A Demonstration of a new TCP Congestion Control Algorithm...
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A Demonstration of a new TCP Congestion Control Algorithm over LTE and other Challenging Networks Jingyuan Wang, Jiangtao Wen, Jun Zhang, Yuxing Han Department of Computer Science and Technology Tsinghua University, Beijing, China [email protected], [email protected], [email protected] and [email protected] ABSTRACT TCP is the most widely used protocol for Internet traffic, including email, web browsing, data and an increasing por- tion of multimedia content delivered in real time using the HTTP/TCP protocols. Performances of existing TCP con- gestion control algorithms degrade significantly when de- ployed over wireless networks. As TCP was designed pri- marily for reliable, as opposed to real time delivery, the prob- lem is particularly severe for real time applications such as HTTP/TCP based streaming. In the proposed demo, we will demonstrate the performance of a new TCP congestion con- trol algorithm in different network conditions. Theoretical analysis and experiments both show that the new TCP con- gestion control algorithm, namely, TCP-FIT, out-performs existing algorithms such as Bic/Cubic, Reno, Veno, West- wood, Compound TCP, FastTCP and etc. under challenging network conditions, while maintaining good inter and intra protocol fairness. The proposed demo will be carried out using generic network emulation hardware such as the Link- tropy Mini, as well as the carrier grade Neatbox software emulator for LTE networks from Nomor Research. Mobi- com participants will also be able to conduct back to back or side by side comparisons of the TCP-FIT and other state of the art TCP algorithms using live wired line as well as 3G or Wi-Fi networks. A video showing one of many com- parisons available to Mobicom participants can be found at http://media.cs.tsinghua.edu.cn/∼multimedia/tcp-fit/. 1. INTRODUCTION The TCP protocol is the most widely used protocol for In- ternet traffic including email, data, web browsing. Although TCP was not originally designed for real time applications such as live streaming of multimedia content, various studies show that up to 80% of existing Internet multimedia services are HTTP/TCP based [6]. Congestion control algorithm is an integral component of TCP that directly determines the performance of the pro- tocol. Based on the inputs used by the congestion control algorithms, TCP congestion control algorithms can be cate- gorized into delay based algorithms, packet loss based algo- rithms and hybrid algorithms. Numerous congestion algo- rithms have been proposed for TCP and the performances of such algorithms have improved tremendously over the last two decades. On the other hand however, the wireless network access as well as the average access speed have grown even more rapidly. Mobile users are routinely accessing wireless net- works with ever more demanding applications and ever in- creasing mobility, leaving the improvement in TCP perfor- mance in pale in comparison with the demand. Improving TCP performance for large bandwidth and delay variation, high packet loss rate wireless networks and intermittent con- nectivity remains a challenge. 2. TCP-FIT We are developing a TCP congestion control algorithm, named TCP-FIT, targeting applications in challenging net- work conditions. Instead of designing a single congestion control mechanism for large ranges of bandwidths, delay, packet loss rate and other network characteristics, TCP-FIT employs an “arsenal” of tools designed for applications in different scenarios, and is a hybrid congestion control algo- rithm that uses both delay and packet loss as inputs. A typical congestion control mechanism in TCP-FIT can be understood as the combination of N parallel virtual ses- sions. These sessions are virtual in the sense that only one physical connection (with associated queue and state ma- chine) is established for each TCP connection. From both the receiver and the application layer perspectives, a TCP- FIT connection is just like another other standard TCP con- nection. The congestion window of TCP-FIT is N times that of each of the virtual sessions, which is controlled using pri- marily packet loss information in a manner similar to state- of-the-art congestion control algorithms such as Reno. The mechanism with which the virtual session congestion win- dow is controlled is selected based on the overall network conditions (e.g. high BDP, high PLR, high bandwidth vari- ations, and combinations thereof). Once the value for the congestion window is found, it is multiplied by the number 1
Transcript of A Demonstration of a new TCP Congestion Control Algorithm...
A Demonstration of a new TCP Congestion ControlAlgorithm over LTE and other Challenging Networks
Jingyuan Wang, Jiangtao Wen, Jun Zhang, Yuxing HanDepartment of Computer Science and Technology
Tsinghua University, Beijing, [email protected], [email protected],[email protected] and [email protected]
ABSTRACTTCP is the most widely used protocol for Internet traffic,including email, web browsing, data and an increasing por-tion of multimedia content delivered in real time using theHTTP/TCP protocols. Performances of existing TCP con-gestion control algorithms degrade significantly when de-ployed over wireless networks. As TCP was designed pri-marily for reliable, as opposed to real time delivery, the prob-lem is particularly severe for real time applications such asHTTP/TCP based streaming. In the proposed demo, we willdemonstrate the performance of a new TCP congestion con-trol algorithm in different network conditions. Theoreticalanalysis and experiments both show that the new TCP con-gestion control algorithm, namely, TCP-FIT, out-performsexisting algorithms such as Bic/Cubic, Reno, Veno, West-wood, Compound TCP, FastTCP and etc. under challengingnetwork conditions, while maintaining good inter and intraprotocol fairness. The proposed demo will be carried outusing generic network emulation hardware such as the Link-tropy Mini, as well as the carrier grade Neatbox softwareemulator for LTE networks from Nomor Research. Mobi-com participants will also be able to conduct back to backor side by side comparisons of the TCP-FIT and other stateof the art TCP algorithms using live wired line as well as3G or Wi-Fi networks. A video showing one of many com-parisons available to Mobicom participants can be found athttp://media.cs.tsinghua.edu.cn/∼multimedia/tcp-fit/.
1. INTRODUCTIONThe TCP protocol is the most widely used protocol for In-
ternet traffic including email, data, web browsing. AlthoughTCP was not originally designed for real time applicationssuch as live streaming of multimedia content, various studiesshow that up to 80% of existing Internet multimedia servicesare HTTP/TCP based [6].
Congestion control algorithm is an integral component ofTCP that directly determines the performance of the pro-tocol. Based on the inputs used by the congestion controlalgorithms, TCP congestion control algorithms can be cate-gorized into delay based algorithms, packet loss based algo-
rithms and hybrid algorithms. Numerous congestion algo-rithms have been proposed for TCP and the performances ofsuch algorithms have improved tremendously over the lasttwo decades.
On the other hand however, the wireless network accessas well as the average access speed have grown even morerapidly. Mobile users are routinely accessing wireless net-works with ever more demanding applications and ever in-creasing mobility, leaving the improvement in TCP perfor-mance in pale in comparison with the demand. ImprovingTCP performance for large bandwidth and delay variation,high packet loss rate wireless networks and intermittent con-nectivity remains a challenge.
2. TCP-FITWe are developing a TCP congestion control algorithm,
named TCP-FIT, targeting applications in challenging net-work conditions. Instead of designing a single congestioncontrol mechanism for large ranges of bandwidths, delay,packet loss rate and other network characteristics, TCP-FITemploys an “arsenal” of tools designed for applications indifferent scenarios, and is a hybrid congestion control algo-rithm that uses both delay and packet loss as inputs.
A typical congestion control mechanism in TCP-FIT canbe understood as the combination of N parallel virtual ses-sions. These sessions are virtual in the sense that only onephysical connection (with associated queue and state ma-chine) is established for each TCP connection. From boththe receiver and the application layer perspectives, a TCP-FIT connection is just like another other standard TCP con-nection.
The congestion window of TCP-FIT is N times that ofeach of the virtual sessions, which is controlled using pri-marily packet loss information in a manner similar to state-of-the-art congestion control algorithms such as Reno. Themechanism with which the virtual session congestion win-dow is controlled is selected based on the overall networkconditions (e.g. high BDP, high PLR, high bandwidth vari-ations, and combinations thereof). Once the value for thecongestion window is found, it is multiplied by the number
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Figure 1: Average throughput for 3 hours of differentTCP algorithms over LTE wireless networks.
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Figure 2: Throughput comparison between differentTCP variants for varied SINR.
N to find the congestion window for TCP-FIT. The numberN is dynamically controlled primarily using delay informa-tion. We also introduce modules in TCP-FIT to better esti-mate the RTT and other key characteristics of the network,for proper adaptation of the virtual session congestion con-trol algorithm, as well as N.
In our research, we have tested the performance of TCP-FIT under various network conditions. The performancewas measured in average throughput, intra and inter protocolfairness, average performance convergence time, as well asapplication layer latency. The experiments were conductedboth on the Linktropy Mini network simulator, the carriergrade real time Nomor Neatbox wireless (LTE, Wi-Max andHSPA) emulator [4], as well as “live” Wi-Fi, ADSL, andChina Mobile 3G TD-SCDMA access cards. The server andclient machines were located in China as well as Europe andthe US. The improvements provided by TCP-FIT were verysignificant and consistent over a long period of time and ge-ographically diverse locations. The results were also con-sistent with analytical analysis of the protocol, including itssteady state performance and fairness.
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Figure 3: Network topology of one LTE demonstrationusing the Nomor Neatbox
A snapshot of the large body of experimental results canbe found in figures 1 and 2 which were obtained using theNeatbox LTE emulator. The average throughput of TCPvariants during a 3-hour period is shown in Fig. 1. Fig.2 shows the throughputs of the various TCP congestion al-gorithms over the LTE network as a function of the SINR.Among the TCP algorithms tested, Reno, CUBIC [1] andCompound TCP (CTCP) [5] are widely used as the conges-tion control algorithms for the Linux and Microsoft Win-dows operating systems. Westwood[3] is a congestion con-trol algorithm optimized for wireless. As can be seen inthe figures, in this particular set of experiments, TCP-FITachieved more than double throughput performance of otheralgorithms.
3. DEMONSTRATIONS
3.1 Demo Equipments and SoftwareOur demonstration equipments include a Nomor Neatbox
[4], a Linktropy Mini network emulator [2], Linux basedservers and PC or Mobile terminals that work as the clients.
Among the equipments, the Nomor Neatbox is a PC basedwireless network emulator which provides realistic and realtime emulation of wireless networks such as LTE. As pointedout in [4], it is capable of fully emulating the network con-figuration, the mobile channel and the physical layer in amulti-cell, multi-user environment that models all effects onuser as experienced in a real system in a repeatable manner.It is widely used by wireless carriers and equipment manu-facturers. As shown in Fig. 3, there are two Ethernet inter-faces in the Neatbox. The Network interface is connected toservers and the User Equipments (UE) interface connects toclients. Between these two interfaces is the emulated wire-less (e.g. LTE) network. An emulation scenario includesone LTE base station (eNB) and several wireless Live-UEsand/or Non-Live-UEs. IP traffics onto eNB are mapped toservers connected to the Network Interface and onto Live-UEs are mapped to clients connected to the UE interface.Non-Live-UEs are used to generate background traffics us-ing Neatbox’s built-in traffic models. The network layout,
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Table 1: LTE Emulator Parameters SettingParameter ValueTx Power 46dBm (eNB), 24dBm (UE)Bandwidth 10MHz
Penetration Loss 20dBPathloss 128.1dB+37.6dB*log10(d/km)
DL Antenna Config 1x2(Rx diversity a UE)Channel Model Typical Urban 3km/h
Shadowing 2D uncorrelated gridScheduler Proportional Fair
number of users, UE capabilities, underlying traffic models,physical layer and MAC layer network parameters etc. areconfigurable via a GUI.
3.2 Demonstration SetupsIn our demonstrations, TCP-FIT will be compared with
other TCP algorithm including, CUBIC, CTCP and TCPWestwood. A typical configuration used for a demo is asshown in Table I for an LTE demo. It contains one LTE basestation (eNB) and 10 LTE UEs in a cell of a 600-m radius.The eNB is connected to two Linux TCP servers, one run-ning TCP-FIT and the other a different algorithm compari-son. Two TCP clients are connected to two Live UEs andthe other 8 Non-live UEs provide background traffic in thedemonstration generated by a Neatbox built-in 3GPP videosimulation model.
A typical demonstration will be shown in three steps: First,we will run one Live-UE in the emulator, and use traditionalTCP algorithms, to deliver a movie clip from sever to theclient. Then, we will use the same HTTP server softwareto stream video but with TCP-FIT. Finally, we will start twoLive-UEs in the LTE emulator at the same time, and streamvideos from two HTTP severs using TCP-FIT and traditionalTCP respectively so as to subjective video qualities betweenthese Live-UEs side by side. Screen captures of the demowith more detailed description of the set up can be found athttp://media.cs.tsinghua.edu.cn/∼multimedia/tcp-fit/lte/.
For each demo, multiple content clips encoded at differ-ent resolutions and bitrates will be made available througha playlist on the server. No client software installation isrequired.
In addition to scheduled demos such as the one describedabove, we will also made servers using TCP-FIT and TCPCubic available to Mobicom participants throughout the con-ference so that attendants will be able to test the perfor-mances of the servers at their own pace.
For controlled experiments, we will also be able to con-figure the Neatbox software and Linktropy Mini emulatoraccording to the requirements of the Mobicom attendants.
4. SUMMARYHere is a summary of key information related to the pro-
posed demo:
Figure 4: Setup of demonstration
• Name of the demoer: Jingyuan Wang
• Affiliation: Ph.D. candidate at Tsinghua University,Beijing, China
• Equipment used for the demo: As shown in Figure4. 2 desktop PCs, 2 laptop computers, 1 Neatbox, 2switches, 2 Linktropy Minis. Laptops, Neatbox, Link-tropy Mini and switches will be provided by the de-moer. It is preferred that the conference provides atleast 1 Linux PC, although this is not required.
• Spaces needed: 85 sqft (min), 100 sqft (preferred)
• URL for more info:http://media.cs.tsinghua.edu.cn/∼multimedia/tcp-fit/
• The demo is eligible for student demo compeition.
5. REFERENCES[1] S. Ha, I. Rhee, and L. Xu. Cubic: a new tcp-friendly
high-speed tcp variant. SIGOPS Oper. Syst. Rev.,42(5):64–74, February 2008.
[2] Linktropy. Linktropy WAN Emulators.http://www.apposite-tech.com/.
[3] S. Mascolo, C. Casetti, M. Gerla, M. Y. Sanadidi, andR. Wang. Tcp westwood: Bandwidth estimation forenhanced transport over wireless links. In Proc.MobiCom, pages 287–297, July 2001.
[4] Nomor. neatboxTM - Network Emulator for ApplicationTesting. http://www.nomor.de/home/solutions-and-products/products/application-tester.
[5] K. Tan, J. Song, Q. Zhang, and M. Sridharan. Acompound tcp approach for high-speed and longdistance networks. In Proc. IEEE INFOCOM, APRIL2006.
[6] B. Wang, J. Kurose, P. Shenoy, and D. Towsley.Multimedia streaming via TCP: An analyticperformance study. ACM Transactions on MultimediaComputing, Communications, and Applications(TOMCCAP), 4(2):1–22, 2008.
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