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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 8, 2016 X. Zhu 6 J. Fu 7 W. Tan 8 M. Ramalho 9 Cisco Systems 10 November 5, 2015 12 Evaluation Test Cases for Interactive Real-Time Media over Wireless 13 Networks 14 draft-ietf-rmcat-wireless-tests-01 16 Abstract 18 It is evident that to ensure seamless and robust user experience 19 across all type of access networks multimedia communication suits 20 should adapt to the changing network conditions. There is an ongoing 21 effort in IETF RMCAT working group to standardize rate adaptive 22 algorithm(s) to be used in the real-time interactive communication. 23 In this document test cases are described to evaluate the 24 performances of the proposed endpoint adaptation solutions in LTE 25 networks and Wi-Fi networks. The proposed algorithms should be 26 evaluated using the test cases defined in this document to select 27 most optimal solutions. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on May 8, 2016. 46 Copyright Notice 48 Copyright (c) 2015 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Cellular Network Specific Test Cases . . . . . . . . . . . . 3 66 3.1. Varying Network Load . . . . . . . . . . . . . . . . . . 6 67 3.1.1. Network Connection . . . . . . . . . . . . . . . . . 6 68 3.1.2. Simulation Setup . . . . . . . . . . . . . . . . . . 7 69 3.2. Bad Radio Coverage . . . . . . . . . . . . . . . . . . . 8 70 3.2.1. Network connection . . . . . . . . . . . . . . . . . 9 71 3.2.2. Simulation Setup . . . . . . . . . . . . . . . . . . 9 72 3.3. Desired Evaluation Metrics for cellular test cases . . . 10 73 4. Wi-Fi Networks Specific Test Cases . . . . . . . . . . . . . 10 74 4.1. Bottleneck in Wired Network . . . . . . . . . . . . . . . 12 75 4.1.1. Network topology . . . . . . . . . . . . . . . . . . 12 76 4.1.2. Test setup . . . . . . . . . . . . . . . . . . . . . 13 77 4.1.3. Typical test scenarios . . . . . . . . . . . . . . . 14 78 4.1.4. Expected behavior . . . . . . . . . . . . . . . . . . 14 79 4.2. Bottleneck in Wi-Fi Network . . . . . . . . . . . . . . . 14 80 4.2.1. Network topology . . . . . . . . . . . . . . . . . . 15 81 4.2.2. Test setup . . . . . . . . . . . . . . . . . . . . . 15 82 4.2.3. Typical test scenarios . . . . . . . . . . . . . . . 16 83 4.2.4. Expected behavior . . . . . . . . . . . . . . . . . . 17 84 4.3. Potential Potential Test Cases . . . . . . . . . . . . . 17 85 4.3.1. EDCA/WMM usage . . . . . . . . . . . . . . . . . . . 17 86 4.3.2. Legacy 802.11b Effects . . . . . . . . . . . . . . . 17 87 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 18 88 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 89 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 90 8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 91 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 92 9.1. Normative References . . . . . . . . . . . . . . . . . . 18 93 9.2. Informative References . . . . . . . . . . . . . . . . . 19 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 97 1. Introduction 99 Wireless networks (both cellular and Wi-Fi [IEEE802.11] local area 100 network) are an integral part of the Internet. Mobile devices 101 connected to the wireless networks produces huge amount of media 102 traffic in the Internet. They covers the scenarios of having a video 103 call in the bus to media consumption sitting on a couch in a living 104 room. It is a well known fact that the characteristic and challenges 105 for offering service over wireless network are very different than 106 providing the same over a wired network. Even though RMCAT basic 107 test cases defines number of test cases that covers lots of effects 108 of the impairments visible in the wireless networks but there are 109 characteristics and dynamics those are unique to particular wireless 110 environment. For example, in the LTE the base station maintains 111 queues per radio bearer per user hence it gives different interaction 112 when all traffic from user share the same queue. Again, the user 113 mobility in a cellular network is different than the user mobility in 114 a Wi-Fi network. Thus, It is important to evaluate the performance 115 of the proposed RMCAT candidates separately in the cellular mobile 116 networks and Wi-Fi local networks (IEEE 802.11xx protocol family ). 118 RMCAT evaluation criteria [I-D.ietf-rmcat-eval-criteria] document 119 provides the guideline to perform the evaluation on candidate 120 algorithms and recognizes wireless networks to be important access 121 link. However, it does not provides particular test cases to 122 evaluate the performance of the candidate algorithm. In this 123 document we describe test cases specifically targeting cellular 124 networks such as LTE networks and Wi-Fi local networks. 126 2. Terminologies 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in RFC2119 [RFC2119] 132 3. Cellular Network Specific Test Cases 134 A cellular environment is more complicated than a wireline ditto 135 since it seeks to provide services in the context of variable 136 available bandwidth, location dependencies and user mobilities at 137 different speeds. In a cellular network the user may reach the cell 138 edge which may lead to a significant amount of retransmissions to 139 deliver the data from the base station to the destination and vice 140 versa. These network links or radio links will often act as a 141 bottleneck for the rest of the network which will eventually lead to 142 excessive delays or packet drops. An efficient retransmission or 143 link adaptation mechanism can reduce the packet loss probability but 144 there will still be some packet losses and delay variations. 145 Moreover, with increased cell load or handover to a congested cell, 146 congestion in transport network will become even worse. Besides, 147 there are certain characteristics which make the cellular network 148 different and challenging than other types of access network such as 149 Wi-Fi and wired network. In a cellular network - 151 o The bottleneck is often a shared link with relatively few users. 153 * The cost per bit over the shared link varies over time and is 154 different for different users. 156 * Left over/ unused resource can be grabbed by other greedy 157 users. 159 o Queues are always per radio bearer hence each user can have many 160 of such queues. 162 o Users can experience both Inter and Intra Radio Access Technology 163 (RAT) handovers ("handover" definition in [HO-def-3GPP] ). 165 o Handover between cells, or change of serving cells (see in 166 [HO-LTE-3GPP] and [HO-UMTS-3GPP] ) might cause user plane 167 interruptions which can lead to bursts of packet losses, delay 168 and/or jitter. The exact behavior depends on the type of radio 169 bearer. Typically, the default best effort bearers do not 170 generate packet loss, instead packets are queued up and 171 transmitted once the handover is completed. 173 o The network part decides how much the user can transmit. 175 o The cellular network has variable link capacity per user 177 * Can vary as fast as a period of milliseconds. 179 * Depends on lots of facts (such as distance, speed, 180 interference, different flows). 182 * Uses complex and smart link adaptation which makes the link 183 behavior ever more dynamic. 185 * The scheduling priority depends on the estimated throughput. 187 o Both Quality of Service (QoS) and non-QoS radio bearers can be 188 used. 190 Hence, a real-time communication application operating in such a 191 cellular network need to cope with shared bottleneck link and 192 variable link capacity, event likes handover, non-congestion related 193 loss, abrupt change in bandwidth (both short term and long term) due 194 to handover, network load and bad radio coverage. Even though 3GPP 195 define QoS bearers [QoS-3GPP] to ensure high quality user experience, 196 adaptive real-time applications are desired. 198 Different mobile operators deploy their own cellular network with 199 their own set of network functionalities and policies. Usually, a 200 mobile operator network includes 2G, EDGE, 3G and 4G radio access 201 technologies. Looking at the specifications of such radio 202 technologies it is evident that only 3G and 4G radio technologies can 203 support the high bandwidth requirements from real-time interactive 204 video applications. The future real-time interactive application 205 will impose even greater demand on cellular network performance which 206 makes 4G (and beyond radio technologies) more suitable access 207 technology for such genre of application. 209 The key factors to define test cases for cellular network are 211 o Shared and varying link capacity 213 o Mobility 215 o Handover 217 However, for cellular network it is very hard to separate such events 218 from one another as these events are heavily related. Hence instead 219 of devising separate test cases for all those important events we 220 have divided the test case in two categories. It should be noted 221 that in the following test cases the goal is to evaluate the 222 performance of candidate algorithms over radio interface of the 223 cellular network. Hence it is assumed that the radio interface is 224 the bottleneck link between the communicating peers and that the core 225 network does not add any extra congestion in the path. Also the 226 combination of multiple access technologies such as one user has LTE 227 connection and another has Wi-Fi connection is kept out of the scope 228 of this document. However, later those additional scenarios can also 229 be added in this list of test cases. While defining the test cases 230 we assumed a typical real-time telephony scenario over cellular 231 networks where one real-time session consists of one voice stream and 232 one video stream. We recommend that an LTE network simulator is used 233 for the test cases defined in this document, for example-NS-3 LTE 234 simulator [LTE-simulator]. 236 3.1. Varying Network Load 238 The goal of this test is to evaluate the performance of the candidate 239 congestion control algorithm under varying network load. The network 240 load variation is created by adding and removing network users a.k.a. 241 User Equipments (UEs) during the simulation. In this test case, each 242 of the user/UE in the media session is an RMCAT compliant endpoint. 243 The arrival of users follows a Poisson distribution, which is 244 proportional to the length of the call, so that the number of users 245 per cell is kept fairly constant during the evaluation period. At 246 the beginning of the simulation there should be enough amount of time 247 to warm-up the network. This is to avoid running the evaluation in 248 an empty network where network nodes are having empty buffers, low 249 interference at the beginning of the simulation. This network 250 initialization period is therefore excluded from the evaluation 251 period. 253 This test case also includes user mobility and competing traffic. 254 The competing traffics includes both same kind of flows (with same 255 adaptation algorithms) and different kind of flows (with different 256 service and congestion control). The investigated congestion control 257 algorithms should show maximum possible network utilization and 258 stability in terms of rate variations, lowest possible end to end 259 frame latency, network latency and Packet Loss Rate (PLR) at 260 different cell load level. 262 3.1.1. Network Connection 264 Each mobile user is connected to a fixed user. The connection 265 between the mobile user and fixed user consists of a LTE radio 266 access, an Evolved Packet Core (EPC) and an Internet connection. The 267 mobile user is connected to the EPC using LTE radio access technology 268 which is further connected to the Internet. The fixed user is 269 connected to the Internet via wired connection with no bottleneck 270 (practically infinite bandwidth). The Internet and wired connection 271 in this setup does not add any network impairments to the test, it 272 only adds 10ms of one-way transport propagation delay. 274 The path from the fixed user to mobile user is defines as "Downlink" 275 and the path from mobile user to the fixed user is defined as 276 "Uplink". We assume that only uplink or downlink is congested for 277 the mobile users. Hence, we recommend that the uplink and downlink 278 simulations are run separately. 280 uplink 281 ++))) +--------------------------> 282 ++-+ ((o)) 283 | | / \ +-------+ +------+ +---+ 284 +--+ / \----+ +-----+ +----+ | 285 / \ +-------+ +------+ +---+ 286 UE BS EPC Internet fixed 287 <--------------------------+ 288 downlink 290 Figure 1: Simulation Topology 292 3.1.2. Simulation Setup 294 The values enclosed within " [ ] " for the following simulation 295 attributes follow the notion set in [I-D.ietf-rmcat-eval-test]. The 296 desired simulation setup as follows- 298 1. Radio environment 300 A. Deployment and propagation model : 3GPP case 1[Deployment] 302 B. Antenna: Multiple-Input and Multiple-Output (MIMO), [2D, 3D] 304 C. Mobility: [3km/h, 30km/h] 306 D. Transmission bandwidth: 10Mhz 308 E. Number of cells: multi cell deployment (3 Cells per Base 309 Station (BS) * 7 BS) = 21 cells 311 F. Cell radius: 166.666 Meters 313 G. Scheduler: Proportional fair with no priority 315 H. Bearer: Default bearer for all traffic. 317 I. Active Queue Management (AQM) settings: AQM [on,off] 319 2. End to end Round Trip Time (RTT): [ 40, 150] 321 3. User arrival model: Poisson arrival model 323 4. User intensity: 325 * Downlink user intensity: {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 326 5.6, 6.3, 7.0, 7.7, 8.4, 9,1, 9.8, 10.5} 328 * Uplink user intercity : {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 329 5.6, 6.3, 7.0} 331 5. Simulation duration: 91s 333 6. Evaluation period : 30s-60s 335 7. Media traffic 337 1. Media type: Video 339 a. Media direction: [Uplink, Downlink] 341 b. Number of Media source per user: One (1) 343 c. Media duration per user: 30s 345 d. Media source: same as define in section 4.3 of 346 [I-D.ietf-rmcat-eval-test] 348 2. Media Type : Audio 350 a. Media direction: Uplink and Downlink 352 b. Number of Media source per user: One (1) 354 c. Media duration per user: 30s 356 d. Media codec: Constant BitRate (CBR) 358 e. Media bitrate : 20 Kbps 360 f. Adaptation: off 362 8. Other traffic model: 364 * Downlink simulation: Maximum of 4Mbps/cell (web browsing or 365 FTP traffic) 367 * Unlink simulation: Maximum of 2Mbps/cell (web browsing or FTP 368 traffic) 370 3.2. Bad Radio Coverage 372 The goal of this test is to evaluate the performance of candidate 373 congestion control algorithm when users visit part of the network 374 with bad radio coverage. The scenario is created by using larger 375 cell radius than previous test case. In this test case each of the 376 user/UE in the media session is an RMCAT compliant endpoint. The 377 arrival of users follows a Poisson distribution, which is 378 proportional to the length of the call, so that the number of users 379 per cell is kept fairly constant during the evaluation period. At 380 the beginning of the simulation there should be enough amount of time 381 to warm-up the network. This is to avoid running the evaluation in 382 an empty network where network nodes are having empty buffers, low 383 interference at the beginning of the simulation. This network 384 initialization period is therefore excluded from the evaluation 385 period. 387 This test case also includes user mobility and competing traffic. 388 The competing traffics includes same kind of flows (with same 389 adaptation algorithms) . The investigated congestion control 390 algorithms should show maximum possible network utilization and 391 stability in terms of rate variations, lowest possible end to end 392 frame latency, network latency and Packet Loss Rate (PLR) at 393 different cell load level. 395 3.2.1. Network connection 397 Same as defined in Section 3.1.1 399 3.2.2. Simulation Setup 401 The desired simulation setup is same as Varying Network Load test 402 case defined in Section 3.1 except following changes- 404 1. Radio environment : Same as defined in Section 3.1.2 except 405 followings 407 A. Deployment and propagation model : 3GPP case 3[Deployment] 409 B. Cell radius: 577.3333 Meters 411 C. Mobility: 3km/h 413 2. User intensity = {0.7, 1.4, 2.1, 2.8, 3.5, 4.2, 4.9, 5.6, 6.3, 414 7.0} 416 3. Media traffic model: Same as defined in Section 3.1.2 418 4. Other traffic model: None 420 3.3. Desired Evaluation Metrics for cellular test cases 422 RMCAT evaluation criteria document [I-D.ietf-rmcat-eval-criteria] 423 defines metrics to be used to evaluate candidate algorithms. 424 However, looking at the nature and distinction of cellular networks 425 we recommend at minimum following metrics to be used to evaluate the 426 performance of the candidate algorithms for the test cases defined in 427 this document. 429 The desired metrics are- 431 o Average cell throughput (for all cells), shows cell utilizations. 433 o Application sending and receiving bitrate, goodput. 435 o Packet Loss Rate (PLR). 437 o End to end Media frame delay. For video, this means the delay 438 from capture to display. 440 o Transport delay. 442 o Algorithm stability in terms of rate variation. 444 4. Wi-Fi Networks Specific Test Cases 446 Given the prevalence of Internet access links over Wi-Fi, it is 447 important to evaluate candidate RMCAT congestion control solutions 448 over Wi-Fi test cases. Such evaluations should also highlight the 449 inherent different characteristics of Wi-Fi networks in contrast to 450 Wired networks: 452 o The wireless radio channel is subject to interference from nearby 453 transmitters, multi-path fading, and shadowing, causing 454 fluctuations in link throughput and sometimes an error-prone 455 communication environment 457 o Available network bandwidth is not only shared over the air 458 between concurrent users, but also between uplink and downlink 459 traffic due to the half duplex nature of wireless transmission 460 medium. 462 o Packet transmissions over Wi-Fi are susceptible to contentions and 463 collisions over the air. Consequently, traffic load beyond a 464 certain utilization level over a Wi-Fi network can introduce 465 frequent collisions and significant network overhead. This, in 466 turn, leads to excessive delay, retransmission, loss and lower 467 effective bandwidth for applications. 469 o The IEEE 802.11 standard (i.e., Wi-Fi) supports multi-rate 470 transmission capabilities by dynamically choosing the most 471 appropriate modulation scheme for a given received signal 472 strength. A different choice of Physical-layer rate will lead to 473 different application-layer throughput. 475 o Presence of legacy 802.11b networks can significantly slow down 476 the rest of a modern Wi-Fi Network, since it takes longer to 477 transmit the same packet over a slower link than over a faster 478 link. [Editor's note: maybe include a reference here instead.] 480 o Handover from one Wi-Fi Access Point (AP) to another may cause 481 packet delay and loss. 483 o IEEE 802.11e defined EDCA/WMM (Enhanced DCF Channel Access/Wi-Fi 484 Multi-Media) to give voice and video streams higher priority over 485 pure data applications (e.g., file transfers). 487 As we can see here, presence of Wi-Fi network in different network 488 topologies and traffic arrival can exert different impact on the 489 network performance in terms of video transport rate, packet loss and 490 delay that, in turn, effect end-to-end real-time multimedia 491 congestion control. 493 Throughout this draft, unless otherwise mentioned, test cases are 494 described using 802.11g due to its wide availability in network 495 simulation platform. In practice, however, statistics collected from 496 enterprise networks show that the dominant physical modes are 802.11n 497 and 802.11ac, accounting for 73.6% and 22.5% of enterprise network 498 users, respectively. Whenever possible, it is recommended to extend 499 some of the experiments to 802.11n and 802.11ac, so as to reflect a 500 more modern Wi-Fi network setting. 502 Since Wi-Fi network normally connects to a wired infrastructure, 503 either the wired network or the Wi-Fi network could be the 504 bottleneck. In the following section, we describe basic test cases 505 for both scenarios separately. The same set of performance metrics 506 as in [I-D.ietf-rmcat-eval-test]) should be collected for each test 507 case. 509 While all test cases described below can be carried out using 510 simulations, e.g. based on [ns-2] or [ns-3], it is also recommended 511 to perform testbed-based evaluations using Wi-Fi access points and 512 endpoints running up-to-date IEEE 802.11 protocols. [Editor's Note: 513 need to add some more discussions on the pros and cons of simulation- 514 based vs. testbed-based evaluations. It will be good to provide 515 recommended testbed configurations. ] 517 4.1. Bottleneck in Wired Network 519 The test scenarios below are intended to mimic the set up of video 520 conferencing over Wi-Fi connections from the home. Typically, the 521 Wi-Fi home network is not congested and the bottleneck is present 522 over the wired home access link. Although it is expected that test 523 evaluation results from this section are similar to those from test 524 cases defined for wired networks (see [I-D.ietf-rmcat-eval-test]), it 525 is worthwhile to run through these tests as sanity checks. 527 4.1.1. Network topology 529 Figure 2 shows topology of the network for Wi-Fi test cases. The 530 test contains multiple mobile nodes (MNs) connected to a common Wi-Fi 531 access point (AP) and their corresponding wired clients on fixed 532 nodes (FNs). Each connection carries either RMCAT or TCP traffic 533 flow. Directions of the flows can be uplink, downlink, or bi- 534 directional. 536 uplink 537 +----------------->+ 538 +------+ +------+ 539 | MN_1 |)))) /=====| FN_1 | 540 +------+ )) // +------+ 541 . )) // . 542 . )) // . 543 . )) // . 544 +------+ +----+ +-----+ +------+ 545 | MN_N | ))))))) | | | |========| FN_N | 546 +------+ | | | | +------+ 547 | AP |=========| FN0 | 548 +----------+ | | | | +----------+ 549 | MN_tcp_1 | )))) | | | |======| MN_tcp_1 | 550 +----------+ +----+ +-----+ +----------+ 551 . )) \\ . 552 . )) \\ . 553 . )) \\ . 554 +----------+ )) \\ +----------+ 555 | MN_tcp_M |))) \=====| MN_tcp_M | 556 +----------+ +----------+ 557 +<-----------------+ 558 downlink 560 Figure 2: Network topology for Wi-Fi test cases 562 4.1.2. Test setup 564 o Test duration: 120s 566 o Wi-Fi network characteristics: 568 * Radio propagation model: Log-distance path loss propagation 569 model [NS3WiFi] 571 * PHY- and MAC-layer configuration: IEEE 802.11g 573 * PHY-layer link rate: 54 Mbps 575 o Wired path characteristics: 577 * Path capacity: 1Mbps 579 * One-Way propagation delay: 50ms. 581 * Maximum end-to-end jitter: 30ms 583 * Bottleneck queue type: Drop tail. 585 * Bottleneck queue size: 300ms. 587 * Path loss ratio: 0%. 589 o Application characteristics: 591 * Media Traffic: 593 + Media type: Video 595 + Media direction: See Section 4.1.3 597 + Number of media sources (N): See Section 4.1.3 599 + Media timeline: 601 - Start time: 0s. 603 - End time: 119s. 605 * Competing traffic: 607 + Type of sources: long-lived TCP 609 + Traffic direction: See Section 4.1.3 610 + Number of sources (M): See Section 4.1.3 612 + Congestion control: Default TCP congestion control [TBD] 614 + Traffic timeline: 616 - Start time: 0s 618 - End time: 119s 620 4.1.3. Typical test scenarios 622 o Single uplink RMCAT flow: N=1 with uplink direction and M=0. 624 o One pair of bi-directional RMCAT flows: N=2 (with one uplink flow 625 and one downlink flow); M=0. 627 o One RMCAT flow competing against one long-live TCP flow over 628 uplink: N=1 (uplink) and M = 1(uplink). 630 4.1.4. Expected behavior 632 o Single uplink RMCAT flow: the candidate algorithm is expected to 633 detect the path capacity constraint, converges to bottleneck 634 link's capacity and adapt the flow to avoid unwanted oscillation 635 when the sending bit rate is approaching the bottleneck link's 636 capacity. No excessive rate oscillations. 638 o Bi-directional RMCAT flows: It is expected that the candidate 639 algorithms is able to converge to the bottleneck capacity of the 640 wired path on both directions despite of the presence of 641 measurement noise over the Wi-Fi connection. 643 o One RMCAT flow competing with long-live TCP flow over uplink: the 644 candidate algorithm should be able to avoid congestion collapse, 645 and stabilize at a fair share of the bottleneck capacity over the 646 wired path. 648 4.2. Bottleneck in Wi-Fi Network 650 These test cases assume that the wired portion along the media path 651 are well-provisioned. The bottleneck is in the Wi-Fi network over 652 wireless. This is to mimic the enterprise/coffee-house scenarios. 654 4.2.1. Network topology 656 Same as defined in Section 4.1.1 658 4.2.2. Test setup 660 o Test duration: 120s 662 o Wi-Fi network characteristics: 664 * Radio propagation model: Log-distance path loss propagation 665 model [NS3WiFi] 667 * PHY- and MAC-layer configuration: IEEE 802.11g 669 * PHY-layer link rate: 54 Mbps 671 o Wired path characteristics: 673 * Path capacity: 100Mbps 675 * One-Way propagation delay: 50ms. 677 * Maximum end-to-end jitter: 30ms 679 * Bottleneck queue type: Drop tail. 681 * Bottleneck queue size: 300ms. 683 * Path loss ratio: 0%. 685 o Application characteristics: 687 * Media Traffic: 689 + Media type: Video 691 + Media direction: See Section 4.2.3 693 + Number of media sources (N): See Section 4.2.3 695 + Media timeline: 697 - Start time: 0s. 699 - End time: 119s. 701 * Competing traffic: 703 + Type of sources: long-lived TCP 705 + Number of sources (M): See Section 4.2.3 707 + Traffic direction: See Section 4.2.3 709 + Congestion control: Default TCP congestion control [TBD] 711 + Traffic timeline: 713 - Start time: 0s 715 - End time: 119s 717 4.2.3. Typical test scenarios 719 This sections describes a few specific test scenarios that are deemed 720 as important for understanding behavior of a RMCAT candidate solution 721 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. Specifications for IEEE 726 802.11g with a physical-layer transmission rate of 54 Mbps is 727 chosen. Note that retransmission and MAC-layer headers and 728 control packets may be sent at a lower link speed. The total 729 application-layer throughput (reasonable distance, low 730 interference and small number of contention stations) for 802.11g 731 is around 20 Mbps. Consequently, a total of N=16 RMCAT flows are 732 needed for saturating the wireless interface in this experiment. 733 Evaluation of a given candidate solution should focus on whether 734 downlink RMCAT flows can stabilize at a fair share of bandwidth. 736 o Multiple RMCAT Flows Sharing the Wireless Uplink: N = 16 (all 737 downlink); M = 0; When multiple clients attempt to transmit video 738 packets uplink over the wireless interface, they introduce more 739 frequent contentions and potentially collisions. Per-flow 740 throughput is expected to be lower than that in the previous 741 downlink-only scenario. Evaluation of a given candidate solution 742 should focus on whether uplink flows can stabilize at a fair share 743 of bandwidth. 745 o Multiple Bi-directional RMCAT Flows: N = 16 (8 uplink and 8 746 downlink); M = 0. The goal of this test is to evaluate 747 performance of the candidate solution in terms of bandwidth 748 fairness between uplink and downlink flow. 750 o Multiple RMCAT flows in the presence of background TCP traffic: 751 the goal of this test is to evaluate how RMCAT flows compete 752 against TCP over a congested Wi-Fi network for a given candidate 753 solution. [Editor's Note: more detailed description will be added 754 in the next version in terms of directoin/number of RMCAT and TCP 755 flows. ] 757 o Varying number of RMCAT flows: the goal of this test is to 758 evaluate how a candidate RMCAT solution responds to varying 759 traffic load/demand over a congested Wi-Fi network. [Editor's 760 Note: more detailed description will be added in the next version 761 in terms of arrival/departure pattern of the flows.] 763 4.2.4. Expected behavior 765 o Multiple downlink RMCAT flows: All RMCAT flows should get fair 766 share of the bandwidth. Overall bandwidth usage should be no less 767 than same case with TCP flows (using TCP as performance 768 benchmark). The delay and loss should be within acceptable range 769 for real-time multimedia flow. 771 o Multiple uplink RMCAT flows: overall bandwidth usage shared by all 772 RMCAT flows should be no less than those shared by the same number 773 of TCP flows (i.e., benchmark performance using TCP flows). 775 o Multiple bi-directional RMCAT flows: overall bandwidth usage 776 shared by all RMCAT flows should be no less than those shared by 777 the same number of TCP flows (i.e., benchmark performance using 778 TCP flows). All downlink RMCAT flows are expected to obtain 779 similar bandwidth with respect to each other. 781 4.3. Potential Potential Test Cases 783 4.3.1. EDCA/WMM usage 785 EDCA/WMM is prioritized QoS with four traffic classes (or Access 786 Categories) with differing priorities. RMCAT flow should have better 787 performance (lower delay, less loss) with EDCA/WMM enabled when 788 competing against non-interactive background traffic (e.g., file 789 transfers). When most of the traffic over Wi-Fi is dominated by 790 media, however, turning on WMM may actually degrade performance. 791 This is a topic worthy of further investigation. 793 4.3.2. Legacy 802.11b Effects 795 When there is 802.11b devices connected to modern 802.11 network, it 796 may affect the performance of the whole network. Additional test 797 cases can be added to evaluate the affects of legacy devices on the 798 performance of RMCAT congestion control algorithm. 800 5. Conclusion 802 This document defines a collection of test cases that are considered 803 important for cellular and Wi-Fi networks. Moreover, this document 804 also provides a framework for defining additional test cases over 805 wireless cellular/Wi-Fi networks. 807 6. Acknowledgements 809 We would like to thank Tomas Frankkila, Magnus Westerlund, Kristofer 810 Sandlund for their valuable comments while writing this draft. 812 7. IANA Considerations 814 This memo includes no request to IANA. 816 8. Security Considerations 818 Security issues have not been discussed in this memo. 820 9. References 822 9.1. Normative References 824 [Deployment] 825 TS 25.814, 3GPP., "Physical layer aspects for evolved 826 Universal Terrestrial Radio Access (UTRA)", October 2006, 827 . 830 [HO-def-3GPP] 831 TR 21.905, 3GPP., "Vocabulary for 3GPP Specifications", 832 December 2009, . 835 [HO-LTE-3GPP] 836 TS 36.331, 3GPP., "E-UTRA- Radio Resource Control (RRC); 837 Protocol specification", December 2011, 838 . 841 [HO-UMTS-3GPP] 842 TS 25.331, 3GPP., "Radio Resource Control (RRC); Protocol 843 specification", December 2011, 844 . 847 [I-D.ietf-rmcat-eval-criteria] 848 Singh, V. and J. Ott, "Evaluating Congestion Control for 849 Interactive Real-time Media", draft-ietf-rmcat-eval- 850 criteria-04 (work in progress), October 2015. 852 [NS3WiFi] "Wi-Fi Channel Model in NS3 Simulator", 853 . 856 [QoS-3GPP] 857 TS 23.203, 3GPP., "Policy and charging control 858 architecture", June 2011, . 861 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 862 Requirement Levels", BCP 14, RFC 2119, 863 DOI 10.17487/RFC2119, March 1997, 864 . 866 9.2. Informative References 868 [I-D.ietf-rmcat-cc-requirements] 869 Jesup, R. and Z. Sarker, "Congestion Control Requirements 870 for Interactive Real-Time Media", draft-ietf-rmcat-cc- 871 requirements-09 (work in progress), December 2014. 873 [I-D.ietf-rmcat-eval-test] 874 Sarker, Z., Singh, V., Zhu, X., and M. Ramalho, "Test 875 Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat- 876 eval-test-02 (work in progress), September 2015. 878 [IEEE802.11] 879 "Standard for Information technology--Telecommunications 880 and information exchange between systems Local and 881 metropolitan area networks--Specific requirements Part 11: 882 Wireless LAN Medium Access Control (MAC) and Physical 883 Layer (PHY) Specifications", 2012. 885 [LTE-simulator] 886 "NS-3, A discrete-Event Network Simulator", 887 . 890 [ns-2] "The Network Simulator - ns-2", 891 . 893 [ns-3] "The Network Simulator - ns-3", . 895 Authors' Addresses 897 Zaheduzzaman Sarker 898 Ericsson AB 899 Laboratoriegraend 11 900 Luleae 97753 901 Sweden 903 Phone: +46 107173743 904 Email: zaheduzzaman.sarker@ericsson.com 906 Ingemar Johansson 907 Ericsson AB 908 Laboratoriegraend 11 909 Luleae 97753 910 Sweden 912 Phone: +46 10 7143042 913 Email: ingemar.s.johansson@ericsson.com 915 Xiaoqing Zhu 916 Cisco Systems 917 12515 Research Blvd., Building 4 918 Austin, TX 78759 919 USA 921 Email: xiaoqzhu@cisco.com 923 Jiantao Fu 924 Cisco Systems 925 707 Tasman Drive 926 Milpitas, CA 95035 927 USA 929 Email: jianfu@cisco.com 930 Wei-Tian Tan 931 Cisco Systems 932 725 Alder Drive 933 Milpitas, CA 95035 934 USA 936 Email: dtan2@cisco.com 938 Michael A. Ramalho 939 Cisco Systems 940 8000 Hawkins Road 941 Sarasota, FL 34241 942 USA 944 Phone: +1 919 476 2038 945 Email: mramalho@cisco.com