1. TCP Performance in Wireless Multi-hop Networks Mario Gerla, Ken Tang, Rajive Bagrodia Wireless Adaptive Mobility Laboratory Computer Science Department University of California,Los Angeles Reported by 郭婉秀 2001/8/31

2. Outline Introduction Main Idea TCP over MAC Layer TCP Measurements Conclusion

3. Introduction(1/2) Two key requirements of the ad-hoc network environment ： -reliable data transfer -congestion control Both MAC and TCP layers strive to provide efficient transport in a shared environment

4. Introduction(2/2) MAC layer has only a myopic view TCP layer provides a true end-to-end control on errors and congestion Interaction between TCP and MAC layer backoff timer causes unfairness and capture condition Study the TCP/MAC layer interaction via simulation.

5. Main Idea Embedded the ACK in the MAC layer protocol TCP interactive with MAC improves performance

6. Experimental Configuration and Parameters(1/2) Three types of topologies: 1. String Topology 2. Ring Topology 3. Grid Topology

7. Experimental Configuration and Parameters(2/2) Three MAC protocols: 1. CSMA “ hidden terminal ” problem 2. FAMA descendent of MACA (Multiple Access Collision Avoidence) 3. MACAW extends MACA,contains addition control packet

8. TCP over MAC Layer(1/2)

9. TCP over MAC Layer(2/2)

10. Grid Topology

13. TCP Measurements(1/3) Unfairness/capture behavior observed TCP does include the disconnect feature

14. TCP Measurements(2/3)

15. TCP Measurements(3/3)

16. Conclusion MACAW with its ACK feature,MILD backoff provides much better fairness More work on link loss protection