This document discusses improving TCP performance over mobile ad-hoc networks. It first introduces TCP and how it is generally used for wired networks where packet loss indicates congestion. However, in wireless mobile ad-hoc networks (MANETs), packet loss can occur for other reasons like interference or fading. The document then outlines some key challenges for TCP in MANETs, such as route failures, shared wireless medium issues, high bit error rates, and inability to differentiate congestion losses from other losses. It reviews some approaches to improve TCP performance in MANETs, including modified TCP, cross-layer solutions, ATP, and ADHOCTCP which aims to identify network state like congestion or errors. The conclusion is that TCP needs

1. IMPROVING TCP
PERFORMANCE OVER
MOBILE AD-HOC
NETWORKS
NAME: ARPITA NASKAR
ENROLLMENT NO: 12017009001104
SECTION: CSE3C ROLL NO.: 46

2. INTRODUCTION
TCP [Transmission Control Protocol] is generally used
in wired networks. In wired networks there is an
assumption that packet loss is an indication of
congestion. In wireless networks like MANET [Mobile
Ad-Hoc Network], there is no assumption like that.
That is why MANET can improve TCP performances.

3. TCP (Transmission Control
Protocol)
TCP (Transmission Control Protocol) is a standard
that defines how to establish and maintain a
network conversation through which application
programs can exchange data. TCP works with the
Internet Protocol (IP), which defines how
send packets of data to each other. Together, TCP
and IP are the basic rules defining the Internet.

4. MANET (MOBILE AD-HOC
NETWORK)
MANET is also called as wireless ad-hoc network that
usually has a routable networking environment on top
of a Link Layer ad-hoc network. These consist of set of
mobile nodes connected wirelessly in a self-
self-healing network, without having a fixed
infrastructure. Each node behaves as a router as they
forward traffic to other specified node in the network.

5. MOBILE AD-HOC NETWORK

6. CHALLENGES FOR TCP IN
MANETS
I. Route failure and network partition: In wireless ad
hoc networks nodes are free to remain static or
as well as can join or leave the network without any
restriction. As a result, two types of problems arise.
One is frequent route failure and another is network
partition.

7. CHALLENGES FOR TCP IN
MANETSII. Shared medium
(a) Hidden and exposed node problem
(b) Channel contention: In IEEE 802.11 networks, owing
to the shared medium, there exists a race condition among
nodes for medium access. As a result, the transmissions of data
packets and their ACKs lead to channel contention which
collision and packet loss.

8. CHALLENGES FOR TCP IN
MANETS
 III. High bit error (random losses): In a wireless network, the
bit error rate is high compared to a wired network. In a wired
network, the losses due to bit corruption or link errors can
negligible.
 IV. Unable to differentiate congestion losses from other
losses: packet loss is very high in wireless networks
compared to wired networks. Packet loss may be due to
interference, fading or channel contention, but TCP assumes
that all packet losses are congestion losses, which leads to
activation of congestion control and a reduction in the cwnd.

9. APPROACHES TO IMPROVE TCP
PERFORMANCES IN MANET
 Modified TCP: This represents a class of transport layer
approaches, where minor modifications are made to the TCP
protocol to adapt it to the characteristics of an ad-hoc
network, but the fundamental elements of TCP are still
retained.
 TCP aware Cross Layer Solutions: This represents a class of
lower layer approaches that hide from TCP the unique
characteristics of ad-hoc networks, and thus necessitate
minimal changes to TCP. Such approaches can be used in
tandem with the approaches in the previous class.

10. APPROACHES TO IMPROVE TCP
PERFORMANCES IN MANET
 ATP (ad-hoc transport protocol): It is tailored toward the
characteristics of ad-hoc networks. ATP consists: rate based
transmissions, quick-start during connection initiation and
route switching, network supported congestion detection
and control, no retransmission time outs, decoupled
congestion Control and reliability, and coarse grained
receiver feedback.
 ADHOCTCP: In this approach we have to identify the network
state CONGESTION, CHANNEL ERROR & DISCONNECTION to
improve the performance of TCP. We use end to end
measurements to identify the presence of congestion in the
network.

11. CONCLUSION
 As the assumption made by TCP that any packet loss is due to
network congestion is not valid in ad hoc networks, either TCP
should be capable of distinguishing various reasons of packet
losses or such non-congestion related losses should be
reduced. To enable TCP to identify various causes of packet
losses there are so many approaches; some of them are
discussed in this presentation. The feedback based solutions
are the best way to improve TCP performance.

12. REFERENCES
 [1] W. Richard Stevens TCP/IP Illustrated, Volume 1, The
Protocols, AWL, 1994 .
 [2] G. Holland and N. Vaidya, “Analysis of TCP performance
over mobile ad hoc networks,” MOBICOM’99.
 [3] H. Balakrishnan, S. Seshan, E. Amir, and R. Katz, “Improving
TCP/IP performance over wireless networks,” MOBICOM’95.
 [4] S. Biaz and N.H. Vaidya, ”Distinguishing congestion losses
from wireless transmission losses” IEEE 7th Int. Conf. on
Computer Communicationsand Networks, October 1998.

13. ACKNOWLEDGEMENT
I have given efforts in this power point presentation. However, it
would not have been possible without the kind support and help
of many teachers. I would like to extend my sincere thanks to all
of them.
I am highly indebted to THE CSE DEPARTMENT for their
guidance and constant supervision as well as for providing
necessary information regarding the power point presentation &
also for their support in completing the power point
presentation.

14. THANK
YOU