  In a mobile ad hoc network, temporary link failures and route changes occur
frequently. With the assumption that all packet losses are due to congestion,
TCP performs poorly in such an environment. There are many versions of TCP
which modified time to time as per need. In this paper modifications introduced
on TCP New Reno over mobile ad-hoc networks using calculation of New
Retransmission Time out (RTO), to improve performance in term of congestion
control. To calculate New RTO, adaptive backoff response approach (ABRA) in TCP
New Reno was applied which suggest ABRA New Reno. It utilizes an ABRA by which
congestion window and slow start threshold values were decreased whenever an
acknowledgement is received and new backoff value calculate from smoothed round
trip time. Evaluation based on comparative study of ABRA New Reno with other
TCP Variants like New Reno and Reno was done using realistic parameters like
TCP Packet Received, Packet Drop, Packets Retransmitted, Throughput, and Packet
Delivery Ratio calculated by varying attributes of Node Speed, Number of Nodes
and Pause Time. Implementation and simulations were performed in QualNet 4.0
simulator.
