Slide 1 of 23 Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP Master Thesis Project (Sep 03 – April 04) Dennis Dungs Technical.

of 23 Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP Master Thesis Project (Sep 03 – April 04) Dennis Dungs Technical University Munich, Germany Aalborg University, Denmark Januar 2004 Supervised by Hans-Peter Schwefel Aalborg University, Denmark

of 23 Agenda Goal and steps of this project Considered Scenarios –Infrastructure –Mobility –Network traffic Implementation –Network setup –Proxy design Evaluation of some scenarios Future Outline Current Problems

of 23 Goal of this project Goal: –Identify TCP performance lacks in wireless scenarios –Evaluate performance capabilites of a TCP Proxy Steps –Getting familiar with concepts of TCP –Research about common TCP implementations –Describing wireless scenarios –Analyzing TCP performance and Identifying TCP performance lacks in wireless scenarios –Designing and Implementing a TCP Proxy –Evaluation of Scenarios using the TCP Proxy

of 23 Considered Scenarios Definition: „A Scenario consists of the network infrastructure, mobility and network traffic.“ Network Infrastructure: –Access Technology –Proxy Location –Sender / Receiver Location –Network configuration ProxyServer Wired Network Mobile Host Wireless supporting Network

of 23 Considered Scenarios Mobility –Fixed position –Handover to same subnet –Handover to different subnet –Handover to new access technology BT -> WLAN -> GPRS -> W-CDMA Network traffic –Size of transmitted data –Used bandwith –Single-/Multi-User –Cross-traffic BSC WLAN AP Mobile Node WLAN AP GPRS Network Router Switch

of 23 Implementation

of 23 Implementation of TCP Proxy - Idea Application Split TCP Idea: SenderReceiver Split TCP-Daemon TCP IP LL / PHY Application TCP IP LL / PHY TCP IP LL / PHY TCP IP LL / PHY TCP Proxy

of 23 Implementation of TCP Proxy - Options IP-Header-Option-Solution –Add original IP-Destination-Adress to IP-Header Option –Send every IP packet to Proxy –Unpack IP-packets at Proxy and start a „normal“ TCP/IP-Connection –Disadvantage: Changes in TCP/IP-Stack of connection initiator necssary IP-Tunneling –Tunnel the IP-packets from connection initiator to Proxy –Unpack IP-packets at Proxy and start a „normal“ TCP/IP-Connection –Disadvantage: additional IP-Overhead Hardware - Solution –Proxy directly integrated in Sender-Receiver-Path –Disadvantage: Different Scenarios need different locations of proxy -> Maintainance efforts ARP – Solution –„emulate“ IP Adresses by faking IP-MAC-Maps –Disadvantage: Difficult to maintain maps –Disadvantage: Timing problems Routing-Solution

of 23 Implementation of TCP Proxy – Network setup 10.10.4.X Tokyo Delft Legend: Proxy Aalborg Fixed Host Mobile Host Spjald Router 10.10.254.254 Mobile Node San Francisco Toronto Server 10.10.1.254 Toronto Switch WLAN Access Point 8 MBit/s 100 MBit/s Policy-Based Routing applied

of 23 Implementation of TCP Proxy – Software Architecture NIC Packet-buffer NIC Packet-buffer decode encode Connection Send data establish connection close connection Process packetCreate packet(s) Send data Data buffer (Mirror) Split TCP daemon

of 23 Implementation of TCP Proxy – Current Features Mirroring Split TCP: –TCP Reno implementation –Slow start –Congestion avoidance –Retransmission timer (partially) –Fast retransmission –Delayed ACKs –Adjustable Maximum Segment Size –Adjustable data buffer –Asymetrical TCP setup

of 23 Evaluation

of 23 Evaluation - Parameters Throughput over time Round-Trip-Times (RTT) –Average –Jitter Transmission time Nr. of packets Nr. of retransmitted bytes Nr. of timeouts –Transmission timeouts

of 23 Evaluation – Measurement Procedure IPerf –Setup a TCP connection from sender to receiver –Send data from sender to receiver at maximum bandwith Ethereal –Trace packets at sender and receiver in real-time into a file TCPTrace –Generate TCP Statistics offline GNUPlot –Visualizing TCP Statistics (RTT Graphs, Throughput Graphs)

of 23 Evaluation – RTTs in WLAN Comparison of RTTs in WLAN –AP transmission power: 30 mW –Distance to AP: 20 cm –Transmission period: 10 s –TCP Proxy configuration: Delayed ACKs off No Buffer Thresholding MSS: 1460 Bytes SamplesAverageMaxMinStd. Dev. No Proxy249416 ms57 ms3 ms Mirror250021 ms60 ms3 ms5 ms Split TCP Proxy 445522 ms70 ms3 ms5 ms

of 23 Evaluation – Distances in WLAN Room 4 Room 3 Room 2 Room 1 Position #1 Position #2 Position #3 Position #4 Legend: Mobile Host WLAN Access Point

of 23 Evaluation – Distances in WLAN Measurement Options: AP transmission power: 30mW Transmission time: 10s Proxy turned off

of 23 Evaluation – Delayed ACKs in WLAN Measurement Options: AP transmission power: 30mW Distance to AP: 20cm Transmission amount: 30MB Symmetrical TCP setup Delay Timer: 500ms MSS: 1460 bytes No Buffer Thresholding

of 23 Evaluation – Delayed ACKs in WLAN Measurement Options: AP transmission power: 30mW Distance to AP: 20cm Transmission amount: 30MB Symmetrical TCP setup: Delayed ACKs: 3 MSS: 1460 bytes No Buffer Thresholding

of 23 Evaluation - WLAN More Results (not shown here): –Test-setup (Ethereal) results in bursty captures –Impact of TCP Proxy on Wired->Wired scenario comparable to WLAN –Sender correlates to Receiver in WLAN –Upstream correlates to Downstream in WLAN –No TCP Retransmissions over WLAN Conclusions: –L2-Retransmissions efficient in tested WLAN scenarios –Standard TCP efficient in tested WLAN scenarios

of 23 Future Outline Implementation: –Developing TCP-Mechanism for Handover-Detection –FreezeTCP Freeze Sender by advertising a zero Window Recover sender by: –3 Duplicate ACKs (slow-start) –1 Non-Zero Window ACK (fast recovery) Evaluation: –Impact of Buffer-Thresholding –Multi-User WLAN Scenarios –GPRS –Bluetooth –W-CDMA –MobileIP / Handover Scenarios

of 23 Current Problems Ethereal not working with PPP in Windows NT/2000/XP (-> BT LAN, GPRS) No globally routable IP-Address available in GPRS Handover to same subnet: switching table MobileIP not running MobileIP-Setup over GPRS No Bluetooth Equipment available No W-CDMA Equipment available Bugs,....

of 23 References Project WebSite: http://kom.auc.dk/~dennis/ http://kom.auc.dk/~dennis/ IPLab WebSite: http://kom.auc.dk/iplab/ WLAN Evaluation Project: http://kom.auc.dk/~ruipt/ RFCs : RFC791 (IP), RFC793 (TCP) eMail: dennis@kom.auc.dkdennis@kom.auc.dk

of 23 Thanks for listening! Any Questions?

of 23 Backup

of 23 Current IPLab network architecture IP LAB: Current Architecture Delft Internet Toronto Frankfurt Shanghai SydneyDhaka Tokyo San Francisco 130.225.51.6 10.10.1.2 10.10.2.2 10.10.2.1 10.10.1.1 Aalborg 10.10.2.254 Spjald 10.10.4.2 10.10.1.254 Shanghai 10.10.3.254 10.10.254.254 Toronto 10.10.3.1 GPRS Network

Slide 1 of 23 Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP Master Thesis Project (Sep 03 – April 04) Dennis Dungs Technical.

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Slide 1 of 23 Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP Master Thesis Project (Sep 03 – April 04) Dennis Dungs Technical.

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Presentation on theme: "Slide 1 of 23 Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP Master Thesis Project (Sep 03 – April 04) Dennis Dungs Technical."— Presentation transcript:

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