--- 1/draft-ietf-rmcat-wireless-tests-09.txt 2020-03-10 09:13:19.779228026 -0700 +++ 2/draft-ietf-rmcat-wireless-tests-10.txt 2020-03-10 09:13:19.827229242 -0700 @@ -1,25 +1,24 @@ Network Working Group Z. Sarker -Internet-Draft I. Johansson -Intended status: Informational Ericsson AB -Expires: August 30, 2020 X. Zhu - J. Fu +Internet-Draft Ericsson AB +Intended status: Informational X. Zhu +Expires: September 10, 2020 J. Fu W. Tan Cisco Systems M. Ramalho AcousticComms - February 27, 2020 + March 9, 2020 Evaluation Test Cases for Interactive Real-Time Media over Wireless Networks - draft-ietf-rmcat-wireless-tests-09 + draft-ietf-rmcat-wireless-tests-10 Abstract The Real-time Transport Protocol (RTP) is a common transport choice for interactive multimedia communication applications. The performance of these applications typically depends on a well- functioning congestion control algorithm. To ensure a seamless and robust user experience, a well-designed RTP-based congestion control algorithm should work well across all access network types. This document describes test cases for evaluating performances of @@ -34,111 +33,103 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on August 30, 2020. + This Internet-Draft will expire on September 10, 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Cellular Network Specific Test Cases . . . . . . . . . . . . 3 - 3.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6 - 3.1.1. Network Connection . . . . . . . . . . . . . . . . . 6 - 3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 - 3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 9 - 3.2.1. Network connection . . . . . . . . . . . . . . . . . 9 - 3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 - 3.3. Desired Evaluation Metrics for cellular test cases . . . 10 - 4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 - 4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 - 4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 - 4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13 - 4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 - 4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15 - 4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15 - 4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 - 4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15 - 4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17 - 4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18 - 4.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19 - 4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19 - 4.3.2. Effect of heterogeneous link rates . . . . . . . . . 19 - 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 20 - 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 20 - 8.2. Informative References . . . . . . . . . . . . . . . . . 21 + 2. Cellular Network Specific Test Cases . . . . . . . . . . . . 3 + 2.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6 + 2.1.1. Network Connection . . . . . . . . . . . . . . . . . 6 + 2.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 + 2.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 9 + 2.2.1. Network connection . . . . . . . . . . . . . . . . . 9 + 2.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 + 2.3. Desired Evaluation Metrics for cellular test cases . . . 10 + 3. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 + 3.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 + 3.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 + 3.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13 + 3.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 + 3.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 15 + 3.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15 + 3.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 + 3.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15 + 3.2.3. Typical test scenarios . . . . . . . . . . . . . . . 17 + 3.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 18 + 3.3. Other Potential Test Cases . . . . . . . . . . . . . . . 19 + 3.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 19 + 3.3.2. Effect of heterogeneous link rates . . . . . . . . . 19 + 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 + 5. Security Considerations . . . . . . . . . . . . . . . . . . . 20 + 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 + 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 + 7.1. Normative References . . . . . . . . . . . . . . . . . . 20 + 7.2. Informative References . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 1. Introduction Wireless networks (both cellular and Wi-Fi [IEEE802.11]) are an integral and increasingly more significant part of the Internet. Typical application scenarios for interactive multimedia communication over wireless include from video conferencing calls in a bus or train as well as live media streaming at home. It is well known that the characteristics and technical challenges for supporting multimedia services over wireless are very different from those of providing the same service over a wired network. Although the basic test cases as defined in [I-D.ietf-rmcat-eval-test] have covered many common effects of network impairments for evaluating RTP-based congestion control schemes, they remain to be tested over characteristics and dynamics unique to a given wireless environment. For example, in cellular networks, the base station maintains individual queues per radio bearer per user hence it leads to a different nature of interactions between traffic flows of different - users. This contrasts with the wired network setting where traffic - flows from all users share the same queue. Furthermore, user - mobility patterns in a cellular network differ from those in a Wi-Fi - network. Therefore, it is important to evaluate the performance of - proposed candidate RTP-based congestion control solutions over - cellular mobile networks and over Wi-Fi networks respectively. + users. This contrasts with a typical wired network setting where + traffic flows from all users share the same queue at the bottleneck. + Furthermore, user mobility patterns in a cellular network differ from + those in a Wi-Fi network. Therefore, it is important to evaluate the + performance of proposed candidate RTP-based congestion control + solutions over cellular mobile networks and over Wi-Fi networks + respectively. The draft [I-D.ietf-rmcat-eval-criteria] provides the guideline for evaluating candidate algorithms and recognizes the importance of testing over wireless access networks. However, it does not describe any specific test cases for performance evaluation of candidate algorithms. This document describes test cases specifically targeting cellular and Wi-Fi networks. -2. Terminologies - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and - "OPTIONAL" in this document are to be interpreted as described in BCP - 14 [RFC2119] [RFC8174] when, and only when, they appear in all - capitals, as shown here. - -3. Cellular Network Specific Test Cases +2. Cellular Network Specific Test Cases A cellular environment is more complicated than its wireline counterpart since it seeks to provide services in the context of variable available bandwidth, location dependencies and user mobilities at different speeds. In a cellular network, the user may reach the cell edge which may lead to a significant amount of retransmissions to deliver the data from the base station to the destination and vice versa. These radio links will often act as a bottleneck for the rest of the network and will eventually lead to excessive delays or packet drops. An efficient retransmission or @@ -194,22 +185,22 @@ cellular network needs to cope with a shared bottleneck link and variable link capacity, events like handover, non-congestion related loss, abrupt changes in bandwidth (both short term and long term) due to handover, network load and bad radio coverage. Even though 3GPP has defined QoS bearers [QoS-3GPP] to ensure high-quality user experience, it is still preferable for real-time applications to behave in an adaptive manner. Different mobile operators deploy their own cellular networks with their own set of network functionalities and policies. Usually, a - mobile operator network includes 2G, EDGE, 3G and 4G radio access - technologies. Looking at the specifications of such radio + mobile operator network includes a range of radio access technologies + such as 3G and 4G/LTE. Looking at the specifications of such radio technologies it is evident that only the more recent radio technologies can support the high bandwidth requirements from real- time interactive video applications. The future real-time interactive application will impose even greater demand on cellular network performance which makes 4G (and beyond) radio technologies more suitable for such genre of application. The key factors in defining test cases for cellular networks are: o Shared and varying link capacity @@ -240,46 +231,48 @@ that these networks are controlled by cellular operators and there exist various amounts of competing traffic in the same cell(s). In practice, it is only in underground mines that one can carry out near deterministic testing. Even there, it is not guaranteed either as workers in the mines may carry with them their personal mobile phones. Furthermore, the underground mining setting may not reflect typical usage patterns in an urban setting. We, therefore, recommend that a cellular network simulator is used for the test cases defined in this document, for example -- the LTE simulator in [NS-3]. -3.1. Varying Network Load +2.1. Varying Network Load The goal of this test is to evaluate the performance of the candidate congestion control algorithm under varying network load. The network load variation is created by adding and removing network users a.k.a. User Equipments (UEs) during the simulation. In this test case, each user/UE in the media session is an endpoint following RTP-based congestion control. User arrivals follow a Poisson distribution proportional to the length of the call, to keep the number of users per cell fairly constant during the evaluation period. At the beginning of the simulation, there should be enough time to warm-up the network. This is to avoid running the evaluation in an empty network where network nodes are having empty buffers, low interference at the beginning of the simulation. This network initialization period should be excluded from the evaluation period. + Typically, the evaluation period starts 30 seconds after test + initialization. This test case also includes user mobility and some competing traffic. The latter includes both the same types of flows (with same adaptation algorithms) and different types of flows (with different services and congestion control schemes). The investigated congestion control algorithms should show maximum possible network utilization and stability in terms of rate variations, lowest possible end to end frame latency, network latency and Packet Loss Rate (PLR) at different cell load level. -3.1.1. Network Connection +2.1.1. Network Connection Each mobile user is connected to a fixed user. The connection between the mobile user and fixed user consists of a cellular radio access, an Evolved Packet Core (EPC) and an Internet connection. The mobile user is connected to the EPC using cellular radio access technology which is further connected to the Internet. At the other end, the fixed user is connected to the Internet via wired connection with sufficiently high bandwidth, for instance, 10 Gbps, so that the system bottleneck is on the cellular radio access interface. The wired connection to in this setup does not introduce any network @@ -297,36 +290,37 @@ ++-+ ((o)) | | / \ +-------+ +------+ +---+ +--+ / \----+ +-----+ +----+ | / \ +-------+ +------+ +---+ UE BS EPC Internet fixed <--------------------------+ downlink Figure 1: Simulation Topology -3.1.2. Simulation Setup +2.1.2. Simulation Setup The values enclosed within "[ ]" for the following simulation attributes follow the same notion as in [I-D.ietf-rmcat-eval-test]. The desired simulation setup is as follows -- 1. Radio environment: A. Deployment and propagation model: 3GPP case 1 (see [HO-deploy-3GPP]) - B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D] + B. Antenna: Multiple-Input and Multiple-Output (MIMO), 2D or 3D + antenna pattern. 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 Station (BS) * 7 BS) = 21 cells F. Cell radius: 166.666 Meters G. Scheduler: Proportional fair with no priority H. Bearer: Default bearer for all traffic. @@ -377,98 +370,101 @@ 8. Other traffic models: * Downlink simulation: Maximum of 4Mbps/cell (web browsing or FTP traffic following default TCP congestion control [RFC5681]) * Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP traffic following default TCP congestion control [RFC5681]) -3.2. Bad Radio Coverage +2.2. Bad Radio Coverage The goal of this test is to evaluate the performance of candidate congestion control algorithm when users visit part of the network with bad radio coverage. The scenario is created by using a larger cell radius than that in the previous test case. In this test case, - each user/UE in the media session is an RMCAT compliant endpoint. - User arrivals follow a Poisson distribution proportional to the - length of the call, to keep the number of users per cell fairly - constant during the evaluation period. At the beginning of the - simulation, there should be enough amount of time to warm-up the - network. This is to avoid running the evaluation in an empty network - where network nodes are having empty buffers, low interference at the - beginning of the simulation. This network initialization period - should be excluded from the evaluation period. + each user/UE in the media session is an endpoint following RTP-based + congestion control. User arrivals follow a Poisson distribution + proportional to the length of the call, to keep the number of users + per cell fairly constant during the evaluation period. At the + beginning of the simulation, there should be enough amount of time to + warm-up the network. This is to avoid running the evaluation in an + empty network where network nodes are having empty buffers, low + interference at the beginning of the simulation. This network + initialization period should be excluded from the evaluation period. + Typically, the evaluation period starts 30 seconds after test + initialization. This test case also includes user mobility and some competing traffic. The latter includes the same kind of flows (with same adaptation algorithms). The investigated congestion control algorithms should result in maximum possible network utilization and stability in terms of rate variations, lowest possible end to end frame latency, network latency and Packet Loss Rate (PLR) at different cell load levels. -3.2.1. Network connection +2.2.1. Network connection - Same as defined in Section 3.1.1 + Same as defined in Section 2.1.1 -3.2.2. Simulation Setup +2.2.2. Simulation Setup The desired simulation setup is the same as the Varying Network Load - test case defined in Section 3.1 except the following changes: + test case defined in Section 2.1 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 2.1.2 except the following: A. Deployment and propagation model: 3GPP case 3 (see [HO-deploy-3GPP]) B. Cell radius: 577.3333 Meters + C. Mobility: 3km/h 2. User intensity = {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3, 7.0} - 3. Media traffic model: Same as defined in Section 3.1.2 + 3. Media traffic model: Same as defined in Section 2.1.2 4. Other traffic models: * Downlink simulation: Maximum of 2Mbps/cell (web browsing or FTP traffic following default TCP congestion control [RFC5681]) * Unlink simulation: Maximum of 1Mbps/cell (web browsing or FTP traffic following default TCP congestion control [RFC5681]) -3.3. Desired Evaluation Metrics for cellular test cases +2.3. Desired Evaluation Metrics for cellular test cases The evaluation criteria document [I-D.ietf-rmcat-eval-criteria] defines the metrics to be used to evaluate candidate algorithms. Considering the nature and distinction of cellular networks we recommend that at least the following metrics be used to evaluate the performance of the candidate algorithms: o Average cell throughput (for all cells), shows cell utilizations. o Application sending and receiving bitrate, goodput. o Packet Loss Rate (PLR). o End-to-end Media frame delay. For video, this means the delay from capture to display. o Transport delay. o Algorithm stability in terms of rate variation. -4. Wi-Fi Networks Specific Test Cases +3. Wi-Fi Networks Specific Test Cases Given the prevalence of Internet access links over Wi-Fi, it is important to evaluate candidate RTP-based congestion control solutions over test cases that include Wi-Fi access links. Such evaluations should highlight the inherently different characteristics of Wi-Fi networks in contrast to their wired counterparts: o The wireless radio channel is subject to interference from nearby transmitters, multipath fading, and shadowing. These effects lead to fluctuations in the link throughput and sometimes an error- @@ -539,31 +535,31 @@ both scenarios separately. The same set of performance metrics as in [I-D.ietf-rmcat-eval-test]) should be collected for each test case. We recommend to carry out the test cases as defined in this document using a simulator, such as [NS-2] or [NS-3]. When feasible, it is encouraged to perform testbed-based evaluations using Wi-Fi access points and endpoints running up-to-date IEEE 802.11 protocols, such as 802.11ac and the emerging Wi-Fi 6, so as to verify the viability of the candidate schemes. -4.1. Bottleneck in Wired Network +3.1. Bottleneck in Wired Network The test scenarios below are intended to mimic the setup of video conferencing over Wi-Fi connections from the home. Typically, the Wi-Fi home network is not congested and the bottleneck is present over the wired home access link. Although it is expected that test evaluation results from this section are similar to those as in [I-D.ietf-rmcat-eval-test], it is still worthwhile to run through these tests as sanity checks. -4.1.1. Network topology +3.1.1. Network topology Figure 2 shows the network topology of Wi-Fi test cases. The test contains multiple mobile nodes (MNs) connected to a common Wi-Fi access point (AP) and their corresponding wired clients on fixed nodes (FNs). Each connection carries either a RTP-based media flow or a TCP traffic flow. Directions of the flows can be uplink (i.e., 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. @@ -587,21 +583,21 @@ . )) \\ . . )) \\ . +----------+ )) \\ +----------+ | MN_tcp_M |))) \=====| FN_tcp_M | +----------+ +----------+ +<-----------------+ Downlink Figure 2: Network topology for Wi-Fi test cases -4.1.2. Test setup +3.1.2. Test setup o Test duration: 120s o Wi-Fi network characteristics: * Radio propagation model: Log-distance path loss propagation model (see [NS3WiFi]) * PHY- and MAC-layer configuration: IEEE 802.11n @@ -620,97 +616,97 @@ * Bottleneck queue size: 300ms. * Path loss ratio: 0%. o Application characteristics: * Media Traffic: + Media type: Video - + Media direction: See Section 4.1.3 + + Media direction: See Section 3.1.3 - + Number of media sources (N): See Section 4.1.3 + + Number of media sources (N): See Section 3.1.3 + Media timeline: - Start time: 0s. - End time: 119s. * Competing traffic: + Type of sources: long-lived TCP or CBR over UDP - + Traffic direction: See Section 4.1.3 + + Traffic direction: See Section 3.1.3 - + Number of sources (M): See Section 4.1.3 + + Number of sources (M): See Section 3.1.3 + Congestion control: Default TCP congestion control [RFC5681] or constant-bit-rate (CBR) traffic over UDP. - + Traffic timeline: See Section 4.1.3 + + Traffic timeline: See Section 3.1.3 -4.1.3. Typical test scenarios +3.1.3. Typical test scenarios o Single uplink RTP-based media flow: N=1 with uplink direction and M=0. o One pair of bi-directional RTP-based media flows: N=2 (i.e., one uplink flow and one downlink flow); M=0. o One pair of bi-directional RTP-based media flows: N=2; one uplink on-off CBR flow over UDP: M=1 (uplink). The CBR flow has ON time at t=0s-60s and OFF time at t=60s-119s. o One pair of bi-directional RTP-based media flows: N=2; one uplink off-on CBR flow over UDP: M=1 (uplink). The CBR flow has OFF time at t=0s-60s and ON time at t=60s-119s. o One RTP-based media flow competing against one long-live TCP flow in the uplink direction: N=1 (uplink) and M = 1(uplink). The TCP flow has start time at t=0s and end time at t=119s. -4.1.4. Expected behavior +3.1.4. Expected behavior o Single uplink RTP-based media flow: the candidate algorithm is expected to detect the path capacity constraint, to converge to the bottleneck link capacity, and to adapt the flow to avoid unwanted oscillations when the sending bit rate is approaching the bottleneck link capacity. No excessive oscillations in the media rate should be present. o Bi-directional RTP-based media flows: the candidate algorithm is expected to converge to the bottleneck capacity of the wired path in both directions despite the presence of measurement noise over the Wi-Fi connection. In the presence of background TCP or CBR over UDP traffic, the rate of RTP-based media flows should adapt promptly to the arrival and departure of background traffic flows. o One RTP-based media flow competing with long-live TCP flow in the uplink direction: the candidate algorithm is expected to avoid congestion collapse and to stabilize at a fair share of the bottleneck link capacity. -4.2. Bottleneck in Wi-Fi Network +3.2. Bottleneck in Wi-Fi Network The test cases in this section assume that the wired segment along the media path is well-provisioned whereas the bottleneck exists over the Wi-Fi access network. This is to mimic the application scenarios typically encountered by users in an enterprise environment or at a coffee house. -4.2.1. Network topology +3.2.1. Network topology - Same as defined in Section 4.1.1 + Same as defined in Section 3.1.1 -4.2.2. Test setup +3.2.2. Test setup o Test duration: 120s o Wi-Fi network characteristics: * Radio propagation model: Log-distance path loss propagation model (see [NS3WiFi]) * PHY- and MAC-layer configuration: IEEE 802.11n * MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps @@ -728,71 +724,71 @@ * Bottleneck queue size: 300ms. * Path loss ratio: 0%. o Application characteristics: * Media Traffic: + Media type: Video - + Media direction: See Section 4.2.3. + + Media direction: See Section 3.2.3. - + Number of media sources (N): See Section 4.2.3. + + Number of media sources (N): See Section 3.2.3. + Media timeline: - Start time: 0s. - End time: 119s. * Competing traffic: + Type of sources: long-lived TCP or CBR over UDP. - + Number of sources (M): See Section 4.2.3. + + Number of sources (M): See Section 3.2.3. - + Traffic direction: See Section 4.2.3. + + Traffic direction: See Section 3.2.3. + Congestion control: Default TCP congestion control [RFC5681] or constant-bit-rate (CBR) traffic over UDP. - + Traffic timeline: See Section 4.2.3. + + Traffic timeline: See Section 3.2.3. -4.2.3. Typical test scenarios +3.2.3. Typical test scenarios This section describes a few test scenarios that are deemed as important for understanding the behavior of a candidate RTP-based congestion control scheme over a Wi-Fi network. a. Multiple RTP-based media flows sharing the wireless downlink: N=16 (all downlink); M = 0. This test case is for studying the impact of contention on the multiple concurrent media flows. For an 802.11n network, given the MCS Index of 11 and the corresponding link rate of 52Mbps, the total application-layer throughput (assuming reasonable distance, low interference and infrequent contentions caused by competing streams) is around 20Mbps. A total of N=16 RTP-based media flows (with a maximum rate of 1.5Mbps each) are expected to saturate the wireless interface in this experiment. Evaluation of a given candidate scheme should focus on whether the downlink media flows can stabilize at a fair share of the total application-layer throughput. - b. Multiple RTP-based media flows sharing the wireless uplink:N = 16 - (all downlink); M = 0. When multiple clients attempt to transmit - media packets uplink over the Wi-Fi network, they introduce more - frequent contentions and potential collisions. Per-flow - throughput is expected to be lower than that in the previous - downlink-only scenario. Evaluation of a given candidate scheme - should focus on whether the uplink flows can stabilize at a fair - share of the total application-layer throughput. + b. Multiple RTP-based media flows sharing the wireless uplink: N = + 16 (all uplink); M = 0. When multiple clients attempt to + transmit media packets uplink over the Wi-Fi network, they + introduce more frequent contentions and potential collisions. + Per-flow throughput is expected to be lower than that in the + previous downlink-only scenario. Evaluation of a given candidate + scheme should focus on whether the uplink flows can stabilize at + a fair share of the total application-layer throughput. c. Multiple bi-directional RTP-based media flows: N = 16 (8 uplink and 8 downlink); M = 0. The goal of this test is to evaluate the performance of the candidate scheme in terms of bandwidth fairness between uplink and downlink flows. d. Multiple bi-directional RTP-based media flows with on-off CBR 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 @@ -819,21 +815,21 @@ g. Varying number of RTP-based media flows: A series of tests can be carried out for the above test cases with different values of N, e.g., N = [4, 8, 12, 16, 20]. The goal of this test is to evaluate how a candidate scheme responds to varying traffic load/ demand over a congested Wi-Fi network. The start times of the media flows are randomly distributes within a window of t=0-10s; their end times are randomly distributed within a window of t=110-120s. -4.2.4. Expected behavior +3.2.4. Expected behavior o Multiple downlink RTP-based media flows: each media flow is expected to get its fair share of the total bottleneck link bandwidth. Overall bandwidth usage should not be significantly lower than that experienced by the same number of concurrent downlink TCP flows. In other words, the behavior of multiple concurrent TCP flows will be used as a performance benchmark for this test scenario. The end-to-end delay and packet loss ratio experienced by each flow should be within an acceptable range for real-time multimedia applications. @@ -866,76 +862,82 @@ o Varying number of bi-directional RTP-based media flows: the test results for varying values of N -- while keeping all other parameters constant -- is expected to show steady and stable per- flow throughput for each value of N. The average throughput of all media flows is expected to stay constant around the maximum rate when N is small, then gradually decrease with increasing value of N till it reaches the minimum allowed rate, beyond which the offered load to the Wi-Fi network exceeds its capacity (i.e., with a very large value of N). -4.3. Other Potential Test Cases +3.3. Other Potential Test Cases -4.3.1. EDCA/WMM usage +3.3.1. EDCA/WMM usage The EDCA/WMM mechanism defines prioritized QoS for four traffic classes (or Access Categories). RTP-based real-time media flows should achieve better performance in terms of lower delay and fewer packet losses with EDCA/WMM enabled when competing against non- interactive background traffic such as file transfers. When most of the traffic over Wi-Fi is dominated by media, however, turning on WMM may degrade performance since all media flows now attempt to access the wireless transmission medium more aggressively, thereby causing more frequent collisions and collision-induced losses. This is a topic worthy of further investigation. -4.3.2. Effect of heterogeneous link rates +3.3.2. Effect of heterogeneous link rates As discussed in [Heusse2003], the presence of clients operating over slow PHY-layer link rates (e.g., a legacy 802.11b device) connected to a modern network may adversely impact the overall performance of 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. -5. IANA Considerations +4. IANA Considerations This memo includes no request to IANA. -6. Security Considerations +5. Security Considerations The security considerations in [I-D.ietf-rmcat-eval-criteria] and the relevant congestion control algorithms apply. The principles for congestion control are described in [RFC2914], and in particular, any - new method MUST implement safeguards to avoid congestion collapse of + new method must implement safeguards to avoid congestion collapse of the Internet. - The evaluations of the test cases are intended to carry out in a - controlled lab environment. Hence, the applications, simulators and - network nodes ought to be well-behaved and should not impact the - desired results. It is important to take appropriate caution to - avoid leaking non-responsive traffic with unproven congestion - avoidance behavior onto the open Internet. + Given the difficulty of deterministic wireless testing, it is + recommended and expected that the tests described in this document + would be done via simulations. However, in the case where these test + cases are carried out in a testbed setting, the evaluation should + take place in a controlled lab environment. In the testbed, the + applications, simulators and network nodes ought to be well-behaved + and should not impact the desired results. It is important to take + appropriate caution to avoid leaking non-responsive traffic with + unproven congestion avoidance behavior onto the open Internet. -7. Acknowledgments +6. Acknowledgments + + The authors would like to thank Ingemar Johansson for contributing to + the cellular test cases during the earlier stage of this draft. The authors would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer Sandlund, Sergio Mena de la Cruz, and Mirja Kuehlewind for their valuable inputs and review comments regarding this draft. -8. References +7. References -8.1. Normative References +7.1. Normative References [HO-deploy-3GPP] TS 25.814, 3GPP., "Physical layer aspects for evolved Universal Terrestrial Radio Access (UTRA)", October 2006, . [I-D.ietf-rmcat-eval-criteria] Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion Control for Interactive Real-time Media", draft-ietf- @@ -950,34 +952,29 @@ 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", . - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, - DOI 10.17487/RFC2119, March 1997, - . - [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion Control", RFC 5681, DOI 10.17487/RFC5681, September 2009, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -8.2. Informative References +7.2. Informative References [Heusse2003] Heusse, M., Rousseau, F., Berger-Sabbatel, G., and A. Duda, "Performance anomaly of 802.11b", in Proc. 23th Annual Joint Conference of the IEEE Computer and Communications Societies, (INFOCOM'03), March 2003. [HO-def-3GPP] TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications", December 2009, . [HO-UMTS-3GPP] TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol specification", December 2011, . - [I-D.ietf-rmcat-cc-requirements] - Jesup, R. and Z. Sarker, "Congestion Control Requirements - for Interactive Real-Time Media", draft-ietf-rmcat-cc- - requirements-09 (work in progress), December 2014. - [NS-2] "ns-2", December 2014, . [NS-3] "ns-3 Network Simulator", . [QoS-3GPP] TS 23.203, 3GPP., "Policy and charging control architecture", June 2011, . @@ -1018,44 +1010,35 @@ Zaheduzzaman Sarker Ericsson AB Laboratoriegraend 11 Luleae 97753 Sweden Phone: +46 107173743 Email: zaheduzzaman.sarker@ericsson.com - Ingemar Johansson - Ericsson AB - Laboratoriegraend 11 - Luleae 97753 - Sweden - - Phone: +46 10 7143042 - Email: ingemar.s.johansson@ericsson.com - Xiaoqing Zhu Cisco Systems 12515 Research Blvd., Building 4 Austin, TX 78759 USA Email: xiaoqzhu@cisco.com + Jiantao Fu Cisco Systems 771 Alder Drive Milpitas, CA 95035 USA Email: jianfu@cisco.com - Wei-Tian Tan Cisco Systems 510 McCarthy Blvd Milpitas, CA 95035 USA Email: dtan2@cisco.com Michael A. Ramalho AcousticComms Consulting