Investigating the Performance of Tcp Variants and Routing Protocols in Mobile Ad Hoc Networks
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Date
2014-06
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Addis Ababa University
Abstract
Mobile Ad Hoc Network (MANET) is a collection of mobile nodes that can
dynamically and randomly move and self organize to form network topology.
MANETs have provided new challenges, which are the results of the unique
characteristics of the wireless medium, the dynamic nature of the network
topology, lacks of well secured boundaries, route failure due to frequent link
breakages, wireless channel error, and using multi-path routes, which affects
the end-to-end transmission of data. Transmission control protocol (TCP)
performs poorly in such networks, since TCP’s congestion control mechanism
cannot distinguish between congestion and non-congestion related packet
losses. TCP was previously developed for wired networks with the assumption
that packet loss is an indication of congestion. However, in MANET TCP
performs congestion control action for several types of losses that are not
related to congestion. Consequently, when a packet loss is detected either by
timeout or three duplicated acknowledgments, TCP slows down the sending
rate by adjusting its congestion window size (cwnd) and unnecessarily
retransmit a packet, which leads to lower throughput.
In this dissertation research, we have proposed a method for TCP to
distinguish between packet losses due to congestion or route failure due to
mobility of nodes. The proposed protocol is called TCP Packet Loss Detection
and Response (TCP-PLDR). We have developed an analytical model of
throughput of TCP with selective acknowledgment (TCP-SACK) and TCPPLDR
protocols as a function of packet loss probability and round trip time
(RTT), in the presence of congestion and route failure losses. The model
captures the behavior of TCP’s congestion avoidance mechanism and its
impact on throughput. Results have shown that TCP-PLDR is TCP friendly
while it improves the throughput of TCP-SACK when there is a packet loss
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due to route failure/change. Simulation was conducted using network
simulator (ns-2) and results have shown that TCP-PLDR improves TCPSACK’s
performance in MANET. As an example, simulation experiment for
route failure and congestion loss scenario shows that TCP-PLDR improves
the throughput of TCP-SACK on average by 39%. Moreover, the proposed
protocol (TCP-PLDR) was evaluated in the presence of wireless channel error,
and multi-path routing protocol like temporally-ordered routing algorithm
(TORA) by making use of throughput, end-to-end delay, and packet delivery
ratio (PDR) performance metrics and results showed that TCP-PLDR
performed better than TCP-SACK.
As stated above, in MANET TCP is unable to distinguish packet losses due to
congestion or route/link failures due to mobility of nodes. Hence the way how
routing protocols respond to route failures and route recovery mechanism
has an effect on the performance of TCP variants. In the second part of this
dissertation paper, the effect of routing protocols; Ad hoc On Demand
Distance Vector (AODV), Destination Sequenced Distance Vector (DSDV),
Dynamic Source Routing (DSR), and Temporally Ordered Routing Algorithm
(TORA), on the performance of TCP variants; TCP-Newreno, TCP-Reno, TCPSACK,
and TCP-Tahoe, under different mobility pattern and node density
were studied thoroughly. Simulation results showed that, for all variants of
TCP, AODV achieved the highest throughput. From TCP variants, TCP
Newreno performed better than the other variants over the stated routing
protocols. Besides, the best performing combination of routing protocols and
TCP variants were identified. It is also confirmed that the performance of TCP
variants are highly dependent on the underlying routing protocols in MANET.
This result was taken as a valuable input to design and study the first part of
this dissertation research. Moreover, performance of TCP-PLDR is compared
with other variants of TCP (TCP-Reno, TCP-Newreno, TCP-Vegas, ATCP, and
TCP-Westwood) and routing protocols (AODV, DSDV, DSR, and TORA). From
TCP variants, in terms of throughput, TCP-PLDR performed better than the
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other variants. Whereas, in terms of delay, TCP-Vegas outperformed the other
variants. From routing protocols, TCP-PLDR can be coupled with AODV and
it is confirmed that TCP-PLDR is more suitable for reactive routing protocol
than proactive in MANET.
In MANET, packet drop attack due to malicious nodes can affect normal
operation of routing protocols, performance of TCP, and performance of the
network at large. The third part of dissertation study investigates the impact
of malicious packet drop attack on the performance of two reactive TCP
variants (Newreno and Sack) and one proactive TCP (Vegas) and two reactive
routing protocols (AODV and DSR) by making use of throughput, end-to-end
delay, and PDR performance metrics. Simulation was conducted by adding
different percentages of malicious nodes in the network. Results showed that
from TCP variants, Vegas outperformed Newreno and Sack in the absence of
malicious nodes (0% malicious nodes). However, as the percentage of
malicious nodes added in the network increases from 5% to 50%, Newreno
and Sack performed better than Vegas though all of them are affected by
malicious nodes. It is also noted that, even though both AODV and DSR
protocols are highly affected by malicious nodes, AODV is more robust to
malicious packet drop attack than DSR.
Finally, performance analysis of TCP-PLDR and TCP-SACK were evaluated
exhaustively under security attack (malicious packet drop attack). Upon
completion of exhaustive simulation, it is confirmed that TCP-PLDR is more
robust to malicious packet drop attack than TCP-SACK.
Keywords: MANET, TCP-PLDR, TCP-SACK, Tahoe, Reno, Newreno, Vegas,
Westwood, AODV, DSDV,DSR,TORA, route failure/change, packet loss, outof-
order packet, congestion, wireless channel error, multi-path route,
malicious packet drop attack.
Description
Keywords
Manet, Tcp-Pldr, Tcp-Sack, Tahoe, Reno, Newreno, Vegas, Westwood, Aodv, Dsdv, Dsr, Tora, Route Failure/Change, Packet Loss, Outof- Order Packet, Congestion, Wireless Channel Error, Multi-Path Route, Malicious Packet Drop Attack