draft-ietf-detnet-bounded-latency-02.txt   draft-ietf-detnet-bounded-latency-03.txt 
DetNet N. Finn DetNet N. Finn
Internet-Draft Huawei Technologies Co. Ltd Internet-Draft Huawei Technologies Co. Ltd
Intended status: Informational J-Y. Le Boudec Intended status: Informational J-Y. Le Boudec
Expires: May 6, 2021 E. Mohammadpour Expires: September 23, 2021 E. Mohammadpour
EPFL EPFL
J. Zhang J. Zhang
Huawei Technologies Co. Ltd Huawei Technologies Co. Ltd
B. Varga B. Varga
J. Farkas J. Farkas
Ericsson Ericsson
November 2, 2020 March 22, 2021
DetNet Bounded Latency DetNet Bounded Latency
draft-ietf-detnet-bounded-latency-02 draft-ietf-detnet-bounded-latency-03
Abstract Abstract
This document presents a timing model for Deterministic Networking This document references specific queuing mechanisms, defined in
(DetNet), so that existing and future standards can achieve the other documents, that can be used to control packet transmission at
DetNet quality of service features of bounded latency and zero each output port and achieve the DetNet qualities of service. This
congestion loss. It defines requirements for resource reservation document presents a timing model for sources, destinations, and the
protocols or servers. It calls out queuing mechanisms, defined in DetNet transit nodes that relay packets that is applicable to all of
other documents, that can provide the DetNet quality of service. those referenced queuing mechanisms. Using the model presented in
this document, it should be possible for an implementor, user, or
standards development organization to select a particular set of
queuing mechanisms for each device in a DetNet network, and to select
a resource reservation algorithm for that network, so that those
elements can work together to provide the DetNet service.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 6, 2021. This Internet-Draft will expire on September 23, 2021.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 4
3. DetNet bounded latency model . . . . . . . . . . . . . . . . 3 3. DetNet bounded latency model . . . . . . . . . . . . . . . . 4
3.1. Flow creation . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Flow admission . . . . . . . . . . . . . . . . . . . . . 4
3.1.1. Static flow latency calculation . . . . . . . . . . . 4 3.1.1. Static latency calculation . . . . . . . . . . . . . 4
3.1.2. Dynamic flow latency calculation . . . . . . . . . . 5 3.1.2. Dynamic latency calculation . . . . . . . . . . . . . 5
3.2. Relay node model . . . . . . . . . . . . . . . . . . . . 6 3.2. Relay node model . . . . . . . . . . . . . . . . . . . . 6
4. Computing End-to-end Delay Bounds . . . . . . . . . . . . . . 8 4. Computing End-to-end Delay Bounds . . . . . . . . . . . . . . 8
4.1. Non-queuing delay bound . . . . . . . . . . . . . . . . . 8 4.1. Non-queuing delay bound . . . . . . . . . . . . . . . . . 8
4.2. Queuing delay bound . . . . . . . . . . . . . . . . . . . 8 4.2. Queuing delay bound . . . . . . . . . . . . . . . . . . . 9
4.2.1. Per-flow queuing mechanisms . . . . . . . . . . . . . 9 4.2.1. Per-flow queuing mechanisms . . . . . . . . . . . . . 9
4.2.2. Per-class queuing mechanisms . . . . . . . . . . . . 9 4.2.2. Aggregate queuing mechanisms . . . . . . . . . . . . 9
4.3. Ingress considerations . . . . . . . . . . . . . . . . . 10 4.3. Ingress considerations . . . . . . . . . . . . . . . . . 10
4.4. Interspersed non-DetNet transit nodes . . . . . . . . . . 11 4.4. Interspersed DetNet-unaware transit nodes . . . . . . . . 11
5. Achieving zero congestion loss . . . . . . . . . . . . . . . 11 5. Achieving zero congestion loss . . . . . . . . . . . . . . . 11
6. Queuing techniques . . . . . . . . . . . . . . . . . . . . . 12 6. Queuing techniques . . . . . . . . . . . . . . . . . . . . . 12
6.1. Queuing data model . . . . . . . . . . . . . . . . . . . 12 6.1. Queuing data model . . . . . . . . . . . . . . . . . . . 13
6.2. Preemption . . . . . . . . . . . . . . . . . . . . . . . 14 6.2. Frame Preemption . . . . . . . . . . . . . . . . . . . . 15
6.3. Time Aware Shaper . . . . . . . . . . . . . . . . . . . . 15 6.3. Time Aware Shaper . . . . . . . . . . . . . . . . . . . . 15
6.4. Credit-Based Shaper with Asynchronous Traffic Shaping . . 15 6.4. Credit-Based Shaper with Asynchronous Traffic Shaping . . 16
6.4.1. Delay Bound Calculation . . . . . . . . . . . . . . . 17 6.4.1. Delay Bound Calculation . . . . . . . . . . . . . . . 18
6.4.2. Flow Admission . . . . . . . . . . . . . . . . . . . 18 6.4.2. Flow Admission . . . . . . . . . . . . . . . . . . . 19
6.5. IntServ . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.5. IntServ . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.6. Cyclic Queuing and Forwarding . . . . . . . . . . . . . . 20 6.6. Cyclic Queuing and Forwarding . . . . . . . . . . . . . . 21
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 7. Example application on DetNet IP network . . . . . . . . . . 22
7.1. Normative References . . . . . . . . . . . . . . . . . . 21 8. Security considerations . . . . . . . . . . . . . . . . . . . 24
7.2. Informative References . . . . . . . . . . . . . . . . . 22 9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.1. Normative References . . . . . . . . . . . . . . . . . . 24
10.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
The ability for IETF Deterministic Networking (DetNet) or IEEE 802.1 The ability for IETF Deterministic Networking (DetNet) or IEEE 802.1
Time-Sensitive Networking (TSN, [IEEE8021TSN]) to provide the DetNet Time-Sensitive Networking (TSN, [IEEE8021TSN]) to provide the DetNet
services of bounded latency and zero congestion loss depends upon A) services of bounded latency and zero congestion loss depends upon A)
configuring and allocating network resources for the exclusive use of configuring and allocating network resources for the exclusive use of
DetNet/TSN flows; B) identifying, in the data plane, the resources to DetNet flows; B) identifying, in the data plane, the resources to be
be utilized by any given packet, and C) the detailed behavior of utilized by any given packet, and C) the detailed behavior of those
those resources, especially transmission queue selection, so that resources, especially transmission queue selection, so that latency
latency bounds can be reliably assured. Thus, DetNet is an example bounds can be reliably assured.
of an IntServ Guaranteed Quality of Service [RFC2212]
As explained in [RFC8655], DetNet flows are characterized by 1) a As explained in [RFC8655], DetNet flows are characterized by 1) a
maximum bandwidth, guaranteed either by the transmitter or by strict maximum bandwidth, guaranteed either by the transmitter or by strict
input metering; and 2) a requirement for a guaranteed worst-case end- input metering; and 2) a requirement for a guaranteed worst-case end-
to-end latency. That latency guarantee, in turn, provides the to-end latency. That latency guarantee, in turn, provides the
opportunity for the network to supply enough buffer space to opportunity for the network to supply enough buffer space to
guarantee zero congestion loss. guarantee zero congestion loss.
To be of use to the applications identified in [RFC8578], it must be To be used by the applications identified in [RFC8578], it must be
possible to calculate, before the transmission of a DetNet flow possible to calculate, before the transmission of a DetNet flow
commences, both the worst-case end-to-end network latency, and the commences, both the worst-case end-to-end network latency, and the
amount of buffer space required at each hop to ensure against amount of buffer space required at each hop to ensure against
congestion loss. congestion loss.
This document references specific queuing mechanisms, defined in This document references specific queuing mechanisms, defined in
other documents, that can be used to control packet transmission at [RFC8655], that can be used to control packet transmission at each
each output port and achieve the DetNet qualities of service. This output port and achieve the DetNet qualities of service. This
document presents a timing model for sources, destinations, and the document presents a timing model for sources, destinations, and the
DetNet transit nodes that relay packets that is applicable to all of DetNet transit nodes that relay packets that is applicable to all of
those referenced queuing mechanisms. those referenced queuing mechanisms. It furthermore provides end-to-
end delay bound and backlog bound computations for such mechanisms
that can be used by the control plane to provide DetNet QoS.
Using the model presented in this document, it should be possible for Using the model presented in this document, it should be possible for
an implementor, user, or standards development organization to select an implementor, user, or standards development organization to select
a particular set of queuing mechanisms for each device in a DetNet a particular set of queuing mechanisms for each device in a DetNet
network, and to select a resource reservation algorithm for that network, and to select a resource reservation algorithm for that
network, so that those elements can work together to provide the network, so that those elements can work together to provide the
DetNet service. DetNet service. Section 7 provides an example application of this
document to a DetNet IP network with combination of different queuing
mechanisms.
This document does not specify any resource reservation protocol or This document does not specify any resource reservation protocol or
server. It does not describe all of the requirements for that control plane function. It does not describe all of the requirements
protocol or server. It does describe requirements for such resource for that protocol or control plane function. It does describe
reservation methods, and for queuing mechanisms that, if met, will requirements for such resource reservation methods, and for queuing
enable them to work together. mechanisms that, if met, will enable them to work together.
2. Terminology and Definitions 2. Terminology and Definitions
This document uses the terms defined in [RFC8655]. This document uses the terms defined in [RFC8655].
3. DetNet bounded latency model 3. DetNet bounded latency model
3.1. Flow creation
This document assumes that following paradigm is used for 3.1. Flow admission
provisioning DetNet flows:
This document assumes that following paradigm is used to admit DetNet
flows:
1. Perform any configuration required by the DetNet transit nodes in 1. Perform any configuration required by the DetNet transit nodes in
the network for the classes of service to be offered, including the network for aggregates of DetNet flows. This configuration
one or more classes of DetNet service. This configuration is is done beforehand, and not tied to any particular DetNet flow.
done beforehand, and not tied to any particular flow.
2. Characterize the new DetNet flow, particularly in terms of 2. Characterize the new DetNet flow, particularly in terms of
required bandwidth. required bandwidth.
3. Establish the path that the DetNet flow will take through the 3. Establish the path that the DetNet flow will take through the
network from the source to the destination(s). This can be a network from the source to the destination(s). This can be a
point-to-point or a point-to-multipoint path. point-to-point or a point-to-multipoint path.
4. Select one of the DetNet classes of service for the DetNet flow. 4. Compute the worst-case end-to-end latency for the DetNet flow,
5. Compute the worst-case end-to-end latency for the DetNet flow,
using one of the methods, below (Section 3.1.1, Section 3.1.2). using one of the methods, below (Section 3.1.1, Section 3.1.2).
In the process, determine whether sufficient resources are In the process, determine whether sufficient resources are
available for that flow to guarantee the required latency and to available for the DetNet flow to guarantee the required latency
provide zero congestion loss. and to provide zero congestion loss.
6. Assuming that the resources are available, commit those resources 5. Assuming that the resources are available, commit those resources
to the flow. This may or may not require adjusting the to the DetNet flow. This may or may not require adjusting the
parameters that control the filtering and/or queuing mechanisms parameters that control the filtering and/or queuing mechanisms
at each hop along the flow's path. at each hop along the DetNet flow's path.
This paradigm can be implemented using peer-to-peer protocols or This paradigm can be implemented using peer-to-peer protocols or
using a central server. In some situations, a lack of resources can using a central controller. In some situations, a lack of resources
require backtracking and recursing through this list. can require backtracking and recursing through this list.
Issues such as un-provisioning a DetNet flow in favor of another, Issues such as service preemption of a DetNet flow in favor of
when resources are scarce, are not considered, here. Also not another, when resources are scarce, are not considered, here. Also
addressed is the question of how to choose the path to be taken by a not addressed is the question of how to choose the path to be taken
DetNet flow. by a DetNet flow.
3.1.1. Static flow latency calculation 3.1.1. Static latency calculation
The static problem: The static problem:
Given a network and a set of DetNet flows, compute an end-to- Given a network and a set of DetNet flows, compute an end-to-
end latency bound (if computable) for each flow, and compute end latency bound (if computable) for each DetNet flow, and
the resources, particularly buffer space, required in each compute the resources, particularly buffer space, required in
DetNet transit node to achieve zero congestion loss. each DetNet transit node to achieve zero congestion loss.
In this calculation, all of the DetNet flows are known before the In this calculation, all of the DetNet flows are known before the
calculation commences. This problem is of interest to relatively calculation commences. This problem is of interest to relatively
static networks, or static parts of larger networks. It provides static networks, or static parts of larger networks. It provides
bounds on delay and buffer size. The calculations can be extended to bounds on delay and buffer size. The calculations can be extended to
provide global optimizations, such as altering the path of one DetNet provide global optimizations, such as altering the path of one DetNet
flow in order to make resources available to another DetNet flow with flow in order to make resources available to another DetNet flow with
tighter constraints. tighter constraints.
The static flow calculation is not limited only to static networks; The static latency calculation is not limited only to static
the entire calculation for all flows can be repeated each time a new networks; the entire calculation for all DetNet flows can be repeated
DetNet flow is created or deleted. If some already-established flow each time a new DetNet flow is created or deleted. If some already-
would be pushed beyond its latency requirements by the new flow, then established DetNet flow would be pushed beyond its latency
the new flow can be refused, or some other suitable action taken. requirements by the new DetNet flow, then the new DetNet flow can be
refused, or some other suitable action taken.
This calculation may be more difficult to perform than that of the This calculation may be more difficult to perform than that of the
dynamic calculation (Section 3.1.2), because the flows passing dynamic calculation (Section 3.1.2), because the DetNet flows passing
through one port on a DetNet transit node affect each others' through one port on a DetNet transit node affect each others'
latency. The effects can even be circular, from Flow A to B to C and latency. The effects can even be circular, from a node A to B to C
back to A. On the other hand, the static calculation can often and back to A. On the other hand, the static calculation can often
accommodate queuing methods, such as transmission selection by strict accommodate queuing methods, such as transmission selection by strict
priority, that are unsuitable for the dynamic calculation. priority, that are unsuitable for the dynamic calculation.
3.1.2. Dynamic flow latency calculation 3.1.2. Dynamic latency calculation
The dynamic problem: The dynamic problem:
Given a network whose maximum capacity for DetNet flows is Given a network whose maximum capacity for DetNet flows is
bounded by a set of static configuration parameters applied bounded by a set of static configuration parameters applied
to the DetNet transit nodes, and given just one DetNet flow, to the DetNet transit nodes, and given just one DetNet flow,
compute the worst-case end-to-end latency that can be compute the worst-case end-to-end latency that can be
experienced by that flow, no matter what other DetNet flows experienced by that flow, no matter what other DetNet flows
(within the network's configured parameters) might be created (within the network's configured parameters) might be created
or deleted in the future. Also, compute the resources, or deleted in the future. Also, compute the resources,
particularly buffer space, required in each DetNet transit particularly buffer space, required in each DetNet transit
node to achieve zero congestion loss. node to achieve zero congestion loss.
This calculation is dynamic, in the sense that flows can be added or This calculation is dynamic, in the sense that DetNet flows can be
deleted at any time, with a minimum of computation effort, and added or deleted at any time, with a minimum of computation effort,
without affecting the guarantees already given to other flows. and without affecting the guarantees already given to other DetNet
flows.
The choice of queuing methods is critical to the applicability of the The choice of queuing methods is critical to the applicability of the
dynamic calculation. Some queuing methods (e.g. CQF, Section 6.6) dynamic calculation. Some queuing methods (e.g. CQF, Section 6.6)
make it easy to configure bounds on the network's capacity, and to make it easy to configure bounds on the network's capacity, and to
make independent calculations for each flow. Some other queuing make independent calculations for each DetNet flow. Some other
methods (e.g. strict priority with the credit-based shaper defined in queuing methods (e.g. strict priority with the credit-based shaper
[IEEE8021Q] section 8.6.8.2) can be used for dynamic flow creation, defined in [IEEE8021Q] section 8.6.8.2) can be used for dynamic
but yield poorer latency and buffer space guarantees than when that DetNet flow creation, but yield poorer latency and buffer space
same queuing method is used for static flow creation (Section 3.1.1). guarantees than when that same queuing method is used for static
DetNet flow creation (Section 3.1.1).
3.2. Relay node model 3.2. Relay node model
A model for the operation of a DetNet transit node is required, in A model for the operation of a DetNet transit node is required, in
order to define the latency and buffer calculations. In Figure 1 we order to define the latency and buffer calculations. In Figure 1 we
see a breakdown of the per-hop latency experienced by a packet see a breakdown of the per-hop latency experienced by a packet
passing through a DetNet transit node, in terms that are suitable for passing through a DetNet transit node, in terms that are suitable for
computing both hop-by-hop latency and per-hop buffer requirements. computing both hop-by-hop latency and per-hop buffer requirements.
DetNet transit node A DetNet transit node B DetNet transit node A DetNet transit node B
+-------------------------+ +------------------------+ +-------------------------+ +------------------------+
| Queuing | | Queuing | | Queuing | | Queuing |
| Regulator subsystem | | Regulator subsystem | | Regulator subsystem | | Regulator subsystem |
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
-->+ | | | | | | | | | + +------>+ | | | | | | | | | + +---> -->+ | | | | | | | | | + +------>+ | | | | | | | | | + +--->
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
| | | | | | | |
+-------------------------+ +------------------------+ +-------------------------+ +------------------------+
|<->|<------>|<------->|<->|<---->|<->|<------>|<------>|<->|<-- |<->|<------>|<------->|<->|<---->|<->|<------>|<------>|<->|<--
2,3 4 5 6 1 2,3 4 5 6 1 2,3 2,3 4 5 6 1 2,3 4 5 6 1 2,3
1: Output delay 4: Processing delay 1: Output delay 4: Processing delay
2: Link delay 5: Regulation delay 2: Link delay 5: Regulation delay
3: Preemption delay 6: Queuing delay. 3: Frame preemption delay 6: Queuing delay
Figure 1: Timing model for DetNet or TSN Figure 1: Timing model for DetNet or TSN
In Figure 1, we see two DetNet transit nodes (typically, bridges or In Figure 1, we see two DetNet transit nodes that are connected via a
routers), with a wired link between them. In this model, the only link. In this model, the only queues, that we deal with explicitly,
queues, that we deal with explicitly, are attached to the output are attached to the output port; other queues are modeled as
port; other queues are modeled as variations in the other delay variations in the other delay times. (E.g., an input queue could be
times. (E.g., an input queue could be modeled as either a variation modeled as either a variation in the link delay (2) or the processing
in the link delay [2] or the processing delay [4].) There are six delay (4).) There are six delays that a packet can experience from
delays that a packet can experience from hop to hop. hop to hop.
1. Output delay 1. Output delay
The time taken from the selection of a packet for output from a The time taken from the selection of a packet for output from a
queue to the transmission of the first bit of the packet on the queue to the transmission of the first bit of the packet on the
physical link. If the queue is directly attached to the physical physical link. If the queue is directly attached to the physical
port, output delay can be a constant. But, in many port, output delay can be a constant. But, in many
implementations, the queuing mechanism in a forwarding ASIC is implementations, the queuing mechanism in a forwarding ASIC is
separated from a multi-port MAC/PHY, in a second ASIC, by a separated from a multi-port MAC/PHY, in a second ASIC, by a
multiplexed connection. This causes variations in the output multiplexed connection. This causes variations in the output
delay that are hard for the forwarding node to predict or control. delay that are hard for the forwarding node to predict or control.
2. Link delay 2. Link delay
The time taken from the transmission of the first bit of the The time taken from the transmission of the first bit of the
packet to the reception of the last bit, assuming that the packet to the reception of the last bit, assuming that the
transmission is not suspended by a preemption event. This delay transmission is not suspended by a frame preemption event. This
has two components, the first-bit-out to first-bit-in delay and delay has two components, the first-bit-out to first-bit-in delay
the first-bit-in to last-bit-in delay that varies with packet and the first-bit-in to last-bit-in delay that varies with packet
size. The former is typically measured by the Precision Time size. The former is typically measured by the Precision Time
Protocol and is constant (see [RFC8655]). However, a virtual Protocol and is constant (see [RFC8655]). However, a virtual
"link" could exhibit a variable link delay. "link" could exhibit a variable link delay.
3. Preemption delay 3. Frame preemption delay
If the packet is interrupted in order to transmit another packet If the packet is interrupted in order to transmit another packet
or packets, (e.g. [IEEE8023] clause 99 frame preemption) an or packets, (e.g. [IEEE8023] clause 99 frame preemption) an
arbitrary delay can result. arbitrary delay can result.
4. Processing delay 4. Processing delay
This delay covers the time from the reception of the last bit of This delay covers the time from the reception of the last bit of
the packet to the time the packet is enqueued in the regulator the packet to the time the packet is enqueued in the regulator
(Queuing subsystem, if there is no regulation). This delay can be (Queuing subsystem, if there is no regulation). This delay can be
variable, and depends on the details of the operation of the variable, and depends on the details of the operation of the
forwarding node. forwarding node.
skipping to change at page 8, line 41 skipping to change at page 8, line 46
First, at the h-th hop along the path of this DetNet flow, obtain an First, at the h-th hop along the path of this DetNet flow, obtain an
upperbound per-hop_non_queuing_delay_bound[h] on the sum of the upperbound per-hop_non_queuing_delay_bound[h] on the sum of the
bounds over the delays 1,2,3,4 of Figure 1. These upper bounds are bounds over the delays 1,2,3,4 of Figure 1. These upper bounds are
expected to depend on the specific technology of the DetNet transit expected to depend on the specific technology of the DetNet transit
node at the h-th hop but not on the T-SPEC of this DetNet flow. Then node at the h-th hop but not on the T-SPEC of this DetNet flow. Then
set non_queuing_delay_bound = the sum of per- set non_queuing_delay_bound = the sum of per-
hop_non_queuing_delay_bound[h] over all hops h. hop_non_queuing_delay_bound[h] over all hops h.
Second, compute queuing_delay_bound as an upper bound to the sum of Second, compute queuing_delay_bound as an upper bound to the sum of
the queuing delays along the path. The value of queuing_delay_bound the queuing delays along the path. The value of queuing_delay_bound
depends on the T-SPEC of this flow and possibly of other flows in the depends on the T-SPEC of this DetNet flow and possibly of other flows
network, as well as the specifics of the queuing mechanisms deployed in the network, as well as the specifics of the queuing mechanisms
along the path of this flow. The computation of queuing_delay_bound deployed along the path of this DetNet flow. The computation of
is described in Section 4.2 as a separate section. queuing_delay_bound is described in Section 4.2 as a separate
section.
4.2. Queuing delay bound 4.2. Queuing delay bound
For several queuing mechanisms, queuing_delay_bound is less than the For several queuing mechanisms, queuing_delay_bound is less than the
sum of upper bounds on the queuing delays (5,6) at every hop. This sum of upper bounds on the queuing delays (5,6) at every hop. This
occurs with (1) per-flow queuing, and (2) per-class queuing with occurs with (1) per-flow queuing, and (2) aggregate queuing with
regulators, as explained in Section 4.2.1, Section 4.2.2, and regulators, as explained in Section 4.2.1, Section 4.2.2, and
Section 6. Section 6.
For other queuing mechanisms the only available value of For other queuing mechanisms the only available value of
queuing_delay_bound is the sum of the per-hop queuing delay bounds. queuing_delay_bound is the sum of the per-hop queuing delay bounds.
In such cases, the computation of per-hop queuing delay bounds must In such cases, the computation of per-hop queuing delay bounds must
account for the fact that the T-SPEC of a DetNet flow is no longer account for the fact that the T-SPEC of a DetNet flow is no longer
satisfied at the ingress of a hop, since burstiness increases as one satisfied at the ingress of a hop, since burstiness increases as one
flow traverses one DetNet transit node. flow traverses one DetNet transit node.
4.2.1. Per-flow queuing mechanisms 4.2.1. Per-flow queuing mechanisms
With such mechanisms, each flow uses a separate queue inside every With such mechanisms, each flow uses a separate queue inside every
node. The service for each queue is abstracted with a guaranteed node. The service for each queue is abstracted with a guaranteed
rate and a latency. For every flow, a per-node delay bound as well rate and a latency. For every DetNet flow, a per-node delay bound as
as an end-to-end delay bound can be computed from the traffic well as an end-to-end delay bound can be computed from the traffic
specification of this flow at its source and from the values of rates specification of this DetNet flow at its source and from the values
and latencies at all nodes along its path. The per-flow queuing is of rates and latencies at all nodes along its path. The per-flow
used in IntServ. Details of calculation for IntServ are described in queuing is used in IntServ. Details of calculation for IntServ are
Section 6.5. described in Section 6.5.
4.2.2. Per-class queuing mechanisms 4.2.2. Aggregate queuing mechanisms
With such mechanisms, the flows that have the same class share the With such mechanisms, multiple flows are aggregated into macro-flows
same queue. A practical example is the credit-based shaper defined and there is one FIFO queue per macro-flow. A practical example is
in section 8.6.8.2 of [IEEE8021Q]. One key issue in this context is the credit-based shaper defined in section 8.6.8.2 of [IEEE8021Q]
how to deal with the burstiness cascade: individual flows that share where a macro-flow is called a "class". One key issue in this
a resource dedicated to a class may see their burstiness increase, context is how to deal with the burstiness cascade: individual flows
which may in turn cause increased burstiness to other flows that share a resource dedicated to a macro-flow may see their
downstream of this resource. Computing delay upper bounds for such burstiness increase, which may in turn cause increased burstiness to
cases is difficult, and in some conditions impossible other flows downstream of this resource. Computing delay upper
bounds for such cases is difficult, and in some conditions impossible
[charny2000delay][bennett2002delay]. Also, when bounds are obtained, [charny2000delay][bennett2002delay]. Also, when bounds are obtained,
they depend on the complete configuration, and must be recomputed they depend on the complete configuration, and must be recomputed
when one flow is added. (The dynamic calculation, Section 3.1.2.) when one flow is added. (The dynamic calculation, Section 3.1.2.)
A solution to deal with this issue is to reshape the flows at every A solution to deal with this issue for the DetNet flows is to reshape
hop. This can be done with per-flow regulators (e.g. leaky bucket them at every hop. This can be done with per-flow regulators (e.g.
shapers), but this requires per-flow queuing and defeats the purpose leaky bucket shapers), but this requires per-flow queuing and defeats
of per-class queuing. An alternative is the interleaved regulator, the purpose of aggregate queuing. An alternative is the interleaved
which reshapes individual flows without per-flow queuing regulator, which reshapes individual DetNet flows without per-flow
([Specht2016UBS], [IEEE8021Qcr]). With an interleaved regulator, the queuing ([Specht2016UBS], [IEEE8021Qcr]). With an interleaved
packet at the head of the queue is regulated based on its (flow) regulator, the packet at the head of the queue is regulated based on
regulation constraints; it is released at the earliest time at which its (flow) regulation constraints; it is released at the earliest
this is possible without violating the constraint. One key feature time at which this is possible without violating the constraint. One
of per-flow or interleaved regulator is that, it does not increase key feature of per-flow or interleaved regulator is that, it does not
worst-case latency bounds [le_boudec_theory_2018]. Specifically, increase worst-case latency bounds [le_boudec2018theory].
when an interleaved regulator is appended to a FIFO subsystem, it Specifically, when an interleaved regulator is appended to a FIFO
does not increase the worst-case delay of the latter. subsystem, it does not increase the worst-case delay of the latter.
Figure 2 shows an example of a network with 5 nodes, per-class Figure 2 shows an example of a network with 5 nodes, aggregate
queuing mechanism and interleaved regulators as in Figure 1. An end- queuing mechanism and interleaved regulators as in Figure 1. An end-
to-end delay bound for flow f, traversing nodes 1 to 5, is calculated to-end delay bound for DetNet flow f, traversing nodes 1 to 5, is
as follows: calculated as follows:
end_to_end_latency_bound_of_flow_f = C12 + C23 + C34 + S4 end_to_end_latency_bound_of_flow_f = C12 + C23 + C34 + S4
In the above formula, Cij is a bound on the delay of the queuing In the above formula, Cij is a bound on the delay of the queuing
subsystem in node i and interleaved regulator of node j, and S4 is a subsystem in node i and interleaved regulator of node j, and S4 is a
bound on the delay of the queuing subsystem in node 4 for flow f. In bound on the delay of the queuing subsystem in node 4 for DetNet flow
fact, using the delay definitions in Section 3.2, Cij is a bound on f. In fact, using the delay definitions in Section 3.2, Cij is a
sum of the delays 1,2,3,6 of node i and 4,5 of node j. Similarly, S4 bound on sum of the delays 1,2,3,6 of node i and 4,5 of node j.
is a bound on sum of the delays 1,2,3,6 of node 4. A practical Similarly, S4 is a bound on sum of the delays 1,2,3,6 of node 4. A
example of queuing model and delay calculation is presented practical example of queuing model and delay calculation is presented
Section 6.4. Section 6.4.
f f
-----------------------------> ----------------------------->
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| 1 |---| 2 |---| 3 |---| 4 |---| 5 | | 1 |---| 2 |---| 3 |---| 4 |---| 5 |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
\__C12_/\__C23_/\__C34_/\_S4_/ \__C12_/\__C23_/\__C34_/\_S4_/
Figure 2: End-to-end delay computation example Figure 2: End-to-end delay computation example
REMARK: The end-to-end delay bound calculation provided here gives a REMARK: The end-to-end delay bound calculation provided here gives a
much better upper bound in comparison with end-to-end delay bound much better upper bound in comparison with end-to-end delay bound
computation by adding the delay bounds of each node in the path of a computation by adding the delay bounds of each node in the path of a
flow [TSNwithATS]. DetNet flow [TSNwithATS].
4.3. Ingress considerations 4.3. Ingress considerations
A sender can be a DetNet node which uses exactly the same queuing A sender can be a DetNet node which uses exactly the same queuing
methods as its adjacent DetNet transit node, so that the delay and methods as its adjacent DetNet transit node, so that the delay and
buffer bounds calculations at the first hop are indistinguishable buffer bounds calculations at the first hop are indistinguishable
from those at a later hop within the DetNet domain. On the other from those at a later hop within the DetNet domain. On the other
hand, the sender may be DetNet unaware, in which case some hand, the sender may be DetNet-unaware, in which case some
conditioning of the flow may be necessary at the ingress DetNet conditioning of the DetNet flow may be necessary at the ingress
transit node. DetNet transit node.
This ingress conditioning typically consists of a FIFO with an output This ingress conditioning typically consists of a FIFO with an output
regulator that is compatible with the queuing employed by the DetNet regulator that is compatible with the queuing employed by the DetNet
transit node on its output port(s). For some queuing methods, simply transit node on its output port(s). For some queuing methods, simply
requires added extra buffer space in the queuing subsystem. Ingress requires added extra buffer space in the queuing subsystem. Ingress
conditioning requirements for different queuing methods are mentioned conditioning requirements for different queuing methods are mentioned
in the sections, below, describing those queuing methods. in the sections, below, describing those queuing methods.
4.4. Interspersed non-DetNet transit nodes 4.4. Interspersed DetNet-unaware transit nodes
It is sometimes desirable to build a network that has both DetNet It is sometimes desirable to build a network that has both DetNet-
aware transit nodes and DetNet non-aware transit nodes, and for a aware transit nodes and DetNet-uaware transit nodes, and for a DetNet
DetNet flow to traverse an island of non-DetNet transit nodes, while flow to traverse an island of DetNet-unaware transit nodes, while
still allowing the network to offer delay and congestion loss still allowing the network to offer delay and congestion loss
guarantees. This is possible under certain conditions. guarantees. This is possible under certain conditions.
In general, when passing through a non-DetNet island, the island In general, when passing through a DetNet-unaware island, the island
causes delay variation in excess of what would be caused by DetNet may cause delay variation in excess of what would be caused by DetNet
nodes. That is, the DetNet flow is "lumpier" after traversing the nodes. That is, the DetNet flow might be "lumpier" after traversing
non-DetNet island. DetNet guarantees for delay and buffer the DetNet-unaware island. DetNet guarantees for delay and buffer
requirements can still be calculated and met if and only if the requirements can still be calculated and met if and only if the
following are true: following are true:
1. The latency variation across the non-DetNet island must be 1. The latency variation across the DetNet-unaware island must be
bounded and calculable. bounded and calculable.
2. An ingress conditioning function (Section 4.3) may be required at 2. An ingress conditioning function (Section 4.3) is required at the
the re-entry to the DetNet-aware domain. This will, at least, re-entry to the DetNet-aware domain. This will, at least,
require some extra buffering to accommodate the additional delay require some extra buffering to accommodate the additional delay
variation, and thus further increases the delay bound. variation, and thus further increases the delay bound.
The ingress conditioning is exactly the same problem as that of a The ingress conditioning is exactly the same problem as that of a
sender at the edge of the DetNet domain. The requirement for bounds sender at the edge of the DetNet domain. The requirement for bounds
on the latency variation across the non-DetNet island is typically on the latency variation across the DetNet-unaware island is
the most difficult to achieve. Without such a bound, it is obvious typically the most difficult to achieve. Without such a bound, it is
that DetNet cannot deliver its guarantees, so a non-DetNet island obvious that DetNet cannot deliver its guarantees, so a DetNet-
that cannot offer bounded latency variation cannot be used to carry a unaware island that cannot offer bounded latency variation cannot be
DetNet flow. used to carry a DetNet flow.
5. Achieving zero congestion loss 5. Achieving zero congestion loss
When the input rate to an output queue exceeds the output rate for a When the input rate to an output queue exceeds the output rate for a
sufficient length of time, the queue must overflow. This is sufficient length of time, the queue must overflow. This is
congestion loss, and this is what deterministic networking seeks to congestion loss, and this is what deterministic networking seeks to
avoid. avoid.
To avoid congestion losses, an upper bound on the backlog present in To avoid congestion losses, an upper bound on the backlog present in
the regulator and queuing subsystem of Figure 1 must be computed the regulator and queuing subsystem of Figure 1 must be computed
during resource reservation. This bound depends on the set of flows during resource reservation. This bound depends on the set of flows
that use these queues, the details of the specific queuing mechanism that use these queues, the details of the specific queuing mechanism
and an upper bound on the processing delay (4). The queue must and an upper bound on the processing delay (4). The queue must
contain the packet in transmission plus all other packets that are contain the packet in transmission plus all other packets that are
waiting to be selected for output. waiting to be selected for output.
A conservative backlog bound, that applies to all systems, can be A conservative backlog bound, that applies to all systems, can be
derived as follows. derived as follows.
The backlog bound is counted in data units (bytes, or words of The backlog bound is counted in data units (bytes, or words of
multiple bytes) that are relevant for buffer allocation. For every multiple bytes) that are relevant for buffer allocation. Based on
class we need one buffer space for the packet in transmission, plus the que For every flow or an aggregate of flows, we need one buffer
space for the packets that are waiting to be selected for output. space for the packet in transmission, plus space for the packets that
Excluding transmission and preemption times, the packets are waiting are waiting to be selected for output. Excluding transmission and
in the queue since reception of the last bit, for a duration equal to frame preemption times, the packets are waiting in the queue since
the processing delay (4) plus the queuing delays (5,6). reception of the last bit, for a duration equal to the processing
delay (4) plus the queuing delays (5,6).
Let Let
o total_in_rate be the sum of the line rates of all input ports that o total_in_rate be the sum of the line rates of all input ports that
send traffic of any class to this output port. The value of send traffic to this output port. The value of total_in_rate is
total_in_rate is in data units (e.g. bytes) per second. in data units (e.g. bytes) per second.
o nb_input_ports be the number input ports that send traffic of any o nb_input_ports be the number input ports that send traffic to this
class to this output port output port
o max_packet_length be the maximum packet size for packets of any o max_packet_length be the maximum packet size for packets that may
class that may be sent to this output port. This is counted in be sent to this output port. This is counted in data units.
data units.
o max_delay456 be an upper bound, in seconds, on the sum of the o max_delay456 be an upper bound, in seconds, on the sum of the
processing delay (4) and the queuing delays (5,6) for a packet of processing delay (4) and the queuing delays (5,6) for any packet
any class at this output port. at this output port.
Then a bound on the backlog of traffic of all classes in the queue at Then a bound on the backlog of traffic in the queue at this output
this output port is port is
backlog_bound = nb_input_ports * max_packet_length + backlog_bound = nb_input_ports * max_packet_length +
total_in_rate* max_delay456 total_in_rate* max_delay456
6. Queuing techniques 6. Queuing techniques
In this section, for simplicity of delay computation, we assume that In this section, for simplicity of delay computation, we assume that
the T-SPEC or arrival curve [NetCalBook] for each flow at source is the T-SPEC or arrival curve [NetCalBook] for each DetNet flow at
leaky bucket. Also, at each relay node, the service for each queue source is leaky bucket. Also, at each Detnet transit node, the
is abstracted with a guaranteed rate and a latency. service for each queue is abstracted with a guaranteed rate and a
latency.
6.1. Queuing data model 6.1. Queuing data model
Sophisticated queuing mechanisms are available in Layer 3 (L3, see, Sophisticated queuing mechanisms are available in Layer 3 (L3, see,
e.g., [RFC7806] for an overview). In general, we assume that "Layer e.g., [RFC7806] for an overview). In general, we assume that "Layer
3" queues, shapers, meters, etc., are precisely the "regulators" 3" queues, shapers, meters, etc., are precisely the "regulators"
shown in Figure 1. The "queuing subsystems" in this figure are not shown in Figure 1. The "queuing subsystems" in this figure are not
the province solely of bridges; they are an essential part of any the province solely of bridges; they are an essential part of any
DetNet transit node. As illustrated by numerous implementation DetNet transit node. As illustrated by numerous implementation
examples, some of the "Layer 3" mechanisms described in documents examples, some of the "Layer 3" mechanisms described in documents
such as [RFC7806] are often integrated, in an implementation, with such as [RFC7806] are often integrated, in an implementation, with
the "Layer 2" mechanisms also implemented in the same node. An the "Layer 2" mechanisms also implemented in the same node. An
integrated model is needed in order to successfully predict the integrated model is needed in order to successfully predict the
interactions among the different queuing mechanisms needed in a interactions among the different queuing mechanisms needed in a
network carrying both DetNet flows and non-DetNet flows. network carrying both DetNet flows and non-DetNet flows.
Figure 3 shows the general model for the flow of packets through the Figure 3 shows the general model for the flow of packets through the
queues of a DetNet transit node. Packets are assigned to a class of queues of a DetNet transit node. The DetNet packets are mapped to a
service. The classes of service are mapped to some number of number of regulators. Here, we assume that the PREOF (Packet
regulator queues. Only DetNet/TSN packets pass through regulators. Replication, Elimination and Ordering Functions) functions are
Queues compete for the selection of packets to be passed to queues in performed before the DetNet packets enter the regulators. All
the queuing subsystem. Packets again are selected for output from Packets are assigned to a set of queues. Queues compete for the
the queuing subsystem. selection of packets to be passed to queues in the queuing subsystem.
Packets again are selected for output from the queuing subsystem.
| |
+--------------------------------V----------------------------------+ +--------------------------------V----------------------------------+
| Class of Service Assignment | | Queue assignment |
+--+------+----------+---------+-----------+-----+-------+-------+--+ +--+------+----------+---------+-----------+-----+-------+-------+--+
| | | | | | | | | | | | | | | |
+--V-+ +--V-+ +--V--+ +--V--+ +--V--+ | | | +--V-+ +--V-+ +--V--+ +--V--+ +--V--+ | | |
|Flow| |Flow| |Flow | |Flow | |Flow | | | | |Flow| |Flow| |Flow | |Flow | |Flow | | | |
| 0 | | 1 | ... | i | | i+1 | ... | n | | | | | 0 | | 1 | ... | i | | i+1 | ... | n | | | |
| reg| | reg| | reg | | reg | | reg | | | | | reg| | reg| | reg | | reg | | reg | | | |
+--+-+ +--+-+ +--+--+ +--+--+ +--+--+ | | | +--+-+ +--+-+ +--+--+ +--+--+ +--+--+ | | |
| | | | | | | | | | | | | | | |
+--V------V----------V--+ +--V-----------V--+ | | | +--V------V----------V--+ +--V-----------V--+ | | |
| Trans. selection | | Trans. select. | | | | | Trans. selection | | Trans. select. | | | |
+----------+------------+ +-----+-----------+ | | | +----------+------------+ +-----+-----------+ | | |
| | | | | | | | | |
+--V--+ +--V--+ +--V--+ +--V--+ +--V--+ +--V--+ +--V--+ +--V--+ +--V--+ +--V--+
| out | | out | | out | | out | | out | | out | | out | | out | | out | | out |
|queue| |queue| |queue| |queue| |queue| |queue| |queue| |queue| |queue| |queue|
| 1 | | 2 | | 3 | | 4 | | 5 | | 1 | | 2 | | 3 | | 4 | | 5 |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| | | | | | | | | |
+----------V----------------------V--------------V-------V-------V--+ +----------V----------------------V--------------V-------V-------V--+
| Transmission selection | | Transmission selection |
+----------+----------------------+--------------+-------+-------+--+ +---------------------------------+---------------------------------+
| | | | | |
V V V V V V
DetNet/TSN queue DetNet/TSN queue non-DetNet/TSN queues
Figure 3: IEEE 802.1Q Queuing Model: Data flow Figure 3: IEEE 802.1Q Queuing Model: Data flow
Some relevant mechanisms are hidden in this figure, and are performed Some relevant mechanisms are hidden in this figure, and are performed
in the queue boxes: in the queue boxes:
o Discarding packets because a queue is full. o Discarding packets because a queue is full.
o Discarding packets marked "yellow" by a metering function, in o Discarding packets marked "yellow" by a metering function, in
preference to discarding "green" packets. preference to discarding "green" packets.
Ideally, neither of these actions are performed on DetNet packets. Ideally, neither of these actions are performed on DetNet packets.
Full queues for DetNet packets should occur only when a flow is Full queues for DetNet packets should occur only when a DetNet flow
misbehaving, and the DetNet QoS does not include "yellow" service for is misbehaving, and the DetNet QoS does not include "yellow" service
packets in excess of committed rate. for packets in excess of committed rate.
The Class of Service Assignment function can be quite complex, even The queue assignment function can be quite complex, even in a bridge
in a bridge [IEEE8021Q], since the introduction of per-stream [IEEE8021Q], since the introduction of per-stream filtering and
filtering and policing ([IEEE8021Q] clause 8.6.5.1). In addition to policing ([IEEE8021Q] clause 8.6.5.1). In addition to the Layer 2
the Layer 2 priority expressed in the 802.1Q VLAN tag, a DetNet priority expressed in the 802.1Q VLAN tag, a DetNet transit node can
transit node can utilize any of the following information to assign a utilize any of the following information to assign a packet to a
packet to a particular class of service (queue): particular queue:
o Input port. o Input port.
o Selector based on a rotating schedule that starts at regular, o Selector based on a rotating schedule that starts at regular,
time-synchronized intervals and has nanosecond precision. time-synchronized intervals and has nanosecond precision.
o MAC addresses, VLAN ID, IP addresses, Layer 4 port numbers, DSCP. o MAC addresses, VLAN ID, IP addresses, Layer 4 port numbers, DSCP.
([I-D.ietf-detnet-ip], [I-D.ietf-detnet-mpls]) (Work items are ([RFC8939], [RFC8964]) (Work items are expected to add MPC and
expected to add MPC and other indicators.) other indicators.)
o The Class of Service Assignment function can contain metering and o The queue assignment function can contain metering and policing
policing functions. functions.
o MPLS and/or pseudowire ([RFC6658]) labels. o MPLS and/or pseudowire ([RFC6658]) labels.
The "Transmission selection" function decides which queue is to The "Transmission selection" function decides which queue is to
transfer its oldest packet to the output port when a transmission transfer its oldest packet to the output port when a transmission
opportunity arises. opportunity arises.
6.2. Preemption 6.2. Frame Preemption
In [IEEE8021Q] and [IEEE8023], the transmission of a frame can be In [IEEE8021Q] and [IEEE8023], the transmission of a frame can be
interrupted by one or more "express" frames, and then the interrupted interrupted by one or more "express" frames, and then the interrupted
frame can continue transmission. This frame preemption is modeled as frame can continue transmission. The frame preemption is modeled as
consisting of two MAC/PHY stacks, one for packets that can be consisting of two MAC/PHY stacks, one for packets that can be
interrupted, and one for packets that can interrupt the interruptible interrupted, and one for packets that can interrupt the interruptible
packets. The Class of Service (queue) determines which packets are packets. Only one layer of frame preemption is supported -- a
which. Only one layer of preemption is supported -- a transmitter transmitter cannot have more than one interrupted frame in progress.
cannot have more than one interrupted frame in progress. DetNet DetNet flows typically pass through the interrupting MAC. For those
flows typically pass through the interrupting MAC. For those DetNet DetNet flows with T-SPEC, latency bound can be calculated by the
flows with T-SPEC, latency bound can be calculated by the methods methods provided in the following sections that accounts for the
provided in the following sections that accounts for the affect of affect of frame preemption, according to the specific queuing
preemption, according to the specific queuing mechanism that is used mechanism that is used in DetNet nodes. Best-effort queues pass
in DetNet nodes. Best-effort queues pass through the interruptible through the interruptible MAC, and can thus be preempted.
MAC, and can thus be preempted.
6.3. Time Aware Shaper 6.3. Time Aware Shaper
In [IEEE8021Q], the notion of time-scheduling queue gates is In [IEEE8021Q], the notion of time-scheduling queue gates is
described in section 8.6.8.4. On each node, the transmission described in section 8.6.8.4. On each node, the transmission
selection for packets is controlled by time-synchronized gates; each selection for packets is controlled by time-synchronized gates; each
output queue is associated with a gate. The gates can be either open output queue is associated with a gate. The gates can be either open
or close. The states of the gates are determined by the gate control or close. The states of the gates are determined by the gate control
list (GCL). The GCL specifies the opening and closing times of the list (GCL). The GCL specifies the opening and closing times of the
gates. Since the design of GCL should satisfy the requirement of gates. The design of GCL should satisfy the requirement of latency
latency upper bounds of all time-sensitive flows, those flows travers upper bounds of all DetNet flows; therefore, those DetNet flows
a network should have bounded latency, if the traffic and nodes are traverse a network should have bounded latency, if the traffic and
conformant. nodes are conformant.
It should be noted that scheduled traffic service relies on a It should be noted that scheduled traffic service relies on a
synchronized network and coordinated GCL configuration. Synthesis of synchronized network and coordinated GCL configuration. Synthesis of
GCL on multiple nodes in network is a scheduling problem considering GCL on multiple nodes in network is a scheduling problem considering
all TSN/DetNet flows traversing the network, which is a non- all DetNet flows traversing the network, which is a non-deterministic
deterministic polynomial-time hard (NP-hard) problem. Also, at this polynomial-time hard (NP-hard) problem. Also, at this writing,
writing, scheduled traffic service supports no more than eight scheduled traffic service supports no more than eight traffic queues,
traffic classes, typically using up to seven priority classes and at typically using up to seven priority queues and at least one best
least one best effort class. effort.
6.4. Credit-Based Shaper with Asynchronous Traffic Shaping 6.4. Credit-Based Shaper with Asynchronous Traffic Shaping
In the cosidered queuing model, there are four types of flows, In the considered queuing model, we considered the four traffic
namely, control-data traffic (CDT), class A, class B, and best effort classes (Definition 3.268 of [IEEE8021Q]): control-data traffic
(BE) in decreasing order of priority. Flows of classes A and B are (CDT), class A, class B, and best effort (BE) in decreasing order of
together referred to AVB flows. This model is a subset of Time- priority. Flows of classes A and B are together referred as AVB
Sensitive Networking as described next. flows. This model is a subset of Time-Sensitive Networking as
described next.
Based on the timing model described in Figure 1, the contention Based on the timing model described in Figure 1, the contention
occurs only at the output port of a relay node; therefore, the focus occurs only at the output port of a DetNet transit node; therefore,
of the rest of this subsection is on the regulator and queuing the focus of the rest of this subsection is on the regulator and
subsystem in the output port of a relay node. The output port queuing subsystem in the output port of a DetNet transit node. Then,
performs per-class scheduling with eight classes (queuing the input flows are identified using the information in (Section 5.1
subsystems): one for CDT, one for class A traffic, one for class B of [RFC8939]). Then they are aggregated into eight macro flows based
traffic, and five for BE traffic denoted as BE0-BE4. The queuing on their traffic classes. We refer to each macro flow as a class.
policy for each queuing subsystem is FIFO. In addition, each node The output port performs aggregate scheduling with eight queues
output port also performs per-flow regulation for AVB flows using an (queuing subsystems): one for CDT, one for class A flows, one for
interleaved regulator (IR), called Asynchronous Traffic Shaper class B flows, and five for BE traffic denoted as BE0-BE4. The
[IEEE8021Qcr]. Thus, at each output port of a node, there is one queuing policy for each queuing subsystem is FIFO. In addition, each
interleaved regulator per-input port and per-class; the interleaved node output port also performs per-flow regulation for AVB flows
regulator is mapped to the regulator depicted in Figure 1. The using an interleaved regulator (IR), called Asynchronous Traffic
detailed picture of scheduling and regulation architecture at a node Shaper [IEEE8021Qcr]. Thus, at each output port of a node, there is
output port is given by Figure 4. The packets received at a node one interleaved regulator per-input port and per-class; the
input port for a given class are enqueued in the respective interleaved regulator is mapped to the regulator depicted in
interleaved regulator at the output port. Then, the packets from all Figure 1. The detailed picture of scheduling and regulation
the flows, including CDT and BE flows, are enqueued in queuing architecture at a node output port is given by Figure 4. The packets
subsytem; there is no regulator for such classes. received at a node input port for a given class are enqueued in the
respective interleaved regulator at the output port. Then, the
packets from all the flows, including CDT and BE flows, are enqueued
in queuing subsytem; there is no regulator for such classes.
+--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+
| | | | | | | | | | | | | | | |
|IR| |IR| |IR| |IR| |IR| |IR| |IR| |IR|
| | | | | | | | | | | | | | | |
+-++XXX++-+ +-++XXX++-+ +-++XXX++-+ +-++XXX++-+
| | | | | | | |
| | | | | | | |
+---+ +-v-XXX-v-+ +-v-XXX-v-+ +-----+ +-----+ +-----+ +-----+ +-----+ +---+ +-v-XXX-v-+ +-v-XXX-v-+ +-----+ +-----+ +-----+ +-----+ +-----+
| | | | | | |Class| |Class| |Class| |Class| |Class| | | | | | | |Class| |Class| |Class| |Class| |Class|
skipping to change at page 16, line 35 skipping to change at page 17, line 31
| | | | | | | | | | | | | | | |
+-v--------v-----------v---------v-------V-------v-------v-------v--+ +-v--------v-----------v---------v-------V-------v-------v-------v--+
| Strict Priority selection | | Strict Priority selection |
+--------------------------------+----------------------------------+ +--------------------------------+----------------------------------+
| |
V V
Figure 4: The architecture of an output port inside a relay node with Figure 4: The architecture of an output port inside a relay node with
interleaved regulators (IRs) and credit-based shaper (CBS) interleaved regulators (IRs) and credit-based shaper (CBS)
Each of the queuing subsystems for class A and B, contains Credit- Each of the queuing subsystems for classes A and B, contains Credit-
Based Shaper (CBS). The CBS serves a packet from a class according Based Shaper (CBS). The CBS serves a packet from a class according
to the available credit for that class. The credit for each class A to the available credit for that class. The credit for each class A
or B increases based on the idle slope, and decreases based on the or B increases based on the idle slope, and decreases based on the
send slope, both of which are parameters of the CBS (Section 8.6.8.2 send slope, both of which are parameters of the CBS (Section 8.6.8.2
of [IEEE8021Q]). The CDT and BE0-BE4 flows are served by separate of [IEEE8021Q]). The CDT and BE0-BE4 flows are served by separate
queuing subsystems. Then, packets from all flows are served by a queuing subsystems. Then, packets from all flows are served by a
transmission selection subsystem that serves packets from each class transmission selection subsystem that serves packets from each class
based on its priority. All subsystems are non-preemptive. based on its priority. All subsystems are non-preemptive.
Guarantees for AVB traffic can be provided only if CDT traffic is Guarantees for AVB traffic can be provided only if CDT traffic is
bounded; it is assumed that the CDT traffic has leaky bucket arrival bounded; it is assumed that the CDT traffic has leaky bucket arrival
skipping to change at page 17, line 14 skipping to change at page 18, line 6
Additionally, it is assumed that the AVB flows are also regulated at Additionally, it is assumed that the AVB flows are also regulated at
their source according to leaky bucket arrival curve. At the source, their source according to leaky bucket arrival curve. At the source,
the traffic satisfies its regulation constraint, i.e. the delay due the traffic satisfies its regulation constraint, i.e. the delay due
to interleaved regulator at source is ignored. to interleaved regulator at source is ignored.
At each DetNet transit node implementing an interleaved regulator, At each DetNet transit node implementing an interleaved regulator,
packets of multiple flows are processed in one FIFO queue; the packet packets of multiple flows are processed in one FIFO queue; the packet
at the head of the queue is regulated based on its leaky bucket at the head of the queue is regulated based on its leaky bucket
parameters; it is released at the earliest time at which this is parameters; it is released at the earliest time at which this is
possible without violating the constraint. The regulation parameters possible without violating the constraint.
for a flow (leaky bucket rate and bucket size) are the same at its
source and at all DetNet transit nodes along its path. The regulation parameters for a flow (leaky bucket rate and bucket
size) are the same at its source and at all DetNet transit nodes
along its path in the case of that all clocks are perfect. However,
in reality there is clock nonideality thoughout the DetNet domain
even with clock synchronization. This phenomenon causes inaccuracy
in the rates configured at the regulators that may lead to network
instability. To avoid that, when configuring the regulators, the
rates are set as the source rates with some positive margin.
[Thomas2020time] describes and provides solutions to this issue.
6.4.1. Delay Bound Calculation 6.4.1. Delay Bound Calculation
A delay bound of the queuing subsystem ([4] in Figure 1) for an AVB A delay bound of the queuing subsystem ((4) in Figure 1) for an AVB
flow of class A or B can be computed if the following condition flow of classes A or B can be computed if the following condition
holds: holds:
sum of leaky bucket rates of all flows of this class at this sum of leaky bucket rates of all flows of this class at this
transit node <= R, where R is given below for every class. transit node <= R, where R is given below for every class.
If the condition holds, the delay bounds for a flow of class X (A or If the condition holds, the delay bounds for a flow of class X (A or
B) is d_X and calculated as: B) is d_X and calculated as:
d_X = T_X + (b_t_X-L_min_X)/R_X - L_min_X/c d_X = T_X + (b_t_X-L_min_X)/R_X - L_min_X/c
skipping to change at page 18, line 24 skipping to change at page 19, line 24
described in [TSNwithATS]. described in [TSNwithATS].
6.4.2. Flow Admission 6.4.2. Flow Admission
The delay bound calculation requires some information about each The delay bound calculation requires some information about each
node. For each node, it is required to know the idle slope of CBS node. For each node, it is required to know the idle slope of CBS
for each class A and B (I_A and I_B), as well as the transmission for each class A and B (I_A and I_B), as well as the transmission
rate of the output link (c). Besides, it is necessary to have the rate of the output link (c). Besides, it is necessary to have the
information on each class, i.e. maximum packet length of classes A, information on each class, i.e. maximum packet length of classes A,
B, and BE. Moreover, the leaky bucket parameters of CDT (r_h,b_h) B, and BE. Moreover, the leaky bucket parameters of CDT (r_h,b_h)
should be known. To admit a flow/flows, their delay requirements should be known. To admit a flow/flows of classes A and B, their
should be guaranteed not to be violated. As described in delay requirements should be guaranteed not to be violated. As
Section 3.1, the two problems, static and dynamic, are addressed described in Section 3.1, the two problems, static and dynamic, are
separately. In either of the problems, the rate and delay should be addressed separately. In either of the problems, the rate and delay
guaranteed. Thus, should be guaranteed. Thus,
The static admission control: The static admission control:
The leaky bucket parameters of all flows are known, The leaky bucket parameters of all AVB flows are known,
therefore, for each flow f, a delay bound can be calculated. therefore, for each AVB flow f, a delay bound can be
The computed delay bound for every flow should not be more calculated. The computed delay bound for every AVB flow
than its delay requirement. Moreover, the sum of the rate of should not be more than its delay requirement. Moreover, the
each flow (r_f) should not be more than the rate allocated to sum of the rate of each flow (r_f) should not be more than
each class (R). If these two conditions hold, the the rate allocated to each class (R). If these two
configuration is declared admissible. conditions hold, the configuration is declared admissible.
The dynamic admission control: The dynamic admission control:
For dynamic admission control, we allocate to every node and For dynamic admission control, we allocate to every node and
class A or B, static value for rate (R) and maximum class A or B, static value for rate (R) and maximum
burstiness (b_t). In addition, for every node and every burstiness (b_t). In addition, for every node and every
class A and B, two counters are maintained: class A and B, two counters are maintained:
R_acc is equal to the sum of the leaky-bucket rates of all R_acc is equal to the sum of the leaky-bucket rates of all
flows of this class already admitted at this node; At all flows of this class already admitted at this node; At all
times, we must have: times, we must have:
R_acc <=R, (Eq. 1) R_acc <=R, (Eq. 1)
b_acc is equal to the sum of the bucket sizes of all flows b_acc is equal to the sum of the bucket sizes of all flows
of this class already admitted at this node; At all times, of this class already admitted at this node; At all times,
we must have: we must have:
b_acc <=b_t. (Eq. 2) b_acc <=b_t. (Eq. 2)
A new flow is admitted at this node, if Eqs. (1) and (2) A new AVB flow is admitted at this node, if Eqs. (1) and (2)
continue to be satisfied after adding its leaky bucket rate continue to be satisfied after adding its leaky bucket rate
and bucket size to R_acc and b_acc. A flow is admitted in and bucket size to R_acc and b_acc. An AVB flow is admitted
the network, if it is admitted at all nodes along its path. in the network, if it is admitted at all nodes along its
When this happens, all variables R_acc and b_acc along its path. When this happens, all variables R_acc and b_acc along
path must be incremented to reflect the addition of the flow. its path must be incremented to reflect the addition of the
Similarly, when a flow leaves the network, all variables flow. Similarly, when an AVB flow leaves the network, all
R_acc and b_acc along its path must be decremented to reflect variables R_acc and b_acc along its path must be decremented
the removal of the flow. to reflect the removal of the flow.
The choice of the static values of R and b_t at all nodes and classes The choice of the static values of R and b_t at all nodes and classes
must be done in a prior configuration phase; R controls the bandwidth must be done in a prior configuration phase; R controls the bandwidth
allocated to this class at this node, b_t affects the delay bound and allocated to this class at this node, b_t affects the delay bound and
the buffer requirement. R must satisfy the constraints given in the buffer requirement. R must satisfy the constraints given in
Annex L.1 of [IEEE8021Q]. Annex L.1 of [IEEE8021Q].
6.5. IntServ 6.5. IntServ
Integrated service (IntServ) is an architecture that specifies the Integrated service (IntServ) is an architecture that specifies the
elements to guarantee quality of service (QoS) on networks. elements to guarantee quality of service (QoS) on networks [RFC2212].
The flow, at the source, has a leaky bucket arrival curve with two The flow, at the source, has a leaky bucket arrival curve with two
parameters r as rate and b as bucket size, i.e., the amount of bits parameters r as rate and b as bucket size, i.e., the amount of bits
entering a node within a time interval t is bounded by r t + b. entering a node within a time interval t is bounded by r t + b.
If a resource reservation on a path is applied, a node provides a If a resource reservation on a path is applied, a node provides a
guaranteed rate R and maximum service latency of T. This can be guaranteed rate R and maximum service latency of T. This can be
interpreted in a way that the bits might have to wait up to T before interpreted in a way that the bits might have to wait up to T before
being served with a rate greater or equal to R. The delay bound of being served with a rate greater or equal to R. The delay bound of
the flow traversing the node is T + b / R. the flow traversing the node is T + b / R.
skipping to change at page 20, line 14 skipping to change at page 21, line 14
If more information about the flow is known, e.g. the peak rate, the If more information about the flow is known, e.g. the peak rate, the
delay bound is more complicated; the detail is available in delay bound is more complicated; the detail is available in
Section 1.4.1 of [NetCalBook]. Section 1.4.1 of [NetCalBook].
6.6. Cyclic Queuing and Forwarding 6.6. Cyclic Queuing and Forwarding
Annex T of [IEEE8021Q] describes Cyclic Queuing and Forwarding (CQF), Annex T of [IEEE8021Q] describes Cyclic Queuing and Forwarding (CQF),
which provides bounded latency and zero congestion loss using the which provides bounded latency and zero congestion loss using the
time-scheduled gates of [IEEE8021Q] section 8.6.8.4. For a given time-scheduled gates of [IEEE8021Q] section 8.6.8.4. For a given
DetNet class of service, a set of two or more buffers is provided at class of DetNet flows, a set of two or more buffers is provided at
the output queue layer of Figure 3. A cycle time T_c is configured the output queue layer of Figure 3. A cycle time T_c is configured
for each class c, and all of the buffer sets in a class swap buffers for each class of DetNet flows c, and all of the buffer sets in a
simultaneously throughout the DetNet domain at that cycle rate, all class of DetNet flows swap buffers simultaneously throughout the
in phase. In such a mechanism, the regulator, mentioned in Figure 1, DetNet domain at that cycle rate, all in phase. In such a mechanism,
is not required. the regulator, mentioned in Figure 1, is not required.
In the case of two-buffer CQF, each class c has two buffers, namely In the case of two-buffer CQF, each class of DetNet flows c has two
buffer1 and buffer2. In a cycle (i) when buffer1 accumulates buffers, namely buffer1 and buffer2. In a cycle (i) when buffer1
received packets from the node's reception ports, buffer2 transmits accumulates received packets from the node's reception ports, buffer2
the already stored packets from the previous cycle (i-1). In the transmits the already stored packets from the previous cycle (i-1).
next cycle (i+1), buffer2 stores the received packets and buffer1 In the next cycle (i+1), buffer2 stores the received packets and
transmits the packets received in cycle (i). The duration of each buffer1 transmits the packets received in cycle (i). The duration of
cycle is T_c. each cycle is T_c.
The per-hop latency is trivially determined by the cycle time T_c: The per-hop latency is trivially determined by the cycle time T_c:
the packet transmitted from a node at a cycle (i), is transmitted the packet transmitted from a node at a cycle (i), is transmitted
from the next node at cycle (i+1). Hence, the maximum delay from the next node at cycle (i+1). Hence, the maximum delay
experienced by a given packet is from the beginning of cycle (i) to experienced by a given packet is from the beginning of cycle (i) to
the end of cycle (i+1), or 2T_c; also, the minimum delay is from the the end of cycle (i+1), or 2T_c; also, the minimum delay is from the
end of cycle (i) to the beginning of cycle (i+1), i.e., zero. Then, end of cycle (i) to the beginning of cycle (i+1), i.e., zero. Then,
if the packet traverses h hops, the maximum delay is: if the packet traverses h hops, the maximum delay is:
(h+1) T_c (h+1) T_c
skipping to change at page 21, line 5 skipping to change at page 22, line 4
which gives a latency variation of 2T_c. which gives a latency variation of 2T_c.
The cycle length T_c should be carefully chosen; it needs to be large The cycle length T_c should be carefully chosen; it needs to be large
enough to accomodate all the DetNet traffic, plus at least one enough to accomodate all the DetNet traffic, plus at least one
maximum interfering packet, that can be received within one cycle. maximum interfering packet, that can be received within one cycle.
Also, the value of T_c includes a time interval, called dead time Also, the value of T_c includes a time interval, called dead time
(DT), which is the sum of the delays 1,2,3,4 defined in Figure 1. (DT), which is the sum of the delays 1,2,3,4 defined in Figure 1.
The value of DT guarantees that the last packet of one cycle in a The value of DT guarantees that the last packet of one cycle in a
node is fully delivered to a buffer of the next node is the same node is fully delivered to a buffer of the next node is the same
cycle. A two-buffer CQF is recommended if DT is small compared to cycle. A two-buffer CQF is recommended if DT is small compared to
T_c. For a large DT, CQF with more buffers can be used. T_c. For a large DT, CQF with more buffers can be used and a cycle
identification label can be added to the packets.
Ingress conditioning (Section 4.3) may be required if the source of a Ingress conditioning (Section 4.3) may be required if the source of a
DetNet flow does not, itself, employ CQF. Since there are no per- DetNet flow does not, itself, employ CQF. Since there are no per-
flow parameters in the CQF technique, per-hop configuration is not flow parameters in the CQF technique, per-hop configuration is not
required in the CQF forwarding nodes. required in the CQF forwarding nodes.
7. References 7. Example application on DetNet IP network
7.1. Normative References This section provides an example application of this document on a
DetNet-enabled IP network. Consider Figure 5, taken from Section 3
of [RFC8939], that shows a simple IP network:
[I-D.ietf-detnet-ip] o The end-system 1 implements IntServ as in Section 6.5 between
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A., itself and relay node 1.
and S. Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-
ip-05 (work in progress), February 2020.
[I-D.ietf-detnet-mpls] o Sub-network 1 is a TSN network. The nodes in subnetwork 1
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A., implement credit-based shapers with asynchronous traffic shaping
Bryant, S., and J. Korhonen, "DetNet Data Plane: MPLS", as in Section 6.4.
draft-ietf-detnet-mpls-05 (work in progress), February
2020. o Sub-network 2 is a TSN network. The nodes in subnetwork 2
implement cyclic queuing and forwarding with two buffers as in
Section 6.6.
o The relay nodes 1 and 2 implement credit-based shapers with
asynchronous traffic shaping as in Section 6.4. They also perform
the aggregation and mapping of IP DetNet flows to TSN streams
(Section 4.4 of [I-D.ietf-detnet-ip-over-tsn]).
DetNet IP Relay Relay DetNet IP
End-System Node 1 Node 2 End-System
1 2
+----------+ +----------+
| Appl. |<------------ End-to-End Service ----------->| Appl. |
+----------+ ............ ........... +----------+
| Service |<-: Service :-- DetNet flow --: Service :->| Service |
+----------+ +----------+ +----------+ +----------+
|Forwarding| |Forwarding| |Forwarding| |Forwarding|
+--------.-+ +-.------.-+ +-.---.----+ +-------.--+
: Link : \ ,-----. / \ ,-----. /
+......+ +----[ Sub- ]----+ +-[ Sub- ]-+
[Network] [Network]
`--1--' `--2--'
|<--------------------- DetNet IP --------------------->|
|<--- d1 --->|<--------------- d2_p --------------->|<-- d3_p -->|
Figure 5: A Simple DetNet-Enabled IP Network, taken from RFC8939
Consider a fully centeralized control plane for the network of
Figure 5 as described in Section 3.2 of
[I-D.ietf-detnet-controller-plane-framework]. Suppose end-system 1
wants to create a DetNet flow with traffic specification destined to
end-system 2 with end-to-end delay bound requirement D. Therefore,
the control plane receives a flow establishment request and
calculates a number of valid paths through the network (Section 3.2
of [I-D.ietf-detnet-controller-plane-framework]). To select a proper
path, the control plane needs to compute an end-to-end delay bound at
every node of each selected path p.
The end-to-end delay bound is d1 + d2_p + d3_p, where d1 is the delay
bound from end-system 1 to the entrance of relay node 1, d2_p is the
delay bound for path p from relay node 1 to entrance of the first
node in sub-network 2, and d3_p the delay bound of path p from the
first node in sub-network 2 to end-system 2. The computation of d1
is explained in Section 6.5. Since the relay node 1, sub-network 1
and relay node 2 implement aggregate queuing, we use the results in
Section 4.2.2 and Section 6.4 to compute d2_p for the path p.
Finally, d3_p is computed using the delay bound computation of
Section 6.6. Any path p such that d1 + d2_p + d3_p <= D satisfies
the delay bound requirement of the flow. If there is no such path,
the control plane may compute new set of valid paths and redo the
delay bound computation or do not admit the DetNet flow.
As soon as the control plane selects a path that satisfies the delay
bound constraint, it allocates and reserves the resources in the path
for the DetNet flow (Section 4.2
[I-D.ietf-detnet-controller-plane-framework]).
8. Security considerations
Detailed security considerations for DetNet are cataloged in
[I-D.ietf-detnet-security], and more general security considerations
are described in [RFC8655].
Security aspects that are unique to DetNet are those whose aim is to
provide the specific QoS aspects of DetNet, specifically bounded end-
to-end delivery latency and zero congestion loss. Achieving such
loss rates and bounded latency may not be possible in the face of a
highly capable adversary, such as the one envisioned by the Internet
Threat Model of BCP 72 [RFC3552] that can arbitrarily drop or delay
any or all traffic. In order to present meaningful security
considerations, we consider a somewhat weaker attacker who does not
control the physical links of the DetNet domain but may have the
ability to control a network node within the boundary of the DetNet
domain.
A security consideration for this document is to secure the resource
reservation signaling for DetNet flows. Any forge or manipulation of
packets during reservation may lead the flow not to be admitted or
face delay bound violation. Security mitigation for this issue is
describedd in Section 7.6 of [I-D.ietf-detnet-security].
9. IANA considerations
This document has no IANA actions.
10. References
10.1. Normative References
[I-D.ietf-detnet-security]
E. Grossman, T. Mizrahi, and A. Hacker, "Deterministic
Networking (DetNet) Security Considerations draft-ietf-
detnet-security-14", <https://tools.ietf.org/html/draft-
ietf-detnet-security-14>.
[RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification [RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212, of Guaranteed Quality of Service", RFC 2212,
DOI 10.17487/RFC2212, September 1997, DOI 10.17487/RFC2212, September 1997,
<https://www.rfc-editor.org/info/rfc2212>. <https://www.rfc-editor.org/info/rfc2212>.
[RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis, [RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
"Packet Pseudowire Encapsulation over an MPLS PSN", "Packet Pseudowire Encapsulation over an MPLS PSN",
RFC 6658, DOI 10.17487/RFC6658, July 2012, RFC 6658, DOI 10.17487/RFC6658, July 2012,
<https://www.rfc-editor.org/info/rfc6658>. <https://www.rfc-editor.org/info/rfc6658>.
[RFC7806] Baker, F. and R. Pan, "On Queuing, Marking, and Dropping", [RFC7806] Baker, F. and R. Pan, "On Queuing, Marking, and Dropping",
RFC 7806, DOI 10.17487/RFC7806, April 2016, RFC 7806, DOI 10.17487/RFC7806, April 2016,
<https://www.rfc-editor.org/info/rfc7806>. <https://www.rfc-editor.org/info/rfc7806>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655, "Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019, DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>. <https://www.rfc-editor.org/info/rfc8655>.
7.2. Informative References [RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
10.2. Informative References
[bennett2002delay] [bennett2002delay]
J.C.R. Bennett, K. Benson, A. Charny, W.F. Courtney, and J.C.R. Bennett, K. Benson, A. Charny, W.F. Courtney, and
J.-Y. Le Boudec, "Delay Jitter Bounds and Packet Scale J.-Y. Le Boudec, "Delay Jitter Bounds and Packet Scale
Rate Guarantee for Expedited Forwarding", Rate Guarantee for Expedited Forwarding",
<https://dl.acm.org/citation.cfm?id=581870>. <https://dl.acm.org/citation.cfm?id=581870>.
[charny2000delay] [charny2000delay]
A. Charny and J.-Y. Le Boudec, "Delay Bounds in a Network A. Charny and J.-Y. Le Boudec, "Delay Bounds in a Network
with Aggregate Scheduling", <https://link.springer.com/ with Aggregate Scheduling", <https://link.springer.com/
chapter/10.1007/3-540-39939-9_1>. chapter/10.1007/3-540-39939-9_1>.
[I-D.ietf-detnet-controller-plane-framework]
A. Malis, X. Geng, M. Chen, F. Qin, and B. Varga,
"Deterministic Networking (DetNet) Controller Plane
Framework draft-ietf-detnet-controller-plane-framework-
00", <https://datatracker.ietf.org/doc/html/draft-ietf-
detnet-controller-plane-framework>.
[I-D.ietf-detnet-ip-over-tsn]
B. Varga, J. Farkas, A. Malis, and S. Bryant, "DetNet Data
Plane: IP over IEEE 802.1 Time Sensitive Networking (TSN)
draft-ietf-detnet-ip-over-tsn-07",
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
ip-over-tsn-07>.
[IEEE8021Q] [IEEE8021Q]
IEEE 802.1, "IEEE Std 802.1Q-2018: IEEE Standard for Local IEEE 802.1, "IEEE Std 802.1Q-2018: IEEE Standard for Local
and metropolitan area networks - Bridges and Bridged and metropolitan area networks - Bridges and Bridged
Networks", 2018, Networks", 2018,
<http://ieeexplore.ieee.org/document/8403927>. <http://ieeexplore.ieee.org/document/8403927>.
[IEEE8021Qcr] [IEEE8021Qcr]
IEEE 802.1, "IEEE P802.1Qcr: IEEE Draft Standard for Local IEEE 802.1, "IEEE P802.1Qcr: IEEE Draft Standard for Local
and metropolitan area networks - Bridges and Bridged and metropolitan area networks - Bridges and Bridged
Networks - Amendment: Asynchronous Traffic Shaping", 2017, Networks - Amendment: Asynchronous Traffic Shaping", 2017,
skipping to change at page 22, line 39 skipping to change at page 26, line 33
[IEEE8021TSN] [IEEE8021TSN]
IEEE 802.1, "IEEE 802.1 Time-Sensitive Networking (TSN) IEEE 802.1, "IEEE 802.1 Time-Sensitive Networking (TSN)
Task Group", <http://www.ieee802.org/1/>. Task Group", <http://www.ieee802.org/1/>.
[IEEE8023] [IEEE8023]
IEEE 802.3, "IEEE Std 802.3-2018: IEEE Standard for IEEE 802.3, "IEEE Std 802.3-2018: IEEE Standard for
Ethernet", 2018, Ethernet", 2018,
<http://ieeexplore.ieee.org/document/8457469>. <http://ieeexplore.ieee.org/document/8457469>.
[le_boudec_theory_2018] [le_boudec2018theory]
J.-Y. Le Boudec, "A Theory of Traffic Regulators for J.-Y. Le Boudec, "A Theory of Traffic Regulators for
Deterministic Networks with Application to Interleaved Deterministic Networks with Application to Interleaved
Regulators", Regulators",
<https://ieeexplore.ieee.org/document/8519761>. <https://ieeexplore.ieee.org/document/8519761>.
[NetCalBook] [NetCalBook]
J.-Y. Le Boudec and P. Thiran, "Network calculus: a theory J.-Y. Le Boudec and P. Thiran, "Network calculus: a theory
of deterministic queuing systems for the internet", 2001, of deterministic queuing systems for the internet", 2001,
<https://ica1www.epfl.ch/PS_files/NetCal.htm>. <https://ica1www.epfl.ch/PS_files/NetCal.htm>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[Specht2016UBS] [Specht2016UBS]
J. Specht and S. Samii, "Urgency-Based Scheduler for Time- J. Specht and S. Samii, "Urgency-Based Scheduler for Time-
Sensitive Switched Ethernet Networks", Sensitive Switched Ethernet Networks",
<https://ieeexplore.ieee.org/abstract/document/7557870>. <https://ieeexplore.ieee.org/abstract/document/7557870>.
[Thomas2020time]
L. Thomas and J.-Y. Le Boudec, "On Time Synchronization
Issues in Time-Sensitive Networks with Regulators and
Nonideal Clocks",
<https://dl.acm.org/doi/10.1145/3393691.3394206>.
[TSNwithATS] [TSNwithATS]
E. Mohammadpour, E. Stai, M. Mohiuddin, and J.-Y. Le E. Mohammadpour, E. Stai, M. Mohiuddin, and J.-Y. Le
Boudec, "End-to-end Latency and Backlog Bounds in Time- Boudec, "End-to-end Latency and Backlog Bounds in Time-
Sensitive Networking with Credit Based Shapers and Sensitive Networking with Credit Based Shapers and
Asynchronous Traffic Shaping", Asynchronous Traffic Shaping",
<https://arxiv.org/abs/1804.10608/>. <https://arxiv.org/abs/1804.10608/>.
Authors' Addresses Authors' Addresses
Norman Finn Norman Finn
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