draft-ietf-rmcat-wireless-tests-11.txt   rfc8869.txt 
Network Working Group Z. Sarker Internet Engineering Task Force (IETF) Z. Sarker
Internet-Draft Ericsson AB Request for Comments: 8869 Ericsson AB
Intended status: Informational X. Zhu Category: Informational X. Zhu
Expires: September 14, 2020 J. Fu ISSN: 2070-1721 J. Fu
Cisco Systems Cisco Systems
March 13, 2020 January 2021
Evaluation Test Cases for Interactive Real-Time Media over Wireless Evaluation Test Cases for Interactive Real-Time Media over Wireless
Networks Networks
draft-ietf-rmcat-wireless-tests-11
Abstract Abstract
The Real-time Transport Protocol (RTP) is a common transport choice The Real-time Transport Protocol (RTP) is a common transport choice
for interactive multimedia communication applications. The for interactive multimedia communication applications. The
performance of these applications typically depends on a well- performance of these applications typically depends on a well-
functioning congestion control algorithm. To ensure a seamless and functioning congestion control algorithm. To ensure a seamless and
robust user experience, a well-designed RTP-based congestion control robust user experience, a well-designed RTP-based congestion control
algorithm should work well across all access network types. This algorithm should work well across all access network types. This
document describes test cases for evaluating performances of document describes test cases for evaluating performances of
candidate congestion control algorithms over cellular and Wi-Fi candidate congestion control algorithms over cellular and Wi-Fi
networks. networks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on September 14, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8869.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Cellular Network Specific Test Cases . . . . . . . . . . . . 3 2. Cellular Network Specific Test Cases
2.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6 2.1. Varying Network Load
2.1.1. Network Connection . . . . . . . . . . . . . . . . . 6 2.1.1. Network Connection
2.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 2.1.2. Simulation Setup
2.1.3. Expected behavior . . . . . . . . . . . . . . . . . . 9 2.1.3. Expected Behavior
2.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 9 2.2. Bad Radio Coverage
2.2.1. Network connection . . . . . . . . . . . . . . . . . 9 2.2.1. Network Connection
2.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 2.2.2. Simulation Setup
2.2.3. Expected behavior . . . . . . . . . . . . . . . . . . 10 2.2.3. Expected Behavior
2.3. Desired Evaluation Metrics for cellular test cases . . . 10 2.3. Desired Evaluation Metrics for Cellular Test Cases
3. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 3. Wi-Fi Networks Specific Test Cases
3.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 3.1. Bottleneck in Wired Network
3.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 3.1.1. Network Topology
3.1.2. Test/simulation setup . . . . . . . . . . . . . . . . 13 3.1.2. Test/Simulation Setup
3.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 3.1.3. Typical Test Scenarios
3.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15 3.1.4. Expected Behavior
3.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15 3.2. Bottleneck in Wi-Fi Network
3.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 3.2.1. Network Topology
3.2.2. Test/simulation setup . . . . . . . . . . . . . . . . 16 3.2.2. Test/Simulation Setup
3.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17 3.2.3. Typical Test Scenarios
3.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18 3.2.4. Expected Behavior
3.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19 3.3. Other Potential Test Cases
3.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19 3.3.1. EDCA/WMM usage
3.3.2. Effect of heterogeneous link rates . . . . . . . . . 19 3.3.2. Effect of Heterogeneous Link Rates
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 4. IANA Considerations
5. Security Considerations . . . . . . . . . . . . . . . . . . . 20 5. Security Considerations
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 20 6. References
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 6.1. Normative References
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.2. Informative References
8.1. Normative References . . . . . . . . . . . . . . . . . . 21 Contributors
8.2. Informative References . . . . . . . . . . . . . . . . . 22 Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses
1. Introduction 1. Introduction
Wireless networks (both cellular and Wi-Fi [IEEE802.11]) are an Wireless networks (both cellular and Wi-Fi [IEEE802.11]) are an
integral and increasingly more significant part of the Internet. integral and increasingly more significant part of the Internet.
Typical application scenarios for interactive multimedia Typical application scenarios for interactive multimedia
communication over wireless include from video conferencing calls in communication over wireless include video conferencing calls in a bus
a bus or train as well as live media streaming at home. It is well or train as well as live media streaming at home. It is well known
known that the characteristics and technical challenges for that the characteristics and technical challenges for supporting
supporting multimedia services over wireless are very different from multimedia services over wireless are very different from those of
those of providing the same service over a wired network. Although providing the same service over a wired network. Although the basic
the basic test cases as defined in [I-D.ietf-rmcat-eval-test] have test cases as defined in [RFC8867] have covered many common effects
covered many common effects of network impairments for evaluating of network impairments for evaluating RTP-based congestion control
RTP-based congestion control schemes, they remain to be tested over schemes, they remain to be tested over characteristics and dynamics
characteristics and dynamics unique to a given wireless environment. unique to a given wireless environment. For example, in cellular
For example, in cellular networks, the base station maintains networks, the base station maintains individual queues per radio
individual queues per radio bearer per user hence it leads to a bearer per user hence it leads to a different nature of interactions
different nature of interactions between traffic flows of different between traffic flows of different users. This contrasts with a
users. This contrasts with a typical wired network setting where typical wired network setting where traffic flows from all users
traffic flows from all users share the same queue at the bottleneck. share the same queue at the bottleneck. Furthermore, user mobility
Furthermore, user mobility patterns in a cellular network differ from patterns in a cellular network differ from those in a Wi-Fi network.
those in a Wi-Fi network. Therefore, it is important to evaluate the Therefore, it is important to evaluate the performance of proposed
performance of proposed candidate RTP-based congestion control candidate RTP-based congestion control solutions over cellular mobile
solutions over cellular mobile networks and over Wi-Fi networks networks and over Wi-Fi networks respectively.
respectively.
The draft [I-D.ietf-rmcat-eval-criteria] provides the guideline for [RFC8868] provides guidelines for evaluating candidate algorithms and
evaluating candidate algorithms and recognizes the importance of recognizes the importance of testing over wireless access networks.
testing over wireless access networks. However, it does not describe However, it does not describe any specific test cases for performance
any specific test cases for performance evaluation of candidate evaluation of candidate algorithms. This document describes test
algorithms. This document describes test cases specifically cases specifically targeting cellular and Wi-Fi networks.
targeting cellular and Wi-Fi networks.
2. Cellular Network Specific Test Cases 2. Cellular Network Specific Test Cases
A cellular environment is more complicated than its wireline A cellular environment is more complicated than its wireline
counterpart since it seeks to provide services in the context of counterpart since it seeks to provide services in the context of
variable available bandwidth, location dependencies and user variable available bandwidth, location dependencies, and user
mobilities at different speeds. In a cellular network, the user may mobilities at different speeds. In a cellular network, the user may
reach the cell edge which may lead to a significant amount of reach the cell edge, which may lead to a significant number of
retransmissions to deliver the data from the base station to the retransmissions to deliver the data from the base station to the
destination and vice versa. These radio links will often act as a destination and vice versa. These radio links will often act as a
bottleneck for the rest of the network and will eventually lead to bottleneck for the rest of the network and will eventually lead to
excessive delays or packet drops. An efficient retransmission or excessive delays or packet drops. An efficient retransmission or
link adaptation mechanism can reduce the packet loss probability but link adaptation mechanism can reduce the packet loss probability, but
there will remain some packet losses and delay variations. Moreover, some packet losses and delay variations will remain. Moreover, with
with increased cell load or handover to a congested cell, congestion increased cell load or handover to a congested cell, congestion in
in the transport network will become even worse. Besides, there the transport network will become even worse. Besides, there exist
exist certain characteristics that distinguish the cellular network certain characteristics that distinguish the cellular network from
from other wireless access networks such as Wi-Fi. In a cellular other wireless access networks such as Wi-Fi. In a cellular network:
network --
o The bottleneck is often a shared link with relatively few users. * The bottleneck is often a shared link with relatively few users.
* The cost per bit over the shared link varies over time and is - The cost per bit over the shared link varies over time and is
different for different users. different for different users.
* Leftover/unused resources can be consumed by other greedy - Leftover/unused resources can be consumed by other greedy
users. users.
o Queues are always per radio bearer hence each user can have many * Queues are always per radio bearer, hence each user can have many
such queues. such queues.
o Users can experience both Inter and Intra Radio Access Technology * Users can experience both inter- and intra-Radio Access Technology
(RAT) handovers (see [HO-def-3GPP] for the definition of (RAT) handovers (see [HO-def-3GPP] for the definition of
"handover"). "handover").
o Handover between cells or change of serving cells (as described in * Handover between cells or change of serving cells (as described in
[HO-LTE-3GPP] and [HO-UMTS-3GPP]) might cause user plane [HO-LTE-3GPP] and [HO-UMTS-3GPP]) might cause user plane
interruptions which can lead to bursts of packet losses, delay interruptions, which can lead to bursts of packet losses, delay,
and/or jitter. The exact behavior depends on the type of radio and/or jitter. The exact behavior depends on the type of radio
bearer. Typically, the default best-effort bearers do not bearer. Typically, the default best-effort bearers do not
generate packet loss, instead, packets are queued up and generate packet loss, instead, packets are queued up and
transmitted once the handover is completed. transmitted once the handover is completed.
o The network part decides how much the user can transmit. * The network part decides how much the user can transmit.
o The cellular network has variable link capacity per user. * The cellular network has variable link capacity per user.
* It can vary as fast as a period of milliseconds. - It can vary as fast as a period of milliseconds.
* It depends on many factors (such as distance, speed, - It depends on many factors (such as distance, speed,
interference, different flows). interference, different flows).
* It uses complex and smart link adaptation which makes the link - It uses complex and smart link adaptation, which makes the link
behavior ever more dynamic. behavior ever more dynamic.
* The scheduling priority depends on the estimated throughput. - The scheduling priority depends on the estimated throughput.
o Both Quality of Service (QoS) and non-QoS radio bearers can be * Both Quality of Service (QoS) and non-QoS radio bearers can be
used. used.
Hence, a real-time communication application operating over a Hence, a real-time communication application operating over a
cellular network needs to cope with a shared bottleneck link and cellular network needs to cope with a shared bottleneck link and
variable link capacity, events like handover, non-congestion related variable link capacity, events like handover, non-congestion-related
loss, abrupt changes in bandwidth (both short term and long term) due loss, and abrupt changes in bandwidth (both short term and long term)
to handover, network load and bad radio coverage. Even though 3GPP due to handover, network load, and bad radio coverage. Even though
has defined QoS bearers [QoS-3GPP] to ensure high-quality user 3GPP has defined QoS bearers [QoS-3GPP] to ensure high-quality user
experience, it is still preferable for real-time applications to experience, it is still preferable for real-time applications to
behave in an adaptive manner. behave in an adaptive manner.
Different mobile operators deploy their own cellular networks with Different mobile operators deploy their own cellular networks with
their own set of network functionalities and policies. Usually, a their own set of network functionalities and policies. Usually, a
mobile operator network includes a range of radio access technologies mobile operator network includes a range of radio access technologies
such as 3G and 4G/LTE. Looking at the specifications of such radio such as 3G and 4G/LTE. Looking at the specifications of such radio
technologies it is evident that only the more recent radio technologies, it is evident that only the more recent radio
technologies can support the high bandwidth requirements from real- technologies can support the high bandwidth requirements from real-
time interactive video applications. The future real-time time interactive video applications. Future real-time interactive
interactive application will impose even greater demand on cellular applications will impose even greater demand on cellular network
network performance which makes 4G (and beyond) radio technologies performance, which makes 4G (and beyond) radio technologies more
more suitable for such genre of application. suitable for such genre of application.
The key factors in defining test cases for cellular networks are: The key factors in defining test cases for cellular networks are:
o Shared and varying link capacity * Shared and varying link capacity
o Mobility * Mobility
o Handover * Handover
However, these factors are typically highly correlated in a cellular However, these factors are typically highly correlated in a cellular
network. Therefore, instead of devising separate test cases for network. Therefore, instead of devising separate test cases for
individual important events, we have divided the test case into two individual important events, we have divided the test cases into two
categories. It should be noted that the goal of the following test categories. It should be noted that the goal of the following test
cases is to evaluate the performance of candidate algorithms over the cases is to evaluate the performance of candidate algorithms over the
radio interface of the cellular network. Hence it is assumed that radio interface of the cellular network. Hence, it is assumed that
the radio interface is the bottleneck link between the communicating the radio interface is the bottleneck link between the communicating
peers and that the core network does not introduce any extra peers and that the core network does not introduce any extra
congestion along the path. Consequently, this draft has kept as out congestion along the path. Consequently, this document has left out
of scope the combination of multiple access technologies involving of scope the combination of multiple access technologies involving
both cellular and Wi-Fi users. In this latter case the shared both cellular and Wi-Fi users. In this latter case, the shared
bottleneck is likely at the wired backhaul link. These test cases bottleneck is likely at the wired backhaul link. These test cases
further assume a typical real-time telephony scenario where one real- further assume a typical real-time telephony scenario where one real-
time session consists of one voice stream and one video stream. time session consists of one voice stream and one video stream.
Even though it is possible to carry out tests over operational Even though it is possible to carry out tests over operational
cellular networks (e.g., LTE/5G), and actually such tests are already cellular networks (e.g., LTE/5G), and actually such tests are already
available today, these tests cannot in general be carried out in a available today, these tests cannot in general be carried out in a
deterministic fashion to ensure repeatability. The main reason is deterministic fashion to ensure repeatability. The main reason is
that these networks are controlled by cellular operators and there that these networks are controlled by cellular operators, and there
exist various amounts of competing traffic in the same cell(s). In exists various amounts of competing traffic in the same cell(s). In
practice, it is only in underground mines that one can carry out near practice, it is only in underground mines that one can carry out near
deterministic testing. Even there, it is not guaranteed either as deterministic testing. Even there, it is not guaranteed either as
workers in the mines may carry with them their personal mobile workers in the mines may carry with them their personal mobile
phones. Furthermore, the underground mining setting may not reflect phones. Furthermore, the underground mining setting may not reflect
typical usage patterns in an urban setting. We, therefore, recommend typical usage patterns in an urban setting. We, therefore, recommend
that a cellular network simulator is used for the test cases defined that a cellular network simulator be used for the test cases defined
in this document, for example -- the LTE simulator in [NS-3]. in this document, for example -- the LTE simulator in [NS-3].
2.1. Varying Network Load 2.1. Varying Network Load
The goal of this test is to evaluate the performance of the candidate The goal of this test is to evaluate the performance of the candidate
congestion control algorithm under varying network load. The network congestion control algorithm under varying network load. The network
load variation is created by adding and removing network users a.k.a. load variation is created by adding and removing network users,
User Equipments (UEs) during the simulation. In this test case, each a.k.a. User Equipment (UE), during the simulation. In this test
user/UE in the media session is an endpoint following RTP-based case, each user/UE in the media session is an endpoint following RTP-
congestion control. User arrivals follow a Poisson distribution based congestion control. User arrivals follow a Poisson
proportional to the length of the call, to keep the number of users distribution proportional to the length of the call, to keep the
per cell fairly constant during the evaluation period. At the number of users per cell fairly constant during the evaluation
beginning of the simulation, there should be enough time to warm-up period. At the beginning of the simulation, there should be enough
the network. This is to avoid running the evaluation in an empty time to warm up the network. This is to avoid running the evaluation
network where network nodes are having empty buffers, low in an empty network where network nodes have empty buffers and low
interference at the beginning of the simulation. This network interference at the beginning of the simulation. This network
initialization period should be excluded from the evaluation period. initialization period should be excluded from the evaluation period.
Typically, the evaluation period starts 30 seconds after test Typically, the evaluation period starts 30 seconds after test
initialization. initialization.
This test case also includes user mobility and some competing This test case also includes user mobility and some competing
traffic. The latter includes both the same types of flows (with same traffic. The latter includes both the same types of flows (with same
adaptation algorithms) and different types of flows (with different adaptation algorithms) and different types of flows (with different
services and congestion control schemes). services and congestion control schemes).
2.1.1. Network Connection 2.1.1. Network Connection
Each mobile user is connected to a fixed user. The connection Each mobile user is connected to a fixed user. The connection
between the mobile user and fixed user consists of a cellular radio between the mobile user and fixed user consists of a cellular radio
access, an Evolved Packet Core (EPC) and an Internet connection. The access, an Evolved Packet Core (EPC), and an Internet connection.
mobile user is connected to the EPC using cellular radio access The mobile user is connected to the EPC using cellular radio access
technology which is further connected to the Internet. At the other technology, which is further connected to the Internet. At the other
end, the fixed user is connected to the Internet via wired connection end, the fixed user is connected to the Internet via a wired
with sufficiently high bandwidth, for instance, 10 Gbps, so that the connection with sufficiently high bandwidth, for instance, 10 Gbps,
system bottleneck is on the cellular radio access interface. The so that the system bottleneck is on the cellular radio access
wired connection to in this setup does not introduce any network interface. The wired connection in this setup does not introduce any
impairments to the test; it only adds 10 ms of one-way propagation network impairments to the test; it only adds 10 ms of one-way
delay. propagation delay.
The path from the fixed user to the mobile users is defined as 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 "downlink", and the path from the mobile users to the fixed user is
defined as "Uplink". We assume that only uplink or downlink is defined as "uplink". We assume that only uplink or downlink is
congested for mobile users. Hence, we recommend that the uplink and congested for mobile users. Hence, we recommend that the uplink and
downlink simulations are run separately. downlink simulations are run separately.
uplink uplink
++))) +--------------------------> ++))) +-------------------------->
++-+ ((o)) ++-+ ((o))
| | / \ +-------+ +------+ +---+ | | / \ +-------+ +------+ +---+
+--+ / \----+ +-----+ +----+ | +--+ / \----+ +-----+ +----+ |
/ \ +-------+ +------+ +---+ / \ +-------+ +------+ +---+
UE BS EPC Internet fixed UE BS EPC Internet fixed
<--------------------------+ <--------------------------+
downlink downlink
Figure 1: Simulation Topology Figure 1: Simulation Topology
2.1.2. Simulation Setup 2.1.2. Simulation Setup
The values enclosed within "[ ]" for the following simulation The values enclosed within "[ ]" for the following simulation
attributes follow the same notion as in [I-D.ietf-rmcat-eval-test]. attributes follow the same notion as in [RFC8867]. The desired
The desired simulation setup is as follows -- simulation setup is as follows:
1. Radio environment: Radio environment:
A. Deployment and propagation model: 3GPP case 1 (see Deployment and propagation model: 3GPP case 1 (see
[HO-deploy-3GPP]) [HO-deploy-3GPP])
B. Antenna: Multiple-Input and Multiple-Output (MIMO), 2D or 3D Antenna: Multiple-Input and Multiple-Output (MIMO), 2D or 3D
antenna pattern. antenna pattern
C. Mobility: [3km/h, 30km/h] Mobility: [3 km/h, 30 km/h]
D. Transmission bandwidth: 10MHz Transmission bandwidth: 10 MHz
E. Number of cells: multi-cell deployment (3 Cells per Base Number of cells: multi-cell deployment (3 cells per Base Station
Station (BS) * 7 BS) = 21 cells (BS) * 7 BS) = 21 cells
F. Cell radius: 166.666 Meters Cell radius: 166.666 meters
G. Scheduler: Proportional fair with no priority Scheduler: Proportional fair with no priority
H. Bearer: Default bearer for all traffic. Bearer: Default bearer for all traffic
I. Active Queue Management (AQM) settings: AQM [on,off] Active Queue Management (AQM) settings: AQM [on, off]
2. End-to-end Round Trip Time (RTT): [40ms, 150ms] End-to-end Round Trip Time (RTT): [40 ms, 150 ms]
3. User arrival model: Poisson arrival model User arrival model: Poisson arrival model
4. User intensity: User intensity:
* Downlink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, Downlink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6,
5.6, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5} 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, Uplink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6,
5.6, 6.3, 7.0} 6.3, 7.0}
5. Simulation duration: 91s Simulation duration: 91 s
6. Evaluation period: 30s-60s Evaluation period: 30 s - 60 s
7. Media traffic: Media traffic:
1. Media type: Video Media type: Video
a. Media direction: [Uplink, Downlink] Media direction: [uplink, downlink]
b. Number of Media source per user: One (1) Number of media sources per user: One (1)
c. Media duration per user: 30s Media duration per user: 30 s
d. Media source: same as defined in Section 4.3 of Media source: same as defined in Section 4.3 of [RFC8867]
[I-D.ietf-rmcat-eval-test]
2. Media Type: Audio Media type: Audio
a. Media direction: Uplink and Downlink Media direction: [uplink, downlink]
b. Number of Media source per user: One (1) Number of media sources per user: One (1)
c. Media duration per user: 30s Media duration per user: 30 s
d. Media codec: Constant Bit Rate (CBR) Media codec: Constant Bit Rate (CBR)
e. Media bitrate: 20 Kbps Media bitrate: 20 Kbps
f. Adaptation: off Adaptation: off
8. Other traffic models: Other traffic models:
* Downlink simulation: Maximum of 4Mbps/cell (web browsing or Downlink simulation: Maximum of 4 Mbps/cell (web browsing or FTP
FTP traffic following default TCP congestion control traffic following default TCP congestion control [RFC5681])
[RFC5681])
* Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP Uplink simulation: Maximum of 2 Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681]) traffic following default TCP congestion control [RFC5681])
2.1.3. Expected behavior 2.1.3. Expected Behavior
The investigated congestion control algorithms should result in The investigated congestion control algorithms should result in
maximum possible network utilization and stability in terms of rate maximum possible network utilization and stability in terms of rate
variations, lowest possible end to end frame latency, network latency variations, lowest possible end-to-end frame latency, network
and Packet Loss Rate (PLR) at different cell load levels. latency, and Packet Loss Rate (PLR) at different cell load levels.
2.2. Bad Radio Coverage 2.2. Bad Radio Coverage
The goal of this test is to evaluate the performance of candidate The goal of this test is to evaluate the performance of the candidate
congestion control algorithm when users visit part of the network congestion control algorithm when users visit part of the network
with bad radio coverage. The scenario is created by using a larger 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, cell radius than that in the previous test case. In this test case,
each user/UE in the media session is an endpoint following RTP-based each user/UE in the media session is an endpoint following RTP-based
congestion control. User arrivals follow a Poisson distribution congestion control. User arrivals follow a Poisson distribution
proportional to the length of the call, to keep the number of users proportional to the length of the call, to keep the number of users
per cell fairly constant during the evaluation period. At the per cell fairly constant during the evaluation period. At the
beginning of the simulation, there should be enough amount of time to beginning of the simulation, there should be enough time to warm up
warm-up the network. This is to avoid running the evaluation in an the network. This is to avoid running the evaluation in an empty
empty network where network nodes are having empty buffers, low network where network nodes have empty buffers and low interference
interference at the beginning of the simulation. This network at the beginning of the simulation. This network initialization
initialization period should be excluded from the evaluation period. period should be excluded from the evaluation period. Typically, the
Typically, the evaluation period starts 30 seconds after test evaluation period starts 30 seconds after test initialization.
initialization.
This test case also includes user mobility and some competing This test case also includes user mobility and some competing
traffic. The latter includes the same kind of flows (with same traffic. The latter includes the same kind of flows (with same
adaptation algorithms). adaptation algorithms).
2.2.1. Network connection 2.2.1. Network Connection
Same as defined in Section 2.1.1 Same as defined in Section 2.1.1.
2.2.2. Simulation Setup 2.2.2. Simulation Setup
The desired simulation setup is the same as the Varying Network Load The desired simulation setup is the same as the Varying Network Load
test case defined in Section 2.1 except the following changes: test case defined in Section 2.1 except for the following changes:
1. Radio environment: Same as defined in Section 2.1.2 except the Radio environment: Same as defined in Section 2.1.2 except for the
following: following:
A. Deployment and propagation model: 3GPP case 3 (see Deployment and propagation model: 3GPP case 3 (see
[HO-deploy-3GPP]) [HO-deploy-3GPP])
B. Cell radius: 577.3333 Meters Cell radius: 577.3333 meters
C. Mobility: 3km/h Mobility: 3 km/h
2. User intensity = {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3, User intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3, 7.0}
7.0}
3. Media traffic model: Same as defined in Section 2.1.2 Media traffic model: Same as defined in Section 2.1.2
4. Other traffic models: Other traffic models:
* Downlink simulation: Maximum of 2Mbps/cell (web browsing or Downlink simulation: Maximum of 2 Mbps/cell (web browsing or FTP
FTP traffic following default TCP congestion control traffic following default TCP congestion control [RFC5681])
[RFC5681])
* Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP Uplink simulation: Maximum of 1 Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681]) traffic following default TCP congestion control [RFC5681])
2.2.3. Expected behavior 2.2.3. Expected Behavior
The investigated congestion control algorithms should result in The investigated congestion control algorithms should result in
maximum possible network utilization and stability in terms of rate maximum possible network utilization and stability in terms of rate
variations, lowest possible end to end frame latency, network latency variations, lowest possible end-to-end frame latency, network
and Packet Loss Rate (PLR) at different cell load levels. latency, and Packet Loss Rate (PLR) at different cell load levels.
2.3. Desired Evaluation Metrics for cellular test cases 2.3. Desired Evaluation Metrics for Cellular Test Cases
The evaluation criteria document [I-D.ietf-rmcat-eval-criteria] The evaluation criteria document [RFC8868] defines the metrics to be
defines the metrics to be used to evaluate candidate algorithms. used to evaluate candidate algorithms. Considering the nature and
Considering the nature and distinction of cellular networks we distinction of cellular networks, we recommend that at least the
recommend that at least the following metrics be used to evaluate the following metrics be used to evaluate the performance of the
performance of the candidate algorithms: candidate algorithms:
o Average cell throughput (for all cells), shows cell utilizations. * Average cell throughput (for all cells), shows cell utilization.
o Application sending and receiving bitrate, goodput. * Application sending and receiving bitrate, goodput.
o Packet Loss Rate (PLR). * Packet Loss Rate (PLR).
o End-to-end Media frame delay. For video, this means the delay * End-to-end media frame delay. For video, this means the delay
from capture to display. from capture to display.
o Transport delay. * Transport delay.
o Algorithm stability in terms of rate variation. * Algorithm stability in terms of rate variation.
3. Wi-Fi Networks Specific Test Cases 3. Wi-Fi Networks Specific Test Cases
Given the prevalence of Internet access links over Wi-Fi, it is Given the prevalence of Internet access links over Wi-Fi, it is
important to evaluate candidate RTP-based congestion control important to evaluate candidate RTP-based congestion control
solutions over test cases that include Wi-Fi access links. Such solutions over test cases that include Wi-Fi access links. Such
evaluations should highlight the inherently different characteristics evaluations should highlight the inherently different characteristics
of Wi-Fi networks in contrast to their wired counterparts: of Wi-Fi networks in contrast to their wired counterparts:
o The wireless radio channel is subject to interference from nearby * The wireless radio channel is subject to interference from nearby
transmitters, multipath fading, and shadowing. These effects lead transmitters, multipath fading, and shadowing. These effects lead
to fluctuations in the link throughput and sometimes an error- to fluctuations in the link throughput and sometimes an error-
prone communication environment. prone communication environment.
o Available network bandwidth is not only shared over the air * Available network bandwidth is not only shared over the air
between concurrent users but also between uplink and downlink between concurrent users but also between uplink and downlink
traffic due to the half-duplex nature of the wireless transmission traffic due to the half-duplex nature of the wireless transmission
medium. medium.
o Packet transmissions over Wi-Fi are susceptible to contentions and * Packet transmissions over Wi-Fi are susceptible to contentions and
collisions over the air. Consequently, traffic load beyond a collisions over the air. Consequently, traffic load beyond a
certain utilization level over a Wi-Fi network can introduce certain utilization level over a Wi-Fi network can introduce
frequent collisions over the air and significant network overhead, frequent collisions over the air and significant network overhead,
as well as packet drops due to buffer overflow at the as well as packet drops due to buffer overflow at the
transmitters. This, in turn, leads to excessive delay, transmitters. This, in turn, leads to excessive delay,
retransmissions, packet losses and lower effective bandwidth for retransmissions, packet losses, and lower effective bandwidth for
applications. Note further that the collision-induced delay and applications. Note further that the collision-induced delay and
loss patterns are qualitatively different from those caused by loss patterns are qualitatively different from those caused by
congestion over a wired connection. congestion over a wired connection.
o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate * The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate
transmission capabilities by dynamically choosing the most transmission capabilities by dynamically choosing the most
appropriate modulation and coding scheme (MCS) for the given appropriate modulation and coding scheme (MCS) for the given
received signal strength. A different choice in the MCS Index received signal strength. A different choice in the MCS Index
leads to different physical-layer (PHY-layer) link rates and leads to different physical-layer (PHY-layer) link rates and
consequently different application-layer throughput. consequently different application-layer throughput.
o The presence of legacy devices (e.g., ones operating only in IEEE * The presence of legacy devices (e.g., ones operating only in IEEE
802.11b) at a much lower PHY-layer link rate can significantly 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 slow down the rest of a modern Wi-Fi network. As discussed in
[Heusse2003], the main reason for such anomaly is that it takes [Heusse2003], the main reason for such anomaly is that it takes
much longer to transmit the same packet over a slower link than much longer to transmit the same packet over a slower link than
over a faster link, thereby consuming a substantial portion of air over a faster link, thereby consuming a substantial portion of air
time. time.
o Handover from one Wi-Fi Access Point (AP) to another may lead to * Handover from one Wi-Fi Access Point (AP) to another may lead to
excessive packet delays and losses during the process. excessive packet delays and losses during the process.
o IEEE 802.11e has introduced the Enhanced Distributed Channel * IEEE 802.11e has introduced the Enhanced Distributed Channel
Access (EDCA) mechanism to allow different traffic categories to Access (EDCA) mechanism to allow different traffic categories to
contend for channel access using different random back-off contend for channel access using different random back-off
parameters. This mechanism is a mandatory requirement for the Wi- parameters. This mechanism is a mandatory requirement for the Wi-
Fi Multimedia (WMM) certification in Wi-Fi Alliance. It allows Fi Multimedia (WMM) certification in Wi-Fi Alliance. It allows
for prioritization of real-time application traffic such as voice for prioritization of real-time application traffic such as voice
and video over non-urgent data transmissions (e.g., file and video over non-urgent data transmissions (e.g., file
transfer). transfer).
In summary, the presence of Wi-Fi access links in different network In summary, the presence of Wi-Fi access links in different network
topologies can exert different impact on the network performance in topologies can exert different impacts on the network performance in
terms of application-layer effective throughput, packet loss rate, terms of application-layer effective throughput, packet loss rate,
and packet delivery delay. These, in turn, will influence the and packet delivery delay. These, in turn, will influence the
behavior of end-to-end real-time multimedia congestion control. behavior of end-to-end real-time multimedia congestion control.
Unless otherwise mentioned, the test cases in this section choose the Unless otherwise mentioned, the test cases in this section choose the
PHY- and MAC-layer parameters based on the IEEE 802.11n Standard. PHY- and MAC-layer parameters based on the IEEE 802.11n standard.
Statistics collected from enterprise Wi-Fi networks show that the two Statistics collected from enterprise Wi-Fi networks show that the two
dominant physical modes are 802.11n and 802.11ac, accounting for 41% dominant physical modes are 802.11n and 802.11ac, accounting for 41%
and 58% of connected devices. As Wi-Fi standards evolve over time -- and 58% of connected devices, respectively. As Wi-Fi standards
for instance, with the introduction of the emerging Wi-Fi 6 (based on evolve over time -- for instance, with the introduction of the
IEEE 802.11ax) products -- the PHY- and MAC-layer test case emerging Wi-Fi 6 (based on IEEE 802.11ax) products -- the PHY- and
specifications need to be updated accordingly to reflect such MAC-layer test case specifications need to be updated accordingly to
changes. reflect such changes.
Typically, a Wi-Fi access network connects to a wired infrastructure. Typically, a Wi-Fi access network connects to a wired infrastructure.
Either the wired or the Wi-Fi segment of the network can be the Either the wired or the Wi-Fi segment of the network can be the
bottleneck. The following sections describe basic test cases for bottleneck. The following sections describe basic test cases for
both scenarios separately. The same set of performance metrics as in both scenarios separately. The same set of performance metrics as in
[I-D.ietf-rmcat-eval-test]) should be collected for each test case. [RFC8867]) should be collected for each test case.
We recommend to carry out the test cases as defined in this document We recommend carrying out the test cases as defined in this document
using a simulator, such as [NS-2] or [NS-3]. When feasible, it is using a simulator, such as [NS-2] or [NS-3]. When feasible, it is
encouraged to perform testbed-based evaluations using Wi-Fi access encouraged to perform testbed-based evaluations using Wi-Fi access
points and endpoints running up-to-date IEEE 802.11 protocols, such 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 as 802.11ac and the emerging Wi-Fi 6, so as to verify the viability
of the candidate schemes. of the candidate schemes.
3.1. Bottleneck in Wired Network 3.1. Bottleneck in Wired Network
The test scenarios below are intended to mimic the setup of video The test scenarios below are intended to mimic the setup of video
conferencing over Wi-Fi connections from the home. Typically, the conferencing over Wi-Fi connections from the home. Typically, the
Wi-Fi home network is not congested and the bottleneck is present Wi-Fi home network is not congested, and the bottleneck is present
over the wired home access link. Although it is expected that test over the wired home access link. Although it is expected that test
evaluation results from this section are similar to those as in evaluation results from this section are similar to those in
[I-D.ietf-rmcat-eval-test], it is still worthwhile to run through [RFC8867], it is still worthwhile to run through these tests as
these tests as sanity checks. sanity checks.
3.1.1. Network topology 3.1.1. Network Topology
Figure 2 shows the network topology of Wi-Fi test cases. The test Figure 2 shows the network topology of Wi-Fi test cases. The test
contains multiple mobile nodes (MNs) connected to a common Wi-Fi contains multiple mobile nodes (MNs) connected to a common Wi-Fi AP
access point (AP) and their corresponding wired clients on fixed and their corresponding wired clients on fixed nodes (FNs). Each
nodes (FNs). Each connection carries either a RTP-based media flow connection carries either an RTP-based media flow or a TCP traffic
or a TCP traffic flow. Directions of the flows can be uplink (i.e., flow. Directions of the flows can be uplink (i.e., from mobile nodes
from mobile nodes to fixed nodes), downlink (i.e., from fixed nodes to fixed nodes), downlink (i.e., from fixed nodes to mobile nodes),
to mobile nodes), or bi-directional. The total number of or bidirectional. The total number of uplink/downlink/bidirectional
uplink/downlink/bi-directional flows for RTP-based media traffic and flows for RTP-based media traffic and TCP traffic are denoted as N
TCP traffic are denoted as N and M, respectively. and M, respectively.
Uplink Uplink
+----------------->+ +----------------->+
+------+ +------+ +------+ +------+
| MN_1 |)))) /=====| FN_1 | | MN_1 |)))) /=====| FN_1 |
+------+ )) // +------+ +------+ )) // +------+
. )) // . . )) // .
. )) // . . )) // .
. )) // . . )) // .
+------+ +----+ +-----+ +------+ +------+ +----+ +-----+ +------+
skipping to change at page 13, line 34 skipping to change at line 588
+----------+ +----+ +-----+ +----------+ +----------+ +----+ +-----+ +----------+
. )) \\ . . )) \\ .
. )) \\ . . )) \\ .
. )) \\ . . )) \\ .
+----------+ )) \\ +----------+ +----------+ )) \\ +----------+
| MN_tcp_M |))) \=====| FN_tcp_M | | MN_tcp_M |))) \=====| FN_tcp_M |
+----------+ +----------+ +----------+ +----------+
+<-----------------+ +<-----------------+
Downlink Downlink
Figure 2: Network topology for Wi-Fi test cases Figure 2: Network Topology for Wi-Fi Test Cases
3.1.2. Test/simulation setup 3.1.2. Test/Simulation Setup
o Test duration: 120s Test duration: 120 s
o Wi-Fi network characteristics: Wi-Fi network characteristics:
* Radio propagation model: Log-distance path loss propagation Radio propagation model: Log-distance path loss propagation model
model (see [NS3WiFi]) (see [NS3WiFi])
* PHY- and MAC-layer configuration: IEEE 802.11n PHY- and MAC-layer configuration: IEEE 802.11n
* MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps MCS Index at 11: Raw data rate at 52 Mbps, 16-QAM (Quadrature
amplitude modulation) and 1/2 coding rate
o Wired path characteristics: Wired path characteristics:
* Path capacity: 1Mbps Path capacity: 1 Mbps
* One-Way propagation delay: 50ms. One-way propagation delay: 50 ms
* Maximum end-to-end jitter: 30ms Maximum end-to-end jitter: 30 ms
* Bottleneck queue type: Drop tail. Bottleneck queue type: Drop tail
* Bottleneck queue size: 300ms. Bottleneck queue size: 300 ms
* Path loss ratio: 0%. Path loss ratio: 0%
o Application characteristics: Application characteristics:
* Media Traffic: Media traffic:
+ Media type: Video Media type: Video
+ Media direction: See Section 3.1.3 Media direction: See Section 3.1.3
+ Number of media sources (N): See Section 3.1.3 Number of media sources (N): See Section 3.1.3
+ Media timeline: Media timeline:
- Start time: 0s. Start time: 0 s
- End time: 119s. End time: 119 s
* Competing traffic: Competing traffic:
+ Type of sources: long-lived TCP or CBR over UDP Type of sources: Long-lived TCP or CBR over UDP
+ Traffic direction: See Section 3.1.3 Traffic direction: See Section 3.1.3
+ Number of sources (M): See Section 3.1.3 Number of sources (M): See Section 3.1.3
+ Congestion control: Default TCP congestion control [RFC5681] Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP. or CBR traffic over UDP
+ Traffic timeline: See Section 3.1.3 Traffic timeline: See Section 3.1.3
3.1.3. Typical test scenarios 3.1.3. Typical Test Scenarios
o Single uplink RTP-based media flow: N=1 with uplink direction and Single uplink RTP-based media flow: N=1 with uplink direction and
M=0. M=0.
o One pair of bi-directional RTP-based media flows: N=2 (i.e., one One pair of bidirectional RTP-based media flows: N=2 (i.e., one
uplink flow and one downlink flow); M=0. uplink flow and one downlink flow); M=0.
o One pair of bi-directional RTP-based media flows: N=2; one uplink One pair of bidirectional RTP-based media flows: N=2; one uplink on-
on-off CBR flow over UDP: M=1 (uplink). The CBR flow has ON time off CBR flow over UDP: M=1 (uplink). The CBR flow has ON time at
at t=0s-60s and OFF time at t=60s-119s. t=0s-60s and OFF time at t=60s-119s.
o One pair of bi-directional RTP-based media flows: N=2; one uplink One pair of bidirectional RTP-based media flows: N=2; one uplink
off-on CBR flow over UDP: M=1 (uplink). The CBR flow has OFF time off-on CBR flow over UDP: M=1 (uplink). The CBR flow has OFF time
at t=0s-60s and ON time at t=60s-119s. at t=0s-60s and ON time at t=60s-119s.
o One RTP-based media flow competing against one long-live TCP flow One RTP-based media flow competing against one long-lived TCP flow
in the uplink direction: N=1 (uplink) and M = 1(uplink). The TCP in the uplink direction: N=1 (uplink) and M=1 (uplink). The TCP
flow has start time at t=0s and end time at t=119s. flow has start time at t=0s and end time at t=119s.
3.1.4. Expected behavior 3.1.4. Expected Behavior
o Single uplink RTP-based media flow: the candidate algorithm is Single uplink RTP-based media flow: The candidate algorithm is
expected to detect the path capacity constraint, to converge to expected to detect the path capacity constraint, to converge to
the bottleneck link capacity, and to adapt the flow to avoid the bottleneck link capacity, and to adapt the flow to avoid
unwanted oscillations when the sending bit rate is approaching the unwanted oscillations when the sending bit rate is approaching the
bottleneck link capacity. No excessive oscillations in the media bottleneck link capacity. No excessive oscillations in the media
rate should be present. rate should be present.
o Bi-directional RTP-based media flows: the candidate algorithm is Bidirectional RTP-based media flows: The candidate algorithm is
expected to converge to the bottleneck capacity of the wired path expected to converge to the bottleneck capacity of the wired path
in both directions despite the presence of measurement noise over in both directions despite the presence of measurement noise over
the Wi-Fi connection. In the presence of background TCP or CBR the Wi-Fi connection. In the presence of background TCP or CBR
over UDP traffic, the rate of RTP-based media flows should adapt over UDP traffic, the rate of RTP-based media flows should adapt
promptly to the arrival and departure of background traffic flows. promptly to the arrival and departure of background traffic flows.
o One RTP-based media flow competing with long-live TCP flow in the One RTP-based media flow competing with long-lived TCP flow in the
uplink direction: the candidate algorithm is expected to avoid uplink direction: The candidate algorithm is expected to avoid
congestion collapse and to stabilize at a fair share of the congestion collapse and to stabilize at a fair share of the
bottleneck link capacity. bottleneck link capacity.
3.2. Bottleneck in Wi-Fi Network 3.2. Bottleneck in Wi-Fi Network
The test cases in this section assume that the wired segment along The test cases in this section assume that the wired segment along
the media path is well-provisioned whereas the bottleneck exists over the media path is well-provisioned, whereas the bottleneck exists
the Wi-Fi access network. This is to mimic the application scenarios over the Wi-Fi access network. This is to mimic the application
typically encountered by users in an enterprise environment or at a scenarios typically encountered by users in an enterprise environment
coffee house. or at a coffee house.
3.2.1. Network topology 3.2.1. Network Topology
Same as defined in Section 3.1.1 Same as defined in Section 3.1.1.
3.2.2. Test/simulation setup 3.2.2. Test/Simulation Setup
o Test duration: 120s Test duration: 120 s
o Wi-Fi network characteristics: Wi-Fi network characteristics:
* Radio propagation model: Log-distance path loss propagation Radio propagation model: Log-distance path loss propagation model
model (see [NS3WiFi]) (see [NS3WiFi])
* PHY- and MAC-layer configuration: IEEE 802.11n PHY- and MAC-layer configuration: IEEE 802.11n
* MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps MCS Index at 11: Raw data rate at 52 Mbps, 16-QAM (Quadrature
amplitude modulation) and 1/2 coding rate
o Wired path characteristics: Wired path characteristics:
* Path capacity: 100Mbps. Path capacity: 100 Mbps
* One-Way propagation delay: 50ms. One-Way propagation delay: 50 ms
* Maximum end-to-end jitter: 30ms. Maximum end-to-end jitter: 30 ms
* Bottleneck queue type: Drop tail. Bottleneck queue type: Drop tail
* Bottleneck queue size: 300ms. Bottleneck queue size: 300 ms
* Path loss ratio: 0%. Path loss ratio: 0%
o Application characteristics: Application characteristics
* Media Traffic: Media traffic:
+ Media type: Video Media type: Video
+ Media direction: See Section 3.2.3. Media direction: See Section 3.2.3
+ Number of media sources (N): See Section 3.2.3. Number of media sources (N): See Section 3.2.3
+ Media timeline: Media timeline:
- Start time: 0s. Start time: 0 s
- End time: 119s. End time: 119 s
* Competing traffic: Competing traffic:
+ Type of sources: long-lived TCP or CBR over UDP. Type of sources: long-lived TCP or CBR over UDP
+ Number of sources (M): See Section 3.2.3. Number of sources (M): See Section 3.2.3
+ Traffic direction: See Section 3.2.3. Traffic direction: See Section 3.2.3
+ Congestion control: Default TCP congestion control [RFC5681] Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP. or CBR traffic over UDP
+ Traffic timeline: See Section 3.2.3. Traffic timeline: See Section 3.2.3
3.2.3. Typical test scenarios 3.2.3. Typical Test Scenarios
This section describes a few test scenarios that are deemed as This section describes a few test scenarios that are deemed as
important for understanding the behavior of a candidate RTP-based important for understanding the behavior of a candidate RTP-based
congestion control scheme over a Wi-Fi network. congestion control scheme over a Wi-Fi network.
a. Multiple RTP-based media flows sharing the wireless downlink: Multiple RTP-based media flows sharing the wireless downlink: N=16
N=16 (all downlink); M = 0. This test case is for studying the (all downlink); M=0. This test case is for studying the impact of
impact of contention on the multiple concurrent media flows. For contention on the multiple concurrent media flows. For an 802.11n
an 802.11n network, given the MCS Index of 11 and the network, given the MCS Index of 11 and the corresponding link rate
corresponding link rate of 52Mbps, the total application-layer of 52 Mbps, the total application-layer throughput (assuming
throughput (assuming reasonable distance, low interference and reasonable distance, low interference, and infrequent contentions
infrequent contentions caused by competing streams) is around caused by competing streams) is around 20 Mbps. A total of N=16
20Mbps. A total of N=16 RTP-based media flows (with a maximum RTP-based media flows (with a maximum rate of 1.5 Mbps each) are
rate of 1.5Mbps each) are expected to saturate the wireless expected to saturate the wireless interface in this experiment.
interface in this experiment. Evaluation of a given candidate Evaluation of a given candidate scheme should focus on whether the
scheme should focus on whether the downlink media flows can downlink media flows can stabilize at a fair share of the total
stabilize at a fair share of the total application-layer application-layer throughput.
throughput.
b. Multiple RTP-based media flows sharing the wireless uplink: N = Multiple RTP-based media flows sharing the wireless uplink: N=16
16 (all uplink); M = 0. When multiple clients attempt to (all uplink); M=0. When multiple clients attempt to transmit
transmit media packets uplink over the Wi-Fi network, they media packets uplink over the Wi-Fi network, they introduce more
introduce more frequent contentions and potential collisions. frequent contentions and potential collisions. Per-flow
Per-flow throughput is expected to be lower than that in the throughput is expected to be lower than that in the previous
previous downlink-only scenario. Evaluation of a given candidate downlink-only scenario. Evaluation of a given candidate scheme
scheme should focus on whether the uplink flows can stabilize at should focus on whether the uplink flows can stabilize at a fair
a fair share of the total application-layer throughput. share of the total application-layer throughput.
c. Multiple bi-directional RTP-based media flows: N = 16 (8 uplink Multiple bidirectional RTP-based media flows: N=16 (8 uplink and 8
and 8 downlink); M = 0. The goal of this test is to evaluate the downlink); M=0. The goal of this test is to evaluate the
performance of the candidate scheme in terms of bandwidth performance of the candidate scheme in terms of bandwidth fairness
fairness between uplink and downlink flows. between uplink and downlink flows.
d. Multiple bi-directional RTP-based media flows with on-off CBR Multiple bidirectional RTP-based media flows with on-off CBR
traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5 traffic over UDP: N=16 (8 uplink and 8 downlink); M=5 (uplink). The
(uplink). The goal of this test is to evaluate the adaptation goal of this test is to evaluate the adaptation behavior of the
behavior of the candidate scheme when its available bandwidth candidate scheme when its available bandwidth changes due to the
changes due to the departure of background traffic. The departure of background traffic. The background traffic consists
background traffic consists of several (e.g., M=5) CBR flows of several (e.g., M=5) CBR flows transported over UDP. These
transported over UDP. These background flows are ON at time background flows are ON at time t=0-60s and OFF at time t=61-120s.
t=0-60s and OFF at time t=61-120s.
e. Multiple bi-directional RTP-based media flows with off-on CBR Multiple bidirectional RTP-based media flows with off-on CBR
traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5 traffic over UDP: N=16 (8 uplink and 8 downlink); M=5 (uplink). The
(uplink). The goal of this test is to evaluate the adaptation goal of this test is to evaluate the adaptation behavior of the
behavior of the candidate scheme when its available bandwidth candidate scheme when its available bandwidth changes due to the
changes due to the arrival of background traffic. The background arrival of background traffic. The background traffic consists of
traffic consists of several (e.g., M=5) parallel CBR flows several (e.g., M=5) parallel CBR flows transported over UDP.
transported over UDP. These background flows are OFF at time These background flows are OFF at time t=0-60s and ON at times
t=0-60s and ON at times t=61-120s. t=61-120s.
f. Multiple bi-directional RTP-based media flows in the presence of Multiple bidirectional RTP-based media flows in the presence of
background TCP traffic: N=16 (8 uplink and 8 downlink); M = 5 background TCP traffic: N=16 (8 uplink and 8 downlink); M=5
(uplink). The goal of this test is to evaluate how RTP-based (uplink). The goal of this test is to evaluate how RTP-based
media flows compete against TCP over a congested Wi-Fi network media flows compete against TCP over a congested Wi-Fi network for
for a given candidate scheme. TCP flows have start time at t=40s a given candidate scheme. TCP flows have start time at t=40s and
and end time at t=80s. end time at t=80s.
g. Varying number of RTP-based media flows: A series of tests can be Varying number of RTP-based media flows: A series of tests can be
carried out for the above test cases with different values of N, 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 e.g., N=[4, 8, 12, 16, 20]. The goal of this test is to evaluate
evaluate how a candidate scheme responds to varying traffic load/ how a candidate scheme responds to varying traffic load/demand
demand over a congested Wi-Fi network. The start times of the over a congested Wi-Fi network. The start times of the media
media flows are randomly distributes within a window of t=0-10s; flows are randomly distributed within a window of t=0-10s; their
their end times are randomly distributed within a window of end times are randomly distributed within a window of t=110-120s.
t=110-120s.
3.2.4. Expected behavior 3.2.4. Expected Behavior
o Multiple downlink RTP-based media flows: each media flow is Multiple downlink RTP-based media flows: Each media flow is expected
expected to get its fair share of the total bottleneck link to get its fair share of the total bottleneck link bandwidth.
bandwidth. Overall bandwidth usage should not be significantly Overall bandwidth usage should not be significantly lower than
lower than that experienced by the same number of concurrent that experienced by the same number of concurrent downlink TCP
downlink TCP flows. In other words, the behavior of multiple flows. In other words, the behavior of multiple concurrent TCP
concurrent TCP flows will be used as a performance benchmark for flows will be used as a performance benchmark for this test
this test scenario. The end-to-end delay and packet loss ratio scenario. The end-to-end delay and packet loss ratio experienced
experienced by each flow should be within an acceptable range for by each flow should be within an acceptable range for real-time
real-time multimedia applications. multimedia applications.
o Multiple uplink RTP-based media flows: overall bandwidth usage by Multiple uplink RTP-based media flows: Overall bandwidth usage by
all media flows should not be significantly lower than that all media flows should not be significantly lower than that
experienced by the same number of concurrent uplink TCP flows. In experienced by the same number of concurrent uplink TCP flows. In
other words, the behavior of multiple concurrent TCP flows will be other words, the behavior of multiple concurrent TCP flows will be
used as a performance benchmark for this test scenario. used as a performance benchmark for this test scenario.
o Multiple bi-directional RTP-based media flows with dynamic Multiple bidirectional RTP-based media flows with dynamic
background traffic carrying CBR flows over UDP: the media flows background traffic carrying CBR flows over UDP: The media flows are
are expected to adapt in a timely fashion to the changes in expected to adapt in a timely fashion to the changes in available
available bandwidth introduced by the arrival/departure of bandwidth introduced by the arrival/departure of background
background traffic. traffic.
o Multiple bi-directional RTP-based media flows with dynamic Multiple bidirectional RTP-based media flows with dynamic
background traffic over TCP: during the presence of TCP background background traffic over TCP: During the presence of TCP background
flows, the overall bandwidth usage by all media flows should not flows, the overall bandwidth usage by all media flows should not
be significantly lower than those achieved by the same number of be significantly lower than those achieved by the same number of
bi-directional TCP flows. In other words, the behavior of bidirectional TCP flows. In other words, the behavior of multiple
multiple concurrent TCP flows will be used as a performance concurrent TCP flows will be used as a performance benchmark for
benchmark for this test scenario. All downlink media flows are this test scenario. All downlink media flows are expected to
expected to obtain similar bandwidth as each other. The obtain similar bandwidth as each other. The throughput of each
throughput of each media flow is expected to decrease upon the media flow is expected to decrease upon the arrival of TCP
arrival of TCP background traffic and, conversely, increase upon background traffic and, conversely, increase upon their departure.
their departure. Both reactions should occur in a timely fashion, Both reactions should occur in a timely fashion, for example,
for example, within 10s of seconds. within 10s of seconds.
o Varying number of bi-directional RTP-based media flows: the test Varying number of bidirectional RTP-based media flows: The test
results for varying values of N -- while keeping all other results for varying values of N -- while keeping all other
parameters constant -- is expected to show steady and stable per- parameters constant -- is expected to show steady and stable per-
flow throughput for each value of N. The average throughput of flow throughput for each value of N. The average throughput of
all media flows is expected to stay constant around the maximum all media flows is expected to stay constant around the maximum
rate when N is small, then gradually decrease with increasing rate when N is small, then gradually decrease with increasing
value of N till it reaches the minimum allowed rate, beyond which value of N till it reaches the minimum allowed rate, beyond which
the offered load to the Wi-Fi network exceeds its capacity (i.e., the offered load to the Wi-Fi network exceeds its capacity (i.e.,
with a very large value of N). with a very large value of N).
3.3. Other Potential Test Cases 3.3. Other Potential Test Cases
skipping to change at page 19, line 46 skipping to change at line 884
classes (or Access Categories). RTP-based real-time media flows classes (or Access Categories). RTP-based real-time media flows
should achieve better performance in terms of lower delay and fewer should achieve better performance in terms of lower delay and fewer
packet losses with EDCA/WMM enabled when competing against non- packet losses with EDCA/WMM enabled when competing against non-
interactive background traffic such as file transfers. When most of interactive background traffic such as file transfers. When most of
the traffic over Wi-Fi is dominated by media, however, turning on WMM the traffic over Wi-Fi is dominated by media, however, turning on WMM
may degrade performance since all media flows now attempt to access may degrade performance since all media flows now attempt to access
the wireless transmission medium more aggressively, thereby causing the wireless transmission medium more aggressively, thereby causing
more frequent collisions and collision-induced losses. This is a more frequent collisions and collision-induced losses. This is a
topic worthy of further investigation. topic worthy of further investigation.
3.3.2. Effect of heterogeneous link rates 3.3.2. Effect of Heterogeneous Link Rates
As discussed in [Heusse2003], the presence of clients operating over As discussed in [Heusse2003], the presence of clients operating over
slow PHY-layer link rates (e.g., a legacy 802.11b device) connected slow PHY-layer link rates (e.g., a legacy 802.11b device) connected
to a modern network may adversely impact the overall performance of to a modern network may adversely impact the overall performance of
the network. Additional test cases can be devised to evaluate the the network. Additional test cases can be devised to evaluate the
effect of clients with heterogeneous link rates on the performance of effect of clients with heterogeneous link rates on the performance of
the candidate congestion control algorithm. Such test cases, for the candidate congestion control algorithm. Such test cases, for
instance, can specify that the PHY-layer link rates for all clients instance, can specify that the PHY-layer link rates for all clients
span over a wide range (e.g., 2Mbps to 54Mbps) for investigating its span over a wide range (e.g., 2 Mbps to 54 Mbps) for investigating
effect on the congestion control behavior of the real-time its effect on the congestion control behavior of the real-time
interactive applications. interactive applications.
4. IANA Considerations 4. IANA Considerations
This memo includes no request to IANA. This document has no IANA actions.
5. Security Considerations 5. Security Considerations
The security considerations in [I-D.ietf-rmcat-eval-criteria] and the The security considerations in [RFC8868] and the relevant congestion
relevant congestion control algorithms apply. The principles for control algorithms apply. The principles for congestion control are
congestion control are described in [RFC2914], and in particular, any described in [RFC2914], and in particular, any new method must
new method must implement safeguards to avoid congestion collapse of implement safeguards to avoid congestion collapse of the Internet.
the Internet.
Given the difficulty of deterministic wireless testing, it is Given the difficulty of deterministic wireless testing, it is
recommended and expected that the tests described in this document recommended and expected that the tests described in this document
would be done via simulations. However, in the case where these test would be done via simulations. However, in the case where these test
cases are carried out in a testbed setting, the evaluation should cases are carried out in a testbed setting, the evaluation should
take place in a controlled lab environment. In the testbed, the take place in a controlled lab environment. In the testbed, the
applications, simulators and network nodes ought to be well-behaved applications, simulators, and network nodes ought to be well-behaved
and should not impact the desired results. It is important to take and should not impact the desired results. It is important to take
appropriate caution to avoid leaking non-responsive traffic with appropriate caution to avoid leaking nonresponsive traffic with
unproven congestion avoidance behavior onto the open Internet. unproven congestion avoidance behavior onto the open Internet.
6. Contributors 6. References
The following individuals contributed to the design, implementation,
and verification of the proposed test cases during earlier stages of
this work. They have helped to validate and substantially improve
this specification.
Ingemar Johansson, <ingemar.s.johansson@ericsson.com> of Ericsson AB
contributing to the description and validation of cellular test cases
during the earlier stage of this draft.
Wei-Tian Tan, <dtan2@cisco.com>, of Cisco Systems designed and set up
a Wi-Fi testbed for evaluating parallel video conferencing streams,
based upon which proposed Wi-Fi test cases are described. He also
recommended additional test cases to consider, such as the impact of
EDCA/WMM usage.
Michael A. Ramalho, <mar42@cornell.edu> of AcousticComms Consulting
(previously at Cisco Systems) applied learnings from Cisco's internal
experimentation to the early versions of the draft. He also worked
on validating the proposed test cases in a VM-based lab setting.
7. Acknowledgments
The authors would like to thank Tomas Frankkila, Magnus Westerlund,
Kristofer Sandlund, Sergio Mena de la Cruz, and Mirja Kuehlewind for
their valuable inputs and review comments regarding this draft.
8. References
8.1. Normative References 6.1. Normative References
[HO-deploy-3GPP] [HO-deploy-3GPP]
TS 25.814, 3GPP., "Physical layer aspects for evolved 3GPP, "Physical layer aspects for evolved Universal
Universal Terrestrial Radio Access (UTRA)", October 2006, Terrestrial Radio Access (UTRA)", TS 25.814, October 2006,
<http://www.3gpp.org/ftp/specs/ <http://www.3gpp.org/ftp/specs/
archive/25_series/25.814/25814-710.zip>. archive/25_series/25.814/25814-710.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-13 (work in progress), March 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] [IEEE802.11]
IEEE, "Standard for Information technology-- IEEE, "Standard for Information technology--
Telecommunications and information exchange between Telecommunications and information exchange between
systems Local and metropolitan area networks--Specific systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications", 2012. (MAC) and Physical Layer (PHY) Specifications",
IEEE 802.11-2012,
<https://ieeexplore.ieee.org/document/7786995>.
[NS3WiFi] "Wi-Fi Channel Model in ns-3 Simulator", [NS3WiFi] "ns3::YansWifiChannel Class Reference",
<https://www.nsnam.org/doxygen/ <https://www.nsnam.org/doxygen/
classns3_1_1_yans_wifi_channel.html>. classns3_1_1_yans_wifi_channel.html>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009, Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>. <https://www.rfc-editor.org/info/rfc5681>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8867] Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, Cases for Evaluating Congestion Control for Interactive
May 2017, <https://www.rfc-editor.org/info/rfc8174>. Real-Time Media", RFC 8867, DOI 10.17487/RFC8867, January
2021, <https://www.rfc-editor.org/info/rfc8867>.
8.2. Informative References [RFC8868] Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion
Control for Interactive Real-Time Media", RFC 8868,
DOI 10.17487/RFC8868, January 2021,
<https://www.rfc-editor.org/info/rfc8868>.
6.2. Informative References
[Heusse2003] [Heusse2003]
Heusse, M., Rousseau, F., Berger-Sabbatel, G., and A. Heusse, M., Rousseau, F., Berger-Sabbatel, G., and A.
Duda, "Performance anomaly of 802.11b", in Proc. 23th Duda, "Performance anomaly of 802.11b", IEEE INFOCOM 2003,
Annual Joint Conference of the IEEE Computer and Twenty-second Annual Joint Conference of the IEEE Computer
Communications Societies, (INFOCOM'03), March 2003. and Communications Societies,
DOI 10.1109/INFCOM.2003.1208921, March 2003,
<https://ieeexplore.ieee.org/document/1208921>.
[HO-def-3GPP] [HO-def-3GPP]
TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications", 3GPP, "Vocabulary for 3GPP Specifications", 3GPP
December 2009, <http://www.3gpp.org/ftp/specs/ TS 21.905, December 2009, <http://www.3gpp.org/ftp/specs/
archive/21_series/21.905/21905-940.zip>. archive/21_series/21.905/21905-940.zip>.
[HO-LTE-3GPP] [HO-LTE-3GPP]
TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC); 3GPP, "Evolved Universal Terrestrial Radio Access
Protocol specification", December 2011, (E-UTRA); Radio Resource Control (RRC); Protocol
specification", 3GPP TS 36.331, December 2011,
<http://www.3gpp.org/ftp/specs/ <http://www.3gpp.org/ftp/specs/
archive/36_series/36.331/36331-990.zip>. archive/36_series/36.331/36331-990.zip>.
[HO-UMTS-3GPP] [HO-UMTS-3GPP]
TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol 3GPP, "Radio Resource Control (RRC); Protocol
specification", December 2011, specification", 3GPP TS 25.331, December 2011,
<http://www.3gpp.org/ftp/specs/ <http://www.3gpp.org/ftp/specs/
archive/25_series/25.331/25331-990.zip>. archive/25_series/25.331/25331-990.zip>.
[NS-2] "ns-2", December 2014, [NS-2] "ns-2", December 2014,
<http://nsnam.sourceforge.net/wiki/index.php/Main_Page>. <http://nsnam.sourceforge.net/wiki/index.php/Main_Page>.
[NS-3] "ns-3 Network Simulator", <https://www.nsnam.org/>. [NS-3] "ns-3 Network Simulator", <https://www.nsnam.org/>.
[QoS-3GPP] [QoS-3GPP] 3GPP, "Policy and charging control architecture", 3GPP
TS 23.203, 3GPP., "Policy and charging control TS 23.203, June 2011, <http://www.3gpp.org/ftp/specs/
architecture", June 2011, <http://www.3gpp.org/ftp/specs/
archive/23_series/23.203/23203-990.zip>. archive/23_series/23.203/23203-990.zip>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000, RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>. <https://www.rfc-editor.org/info/rfc2914>.
Contributors
The following individuals contributed to the design, implementation,
and verification of the proposed test cases during earlier stages of
this work. They have helped to validate and substantially improve
this specification.
Ingemar Johansson <ingemar.s.johansson@ericsson.com> of Ericsson AB
contributed to the description and validation of cellular test cases
during the earlier stage of this document.
Wei-Tian Tan <dtan2@cisco.com> of Cisco Systems designed and set up a
Wi-Fi testbed for evaluating parallel video conferencing streams,
based upon which proposed Wi-Fi test cases are described. He also
recommended additional test cases to consider, such as the impact of
EDCA/WMM usage.
Michael A. Ramalho <mar42@cornell.edu> of AcousticComms Consulting
(previously at Cisco Systems) applied lessons from Cisco's internal
experimentation to the draft versions of the document. He also
worked on validating the proposed test cases in a virtual-machine-
based lab setting.
Acknowledgments
The authors would like to thank Tomas Frankkila, Magnus Westerlund,
Kristofer Sandlund, Sergio Mena de la Cruz, and Mirja K├╝hlewind for
their valuable inputs and review comments regarding this document.
Authors' Addresses Authors' Addresses
Zaheduzzaman Sarker Zaheduzzaman Sarker
Ericsson AB Ericsson AB
Laboratoriegraend 11 Torshamnsgatan 23
Luleae 97753 SE-164 83 Stockholm
Sweden Sweden
Phone: +46 107173743 Phone: +46 10 717 37 43
Email: zaheduzzaman.sarker@ericsson.com Email: zaheduzzaman.sarker@ericsson.com
Xiaoqing Zhu Xiaoqing Zhu
Cisco Systems Cisco Systems
12515 Research Blvd., Building 4 Building 4
Austin, TX 78759 12515 Research Blvd
USA Austin, TX 78759
United States of America
Email: xiaoqzhu@cisco.com Email: xiaoqzhu@cisco.com
Jiantao Fu Jiantao Fu
Cisco Systems Cisco Systems
771 Alder Drive 771 Alder Drive
Milpitas, CA 95035 Milpitas, CA 95035
USA United States of America
Email: jianfu@cisco.com Email: jianfu@cisco.com
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