet nodes providing the DetNet
forwarding sub-layer for that flow, there is a potential for
disruption or failure of the DetNet QoS. A network administrator
needs to ensure that the DetNet-unaware network nodes are configured
to minimize the chances of packet loss and delay, and provision
enough extra buffer space in the DetNet transit node following the
DetNet-unaware network nodes to absorb the induced latency
variations.
4.3. DetNet flows
4.3.1. DetNet flow types
A DetNet flow can have different formats while its packets are
forwarded between the peer end systems depending on the type of the
end systems. Corresponding to the end system types, the following
possible types / formats of a DetNet flow are distinguished in this
document. The different flow types have different requirements to
DetNet nodes.
o App-flow: the payload (data) carried over a DetNet flow between
DetNet unaware end systems. An app-flow does not contain any
DetNet related attributes and does not imply any specific
requirement on DetNet nodes.
o DetNet-f-flow: specific format of a DetNet flow. It only requires
the resource allocation features provided by the DetNet forwarding
sub-layer.
o DetNet-s-flow: specific format of a DetNet flow. It only requires
the service protection feature ensured by the DetNet service sub-
layer.
o DetNet-sf-flow: specific format of a DetNet flow. It requires
both DetNet service sub-layer and DetNet forwarding sub-layer
functions during forwarding.
4.3.2. Source transmission behavior
For the purposes of resource allocation, DetNet flows can be
synchronous or asynchronous. In synchronous DetNet flows, at least
the DetNet nodes (and possibly the end systems) are closely time
synchronized, typically to better than 1 microsecond. By
transmitting packets from different DetNet flows or classes of DetNet
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flows at different times, using repeating schedules synchronized
among the DetNet nodes, resources such as buffers and link bandwidth
can be shared over the time domain among different DetNet flows.
There is a tradeoff among techniques for synchronous DetNet flows
between the burden of fine-grained scheduling and the benefit of
reducing the required resources, especially buffer space.
In contrast, asynchronous DetNet flows are not coordinated with a
fine-grained schedule, so relay and end systems must assume worst-
case interference among DetNet flows contending for buffer resources.
Asynchronous DetNet flows are characterized by:
o A maximum packet size;
o An observation interval; and
o A maximum number of transmissions during that observation
interval.
These parameters, together with knowledge of the protocol stack used
(and thus the size of the various headers added to a packet), provide
the bandwidth that is needed for the DetNet flow.
The source is required not to exceed these limits in order to obtain
DetNet service. If the source transmits less data than this limit
allows, the unused resource such as link bandwidth can be made
available by the DetNet system to non-DetNet packets as long as all
guarantees are fulfilled. However, making those resources available
to DetNet packets in other DetNet flows would serve no purpose.
Those other DetNet flows have their own dedicated resources, on the
assumption that all DetNet flows can use all of their resources over
a long period of time.
There is no expectation in DetNet for App-flows to be responsive to
congestion control [RFC2914] or explicit congestion notification
[RFC3168]. The assumption is that a DetNet flow, to be useful, must
be delivered in its entirety. That is, while any useful application
is written to expect a certain number of lost packets, the real-time
applications of interest to DetNet demand that the loss of data due
to the network is a rare event.
Although DetNet strives to minimize the changes required of an
application to allow it to shift from a special-purpose digital
network to an Internet Protocol network, one fundamental shift in the
behavior of network applications is impossible to avoid: the
reservation of resources before the application starts. In the first
place, a network cannot deliver finite latency and practically zero
packet loss to an arbitrarily high offered load. Secondly, achieving
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practically zero packet loss for DetNet flows means that DetNet nodes
have to dedicate buffer resources to specific DetNet flows or to
classes of DetNet flows. The requirements of each reservation have
to be translated into the parameters that control each DetNet
system's queuing, shaping, and scheduling functions and delivered to
the DetNet nodes and end systems.
All nodes in a DetNet domain are expected to support the data
behavior required to deliver a particular DetNet service. If a node
itself is not DetNet service aware, the DetNet nodes that are
adjacent to such non-DetNet aware nodes must ensure that the non-
DetNet aware node is provisioned to appropriately support the DetNet
service. For example, an IEEE 802.1 TSN node may be used to
interconnect DetNet aware nodes, and these DetNet nodes can map
DetNet flows to 802.1 TSN flows. Another example, an MPLS-TE or TP
domain may be used to interconnect DetNet aware nodes, and these
DetNet nodes can map DetNet flows to TE LSPs which can provide the
QoS requirements of the DetNet service.
4.3.3. Incomplete Networks
The presence in the network of intermediate nodes or subnets that are
not fully capable of offering DetNet services complicates the ability
of the intermediate nodes and/or controller to allocate resources, as
extra buffering must be allocated at points downstream from the non-
DetNet intermediate node for a DetNet flow. This extra buffering may
increase latency and/or jitter.
4.4. Traffic Engineering for DetNet
Traffic Engineering Architecture and Signaling (TEAS) [TEAS] defines
traffic-engineering architectures for generic applicability across
packet and non-packet networks. From a TEAS perspective, Traffic
Engineering (TE) refers to techniques that enable operators to
control how specific traffic flows are treated within their networks.
Because if its very nature of establishing explicit optimized paths,
Deterministic Networking can be seen as a new, specialized branch of
Traffic Engineering, and inherits its architecture with a separation
into planes.
The Deterministic Networking architecture is thus composed of three
planes, a (User) Application Plane, a Controller Plane, and a Network
Plane, which echoes that of Figure 1 of Software-Defined Networking
(SDN): Layers and Architecture Terminology [RFC7426], and the
Controllers identified in [RFC8453] and [RFC7149].
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4.4.1. The Application Plane
Per [RFC7426], the Application Plane includes both applications and
services. In particular, the Application Plane incorporates the User
Agent, a specialized application that interacts with the end user /
operator and performs requests for Deterministic Networking services
via an abstract Flow Management Entity, (FME) which may or may not be
collocated with (one of) the end systems.
At the Application Plane, a management interface enables the
negotiation of flows between end systems. An abstraction of the flow
called a Traffic Specification (TSpec) provides the representation.
This abstraction is used to place a reservation over the (Northbound)
Service Interface and within the Application plane. It is associated
with an abstraction of location, such as IP addresses and DNS names,
to identify the end systems and possibly specify DetNet nodes.
4.4.2. The Controller Plane
The Controller Plane corresponds to the aggregation of the Control
and Management Planes in [RFC7426], though Common Control and
Measurement Plane (CCAMP) [CCAMP] makes an additional distinction
between management and measurement. When the logical separation of
the Control, Measurement and other Management entities is not
relevant, the term Controller Plane is used for simplicity to
represent them all, and the term Controller Plane Function (CPF)
refers to any device operating in that plane, whether is it a Path
Computation Element (PCE) [RFC4655], or a Network Management entity
(NME), or a distributed control plane. The CPF is a core element of
a controller, in charge of computing Deterministic paths to be
applied in the Network Plane.
A (Northbound) Service Interface enables applications in the
Application Plane to communicate with the entities in the Controller
Plane as illustrated in Figure 7.
One or more CPF(s) collaborate to implement the requests from the FME
as Per-Flow Per-Hop Behaviors installed in the DetNet nodes for each
individual flow. The CPFs place each flow along a deterministic
sequence of DetNet nodes so as to respect per-flow constraints such
as security and latency, and optimize the overall result for metrics
such as an abstract aggregated cost. The deterministic sequence can
typically be more complex than a direct sequence and include
redundant paths, with one or more packet replication and elimination
points. Scaling to larger networks is discussed in Section 4.9.
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4.4.3. The Network Plane
The Network Plane represents the network devices and protocols as a
whole, regardless of the Layer at which the network devices operate.
It includes Forwarding Plane (data plane), Application, and
Operational Plane (e.g., OAM) aspects.
The network Plane comprises the Network Interface Cards (NIC) in the
end systems, which are typically IP hosts, and DetNet nodes, which
are typically IP routers and MPLS switches. Network-to-Network
Interfaces such as used for Traffic Engineering path reservation in
[RFC5921], as well as User-to-Network Interfaces (UNI) such as
provided by the Local Management Interface (LMI) between network and
end systems, are both part of the Network Plane, both in the control
plane and the data plane.
A Southbound (Network) Interface enables the entities in the
Controller Plane to communicate with devices in the Network Plane as
illustrated in Figure 7. This interface leverages and extends TEAS
to describe the physical topology and resources in the Network Plane.
End End
System System
-+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
CPF CPF CPF CPF
-+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
DetNet DetNet DetNet DetNet
Node Node Node Node
NIC NIC
DetNet DetNet DetNet DetNet
Node Node Node Node
Figure 7: Northbound and Southbound interfaces
The DetNet nodes (and possibly the end systems NIC) expose their
capabilities and physical resources to the controller (the CPF), and
update the CPFs with their dynamic perception of the topology, across
the Southbound Interface. In return, the CPFs set the per-flow paths
up, providing a Flow Characterization that is more tightly coupled to
the DetNet node Operation than a TSpec.
At the Network plane, DetNet nodes may exchange information regarding
the state of the paths, between adjacent DetNet nodes and possibly
with the end systems, and forward packets within constraints
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associated to each flow, or, when unable to do so, perform a last
resort operation such as drop or declassify.
This document focuses on the Southbound interface and the operation
of the Network Plane.
4.5. Queuing, Shaping, Scheduling, and Preemption
DetNet achieves bounded delivery latency by reserving bandwidth and
buffer resources at each DetNet node along the path of the DetNet
flow. The reservation itself is not sufficient, however.
Implementors and users of a number of proprietary and standard real-
time networks have found that standards for specific data plane
techniques are required to enable these assurances to be made in a
multi-vendor network. The fundamental reason is that latency
variation in one DetNet system results in the need for extra buffer
space in the next-hop DetNet system(s), which in turn, increases the
worst-case per-hop latency.
Standard queuing and transmission selection algorithms allow traffic
engineering Section 4.4 to compute the latency contribution of each
DetNet node to the end-to-end latency, to compute the amount of
buffer space required in each DetNet node for each incremental DetNet
flow, and most importantly, to translate from a flow specification to
a set of values for the managed objects that control each relay or
end system. For example, the IEEE 802.1 WG has specified (and is
specifying) a set of queuing, shaping, and scheduling algorithms that
enable each DetNet node, and/or a central controller, to compute
these values. These algorithms include:
o A credit-based shaper [IEEE802.1Qav] (superseded by
[IEEE802.1Q-2018]).
o Time-gated queues governed by a rotating time schedule based on
synchronized time [IEEE802.1Qbv] (superseded by
[IEEE802.1Q-2018]).
o Synchronized double (or triple) buffers driven by synchronized
time ticks. [IEEE802.1Qch] (superseded by [IEEE802.1Q-2018]).
o Pre-emption of an Ethernet packet in transmission by a packet with
a more stringent latency requirement, followed by the resumption
of the preempted packet [IEEE802.1Qbu] (superseded by
[IEEE802.1Q-2018]), [IEEE802.3br] (superseded by
[IEEE802.3-2018]).
While these techniques are currently embedded in Ethernet
[IEEE802.3-2018] and bridging standards, we can note that they are
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all, except perhaps for packet preemption, equally applicable to
other media than Ethernet, and to routers as well as bridges. Other
media may have its own methods, see, e.g.,
[I-D.ietf-6tisch-architecture], [RFC7554]. Further techniques are
defined by the IETF, e.g., [RFC8289] and [RFC8033]. DetNet may
include such definitions in the future, or may define how these
techniques can be used by DetNet nodes.
4.6. Service instance
A Service instance represents all the functions required on a DetNet
node to allow the end-to-end service between the UNIs.
The DetNet network general reference model is shown in Figure 8 for a
DetNet service scenario (i.e., between two DetNet-UNIs). In this
figure, end systems ("A" and "B") are connected directly to the edge
nodes of an IP/MPLS network ("PE1" and "PE2"). End systems
participating in DetNet communication may require connectivity before
setting up an App-flow that requires the DetNet service. Such a
connectivity related service instance and the one dedicated for
DetNet service share the same access. Packets belonging to a DetNet
flow are selected by a filter configured on the access ("F1" and
"F2"). As a result, data flow specific access ("access-A + F1" and
"access-B + F2") are terminated in the flow specific service instance
("SI-1" and "SI-2"). A tunnel is used to provide connectivity
between the service instances.
The tunnel is exclusively used for the packets of the DetNet flow
between "SI-1" and "SI-2". The service instances are configured to
implement DetNet functions and a flow specific DetNet forwarding.
The service instance and the tunnel may or may not be shared by
multiple DetNet flows. Sharing the service instance by multiple
DetNet flows requires properly populated forwarding tables of the
service instance.
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access-A access-B
<-----> <-------- tunnel ----------> <----->
+---------+ ___ _ +---------+
End system | +----+ | / \/ \_ | +----+ | End system
"A" -------F1+ | | / \ | | +F2----- "B"
| | +========+ IP/MPLS +=======+ | |
| |SI-1| | \__ Net._/ | |SI-2| |
| +----+ | \____/ | +----+ |
|PE1 | | PE2|
+---------+ +---------+
Figure 8: DetNet network general reference model
The tunnel between the service instances may have some special
characteristics. For example, in case of a DetNet L3 service, there
are differences in the usage of the PW for DetNet traffic compared to
the network model described in [RFC6658]. In the DetNet scenario,
the PW is likely to be used exclusively by the DetNet flow, whereas
[RFC6658] states: "The packet PW appears as a single point-to-point
link to the client layer. Network-layer adjacency formation and
maintenance between the client equipment will follow the normal
practice needed to support the required relationship in the client
layer ... This packet PseudoWire is used to transport all of the
required Layer-2 and Layer-3 protocols between LSR1 and LSR2".
Further details are network technology specific and can be found in
[I-D.ietf-detnet-dp-sol-mpls] and [I-D.ietf-detnet-dp-sol-ip].
4.7. Flow identification at technology borders
This section discusses what needs to be done at technology borders
including Ethernet as one of the technologies. Flow identification
for MPLS and IP data planes are described in
[I-D.ietf-detnet-dp-sol-mpls] and [I-D.ietf-detnet-dp-sol-ip],
respectively.
4.7.1. Exporting flow identification
A DetNet node may need to map specific flows to lower layer flows (or
Streams) in order to provide specific queuing and shaping services
for specific flows. For example:
o A non-IP, strictly L2 source end system X may be sending multiple
flows to the same L2 destination end system Y. Those flows may
include DetNet flows with different QoS requirements, and may
include non-DetNet flows.
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o A router may be sending any number of flows to another router.
Again, those flows may include DetNet flows with different QoS
requirements, and may include non-DetNet flows.
o Two routers may be separated by bridges. For these bridges to
perform any required per-flow queuing and shaping, they must be
able to identify the individual flows.
o A Label Edge Router (LER) may have a Label Switched Path (LSP) set
up for handling traffic destined for a particular IP address
carrying only non-DetNet flows. If a DetNet flow to that same
address is requested, a separate LSP may be needed, in order that
all of the Label Switch Routers (LSRs) along the path to the
destination give that flow special queuing and shaping.
The need for a lower-layer node to be aware of individual higher-
layer flows is not unique to DetNet. But, given the endless
complexity of layering and relayering over tunnels that is available
to network designers, DetNet needs to provide a model for flow
identification that is better than packet inspection. That is not to
say that packet inspection to Layer-4 or Layer-5 addresses will not
be used, or the capability standardized; but, there are alternatives.
A DetNet relay node can connect DetNet flows on different paths using
different flow identification methods. For example:
o A single unicast DetNet flow passing from router A through a
bridged network to router B may be assigned a TSN Stream
identifier that is unique within that bridged network. The
bridges can then identify the flow without accessing higher-layer
headers. Of course, the receiving router must recognize and
accept that TSN Stream.
o A DetNet flow passing from LSR A to LSR B may be assigned a
different label than that used for other flows to the same IP
destination.
In any of the above cases, it is possible that an existing DetNet
flow can be an aggregate carrying multiple other DetNet flows. (Not
to be confused with DetNet compound vs. member flows.) Of course,
this requires that the aggregate DetNet flow be provisioned properly
to carry the aggregated flows.
Thus, rather than packet inspection, there is the option to export
higher-layer information to the lower layer. The requirement to
support one or the other method for flow identification (or both) is
a complexity that is part of DetNet control models.
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4.7.2. Flow attribute mapping between layers
Forwarding of packets of DetNet flows over multiple technology
domains may require that lower layers are aware of specific flows of
higher layers. Such an "exporting of flow identification" is needed
each time when the forwarding paradigm is changed on the forwarding
path (e.g., two LSRs are interconnected by a L2 bridged domain,
etc.). The three representative forwarding methods considered for
deterministic networking are:
o IP routing
o MPLS label switching
o Ethernet bridging
A packet with corresponding Flow-IDs is illustrated in Figure 9,
which also indicates where each Flow-ID can be added or removed.
add/remove add/remove
Eth Flow-ID IP Flow-ID
| |
v v
+-----------------------------------------------------------+
| | | | |
| Eth | MPLS | IP | Application data |
| | | | |
+-----------------------------------------------------------+
^
|
add/remove
MPLS Flow-ID
Figure 9: Packet with multiple Flow-IDs
The additional (domain specific) Flow-ID can be
o created by a domain specific function or
o derived from the Flow-ID added to the App-flow.
The Flow-ID must be unique inside a given domain. Note that the
Flow-ID added to the App-flow is still present in the packet, but
some nodes may lack the function to recognize it; that's why the
additional Flow-ID is added.
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4.7.3. Flow-ID mapping examples
IP nodes and MPLS nodes are assumed to be configured to push such an
additional (domain specific) Flow-ID when sending traffic to an
Ethernet switch (as shown in the examples below).
Figure 10 shows a scenario where an IP end system ("IP-A") is
connected via two Ethernet switches ("ETH-n") to an IP router ("IP-
1").
IP domain
<-----------------------------------------------
+======+ +======+
|L3-ID | |L3-ID |
+======+ /\ +-----+ +======+
/ \ Forward as | |
/IP-A\ per ETH-ID |IP-1 | Recognize
Push ------> +-+----+ | +---+-+ <----- ETH-ID
ETH-ID | +----+-----+ |
| v v |
| +-----+ +-----+ |
+------+ | | +---------+
+......+ |ETH-1+----+ETH-2| +======+
.L3-ID . +-----+ +-----+ |L3-ID |
+======+ +......+ +======+
|ETH-ID| .L3-ID . |ETH-ID|
+======+ +======+ +------+
|ETH-ID|
+======+
Ethernet domain
<---------------->
Figure 10: IP nodes interconnected by an Ethernet domain
End system "IP-A" uses the original App-flow specific ID ("L3-ID"),
but as it is connected to an Ethernet domain it has to push an
Ethernet-domain specific flow-ID ("ETH-ID") before sending the packet
to "ETH-1" node. Ethernet switch "ETH-1" can recognize the data flow
based on the "ETH-ID" and it does forwarding toward "ETH-2". "ETH-2"
switches the packet toward the IP router. "IP-1" must be configured
to receive the Ethernet Flow-ID specific multicast flow, but (as it
is an L3 node) it decodes the data flow ID based on the "L3-ID"
fields of the received packet.
Figure 11 shows a scenario where MPLS domain nodes ("PE-n" and "P-m")
are connected via two Ethernet switches ("ETH-n").
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MPLS domain
<----------------------------------------------->
+=======+ +=======+
|MPLS-ID| |MPLS-ID|
+=======+ +-----+ +-----+ +=======+ +-----+
| | Forward as | | | |
|PE-1 | per ETH-ID | P-2 +-----------+ PE-2|
Push -----> +-+---+ | +---+-+ +-----+
ETH-ID | +-----+----+ | \ Recognize
| v v | +-- ETH-ID
| +-----+ +-----+ |
+---+ | | +----+
+.......+ |ETH-1+----+ETH-2| +=======+
.MPLS-ID. +-----+ +-----+ |MPLS-ID|
+=======+ +=======+
|ETH-ID | +.......+ |ETH-ID |
+=======+ .MPLS-ID. +-------+
+=======+
|ETH-ID |
+=======+
Ethernet domain
<---------------->
Figure 11: MPLS nodes interconnected by an Ethernet domain
"PE-1" uses the MPLS specific ID ("MPLS-ID"), but as it is connected
to an Ethernet domain it has to push an Ethernet-domain specific
flow-ID ("ETH-ID") before sending the packet to "ETH-1". Ethernet
switch "ETH-1" can recognize the data flow based on the "ETH-ID" and
it does forwarding toward "ETH-2". "ETH-2" switches the packet
toward the MPLS node ("P-2"). "P-2" must be configured to receive
the Ethernet Flow-ID specific multicast flow, but (as it is an MPLS
node) it decodes the data flow ID based on the "MPLS-ID" fields of
the received packet.
One can appreciate from the above example that, when the means used
for DetNet flow identification is altered or exported, the means for
encoding the sequence number information must similarly be altered or
exported.
4.8. Advertising resources, capabilities and adjacencies
Provisioning of DetNet requires knowledge about:
o Details of the DetNet system's capabilities that are required in
order to accurately allocate that DetNet system's resources, as
well as other DetNet systems' resources. This includes, for
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example, which specific queuing and shaping algorithms are
implemented (Section 4.5), the number of buffers dedicated for
DetNet allocation, and the worst-case forwarding delay and
misordering.
o The actual state of a DetNet node's DetNet resources.
o The identity of the DetNet system's neighbors, and the
characteristics of the link(s) between the DetNet systems,
including the latency of the links (in nanoseconds).
4.9. Scaling to larger networks
Reservations for individual DetNet flows require considerable state
information in each DetNet node, especially when adequate fault
mitigation (Section 3.3.2) is required. The DetNet data plane, in
order to support larger numbers of DetNet flows, must support the
aggregation of DetNet flows. Such aggregated flows can be viewed by
the DetNet nodes' data plane largely as individual DetNet flows.
Without such aggregation, the per-relay system may limit the scale of
DetNet networks. Example techniques that may be used include MPLS
hierarchy and IP DiffServ Code Points (DSCPs).
4.10. Compatibility with Layer-2
Standards providing similar capabilities for bridged networks (only)
have been and are being generated in the IEEE 802 LAN/MAN Standards
Committee. The present architecture describes an abstract model that
can be applicable both at Layer-2 and Layer-3, and over links not
defined by IEEE 802.
DetNet enabled end systems and DetNet nodes can be interconnected by
sub-networks, i.e., Layer-2 technologies. These sub-networks will
provide DetNet compatible service for support of DetNet traffic.
Examples of sub-network technologies include MPLS TE, 802.1 TSN, and
a point-to-point OTN link. Of course, multi-layer DetNet systems may
be possible too, where one DetNet appears as a sub-network, and
provides service to, a higher layer DetNet system.
5. Security Considerations
Security considerations for DetNet are described in detail in
[I-D.ietf-detnet-security]. This section considers exclusively
security considerations which are specific to the DetNet
architecture.
Security aspects which are unique to DetNet are those whose aim is to
provide the specific quality of service aspects of DetNet, which are
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primarily to deliver data flows with extremely low packet loss rates
and bounded end-to-end delivery latency. A DetNet may be implemented
using MPLS and/or IP (including both v4 and v6) technologies, and
thus inherits the security properties of those technologies at both
the data plane and the control plane.
Security considerations for DetNet are constrained (compared to, for
example, the open Internet) because DetNet is defined to operate only
within a single administrative domain (see Section 1). The primary
considerations are to secure the request and control of DetNet
resources, maintain confidentiality of data traversing the DetNet,
and provide the availability of the DetNet quality of service.
To secure the request and control of DetNet resources, authentication
and authorization can be used for each device connected to a DetNet
domain, most importantly to network controller devices. Control of a
DetNet network may be centralized or distributed (within a single
administrative domain). In the case of centralized control,
precedent for security considerations as defined for Abstraction and
Control of Traffic Engineered Networks (ACTN) can be found in
[RFC8453], Section 9. In the case of distributed control protocols,
DetNet security is expected to be provided by the security properties
of the protocols in use. In any case, the result is that
manipulation of administratively configurable parameters is limited
to authorized entities.
To maintain confidentiality of data traversing the DetNet,
application flows can be protected through whatever means is provided
by the underlying technology. For example, encryption may be used,
such as that provided by IPSec [RFC4301] for IP flows and by MACSec
[IEEE802.1AE-2018] for Ethernet (Layer-2) flows.
DetNet flows are identified on a per-flow basis, which may provide
attackers with additional information about the data flows (when
compared to networks that do not include per-flow identification).
This is an inherent property of DetNet which has security
implications that should be considered when determining if DetNet is
a suitable technology for any given use case.
To provide uninterrupted availability of the DetNet quality of
service, provisions can be made against DOS attacks and delay
attacks. To protect against DOS attacks, excess traffic due to
malicious or malfunctioning devices can be prevented or mitigated,
for example through the use of traffic admission control applied at
the input of a DetNet domain, as described in Section 3.2.1, and
through the fault mitigation methods described in Section 3.3.2. To
prevent DetNet packets from being delayed by an entity external to a
DetNet domain, DetNet technology definition can allow for the
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mitigation of Man-In-The-Middle attacks, for example through use of
authentication and authorization of devices within the DetNet domain.
Because DetNet mechanisms or applications that rely on DetNet can
make heavy use of methods that require precise time synchronization,
the accuracy, availability, and integrity of time synchronization is
of critical importance. Extensive discussion of this topic can be
found in [RFC7384].
DetNet use cases are known to have widely divergent security
requirements. The intent of this section is to provide a baseline
for security considerations which are common to all DetNet designs
and implementations, without burdening individual designs with
specifics of security infrastructure which may not be germane to the
given use case. Designers and implementers of DetNet systems are
expected to take use case specific considerations into account in
their DetNet designs and implementations.
6. Privacy Considerations
DetNet provides a Quality of Service (QoS), and the generic
considerations for such mechanisms apply. In particular, such
markings allow for an attacker to correlate flows or to select
particular types of flow for more detailed inspection.
However, the requirement for every (or almost every) node along the
path of a DetNet flow to identify DetNet flows may present an
additional attack surface for privacy, should the DetNet paradigm be
found useful in broader environments.
7. IANA Considerations
This document does not require an action from IANA.
8. Acknowledgements
The authors wish to thank Lou Berger, David Black, Stewart Bryant,
Rodney Cummings, Ethan Grossman, Craig Gunther, Marcel Kiessling,
Rudy Klecka, Jouni Korhonen, Erik Nordmark, Shitanshu Shah, Wilfried
Steiner, George Swallow, Michael Johas Teener, Pat Thaler, Thomas
Watteyne, Patrick Wetterwald, Karl Weber, Anca Zamfir, for their
various contributions to this work.
9. Informative References
[BUFFERBLOAT]
Gettys, J. and K. Nichols, "Bufferbloat: Dark Buffers in
the Internet", January 2012.
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[CCAMP] IETF, "Common Control and Measurement Plane Working
Group",
<https://datatracker.ietf.org/doc/charter-ietf-ccamp/>.
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-20 (work
in progress), March 2019.
[I-D.ietf-detnet-dp-sol-ip]
Korhonen, J. and B. Varga, "DetNet IP Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-ip-02 (work in
progress), March 2019.
[I-D.ietf-detnet-dp-sol-mpls]
Korhonen, J. and B. Varga, "DetNet MPLS Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-mpls-02 (work in
progress), March 2019.
[I-D.ietf-detnet-problem-statement]
Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", draft-ietf-detnet-problem-statement-09 (work
in progress), December 2018.
[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-04 (work in progress), March 2019.
[I-D.ietf-detnet-use-cases]
Grossman, E., "Deterministic Networking Use Cases", draft-
ietf-detnet-use-cases-20 (work in progress), December
2018.
[IEC62439-3-2016]
International Electrotechnical Commission (IEC) TC 65/SC
65C - Industrial networks, "IEC 62439-3:2016 Industrial
communication networks - High availability automation
networks - Part 3: Parallel Redundancy Protocol (PRP) and
High-availability Seamless Redundancy (HSR)", 2016,
<https://webstore.iec.ch/publication/24447>.
[IEEE802.1AE-2018]
IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
Security (MACsec)", 2018,
<https://ieeexplore.ieee.org/document/8585421>.
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[IEEE802.1BA]
IEEE Standards Association, "IEEE Std 802.1BA-2011 Audio
Video Bridging (AVB) Systems", 2011,
<https://ieeexplore.ieee.org/document/6032690/>.
[IEEE802.1CB]
IEEE Standards Association, "IEEE Std 802.1CB-2017 Frame
Replication and Elimination for Reliability", 2017,
<https://ieeexplore.ieee.org/document/8091139/>.
[IEEE802.1Q-2018]
IEEE Standards Association, "IEEE Std 802.1Q-2018 Bridges
and Bridged Networks", 2018,
<https://ieeexplore.ieee.org/document/8403927>.
[IEEE802.1Qav]
IEEE Standards Association, "IEEE Std 802.1Qav-2009
Bridges and Bridged Networks - Amendment 12: Forwarding
and Queuing Enhancements for Time-Sensitive Streams",
2009, <https://ieeexplore.ieee.org/document/5375704/>.
[IEEE802.1Qbu]
IEEE Standards Association, "IEEE Std 802.1Qbu-2016
Bridges and Bridged Networks - Amendment 26: Frame
Preemption", 2016,
<https://ieeexplore.ieee.org/document/7553415/>.
[IEEE802.1Qbv]
IEEE Standards Association, "IEEE Std 802.1Qbv-2015
Bridges and Bridged Networks - Amendment 25: Enhancements
for Scheduled Traffic", 2015,
<https://ieeexplore.ieee.org/document/7572858/>.
[IEEE802.1Qch]
IEEE Standards Association, "IEEE Std 802.1Qch-2017
Bridges and Bridged Networks - Amendment 29: Cyclic
Queuing and Forwarding", 2017,
<https://ieeexplore.ieee.org/document/7961303/>.
[IEEE802.1TSNTG]
IEEE Standards Association, "IEEE 802.1 Time-Sensitive
Networking Task Group", <http://www.ieee802.org/1/tsn>.
[IEEE802.3-2018]
IEEE Standards Association, "IEEE Std 802.3-2018 Standard
for Ethernet", 2018,
<https://ieeexplore.ieee.org/document/8457469>.
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[IEEE802.3br]
IEEE Standards Association, "IEEE Std 802.3br-2016
Standard for Ethernet Amendment 5: Specification and
Management Parameters for Interspersing Express Traffic",
2016, <http://ieeexplore.ieee.org/document/7900321/>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <https://www.rfc-editor.org/info/rfc2205>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<https://www.rfc-editor.org/info/rfc5921>.
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[RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport
Profile (MPLS-TP) Survivability Framework", RFC 6372,
DOI 10.17487/RFC6372, September 2011,
<https://www.rfc-editor.org/info/rfc6372>.
[RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
"Packet Pseudowire Encapsulation over an MPLS PSN",
RFC 6658, DOI 10.17487/RFC6658, July 2012,
<https://www.rfc-editor.org/info/rfc6658>.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
<https://www.rfc-editor.org/info/rfc7149>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <https://www.rfc-editor.org/info/rfc7426>.
[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015,
<https://www.rfc-editor.org/info/rfc7554>.
[RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF
Recommendations Regarding Active Queue Management",
BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,
<https://www.rfc-editor.org/info/rfc7567>.
[RFC7813] Farkas, J., Ed., Bragg, N., Unbehagen, P., Parsons, G.,
Ashwood-Smith, P., and C. Bowers, "IS-IS Path Control and
Reservation", RFC 7813, DOI 10.17487/RFC7813, June 2016,
<https://www.rfc-editor.org/info/rfc7813>.
[RFC8033] Pan, R., Natarajan, P., Baker, F., and G. White,
"Proportional Integral Controller Enhanced (PIE): A
Lightweight Control Scheme to Address the Bufferbloat
Problem", RFC 8033, DOI 10.17487/RFC8033, February 2017,
<https://www.rfc-editor.org/info/rfc8033>.
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[RFC8227] Cheng, W., Wang, L., Li, H., van Helvoort, H., and J.
Dong, "MPLS-TP Shared-Ring Protection (MSRP) Mechanism for
Ring Topology", RFC 8227, DOI 10.17487/RFC8227, August
2017, <https://www.rfc-editor.org/info/rfc8227>.
[RFC8289] Nichols, K., Jacobson, V., McGregor, A., Ed., and J.
Iyengar, Ed., "Controlled Delay Active Queue Management",
RFC 8289, DOI 10.17487/RFC8289, January 2018,
<https://www.rfc-editor.org/info/rfc8289>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
[TEAS] IETF, "Traffic Engineering Architecture and Signaling
Working Group",
<https://datatracker.ietf.org/doc/charter-ietf-teas/>.
Authors' Addresses
Norman Finn
Huawei
3101 Rio Way
Spring Valley, California 91977
US
Phone: +1 925 980 6430
Email: norman.finn@mail01.huawei.com
Pascal Thubert
Cisco Systems
Village d'Entreprises Green Side
400, Avenue de Roumanille
Batiment T3
Biot - Sophia Antipolis 06410
FRANCE
Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com
Finn, et al. Expires November 7, 2019 [Page 44]
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Balazs Varga
Ericsson
Magyar tudosok korutja 11
Budapest 1117
Hungary
Email: balazs.a.varga@ericsson.com
Janos Farkas
Ericsson
Magyar tudosok korutja 11
Budapest 1117
Hungary
Email: janos.farkas@ericsson.com
Finn, et al. Expires November 7, 2019 [Page 45]
