ATCP:TCP Performance Over Mobile Ad Hoc Networks Researched by Suresh Singh of PSU and Jian Liu of Sun Microsystems Presentation by Mir Hashimi CS 401B Mobile computing University of Missouri-Rolla Spring of

Introduction: In this presentation, I will present a solution to the Problem of running TCP in Ad hoc wireless network The solution is to implement a thin layer between IP And TCP called ATCP that ensures correct TCP Behavior while maintaining high throughput. 2

Introduction continue  Ad hoc networks do not have any fixed infrastructure  Nodes can move randomly  Application in real life are:  Battlefield ( group of soldiers)  Cars on a highway  People in a building  Many, many more…………. 3

Problem Statement: It is well known that the TCP performance deteriorate in Mobile Ad hoc network environments. Due to:  Higher BER  Route re-computation  Network partition  Multiple routing 4

Problem Statement: continued What does Congestion Window, CWND really mean in ad hoc networks? In Ad hoc networks since route changes during the lifetime of the connection, the relationship between the CWND size and tolerable data rate for the route. 5

ECN, Explicit Congestion Notification is used as a Mechanism by which the sender is notified of impeding network congestion along the route followed by the TCP Connection. Upon receipt of an ECN the sender invokes congestion control without waiting for timeout event. 6

What is ATCP? Ad hoc ATCP ATCP listen to the network state, information provided by the ECN, explicit congestion notification 7

Benefits of ATCP are:  Standard TCP/IP is unchanged.  ATCP is invisible to TCP and therefore nodes with and Without ATCP can interoperate. Drawback: Nods without ATCP will see all the performance problems associated with running TCP over the Ad hoc network. 8

Motivation behind design of ATCP:  To provide a complete solution to the problem of running TCP over multi-hops wireless network with the following Characteristic:  Improve TCP performance for connections set up in The Ad hoc networks. 9

Motivation behind design of ATCP: TCP performance is affected by the problem of high BER and disconnections due to route re-computation, the appropriate behavior in these cases might be:  High BER  Delay due to route re-computation  Transient partition  Multi path routing 10

Design Characteristics:  Maintain TCP’s congestion control behavior  Appropriate CWND behavior  Maintain end to end TCP semantic  Be compatible with standard TCP 11

Functioning of the ATCP layer: ATCP layer is only active at the TCP sender, this will Monitor state of the network and takes appropriate action ATCP States:  Loss channel  Normal  Congested  Disconnected 12

Implementation of the ATCP:  ATCP behavior in the normal state  ATCP behavior in the loss state  ATCP behavior in disconnected state  ATCP behavior in congestion state 13 Implementation Implementation

Comparison of performance between TCP and ATCP Jian Liu and Suresh Singh conducted experiment at Portland State University under all effects of network partition, multi-path routing congestion and bit error and concluded A 1/3 rd reduction time for ATCP as compared with TCP 14

Conclusion: The highlights of ATCP are:  End to end TCP semantics are maintained  ATCP is transparent which means that nodes with or  Without ATCP can set up TCP connection normally  ATCP does not interfere with TCP congestion control  behavior When there is network congestion 15