 1/draftietfdetnetboundedlatency00.txt 20191104 09:13:37.161627387 0800
+++ 2/draftietfdetnetboundedlatency01.txt 20191104 09:13:37.217628802 0800
@@ 1,25 +1,25 @@
DetNet N. Finn
InternetDraft Huawei Technologies Co. Ltd
Intended status: Informational JY. Le Boudec
Expires: January 25, 2020 E. Mohammadpour
+Expires: May 7, 2020 E. Mohammadpour
EPFL
J. Zhang
Huawei Technologies Co. Ltd
B. Varga
J. Farkas
Ericsson
 July 24, 2019
+ November 4, 2019
DetNet Bounded Latency
 draftietfdetnetboundedlatency00
+ draftietfdetnetboundedlatency01
Abstract
This document presents a timing model for Deterministic Networking
(DetNet), so that existing and future standards can achieve the
DetNet quality of service features of bounded latency and zero
congestion loss. It defines requirements for resource reservation
protocols or servers. It calls out queuing mechanisms, defined in
other documents, that can provide the DetNet quality of service.
@@ 31,21 +31,21 @@
InternetDrafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as InternetDrafts. The list of current Internet
Drafts is at https://datatracker.ietf.org/drafts/current/.
InternetDrafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use InternetDrafts as reference
material or to cite them other than as "work in progress."
 This InternetDraft will expire on January 25, 2020.
+ This InternetDraft will expire on May 7, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/licenseinfo) in effect on the date of
publication of this document. Please review these documents
@@ 57,43 +57,43 @@
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3
3. DetNet bounded latency model . . . . . . . . . . . . . . . . 4
3.1. Flow creation . . . . . . . . . . . . . . . . . . . . . . 4
3.1.1. Static flow latency calculation . . . . . . . . . . . 4
3.1.2. Dynamic flow latency calculation . . . . . . . . . . 5
3.2. Relay node model . . . . . . . . . . . . . . . . . . . . 6
 4. Computing Endtoend Latency Bounds . . . . . . . . . . . . . 8
+ 4. Computing Endtoend Delay Bounds . . . . . . . . . . . . . . 8
4.1. Nonqueuing delay bound . . . . . . . . . . . . . . . . . 8
 4.2. Queuing delay bound . . . . . . . . . . . . . . . . . . . 8
+ 4.2. Queuing delay bound . . . . . . . . . . . . . . . . . . . 9
4.2.1. Perflow queuing mechanisms . . . . . . . . . . . . . 9
4.2.2. Perclass queuing mechanisms . . . . . . . . . . . . 9
4.3. Ingress considerations . . . . . . . . . . . . . . . . . 10
4.4. Interspersed nonDetNet transit nodes . . . . . . . . . . 11
5. Achieving zero congestion loss . . . . . . . . . . . . . . . 11
 5.1. A General Formula . . . . . . . . . . . . . . . . . . . . 11
 6. Queuing techniques . . . . . . . . . . . . . . . . . . . . . 12
 6.1. Queuing data model . . . . . . . . . . . . . . . . . . . 12
 6.2. Preemption . . . . . . . . . . . . . . . . . . . . . . . 14
+ 6. Queuing techniques . . . . . . . . . . . . . . . . . . . . . 13
+ 6.1. Queuing data model . . . . . . . . . . . . . . . . . . . 13
+ 6.2. Preemption . . . . . . . . . . . . . . . . . . . . . . . 15
6.3. Timescheduled queuing . . . . . . . . . . . . . . . . . 15
6.4. CreditBased Shaper with Asynchronous Traffic Shaping . . 16
 6.4.1. Flow Admission . . . . . . . . . . . . . . . . . . . 19
+ 6.4.1. Delay Bound Calculation . . . . . . . . . . . . . . . 18
+ 6.4.2. Flow Admission . . . . . . . . . . . . . . . . . . . 19
6.5. IntServ . . . . . . . . . . . . . . . . . . . . . . . . . 20
 6.6. Cyclic Queuing and Forwarding . . . . . . . . . . . . . . 22
 6.6.1. CQF timing sequence . . . . . . . . . . . . . . . . . 23
+ 6.6. Cyclic Queuing and Forwarding . . . . . . . . . . . . . . 23
+ 6.6.1. CQF timing sequence . . . . . . . . . . . . . . . . . 24
6.6.2. CQF latency calculation . . . . . . . . . . . . . . . 24
 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
 7.1. Normative References . . . . . . . . . . . . . . . . . . 24
 7.2. Informative References . . . . . . . . . . . . . . . . . 25
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
+ 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
+ 7.1. Normative References . . . . . . . . . . . . . . . . . . 25
+ 7.2. Informative References . . . . . . . . . . . . . . . . . 26
+ Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
The ability for IETF Deterministic Networking (DetNet) or IEEE 802.1
TimeSensitive Networking (TSN, [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/TSN 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
@@ 167,23 +167,24 @@
6. Assuming that the resources are available, commit those resources
to the flow. This may or may not require adjusting the
parameters that control the filtering and/or queuing mechanisms
at each hop along the flow's path.
This paradigm can be implemented using peertopeer protocols or
using a central server. In some situations, a lack of resources can
require backtracking and recursing through this list.
 Issues such as unprovisioning 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.
+ Issues such as unprovisioning 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 flow latency calculation
The static problem:
Given a network and a set of DetNet flows, compute an endto
end latency bound (if computable) for each 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
@@ 221,28 +222,35 @@
particularly buffer space, required in each DetNet transit
node to achieve zero congestion loss.
This calculation is dynamic, in the sense that flows can be added or
deleted at any time, with a minimum of computation effort, and
without affecting the guarantees already given to other flows.
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 flow. Other queuing methods
 (e.g., transmission selection by strict priority), make this
 calculation impossible, because the worst case for one flow cannot be
 computed without complete knowledge of all other flows. Other
 queuing methods (e.g. the creditbased shaper defined in [IEEE8021Q]
 section 8.6.8.2) can be used for dynamic flow creation, but yield
 poorer latency and buffer space guarantees than when that same
 queuing method is used for static flow creation (Section 3.1.1).
+ make independent calculations for each flow. [[E:The rest of this
+ paragraph should be changed.]] Other queuing methods (e.g.,
+ transmission selection by strict priority), make this calculation
+ impossible, because the worst case for one flow cannot be computed
+ without complete knowledge of all other flows. Other queuing methods
+ (e.g. the creditbased shaper defined in [IEEE8021Q] section 8.6.8.2)
+ can be used for dynamic flow creation, but yield poorer latency and
+ buffer space guarantees than when that same queuing method is used
+ for static flow creation (Section 3.1.1).
+
+ [[E:proposed replacement: Some other queuing methods (e.g. strict
+ priority with the creditbased shaper defined in [IEEE8021Q] section
+ 8.6.8.2) can be used for dynamic flow creation, but yield poorer
+ latency and buffer space guarantees than when that same queuing
+ method is used for static 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 perhop latency experienced by a packet
passing through a DetNet transit node, in terms that are suitable for
computing both hopbyhop latency and perhop buffer requirements.
DetNet transit node A DetNet transit node B
@@ 257,25 +265,25 @@
<><><><><><><><><><
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: Preemption delay 6: Queuing delay.
Figure 1: Timing model for DetNet or TSN
In Figure 1, we see two DetNet transit nodes (typically, bridges or
routers), with a wired link between them. In this model, the only
 queues 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.
+ 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
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. But, in many
implementations, the queuing mechanism in a forwarding ASIC is
separated from a multiport MAC/PHY, in a second ASIC, by a
multiplexed connection. This causes variations in the output
delay that are hard for the forwarding node to predict or control.
@@ 338,80 +346,85 @@
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.
o Variations in processing delay (4) require additional output
buffers in the queues of that same DetNet transit node. Depending
on the details of the queueing subsystem delay (6) calculations,
these variations need not be visible outside the DetNet transit
node.
4. Computing Endtoend Latency Bounds
+4. Computing Endtoend Delay Bounds
4.1. Nonqueuing delay bound
 Endtoend 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 worstcase endtoend delay is less than the
 sum of the perhop worstcase delays. An endtoend latency bound
 for one DetNet flow can be computed as
+ Endtoend delay 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 endtoend delay bound is less than the sum
+ of the perhop delay bounds. An endtoend delay bound for one
+ DetNet flow can be computed as
 end_to_end_latency_bound = non_queuing_latency + queuing_latency
+ 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 hth hop along the path of this DetNet flow, obtain an upper
 bound perhop_non_queuing_latency[h] on the sum of delays 1,2,3,4 of
 Figure 1. These upperbounds are expected to depend on the specific
 technology of the DetNet transit node at the hth hop but not on the
 TSPEC of this DetNet flow. Then set non_queuing_latency = the sum
 of perhop_non_queuing_latency[h] over all hops h.
+ The two terms in the above formula are computed as follows.
4.2. Queuing delay bound
+ First, at the hth hop along the path of this DetNet flow, obtain an
+ upperbound perhop_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
+ expected to depend on the specific technology of the DetNet transit
+ node at the hth hop but not on the TSPEC of this DetNet flow. Then
+ set non_queuing_delay_bound = the sum of per
+ hop_non_queuing_delay_bound[h] over all hops h.
 Second, compute queuing_latency as an upper bound to the sum of the
 queuing delays along the path. The value of queuing_latency depends
 on the TSPEC of this flow and possibly of other flows in the
+ 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 TSPEC of this flow and possibly of other flows in the
network, as well as the specifics of the queuing mechanisms deployed
 along the path of this flow.
+ along the path of this flow. The computation of queuing_delay_bound
+ is described in Section 4.2 as a separate section.
 For several queuing mechanisms, queuing_latency is less than the sum
 of upper bounds on the queuing delays (5,6) at every hop. This
+4.2. Queuing delay bound
+
+ For several queuing mechanisms, queuing_delay_bound is less than the
+ sum of upper bounds on the queuing delays (5,6) at every hop. This
occurs with (1) perflow queuing, and (2) perclass queuing with
regulators, as explained in Section 4.2.1, Section 4.2.2, and
Section 6.
For other queuing mechanisms the only available value of
 queuing_latency is the sum of the perhop queuing delay bounds. In
 such cases, the computation of perhop queuing delay bounds must
+ queuing_delay_bound is the sum of the perhop queuing delay bounds.
+ In such cases, the computation of perhop queuing delay bounds must
account for the fact that the TSPEC 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.
4.2.1. Perflow 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 delay. For every flow the pernode delay bound as well as
 endtoend delay bound can be computed from the traffic specification
 of this flow at its source and from the values of rates and latencies
 at all nodes along its path. Details of calculation for IntServ are
 described in Section 6.5.
+ rate and a latency. For every flow, a pernode delay bound as well
+ as an endtoend delay bound can be computed from the traffic
+ specification of this flow at its source and from the values of rates
+ and latencies at all nodes along its path. The perflow queuing is
+ used in IntServ. Details of calculation for IntServ are described in
+ Section 6.5.
4.2.2. Perclass queuing mechanisms
With such mechanisms, the flows that have the same class share the
same queue. A practical example is the creditbased shaper defined
in section 8.6.8.2 of [IEEE8021Q]. One key issue in this context is
how to deal with the burstiness cascade: individual flows that share
a resource dedicated to a class may see their burstiness increase,
which may in turn cause increased burstiness to other flows
 downstream of this resource. Computing latency upper bounds for such
+ 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,
they depend on the complete configuration, and must be recomputed
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
hop. This can be done with perflow regulators (e.g. leaky bucket
shapers), but this requires perflow queuing and defeats the purpose
of perclass queuing. An alternative is the interleaved regulator,
which reshapes individual flows without perflow queuing
@@ 424,99 +437,98 @@
when an interleaved regulator is appended to a FIFO subsystem, it
does not increase the worstcase delay of the latter.
Figure 2 shows an example of a network with 5 nodes, perclass
queuing mechanism and interleaved regulators as in Figure 1. An end
toend delay bound for 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 aggregate response time
 of queuing subsystem in node i and interleaved regulator of node j,
 and S4 is a bound on the response time of the queuing subsystem in
 node 4 for flow f. In fact, using the delay definitions in
 Section 3.2, Cij is a bound on sum of the delays 1,2,3,6 of node i
 and 4,5 of node j. Similarly, S4 is a bound on sum of the delays
 1,2,3,6 of node 4. A practical example of queuing model and delay
 calculation is presented Section 6.4.
+ 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 flow f. In
+ fact, using the delay definitions in Section 3.2, Cij is a bound on
+ sum of the delays 1,2,3,6 of node i and 4,5 of node j. Similarly, S4
+ is a bound on sum of the delays 1,2,3,6 of node 4. A practical
+ example of queuing model and delay calculation is presented
+ Section 6.4.
f
>
++ ++ ++ ++ ++
 1  2  3  4  5 
++ ++ ++ ++ ++
\__C12_/\__C23_/\__C34_/\_S4_/
 Figure 2: Endtoend latency computation example
+ Figure 2: Endtoend delay computation example
REMARK: The endtoend delay bound calculation provided here gives a
much better upper bound in comparison with endtoend delay bound
computation by adding the delay bounds of each node in the path of a
flow [TSNwithATS].
4.3. Ingress considerations
A sender can be a DetNet node which uses exactly the same queuing
 methods as its adjacent DetNet transit node, so that the latency and
 buffer 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
 flow may be necessary at the ingress DetNet transit node.
+ methods as its adjacent DetNet transit node, so that the delay 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 flow may be necessary at the ingress DetNet
+ transit node.
This ingress conditioning typically consists of a FIFO with an output
regulator that is compatible with the queuing employed by the DetNet
transit node on its output port(s). For some queuing methods, simply
requires added extra buffer space in the queuing subsystem. Ingress
conditioning requirements for different queuing methods are mentioned
in the sections, below, describing those queuing methods.
4.4. Interspersed nonDetNet transit nodes
It is sometimes desirable to build a network that has both DetNet
aware transit nodes and DetNet nonaware transit nodes, and for a
DetNet flow to traverse an island of nonDetNet transit nodes, while
 still allowing the network to offer latency and congestion loss
+ still allowing the network to offer delay and congestion loss
guarantees. This is possible under certain conditions.
In general, when passing through a nonDetNet island, the island
causes delay variation in excess of what would be caused by DetNet
nodes. That is, the DetNet flow is "lumpier" after traversing the
 nonDetNet island. DetNet guarantees for latency and buffer
+ nonDetNet 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 nonDetNet island must be
bounded and calculable.
2. An ingress conditioning function (Section 4.3) may be required at
the reentry to the DetNetaware domain. This will, at least,
require some extra buffering to accommodate the additional delay
 variation, and thus further increases the worstcase latency.
+ variation, and thus further increases the delay 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 nonDetNet island is typically
the most difficult to achieve. Without such a bound, it is obvious
that DetNet cannot deliver its guarantees, so a nonDetNet 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 deterministic networking seeks to
avoid.
5.1. A General Formula

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.
@@ 524,43 +536,47 @@
The backlog bound is counted in data units (bytes, or words of
multiple bytes) that are relevant for buffer allocation. For every
class we need one buffer space for the packet in transmission, plus
space for the packets that are waiting to be selected for output.
Excluding transmission and preemption times, the packets are waiting
in the queue since reception of the last bit, for a duration equal to
the processing delay (4) plus the queuing delays (5,6).
Let
 o nb_classes be the number of classes of traffic that may use this
 output port

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
total_in_rate is in data units (e.g. bytes) per second.
o nb_input_ports be the number input ports that send traffic of any
class to this output port
o max_packet_length be the maximum packet size for packets of any
class that may be sent to this output port. This is counted in
data units.
 o max_delay45 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
any class at this output port.
Then a bound on the backlog of traffic of all classes in the queue at
this output port is
+ [[E: The formula is not right; why do we need nb_classes to compute
+ backlog bound?]]
+
backlog_bound = ( nb_classes + nb_input_ports ) *
 max_packet_length + total_in_rate* max_delay45
+ max_packet_length + total_in_rate* max_delay456
+
+ [[E: proposed general backlog bound:]]
+ backlog_bound = nb_input_ports * max_packet_length +
+ total_in_rate* max_delay456
6. Queuing techniques
6.1. Queuing data model
Sophisticated queuing mechanisms are available in Layer 3 (L3, see,
e.g., [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 not
the province solely of bridges; they are an essential part of any
@@ 663,23 +679,23 @@
6.3. Timescheduled queuing
In [IEEE8021Q], the notion of timescheduling queue gates is
described in section 8.6.8.4. Below every output queue (the lower
row of queues in Figure 3) is a gate that permits or denies the queue
to present data for transmission selection. The gates are controlled
by a rotating schedule that can be locked to a clock that is
synchronized with other DetNet transit nodes. The DetNet class of
service can be supplied by queuing mechanisms based on time, rather
 than the regulator model in Figure 3. Generally speacking, this
 timeaware scheduling can be used as a layer 2 time division
 multiplexing (TDM) technique.
+ than the regulator model in Figure 3. Generally speaking, this time
+ aware scheduling can be used as a layer 2 time division multiplexing
+ (TDM) technique.
Consider the static configuration of a deterministic network. To
provide endtoend latency guaranteed service, network nodes can
support timebased behavior, which is determined by gate control list
(GCL). GCL defines the gate operation, in open or closed state, with
associated timing for each traffic class queue. A time slice with
gate state "open" is called transmission window. The timebased
traffic scheduling must be coordinated among the DetNet transit nodes
along the path from sender to receiver, to control the transmission
of timesensitive traffic.
@@ 709,42 +725,45 @@
synchronized network and coordinated GCL configuration. Synthesis of
GCL on multiple nodes in network is a scheduling problem considering
all TSN/DetNet flows traversing the network, which is a non
deterministic polynomialtime hard (NPhard) problem. Also, at this
writing, scheduled traffic service supports no more than eight
traffic classes, typically using up to seven priority classes and at
least one best effort class.
6.4. CreditBased Shaper with Asynchronous Traffic Shaping
 Consider a network with a set of nodes (DetNet transit nodes and
 hosts) along with a set of flows between hosts. Hosts are sources or
 destinations of flows. There are four types of flows, namely,
 controldata traffic (CDT), class A, class B, and best effort (BE) in
 decreasing order of priority. Flows of classes A and B are together
 referred to AVB flows. It is assumed a subset of TSN functions as
 described next.
+ In the cosidered queuing model, there are four types of flows,
+ namely, controldata traffic (CDT), class A, class B, and best effort
+ (BE) in decreasing order of priority. Flows of classes A and B are
+ together referred to AVB flows. This model is a subset of Time
+ Sensitive Networking as described next.
 It is also assumed that contention occurs only at the output port of
 a TSN node. Each node output port performs perclass scheduling with
 eight classes: one for CDT, one for class A traffic, one for class B
 traffic, and five for BE traffic denoted as BE0BE4 (according to TSN
 standard). In addition, each node output port also performs perflow
 regulation for AVB flows using an interleaved regulator (IR), called
 Asynchronous Traffic Shaper (ATS) in TSN. Thus, at each output port
 of a node, there is one interleaved regulator perinput port and per
 class. 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 class based FIFO system (CBFS) [TSNwithATS].
+ Based on the timing model described in Figure 1, the contention
+ occurs only at the output port of a relay node; therefore, the focus
+ of the rest of this subsection is on the regulator and queuing
+ subsystem in the output port of a relay node. The output port
+ performs perclass scheduling with eight classes (queuing
+ subsystems): one for CDT, one for class A traffic, one for class B
+ traffic, and five for BE traffic denoted as BE0BE4. The queuing
+ policy for each queuing subsystem is FIFO. In addition, each node
+ output port also performs perflow regulation for AVB flows using an
+ interleaved regulator (IR), called Asynchronous Traffic Shaper
+ [IEEE8021Qcr]. Thus, at each output port of a node, there is one
+ interleaved regulator perinput port and perclass; 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 queuing
+ subsytem; there is no regulator for such classes.
++ ++ ++ ++
       
IR IR IR IR
       
+++XXX+++ +++XXX+++
   
   
++ +vXXXv+ +vXXXv+ ++ ++ ++ ++ ++
      Class Class Class Class Class
@@ 755,117 +774,121 @@
 +v+ +v+     
 CBS CBS     
 +++ +++     
       
+vvvvVvvv+
 Strict Priority selection 
+++

V
 Figure 4: Architecture of a TSN node output port with interleaved
 regulators (IRs)
+ Figure 4: The architecture of an output port inside a relay node with
+ interleaved regulators (IRs) and creditbased shaper (CBS)
 The CBFS includes two CreditBased Shaper (CBS) subsystems, one for
 each class A and B. The CBS serves a packet from a class according
+ Each of the queuing subsystems for class A and B, contains Credit
+ 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
or B increases based on the idle slope, and decreases based on the
 send slope, both of which are parameters of the CBS. The CDT and
 BE0BE4 flows in the CBFS are served by separate FIFO 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 nonpreemptive. Guarantees for AVB traffic can be
 provided only if CDT traffic is bounded; it is assumed that the CDT
 traffic has leaky bucket arrival curve with two parameters r_h as
 rate and b_h as bucket size, i.e., the amount of bits entering a node
 within a time interval t is bounded by r_h t + b_h.
+ send slope, both of which are parameters of the CBS (Section 8.6.8.2
+ of [IEEE8021Q]). The CDT and BE0BE4 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 nonpreemptive.
+ Guarantees for AVB traffic can be provided only if CDT traffic is
+ bounded; it is assumed that the CDT traffic has leaky bucket arrival
+ curve with two parameters r_h as rate and b_h as bucket size, i.e.,
+ 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 AVB flows are also regulated at
 their source according to leaky bucket arrival curve. At the source
 hosts, the traffic satisfies its regulation constraint, i.e. the
 delay due to interleaved regulator at hosts is ignored.
+ their source according to leaky bucket arrival curve. At the source,
+ the traffic satisfies its regulation constraint, i.e. the delay due
+ to interleaved regulator at 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. A delay bound
 of CBFS for an AVB flow f of class A or B can be computed if the
 following condition holds:
+ source and at all DetNet transit nodes along its path.
 sum of leaky bucket rates of all flows of this class at this node
 <= R, where R is given below for every class.
+6.4.1. Delay Bound Calculation
 If the condition holds, the delay bound is:
+ 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
+ holds:
 d_f = T + (b_tL_min_f)/R  L_min_f/c
+ sum of leaky bucket rates of all flows of this class at this
+ transit node <= R, where R is given below for every class.
 where L_min_f is the minimum packet length of flow f; c is the output
 link transmission rate; b_t is the sum of the b term (bucket size)
 for all the flows having the same class as flow f at this node.
 Parameters R and T are calculated as follows for class A and class B,
 separately:
+ If the condition holds, the delay bounds for a flow of class X (A or
+ B) is d_X and calculated as:
 If f is of class A:
+ d_X = T_X + (b_t_XL_min_X)/R_X  L_min_X/c
 R = I_A (cr_h)/ c
+ where L_min_X is the minimum packet lengths of class X (A or B); c is
+ the output link transmission rate; 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 class B, separately:
 T = L_nA + b_h + r_h L_n/c)/(cr_h)
+ If the flow is of class A:
+
+ R_A = I_A (cr_h)/ c
+
+ T_A = L_nA + b_h + r_h L_n/c)/(cr_h)
where 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.
 If f is of class B:
+ If the flow is of class B:
 R = I_B (cr_h)/ c
+ R_B = I_B (cr_h)/ c
 T = (L_BE + L_A + L_nA I_A/(c_hI_A) + b_h + r_h L_n/c)/(cr_h)
+ T_B = (L_BE + L_A + L_nA I_A/(c_hI_A) + b_h + r_h L_n/c)/(cr_h)
where L_A is the maximum packet length of class A; L_BE is the
maximum packet length of class BE.
 Then, an endtoend delay bound is calculated by the formula
 Section 4.2.2, where for Cij:

 Cij = max(d_f')
+ Then, an endtoend delay bound of class X (A or B)is calculated by
+ the formula Section 4.2.2, where for Cij:
 where f' is any flow that shares the same CBFS class with flow f at
 node i and the same interleaved regulator as flow f at node j.
+ Cij = d_X
More information of delay analysis in such a DetNet transit node is
described in [TSNwithATS].
6.4.1. Flow Admission
+6.4.2. Flow Admission
 The delay calculation requires some information about each 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 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) should be
 known. To admit a flow/flows, their delay requirements should 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 should be guaranteed. Thus,
+ The delay bound calculation requires some information about each
+ 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
+ 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)
+ should be known. To admit a flow/flows, their delay requirements
+ should 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 should be
+ guaranteed. Thus,
The static admission control:
The leaky bucket parameters of all flows are known,
 therefore, for each flow a delay bound can be calculated.
+ therefore, for each flow f, a delay bound can be calculated.
The computed delay bound for every flow should not be more
than its delay requirement. Moreover, the sum of the rate of
each flow (r_f) should 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 to every node and
class A or B, static value for rate (R) and maximum
burstiness (b_t). In addition, for every node and every
class A and B, two counters are maintained:
R_acc is equal to the sum of the leakybucket rates of all
flows of this class already admitted at this node; At all
times, we must have:
R_acc <=R, (Eq. 1)
@@ 888,24 +911,30 @@
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, b_t affects the delay bound and
the buffer requirement. R must satisfy the constraints given in
Annex L.1 of [IEEE8021Q].
6.5. IntServ
Integrated service (IntServ) is an architecture that specifies the
 elements to guarantee quality of service (QoS) on networks. To
 satisfied guaranteed service, a flow must conform to a traffic
 specification (Tspec), and reservation is made along a path, only if
 routers are able to guarantee the required bandwidth and buffer.
+ elements to guarantee quality of service (QoS) on networks. [[E: The
+ rest of this paragraph is better not to be placed here; these should
+ be mentioned (is mentioned) in the introduction.]] To satisfied
+ guaranteed service, a flow must conform to a traffic specification
+ (Tspec), and reservation is made along a path, only if routers are
+ able to guarantee the required bandwidth and buffer.
+
+ [[E: The information about arrival and service curves can be shorter
+ with less detail. I put a proposed text after description of
+ these.]]
Consider the traffic model which conforms to token bucket regulator
(r, b), with
o Token bucket depth (b).
o Token bucket rate (r).
The traffic specification can be described as an arrival curve:
@@ 915,41 +944,52 @@
the number of bit for the flow is limited by alpha(t) = b + rt.
If resource reservation on a path is applied, IntServ model of a
router can be described as a ratelatency service curve beta(t).
beta(t) = max(0, R(tT))
It describes that bits might have to wait up to T before being served
with a rate greater or equal to R.
 It should be noted that, the guaranteed service rate R is a share of
 link's bandwidth. The choice of R is related to the specification of
 flows which will transmit on this node. For example, in strict
 priority policy, considering a flow with priority j, its share of
 bandwidth may be R=csum(r_i), i 0.7 1 (units of Tc) 2 3
+ 0 time > 0.7 1 (units of T_c) 2 3
DetNet transit node A out port 1
 a <DT> b  c  d
+++++
\_____ \_____
 \_____ \_____ queuetoqueue delay = 1.3 Tc
+ \_____ \_____ queuetoqueue delay = 1.3 T_c
\_____ \_____
\_____ \_____ DetNet transit node B
\_ \_ queue assignment, in
  <DT> port 2 to out 3 
+++++
0.3 time> 1.3 2.0 2.3 3.3
window to transfer
to buffer c > VVVVVVVVVVVV
if dead time not window to transfer
@@ 1030,23 +1070,24 @@
3. The output queues on port 2 of node B.
In this figure, the output ports on the two nodes are synchronized,
and a new buffer starts transmitting at each tick, shown as 0, 1, 2,
... The output times shown for timelines 1 and 3 are the times at
which packets are selected for output, which is the start point of
the output time (1) of Figure 1. The queue assignments times on
timeline 3 take place at the beginning of the queuing delay (6) of
Figure 1. Timebased CQF, as described here, does not require any
 regulator queues. In the shown in the figure, the total time for
 delays 1 through 6 of Figure 1 is 1.3Tc. Of course, any value is
 possible.
+ regulator queues. In the shown in the figure, the total time [[E:
+ what is meant by total time? Does it mean a delay bound is 1.3
+ T_C?]] for delays (1) through (6) of Figure 1, is 1.3T_c. Of course,
+ any value is possible.
6.6.1. CQF timing sequence
In general, as shown in Figure 6, the windows for buffer assignment
do not align perfectly with the windows for buffer transmission. The
input gates (the center timeline in Figure 6) must switch from using
one buffer to using another buffer in sync with the (delayed)
received data, at times offset by the dead time from the output
buffer switching (the bottom timeline in Figure 6).
@@ 1066,23 +1107,23 @@
from node A buffer a into node B buffer d between the times 1.3 and
2.3 in Figure 6. Buffer b starts outputting at time = 2.0, while
buffer d is filling. Thus, three buffers are in use, one filling,
one waiting, and one emptying.
6.6.2. CQF latency calculation
The perhop latency is trivially determined by the wire delay and the
queuing delay. Since the wire delay is either absorbed into the
queueing delay (dead time is small and two buffers are used) or
 padded out to a whole cycle time Tc (three buffers are used) the per
 hop latency is always an integral number of cycle times Tc, with a
 latency variation at the output of the final hop of Tc.
+ padded out to a whole cycle time T_c (three buffers are used) the
+ perhop latency is always an integral number of cycle times T_c, with
+ a latency variation at the output of the final hop of T_c.
Ingress conditioning (Section 4.3) may be required if the source of a
DetNet flow does not, itself, employ CQF.
Note that there are no perflow parameters in the CQF technique.
Therefore, there is no requirement for perhop configuration when a
new DetNet flow is added to a network, except perhaps for ingress
checks to see that the transmitter does not exceed the contracted
bandwidth.