TCP optimization in mobile ad hoc networks MANETs is a challenging issue because of some unique characteristics of MANETs. Packet losses in MANETs are mainly due to congestion and frequent link failures but in case of wired networks packet losses are mainly due to congestion. To optimize TCP in MANETs we use congestion control and avoidance algorithms. In this paper, we describe an NS2-based simulation analysis of TCP using omni antennas over mobile ad-hoc network. In particular, we compare the performance of end to end protocols such as TCP-Newreno and TCP-SACK with the routing provided by AODV, DSR and DSDV protocols using omni directional antenna. We investigate the effects of varying node density, mobility of nodes and pause time of nodes has on TCP performance. Through simulation, we show that TCP throughput drops significantly when nodes move, due to TCP’s inability to recognize the difference between link failure and congestion. We compare the throughput performance between the TCP versions.