draft-ietf-rmcat-wireless-tests-08.txt   draft-ietf-rmcat-wireless-tests-09.txt 
Network Working Group Z. Sarker Network Working Group Z. Sarker
Internet-Draft I. Johansson Internet-Draft I. Johansson
Intended status: Informational Ericsson AB Intended status: Informational Ericsson AB
Expires: January 6, 2020 X. Zhu Expires: August 30, 2020 X. Zhu
J. Fu J. Fu
W. Tan W. Tan
M. Ramalho
Cisco Systems Cisco Systems
July 5, 2019 M. Ramalho
AcousticComms
February 27, 2020
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-08 draft-ietf-rmcat-wireless-tests-09
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 such applications typically depends on a well- performance of these applications typically depends on a well-
functioning congestion control algorithm. To ensure 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 such document describes test cases for evaluating performances of
congestion control algorithms over LTE and Wi-Fi networks. candidate congestion control algorithms over cellular and Wi-Fi
networks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 6, 2020. This Internet-Draft will expire on August 30, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 40 skipping to change at page 2, line 45
4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13 4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13
4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14
4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15 4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15
4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15 4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15
4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15
4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15 4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15
4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17 4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17
4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18 4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18
4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19 4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19
4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19 4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19
4.3.2. Effects of Legacy 802.11b Devices . . . . . . . . . . 19 4.3.2. Effect of heterogeneous link rates . . . . . . . . . 19
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 8.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 20 8.2. Informative References . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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 part of the Internet. Mobile devices connected to the integral and increasingly more significant part of the Internet.
wireless networks account for an increasingly more significant Typical application scenarios for interactive multimedia
portion of the media traffic over the Internet. Application communication over wireless include from video conferencing calls in
scenarios range from video conferencing calls in a bus or train to a bus or train as well as live media streaming at home. It is well
media consumption by someone on a living room couch. It is well
known that the characteristics and technical challenges for known that the characteristics and technical challenges for
supporting multimedia services over wireless are very different from supporting multimedia services over wireless are very different from
those of providing the same service over a wired network. Even those of providing the same service over a wired network. Although
though basic test cases for evaluating RTP-based congestion control the basic test cases as defined in [I-D.ietf-rmcat-eval-test] have
schemes as defined in [I-D.ietf-rmcat-eval-test] have covered many covered many common effects of network impairments for evaluating
effects of the impairments common to both wired and wireless RTP-based congestion control schemes, they remain to be tested over
networks, there remain characteristics and dynamics unique to a given characteristics and dynamics unique to a given wireless environment.
wireless environment. For example, in LTE networks, the base station For example, in cellular networks, the base station maintains
maintains individual queues per radio bearer per user hence it leads individual queues per radio bearer per user hence it leads to a
to a different nature of interactions between traffic flows of different nature of interactions between traffic flows of different
different users. This contrasts with wired networks, where traffic users. This contrasts with the wired network setting where traffic
flows from all users share the same queue. Furthermore, user flows from all users share the same queue. Furthermore, user
mobility patterns in a cellular network differ from those in a Wi-Fi mobility patterns in a cellular network differ from those in a Wi-Fi
network. Therefore, it is important to evaluate the performance of network. Therefore, it is important to evaluate the performance of
proposed candidate RTP-based congestion control solutions over proposed candidate RTP-based congestion control solutions over
cellular mobile networks and over Wi-Fi networks respectively. cellular mobile networks and over Wi-Fi networks respectively.
RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria] The draft [I-D.ietf-rmcat-eval-criteria] provides the guideline for
provides the guideline 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 networks such as LTE networks targeting cellular and Wi-Fi networks.
and Wi-Fi networks.
2. Terminologies 2. Terminologies
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Cellular Network Specific Test Cases 3. 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 amount 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 network links or radio links will destination and vice versa. These radio links will often act as a
often act as a bottleneck for the rest of the network and will bottleneck for the rest of the network and will eventually lead to
eventually lead to excessive delays or packet drops. An efficient excessive delays or packet drops. An efficient retransmission or
retransmission or link adaptation mechanism can reduce the packet link adaptation mechanism can reduce the packet loss probability but
loss probability but there will still be some packet losses and delay there will remain some packet losses and delay variations. Moreover,
variations. Moreover, with increased cell load or handover to a with increased cell load or handover to a congested cell, congestion
congested cell, congestion in the transport network will become even in the transport network will become even worse. Besides, there
worse. Besides, there are certain characteristics which make the exist certain characteristics that distinguish the cellular network
cellular network different from and more challenging than other types from other wireless access networks such as Wi-Fi. In a cellular
of access networks such as Wi-Fi and wired network. In a cellular
network -- network --
o The bottleneck is often a shared link with relatively few users. 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 * The cost per bit over the shared link varies over time and is
different for different users. different for different users.
* Leftover/unused resource can be consumed by other greedy users. * Leftover/unused resources can be consumed by other greedy
users.
o Queues are always per radio bearer hence each user can have many o Queues are always per radio bearer hence each user can have many
of such queues. such queues.
o Users can experience both Inter and Intra Radio Access Technology o 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 o 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. o The network part decides how much the user can transmit.
o The cellular network has variable link capacity per user o The cellular network has variable link capacity per user.
* Can vary as fast as a period of milliseconds. * It can vary as fast as a period of milliseconds.
* Depends on many factors (such as distance, speed, interference, * It depends on many factors (such as distance, speed,
different flows). interference, different flows).
* 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 o Both Quality of Service (QoS) and non-QoS radio bearers can be
used. used.
Hence, a real-time communication application operating in such 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, abrupt changes in bandwidth (both short term and long term) due
to handover, network load and bad radio coverage. Even though 3GPP to handover, network load and bad radio coverage. Even though 3GPP
define QoS bearers [QoS-3GPP] to ensure high-quality user experience, has defined QoS bearers [QoS-3GPP] to ensure high-quality user
adaptive real-time applications are desired. experience, it is still preferable for real-time applications to
behave in an adaptive manner.
Different mobile operators deploy their own cellular network 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 2G, EDGE, 3G and 4G radio access mobile operator network includes 2G, EDGE, 3G and 4G radio access
technologies. Looking at the specifications of such radio technologies. Looking at the specifications of such radio
technologies it is evident that only 3G and 4G radio technologies can technologies it is evident that only the more recent radio
support the high bandwidth requirements from real-time interactive technologies can support the high bandwidth requirements from real-
video applications. The future real-time interactive application time interactive video applications. The future real-time
will impose even greater demand on cellular network performance which interactive application will impose even greater demand on cellular
makes 4G (and beyond radio technologies) more suitable access network performance which makes 4G (and beyond) radio technologies
technology for such genre of application. more suitable for such genre of application.
The key factors to define test cases for cellular networks are The key factors in defining test cases for cellular networks are:
o Shared and varying link capacity o Shared and varying link capacity
o Mobility o Mobility
o Handover o Handover
However, for cellular networks, it is very hard to separate such However, these factors are typically highly correlated in a cellular
events from one another as these events are heavily related. Hence network. Therefore, instead of devising separate test cases for
instead of devising separate test cases for all those important individual important events, we have divided the test case into two
events, we have divided the test case into two categories. It should categories. It should be noted that the goal of the following test
be noted that the goal of the following test cases is to evaluate the cases is to evaluate the performance of candidate algorithms over the
performance of candidate algorithms over the radio interface of the radio interface of the cellular network. Hence it is assumed that
cellular network. Hence it is assumed that the radio interface is the radio interface is the bottleneck link between the communicating
the bottleneck link between the communicating peers and that the core peers and that the core network does not introduce any extra
network does not add any extra congestion in the path. Also, the congestion along the path. Consequently, this draft has kept as out
combination of multiple access technologies such as one user has LTE of scope the combination of multiple access technologies involving
connection and another has Wi-Fi connection is kept out of the scope both cellular and Wi-Fi users. In this latter case the shared
of this document. However, later those additional scenarios can also bottleneck is likely at the wired backhaul link. These test cases
be added in this list of test cases. While defining the test cases further assume a typical real-time telephony scenario where one real-
we assumed a typical real-time telephony scenario over cellular time session consists of one voice stream and one video stream.
networks where one real-time session consists of one voice stream and
one video stream.
Even though it is possible to carry out tests over operational LTE Even though it is possible to carry out tests over operational
(and 5G) networks, and actually such tests are already available cellular networks (e.g., LTE/5G), and actually such tests are already
today, these tests cannot in the general case be carried out in a available today, these tests cannot in general be carried out in a
deterministic fashion or to ensure repeatability. The main reason is deterministic fashion to ensure repeatability. The main reason is
that these networks are in the control of cellular operators and that these networks are controlled by cellular operators and there
there exist various amounts of competing traffic in the same cell(s). exist various amounts of competing traffic in the same cell(s). In
In practice, it is only in underground mines that one can carry out practice, it is only in underground mines that one can carry out near
near deterministic testing. Even there, it is not guaranteed either deterministic testing. Even there, it is not guaranteed either as
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 an LTE network simulator is used for the test cases defined in that a cellular network simulator is used for the test cases defined
this document, for example --- NS-3 LTE simulator [LTE-simulator]. in this document, for example -- the LTE simulator in [NS-3].
3.1. Varying Network Load 3.1. 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 a.k.a.
User Equipments (UEs) during the simulation. In this test case, each User Equipments (UEs) during the simulation. In this test case, each
of the user/UE in the media session is an RMCAT compliant endpoint. user/UE in the media session is an endpoint following RTP-based
The arrival of users follows a Poisson distribution proportional to congestion control. User arrivals follow a Poisson distribution
the length of the call so as to keep the number of users per cell proportional to the length of the call, to keep the number of users
fairly constant during the evaluation period. At the beginning of per cell fairly constant during the evaluation period. At the
the simulation, there should be enough time to warm-up the network. beginning of the simulation, there should be enough time to warm-up
This is to avoid running the evaluation in an empty network where the network. This is to avoid running the evaluation in an empty
network nodes are having empty buffers, low interference at the network where network nodes are having empty buffers, low
beginning of the simulation. This network initialization period is interference at the beginning of the simulation. This network
therefore excluded from the evaluation period. initialization period should be excluded from the evaluation period.
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 same kind of flows (with same traffic. The latter includes both the same types of flows (with same
adaptation algorithms) and different kind of flows (with different adaptation algorithms) and different types of flows (with different
services and congestion control schemes). The investigated services and congestion control schemes). The investigated
congestion control algorithms should show maximum possible network congestion control algorithms should show maximum possible network
utilization and stability in terms of rate variations, lowest utilization and stability in terms of rate variations, lowest
possible end to end frame latency, network latency and Packet Loss possible end to end frame latency, network latency and Packet Loss
Rate (PLR) at different cell load level. Rate (PLR) at different cell load level.
3.1.1. Network Connection 3.1.1. 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 an LTE 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. The
mobile user is connected to the EPC using LTE radio access technology mobile user is connected to the EPC using cellular radio access
which is further connected to the Internet. The fixed user is technology which is further connected to the Internet. At the other
connected to the Internet via wired connection with sufficiently high end, the fixed user is connected to the Internet via wired connection
bandwidth, for instance, 10 Gbps, so that the system is resource- with sufficiently high bandwidth, for instance, 10 Gbps, so that the
limited on the wireless interface. The wired connection to the system bottleneck is on the cellular radio access interface. The
Internet in this setup does not introduce any network impairments to wired connection to in this setup does not introduce any network
the test; it only adds 10 ms of one-way propagation delay. impairments to the test; it only adds 10 ms of one-way propagation
delay.
The path from the fixed user to the mobile users is defined as 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))
skipping to change at page 7, line 34 skipping to change at page 7, line 33
Figure 1: Simulation Topology Figure 1: Simulation Topology
3.1.2. Simulation Setup 3.1.2. 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 [I-D.ietf-rmcat-eval-test].
The desired simulation setup is as follows -- The desired simulation setup is as follows --
1. Radio environment: 1. Radio environment:
A. Deployment and propagation model: 3GPP case 1 [Deployment] A. Deployment and propagation model: 3GPP case 1 (see
[HO-deploy-3GPP])
B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D] B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D]
C. Mobility: [3km/h, 30km/h] C. Mobility: [3km/h, 30km/h]
D. Transmission bandwidth: 10Mhz D. Transmission bandwidth: 10Mhz
E. Number of cells: multi-cell deployment (3 Cells per Base E. Number of cells: multi-cell deployment (3 Cells per Base
Station (BS) * 7 BS) = 21 cells Station (BS) * 7 BS) = 21 cells
F. Cell radius: 166.666 Meters F. Cell radius: 166.666 Meters
G. Scheduler: Proportional fair with no priority G. Scheduler: Proportional fair with no priority
H. Bearer: Default bearer for all traffic. H. Bearer: Default bearer for all traffic.
I. Active Queue Management (AQM) settings: AQM [on,off] I. Active Queue Management (AQM) settings: AQM [on,off]
2. End to end Round Trip Time (RTT): [40, 150] 2. End-to-end Round Trip Time (RTT): [40ms, 150ms]
3. User arrival model: Poisson arrival model 3. User arrival model: Poisson arrival model
4. User intensity: 4. 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, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5} 5.6, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5}
* Uplink user intensity : {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, * Uplink user intensity : {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9,
5.6, 6.3, 7.0} 5.6, 6.3, 7.0}
skipping to change at page 9, line 18 skipping to change at page 9, line 18
* Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP * Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681]) traffic following default TCP congestion control [RFC5681])
3.2. Bad Radio Coverage 3.2. 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 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 of the user/UE in the media session is an RMCAT compliant each user/UE in the media session is an RMCAT compliant endpoint.
endpoint. The arrival of users follows a Poisson distribution User arrivals follow a Poisson distribution proportional to the
proportional to the length of the call, so as to keep the number of length of the call, to keep the number of users per cell fairly
users per cell fairly constant during the evaluation period. At the constant during the evaluation period. At the beginning of the
beginning of the simulation, there should be enough amount of time to simulation, there should be enough amount of time to warm-up the
warm-up the network. This is to avoid running the evaluation in an network. This is to avoid running the evaluation in an empty network
empty network where network nodes are having empty buffers, low where network nodes are having empty buffers, low interference at the
interference at the beginning of the simulation. This network beginning of the simulation. This network initialization period
initialization period is therefore excluded from the evaluation should be excluded from the evaluation period.
period.
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). The investigated congestion control adaptation algorithms). The investigated congestion control
algorithms should result in maximum possible network utilization and algorithms should result in maximum possible network utilization and
stability in terms of rate variations, lowest possible end to end stability in terms of rate variations, lowest possible end to end
frame latency, network latency and Packet Loss Rate (PLR) at frame latency, network latency and Packet Loss Rate (PLR) at
different cell load levels. different cell load levels.
3.2.1. Network connection 3.2.1. Network connection
skipping to change at page 9, line 49 skipping to change at page 9, line 48
Same as defined in Section 3.1.1 Same as defined in Section 3.1.1
3.2.2. Simulation Setup 3.2.2. 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 3.1 except the following changes: test case defined in Section 3.1 except the following changes:
1. Radio environment: Same as defined in Section 3.1.2 except the 1. Radio environment: Same as defined in Section 3.1.2 except the
following: following:
A. Deployment and propagation model: 3GPP case 3 [Deployment] A. Deployment and propagation model: 3GPP case 3 (see
[HO-deploy-3GPP])
B. Cell radius: 577.3333 Meters B. Cell radius: 577.3333 Meters
C. Mobility: 3km/h 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, 2. 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 3.1.2 3. Media traffic model: Same as defined in Section 3.1.2
4. Other traffic models: 4. Other traffic models:
* Downlink simulation: Maximum of 2Mbps/cell (web browsing or * Downlink simulation: Maximum of 2Mbps/cell (web browsing or
FTP traffic following default TCP congestion control FTP traffic following default TCP congestion control
[RFC5681]) [RFC5681])
* Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP * Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681]) traffic following default TCP congestion control [RFC5681])
3.3. Desired Evaluation Metrics for cellular test cases 3.3. Desired Evaluation Metrics for cellular test cases
RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria] The evaluation criteria document [I-D.ietf-rmcat-eval-criteria]
defines the metrics to be used to evaluate candidate algorithms. defines the metrics to be used to evaluate candidate algorithms.
However, looking at the nature and distinction of cellular networks Considering the nature and distinction of cellular networks we
we recommend that at least the following metrics be used to evaluate recommend that at least the following metrics be used to evaluate the
the performance of the candidate algorithms for the test cases performance of the candidate algorithms:
defined in this document.
The desired metrics are --
o Average cell throughput (for all cells), shows cell utilizations. o Average cell throughput (for all cells), shows cell utilizations.
o Application sending and receiving bitrate, goodput. o Application sending and receiving bitrate, goodput.
o Packet Loss Rate (PLR). o Packet Loss Rate (PLR).
o End to end Media frame delay. For video, this means the delay o End-to-end Media frame delay. For video, this means the delay
from capture to display. from capture to display.
o Transport delay. o Transport delay.
o Algorithm stability in terms of rate variation. o Algorithm stability in terms of rate variation.
4. Wi-Fi Networks Specific Test Cases 4. 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 RMCAT congestion control solutions important to evaluate candidate RTP-based congestion control
over test cases that include Wi-Fi access lines. Such evaluations solutions over test cases that include Wi-Fi access links. Such
should also highlight the inherently different characteristics of Wi- evaluations should highlight the inherently different characteristics
Fi networks in contrast to wired networks: of Wi-Fi networks in contrast to their wired counterparts:
o The wireless radio channel is subject to interference from nearby o The wireless radio channel is subject to interference from nearby
transmitters, multipath fading, and shadowing, causing transmitters, multipath fading, and shadowing. These effects lead
fluctuations in link throughput and sometimes an error-prone to fluctuations in the link throughput and sometimes an error-
communication environment prone communication environment.
o Available network bandwidth is not only shared over the air o 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 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 o 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, however, that the consequent delay and loss applications. Note further that the collision-induced delay and
patterns caused by collisions are qualitatively different from loss patterns are qualitatively different from those caused by
those induced by congestion over a wired connection. congestion over a wired connection.
o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate o 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 scheme for the given received signal appropriate modulation and coding scheme (MCS) for the given
strength. A different choice of physical-layer rate leads to received signal strength. A different choice in the MCS Index
different application-layer throughput. leads to different physical-layer (PHY-layer) link rates and
consequently different application-layer throughput.
o Presence of legacy 802.11b networks can significantly slow down o The presence of legacy devices (e.g., ones operating only in IEEE
the rest of a modern Wi-Fi network. As discussed in [Heusse2003], 802.11b) at a much lower PHY-layer link rate can significantly
the main reason for such abnomaly is that it takes longer to slow down the rest of a modern Wi-Fi network. As discussed in
transmit the same packet over a slower link than over a faster [Heusse2003], the main reason for such anomaly is that it takes
link. much longer to transmit the same packet over a slower link than
over a faster link, thereby consuming a substantial portion of air
time.
o Handover from one Wi-Fi Access Point (AP) to another may lead to o Handover from one Wi-Fi Access Point (AP) to another may lead to
packet delay and losses during the process. excessive packet delays and losses during the process.
o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi o IEEE 802.11e has introduced the Enhanced Distributed Channel
Multi-Media) to give voice and video streams higher priority over Access (EDCA) mechanism to allow different traffic categories to
pure data applications (e.g., file transfers). contend for channel access using different random back-off
parameters. This mechanism is a mandatory requirement for the Wi-
Fi Multimedia (WMM) certification in Wi-Fi Alliance. It allows
for prioritization of real-time application traffic such as voice
and video over non-urgent data transmissions (e.g., file
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 impact 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, influence the behavior of and packet delivery delay. These, in turn, will influence the
end-to-end real-time multimedia congestion control. behavior of end-to-end real-time multimedia congestion control.
Unless otherwise mentioned, test cases in this section are described Unless otherwise mentioned, the test cases in this section choose the
using the underlying PHY- and MAC-layer parameters based on the IEEE PHY- and MAC-layer parameters based on the IEEE 802.11n Standard.
802.11n Standard. Statistics collected from enterprise Wi-Fi Statistics collected from enterprise Wi-Fi networks show that the two
networks show that the two dominant physical modes are 802.11n and dominant physical modes are 802.11n and 802.11ac, accounting for 41%
802.11ac, accounting for 41% and 58% of connected devices. As Wi-Fi and 58% of connected devices. As Wi-Fi standards evolve over time --
standards evolve over time -- for instance, with the introduction of for instance, with the introduction of the emerging Wi-Fi 6 (based on
the emerging Wi-Fi 6 (802.11ax) products -- the PHY- and MAC-layer IEEE 802.11ax) products -- the PHY- and MAC-layer test case
test case specifications need to be updated accordingly to reflect specifications need to be updated accordingly to reflect such
such changes. 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 could be the Either the wired or the Wi-Fi segment of the network can be the
bottleneck. In the following sections, we describe basic test cases bottleneck. The following sections describe basic test cases for
for both scenarios separately. The same set of performance metrics both scenarios separately. The same set of performance metrics as in
as in [I-D.ietf-rmcat-eval-test]) should be collected for each test [I-D.ietf-rmcat-eval-test]) should be collected for each test case.
case.
All test cases described below can be carried out using simulations, We recommend to carry out the test cases as defined in this document
e.g. based on [ns-2] or [ns-3]. When feasible, it is also encouraged using a simulator, such as [NS-2] or [NS-3]. When feasible, it is
to perform testbed-based evaluations using Wi-Fi access points and encouraged to perform testbed-based evaluations using Wi-Fi access
endpoints running up-to-date IEEE 802.11 protocols, such as 802.11ac points and endpoints running up-to-date IEEE 802.11 protocols, such
and the emerging Wi-Fi 6, to verify the viability of the candidate as 802.11ac and the emerging Wi-Fi 6, so as to verify the viability
schemes. of the candidate schemes.
4.1. Bottleneck in Wired Network 4.1. 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 from test evaluation results from this section are similar to those as in
cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), it [I-D.ietf-rmcat-eval-test], it is still worthwhile to run through
is still worthwhile to run through these tests as sanity checks. these tests as sanity checks.
4.1.1. Network topology 4.1.1. 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
access point (AP) and their corresponding wired clients on fixed access point (AP) and their corresponding wired clients on fixed
nodes (FNs). Each connection carries either a RMCAT or a TCP traffic nodes (FNs). Each connection carries either a RTP-based media flow
flow. Directions of the flows can be uplink, downlink, or bi- or a TCP traffic flow. Directions of the flows can be uplink (i.e.,
directional. from mobile nodes to fixed nodes), downlink (i.e., from fixed nodes
to mobile nodes), or bi-directional. The total number of
uplink/downlink/bi-directional flows for RTP-based media traffic and
TCP traffic are denoted as N and M, respectively.
Uplink Uplink
+----------------->+ +----------------->+
+------+ +------+ +------+ +------+
| MN_1 |)))) /=====| FN_1 | | MN_1 |)))) /=====| FN_1 |
+------+ )) // +------+ +------+ )) // +------+
. )) // . . )) // .
. )) // . . )) // .
. )) // . . )) // .
+------+ +----+ +-----+ +------+ +------+ +----+ +-----+ +------+
| MN_N | ))))))) | | | |========| FN_N | | MN_N | ))))))) | | | |========| FN_N |
+------+ | | | | +------+ +------+ | | | | +------+
| AP |=========| FN0 | | AP |=========| FN0 |
+----------+ | | | | +----------+ +----------+ | | | | +----------+
| MN_tcp_1 | )))) | | | |======| MN_tcp_1 | | MN_tcp_1 | )))) | | | |======| FN_tcp_1 |
+----------+ +----+ +-----+ +----------+ +----------+ +----+ +-----+ +----------+
. )) \\ . . )) \\ .
. )) \\ . . )) \\ .
. )) \\ . . )) \\ .
+----------+ )) \\ +----------+ +----------+ )) \\ +----------+
| MN_tcp_M |))) \=====| MN_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
4.1.2. Test setup 4.1.2. Test setup
o Test duration: 120s o Test duration: 120s
o Wi-Fi network characteristics: o Wi-Fi network characteristics:
* Radio propagation model: Log-distance path loss propagation * Radio propagation model: Log-distance path loss propagation
model [NS3WiFi] model (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@52Mbps * MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps
o Wired path characteristics: o Wired path characteristics:
* Path capacity: 1Mbps * Path capacity: 1Mbps
* One-Way propagation delay: 50ms. * One-Way propagation delay: 50ms.
* Maximum end-to-end jitter: 30ms * Maximum end-to-end jitter: 30ms
* Bottleneck queue type: Drop tail. * Bottleneck queue type: Drop tail.
skipping to change at page 14, line 40 skipping to change at page 14, line 40
+ Number of sources (M): See Section 4.1.3 + Number of sources (M): See Section 4.1.3
+ Congestion control: Default TCP congestion control [RFC5681] + Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP. or constant-bit-rate (CBR) traffic over UDP.
+ Traffic timeline: See Section 4.1.3 + Traffic timeline: See Section 4.1.3
4.1.3. Typical test scenarios 4.1.3. Typical test scenarios
o Single uplink RMCAT flow: N=1 with uplink direction and M=0. o Single uplink RTP-based media flow: N=1 with uplink direction and
M=0.
o One pair of bi-directional RMCAT flows: N=2 (with one uplink flow o One pair of bi-directional RTP-based media flows: N=2 (i.e., one
and one downlink flow); M=0. uplink flow and one downlink flow); M=0.
o One pair of bi-directional RMCAT flows, one on-off CBR over UDP o One pair of bi-directional RTP-based media flows: N=2; one uplink
flow on uplink: N=2 (with one uplink flow and one downlink flow); on-off CBR flow over UDP: M=1 (uplink). The CBR flow has ON time
M=1 (uplink). CBR flow ON time at 0s-60s, OFF time at 60s-119s. at t=0s-60s and OFF time at t=60s-119s.
o One pair of bi-directional RMCAT flows, one off-on CBR over UDP o One pair of bi-directional RTP-based media flows: N=2; one uplink
flow on uplink: N=2 (with one uplink flow and one downlink flow); off-on CBR flow over UDP: M=1 (uplink). The CBR flow has OFF time
M=1 (uplink). OFF time for UDP flow: 0s-60s; ON time: 60s-119s. at t=0s-60s and ON time at t=60s-119s.
o One RMCAT flow competing against one long-live TCP flow over o One RTP-based media flow competing against one long-live TCP flow
uplink: N=1 (uplink) and M = 1(uplink), TCP start time at 0s and in the uplink direction: N=1 (uplink) and M = 1(uplink). The TCP
end time at 119s. flow has start time at t=0s and end time at t=119s.
4.1.4. Expected behavior 4.1.4. Expected behavior
o Single uplink RMCAT flow: the candidate algorithm is expected to o Single uplink RTP-based media flow: the candidate algorithm is
detect the path capacity constraint, to converge to bottleneck expected to detect the path capacity constraint, to converge to
link capacity and to adapt the flow to avoid unwanted oscillation the bottleneck link capacity, and to adapt the flow to avoid
when the sending bit rate is approaching the bottleneck link unwanted oscillations when the sending bit rate is approaching the
capacity. No excessive oscillations in the media rate should be bottleneck link capacity. No excessive oscillations in the media
present. rate should be present.
o Bi-directional RMCAT flows: It is expected that the candidate o Bi-directional RTP-based media flows: the candidate algorithm is
algorithm is able to converge to the bottleneck capacity of the expected to converge to the bottleneck capacity of the wired path
wired path on both directions despite the presence of measurement in both directions despite the presence of measurement noise over
noise over the Wi-Fi connection. In the presence of background the Wi-Fi connection. In the presence of background TCP or CBR
TCP or CBR over UDP traffic, the rate of RMCAT flows should adapt over UDP traffic, the rate of RTP-based media flows should adapt
in a timely manner to changes in the available bottleneck promptly to the arrival and departure of background traffic flows.
bandwidth.
o One RMCAT flow competing with long-live TCP flow over uplink: the o One RTP-based media flow competing with long-live TCP flow in the
candidate algorithm should be able to avoid congestion collapse, uplink direction: the candidate algorithm is expected to avoid
and to stabilize at a fair share of the bottleneck link capacity. congestion collapse and to stabilize at a fair share of the
bottleneck link capacity.
4.2. Bottleneck in Wi-Fi Network 4.2. Bottleneck in Wi-Fi Network
These test cases assume that the wired portion along the media path The test cases in this section assume that the wired segment along
is well-provisioned whereas the bottleneck exists over the Wi-Fi the media path is well-provisioned whereas the bottleneck exists over
access network. This is to mimic the application scenarios typically the Wi-Fi access network. This is to mimic the application scenarios
encountered by users in an enterprise environment or at a coffee typically encountered by users in an enterprise environment or at a
house. coffee house.
4.2.1. Network topology 4.2.1. Network topology
Same as defined in Section 4.1.1 Same as defined in Section 4.1.1
4.2.2. Test setup 4.2.2. Test setup
o Test duration: 120s o Test duration: 120s
o Wi-Fi network characteristics: o Wi-Fi network characteristics:
* Radio propagation model: Log-distance path loss propagation * Radio propagation model: Log-distance path loss propagation
model [NS3WiFi] model (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: 16-QAM 1/2, Raw Data Rate at 52Mbps
o Wired path characteristics: o Wired path characteristics:
* Path capacity: 100Mbps. * Path capacity: 100Mbps.
* One-Way propagation delay: 50ms. * One-Way propagation delay: 50ms.
skipping to change at page 17, line 8 skipping to change at page 17, line 8
+ Traffic direction: See Section 4.2.3. + Traffic direction: See Section 4.2.3.
+ Congestion control: Default TCP congestion control [RFC5681] + Congestion control: Default TCP congestion control [RFC5681]
or constant-bit-rate (CBR) traffic over UDP. or constant-bit-rate (CBR) traffic over UDP.
+ Traffic timeline: See Section 4.2.3. + Traffic timeline: See Section 4.2.3.
4.2.3. Typical test scenarios 4.2.3. 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 RMCAT important for understanding the behavior of a candidate RTP-based
solution over a Wi-Fi network. congestion control scheme over a Wi-Fi network.
a. Multiple RMCAT Flows Sharing the Wireless Downlink: N=16 (all a. Multiple RTP-based media flows sharing the wireless downlink:
downlink); M = 0. This test case is for studying the impact of N=16 (all downlink); M = 0. This test case is for studying the
contention on the multiple concurrent RMCAT flows. For an impact of contention on the multiple concurrent media flows. For
802.11n network, given the MCS Index of 11 and the corresponding an 802.11n network, given the MCS Index of 11 and the
raw data rate of 52Mbps, the total application-layer throughput corresponding link rate of 52Mbps, the total application-layer
(assuming reasonable distance, low interference and infrequent throughput (assuming reasonable distance, low interference and
contentions caused by competing streams) is around 20Mbps. infrequent contentions caused by competing streams) is around
Consequently, a total of N=16 RMCAT flows are needed to saturate 20Mbps. A total of N=16 RTP-based media flows (with a maximum
the wireless interface in this experiment. Evaluation of a given rate of 1.5Mbps each) are expected to saturate the wireless
candidate solution should focus on whether downlink RMCAT flows interface in this experiment. Evaluation of a given candidate
can stabilize at a fair share of total application-layer scheme should focus on whether the downlink media flows can
stabilize at a fair share of the total application-layer
throughput. throughput.
b. Multiple RMCAT Flows Sharing the Wireless Uplink: N = 16 (all b. Multiple RTP-based media flows sharing the wireless uplink:N = 16
downlink); M = 0. When multiple clients attempt to transmit (all downlink); M = 0. When multiple clients attempt to transmit
video packets uplink over the wireless interface, they introduce media packets uplink over the Wi-Fi network, they introduce more
more frequent contentions and potential collisions. Per-flow frequent contentions and potential collisions. Per-flow
throughput is expected to be lower than that in the previous throughput is expected to be lower than that in the previous
downlink-only scenario. Evaluation of a given candidate solution downlink-only scenario. Evaluation of a given candidate scheme
should focus on whether uplink flows can stabilize at a fair should focus on whether the uplink flows can stabilize at a fair
share of application-layer throughput. share of the total application-layer throughput.
c. Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8 c. Multiple bi-directional RTP-based media flows: N = 16 (8 uplink
downlink); M = 0. The goal of this test is to evaluate the and 8 downlink); M = 0. The goal of this test is to evaluate the
performance of the candidate solution in terms of bandwidth performance of the candidate scheme in terms of bandwidth
fairness between uplink and downlink flows. fairness between uplink and downlink flows.
d. Multiple Bi-directional RMCAT Flows with on-off CBR traffic: N = d. Multiple bi-directional RTP-based media flows with on-off CBR
16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5
test is to evaluate the adaptation behavior of the candidate (uplink). The goal of this test is to evaluate the adaptation
solution when its available bandwidth changes due to the behavior of the candidate scheme when its available bandwidth
departure of background traffic. The background traffic consists changes due to the departure of background traffic. The
of several (e.g., M=5) CBR flows transported over UDP. These background traffic consists of several (e.g., M=5) CBR flows
background flows are ON at times t=0-60s and are OFF at times transported over UDP. These background flows are ON at time
t=61-120s. t=0-60s and OFF at time t=61-120s.
e. 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 the adaptation behavior of the candidate
solution when its available bandwidth changes due to the arrival
of background traffic. The background traffic consists of
several (e.g., M=5) parallel CBR flows transported over UDP.
These background flows are OFF at times t=0-60s and are ON at e. Multiple bi-directional RTP-based media flows with off-on CBR
times t=61-120s. traffic over UDP: N = 16 (8 uplink and 8 downlink); M = 5
(uplink). The goal of this test is to evaluate the adaptation
behavior of the candidate scheme when its available bandwidth
changes due to the arrival of background traffic. The background
traffic consists of several (e.g., M=5) parallel CBR flows
transported over UDP. These background flows are OFF at time
t=0-60s and ON at times t=61-120s.
f. Multiple Bi-directional RMCAT flows in the presence of background f. Multiple bi-directional RTP-based media flows in the presence of
TCP traffic: N=16 (8 uplink and 8 downlink); M = 5 (uplink). The background TCP traffic: N=16 (8 uplink and 8 downlink); M = 5
goal of this test is to evaluate how RMCAT flows compete against (uplink). The goal of this test is to evaluate how RTP-based
TCP over a congested Wi-Fi network for a given candidate media flows compete against TCP over a congested Wi-Fi network
solution. TCP start time: 40s, end time: 80s. for a given candidate scheme. TCP flows have start time at t=40s
and end time at t=80s.
g. Varying number of RMCAT flows: A series of tests can be carried g. Varying number of RTP-based media flows: A series of tests can be
out for the above test cases with different values of N, e.g., N carried out for the above test cases with different values of N,
= [4, 8, 12, 16, 20]. The goal of this test is to evaluate how a e.g., N = [4, 8, 12, 16, 20]. The goal of this test is to
candidate RMCAT solution responds to varying traffic load/demand evaluate how a candidate scheme responds to varying traffic load/
over a congested Wi-Fi network. The start time of these RMCAT demand over a congested Wi-Fi network. The start times of the
flows is randomly distributed within a window of t=0-10s, whereas media flows are randomly distributes within a window of t=0-10s;
their end times are randomly distributed within a window of their end times are randomly distributed within a window of
t=110-120s. t=110-120s.
4.2.4. Expected behavior 4.2.4. Expected behavior
o Multiple downlink RMCAT flows: each RMCAT flow should get its fair o Multiple downlink RTP-based media flows: each media flow is
share of the total bottleneck link bandwidth. Overall bandwidth expected to get its fair share of the total bottleneck link
usage should not be significantly lower than that experienced by bandwidth. Overall bandwidth usage should not be significantly
the same number of concurrent downlink TCP flows. In other words, lower than that experienced by the same number of concurrent
the performance of multiple concurrent TCP flows will be used as a downlink TCP flows. In other words, the behavior of multiple
performance benchmark for this test scenario. The end-to-end concurrent TCP flows will be used as a performance benchmark for
delay and packet loss ratio experienced by each flow should be this test scenario. The end-to-end delay and packet loss ratio
within an acceptable range for real-time multimedia applications. experienced by each flow should be within an acceptable range for
real-time multimedia applications.
o Multiple uplink RMCAT flows: overall bandwidth usage shared by all o Multiple uplink RTP-based media flows: overall bandwidth usage by
RMCAT 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 performance of multiple concurrent TCP flows will other words, the behavior of multiple concurrent TCP flows will be
be used as a performance benchmark for this test scenario. used as a performance benchmark for this test scenario.
o Multiple bi-directional RMCAT flows with dynamic background o Multiple bi-directional RTP-based media flows with dynamic
traffic carrying CBR flows over UDP: RMCAT flows should adapt in a background traffic carrying CBR flows over UDP: the media flows
timely fashion to the resulting changes in available bandwidth. are expected to adapt in a timely fashion to the changes in
available bandwidth introduced by the arrival/departure of
background traffic.
o Multiple bi-directional RMCAT flows with dynamic background o Multiple bi-directional RTP-based media flows with dynamic
traffic over TCP: during the presence of TCP background flows, the background traffic over TCP: during the presence of TCP background
overall bandwidth usage shared by all RMCAT flows should not be flows, the overall bandwidth usage by all media flows should not
significantly lower than those achieved by the same number of bi- be significantly lower than those achieved by the same number of
directional TCP flows. In other words, the performance of bi-directional TCP flows. In other words, the behavior of
multiple concurrent TCP flows will be used as a performance multiple concurrent TCP flows will be used as a performance
benchmark for this test scenario. All downlink RMCAT flows are benchmark for this test scenario. All downlink media flows are
expected to obtain similar bandwidth with respect to each other. expected to obtain similar bandwidth as each other. The
The throughput of RMCAT flows should decrease upon the arrival of throughput of each media flow is expected to decrease upon the
TCP background traffic and increase upon their departure, both arrival of TCP background traffic and, conversely, increase upon
reactions should occur in a timely fashion (e.g., within 10s of their departure. Both reactions should occur in a timely fashion,
seconds). for example, within 10s of seconds.
o Varying number of bi-directional RMCAT flows: the test results for o Varying number of bi-directional RTP-based media flows: the test
varying values of N -- while keeping all other parameters constant results for varying values of N -- while keeping all other
-- is expected to show steady and stable per-flow throughput for parameters constant -- is expected to show steady and stable per-
each value of N. The average throughput of all RMCAT flows is flow throughput for each value of N. The average throughput of
expected to stay constant around the maximum rate when N is small, all media flows is expected to stay constant around the maximum
then gradually decrease with increasing number of RMCAT flows till rate when N is small, then gradually decrease with increasing
it reaches the minimum allowed rate, beyond which the offered load value of N till it reaches the minimum allowed rate, beyond which
to the Wi-Fi network (with a large value of N) is exceeding its the offered load to the Wi-Fi network exceeds its capacity (i.e.,
capacity. with a very large value of N).
4.3. Other Potential Test Cases 4.3. Other Potential Test Cases
4.3.1. EDCA/WMM usage 4.3.1. EDCA/WMM usage
EDCA/WMM is prioritized QoS with four traffic classes (or Access The EDCA/WMM mechanism defines prioritized QoS for four traffic
Categories) with differing priorities. RMCAT flows should achieve classes (or Access Categories). RTP-based real-time media flows
better performance (i.e., lower delay, fewer packet losses) with should achieve better performance in terms of lower delay and fewer
EDCA/WMM enabled when competing against non-interactive background packet losses with EDCA/WMM enabled when competing against non-
traffic (e.g., file transfers). When most of the traffic over Wi-Fi interactive background traffic such as file transfers. When most of
is dominated by media, however, turning on WMM may actually degrade the traffic over Wi-Fi is dominated by media, however, turning on WMM
performance since all media flows now attempt to access the wireless may degrade performance since all media flows now attempt to access
transmission medium more aggressively, thereby causing more frequent the wireless transmission medium more aggressively, thereby causing
collisions and collision-induced losses. This is a topic worthy of more frequent collisions and collision-induced losses. This is a
further investigation. topic worthy of further investigation.
4.3.2. Effects of Legacy 802.11b Devices
When there exist 802.11b devices connected to a modern 802.11
network, they may affect the performance of the whole network.
Additional test cases can be added to evaluate the impacts of legacy
devices on the performance of the candidate congestion control
algorithm.
5. Conclusion 4.3.2. Effect of heterogeneous link rates
This document defines a collection of test cases that are considered As discussed in [Heusse2003], the presence of clients operating over
important for cellular and Wi-Fi networks. Moreover, this document slow PHY-layer link rates (e.g., a legacy 802.11b device) connected
also provides a framework for defining additional test cases over to a modern network may adversely impact the overall performance of
wireless cellular/Wi-Fi networks. the network. Additional test cases can be devised to evaluate the
effect of clients with heterogeneous link rates on the performance of
the candidate congestion control algorithm. Such test cases, for
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
effect on the congestion control behavior of the real-time
interactive applications.
6. IANA Considerations 5. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
7. Security Considerations 6. Security Considerations
The security considerations in [I-D.ietf-rmcat-eval-criteria] and the The security considerations in [I-D.ietf-rmcat-eval-criteria] and the
relevant congestion control algorithms apply. The principles for relevant congestion control algorithms apply. The principles for
congestion control are described in [RFC2914], and in particular, any congestion control are described in [RFC2914], and in particular, any
new method MUST implement safeguards to avoid congestion collapse of new method MUST implement safeguards to avoid congestion collapse of
the Internet. the Internet.
The evaluations of the test cases are intended to carry out in a The evaluations of the test cases are intended to carry out in a
controlled lab environment. Hence, the applications, simulators and controlled lab environment. Hence, the applications, simulators and
network nodes ought to be well-behaved and should not impact the network nodes ought to be well-behaved and should not impact the
desired results. It is important to take appropriate caution to desired results. It is important to take appropriate caution to
avoid leaking non-responsive traffic from unproven congestion avoid leaking non-responsive traffic with unproven congestion
avoidance techniques onto the open Internet. avoidance behavior onto the open Internet.
8. Acknowledgments 7. Acknowledgments
The authors would like to thank Tomas Frankkila, Magnus Westerlund, The authors would like to thank Tomas Frankkila, Magnus Westerlund,
Kristofer Sandlund, and Sergio Mena de la Cruz for their valuable Kristofer Sandlund, Sergio Mena de la Cruz, and Mirja Kuehlewind for
input and review comments regarding this draft. their valuable inputs and review comments regarding this draft.
9. References 8. References
9.1. Normative References 8.1. Normative References
[Deployment] [HO-deploy-3GPP]
TS 25.814, 3GPP., "Physical layer aspects for evolved TS 25.814, 3GPP., "Physical layer aspects for evolved
Universal Terrestrial Radio Access (UTRA)", October 2006, Universal Terrestrial Radio Access (UTRA)", 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>.
[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] [I-D.ietf-rmcat-eval-criteria]
Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion
Control for Interactive Real-time Media", draft-ietf- Control for Interactive Real-time Media", draft-ietf-
rmcat-eval-criteria-08 (work in progress), November 2018. rmcat-eval-criteria-11 (work in progress), February 2020.
[NS3WiFi] "Wi-Fi Channel Model in NS3 Simulator", [I-D.ietf-rmcat-eval-test]
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat-
eval-test-10 (work in progress), May 2019.
[IEEE802.11]
IEEE, "Standard for Information technology--
Telecommunications and information exchange between
systems Local and metropolitan area networks--Specific
requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications", 2012.
[NS3WiFi] "Wi-Fi Channel Model in ns-3 Simulator",
<https://www.nsnam.org/doxygen/ <https://www.nsnam.org/doxygen/
classns3_1_1_yans_wifi_channel.html>. classns3_1_1_yans_wifi_channel.html>.
[QoS-3GPP]
TS 23.203, 3GPP., "Policy and charging control
architecture", June 2011, <http://www.3gpp.org/ftp/specs/
archive/23_series/23.203/23203-990.zip>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <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 [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 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References 8.2. 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", in Proc. 23th
Annual Joint Conference of the IEEE Computer and Annual Joint Conference of the IEEE Computer and
Communications Societies, (INFOCOM'03), March 2003. Communications Societies, (INFOCOM'03), March 2003.
[HO-def-3GPP]
TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications",
December 2009, <http://www.3gpp.org/ftp/specs/
archive/21_series/21.905/21905-940.zip>.
[HO-LTE-3GPP]
TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC);
Protocol specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/36_series/36.331/36331-990.zip>.
[HO-UMTS-3GPP]
TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol
specification", December 2011,
<http://www.3gpp.org/ftp/specs/
archive/25_series/25.331/25331-990.zip>.
[I-D.ietf-rmcat-cc-requirements] [I-D.ietf-rmcat-cc-requirements]
Jesup, R. and Z. Sarker, "Congestion Control Requirements Jesup, R. and Z. Sarker, "Congestion Control Requirements
for Interactive Real-Time Media", draft-ietf-rmcat-cc- for Interactive Real-Time Media", draft-ietf-rmcat-cc-
requirements-09 (work in progress), December 2014. requirements-09 (work in progress), December 2014.
[I-D.ietf-rmcat-eval-test] [NS-2] "ns-2", December 2014,
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test <http://nsnam.sourceforge.net/wiki/index.php/Main_Page>.
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.
[LTE-simulator] [NS-3] "ns-3 Network Simulator", <https://www.nsnam.org/>.
"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", [QoS-3GPP]
<http://www.isi.edu/nsnam/ns/>. 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>.
[ns-3] "The Network Simulator - ns-3", <https://www.nsnam.org/>. [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.
Authors' Addresses Authors' Addresses
Zaheduzzaman Sarker Zaheduzzaman Sarker
Ericsson AB Ericsson AB
Laboratoriegraend 11 Laboratoriegraend 11
Luleae 97753 Luleae 97753
Sweden Sweden
Phone: +46 107173743 Phone: +46 107173743
skipping to change at page 23, line 4 skipping to change at page 22, line 43
Email: zaheduzzaman.sarker@ericsson.com Email: zaheduzzaman.sarker@ericsson.com
Ingemar Johansson Ingemar Johansson
Ericsson AB Ericsson AB
Laboratoriegraend 11 Laboratoriegraend 11
Luleae 97753 Luleae 97753
Sweden Sweden
Phone: +46 10 7143042 Phone: +46 10 7143042
Email: ingemar.s.johansson@ericsson.com Email: ingemar.s.johansson@ericsson.com
Xiaoqing Zhu Xiaoqing Zhu
Cisco Systems Cisco Systems
12515 Research Blvd., Building 4 12515 Research Blvd., Building 4
Austin, TX 78759 Austin, TX 78759
USA USA
Email: xiaoqzhu@cisco.com Email: xiaoqzhu@cisco.com
Jiantao Fu Jiantao Fu
Cisco Systems Cisco Systems
707 Tasman Drive 771 Alder Drive
Milpitas, CA 95035 Milpitas, CA 95035
USA USA
Email: jianfu@cisco.com Email: jianfu@cisco.com
Wei-Tian Tan Wei-Tian Tan
Cisco Systems Cisco Systems
725 Alder Drive 510 McCarthy Blvd
Milpitas, CA 95035 Milpitas, CA 95035
USA USA
Email: dtan2@cisco.com Email: dtan2@cisco.com
Michael A. Ramalho Michael A. Ramalho
Cisco Systems, Inc. AcousticComms Consulting
8000 Hawkins Road 6310 Watercrest Way Unit 203
Sarasota, FL 34241 Lakewood Ranch, FL 34202-5211
USA USA
Phone: +1 919 476 2038 Phone: +1 732 832 9723
Email: mramalho@cisco.com Email: mar42@cornell.edu
 End of changes. 110 change blocks. 
395 lines changed or deleted 400 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/