wdiff draft-ietf-rmcat-wireless-tests-08.txt draft-ietf-rmcat-wireless-tests-09.txt

Network Working Group Z. Sarker
Internet-Draft I. Johansson
Intended status: Informational Ericsson AB
Expires: January 6, August 30, 2020 X. Zhu
J. Fu
W. Tan
M. Ramalho
Cisco Systems
July 5, 2019
M. Ramalho
AcousticComms
February 27, 2020

Evaluation Test Cases for Interactive Real-Time Media over Wireless
Networks
draft-ietf-rmcat-wireless-tests-08
draft-ietf-rmcat-wireless-tests-09

Abstract

The Real-time Transport Protocol (RTP) is a common transport choice
for interactive multimedia communication applications. The
performance of such these applications typically depends on a well-
functioning congestion control algorithm. To ensure a seamless and
robust user experience, a well-designed RTP-based congestion control
algorithm should work well across all access network types. This
document describes test cases for evaluating performances of such
candidate congestion control algorithms over LTE cellular and Wi-Fi
networks.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on January 6, August 30, 2020.

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(https://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Cellular Network Specific Test Cases . . . . . . . . . . . . 3
3.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6
3.1.1. Network Connection . . . . . . . . . . . . . . . . . 6
3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7
3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 9
3.2.1. Network connection . . . . . . . . . . . . . . . . . 9
3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9
3.3. Desired Evaluation Metrics for cellular test cases . . . 10
4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10
4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12
4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12
4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13
4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14
4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15
4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15
4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15
4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15
4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17
4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18
4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19
4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19
4.3.2. Effects Effect of Legacy 802.11b Devices . heterogeneous link rates . . . . . . . . . 19
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
7.
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8.
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
9.
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1.
8.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2.
8.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22

1. Introduction

Wireless networks (both cellular and Wi-Fi [IEEE802.11]) are an
integral part of the Internet. Mobile devices connected to the
wireless networks account for an and increasingly more significant
portion part of the media traffic over the Internet. Application
Typical application scenarios range for interactive multimedia
communication over wireless include from video conferencing calls in
a bus or train to as well as live media consumption by someone on a living room couch. streaming at home. It is well
known that the characteristics and technical challenges for
supporting multimedia services over wireless are very different from
those of providing the same service over a wired network. Even
though Although
the basic test cases for evaluating RTP-based congestion control
schemes as defined in [I-D.ietf-rmcat-eval-test] have
covered many common effects of the network impairments common to both wired and wireless
networks, there for evaluating
RTP-based congestion control schemes, they remain to be tested over
characteristics and dynamics unique to a given wireless environment.
For example, in LTE cellular networks, the base station maintains
individual queues per radio bearer per user hence it leads to a
different nature of interactions between traffic flows of different
users. This contrasts with the wired networks, network setting where traffic
flows from all users share the same queue. Furthermore, user
mobility patterns in a cellular network differ from those in a Wi-Fi
network. Therefore, it is important to evaluate the performance of
proposed candidate RTP-based congestion control solutions over
cellular mobile networks and over Wi-Fi networks respectively.

RMCAT evaluation criteria document

The draft [I-D.ietf-rmcat-eval-criteria] provides the guideline for
evaluating candidate algorithms and recognizes the importance of
testing over wireless access networks. However, it does not describe
any specific test cases for performance evaluation of candidate
algorithms. This document describes test cases specifically
targeting cellular networks such as LTE networks and Wi-Fi networks.

2. Terminologies

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. Cellular Network Specific Test Cases

A cellular environment is more complicated than its wireline
counterpart since it seeks to provide services in the context of
variable available bandwidth, location dependencies and user
mobilities at different speeds. In a cellular network, the user may
reach the cell edge which may lead to a significant amount of
retransmissions to deliver the data from the base station to the
destination and vice versa. These network links or radio links will often act as a
bottleneck for the rest of the network and will eventually lead to
excessive delays or packet drops. An efficient retransmission or
link adaptation mechanism can reduce the packet loss probability but
there will still be remain some packet losses and delay variations. Moreover,
with increased cell load or handover to a congested cell, congestion
in the transport network will become even worse. Besides, there are
exist certain characteristics which make that distinguish the cellular network different
from and more challenging than other types
of wireless access networks such as Wi-Fi and wired network. Wi-Fi. In a cellular
network --

o The bottleneck is often a shared link with relatively few users.

* The cost per bit over the shared link varies over time and is
different for different users.

* Leftover/unused resource resources can be consumed by other greedy
users.

o Queues are always per radio bearer hence each user can have many
of
such queues.

o Users can experience both Inter and Intra Radio Access Technology
(RAT) handovers (see [HO-def-3GPP] for the definition of
"handover").

o Handover between cells or change of serving cells (as described in
[HO-LTE-3GPP] and [HO-UMTS-3GPP]) might cause user plane
interruptions which can lead to bursts of packet losses, delay
and/or jitter. The exact behavior depends on the type of radio
bearer. Typically, the default best-effort bearers do not
generate packet loss, instead, packets are queued up and
transmitted once the handover is completed.

o The network part decides how much the user can transmit.

o The cellular network has variable link capacity per user user.

* Can It can vary as fast as a period of milliseconds.

* Depends It depends on many factors (such as distance, speed,
interference, different flows).

* Uses It uses complex and smart link adaptation which makes the link
behavior ever more dynamic.

* The scheduling priority depends on the estimated throughput.

o Both Quality of Service (QoS) and non-QoS radio bearers can be
used.

Hence, a real-time communication application operating in such over a
cellular network needs to cope with a shared bottleneck link and
variable link capacity, events like handover, non-congestion related
loss, abrupt changes in bandwidth (both short term and long term) due
to handover, network load and bad radio coverage. Even though 3GPP
define
has defined QoS bearers [QoS-3GPP] to ensure high-quality user
experience,
adaptive it is still preferable for real-time applications are desired. to
behave in an adaptive manner.

Different mobile operators deploy their own cellular network networks with
their own set of network functionalities and policies. Usually, a
mobile operator network includes 2G, EDGE, 3G and 4G radio access
technologies. Looking at the specifications of such radio
technologies it is evident that only 3G and 4G the more recent radio
technologies can support the high bandwidth requirements from real-time real-
time interactive video applications. The future real-time
interactive application will impose even greater demand on cellular
network performance which makes 4G (and beyond beyond) radio technologies) technologies
more suitable access
technology for such genre of application.

The key factors to define in defining test cases for cellular networks are are:

o Shared and varying link capacity

o Mobility

o Handover

However, for cellular networks, it is very hard to separate such
events from one another as these events factors are heavily related. Hence typically highly correlated in a cellular
network. Therefore, instead of devising separate test cases for all those
individual important events, we have divided the test case into two
categories. It should be noted that the goal of the following test
cases is to evaluate the performance of candidate algorithms over the
radio interface of the cellular network. Hence it is assumed that
the radio interface is the bottleneck link between the communicating
peers and that the core network does not add introduce any extra
congestion in along the path. Also, Consequently, this draft has kept as out
of scope the combination of multiple access technologies such as one user has LTE
connection involving
both cellular and another has Wi-Fi connection is kept out of the scope
of users. In this document. However, later those additional scenarios can also
be added in this list of test cases. While defining latter case the shared
bottleneck is likely at the wired backhaul link. These test cases
we assumed
further assume a typical real-time telephony scenario over cellular
networks where one real-time real-
time session consists of one voice stream and one video stream.

Even though it is possible to carry out tests over operational LTE
(and 5G) networks,
cellular networks (e.g., LTE/5G), and actually such tests are already
available today, these tests cannot in the general case be carried out in a
deterministic fashion or to ensure repeatability. The main reason is
that these networks are in the control of controlled by cellular operators and there
exist various amounts of competing traffic in the same cell(s). In
practice, it is only in underground mines that one can carry out near
deterministic testing. Even there, it is not guaranteed either as
workers in the mines may carry with them their personal mobile
phones. Furthermore, the underground mining setting may not reflect
typical usage patterns in an urban setting. We, therefore, recommend
that an LTE a cellular network simulator is used for the test cases defined
in this document, for example --- NS-3 -- the LTE simulator [LTE-simulator]. in [NS-3].

3.1. Varying Network Load

The goal of this test is to evaluate the performance of the candidate
congestion control algorithm under varying network load. The network
load variation is created by adding and removing network users a.k.a.
User Equipments (UEs) during the simulation. In this test case, each
of the
user/UE in the media session is an RMCAT compliant endpoint.
The arrival of users follows endpoint following RTP-based
congestion control. User arrivals follow a Poisson distribution
proportional to the length of the call so as call, to keep the number of users
per cell fairly constant during the evaluation period. At the
beginning of the simulation, there should be enough time to warm-up
the network. This is to avoid running the evaluation in an empty
network where network nodes are having empty buffers, low
interference at the beginning of the simulation. This network
initialization period is
therefore should be excluded from the evaluation period.

This test case also includes user mobility and some competing
traffic. The latter includes both the same kind types of flows (with same
adaptation algorithms) and different kind types of flows (with different
services and congestion control schemes). The investigated
congestion control algorithms should show maximum possible network
utilization and stability in terms of rate variations, lowest
possible end to end frame latency, network latency and Packet Loss
Rate (PLR) at different cell load level.

3.1.1. Network Connection

Each mobile user is connected to a fixed user. The connection
between the mobile user and fixed user consists of an LTE a cellular radio
access, an Evolved Packet Core (EPC) and an Internet connection. The
mobile user is connected to the EPC using LTE cellular radio access
technology which is further connected to the Internet. The At the other
end, the fixed user is connected to the Internet via wired connection
with sufficiently high bandwidth, for instance, 10 Gbps, so that the
system bottleneck is resource-
limited on the wireless cellular radio access interface. The
wired connection to the
Internet in this setup does not introduce any network
impairments to the test; it only adds 10 ms of one-way propagation
delay.

The path from the fixed user to the mobile users is defined as
"Downlink" and the path from the mobile users to the fixed user is
defined as "Uplink". We assume that only uplink or downlink is
congested for mobile users. Hence, we recommend that the uplink and
downlink simulations are run separately.

uplink
++))) +-------------------------->
++-+ ((o))
| | / \ +-------+ +------+ +---+
+--+ / \----+ +-----+ +----+ |
/ \ +-------+ +------+ +---+
UE BS EPC Internet fixed
<--------------------------+
downlink

Figure 1: Simulation Topology

3.1.2. Simulation Setup

The values enclosed within "[ ]" for the following simulation
attributes follow the same notion as in [I-D.ietf-rmcat-eval-test].
The desired simulation setup is as follows --

1. Radio environment:

A. Deployment and propagation model: 3GPP case 1 [Deployment] (see
[HO-deploy-3GPP])

B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D]

C. Mobility: [3km/h, 30km/h]

D. Transmission bandwidth: 10Mhz

E. Number of cells: multi-cell deployment (3 Cells per Base
Station (BS) * 7 BS) = 21 cells

F. Cell radius: 166.666 Meters

G. Scheduler: Proportional fair with no priority

H. Bearer: Default bearer for all traffic.

I. Active Queue Management (AQM) settings: AQM [on,off]

2. End to end End-to-end Round Trip Time (RTT): [40, 150] [40ms, 150ms]

3. User arrival model: Poisson arrival model

4. User intensity:

* Downlink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9,
5.6, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5}

* Uplink user intensity : {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9,
5.6, 6.3, 7.0}

5. Simulation duration: 91s

6. Evaluation period: 30s-60s

7. Media traffic:

1. Media type: Video

a. Media direction: [Uplink, Downlink]

b. Number of Media source per user: One (1)

c. Media duration per user: 30s

d. Media source: same as defined in Section 4.3 of
[I-D.ietf-rmcat-eval-test]

2. Media Type: Audio

a. Media direction: Uplink and Downlink

b. Number of Media source per user: One (1)

c. Media duration per user: 30s

d. Media codec: Constant Bit Rate (CBR)

e. Media bitrate: 20 Kbps

f. Adaptation: off

8. Other traffic models:

* Downlink simulation: Maximum of 4Mbps/cell (web browsing or
FTP traffic following default TCP congestion control
[RFC5681])

* Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681])

3.2. Bad Radio Coverage

The goal of this test is to evaluate the performance of candidate
congestion control algorithm when users visit part of the network
with bad radio coverage. The scenario is created by using a larger
cell radius than that in the previous test case. In this test case,
each of the user/UE in the media session is an RMCAT compliant endpoint. The arrival of users follows
User arrivals follow a Poisson distribution proportional to the
length of the call, so as to keep the number of users per cell fairly
constant during the evaluation period. At the beginning of the
simulation, there should be enough amount of time to warm-up the
network. This is to avoid running the evaluation in an empty network
where network nodes are having empty buffers, low interference at the
beginning of the simulation. This network initialization period is therefore
should be excluded from the evaluation period.

This test case also includes user mobility and some competing
traffic. The latter includes the same kind of flows (with same
adaptation algorithms). The investigated congestion control
algorithms should result in maximum possible network utilization and
stability in terms of rate variations, lowest possible end to end
frame latency, network latency and Packet Loss Rate (PLR) at
different cell load levels.

3.2.1. Network connection

Same as defined in Section 3.1.1

3.2.2. Simulation Setup

The desired simulation setup is the same as the Varying Network Load
test case defined in Section 3.1 except the following changes:

1. Radio environment: Same as defined in Section 3.1.2 except the
following:

A. Deployment and propagation model: 3GPP case 3 [Deployment] (see
[HO-deploy-3GPP])

B. Cell radius: 577.3333 Meters
C. Mobility: 3km/h

2. User intensity = {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3,
7.0}

3. Media traffic model: Same as defined in Section 3.1.2

4. Other traffic models:

* Downlink simulation: Maximum of 2Mbps/cell (web browsing or
FTP traffic following default TCP congestion control
[RFC5681])

* Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681])

3.3. Desired Evaluation Metrics for cellular test cases

RMCAT

The evaluation criteria document [I-D.ietf-rmcat-eval-criteria]
defines the metrics to be used to evaluate candidate algorithms.
However, looking at
Considering the nature and distinction of cellular networks we
recommend that at least the following metrics be used to evaluate the
performance of the candidate algorithms for the test cases
defined in this document.

The desired metrics are -- algorithms:

o Average cell throughput (for all cells), shows cell utilizations.

o Application sending and receiving bitrate, goodput.

o Packet Loss Rate (PLR).

o End to end End-to-end Media frame delay. For video, this means the delay
from capture to display.

o Transport delay.

o Algorithm stability in terms of rate variation.

4. Wi-Fi Networks Specific Test Cases

Given the prevalence of Internet access links over Wi-Fi, it is
important to evaluate candidate RMCAT RTP-based congestion control
solutions over test cases that include Wi-Fi access lines. links. Such
evaluations should also highlight the inherently different characteristics
of Wi-
Fi Wi-Fi networks in contrast to their wired networks: counterparts:

o The wireless radio channel is subject to interference from nearby
transmitters, multipath fading, and shadowing, causing shadowing. These effects lead
to fluctuations in the link throughput and sometimes an error-prone error-
prone communication environment environment.

o Available network bandwidth is not only shared over the air
between concurrent users but also between uplink and downlink
traffic due to the half-duplex nature of the wireless transmission
medium.

o Packet transmissions over Wi-Fi are susceptible to contentions and
collisions over the air. Consequently, traffic load beyond a
certain utilization level over a Wi-Fi network can introduce
frequent collisions over the air and significant network overhead,
as well as packet drops due to buffer overflow at the
transmitters. This, in turn, leads to excessive delay,
retransmissions, packet losses and lower effective bandwidth for
applications. Note, however, Note further that the consequent collision-induced delay and
loss patterns caused by collisions are qualitatively different from those induced caused by
congestion over a wired connection.

o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate
transmission capabilities by dynamically choosing the most
appropriate modulation and coding scheme (MCS) for the given
received signal strength. A different choice of physical-layer rate in the MCS Index
leads to different physical-layer (PHY-layer) link rates and
consequently different application-layer throughput.

o Presence The presence of legacy 802.11b networks devices (e.g., ones operating only in IEEE
802.11b) at a much lower PHY-layer link rate can significantly
slow down the rest of a modern Wi-Fi network. As discussed in
[Heusse2003], the main reason for such abnomaly anomaly is that it takes
much longer to transmit the same packet over a slower link than
over a faster
link. link, thereby consuming a substantial portion of air
time.

o Handover from one Wi-Fi Access Point (AP) to another may lead to
excessive packet delay delays and losses during the process.

o IEEE 802.11e defined EDCA/WMM (Enhanced DCF has introduced the Enhanced Distributed Channel Access/Wi-Fi
Multi-Media)
Access (EDCA) mechanism to allow different traffic categories to give
contend for channel access using different random back-off
parameters. This mechanism is a mandatory requirement for the Wi-
Fi Multimedia (WMM) certification in Wi-Fi Alliance. It allows
for prioritization of real-time application traffic such as voice
and video streams higher priority over
pure non-urgent data applications transmissions (e.g., file transfers).
transfer).

In summary, the presence of Wi-Fi access links in different network
topologies can exert different impact on the network performance in
terms of application-layer effective throughput, packet loss rate,
and packet delivery delay. These, in turn, will influence the
behavior of end-to-end real-time multimedia congestion control.

Unless otherwise mentioned, the test cases in this section are described
using choose the underlying
PHY- and MAC-layer parameters based on the IEEE 802.11n Standard.
Statistics collected from enterprise Wi-Fi networks show that the two
dominant physical modes are 802.11n and 802.11ac, accounting for 41%
and 58% of connected devices. As Wi-Fi standards evolve over time --
for instance, with the introduction of the emerging Wi-Fi 6 (802.11ax) (based on
IEEE 802.11ax) products -- the PHY- and MAC-layer test case
specifications need to be updated accordingly to reflect such
changes.

Typically, a Wi-Fi access network connects to a wired infrastructure.
Either the wired or the Wi-Fi segment of the network could can be the
bottleneck. In the The following sections, we sections describe basic test cases for
both scenarios separately. The same set of performance metrics as in
[I-D.ietf-rmcat-eval-test]) should be collected for each test case.

All test cases described below can be carried

We recommend to carry out the test cases as defined in this document
using simulations,
e.g. based on [ns-2] a simulator, such as [NS-2] or [ns-3]. [NS-3]. When feasible, it is also
encouraged to perform testbed-based evaluations using Wi-Fi access
points and endpoints running up-to-date IEEE 802.11 protocols, such
as 802.11ac and the emerging Wi-Fi 6, so as to verify the viability
of the candidate schemes.

4.1. Bottleneck in Wired Network

The test scenarios below are intended to mimic the setup of video
conferencing over Wi-Fi connections from the home. Typically, the
Wi-Fi home network is not congested and the bottleneck is present
over the wired home access link. Although it is expected that test
evaluation results from this section are similar to those from test
cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), as in
[I-D.ietf-rmcat-eval-test], it is still worthwhile to run through
these tests as sanity checks.

4.1.1. Network topology

Figure 2 shows the network topology of Wi-Fi test cases. The test
contains multiple mobile nodes (MNs) connected to a common Wi-Fi
access point (AP) and their corresponding wired clients on fixed
nodes (FNs). Each connection carries either a RMCAT RTP-based media flow
or a TCP traffic flow. Directions of the flows can be uplink, downlink, uplink (i.e.,
from mobile nodes to fixed nodes), downlink (i.e., from fixed nodes
to mobile nodes), or bi-
directional. bi-directional. The total number of
uplink/downlink/bi-directional flows for RTP-based media traffic and
TCP traffic are denoted as N and M, respectively.

Uplink
+----------------->+
+------+ +------+
| MN_1 |)))) /=====| FN_1 |
+------+ )) // +------+
. )) // .
. )) // .
. )) // .
+------+ +----+ +-----+ +------+
| MN_N | ))))))) | | | |========| FN_N |
+------+ | | | | +------+
| AP |=========| FN0 |
+----------+ | | | | +----------+
| MN_tcp_1 | )))) | | | |======| MN_tcp_1 FN_tcp_1 |
+----------+ +----+ +-----+ +----------+
. )) \\ .
. )) \\ .
. )) \\ .
+----------+ )) \\ +----------+
| MN_tcp_M |))) \=====| MN_tcp_M FN_tcp_M |
+----------+ +----------+
+<-----------------+
Downlink

Figure 2: Network topology for Wi-Fi test cases

4.1.2. Test setup

o Test duration: 120s

o Wi-Fi network characteristics:

* Radio propagation model: Log-distance path loss propagation
model [NS3WiFi] (see [NS3WiFi])

* PHY- and MAC-layer configuration: IEEE 802.11n

* MCS Index at 11: 16-QAM 1/2, Raw Data Rate@52Mbps Rate at 52Mbps

o Wired path characteristics:

* Path capacity: 1Mbps

* One-Way propagation delay: 50ms.

* Maximum end-to-end jitter: 30ms

* Bottleneck queue type: Drop tail.

* Bottleneck queue size: 300ms.

* Path loss ratio: 0%.

o Application characteristics:

* Media Traffic:

+ Media type: Video

+ Media direction: See Section 4.1.3

+ Number of media sources (N): See Section 4.1.3

+ Media timeline:

- Start time: 0s.

- End time: 119s.

* Competing traffic:

+ Type of sources: long-lived TCP or CBR over UDP

+ Traffic direction: See Section 4.1.3

+ Number of sources (M): See Section 4.1.3

+ Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP.

+ Traffic timeline: See Section 4.1.3

4.1.3. Typical test scenarios

o Single uplink RMCAT RTP-based media flow: N=1 with uplink direction and
M=0.

o One pair of bi-directional RMCAT RTP-based media flows: N=2 (with (i.e., one
uplink flow and one downlink flow); M=0.

o One pair of bi-directional RMCAT flows, RTP-based media flows: N=2; one uplink
on-off CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow); over UDP: M=1 (uplink). The CBR flow has ON time
at 0s-60s, t=0s-60s and OFF time at 60s-119s. t=60s-119s.

o One pair of bi-directional RMCAT flows, RTP-based media flows: N=2; one uplink
off-on CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow); over UDP: M=1 (uplink). The CBR flow has OFF time for UDP flow: 0s-60s;
at t=0s-60s and ON time: 60s-119s. time at t=60s-119s.

o One RMCAT RTP-based media flow competing against one long-live TCP flow over
uplink:
in the uplink direction: N=1 (uplink) and M = 1(uplink), 1(uplink). The TCP
flow has start time at 0s t=0s and end time at 119s. t=119s.

4.1.4. Expected behavior

o Single uplink RMCAT RTP-based media flow: the candidate algorithm is
expected to detect the path capacity constraint, to converge to
the bottleneck link capacity capacity, and to adapt the flow to avoid
unwanted oscillation oscillations when the sending bit rate is approaching the
bottleneck link capacity. No excessive oscillations in the media
rate should be present.

o Bi-directional RMCAT RTP-based media flows: It is expected that the candidate algorithm is able
expected to converge to the bottleneck capacity of the wired path on
in both directions despite the presence of measurement noise over
the Wi-Fi connection. In the presence of background TCP or CBR
over UDP traffic, the rate of RMCAT RTP-based media flows should adapt
in a timely manner
promptly to changes in the available bottleneck
bandwidth. arrival and departure of background traffic flows.

o One RMCAT RTP-based media flow competing with long-live TCP flow over uplink: in the
uplink direction: the candidate algorithm should be able is expected to avoid
congestion collapse, collapse and to stabilize at a fair share of the
bottleneck link capacity.

4.2. Bottleneck in Wi-Fi Network

These

The test cases in this section assume that the wired portion segment along
the media path is well-provisioned whereas the bottleneck exists over
the Wi-Fi access network. This is to mimic the application scenarios
typically encountered by users in an enterprise environment or at a
coffee house.

4.2.1. Network topology

Same as defined in Section 4.1.1

4.2.2. Test setup

o Test duration: 120s

o Wi-Fi network characteristics:

* Radio propagation model: Log-distance path loss propagation
model [NS3WiFi] (see [NS3WiFi])

* PHY- and MAC-layer configuration: IEEE 802.11n
* MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps

o Wired path characteristics:

* Path capacity: 100Mbps.

* One-Way propagation delay: 50ms.

* Maximum end-to-end jitter: 30ms.

* Bottleneck queue type: Drop tail.

* Bottleneck queue size: 300ms.

* Path loss ratio: 0%.

o Application characteristics:

* Media Traffic:

+ Media type: Video

+ Media direction: See Section 4.2.3.

+ Number of media sources (N): See Section 4.2.3.

+ Media timeline:

- Start time: 0s.

- End time: 119s.

* Competing traffic:

+ Type of sources: long-lived TCP or CBR over UDP.

+ Number of sources (M): See Section 4.2.3.

+ Traffic direction: See Section 4.2.3.

+ Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP.

+ Traffic timeline: See Section 4.2.3.

4.2.3. Typical test scenarios

This section describes a few test scenarios that are deemed as
important for understanding the behavior of a candidate RMCAT
solution RTP-based
congestion control scheme over a Wi-Fi network.

a. Multiple RMCAT Flows Sharing RTP-based media flows sharing the Wireless Downlink: wireless downlink:
N=16 (all downlink); M = 0. This test case is for studying the
impact of contention on the multiple concurrent RMCAT media flows. For
an 802.11n network, given the MCS Index of 11 and the
corresponding
raw data link rate of 52Mbps, the total application-layer
throughput (assuming reasonable distance, low interference and
infrequent contentions caused by competing streams) is around
20Mbps.
Consequently, a A total of N=16 RMCAT RTP-based media flows (with a maximum
rate of 1.5Mbps each) are needed expected to saturate the wireless
interface in this experiment. Evaluation of a given candidate solution
scheme should focus on whether the downlink RMCAT media flows can
stabilize at a fair share of the total application-layer
throughput.

b. Multiple RMCAT Flows Sharing RTP-based media flows sharing the Wireless Uplink: N wireless uplink:N = 16
(all downlink); M = 0. When multiple clients attempt to transmit
video
media packets uplink over the wireless interface, Wi-Fi network, they introduce more
frequent contentions and potential collisions. Per-flow
throughput is expected to be lower than that in the previous
downlink-only scenario. Evaluation of a given candidate solution scheme
should focus on whether the uplink flows can stabilize at a fair
share of the total application-layer throughput.

c. Multiple Bi-directional RMCAT Flows: bi-directional RTP-based media flows: N = 16 (8 uplink
and 8 downlink); M = 0. The goal of this test is to evaluate the
performance of the candidate solution scheme in terms of bandwidth
fairness between uplink and downlink flows.

d. Multiple Bi-directional RMCAT Flows bi-directional RTP-based media flows with on-off CBR traffic:
traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5(uplink). 5
(uplink). The goal of this test is to evaluate the adaptation
behavior of the candidate
solution scheme when its available bandwidth
changes due to the departure of background traffic. The
background traffic consists of several (e.g., M=5) CBR flows
transported over UDP. These background flows are ON at times time
t=0-60s and are OFF at times time t=61-120s.

e. Multiple Bi-directional RMCAT Flows bi-directional RTP-based media flows with off-on CBR traffic:
traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5(uplink). 5
(uplink). The goal of this test is to evaluate the adaptation
behavior of the candidate
solution scheme when its available bandwidth
changes due to the arrival of background traffic. The background
traffic consists of several (e.g., M=5) parallel CBR flows
transported over UDP. These background flows are OFF at times time
t=0-60s and are ON at times t=61-120s.

f. Multiple Bi-directional RMCAT bi-directional RTP-based media flows in the presence of
background TCP traffic: N=16 (8 uplink and 8 downlink); M = 5
(uplink). The goal of this test is to evaluate how RMCAT RTP-based
media flows compete against TCP over a congested Wi-Fi network
for a given candidate
solution. scheme. TCP flows have start time: 40s, time at t=40s
and end time: 80s. time at t=80s.

g. Varying number of RMCAT RTP-based media flows: A series of tests can be
carried out for the above test cases with different values of N,
e.g., N = [4, 8, 12, 16, 20]. The goal of this test is to
evaluate how a candidate RMCAT solution scheme responds to varying traffic load/demand load/
demand over a congested Wi-Fi network. The start time times of these RMCAT the
media flows is are randomly distributed distributes within a window of t=0-10s, whereas t=0-10s;
their end times are randomly distributed within a window of
t=110-120s.

4.2.4. Expected behavior

o Multiple downlink RMCAT RTP-based media flows: each RMCAT media flow should is
expected to get its fair share of the total bottleneck link
bandwidth. Overall bandwidth usage should not be significantly
lower than that experienced by the same number of concurrent
downlink TCP flows. In other words, the performance behavior of multiple
concurrent TCP flows will be used as a performance benchmark for
this test scenario. The end-to-end delay and packet loss ratio
experienced by each flow should be within an acceptable range for
real-time multimedia applications.

o Multiple uplink RMCAT RTP-based media flows: overall bandwidth usage shared by
all
RMCAT media flows should not be significantly lower than that
experienced by the same number of concurrent uplink TCP flows. In
other words, the performance behavior of multiple concurrent TCP flows will be
used as a performance benchmark for this test scenario.

o Multiple bi-directional RMCAT RTP-based media flows with dynamic
background traffic carrying CBR flows over UDP: RMCAT the media flows should
are expected to adapt in a timely fashion to the resulting changes in
available bandwidth. bandwidth introduced by the arrival/departure of
background traffic.

o Multiple bi-directional RMCAT RTP-based media flows with dynamic
background traffic over TCP: during the presence of TCP background
flows, the overall bandwidth usage shared by all RMCAT media flows should not
be significantly lower than those achieved by the same number of bi-
directional
bi-directional TCP flows. In other words, the performance behavior of
multiple concurrent TCP flows will be used as a performance
benchmark for this test scenario. All downlink RMCAT media flows are
expected to obtain similar bandwidth with respect to as each other. The
throughput of RMCAT flows should each media flow is expected to decrease upon the
arrival of TCP background traffic and and, conversely, increase upon
their departure, both departure. Both reactions should occur in a timely fashion (e.g., fashion,
for example, within 10s of
seconds). seconds.

o Varying number of bi-directional RMCAT RTP-based media flows: the test
results for varying values of N -- while keeping all other
parameters constant -- is expected to show steady and stable per-flow per-
flow throughput for each value of N. The average throughput of
all RMCAT media flows is expected to stay constant around the maximum
rate when N is small, then gradually decrease with increasing number
value of RMCAT flows N till it reaches the minimum allowed rate, beyond which
the offered load to the Wi-Fi network (with exceeds its capacity (i.e.,
with a very large value of N) is exceeding its
capacity. N).

4.3. Other Potential Test Cases

4.3.1. EDCA/WMM usage

The EDCA/WMM is mechanism defines prioritized QoS with for four traffic
classes (or Access
Categories) with differing priorities. RMCAT Categories). RTP-based real-time media flows
should achieve better performance (i.e., in terms of lower delay, delay and fewer
packet losses) losses with EDCA/WMM enabled when competing against non-interactive non-
interactive background traffic (e.g., such as file transfers). transfers. When most of
the traffic over Wi-Fi is dominated by media, however, turning on WMM
may actually degrade performance since all media flows now attempt to access
the wireless transmission medium more aggressively, thereby causing
more frequent collisions and collision-induced losses. This is a
topic worthy of further investigation.

4.3.2. Effects Effect of Legacy 802.11b Devices

When there exist heterogeneous link rates

As discussed in [Heusse2003], the presence of clients operating over
slow PHY-layer link rates (e.g., a legacy 802.11b devices device) connected
to a modern 802.11
network, they network may affect adversely impact the overall performance of
the whole network. Additional test cases can be added devised to evaluate the impacts
effect of legacy
devices clients with heterogeneous link rates on the performance of
the candidate congestion control algorithm.

5. Conclusion

This document defines a collection of Such test cases cases, for
instance, can specify that are considered
important the PHY-layer link rates for cellular and Wi-Fi networks. Moreover, this document
also provides all clients
span over a framework wide range (e.g., 2Mbps to 54Mbps) for defining additional test cases over
wireless cellular/Wi-Fi networks.

6. IANA Considerations

This investigating its
effect on the congestion control behavior of the real-time
interactive applications.

5. IANA Considerations

This memo includes no request to IANA.

6. Security Considerations

The security considerations in [I-D.ietf-rmcat-eval-criteria] and the
relevant congestion control algorithms apply. The principles for
congestion control are described in [RFC2914], and in particular, any
new method MUST implement safeguards to avoid congestion collapse of
the Internet.

The evaluations of the test cases are intended to carry out in a
controlled lab environment. Hence, the applications, simulators and
network nodes ought to be well-behaved and should not impact the
desired results. It is important to take appropriate caution to
avoid leaking non-responsive traffic from with unproven congestion
avoidance techniques behavior onto the open Internet.

7. Acknowledgments

The authors would like to thank Tomas Frankkila, Magnus Westerlund,
Kristofer Sandlund, and Sergio Mena de la Cruz Cruz, and Mirja Kuehlewind for
their valuable
input inputs and review comments regarding this draft.

8. References

9.1.

8.1. Normative References

[Deployment]

[HO-deploy-3GPP]
TS 25.814, 3GPP., "Physical layer aspects for evolved
Universal Terrestrial Radio Access (UTRA)", October 2006,
<http://www.3gpp.org/ftp/specs/
archive/25_series/25.814/25814-710.zip>.

[HO-def-3GPP]
TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications",
December 2009, <http://www.3gpp.org/ftp/specs/
archive/21_series/21.905/21905-940.zip>.

[HO-LTE-3GPP]
TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC);
Protocol specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/36_series/36.331/36331-990.zip>.

[HO-UMTS-3GPP]
TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol
specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/25_series/25.331/25331-990.zip>.

[I-D.ietf-rmcat-eval-criteria]
Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion
Control for Interactive Real-time Media", draft-ietf-
rmcat-eval-criteria-08
rmcat-eval-criteria-11 (work in progress), November 2018. February 2020.

[I-D.ietf-rmcat-eval-test]
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat-
eval-test-10 (work in progress), May 2019.

[IEEE802.11]
IEEE, "Standard for Information technology--
Telecommunications and information exchange between
systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications", 2012.

[NS3WiFi] "Wi-Fi Channel Model in NS3 ns-3 Simulator",
<https://www.nsnam.org/doxygen/
classns3_1_1_yans_wifi_channel.html>.

[QoS-3GPP]
TS 23.203, 3GPP., "Policy and charging control
architecture", June 2011, <http://www.3gpp.org/ftp/specs/
archive/23_series/23.203/23203-990.zip>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.

[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.

8.2. Informative References

[Heusse2003]
Heusse, M., Rousseau, F., Berger-Sabbatel, G., and A.
Duda, "Performance anomaly of 802.11b", in Proc. 23th
Annual Joint Conference of the IEEE Computer and
Communications Societies, (INFOCOM'03), March 2003.

[HO-def-3GPP]
TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications",
December 2009, <http://www.3gpp.org/ftp/specs/
archive/21_series/21.905/21905-940.zip>.

[HO-LTE-3GPP]
TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC);
Protocol specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/36_series/36.331/36331-990.zip>.

[HO-UMTS-3GPP]
TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol
specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/25_series/25.331/25331-990.zip>.

[I-D.ietf-rmcat-cc-requirements]
Jesup, R. and Z. Sarker, "Congestion Control Requirements
for Interactive Real-Time Media", draft-ietf-rmcat-cc-
requirements-09 (work in progress), December 2014.

[I-D.ietf-rmcat-eval-test]
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat-
eval-test-10 (work in progress), May 2019.

[LTE-simulator]
"NS-3, A discrete-Event

[NS-2] "ns-2", December 2014,
<http://nsnam.sourceforge.net/wiki/index.php/Main_Page>.

[NS-3] "ns-3 Network Simulator",
<https://www.nsnam.org/docs/release/3.23/manual/html/
index.html>.

[ns-2] "The Network Simulator - ns-2",
<http://www.isi.edu/nsnam/ns/>.

[ns-3] "The Network Simulator - ns-3", <https://www.nsnam.org/>.

[QoS-3GPP]
TS 23.203, 3GPP., "Policy and charging control
architecture", June 2011, <http://www.3gpp.org/ftp/specs/
archive/23_series/23.203/23203-990.zip>.

[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.

Authors' Addresses

Zaheduzzaman Sarker
Ericsson AB
Laboratoriegraend 11
Luleae 97753
Sweden

Phone: +46 107173743
Email: zaheduzzaman.sarker@ericsson.com

Ingemar Johansson
Ericsson AB
Laboratoriegraend 11
Luleae 97753
Sweden

Phone: +46 10 7143042
Email: ingemar.s.johansson@ericsson.com

Xiaoqing Zhu
Cisco Systems
12515 Research Blvd., Building 4
Austin, TX 78759
USA

Email: xiaoqzhu@cisco.com
Jiantao Fu
Cisco Systems
707 Tasman
771 Alder Drive
Milpitas, CA 95035
USA

Email: jianfu@cisco.com

Wei-Tian Tan
Cisco Systems
725 Alder Drive
510 McCarthy Blvd
Milpitas, CA 95035
USA

Email: dtan2@cisco.com

Michael A. Ramalho
Cisco Systems, Inc.
8000 Hawkins Road
Sarasota,
AcousticComms Consulting
6310 Watercrest Way Unit 203
Lakewood Ranch, FL 34241 34202-5211
USA

Phone: +1 919 476 2038 732 832 9723
Email: mramalho@cisco.com mar42@cornell.edu