Internet Engineering Task Force (IETF) N. Finn
Request for Comments: 9320 Huawei Technologies Co. Ltd
Category: Informational J.-Y. Le Boudec
ISSN: 2070-1721 E. Mohammadpour
EPFL
J. Zhang
Huawei Technologies Co. Ltd
B. Varga
Ericsson
November 2022
Deterministic Networking (DetNet) Bounded Latency
Abstract
This document presents a timing model for sources, destinations, and
Deterministic Networking (DetNet) transit nodes. Using the model, it
provides a methodology to compute end-to-end latency and backlog
bounds for various queuing methods. The methodology can be used by
the management and control planes and by resource reservation
algorithms to provide bounded latency and zero congestion loss for
the DetNet service.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9320.
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Copyright (c) 2022 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction
2. Terminology and Definitions
3. DetNet Bounded Latency Model
3.1. Flow Admission
3.1.1. Static Latency Calculation
3.1.2. Dynamic Latency Calculation
3.2. Relay Node Model
4. Computing End-to-End Delay Bounds
4.1. Non-queuing Delay Bound
4.2. Queuing Delay Bound
4.2.1. Per-Flow Queuing Mechanisms
4.2.2. Aggregate Queuing Mechanisms
4.3. Ingress Considerations
4.4. Interspersed DetNet-Unaware Transit Nodes
5. Achieving Zero Congestion Loss
6. Queuing Techniques
6.1. Queuing Data Model
6.2. Frame Preemption
6.3. Time-Aware Shaper
6.4. Credit-Based Shaper with Asynchronous Traffic Shaping
6.4.1. Delay Bound Calculation
6.4.2. Flow Admission
6.5. Guaranteed Service
6.6. Cyclic Queuing and Forwarding
7. Example Application on DetNet IP Network
8. Security Considerations
9. IANA considerations
10. References
10.1. Normative References
10.2. Informative References
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
The ability for IETF Deterministic Networking (DetNet) or IEEE 802.1
Time-Sensitive Networking [IEEE8021TSN] to provide the DetNet
services of bounded latency and zero congestion loss depends upon
A. configuring and allocating network resources for the exclusive
use of DetNet flows;
B. identifying, in the data plane, the resources to be utilized by
any given packet; and
C. the detailed behavior of those resources, especially transmission
queue selection, so that latency bounds can be reliably assured.
As explained in [RFC8655], DetNet flows are notably characterized by
1. a maximum bandwidth, guaranteed either by the transmitter or by
strict input metering, and
2. a requirement for a guaranteed worst-case end-to-end latency.
That latency guarantee, in turn, provides the opportunity for the
network to supply enough buffer space to guarantee zero congestion
loss. In this document, it is assumed that the paths of DetNet flows
are fixed. Before the transmission of a DetNet flow, it is possible
to calculate end-to-end latency bounds and the amount of buffer space
required at each hop to ensure zero congestion loss; this can be used
by the applications identified in [RFC8578].
This document presents a timing model for sources, destinations, and
the DetNet transit nodes; using this model, it provides a methodology
to compute end-to-end latency and backlog bounds for various queuing
mechanisms that can be used by the management and control planes to
provide DetNet qualities of service. The methodology used in this
document accounts for the possibility of packet reordering within a
DetNet node. The bounds on the amount of packet reordering is out of
the scope of this document and can be found in
[PacketReorderingBounds]. Moreover, this document references
specific queuing mechanisms, mentioned in [RFC8655], as proofs of
concept that can be used to control packet transmission at each
output port and achieve the DetNet quality of service (QoS).
Using the model presented in this document, it is possible for an
implementer, user, or standards development organization to select a
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.
Section 7 provides an example application of the timing model
introduced in this document on a DetNet IP network with a combination
of different queuing mechanisms.
This document does not specify any resource reservation protocol or
control plane function. It does not describe all of the requirements
for that protocol or control plane function. It does describe
requirements for such resource reservation methods and for queuing
mechanisms that, if met, will enable them to work together.
2. Terminology and Definitions
This document uses the terms defined in [RFC8655]. Moreover, the
following terms are used in this document:
T-SPEC
TrafficSpecification, as defined in Section 5.5 of [RFC9016].
arrival curve
An arrival curve function alpha(t) is an upper bound on the number
of bits seen at an observation point within any time interval t.
CQF
Cyclic Queuing and Forwarding.
CBS
Credit-Based Shaper.
TSN
Time-Sensitive Networking.
PREOF
A collective name for Packet Replication, Elimination, and
Ordering Functions.
POF
A Packet Ordering Function is a function that reorders 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.
3. DetNet Bounded Latency Model
3.1. Flow Admission
This document assumes that the following paradigm is used to admit
DetNet flows:
1. Perform any configuration required by the DetNet transit nodes in
the network for aggregates of DetNet flows. This configuration
is done beforehand and not tied to any particular DetNet flow.
2. Characterize the new DetNet flow, particularly in terms of
required bandwidth.
3. Establish the path that the DetNet flow will take through the
network from the source to the destination(s). This can be a
point-to-point or a point-to-multipoint path.
4. Compute the worst-case end-to-end latency for the DetNet flow
using one of the methods below (Sections 3.1.1 and 3.1.2). In
the process, determine whether sufficient resources are available
for the DetNet flow to guarantee the required latency and to
provide zero congestion loss.
5. Assuming that the resources are available, commit those resources
to the DetNet flow. This may require adjusting the parameters
that control the filtering and/or queuing mechanisms at each hop
along the DetNet flow's path.
This paradigm can be implemented using peer-to-peer protocols or
using a central controller. In some situations, a lack of resources
can require backtracking and recursing through the above list.
Issues, such as service preemption of a DetNet flow in favor of
another, when resources are scarce, are not considered here. Also
not addressed is the question of how to choose the path to be taken
by a DetNet flow.
3.1.1. Static Latency Calculation
The static problem:
Given a network and a set of DetNet flows, compute an end-to-
end latency bound (if computable) for each DetNet flow and
compute the resources, particularly buffer space, required in
each DetNet transit node to achieve zero congestion loss.
In this calculation, all of the DetNet flows are known before the
calculation commences. This problem is of interest to relatively
static networks or static parts of larger networks. It provides
bounds on latency and buffer size. The calculations can be extended
to provide global optimizations, such as altering the path of one
DetNet flow in order to make resources available to another DetNet
flow with tighter constraints.
This calculation may be more difficult to perform than the dynamic
calculation (Section 3.1.2) because the DetNet flows passing through
one port on a DetNet transit node affect each other's latency. The
effects can even be circular, from node A to B to C and back to A.
On the other hand, the static calculation can often accommodate
queuing methods, such as transmission selection by strict priority,
that are unsuitable for the dynamic calculation.
3.1.2. Dynamic Latency Calculation
The dynamic problem:
Given a network whose maximum capacity for DetNet flows is
bounded by a set of static configuration parameters applied
to the DetNet transit nodes and given just one DetNet flow,
compute the worst-case end-to-end latency that can be
experienced by that flow, no matter what other DetNet flows
(within the network's configured parameters) might be created
or deleted in the future. Also, compute the resources,
particularly buffer space, required in each DetNet transit
node to achieve zero congestion loss.
This calculation is dynamic, in the sense that DetNet flows can be
added or deleted at any time, with a minimum of computation effort
and without affecting the guarantees already given to other DetNet
flows.
Dynamic latency calculation can be done based on the static one
described in Section 3.1.1; when a new DetNet flow is created or
deleted, the entire calculation for all DetNet flows is repeated. If
an already-established DetNet flow would be pushed beyond its latency
requirements by the new DetNet flow request, then the new DetNet flow
request can be refused or some other suitable action can be taken.
The choice of queuing methods is critical to the applicability of the
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 independent calculations for each DetNet flow. Some other
queuing methods (e.g., strict priority with the credit-based shaper
defined in Section 8.6.8.2 of [IEEE8021Q]) can be used for dynamic
DetNet flow creation but yield poorer latency and buffer space
guarantees than when that same queuing method is used for static
DetNet flow creation (Section 3.1.1).
3.2. Relay Node Model
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
see a breakdown of the per-hop latency experienced by a packet
passing through a DetNet transit node in terms that are suitable for
computing both hop-by-hop latency and per-hop buffer requirements.
DetNet transit node A DetNet transit node B
+-------------------------+ +------------------------+
| Queuing | | Queuing |
| Regulator subsystem | | Regulator subsystem |
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
-->+ | | | | | | | | | + +------>+ | | | | | | | | | + +--->
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
| | | |
+-------------------------+ +------------------------+
|<->|<------>|<------->|<->|<---->|<->|<------>|<------>|<->|<--
2,3 4 5 6 1 2,3 4 5 6 1 2,3
1: Output delay 4: Processing delay
2: Link delay 5: Regulation delay
3: Frame preemption delay 6: Queuing subsystem delay
Figure 1: Timing Model for DetNet or TSN
In Figure 1, we see two DetNet transit nodes that are connected via a
link. In this model, the only queues that we deal with explicitly
are attached to the output port; other queues are modeled as
variations in the other delay times (e.g., an input queue could be
modeled as either a variation in the link delay (2) or the processing
delay (4)). There are six delays that a packet can experience from
hop to hop.
1. Output delay
This is 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 physical link. If the queue is directly attached to the
physical port, output delay can be a constant. However, in many
implementations, a multiplexed connection separates the queuing
mechanism from a multi-port Network Interface Card (NIC). This
causes variations in the output delay that are hard for the
forwarding node to predict or control.
2. Link delay
This is the time taken from the transmission of the first bit of
the packet to the reception of the last bit, assuming that the
transmission is not suspended by a frame preemption event. This
delay has two components: the first-bit-out to first-bit-in delay
and the first-bit-in to last-bit-in delay that varies with packet
size. The former is typically constant. However, a virtual
"link" could exhibit a variable link delay.
3. Frame preemption delay
If the packet is interrupted in order to transmit another packet
or packets (e.g., frame preemption, as in [IEEE8023], clause 99),
an arbitrary delay can result.
4. Processing delay
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
(queuing subsystem if there is no regulator), as shown in
Figure 1. This delay can be variable and depends on the details
of the operation of the forwarding node.
5. Regulator queuing delay
A regulator, also known as shaper in [RFC2475], delays some or
all of the packets in a traffic stream in order to bring the
stream into compliance with an arrival curve; an arrival curve
'alpha(t)' is an upper bound on the number of bits observed
within any interval t. The regulator delay is the time spent
from the insertion of the last bit of a packet into a regulation
queue until the time the packet is declared eligible according to
its regulation constraints. We assume that this time can be
calculated based on the details of regulation policy. If there
is no regulation, this time is zero.
6. Queuing subsystem delay
This is the time spent for a packet from being declared eligible
until being selected for output on the next link. We assume that
this time is calculable based on the details of the queuing
mechanism. If there is no regulation, this time is from the
insertion of the packet into a queue until it is selected for
output on the next link.
Not shown in Figure 1 are the other output queues that we presume are
also attached to that same output port as the queue shown, and
against which this shown queue competes for transmission
opportunities.
In this analysis, the measurement is from the point at which a packet
is selected for output in a node to the point at which it is selected
for output in the next downstream node (i.e., the definition of a
"hop"). In general, any queue selection method that is suitable for
use in a DetNet network includes a detailed specification as to
exactly when packets are selected for transmission. Any variations
in any of the delay times 1-4 result in a need for additional buffers
in the queue. If all delays 1-4 are constant, then any variation in
the time at which packets are inserted into a queue depends entirely
on the timing of packet selection in the previous node. If delays
1-4 are not constant, then additional buffers are required in the
queue to absorb these variations. Thus:
* Variations in the output delay (1) require buffers to absorb that
variation in the next hop, so the output delay variations of the
previous hop (on each input port) must be known in order to
calculate the buffer space required on this hop.
* Variations in the processing delay (4) require additional output
buffers in the queues of that same DetNet transit node. Depending
on the details of the queuing subsystem delay (6) calculations,
these variations need not be visible outside the DetNet transit
node.
4. Computing End-to-End Delay Bounds
4.1. Non-queuing Delay Bound
End-to-end latency bounds can be computed using the delay model in
Section 3.2. Here, it is important to be aware that, for several
queuing mechanisms, the end-to-end latency bound is less than the sum
of the per-hop latency bounds. An end-to-end latency bound for one
DetNet flow can be computed as
end_to_end_delay_bound = non_queuing_delay_bound +
queuing_delay_bound
The two terms in the above formula are computed as follows.
First, at the h-th hop along the path of this DetNet flow, obtain an
upper-bound per-hop_non_queuing_delay_bound[h] on the sum of the
bounds over delays 1, 2, 3, and 4 of Figure 1. These upper bounds
are 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 [RFC9016]. Then, set non_queuing_delay_bound = the sum of per-
hop_non_queuing_delay_bound[h] over all hops h.
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
depends on the information on the arrival curve of this DetNet flow
and possibly of other flows in the network, as well as the specifics
of the queuing mechanisms deployed along the path of this DetNet
flow. Note that arrival curve of the DetNet flow at the source is
immediately specified by the T-SPEC of this flow. The computation of
queuing_delay_bound is described in Section 4.2 as a separate
section.
4.2. Queuing Delay Bound
For several queuing mechanisms, queuing_delay_bound is less than the
sum of upper bounds on the queuing delays (5 and 6) at every hop.
This occurs with (1) per-flow queuing and (2) aggregate queuing with
regulators, as explained in Sections 4.2.1, 4.2.2, and 6. For other
queuing mechanisms, the only available value of queuing_delay_bound
is the sum of the per-hop queuing delay bounds.
The computation of per-hop queuing delay bounds must account for the
fact that the arrival curve of a DetNet flow is no longer satisfied
at the ingress of a hop, since burstiness increases as one flow
traverses one DetNet transit node. If a regulator is placed at a
hop, an arrival curve of a DetNet flow at the entrance of the queuing
subsystem of this hop is the one configured at the regulator (also
called shaping curve in [NetCalBook]); otherwise, an arrival curve of
the flow can be derived using the delay jitter of the flow from the
last regulation point (the last regulator in the path of the flow if
there is any, otherwise the source of the flow) to the ingress of the
hop; more formally, assume a DetNet flow has an arrival curve at the
last regulation point equal to 'alpha(t)' and the delay jitter from
the last regulation point to the ingress of the hop is 'V'. Then,
the arrival curve at the ingress of the hop is 'alpha(t+V)'.
For example, consider a DetNet flow with T-SPEC "Interval: tau,
MaxPacketsPerInterval: K, MaxPayloadSize: L" at the source. Then, a
leaky-bucket arrival curve for such flow at the source is alpha(t)=r
* t+ b, t>0; alpha(0)=0, where r is the rate and b is the bucket
size, computed as
r = K * (L+L') / tau,
b = K * (L+L').
where L' is the size of any added networking technology-specific
encapsulation (e.g., MPLS label(s), UDP, or IP headers). Now, if the
flow has a delay jitter of 'V' from the last regulation point to the
ingress of a hop, an arrival curve at this point is r * t + b + r *
V, implying that the burstiness is increased by r*V. More detailed
information on arrival curves is available in [NetCalBook].
4.2.1. Per-Flow Queuing Mechanisms
With such mechanisms, each flow uses a separate queue inside every
node. The service for each queue is abstracted with a guaranteed
rate and a latency. For every DetNet flow, a per-node latency bound,
as well as an end-to-end latency bound, can be computed from the
traffic specification of this DetNet flow at its source and from the
values of rates and latencies at all nodes along its path. An
instance of per-flow queuing is Guaranteed Service [RFC2212], for
which the details of latency bound calculation are presented in
Section 6.5.
4.2.2. Aggregate Queuing Mechanisms
With such mechanisms, multiple flows are aggregated into macro-flows
and there is one FIFO queue per macro-flow. A practical example is
the credit-based shaper defined in Section 8.6.8.2 of [IEEE8021Q],
where a macro-flow is called a "class". One key issue in this
context is how to deal with the burstiness cascade; individual flows
that share a resource dedicated to a macro-flow may see their
burstiness increase, which may in turn cause increased burstiness to
other flows downstream of this resource. Computing delay upper
bounds for such cases is difficult and, in some conditions,
impossible [CharnyDelay] [BennettDelay]. Also, when bounds are
obtained, they depend on the complete configuration and must be
recomputed when one flow is added (i.e., the dynamic calculation in
Section 3.1.2).
A solution to deal with this issue for the DetNet flows is to reshape
them at every hop. This can be done with per-flow regulators (e.g.,
leaky-bucket shapers), but this requires per-flow queuing and defeats
the purpose of aggregate queuing. An alternative is the interleaved
regulator, which reshapes individual DetNet flows without per-flow
queuing [SpechtUBS] [IEEE8021Qcr]. With an interleaved regulator,
the packet at the head of the queue is regulated based on its (flow)
regulation constraints; it is released at the earliest time at which
this is possible without violating the constraint. One key feature
of a per-flow or interleaved regulator is that it does not increase
worst-case latency bounds [LeBoudecTheory]. Specifically, when an
interleaved regulator is appended to a FIFO subsystem, it does not
increase the worst-case delay of the latter. In Figure 1, when the
order of packets from the output of a queuing subsystem at node A to
the entrance of a regulator at node B is preserved, then the
regulator does not increase the worst-case latency bounds. This is
made possible if all the systems are FIFO or a DetNet Packet Ordering
Function (POF) is implemented just before the regulator. This
property does not hold if packet reordering occurs from the output of
a queuing subsystem to the entrance of the next downstream
interleaved regulator, e.g., at a non-FIFO switching fabric.
Figure 2 shows an example of a network with 5 nodes, an aggregate
queuing mechanism, and interleaved regulators, as in Figure 1. An
end-to-end delay bound for DetNet flow f, traversing nodes 1 to 5, is
calculated as follows:
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
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 DetNet flow
f. In fact, using the delay definitions in Section 3.2, Cij is a
bound on a sum of delays 1, 2, 3, and 6 of node i and delays 4 and 5
of node j. Similarly, S4 is a bound on sum of delays 1, 2, 3, and 6
of node 4. A practical example of the queuing model and delay
calculation is presented Section 6.4.
f
----------------------------->
+---+ +---+ +---+ +---+ +---+
| 1 |---| 2 |---| 3 |---| 4 |---| 5 |
+---+ +---+ +---+ +---+ +---+
\__C12_/\__C23_/\__C34_/\_S4_/
Figure 2: End-to-End Delay Computation Example
If packet reordering does not occur, the end-to-end latency bound
calculation provided here gives a tighter latency upper bound than
would be obtained by adding the latency bounds of each node in the
path of a DetNet flow [TSNwithATS].
4.3. Ingress Considerations
A sender can be a DetNet node that uses exactly the same queuing
methods as its adjacent DetNet transit node so that the latency and
buffer bounds calculations at the first hop are indistinguishable
from those at a later hop within the DetNet domain. On the other
hand, the sender may be DetNet unaware; in which case, some
conditioning of the DetNet flow may be necessary at the ingress
DetNet transit node. The ingress conditioning typically consists of
the regulators described in Section 3.2.
4.4. Interspersed DetNet-Unaware Transit Nodes
It is sometimes desirable to build a network that has both DetNet-
aware transit nodes and DetNet-unaware transit nodes and for a DetNet
flow to traverse an island of DetNet-unaware transit nodes while
still allowing the network to offer delay and congestion loss
guarantees. This is possible under certain conditions.
In general, when passing through a DetNet-unaware island, the island
may cause delay variation in excess of what would be caused by DetNet
nodes. That is, the DetNet flow might be "lumpier" after traversing
the DetNet-unaware island. DetNet guarantees for delay and buffer
requirements can still be calculated and met if and only if the
following are true:
1. The latency variation across the DetNet-unaware island must be
bounded and calculable.
2. An ingress conditioning function (Section 4.3) is required at the
reentry to the DetNet-aware domain. This will, at least, require
some extra buffering to accommodate the additional delay
variation and thus further increases the latency bound.
The ingress conditioning is exactly the same problem as that of a
sender at the edge of the DetNet domain. The requirement for bounds
on the latency variation across the DetNet-unaware island is
typically the most difficult to achieve. Without such a bound, it is
obvious that DetNet cannot deliver its guarantees, so a DetNet-
unaware island that cannot offer bounded latency variation cannot be
used to carry a DetNet flow.
5. Achieving Zero Congestion Loss
When the input rate to an output queue exceeds the output rate for a
sufficient length of time, the queue must overflow. This is
congestion loss, and this is what DetNet seeks to avoid.
To avoid congestion losses, an upper bound on the backlog present in
the regulator and queuing subsystem of Figure 1 must be computed
during resource reservation. This bound depends on the set of flows
that use these queues, the details of the specific queuing mechanism,
and an upper bound on the processing delay (4). The queue must
contain the packet in transmission, plus all other packets that are
waiting to be selected for output. A conservative backlog bound that
applies to all systems can be derived as follows.
The backlog bound is counted in data units (bytes or words of
multiple bytes) that are relevant for buffer allocation. For every
flow or an aggregate of flows, we need one buffer space for the
packet in transmission, plus space for the packets that are waiting
to be selected for output.
Let
* total_in_rate be the sum of the line rates of all input ports that
send traffic to this output port. The value of total_in_rate is
in data units (e.g., bytes) per second.
* nb_input_ports be the number of input ports that send traffic to
this output port.
* max_packet_length be the maximum packet size for packets that may
be sent to this output port. This is counted in data units.
* max_delay456 be an upper bound, in seconds, on the sum of the
processing delay (4) and the queuing delays (5 and 6) for any
packet at this output port.
Then, a bound on the backlog of traffic in the queue at this output
port is
backlog_bound = (nb_input_ports * max_packet_length) +
(total_in_rate * max_delay456)
The above bound is over the backlog caused by the traffic entering
the queue from the input ports of a DetNet node. If the DetNet node
also generates packets (e.g., creation of new packets or replication
of arriving packets), the bound must accordingly incorporate the
introduced backlog.
6. Queuing Techniques
In this section, we present a general queuing data model, as well as
some examples of queuing mechanisms. For simplicity of latency bound
computation, we assume a leaky-bucket arrival curve for each DetNet
flow at the source. Also, at each DetNet transit node, the service
for each queue is abstracted with a minimum guaranteed rate and a
latency [NetCalBook].
6.1. Queuing Data Model
Sophisticated queuing mechanisms are available in Layer 3 (L3) (e.g.,
see [RFC7806] for an overview). In general, we assume that "Layer 3"
queues, shapers, meters, etc., are precisely the "regulators" shown
in Figure 1. The "queuing subsystems" in this figure are FIFO. They
are not the province solely of bridges; they are an essential part of
any DetNet transit node. As illustrated by numerous implementation
examples, some of the "Layer 3" mechanisms described in documents,
such as [RFC7806], are often integrated in an implementation, with
the "Layer 2" mechanisms also implemented in the same node. An
integrated model is needed in order to successfully predict the
interactions among the different queuing mechanisms needed in a
network carrying both DetNet flows and non-DetNet flows.
Figure 3 shows the general model for the flow of packets through the
queues of a DetNet transit node. The DetNet packets are mapped to a
number of regulators. Here, we assume that the Packet Replication,
Elimination, and Ordering Functions (PREOF) are performed before the
DetNet packets enter the regulators. All packets are assigned to a
set of queues. Packets compete for the selection to be passed to
queues in the queuing subsystem. Packets again are selected for
output from the queuing subsystem.
|
+--------------------------------V----------------------------------+
| Queue assignment |
+--+------+----------+---------+-----------+-----+-------+-------+--+
| | | | | | | |
+--V-+ +--V-+ +--V--+ +--V--+ +--V--+ | | |
|Flow| |Flow| |Flow | |Flow | |Flow | | | |
| 0 | | 1 | ... | i | | i+1 | ... | n | | | |
| reg| | reg| | reg | | reg | | reg | | | |
+--+-+ +--+-+ +--+--+ +--+--+ +--+--+ | | |
| | | | | | | |
+--V------V----------V--+ +--V-----------V--+ | | |
| Trans. selection | | Trans. select. | | | |
+----------+------------+ +-----+-----------+ | | |
| | | | |
+--V--+ +--V--+ +--V--+ +--V--+ +--V--+
| out | | out | | out | | out | | out |
|queue| |queue| |queue| |queue| |queue|
| 1 | | 2 | | 3 | | 4 | | 5 |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| | | | |
+----------V----------------------V--------------V-------V-------V--+
| Transmission selection |
+---------------------------------+---------------------------------+
|
V
Figure 3: IEEE 802.1Q Queuing Model: Data Flow
Some relevant mechanisms are hidden in this figure and are performed
in the queue boxes:
* discarding packets because a queue is full
* discarding packets marked "yellow" by a metering function in
preference to discarding "green" packets [RFC2697]
Ideally, neither of these actions are performed on DetNet packets.
Full queues for DetNet packets occur only when a DetNet flow is
misbehaving, and the DetNet QoS does not include "yellow" service for
packets in excess of a committed rate.
The queue assignment function can be quite complex, even in a bridge
[IEEE8021Q], because of the introduction of per-stream filtering and
policing ([IEEE8021Q], clause 8.6.5.1). In addition to the Layer 2
priority expressed in the 802.1Q VLAN tag, a DetNet transit node can
utilize the information from the non-exhaustive list below to assign
a packet to a particular queue:
* input port
* selector based on a rotating schedule that starts at regular,
time-synchronized intervals and has nanosecond precision
* MAC addresses, VLAN ID, IP addresses, Layer 4 port numbers, and
Differentiated Services Code Point (DSCP) [RFC8939] [RFC8964]
* the queue assignment function can contain metering and policing
functions
* MPLS and/or pseudowire labels [RFC6658]
The "Transmission selection" function decides which queue is to
transfer its oldest packet to the output port when a transmission
opportunity arises.
6.2. Frame Preemption
In [IEEE8021Q] and [IEEE8023], the transmission of a frame can be
interrupted by one or more "express" frames; then, the interrupted
frame can continue transmission. The frame preemption is modeled as
consisting of two MAC/PHY stacks: one for packets that can be
interrupted and one for packets that can interrupt the interruptible
packets. Only one layer of frame preemption is supported -- a
transmitter cannot have more than one interrupted frame in progress.
DetNet flows typically pass through the interrupting MAC. For those
DetNet flows with T-SPEC, latency bounds can be calculated by the
methods provided in the following sections that account for the
effect of frame preemption, according to the specific queuing
mechanism that is used in DetNet nodes. Best-effort queues pass
through the interruptible MAC and can thus be preempted.
6.3. Time-Aware Shaper
In [IEEE8021Q], the notion of time-scheduling queue gates is
described in Section 8.6.8.4. On each node, the transmission
selection for packets is controlled by time-synchronized gates; each
output queue is associated with a gate. The gates can be either open
or closed. The states of the gates are determined by the gate
control list (GCL). The GCL specifies the opening and closing times
of the gates. The design of the GCL must satisfy the requirement of
latency upper bounds of all DetNet flows; therefore, those DetNet
flows that traverse a network that uses this kind of shaper must have
bounded latency if the traffic and nodes are conformant.
Note that scheduled traffic service relies on a synchronized network
and coordinated GCL configuration. Synthesis of the GCL on multiple
nodes in a network is a scheduling problem considering all DetNet
flows traversing the network, which is a nondeterministic polynomial-
time hard (NP-hard) problem [Sch8021Qbv]. Also, at the time of
writing, scheduled traffic service supports no more than eight
traffic queues, typically using up to seven priority queues and at
least one best effort.
6.4. Credit-Based Shaper with Asynchronous Traffic Shaping
In this queuing model, it is assumed that the DetNet nodes are FIFO.
We consider the four traffic classes (Definition 3.268 of
[IEEE8021Q]): control-data traffic (CDT), class A, class B, and best
effort (BE) in decreasing order of priority. Flows of classes A and
B are DetNet flows that are less critical than CDT (such as studio
audio and video traffic, as in IEEE 802.1BA Audio-Video-Bridging).
This model is a subset of Time-Sensitive Networking, as described
next.
Based on the timing model described in Figure 1, contention occurs
only at the output port of a DetNet transit node; therefore, the
focus of the rest of this subsection is on the regulator and queuing
subsystem in the output port of a DetNet transit node. The input
flows are identified using the information in (Section 5.1 of
[RFC8939]). Then, they are aggregated into eight macro-flows based
on their service requirements; we refer to each macro-flow as a
class. The output port performs aggregate scheduling with eight
queues (queuing subsystems): one for CDT, one for class A flows, one
for class B flows, and five for BE traffic denoted as BE0-BE4. The
queuing policy for each queuing subsystem is FIFO. In addition, each
node output port also performs per-flow regulation for class A and B
flows using an interleaved regulator (IR). This regulation is called
asynchronous traffic shaping [IEEE8021Qcr]. Thus, at each output
port of a node, there is one interleaved regulator per input port and
per class; the interleaved regulator is mapped to the regulator
depicted in Figure 1. The detailed picture of scheduling and
regulation architecture at a node output port is given by Figure 4.
The packets 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 a queuing subsystem; there is no regulator for CDT and BE
flows.
+--+ +--+ +--+ +--+
| | | | | | | |
|IR| |IR| |IR| |IR|
| | | | | | | |
+-++XXX++-+ +-++XXX++-+
| | | |
| | | |
+---+ +-v-XXX-v-+ +-v-XXX-v-+ +-----+ +-----+ +-----+ +-----+ +-----+
| | | | | | |Class| |Class| |Class| |Class| |Class|
|CDT| | Class A | | Class B | | BE4 | | BE3 | | BE2 | | BE1 | | BE0 |
| | | | | | | | | | | | | | | |
+-+-+ +----+----+ +----+----+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| | | | | | | |
| +-v-+ +-v-+ | | | | |
| |CBS| |CBS| | | | | |
| +-+-+ +-+-+ | | | | |
| | | | | | | |
+-v--------v-----------v---------v-------V-------v-------v-------v--+
| Strict Priority selection |
+--------------------------------+----------------------------------+
|
V
Figure 4: The Architecture of an Output Port inside a Relay Node with
Interleaved Regulators (IRs) and a Credit-Based Shaper (CBS)
Each of the queuing subsystems for classes A and B contains a credit-
based shaper (CBS). The CBS serves a packet from a class according
to the available credit for that class. As described in
Section 8.6.8.2 and Annex L.1 of [IEEE8021Q], the credit for each
class A or B increases based on the idle slope (as guaranteed rate)
and decreases based on the sendslope (typically equal to the
difference between the guaranteed and the output link rates), both of
which are parameters of the CBS. The CDT and BE0-BE4 flows are
served by separate queuing subsystems. Then, packets from all flows
are served by a transmission selection subsystem that serves packets
from each class based on its priority. All subsystems are non-
preemptive. Guarantees for class A and B traffic can be provided
only if CDT is bounded. It is assumed that the CDT has a leaky-
bucket arrival curve with two parameters: r_h as rate and b_h as
bucket size. That is, the amount of bits entering a node within a
time interval t is bounded by r_h * t + b_h.
Additionally, it is assumed that the class A and B flows are also
regulated at their source according to a leaky-bucket arrival curve.
At the source, the traffic satisfies its regulation constraint, i.e.,
the delay due to interleaved regulator at the source is ignored.
At each DetNet transit node implementing an interleaved regulator,
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 parameters. It is released at the earliest time at which this
is possible without violating the constraint.
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 where all clocks are perfect. However, in
reality, there is clock non-ideality throughout 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 instability, the rates are set as the source
rates with some positive margin when configuring regulators.
[ThomasTime] describes and provides solutions to this issue.
6.4.1. Delay Bound Calculation
A delay bound of the queuing subsystem ((4) in Figure 1) of a given
DetNet node for a flow of class A or B can be computed if the
following condition holds:
The sum of leaky-bucket rates of all flows of this class at this
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
B) is d_X and calculated as:
d_X = T_X + (b_t_X-L_min_X)/R_X - L_min_X/c
where L_min_X is the minimum packet lengths of class X (A or B); c is
the output link transmission rate; and b_t_X is the sum of the b term
(bucket size) for all the flows of the class X. Parameters R_X and
T_X are calculated as follows for class A and B, separately.
If the flow is of class A:
R_A = I_A * (c-r_h)/ c
T_A = (L_nA + b_h + r_h * L_n/c)/(c-r_h)
where I_A is the idle slope for class A; L_nA is the maximum packet
length of class B and BE packets; L_n is the maximum packet length of
classes A, B, and BE; and r_h is the rate and b_h is the bucket size
of CDT leaky-bucket arrival curve.
If the flow is of class B:
R_B = I_B * (c-r_h)/ c
T_B = (L_BE + L_A + L_nA * I_A/(c_h-I_A) + b_h + r_h * L_n/
c)/(c-r_h)
where I_B is the idle slope for class B; L_A is the maximum packet
length of class A; and L_BE is the maximum packet length of class BE.
Then, as discussed in Section 4.2.2, an interleaved regulator does
not increase the delay bound of the upstream queuing subsystem;
therefore, an end-to-end delay bound for a DetNet flow of class X (A
or B) is the sum of d_X_i for all node i in the path of the flow,
where d_X_i is the delay bound of queuing subsystem in node i, which
is computed as above. According to the notation in Section 4.2.2,
the delay bound of the queuing subsystem in a node i and interleaved
regulator in node j, i.e., Cij, is:
Cij = d_X_i
More information of delay analysis in such a DetNet transit node is
described in [TSNwithATS].
6.4.2. Flow Admission
The delay bound calculation requires some information about each
node. For each node, it is required to know the idle slope of the
CBS 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
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)
must be known. To admit a flow or flows of classes A and B, their
delay requirements must be guaranteed not to be violated. As
described in Section 3.1, the two problems (static and dynamic) are
addressed separately. In either of the problems, the rate and delay
must be guaranteed. Thus,
The static admission control:
The leaky-bucket parameters of all class A or B flows are
known; therefore, for each flow f of either class A or B, a
delay bound can be calculated. The computed delay bound for
every flow of class A or B must not be more than its delay
requirement. Moreover, the sum of the rate of each flow
(r_f) must not be more than the rate allocated to each class
(R). If these two conditions hold, the configuration is
declared admissible.
The dynamic admission control:
For dynamic admission control, we allocate a static value
for rate (R) and a maximum bucket size (b_t) to every node
and each class A or B. In addition, for every node and
each class A or B, two counters are maintained:
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
times, we must have:
R_acc <= R, (Eq. 1)
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,
we must have:
b_acc <= b_t. (Eq. 2)
A new class A or B flow is admitted at this node if Eqs. (1)
and (2) continue to be satisfied after adding its leaky-
bucket rate and bucket size to R_acc and b_acc. A class A or
B flow is admitted in the network if it is admitted at all
nodes along its path. When this happens, all variables R_acc
and b_acc along its path must be incremented to reflect the
addition of the flow. Similarly, when a class A or B flow
leaves the network, all variables R_acc and b_acc along its
path must be decremented to reflect the removal of the flow.
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
allocated to this class at this node, and b_t affects the delay bound
and the buffer requirement. The value of R must be set such that
R <= I_X*(c-r_h)/c
where I_X is the idleslope of credit-based shaper for class X={A,B},
c is the transmission rate of the output link, and r_h is the leaky-
bucket rate of the CDT class.
6.5. Guaranteed Service
The Guaranteed Service is defined in [RFC2212]. 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 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
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
being served with a rate greater or equal to R. The delay bound of
the flow traversing the node is T + b / R.
Consider a Guaranteed Service [RFC2212] path including a sequence of
nodes, where the i-th node provides a guaranteed rate R_i and maximum
service latency of T_i. Then, the end-to-end delay bound for a flow
on this can be calculated as sum(T_i) + b / min(R_i).
The provided delay bound is based on a simple case of Guaranteed
Service, where only a guaranteed rate and maximum service latency and
a leaky-bucket arrival curve are available. If more information
about the flow is known, e.g., the peak rate, the delay bound is more
complicated; the details are available in [RFC2212] and Section 1.4.1
of [NetCalBook].
6.6. Cyclic Queuing and Forwarding
Annex T of [IEEE8021Q] describes Cyclic Queuing and Forwarding (CQF),
which provides bounded latency and zero congestion loss using the
time-scheduled gates of Section 8.6.8.4 of [IEEE8021Q]. For a given
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
for each class of DetNet flows c, and all of the buffer sets in a
class of DetNet flows swap buffers simultaneously throughout the
DetNet domain at that cycle rate, all in phase. In such a mechanism,
the regulator, as mentioned in Figure 1, is not required.
In the case of two-buffer CQF, each class of DetNet flows c has two
buffers, namely buffer1 and buffer2. In a cycle (i) when buffer1
accumulates received packets from the node's reception ports, buffer2
transmits the already stored packets from the previous cycle (i-1).
In the next cycle (i+1), buffer2 stores the received packets and
buffer1 transmits the packets received in cycle (i). The duration of
each cycle is T_c.
The cycle time T_c must be carefully chosen; it needs to be large
enough to accommodate all the DetNet traffic, plus at least one
maximum packet (or fragment) size from lower priority queues, which
might be received within a cycle. Also, the value of T_c includes a
time interval, called dead time (DT), which is the sum of delays 1,
2, 3, and 4 defined in Figure 1. 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 in the same 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, and a cycle identification label can be added to the
packets.
The per-hop latency is determined by the cycle time T_c: a packet
transmitted from a node at a cycle (i) is transmitted from the next
node at cycle (i+1). Then, if the packet traverses h hops, the
maximum latency experienced by the packet is from the beginning of
cycle (i) to the end of cycle (i+h); also, the minimum latency is
from the end of cycle (i), before the DT, to the beginning of cycle
(i+h). Then, the maximum latency is:
(h+1) T_c
and the minimum latency is:
(h-1) T_c + DT.
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-flow
parameters in the CQF technique, per-hop configuration is not
required in the CQF forwarding nodes.
7. Example Application on DetNet IP Network
This section provides an example application of the timing model
presented in this document to control the admission of a DetNet flow
on a DetNet-enabled IP network. Consider Figure 5, taken from
Section 3 of [RFC8939], which shows a simple IP network:
* End system 1 implements Guaranteed Service [RFC2212], as in
Section 6.5, between itself and relay node 1.
* Sub-network 1 is a TSN network. The nodes in sub-network 1
implement credit-based shapers with asynchronous traffic shaping,
as in Section 6.4.
* Sub-network 2 is a TSN network. The nodes in sub-network 2
implement Cyclic Queuing and Forwarding with two buffers, as in
Section 6.6.
* 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 [RFC9023]).
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 RFC 8939
Consider a fully centralized control plane for the network of
Figure 5, as described in Section 3.2 of [DETNET-CONTROL-PLANE].
Suppose end system 1 wants to create a DetNet flow with a 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 [DETNET-CONTROL-PLANE]). 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 the entrance of the first
node in sub-network 2, and d3_p is 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
Sections 4.2.2 and 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 a new set of valid paths and redo the delay bound
computation or reject 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 of [DETNET-CONTROL-PLANE]).
8. Security Considerations
Detailed security considerations for DetNet are cataloged in
[RFC9055], 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], which 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 or change the behavior of some resources within
the boundary of the DetNet domain.
Latency bound calculations use parameters that reflect physical
quantities. If an attacker finds a way to change the physical
quantities, unknown to the control and management planes, the latency
calculations fail and may result in latency violation and/or
congestion losses. An example of such attacks is to make some
traffic sources under the control of the attacker send more traffic
than their assumed T-SPECs. This type of attack is typically avoided
by ingress conditioning at the edge of a DetNet domain. However, it
must be insured that such ingress conditioning is done per flow and
that the buffers are segregated such that if one flow exceeds its
T-SPEC, it does not cause buffer overflow for other flows.
Some queuing mechanisms require time synchronization and operate
correctly only if the time synchronization works correctly. In the
case of CQF, the correct alignments of cycles can fail if an attack
against time synchronization fools a node into having an incorrect
offset. Some of these attacks can be prevented by cryptographic
authentication as in Annex K of [IEEE1588] for the Precision Time
Protocol (PTP). However, the attacks that change the physical
latency of the links used by the time synchronization protocol are
still possible even if the time synchronization protocol is protected
by authentication and cryptography [DelayAttack]. Such attacks can
be detected only by their effects on latency bound violations and
congestion losses, which do not occur in normal DetNet operation.
9. IANA considerations
This document has no IANA actions.
10. References
10.1. Normative References
[IEEE8021Q]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Bridges and Bridged Networks", IEEE Std 802.1Q-
2018, DOI 10.1109/IEEESTD.2018.8403927, July 2018,
<https://ieeexplore.ieee.org/document/8403927>.
[RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212,
DOI 10.17487/RFC2212, September 1997,
<https://www.rfc-editor.org/info/rfc2212>.
[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>.
[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>.
[RFC7806] Baker, F. and R. Pan, "On Queuing, Marking, and Dropping",
RFC 7806, DOI 10.17487/RFC7806, April 2016,
<https://www.rfc-editor.org/info/rfc7806>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[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>.
[RFC9016] Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
Fedyk, "Flow and Service Information Model for
Deterministic Networking (DetNet)", RFC 9016,
DOI 10.17487/RFC9016, March 2021,
<https://www.rfc-editor.org/info/rfc9016>.
10.2. Informative References
[BennettDelay]
Bennett, J. C. R., Benson, K., Charny, A., Courtney, W.
F., and J.-Y. Le Boudec, "Delay jitter bounds and packet
scale rate guarantee for expedited forwarding",
DOI 10.1109/TNET.2002.801404, August 2002,
<https://dl.acm.org/citation.cfm?id=581870>.
[CharnyDelay]
Charny, A. and J.-Y. Le Boudec, "Delay Bounds in a Network
with Aggregate Scheduling", DOI 10.1007/3-540-39939-9_1,
September 2002, <https://link.springer.com/
chapter/10.1007/3-540-39939-9_1>.
[DelayAttack]
Barreto, S., Suresh, A., and J. L. Boudec, "Cyber-attack
on packet-based time synchronization protocols: The
undetectable Delay Box", DOI 10.1109/I2MTC.2016.7520408,
May 2016, <https://ieeexplore.ieee.org/document/7520408>.
[DETNET-CONTROL-PLANE]
Malis, A., Geng, A., Ed., Chen, M., Qin, F., and B. Varga,
"Deterministic Networking (DetNet) Controller Plane
Framework", Work in Progress, Internet-Draft, draft-ietf-
detnet-controller-plane-framework-02, 28 June 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
controller-plane-framework-02>.
[IEEE1588] IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Std 1588-2008, DOI 10.1109/IEEESTD.2008.4579760, July
2008, <https://ieeexplore.ieee.org/document/4579760>.
[IEEE8021Qcr]
IEEE 802.1, "802.1Qcr-2020 - IEEE Standard for Local and
Metropolitan Area Networks--Bridges and Bridged Networks
Amendment 34:Asynchronous Traffic Shaping", November 2020,
<https://ieeexplore.ieee.org/document/9253013>.
[IEEE8021TSN]
IEEE 802.1, "802.1 Time-Sensitive Networking (TSN) Task
Group", <https://1.ieee802.org/tsn/>.
[IEEE8023] IEEE, "IEEE Standard for Ethernet", IEEE Std 802.3-2018,
DOI 10.1109/IEEESTD.2018.8457469, August 2018,
<http://ieeexplore.ieee.org/document/8457469>.
[LeBoudecTheory]
Le Boudec, J.-Y., "A Theory of Traffic Regulators for
Deterministic Networks With Application to Interleaved
Regulators", DOI 10.1109/TNET.2018.2875191, November 2018,
<https://ieeexplore.ieee.org/document/8519761>.
[NetCalBook]
Le Boudec, J.-Y. and P. Thiran, "Network Calculus: A
Theory of Deterministic Queuing Systems for the Internet",
Springer Science & Business Media, vol. 2050, 2001,
<https://leboudec.github.io/netcal/latex/netCalBook.pdf>.
[PacketReorderingBounds]
Mohammadpour, E. and J.-Y. Le Boudec, "On Packet
Reordering in Time-Sensitive Networks",
DOI 10.1109/TNET.2021.3129590, December 2021,
<https://ieeexplore.ieee.org/document/9640523>.
[RFC2697] Heinanen, J. and R. Guerin, "A Single Rate Three Color
Marker", RFC 2697, DOI 10.17487/RFC2697, September 1999,
<https://www.rfc-editor.org/info/rfc2697>.
[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>.
[RFC9023] Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
"Deterministic Networking (DetNet) Data Plane: IP over
IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9023,
DOI 10.17487/RFC9023, June 2021,
<https://www.rfc-editor.org/info/rfc9023>.
[RFC9055] Grossman, E., Ed., Mizrahi, T., and A. Hacker,
"Deterministic Networking (DetNet) Security
Considerations", RFC 9055, DOI 10.17487/RFC9055, June
2021, <https://www.rfc-editor.org/info/rfc9055>.
[Sch8021Qbv]
Craciunas, S., Oliver, R., Chmelik, M., and W. Steiner,
"Scheduling Real-Time Communication in IEEE 802.1Qbv Time
Sensitive Networks", DOI 10.1145/2997465.2997470, October
2016, <https://dl.acm.org/doi/10.1145/2997465.2997470>.
[SpechtUBS]
Specht, J. and S. Samii, "Urgency-Based Scheduler for
Time-Sensitive Switched Ethernet Networks",
DOI 10.1109/ECRTS.2016.27, July 2016,
<https://ieeexplore.ieee.org/abstract/document/7557870>.
[ThomasTime]
Thomas, L. and J.-Y. Le Boudec, "On Time Synchronization
Issues in Time-Sensitive Networks with Regulators and
Nonideal Clocks", DOI 10.1145/3393691.339420, June 2020,
<https://dl.acm.org/doi/10.1145/3393691.3394206>.
[TSNwithATS]
Mohammadpour, E., Stai, E., Mohiuddin, M., and J.-Y. Le
Boudec, "Latency and Backlog Bounds in Time-Sensitive
Networking with Credit Based Shapers and Asynchronous
Traffic Shaping", DOI 10.1109/ITC30.2018.10053, September
2018, <https://ieeexplore.ieee.org/document/8493026>.
Acknowledgments
We would like to thank Lou Berger, Tony Przygienda, John Scudder,
Watson Ladd, Yoshifumi Nishida, Ralf Weber, Robert Sparks, Gyan
Mishra, Martin Duke, Éric Vyncke, Lars Eggert, Roman Danyliw, and
Paul Wouters for their useful feedback on this document.
Contributors
RFC 7322 limits the number of authors listed on the front page to a
maximum of 5. The editor wishes to thank and acknowledge the
following author for contributing text to this document:
Janos Farkas
Ericsson
Email: janos.farkas@ericsson.com
Authors' Addresses
Norman Finn
Huawei Technologies Co. Ltd
3101 Rio Way
Spring Valley, California 91977
United States of America
Phone: +1 925 980 6430
Email: nfinn@nfinnconsulting.com
Jean-Yves Le Boudec
EPFL
IC Station 14
CH-1015 Lausanne
Switzerland
Email: jean-yves.leboudec@epfl.ch
Ehsan Mohammadpour
EPFL
IC Station 14
CH-1015 Lausanne
Switzerland
Email: ehsan.mohammadpour@epfl.ch
Jiayi Zhang
Huawei Technologies Co. Ltd
Q27, No.156 Beiqing Road
Beijing
100095
China
Email: zhangjiayi11@huawei.com
Balázs Varga
Ericsson
Budapest
Konyves Kálmán krt. 11/B
1097
Hungary
Email: balazs.a.varga@ericsson.com