Network Working Group Z. Sarker
Internet-Draft I. Johansson
Intended status: Informational Ericsson AB
Expires: January 2, 2020 X. Zhu
J. Fu
W. Tan
M. Ramalho
Cisco Systems
July 1, 2019
Evaluation Test Cases for Interactive Real-Time Media over Wireless
Networks
draft-ietf-rmcat-wireless-tests-07
Abstract
The Real-time Transport Protocol (RTP) is used for interactive
multimedia communication applications. A congestion control
algorithm is typically required by these applications. To ensure
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 congestion control algorithms over LTE and Wi-Fi
networks.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 2, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . 8
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 . . . . . . . . . . . . . . . 16
4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18
4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19
4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19
4.3.2. Effects of Legacy 802.11b Devices . . . . . . . . . . 19
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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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 increasingly more significant
portion of the media traffic over the Internet. Application
scenarios range from video conferencing calls in a bus or train to
media consumption by someone sitting on a living room couch. 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 basic test cases for evaluating RTP-based congestion control
schemes as defined in [I-D.ietf-rmcat-eval-test] have covered many
effects of the impairments common to both wired and wireless
networks, there remain characteristics and dynamics unique to a given
wireless environment. For example, in LTE networks, the base station
maintains individual queues per radio bearer per user hence it leads
to a different nature of interaction between traffic flows of
different users. This contrasts with wired network, where traffic
from all users share the same queue. Furthermore, user mobility
patterns in a cellular network differs 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 [I-D.ietf-rmcat-eval-criteria] document
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 a wireline ditto
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
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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 which 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 some packet losses and delay variations.
Moreover, with increased cell load or handover to a congested cell,
congestion in transport network will become even worse. Besides,
there are certain characteristics which make the cellular network
different from and more challenging than other types of access
networks such as Wi-Fi and wired network. 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.
* Left over/ unused resource can be grabbed 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 ("handover" definition in [HO-def-3GPP] ).
o Handover between cells, or change of serving cells (see 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
* Can vary as fast as a period of milliseconds.
* Depends on lots of facts (such as distance, speed,
interference, different flows).
* Uses complex and smart link adaptation which makes the link
behavior ever more dynamic.
* The scheduling priority depends on the estimated throughput.
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o Both Quality of Service (QoS) and non-QoS radio bearers can be
used.
Hence, a real-time communication application operating in such a
cellular network need to cope with shared bottleneck link and
variable link capacity, event likes handover, non-congestion related
loss, abrupt change in bandwidth (both short term and long term) due
to handover, network load and bad radio coverage. Even though 3GPP
define QoS bearers [QoS-3GPP] to ensure high quality user experience,
adaptive real-time applications are desired.
Different mobile operators deploy their own cellular network 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 radio technologies can
support the high bandwidth requirements from 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 radio technologies) more suitable access
technology for such genre of application.
The key factors to define test cases for cellular networks are
o Shared and varying link capacity
o Mobility
o Handover
However, for cellular network it is very hard to separate such events
from one another as these events are heavily related. Hence instead
of devising separate test cases for all those important events we
have divided the test case in two categories. It should be noted
that in the following test cases the goal is to evaluate the
performance of candidate algorithms over 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 any extra congestion in the path. Also the
combination of multiple access technologies such as one user has LTE
connection and another has Wi-Fi connection is kept out of the scope
of this document. However, later those additional scenarios can also
be added in this list of test cases. While defining the test cases
we assumed a typical real-time telephony scenario over cellular
networks where one real-time session consists of one voice stream and
one video stream. We recommend that an LTE network simulator is used
for the test cases defined in this document, for example-NS-3 LTE
simulator [LTE-simulator].
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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 a Poisson distribution, which is
proportional to the length of the call, so that the number of users
per cell is kept 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 excluded from the evaluation
period.
This test case also includes user mobility and competing traffic.
The competing traffic includes both same kind of flows (with same
adaptation algorithms) and different kind of flows (with different
service and congestion control). 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 a LTE radio
access, an Evolved Packet Core (EPC) and an Internet connection. The
mobile user is connected to the EPC using LTE radio access technology
which is further connected to the Internet. The fixed user is
connected to the Internet via wired connection with sufficiently high
bandwidth, for instance, 10 Gbps, so that the system is resource-
limited on the wireless interface. The Internet and wired connection
in this setup does not introduce any network impairments to the test;
it only adds 10ms of one-way propagation delay.
The path from the fixed user to mobile user is defines as "Downlink"
and the path from mobile user to the fixed user is defined as
"Uplink". We assume that only uplink or downlink is congested for
the mobile users. Hence, we recommend that the uplink and downlink
simulations are run separately.
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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 notion set in [I-D.ietf-rmcat-eval-test]. The
desired simulation setup as follows-
1. Radio environment
A. Deployment and propagation model : 3GPP case 1[Deployment]
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 Round Trip Time (RTT): [ 40, 150]
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}
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* 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 define 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 BitRate (CBR)
e. Media bitrate : 20 Kbps
f. Adaptation: off
8. Other traffic model:
* 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 larger
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cell radius than 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 a Poisson distribution, which is
proportional to the length of the call, so that the number of users
per cell is kept 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 excluded from the evaluation
period.
This test case also includes user mobility and competing traffic.
The competing traffic includes same kind of flows (with same
adaptation algorithms) . 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.
3.2.1. Network connection
Same as defined in Section 3.1.1
3.2.2. Simulation Setup
The desired simulation setup is same as Varying Network Load test
case defined in Section 3.1 except 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]
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 model:
* Downlink simulation: Maximum of 2Mbps/cell (web browsing or
FTP traffic following default TCP congestion control
[RFC5681])
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* 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 evaluation criteria document [I-D.ietf-rmcat-eval-criteria]
defines metrics to be used to evaluate candidate algorithms.
However, looking at the nature and distinction of cellular networks
we recommend at minimum following metrics to be used to evaluate the
performance of the candidate algorithms for the test cases defined in
this document.
The desired metrics are-
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 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 congestion control solutions
over test cases that include Wi-Fi access lines. Such evaluations
should also highlight the inherent different characteristics of Wi-Fi
networks in contrast to wired networks:
o The wireless radio channel is subject to interference from nearby
transmitters, multipath fading, and shadowing, causing
fluctuations in link throughput and sometimes an error-prone
communication environment
o Available network bandwidth is not only shared over the air
between cocurrent users, but also between uplink and downlink
traffic due to the half duplex nature of 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
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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, that the consequent delay and loss
patterns caused by collisions are qualitatively different from
those induced 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 scheme for a given received signal
strength. A different choice of physical-layer rate leads to
different application-layer throughput.
o Presence of legancy 802.11b networks can significantly slow down
the the rest of a modern Wi-Fi Network. As discussed in
[Heusse2003]since it takes longer to transmit the same packet over
a slower link than over a faster link.
o Handover from one Wi-Fi Access Point (AP) to another may lead to
packet delay and losses during the process.
o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi
Multi-Media) to give voice and video streams higher priority over
pure data applications (e.g., file transfers).
In summary, 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, influence the behavior of
end-to-end real-time multimedia congestion control.
Unless otherwise mentioned, test cases in this section are described
using 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) 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 be the
bottleneck. In the following sections, we 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.
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All test cases described below can be carried out using simulations,
e.g. based on [ns-2] or [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, 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]), it
is worthwhile to run through these tests as sanity checks.
4.1.1. Network topology
Figure 2 shows topology of the network for 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 RMCAT or TCP traffic
flow. Directions of the flows can be uplink, downlink, or bi-
directional.
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uplink
+----------------->+
+------+ +------+
| MN_1 |)))) /=====| FN_1 |
+------+ )) // +------+
. )) // .
. )) // .
. )) // .
+------+ +----+ +-----+ +------+
| MN_N | ))))))) | | | |========| FN_N |
+------+ | | | | +------+
| AP |=========| FN0 |
+----------+ | | | | +----------+
| MN_tcp_1 | )))) | | | |======| MN_tcp_1 |
+----------+ +----+ +-----+ +----------+
. )) \\ .
. )) \\ .
. )) \\ .
+----------+ )) \\ +----------+
| MN_tcp_M |))) \=====| MN_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]
* PHY- and MAC-layer configuration: IEEE 802.11n
* MCS Index at 11: 16-QAM 1/2, Raw Data Rate@52Mbps
o Wired path characteristics:
* Path capacity: 1Mbps
* One-Way propagation delay: 50ms.
* Maximum end-to-end jitter: 30ms
* Bottleneck queue type: Drop tail.
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* 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 flow: N=1 with uplink direction and M=0.
o One pair of bi-directional RMCAT flows: N=2 (with one uplink flow
and one downlink flow); M=0.
o One pair of bi-directional RMCAT flows, one on-off CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow);
M=1 (uplink). CBR flow ON time at 0s-60s, OFF time at 60s-119s.
o One pair of bi-directional RMCAT flows, one off-on CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow);
M=1 (uplink). OFF time for UDP flow: 0s-60s; ON time: 60s-119s.
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o One RMCAT flow competing against one long-live TCP flow over
uplink: N=1 (uplink) and M = 1(uplink), TCP start time at 0s and
end time at 119s.
4.1.4. Expected behavior
o Single uplink RMCAT flow: the candidate algorithm is expected to
detect the path capacity constraint, to converge to bottleneck
link capacity and to adapt the flow to avoid unwanted oscillation
when the sending bit rate is approaching the bottleneck link
capacity. No excessive rate oscillations should be present.
o Bi-directional RMCAT flows: It is expected that the candidate
algorithm is able to converge to the bottleneck capacity of the
wired path on both directions despite presence of measurment noise
over the Wi-Fi connection. In the presence of background TCP or
CBR over UDP traffic, the rate of RMCAT flows should adapt in a
timely manner to changes in the available bottleneck bandwidth.
o One RMCAT flow competing with long-live TCP flow over uplink: the
candidate algorithm should be able to avoid congestion collapse,
and to stablize at a fair share of the bottleneck link capacity.
4.2. Bottleneck in Wi-Fi Network
These test cases assume that the wired portion 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]
* PHY- and MAC-layer configuration: IEEE 802.11n
* MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps
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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 RMCAT candidate
solution over a Wi-Fi network.
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o Multiple RMCAT Flows Sharing the Wireless Downlink: N=16 (all
downlink); M = 0. This test case is for studying the impact of
contention on competing RMCAT flows. For an 802.11n network,
given the MCS Index of 11 and the corresponding raw data 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
total of N=16 RMCAT flows are needed to saturate the wireless
interface in this experiment. Evaluation of a given candidate
solution should focus on whether downlink RMCAT flows can stablize
at a fair share of total application-layer throughput.
o Multiple RMCAT Flows Sharing the Wireless Uplink: N = 16 (all
downlink); M = 0. When multiple clients attempt to transmit video
packets uplink over the wireless interface, 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
should focus on whether uplink flows can stablize at a fair share
of application-layer throughput.
o Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8
downlink); M = 0. The goal of this test is to evaluate
performance of the candidate solution in terms of bandwidth
fairness between uplink and downlink flows.
o Multiple Bi-directional RMCAT Flows with on-off CBR traffic: N =
16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this
test is to evaluate adaptation behavior of the candidate solution
when its available bandwidth changes due to departure of
background traffic. The background traffic consists of several
(e.g., M=5) CBR flows transported over UDP, which are ON at times
t=0-60s and are OFF at times t=61-120s.
o Multiple Bi-directional RMCAT Flows with off-on CBR traffic: N =
16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this
test is to evaluate adaptation behavior of the candidate solution
when its available bandwidth changes due to arrival of background
traffic. The background traffic consists of several (e.g., M=5)
parallel CBR flows transported over UDP, which are OFF at times
t=0-60s and are ON at times t=61-120s.
o Multiple Bi-directional RMCAT 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 flows compete against
TCP over a congested Wi-Fi network for a given candidate solution.
TCP start time: 40s, end time: 80s.
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o Varying number of RMCAT 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 responds to varying traffic load/demand
over a congested Wi-Fi network. The start time of these RMCAT
flows is randomly distributed within a window of t=0-10s, whereas
their end times are randomly distributed within a window of
t=110-120s.
4.2.4. Expected behavior
o Multiple downlink RMCAT flows: each RMCAT flow should 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 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 acceptable range for real-time multimedia applications.
o Multiple uplink RMCAT flows: overall bandwidth usage shared by all
RMCAT flows should not be significantly lower than that
experienced by the same number of concurrent uplink TCP flows. In
other words, the performance of multiple concurrent TCP flows will
be used as a performance benchmark for this test scenario.
o Multiple bi-directional RMCAT flows with dynamic background
traffic carrying CBR flows over UDP: RMCAT flows should adapt in a
timely fashion to the resulting changes in available bandwidth.
o Multiple bi-directional RMCAT flows with dynamic background
traffic over TCP: during the presence of TCP background flows, the
overall bandwidth usage shared by all RMCAT flows should not be
significantly lower than those achieved by the same number of bi-
directional TCP flows. In other words, the performance of
multiple concurrent TCP flows will be used as a performance
benchmark for this test scenario. All downlink RMCAT flows are
expected to obtain similar bandwidth with respect to each other.
The throughput of RMCAT flows should decrease upon the arrival of
TCP background traffic and increase upon their departure, both
reactions should occur in a timely fashion (e.g., within 10s of
seconds).
o Varying number of RMCAT flows: the test results for varying values
of N -- while keeping all other parameters constant -- is expected
to show steady and stable per-flow throughtput for each value of
N. The average throughput of all RMCAT flows is expected to stay
constant around the maximum rate when N is small, then gradually
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decrease with increasing number of RMCAT flows till it reaches the
minimum allowed rate, beyond which the offered load to the Wi-Fi
network (with a large value of N) is exceeding its capacity.
4.3. Other Potential Test Cases
4.3.1. EDCA/WMM usage
EDCA/WMM is prioritized QoS with four traffic classes (or Access
Categories) with differing priorities. RMCAT flows should achieve
better performance (i.e., lower delay, fewer packet losses) with
EDCA/WMM enabled when competing against non-interactive background
traffic (e.g., file 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 of Legacy 802.11b Devices
When there is 802.11b devices connected to modern 802.11 network, it
may affect the performance of the whole network. Additional test
cases can be added to evaluate the affects of legancy devices on the
performance of RMCAT congestion control algorithm.
5. Conclusion
This document defines a collection of test cases that are considered
important for cellular and Wi-Fi networks. Moreover, this document
also provides a framework for defining additional test cases over
wireless cellular/Wi-Fi networks.
6. IANA Considerations
This memo includes no request to IANA.
7. 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 evaluation of the test cases are intended to be run in a
controlled lab environment. Hence, the applications, simulators and
network nodes ought to be well-behaved and should not impact the
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desired results. It is important to take appropriate caution to
avoid leaking non-responsive traffic from unproven congestion
avoidance techniques onto the open Internet.
8. Acknowledgments
We would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer
Sandlund, and Sergio Mena de la Cruz for their valuable input and
review comments regarding this draft.
9. References
9.1. Normative References
[Deployment]
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 (work in progress), November 2018.
[NS3WiFi] "Wi-Fi Channel Model in NS3 Simulator",
<https://www.nsnam.org/doxygen/
classns3_1_1_yans_wifi_channel.html>.
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[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. 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.
[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.
[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.
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[LTE-simulator]
"NS-3, A discrete-Event 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/>.
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 Drive
Milpitas, CA 95035
USA
Email: jianfu@cisco.com
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Wei-Tian Tan
Cisco Systems
725 Alder Drive
Milpitas, CA 95035
USA
Email: dtan2@cisco.com
Michael A. Ramalho
Cisco Systems, Inc.
8000 Hawkins Road
Sarasota, FL 34241
USA
Phone: +1 919 476 2038
Email: mramalho@cisco.com
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