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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 2002
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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.
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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………….
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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
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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.
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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.
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What is ATCP? Ad hoc ATCP
ATCP listen to the network state,
information provided by the
ECN, explicit congestion notification
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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.
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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.
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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
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Design Characteristics:
Maintain TCP’s congestion control behavior
Appropriate CWND behavior
Maintain end to end TCP semantic
Be compatible with standard TCP
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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
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Implementation of the ATCP:
ATCP
behavior in the normal state
I
m
p
ATCP
behavior in the loss state
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ATCP
behavior in disconnected state
m
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ATCP
behavior in congestion state
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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 1/3rd reduction time for ATCP as compared with TCP
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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
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