< draft-ietf-rmcat-wireless-tests-06.txt   draft-ietf-rmcat-wireless-tests-07.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: June 25, 2019 X. Zhu Expires: January 2, 2020 X. Zhu
J. Fu J. Fu
W. Tan W. Tan
M. Ramalho M. Ramalho
Cisco Systems Cisco Systems
December 22, 2018 July 1, 2019
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-06 draft-ietf-rmcat-wireless-tests-07
Abstract Abstract
The Real-time Transport Protocol (RTP) is used for interactive The Real-time Transport Protocol (RTP) is used for interactive
multimedia communication applications. These applications are multimedia communication applications. A congestion control
typically required to implement congestion control. To ensure algorithm is typically required by these applications. To ensure
seamless and robust user experience, a well-designed RTP-based seamless and robust user experience, a well-designed RTP-based
congestion control algorithm should work well across all access congestion control algorithm should work well across all access
network types. This document describes test cases for evaluating network types. This document describes test cases for evaluating
performances of such congestion control algorithms over LTE and Wi-Fi performances of such congestion control algorithms over LTE and Wi-Fi
networks. 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.
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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 June 25, 2019. This Internet-Draft will expire on January 2, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 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
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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
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3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7
3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 8 3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 8
3.2.1. Network connection . . . . . . . . . . . . . . . . . 9 3.2.1. Network connection . . . . . . . . . . . . . . . . . 9
3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9
3.3. Desired Evaluation Metrics for cellular test cases . . . 10 3.3. Desired Evaluation Metrics for cellular test cases . . . 10
4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10
4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12
4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12
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 . . . . . . . . . . . . . . . . . . 14 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 . . . . . . . . . . . . . . . 16 4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 16
4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 17 4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18
4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 18 4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19
4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 18 4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19
4.3.2. Effects of Legacy 802.11b Devices . . . . . . . . . . 18 4.3.2. Effects of Legacy 802.11b Devices . . . . . . . . . . 19
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 19 9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 20 9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
Wireless networks (both cellular and Wi-Fi [IEEE802.11] local area Wireless networks (both cellular and Wi-Fi [IEEE802.11]) are an
network) are an integral part of the Internet. Mobile devices integral part of the Internet. Mobile devices connected to the
connected to the wireless networks generate huge amount of media wireless networks account for an increasingly more significant
traffic in the Internet. Application scenarios range from users portion of the media traffic over the Internet. Application
having a video call in the bus to media consumption by someone scenarios range from video conferencing calls in a bus or train to
sitting on a living room couch. It is well known that the media consumption by someone sitting on a living room couch. It is
characteristics and technical challenges for offering multimedia well known that the characteristics and technical challenges for
services over wireless are very different from those of providing the supporting multimedia services over wireless are very different from
same service over a wired network. Even though RMCAT basic test those of providing the same service over a wired network. Even
cases as defined in [I-D.ietf-rmcat-eval-test] have covered many though basic test cases for evaluating RTP-based congestion control
effects of the impairments also visible in wireless networks, there schemes as defined in [I-D.ietf-rmcat-eval-test] have covered many
remains characteristics and dynamics unique to a given wireless effects of the impairments common to both wired and wireless
environment. For example, in LTE networks the base station maintains networks, there remain characteristics and dynamics unique to a given
queues per radio bearer per user hence it leads to a different nature wireless environment. For example, in LTE networks, the base station
of interaction from that over the wired network, where traffic from maintains individual queues per radio bearer per user hence it leads
all users share the same queue. Furthermore, user mobility in a to a different nature of interaction between traffic flows of
cellular network is different than user mobility in a Wi-Fi network. different users. This contrasts with wired network, where traffic
Therefore, It is important to evaluate performance of the proposed from all users share the same queue. Furthermore, user mobility
RMCAT candidate solutions separately over cellular mobile networks patterns in a cellular network differs from those in a Wi-Fi network.
and over Wi-Fi local networks (i.e., IEEE 802.11xx protocol family ). Therefore, it is important to evaluate the performance of proposed
candidate RTP-based congestion control solutions over cellular mobile
networks and over Wi-Fi networks respectively.
RMCAT evaluation criteria [I-D.ietf-rmcat-eval-criteria] document RMCAT evaluation criteria [I-D.ietf-rmcat-eval-criteria] document
provides the guideline for evaluating candidate algorithms and provides the guideline for evaluating candidate algorithms and
recognizes the importance of testing over wireless access networks. recognizes the importance of testing over wireless access networks.
However, it does not describe any specific test cases for evaluating However, it does not describe any specific test cases for performance
performance of the candidate algorithm. This document describes test evaluation of candidate algorithms. This document describes test
cases specifically targeting cellular networks such as LTE networks cases specifically targeting cellular networks such as LTE networks
and Wi-Fi local 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
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edge which may lead to a significant amount of retransmissions to edge which may lead to a significant amount of retransmissions to
deliver the data from the base station to the destination and vice deliver the data from the base station to the destination and vice
versa. These network links or radio links will often act as a versa. These network links or radio links will often act as a
bottleneck for the rest of the network which will eventually lead to bottleneck for the rest of the network which 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 still be some packet losses and delay variations. there will still be some packet losses and delay variations.
Moreover, with increased cell load or handover to a congested cell, Moreover, with increased cell load or handover to a congested cell,
congestion in transport network will become even worse. Besides, congestion in transport network will become even worse. Besides,
there are certain characteristics which make the cellular network there are certain characteristics which make the cellular network
different and challenging than other types of access network such as different from and more challenging than other types of access
Wi-Fi and wired network. In a cellular network - networks such as Wi-Fi and wired network. In a cellular 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.
* Left over/ unused resource can be grabbed by other greedy * Left over/ unused resource can be grabbed by other greedy
users. 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
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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 3G and 4G radio technologies can
support the high bandwidth requirements from real-time interactive support the high bandwidth requirements from real-time interactive
video applications. The future real-time interactive application video applications. The future real-time interactive application
will impose even greater demand on cellular network performance which will impose even greater demand on cellular network performance which
makes 4G (and beyond radio technologies) more suitable access makes 4G (and beyond radio technologies) more suitable access
technology for such genre of application. technology for such genre of application.
The key factors to define test cases for cellular network are The key factors to define 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 network it is very hard to separate such events However, for cellular network it is very hard to separate such events
from one another as these events are heavily related. Hence instead from one another as these events are heavily related. Hence instead
of devising separate test cases for all those important events we of devising separate test cases for all those important events we
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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. of the user/UE in the media session is an RMCAT compliant endpoint.
The arrival of users follows a Poisson distribution, which is The arrival of users follows a Poisson distribution, which is
proportional to the length of the call, so that the number of users proportional to the length of the call, so that the number of users
per cell is kept fairly constant during the evaluation period. At per cell is kept fairly constant during the evaluation period. At
the beginning of the simulation there should be enough amount of time the beginning of the simulation there should be enough time to warm-
to warm-up the network. This is to avoid running the evaluation in up the network. This is to avoid running the evaluation in an empty
an empty network where network nodes are having empty buffers, low network where network nodes are having empty buffers, low
interference at the beginning of the simulation. This network interference at the beginning of the simulation. This network
initialization period is therefore excluded from the evaluation initialization period is therefore excluded from the evaluation
period. period.
This test case also includes user mobility and competing traffic. This test case also includes user mobility and competing traffic.
The competing traffics includes both same kind of flows (with same The competing traffic includes both same kind of flows (with same
adaptation algorithms) and different kind of flows (with different adaptation algorithms) and different kind of flows (with different
service and congestion control). The investigated congestion control service and congestion control). The investigated congestion control
algorithms should show maximum possible network utilization and algorithms should show 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 level. 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 a LTE radio between the mobile user and fixed user consists of a LTE 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 LTE radio access technology
which is further connected to the Internet. The fixed user is which is further connected to the Internet. The fixed user is
connected to the Internet via wired connection with no bottleneck connected to the Internet via wired connection with sufficiently high
(practically infinite bandwidth). The Internet and wired connection bandwidth, for instance, 10 Gbps, so that the system is resource-
in this setup does not add any network impairments to the test, it limited on the wireless interface. The Internet and wired connection
only adds 10ms of one-way transport propagation delay. in this setup does not introduce any network impairments to the test;
it only adds 10ms of one-way propagation delay.
The path from the fixed user to mobile user is defines as "Downlink" The path from the fixed user to mobile user is defines as "Downlink"
and the path from mobile user to the fixed user is defined as and the path from mobile user to the fixed user is defined as
"Uplink". We assume that only uplink or downlink is congested for "Uplink". We assume that only uplink or downlink is congested for
the mobile users. Hence, we recommend that the uplink and downlink the mobile users. Hence, we recommend that the uplink and downlink
simulations are run separately. simulations are run separately.
uplink uplink
++))) +--------------------------> ++))) +-------------------------->
++-+ ((o)) ++-+ ((o))
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2. End to end Round Trip Time (RTT): [ 40, 150] 2. End to end Round Trip Time (RTT): [ 40, 150]
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 intercity : {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}
5. Simulation duration: 91s 5. Simulation duration: 91s
6. Evaluation period : 30s-60s 6. Evaluation period : 30s-60s
7. Media traffic 7. Media traffic
1. Media type: Video 1. Media type: Video
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d. Media codec: Constant BitRate (CBR) d. Media codec: Constant BitRate (CBR)
e. Media bitrate : 20 Kbps e. Media bitrate : 20 Kbps
f. Adaptation: off f. Adaptation: off
8. Other traffic model: 8. Other traffic model:
* Downlink simulation: Maximum of 4Mbps/cell (web browsing or * Downlink simulation: Maximum of 4Mbps/cell (web browsing or
FTP traffic) FTP traffic following default TCP congestion control
[RFC5681])
* Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP * Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP
traffic) 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 larger with bad radio coverage. The scenario is created by using larger
cell radius than previous test case. In this test case each of the cell radius than previous test case. In this test case each of the
user/UE in the media session is an RMCAT compliant endpoint. The user/UE in the media session is an RMCAT compliant endpoint. The
arrival of users follows a Poisson distribution, which is arrival of users follows a Poisson distribution, which is
proportional to the length of the call, so that the number of users proportional to the length of the call, so that the number of users
per cell is kept fairly constant during the evaluation period. At per cell is kept fairly constant during the evaluation period. At
the beginning of the simulation there should be enough amount of time the beginning of the simulation there should be enough amount of time
to warm-up the network. This is to avoid running the evaluation in to warm-up the network. This is to avoid running the evaluation in
an empty network where network nodes are having empty buffers, low an empty network where network nodes are having empty buffers, low
interference at the beginning of the simulation. This network interference at the beginning of the simulation. This network
initialization period is therefore excluded from the evaluation initialization period is therefore excluded from the evaluation
period. period.
This test case also includes user mobility and competing traffic. This test case also includes user mobility and competing traffic.
The competing traffics includes same kind of flows (with same The competing traffic includes same kind of flows (with same
adaptation algorithms) . The investigated congestion control adaptation algorithms) . The investigated congestion control
algorithms should show maximum possible network utilization and algorithms should show 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 level. different cell load level.
3.2.1. Network connection 3.2.1. Network connection
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 same as Varying Network Load test The desired simulation setup is same as Varying Network Load test
case defined in Section 3.1 except following changes- case defined in Section 3.1 except following changes:
1. Radio environment : Same as defined in Section 3.1.2 except 1. Radio environment: Same as defined in Section 3.1.2 except the
followings following:
A. Deployment and propagation model : 3GPP case 3[Deployment] A. Deployment and propagation model : 3GPP case 3 [Deployment]
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 model: None 4. Other traffic model:
* Downlink simulation: Maximum of 2Mbps/cell (web browsing or
FTP traffic following default TCP congestion control
[RFC5681])
* Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP
traffic following default TCP congestion control [RFC5681])
3.3. Desired Evaluation Metrics for cellular test cases 3.3. Desired Evaluation Metrics for cellular test cases
RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria] RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria]
defines metrics to be used to evaluate candidate algorithms. defines metrics to be used to evaluate candidate algorithms.
However, looking at the nature and distinction of cellular networks However, looking at the nature and distinction of cellular networks
we recommend at minimum following metrics to be used to evaluate the we recommend at minimum following metrics to be used to evaluate the
performance of the candidate algorithms for the test cases defined in performance of the candidate algorithms for the test cases defined in
this document. this document.
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communication environment 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 cocurrent users, but also between uplink and downlink between cocurrent 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 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 and significant network overhead. This, in frequent collisions over the air and significant network overhead,
turn, leads to excessive delay, retransmissions, packet losses and as well as packet drops due to buffer overflow at the
lower effective bandwidth for applications. transmitters. This, in turn, leads to excessive delay,
retransmissions, packet losses and lower effective bandwidth for
applications. Note, however, that the consequent delay and loss
patterns caused by collisions are qualitatively different from
those induced by congestion over a wired connection.
o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate 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 a given received singal appropriate modulation scheme for a given received signal
strength. A different choice of physical-layer rate leads to strength. A different choice of physical-layer rate leads to
different application-layer throughput. different application-layer throughput.
o Presence of legancy 802.11b networks can significantly slow down o Presence of legancy 802.11b networks can significantly slow down
the the rest of a modern Wi-Fi Network, since it takes longer to the the rest of a modern Wi-Fi Network. As discussed in
transmit the same packet over a slower link than over a faster [Heusse2003]since it takes longer to transmit the same packet over
link. [Editor's note: maybe include a reference here instead.] a slower link than over a faster link.
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. packet delay and losses during the process.
o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi
Multi-Media) to give voice and video streams higher priority over Multi-Media) to give voice and video streams higher priority over
pure data applications (e.g., file transfers). pure data applications (e.g., file transfers).
In summary, presence of Wi-Fi access links in different network In summary, 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, influence the behavior of
end-to-end real-time multimedia congestion control. end-to-end real-time multimedia congestion control.
Throughout this draft, unless otherwise mentioned, test cases are Unless otherwise mentioned, test cases in this section are described
described using 802.11n due to its wide availability in real-world using the underlying PHY- and MAC-layer parameters based on the IEEE
networks. Statistics collected from enterprise Wi-Fi networks show 802.11n Standard. Statistics collected from enterprise Wi-Fi
that the dominant physical modes are 802.11n and 802.11ac, accounting networks show that the two dominant physical modes are 802.11n and
for 73.6% and 22.5% of enterprise network users, respectively. 802.11ac, accounting for 41% and 58% of connected devices. As Wi-Fi
standards evolve over time, for instance, with the introduction of
the emerging Wi-Fi 6 (802.11ax) products, the PHY- and MAC-layer test
case specifications need to be updated accordingly to reflect such
changes.
Typically, a Wi-Fi access network connects to a wired infrastructure. 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 could be the
bottleneck. In the following sections, we describe basic test cases bottleneck. In the following sections, we describe basic test cases
for both scenarios separately. The same set of performance metrics for both scenarios separately. The same set of performance metrics
as in [I-D.ietf-rmcat-eval-test]) should be collected for each test as in [I-D.ietf-rmcat-eval-test]) should be collected for each test
case. case.
While all test cases described below can be carried out using All test cases described below can be carried out using simulations,
simulations, e.g. based on [ns-2] or [ns-3], it is also recommended e.g. based on [ns-2] or [ns-3]. When feasible, it is also encouraged
to perform testbed-based evaluations using Wi-Fi access points and to perform testbed-based evaluations using Wi-Fi access points and
endpoints running up-to-date IEEE 802.11 protocols. [Editor's Note: endpoints running up-to-date IEEE 802.11 protocols, such as 802.11ac
need to add some more discussions on the pros and cons of simulation- and the emerging Wi-Fi 6, to verify the viability of the candidate
based vs. testbed-based evaluations. Will be good to provide schemes.
recommended testbed configurations. ]
4.1. Bottleneck in Wired Network 4.1. Bottleneck in Wired Network
The test scenarios below are intended to mimic the set up 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 from test
cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), it cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), it
is worthwhile to run through these tests as sanity checks. is worthwhile to run through these tests as sanity checks.
4.1.1. Network topology 4.1.1. Network topology
Figure 2 shows topology of the network for Wi-Fi test cases. The Figure 2 shows topology of the network for Wi-Fi test cases. The
skipping to change at page 14, line 4 skipping to change at page 14, line 30
- Start time: 0s. - Start time: 0s.
- End time: 119s. - End time: 119s.
* 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 4.1.3 + Traffic direction: See Section 4.1.3
+ Number of sources (M): See Section 4.1.3 + Number of sources (M): See Section 4.1.3
+ Congestion control: Default TCP congestion control [TBD] or + Congestion control: Default TCP congestion control [RFC5681]
CBR 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 RMCAT 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 RMCAT flows: N=2 (with one uplink flow
and one downlink flow); M=0. 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 RMCAT flows, one on-off CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow); flow on uplink: N=2 (with one uplink flow and one downlink flow);
M=1 (uplink). CBR flow on time at 0s-60s, off time at 60s-119s. M=1 (uplink). CBR flow ON time at 0s-60s, OFF time at 60s-119s.
o One pair of bi-directional RMCAT flows, one off-on CBR over UDP o One pair of bi-directional RMCAT flows, one off-on CBR over UDP
flow on uplink: N=2 (with one uplink flow and one downlink flow); flow on uplink: N=2 (with one uplink flow and one downlink flow);
M=1 (uplink). UDP off time: 0s-60s, on time: 60s-119s. M=1 (uplink). OFF time for UDP flow: 0s-60s; ON time: 60s-119s.
o One RMCAT flow competing against one long-live TCP flow over o One RMCAT flow competing against one long-live TCP flow over
uplink: N=1 (uplink) and M = 1(uplink), TCP start time at 0s and uplink: N=1 (uplink) and M = 1(uplink), TCP start time at 0s and
end time at 119s. end time at 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 RMCAT flow: the candidate algorithm is expected to
detect the path capacity constraint, to converge to bottleneck detect the path capacity constraint, to converge to bottleneck
link capacity and to adapt the flow to avoid unwanted oscillation link capacity and to adapt the flow to avoid unwanted oscillation
skipping to change at page 16, line 18 skipping to change at page 16, line 43
- End time: 119s. - End time: 119s.
* 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 4.2.3 + Number of sources (M): See Section 4.2.3
+ Traffic direction: See Section 4.2.3 + Traffic direction: See Section 4.2.3
+ Congestion control: Default TCP congestion control [TBD] or + Congestion control: Default TCP congestion control [RFC5681]
CBR 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 RMCAT candidate important for understanding the behavior of a RMCAT candidate
solution over a Wi-Fi network. solution over a Wi-Fi network.
o Multiple RMCAT Flows Sharing the Wireless Downlink: N=16 (all o Multiple RMCAT Flows Sharing the Wireless Downlink: N=16 (all
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packets uplink over the wireless interface, they introduce more packets uplink over the wireless interface, they introduce 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 solution
should focus on whether uplink flows can stablize at a fair share should focus on whether uplink flows can stablize at a fair share
of application-layer throughput. of application-layer throughput.
o Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8 o Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8
downlink); M = 0. The goal of this test is to evaluate downlink); M = 0. The goal of this test is to evaluate
performance of the candidate solution in terms of bandwidth performance of the candidate solution in terms of bandwidth
fairness between uplink and downlink flow. fairness between uplink and downlink flows.
o Multiple Bi-directional RMCAT Flows with on-off CBR traffic: N = o Multiple Bi-directional RMCAT Flows with on-off CBR traffic: N =
16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this 16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this
test is to evaluate adaptation behavior of the candidate solution test is to evaluate adaptation behavior of the candidate solution
when its available bandwidth changes due to departure of when its available bandwidth changes due to departure of
background traffic. The background traffic consists of several background traffic. The background traffic consists of several
(e.g., M=5) CBR flows transported over UDP, which are ON at times (e.g., M=5) CBR flows transported over UDP, which are ON at times
t=0-60s and are OFF at times t=61-120s. t=0-60s and are OFF at times t=61-120s.
o Multiple Bi-directional RMCAT Flows with off-on CBR traffic: N = o Multiple Bi-directional RMCAT Flows with off-on CBR traffic: N =
16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this 16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this
test is to evaluate adaptation behavior of the candidate solution test is to evaluate adaptation behavior of the candidate solution
when its available bandwidth changes due to arrival of background when its available bandwidth changes due to arrival of background
traffic. The background traffic consists of several (e.g., M=5) traffic. The background traffic consists of several (e.g., M=5)
parallel CBR flows transported over UDP, which are OFF at times parallel CBR flows transported over UDP, which are OFF at times
t=0-60s and are ON at times t=61-120s. t=0-60s and are ON at times t=61-120s.
o Multiple RMCAT flows in the presence of background TCP traffic. o Multiple Bi-directional RMCAT flows in the presence of background
The goal of this test is to evaluate how RMCAT flows compete TCP traffic: N=16 (8 uplink and 8 downlink); M = 5 (uplink). The
against TCP over a congested Wi-Fi network for a given candidate goal of this test is to evaluate how RMCAT flows compete against
solution. TCP start time: 0s, end time: 119s. [Editor's Note: TCP over a congested Wi-Fi network for a given candidate solution.
need to add the number of recommended RMCAT and TCP flows] TCP start time: 40s, end time: 80s.
o Varying number of RMCAT flows. The goal of this test is to o Varying number of RMCAT flows. A series of tests can be carried
evaluate how a candidate RMCAT solution responds to varying out for the above test cases with different values of N, e.g., N =
traffic load/demand over a congested Wi-Fi network. [Editor's [4, 8, 12, 16, 20]. The goal of this test is to evaluate how a
Note: need to specify recommended arrival/departure pattern of candidate RMCAT solution responds to varying traffic load/demand
RMCAT flows] over a congested Wi-Fi network. The start time of these RMCAT
flows is randomly distributed within a window of t=0-10s, whereas
their end times are randomly distributed within a window of
t=110-120s.
4.2.4. Expected behavior 4.2.4. Expected behavior
o Multiple downlink RMCAT flows: each RMCAT flow should get its fair o Multiple downlink RMCAT flows: each RMCAT flow should get its fair
share of the total bottleneck link bandwidth. Overall bandwidth share of the total bottleneck link bandwidth. Overall bandwidth
usage should not be significantly lower than that experienced by usage should not be significantly lower than that experienced by
the same number of concurrent downlink TCP flows. In other words, the same number of concurrent downlink TCP flows. In other words,
the performance of multiple concurrent TCP flows will be used as a the performance of multiple concurrent TCP flows will be used as a
performance benchmark for this test scenario. The end-to-end performance benchmark for this test scenario. The end-to-end
delay and packet loss ratio experienced by each flow should be delay and packet loss ratio experienced by each flow should be
within acceptable range for real-time multimedia applications. within acceptable range for real-time multimedia applications.
o Multiple uplink RMCAT flows: overall bandwidth usage shared by all o Multiple uplink RMCAT flows: overall bandwidth usage shared by all
RMCAT flows should not be significantly lower than that RMCAT 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 performance of multiple concurrent TCP flows will
be used as a performance benchmark for this test scenario. be used as a performance benchmark for this test scenario.
o Multiple bi-directional RMCAT flows with dynamic background o Multiple bi-directional RMCAT flows with dynamic background
traffic carry CBR flows over UDP: RMCAT flows should adapt in a traffic carrying CBR flows over UDP: RMCAT flows should adapt in a
timely fashion to the resulting changes in available bandwidth. timely fashion to the resulting changes in available bandwidth.
o Multiple bi-directional RMCAT flows with TCP traffic: overall o Multiple bi-directional RMCAT flows with dynamic background
bandwidth usage shared by all RMCAT flows should not be traffic over TCP: during the presence of TCP background flows, the
overall bandwidth usage shared by all RMCAT flows should not be
significantly lower than those achieved by the same number of bi- significantly lower than those achieved by the same number of bi-
directional TCP flows. In other words, the performance of directional TCP flows. In other words, the performance 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 RMCAT flows are
expected to obtain similar bandwidth with respect to each other. expected to obtain similar bandwidth with respect to each other.
The throughput of RMCAT flows should decrease upon the arrival of
TCP background traffic and increase upon their departure, both
reactions should occur in a timely fashion (e.g., within 10s of
seconds).
o Varying number of RMCAT flows: the test results for varying values
of N -- while keeping all other parameters constant -- is expected
to show steady and stable per-flow throughtput for each value of
N. The average throughput of all RMCAT flows is expected to stay
constant around the maximum rate when N is small, then gradually
decrease with increasing number of RMCAT flows till it reaches the
minimum allowed rate, beyond which the offered load to the Wi-Fi
network (with a large value of N) is exceeding its capacity.
4.3. Other Potential Test Cases 4.3. 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 EDCA/WMM is prioritized QoS with four traffic classes (or Access
Categories) with differing priorities. RMCAT flows should achieve Categories) with differing priorities. RMCAT flows should achieve
better performance (i.e., lower delay, fewer packet losses) with better performance (i.e., lower delay, fewer packet losses) with
EDCA/WMM enabled when competing against non-interactive background EDCA/WMM enabled when competing against non-interactive background
traffic (e.g., file transfers). When most of the traffic over Wi-Fi traffic (e.g., file transfers). When most of the traffic over Wi-Fi
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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 evaluation of the test cases are intended to be run in a The evaluation of the test cases are intended to be run 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 from unproven congestion
avoidance techniques onto the open Internet. avoidance techniques onto the open Internet.
8. Acknowledgements 8. Acknowledgments
We would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer We would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer
Sandlund for their valuable comments while writing this draft. Sandlund, and Sergio Mena de la Cruz for their valuable input and
review comments regarding this draft.
9. References 9. References
9.1. Normative References 9.1. Normative References
[Deployment] [Deployment]
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>.
skipping to change at page 20, line 28 skipping to change at page 21, line 19
[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, [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>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [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 9.2. Informative References
[Heusse2003]
Heusse, M., Rousseau, F., Berger-Sabbatel, G., and A.
Duda, "Performance anomaly of 802.11b", in Proc. 23th
Annual Joint Conference of the IEEE Computer and
Communications Societies, (INFOCOM'03), March 2003.
[I-D.ietf-rmcat-cc-requirements] [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] [I-D.ietf-rmcat-eval-test]
Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test
Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat- Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat-
eval-test-08 (work in progress), November 2018. eval-test-10 (work in progress), May 2019.
[IEEE802.11] [IEEE802.11]
"Standard for Information technology--Telecommunications IEEE, "Standard for Information technology--
and information exchange between systems Local and Telecommunications and information exchange between
metropolitan area networks--Specific requirements Part 11: systems Local and metropolitan area networks--Specific
Wireless LAN Medium Access Control (MAC) and Physical requirements Part 11: Wireless LAN Medium Access Control
Layer (PHY) Specifications", 2012. (MAC) and Physical Layer (PHY) Specifications", 2012.
[LTE-simulator] [LTE-simulator]
"NS-3, A discrete-Event Network Simulator", "NS-3, A discrete-Event Network Simulator",
<https://www.nsnam.org/docs/release/3.23/manual/html/ <https://www.nsnam.org/docs/release/3.23/manual/html/
index.html>. index.html>.
[ns-2] "The Network Simulator - ns-2", [ns-2] "The Network Simulator - ns-2",
<http://www.isi.edu/nsnam/ns/>. <http://www.isi.edu/nsnam/ns/>.
[ns-3] "The Network Simulator - ns-3", <https://www.nsnam.org/>. [ns-3] "The Network Simulator - ns-3", <https://www.nsnam.org/>.
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