1 / 26

Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP

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. Agenda.

christopher-moss
Download Presentation

Implementation and Evaluation of a Performance Enhancing Proxy for Wireless TCP

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. 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

  3. 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

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

  5. Considered Scenarios BSC GPRS Network WLAN AP • 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 Switch Mobile Node WLAN AP Router WLAN AP

  6. Implementation

  7. Implementation of TCP Proxy - Idea Split TCP Idea: Sender Receiver TCP Proxy Application Application Split TCP-Daemon TCP TCP TCP TCP IP IP IP IP LL / PHY LL / PHY LL / PHY LL / PHY

  8. 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

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

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

  11. 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

  12. Evaluation

  13. 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

  14. 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)

  15. 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

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

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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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,.... 

  23. References • Project WebSite: 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.dk

  24. Thanks for listening! Any Questions?

  25. Backup

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

More Related