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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Z. Sarker 3 Internet-Draft I. Johansson 4 Intended status: Informational Ericsson AB 5 Expires: May 18, 2017 X. Zhu 6 J. Fu 7 W. Tan 8 M. Ramalho 9 Cisco Systems 10 November 14, 2016 12 Evaluation Test Cases for Interactive Real-Time Media over Wireless 13 Networks 14 draft-ietf-rmcat-wireless-tests-03 16 Abstract 18 There is an ongoing effort in IETF RMCAT working group to standardize 19 rate adaptation algorithm(s) for real-time interactive communication. 20 To ensure seamless and robust user experience, the proposed rate 21 adaptation algorithm(s) should work well across all access network 22 types. This document describes test cases for evaluating 23 performances of the proposed rate adaptation solutions over LTE and 24 Wi-Fi networks. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on May 18, 2017. 43 Copyright Notice 45 Copyright (c) 2016 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 61 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. Cellular Network Specific Test Cases . . . . . . . . . . . . 3 63 3.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6 64 3.1.1. Network Connection . . . . . . . . . . . . . . . . . 6 65 3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 66 3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 8 67 3.2.1. Network connection . . . . . . . . . . . . . . . . . 9 68 3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 69 3.3. Desired Evaluation Metrics for cellular test cases . . . 10 70 4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 71 4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 72 4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 73 4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13 74 4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 75 4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 14 76 4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 15 77 4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 78 4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15 79 4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 16 80 4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 17 81 4.3. Potential Potential Test Cases . . . . . . . . . . . . . 18 82 4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 18 83 4.3.2. Legacy 802.11b Effects . . . . . . . . . . . . . . . 18 84 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 18 85 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 86 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 87 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 88 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 89 9.1. Normative References . . . . . . . . . . . . . . . . . . 19 90 9.2. Informative References . . . . . . . . . . . . . . . . . 20 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 93 1. Introduction 95 Wireless networks (both cellular and Wi-Fi [IEEE802.11] local area 96 network) are an integral part of the Internet. Mobile devices 97 connected to the wireless networks generate huge amount of media 98 traffic in the Internet. Application scenarios range from users 99 having a video call in the bus to media consumption by someone 100 sitting on a living room couch. It is well known that the 101 characteristics and technical challenges for offering multimedia 102 services over wireless are very different from those of providing the 103 same service over a wired network. Even though RMCAT basic test 104 cases as defined in [I-D.ietf-rmcat-eval-test] have covered many 105 effects of the impairments also visible in wireless networks, there 106 remains characteristics and dynamics unique to a given wireless 107 environment. For example, in LTE networks the base station maintains 108 queues per radio bearer per user hence it leads to a different nature 109 of interaction from that over the wired network, where traffic from 110 all users share the same queue. Furthermore, user mobility in a 111 cellular network is different than user mobility in a Wi-Fi network. 112 Therefore, It is important to evaluate performance of the proposed 113 RMCAT candidate solutions separately over cellular mobile networks 114 and over Wi-Fi local networks (i.e., IEEE 802.11xx protocol family ). 116 RMCAT evaluation criteria [I-D.ietf-rmcat-eval-criteria] document 117 provides the guideline for evaluating candidate algorithms and 118 recognizes the importance of testing over wireless access networks. 119 However, it does not describe any specific test cases for evaluating 120 performance of the candidate algorithm. This document describes test 121 cases specifically targeting cellular networks such as LTE networks 122 and Wi-Fi local networks. 124 2. Terminologies 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 128 document are to be interpreted as described in RFC2119 [RFC2119] 130 3. Cellular Network Specific Test Cases 132 A cellular environment is more complicated than a wireline ditto 133 since it seeks to provide services in the context of variable 134 available bandwidth, location dependencies and user mobilities at 135 different speeds. In a cellular network the user may reach the cell 136 edge which may lead to a significant amount of retransmissions to 137 deliver the data from the base station to the destination and vice 138 versa. These network links or radio links will often act as a 139 bottleneck for the rest of the network which will eventually lead to 140 excessive delays or packet drops. An efficient retransmission or 141 link adaptation mechanism can reduce the packet loss probability but 142 there will still be some packet losses and delay variations. 143 Moreover, with increased cell load or handover to a congested cell, 144 congestion in transport network will become even worse. Besides, 145 there are certain characteristics which make the cellular network 146 different and challenging than other types of access network such as 147 Wi-Fi and wired network. In a cellular network - 149 o The bottleneck is often a shared link with relatively few users. 151 * The cost per bit over the shared link varies over time and is 152 different for different users. 154 * Left over/ unused resource can be grabbed by other greedy 155 users. 157 o Queues are always per radio bearer hence each user can have many 158 of such queues. 160 o Users can experience both Inter and Intra Radio Access Technology 161 (RAT) handovers ("handover" definition in [HO-def-3GPP] ). 163 o Handover between cells, or change of serving cells (see in 164 [HO-LTE-3GPP] and [HO-UMTS-3GPP] ) might cause user plane 165 interruptions which can lead to bursts of packet losses, delay 166 and/or jitter. The exact behavior depends on the type of radio 167 bearer. Typically, the default best effort bearers do not 168 generate packet loss, instead packets are queued up and 169 transmitted once the handover is completed. 171 o The network part decides how much the user can transmit. 173 o The cellular network has variable link capacity per user 175 * Can vary as fast as a period of milliseconds. 177 * Depends on lots of facts (such as distance, speed, 178 interference, different flows). 180 * Uses complex and smart link adaptation which makes the link 181 behavior ever more dynamic. 183 * The scheduling priority depends on the estimated throughput. 185 o Both Quality of Service (QoS) and non-QoS radio bearers can be 186 used. 188 Hence, a real-time communication application operating in such a 189 cellular network need to cope with shared bottleneck link and 190 variable link capacity, event likes handover, non-congestion related 191 loss, abrupt change in bandwidth (both short term and long term) due 192 to handover, network load and bad radio coverage. Even though 3GPP 193 define QoS bearers [QoS-3GPP] to ensure high quality user experience, 194 adaptive real-time applications are desired. 196 Different mobile operators deploy their own cellular network with 197 their own set of network functionalities and policies. Usually, a 198 mobile operator network includes 2G, EDGE, 3G and 4G radio access 199 technologies. Looking at the specifications of such radio 200 technologies it is evident that only 3G and 4G radio technologies can 201 support the high bandwidth requirements from real-time interactive 202 video applications. The future real-time interactive application 203 will impose even greater demand on cellular network performance which 204 makes 4G (and beyond radio technologies) more suitable access 205 technology for such genre of application. 207 The key factors to define test cases for cellular network are 209 o Shared and varying link capacity 211 o Mobility 213 o Handover 215 However, for cellular network it is very hard to separate such events 216 from one another as these events are heavily related. Hence instead 217 of devising separate test cases for all those important events we 218 have divided the test case in two categories. It should be noted 219 that in the following test cases the goal is to evaluate the 220 performance of candidate algorithms over radio interface of the 221 cellular network. Hence it is assumed that the radio interface is 222 the bottleneck link between the communicating peers and that the core 223 network does not add any extra congestion in the path. Also the 224 combination of multiple access technologies such as one user has LTE 225 connection and another has Wi-Fi connection is kept out of the scope 226 of this document. However, later those additional scenarios can also 227 be added in this list of test cases. While defining the test cases 228 we assumed a typical real-time telephony scenario over cellular 229 networks where one real-time session consists of one voice stream and 230 one video stream. We recommend that an LTE network simulator is used 231 for the test cases defined in this document, for example-NS-3 LTE 232 simulator [LTE-simulator]. 234 3.1. Varying Network Load 236 The goal of this test is to evaluate the performance of the candidate 237 congestion control algorithm under varying network load. The network 238 load variation is created by adding and removing network users a.k.a. 239 User Equipments (UEs) during the simulation. In this test case, each 240 of the user/UE in the media session is an RMCAT compliant endpoint. 241 The arrival of users follows a Poisson distribution, which is 242 proportional to the length of the call, so that the number of users 243 per cell is kept fairly constant during the evaluation period. At 244 the beginning of the simulation there should be enough amount of time 245 to warm-up the network. This is to avoid running the evaluation in 246 an empty network where network nodes are having empty buffers, low 247 interference at the beginning of the simulation. This network 248 initialization period is therefore excluded from the evaluation 249 period. 251 This test case also includes user mobility and competing traffic. 252 The competing traffics includes both same kind of flows (with same 253 adaptation algorithms) and different kind of flows (with different 254 service and congestion control). The investigated congestion control 255 algorithms should show maximum possible network utilization and 256 stability in terms of rate variations, lowest possible end to end 257 frame latency, network latency and Packet Loss Rate (PLR) at 258 different cell load level. 260 3.1.1. Network Connection 262 Each mobile user is connected to a fixed user. The connection 263 between the mobile user and fixed user consists of a LTE radio 264 access, an Evolved Packet Core (EPC) and an Internet connection. The 265 mobile user is connected to the EPC using LTE radio access technology 266 which is further connected to the Internet. The fixed user is 267 connected to the Internet via wired connection with no bottleneck 268 (practically infinite bandwidth). The Internet and wired connection 269 in this setup does not add any network impairments to the test, it 270 only adds 10ms of one-way transport propagation delay. 272 The path from the fixed user to mobile user is defines as "Downlink" 273 and the path from mobile user to the fixed user is defined as 274 "Uplink". We assume that only uplink or downlink is congested for 275 the mobile users. Hence, we recommend that the uplink and downlink 276 simulations are run separately. 278 uplink 279 ++))) +--------------------------> 280 ++-+ ((o)) 281 | | / \ +-------+ +------+ +---+ 282 +--+ / \----+ +-----+ +----+ | 283 / \ +-------+ +------+ +---+ 284 UE BS EPC Internet fixed 285 <--------------------------+ 286 downlink 288 Figure 1: Simulation Topology 290 3.1.2. Simulation Setup 292 The values enclosed within " [ ] " for the following simulation 293 attributes follow the notion set in [I-D.ietf-rmcat-eval-test]. The 294 desired simulation setup as follows- 296 1. Radio environment 298 A. Deployment and propagation model : 3GPP case 1[Deployment] 300 B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D] 302 C. Mobility: [3km/h, 30km/h] 304 D. Transmission bandwidth: 10Mhz 306 E. Number of cells: multi cell deployment (3 Cells per Base 307 Station (BS) * 7 BS) = 21 cells 309 F. Cell radius: 166.666 Meters 311 G. Scheduler: Proportional fair with no priority 313 H. Bearer: Default bearer for all traffic. 315 I. Active Queue Management (AQM) settings: AQM [on,off] 317 2. End to end Round Trip Time (RTT): [ 40, 150] 319 3. User arrival model: Poisson arrival model 321 4. User intensity: 323 * Downlink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 324 5.6, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5} 326 * Uplink user intercity : {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 327 5.6, 6.3, 7.0} 329 5. Simulation duration: 91s 331 6. Evaluation period : 30s-60s 333 7. Media traffic 335 1. Media type: Video 337 a. Media direction: [Uplink, Downlink] 339 b. Number of Media source per user: One (1) 341 c. Media duration per user: 30s 343 d. Media source: same as define in section 4.3 of 344 [I-D.ietf-rmcat-eval-test] 346 2. Media Type : Audio 348 a. Media direction: Uplink and Downlink 350 b. Number of Media source per user: One (1) 352 c. Media duration per user: 30s 354 d. Media codec: Constant BitRate (CBR) 356 e. Media bitrate : 20 Kbps 358 f. Adaptation: off 360 8. Other traffic model: 362 * Downlink simulation: Maximum of 4Mbps/cell (web browsing or 363 FTP traffic) 365 * Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP 366 traffic) 368 3.2. Bad Radio Coverage 370 The goal of this test is to evaluate the performance of candidate 371 congestion control algorithm when users visit part of the network 372 with bad radio coverage. The scenario is created by using larger 373 cell radius than previous test case. In this test case each of the 374 user/UE in the media session is an RMCAT compliant endpoint. The 375 arrival of users follows a Poisson distribution, which is 376 proportional to the length of the call, so that the number of users 377 per cell is kept fairly constant during the evaluation period. At 378 the beginning of the simulation there should be enough amount of time 379 to warm-up the network. This is to avoid running the evaluation in 380 an empty network where network nodes are having empty buffers, low 381 interference at the beginning of the simulation. This network 382 initialization period is therefore excluded from the evaluation 383 period. 385 This test case also includes user mobility and competing traffic. 386 The competing traffics includes same kind of flows (with same 387 adaptation algorithms) . The investigated congestion control 388 algorithms should show maximum possible network utilization and 389 stability in terms of rate variations, lowest possible end to end 390 frame latency, network latency and Packet Loss Rate (PLR) at 391 different cell load level. 393 3.2.1. Network connection 395 Same as defined in Section 3.1.1 397 3.2.2. Simulation Setup 399 The desired simulation setup is same as Varying Network Load test 400 case defined in Section 3.1 except following changes- 402 1. Radio environment : Same as defined in Section 3.1.2 except 403 followings 405 A. Deployment and propagation model : 3GPP case 3[Deployment] 407 B. Cell radius: 577.3333 Meters 409 C. Mobility: 3km/h 411 2. User intensity = {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3, 412 7.0} 414 3. Media traffic model: Same as defined in Section 3.1.2 416 4. Other traffic model: None 418 3.3. Desired Evaluation Metrics for cellular test cases 420 RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria] 421 defines metrics to be used to evaluate candidate algorithms. 422 However, looking at the nature and distinction of cellular networks 423 we recommend at minimum following metrics to be used to evaluate the 424 performance of the candidate algorithms for the test cases defined in 425 this document. 427 The desired metrics are- 429 o Average cell throughput (for all cells), shows cell utilizations. 431 o Application sending and receiving bitrate, goodput. 433 o Packet Loss Rate (PLR). 435 o End to end Media frame delay. For video, this means the delay 436 from capture to display. 438 o Transport delay. 440 o Algorithm stability in terms of rate variation. 442 4. Wi-Fi Networks Specific Test Cases 444 Given the prevalence of Internet access links over Wi-Fi, it is 445 important to evaluate candidate RMCAT congestion control solutions 446 over test cases that include Wi-Fi access lines. Such evaluations 447 should also highlight the inherent different characteristics of Wi-Fi 448 networks in contrast to wired networks: 450 o The wireless radio channel is subject to interference from nearby 451 transmitters, multipath fading, and shadowing, causing 452 fluctuations in link throughput and sometimes an error-prone 453 communication environment 455 o Available network bandwidth is not only shared over the air 456 between cocurrent users, but also between uplink and downlink 457 traffic due to the half duplex nature of wireless transmission 458 medium. 460 o Packet transmissions over Wi-Fi are susceptible to contentions and 461 collisions over the air. Consequently, traffic load beyond a 462 certain utilization level over a Wi-Fi network can introduce 463 frequent collisions and significant network overhead. This, in 464 turn, leads to excessive delay, retransmissions, packet losses and 465 lower effective bandwidth for applications. 467 o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate 468 transmission capabilities by dynamically choosing the most 469 appropriate modulation scheme for a given received singal 470 strength. A different choice of physical-layer rate leads to 471 different application-layer throughput. 473 o Presence of legancy 802.11b networks can significantly slow down 474 the the rest of a modern Wi-Fi Network, since it takes longer to 475 transmit the same packet over a slower link than over a faster 476 link. [Editor's note: maybe include a reference here instead.] 478 o Handover from one Wi-Fi Access Point (AP) to another may lead to 479 packet delay and losses during the process. 481 o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi 482 Multi-Media) to give voice and video streams higher priority over 483 pure data applications (e.g., file transfers). 485 In summary, presence of Wi-Fi access links in different network 486 topologies can exert different impact on the network performance in 487 terms of application-layer effective throughput, packet loss rate, 488 and packet delivery delay. These, in turn, influence the behavior of 489 end-to-end real-time multimedia congestion control. 491 Throughout this draft, unless otherwise mentioned, test cases are 492 described using 802.11n due to its wide availability in real-world 493 networks. Statistics collected from enterprise Wi-Fi networks show 494 that the dominant physical modes are 802.11n and 802.11ac, accounting 495 for 73.6% and 22.5% of enterprise network users, respectively. 497 Typically, a Wi-Fi access network connects to a wired infrastructure. 498 Either the wired or the Wi-Fi segment of the network could be the 499 bottleneck. In the following sections, we describe basic test cases 500 for both scenarios separately. The same set of performance metrics 501 as in [I-D.ietf-rmcat-eval-test]) should be collected for each test 502 case. 504 While all test cases described below can be carried out using 505 simulations, e.g. based on [ns-2] or [ns-3], it is also recommended 506 to perform testbed-based evaluations using Wi-Fi access points and 507 endpoints running up-to-date IEEE 802.11 protocols. [Editor's Note: 508 need to add some more discussions on the pros and cons of simulation- 509 based vs. testbed-based evaluations. Will be good to provide 510 recommended testbed configurations. ] 512 4.1. Bottleneck in Wired Network 514 The test scenarios below are intended to mimic the set up of video 515 conferencing over Wi-Fi connections from the home. Typically, the 516 Wi-Fi home network is not congested and the bottleneck is present 517 over the wired home access link. Although it is expected that test 518 evaluation results from this section are similar to those from test 519 cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), it 520 is worthwhile to run through these tests as sanity checks. 522 4.1.1. Network topology 524 Figure 2 shows topology of the network for Wi-Fi test cases. The 525 test contains multiple mobile nodes (MNs) connected to a common Wi-Fi 526 access point (AP) and their corresponding wired clients on fixed 527 nodes (FNs). Each connection carries either RMCAT or TCP traffic 528 flow. Directions of the flows can be uplink, downlink, or bi- 529 directional. 531 uplink 532 +----------------->+ 533 +------+ +------+ 534 | MN_1 |)))) /=====| FN_1 | 535 +------+ )) // +------+ 536 . )) // . 537 . )) // . 538 . )) // . 539 +------+ +----+ +-----+ +------+ 540 | MN_N | ))))))) | | | |========| FN_N | 541 +------+ | | | | +------+ 542 | AP |=========| FN0 | 543 +----------+ | | | | +----------+ 544 | MN_tcp_1 | )))) | | | |======| MN_tcp_1 | 545 +----------+ +----+ +-----+ +----------+ 546 . )) \\ . 547 . )) \\ . 548 . )) \\ . 549 +----------+ )) \\ +----------+ 550 | MN_tcp_M |))) \=====| MN_tcp_M | 551 +----------+ +----------+ 552 +<-----------------+ 553 downlink 555 Figure 2: Network topology for Wi-Fi test cases 557 4.1.2. Test setup 559 o Test duration: 120s 561 o Wi-Fi network characteristics: 563 * Radio propagation model: Log-distance path loss propagation 564 model [NS3WiFi] 566 * PHY- and MAC-layer configuration: IEEE 802.11n 568 * MCS Index at 11: 16-QAM 1/2, Raw Data Rate@52Mbps 570 o Wired path characteristics: 572 * Path capacity: 1Mbps 574 * One-Way propagation delay: 50ms. 576 * Maximum end-to-end jitter: 30ms 578 * Bottleneck queue type: Drop tail. 580 * Bottleneck queue size: 300ms. 582 * Path loss ratio: 0%. 584 o Application characteristics: 586 * Media Traffic: 588 + Media type: Video 590 + Media direction: See Section 4.1.3 592 + Number of media sources (N): See Section 4.1.3 594 + Media timeline: 596 - Start time: 0s. 598 - End time: 119s. 600 * Competing traffic: 602 + Type of sources: long-lived TCP or CBR over UDP 604 + Traffic direction: See Section 4.1.3 605 + Number of sources (M): See Section 4.1.3 607 + Congestion control: Default TCP congestion control [TBD] or 608 CBR over UDP 610 + Traffic timeline: See Section 4.1.3 612 4.1.3. Typical test scenarios 614 o Single uplink RMCAT flow: N=1 with uplink direction and M=0. 616 o One pair of bi-directional RMCAT flows: N=2 (with one uplink flow 617 and one downlink flow); M=0. 619 o One pair of bi-directional RMCAT flows, one on-off CBR over UDP 620 flow on uplink : N=2 (with one uplink flow and one downlink flow); 621 M=1 (uplink). CBR flow on time at 0s-60s, off time at 60s-119s 623 o One pair of bi-directional RMCAT flows, one off-on CBR over UDP 624 flow on uplink : N=2 (with one uplink flow and one downlink flow); 625 M=1 (uplink). UDP off time: 0s-60s, on time: 60s-119s 627 o One RMCAT flow competing against one long-live TCP flow over 628 uplink: N=1 (uplink) and M = 1(uplink), TCP start time: 0s, end 629 time: 119s. 631 4.1.4. Expected behavior 633 o Single uplink RMCAT flow: the candidate algorithm is expected to 634 detect the path capacity constraint, to converge to bottleneck 635 link capacity and to adapt the flow to avoid unwanted oscillation 636 when the sending bit rate is approaching the bottleneck link 637 capacity. No excessive rate oscillations should be present. 639 o Bi-directional RMCAT flows: It is expected that the candidate 640 algorithm is able to converge to the bottleneck capacity of the 641 wired path on both directions despite presence of measurment noise 642 over the Wi-Fi connection. In the presence of background TCP or 643 CBR over UDP traffic, the rate of RMCAT flows should adapt in a 644 timely manner to changes in the available bottleneck bandwidth. 646 o One RMCAT flow competing with long-live TCP flow over uplink: the 647 candidate algorithm should be able to avoid congestion collapse, 648 and to stablize at a fair share of the bottleneck link capacity. 650 4.2. Bottleneck in Wi-Fi Network 652 These test cases assume that the wired portion along the media path 653 is well-provisioned whereas the bottleneck exists over the Wi-Fi 654 access network. This is to mimic the application scenarios typically 655 encountered by users in an enterprise environment or at a coffee 656 house. 658 4.2.1. Network topology 660 Same as defined in Section 4.1.1 662 4.2.2. Test setup 664 o Test duration: 120s 666 o Wi-Fi network characteristics: 668 * Radio propagation model: Log-distance path loss propagation 669 model [NS3WiFi] 671 * PHY- and MAC-layer configuration: IEEE 802.11n 673 * MCS Index at 11: 16-QAM 1/2, Raw Data Rate at 52Mbps 675 o Wired path characteristics: 677 * Path capacity: 100Mbps 679 * One-Way propagation delay: 50ms. 681 * Maximum end-to-end jitter: 30ms 683 * Bottleneck queue type: Drop tail. 685 * Bottleneck queue size: 300ms. 687 * Path loss ratio: 0%. 689 o Application characteristics: 691 * Media Traffic: 693 + Media type: Video 695 + Media direction: See Section 4.2.3 697 + Number of media sources (N): See Section 4.2.3 698 + Media timeline: 700 - Start time: 0s. 702 - End time: 119s. 704 * Competing traffic: 706 + Type of sources: long-lived TCP or CBR over UDP 708 + Number of sources (M): See Section 4.2.3 710 + Traffic direction: See Section 4.2.3 712 + Congestion control: Default TCP congestion control [TBD] or 713 CBR over UDP 715 + Traffic timeline: See Section 4.2.3 717 4.2.3. Typical test scenarios 719 This section describes a few test scenarios that are deemed as 720 important for understanding the behavior of a RMCAT candidate 721 solution over a Wi-Fi network. 723 o Multiple RMCAT Flows Sharing the Wireless Downlink: N=16 (all 724 downlink); M = 0. This test case is for studying the impact of 725 contention on competing RMCAT flows. For an 802.11n network, 726 given the MCS Index of 11 and the corresponding raw data rate of 727 52Mbps, the total application-layer throughput (assuming 728 reasonable distance, low interference and infrequent contentions 729 caused by competing streams) is around 20Mbps. Consequently, a 730 total of N=16 RMCAT flows are needed to saturate the wireless 731 interface in this experiment. Evaluation of a given candidate 732 solution should focus on whether downlink RMCAT flows can stablize 733 at a fair share of total application-layer throughput. 735 o Multiple RMCAT Flows Sharing the Wireless Uplink: N = 16 (all 736 downlink); M = 0. When multiple clients attempt to transmit video 737 packets uplink over the wireless interface, they introduce more 738 frequent contentions and potential collisions. Per-flow 739 throughput is expected to be lower than that in the previous 740 downlink-only scenario. Evaluation of a given candidate solution 741 should focus on whether uplink flows can stablize at a fair share 742 of application-layer throughput. 744 o Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8 745 downlink); M = 0. The goal of this test is to evaluate 746 performance of the candidate solution in terms of bandwidth 747 fairness between uplink and downlink flow. 749 o Multiple Bi-directional RMCAT Flows with on-off CBR traffic: N = 750 16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this 751 test is to evaluate adaptation behavior of the candidate solution 752 when its available bandwidth changes due to departure of 753 background traffic. The background traffic consists of several 754 (e.g., M=5) CBR flows transported over UDP, which are ON at times 755 t=0-60s and are OFF at times t=61-120s. 757 o Multiple Bi-directional RMCAT Flows with off-on CBR traffic: N = 758 16 (8 uplink and 8 downlink); M = 5(uplink). The goal of this 759 test is to evaluate adaptation behavior of the candidate solution 760 when its available bandwidth changes due to arrival of background 761 traffic. The background traffic consists of several (e.g., M=5) 762 parallel CBR flows transported over UDP, which are OFF at times 763 t=0-60s and are ON at times t=61-120s. 765 o Multiple RMCAT flows in the presence of background TCP traffic. 766 The goal of this test is to evaluate how RMCAT flows compete 767 against TCP over a congested Wi-Fi network for a given candidate 768 solution. TCP start time: 0s, end time: 119s. [Editor's Note: 769 need to add the number of recommended RMCAT and TCP flows] 771 o Varying number of RMCAT flows. The goal of this test is to 772 evaluate how a candidate RMCAT solution responds to varying 773 traffic load/demand over a congested Wi-Fi network. [Editor's 774 Note: need to specify recommended arrival/departure pattern of 775 RMCAT flows] 777 4.2.4. Expected behavior 779 o Multiple downlink RMCAT flows: each RMCAT flow should get its fair 780 share of the total bottleneck link bandwidth. Overall bandwidth 781 usage should not be significantly lower than that experienced by 782 the same number of concurrent downlink TCP flows. In other words, 783 the performance of multiple concurrent TCP flows will be used as a 784 performance benchmark for this test scenario. The end-to-end 785 delay and packet loss ratio experienced by each flow should be 786 within acceptable range for real-time multimedia applications. 788 o Multiple uplink RMCAT flows: overall bandwidth usage shared by all 789 RMCAT flows should not be significantly lower than that 790 experienced by the same number of concurrent uplink TCP flows. In 791 other words, the performance of multiple concurrent TCP flows will 792 be used as a performance benchmark for this test scenario. 794 o Multiple bi-directional RMCAT flows with dynamic background 795 traffic carry CBR flows over UDP: RMCAT flows should adapt in a 796 timely fashion to the resulting changes in available bandwidth. 798 o Multiple bi-directional RMCAT flows with TCP traffic: overall 799 bandwidth usage shared by all RMCAT flows should not be 800 significantly lower than those achieved by the same number of bi- 801 directional TCP flows. In other words, the performance of 802 multiple concurrent TCP flows will be used as a performance 803 benchmark for this test scenario. All downlink RMCAT flows are 804 expected to obtain similar bandwidth with respect to each other. 806 4.3. Potential Potential Test Cases 808 4.3.1. EDCA/WMM usage 810 EDCA/WMM is prioritized QoS with four traffic classes (or Access 811 Categories) with differing priorities. RMCAT flows should achieve 812 better performance (i.e., lower delay, fewer packet losses) with 813 EDCA/WMM enabled when competing against non-interactive background 814 traffic (e.g., file transfers). When most of the traffic over Wi-Fi 815 is dominated by media, however, turning on WMM may actually degrade 816 performance since all media flows now attempt to access the wireless 817 transmission medium more aggressively, thereby causing more frequent 818 collisions and collision-induced losses. This is a topic worthy of 819 further investigation. 821 4.3.2. Legacy 802.11b Effects 823 When there is 802.11b devices connected to modern 802.11 network, it 824 may affect the performance of the whole network. Additional test 825 cases can be added to evaluate the affects of legancy devices on the 826 performance of RMCAT congestion control algorithm. 828 5. Conclusion 830 This document defines a collection of test cases that are considered 831 important for cellular and Wi-Fi networks. Moreover, this document 832 also provides a framework for defining additional test cases over 833 wireless cellular/Wi-Fi networks. 835 6. Acknowledgements 837 We would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer 838 Sandlund for their valuable comments while writing this draft. 840 7. IANA Considerations 842 This memo includes no request to IANA. 844 8. Security Considerations 846 Security issues have not been discussed in this memo. 848 9. References 850 9.1. Normative References 852 [Deployment] 853 TS 25.814, 3GPP., "Physical layer aspects for evolved 854 Universal Terrestrial Radio Access (UTRA)", October 2006, 855 . 858 [HO-def-3GPP] 859 TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications", 860 December 2009, . 863 [HO-LTE-3GPP] 864 TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC); 865 Protocol specification", December 2011, 866 . 869 [HO-UMTS-3GPP] 870 TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol 871 specification", December 2011, 872 . 875 [I-D.ietf-rmcat-eval-criteria] 876 Singh, V., Ott, J., and S. Holmer, "Evaluating Congestion 877 Control for Interactive Real-time Media", draft-ietf- 878 rmcat-eval-criteria-06 (work in progress), September 2016. 880 [NS3WiFi] "Wi-Fi Channel Model in NS3 Simulator", 881 . 884 [QoS-3GPP] 885 TS 23.203, 3GPP., "Policy and charging control 886 architecture", June 2011, . 889 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 890 Requirement Levels", BCP 14, RFC 2119, 891 DOI 10.17487/RFC2119, March 1997, 892 . 894 9.2. Informative References 896 [I-D.ietf-rmcat-cc-requirements] 897 Jesup, R. and Z. Sarker, "Congestion Control Requirements 898 for Interactive Real-Time Media", draft-ietf-rmcat-cc- 899 requirements-09 (work in progress), December 2014. 901 [I-D.ietf-rmcat-eval-test] 902 Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test 903 Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat- 904 eval-test-04 (work in progress), October 2016. 906 [IEEE802.11] 907 "Standard for Information technology--Telecommunications 908 and information exchange between systems Local and 909 metropolitan area networks--Specific requirements Part 11: 910 Wireless LAN Medium Access Control (MAC) and Physical 911 Layer (PHY) Specifications", 2012. 913 [LTE-simulator] 914 "NS-3, A discrete-Event Network Simulator", 915 . 918 [ns-2] "The Network Simulator - ns-2", 919 . 921 [ns-3] "The Network Simulator - ns-3", . 923 Authors' Addresses 925 Zaheduzzaman Sarker 926 Ericsson AB 927 Laboratoriegraend 11 928 Luleae 97753 929 Sweden 931 Phone: +46 107173743 932 Email: zaheduzzaman.sarker@ericsson.com 933 Ingemar Johansson 934 Ericsson AB 935 Laboratoriegraend 11 936 Luleae 97753 937 Sweden 939 Phone: +46 10 7143042 940 Email: ingemar.s.johansson@ericsson.com 942 Xiaoqing Zhu 943 Cisco Systems 944 12515 Research Blvd., Building 4 945 Austin, TX 78759 946 USA 948 Email: xiaoqzhu@cisco.com 950 Jiantao Fu 951 Cisco Systems 952 707 Tasman Drive 953 Milpitas, CA 95035 954 USA 956 Email: jianfu@cisco.com 958 Wei-Tian Tan 959 Cisco Systems 960 725 Alder Drive 961 Milpitas, CA 95035 962 USA 964 Email: dtan2@cisco.com 966 Michael A. Ramalho 967 Cisco Systems 968 8000 Hawkins Road 969 Sarasota, FL 34241 970 USA 972 Phone: +1 919 476 2038 973 Email: mramalho@cisco.com