Internet started as an experimental network for researchers and primarily was used as a medium for applications like file transfer and email. Some of the modern applications like video transmission over IP network require certain guarantees in terms of available network bandwidth. Packet loss directly affects the perceived quality of the video and packet loss can be caused by network congestion, which results in dropped packets.The QoS solutions for video transmission over IP network presently include integrated services (IntServ) [4], differentiated services [5], and multiprotocol label switching (MPLS) [6]. Among them, the DiffServ is regarded as a dominant protocol for its flexibility, scalability, and capability of QoS guarantee. An extensive simulation model has been developed to study the performance and viability for the video transmission over IP Network. The performance of video over DiffServ is studied with extensive simulation results and by comparing the performance of improved token bucket TCM algorithm with existing srTCM (single-rate three color marker) [2] and trTCM (two-rate three-color marker) [3] algorithms over DiffServ network. The paper suggests a mechanism (improved token bucket TCM) in order to improve the quality of video over Internet. The enhancement mechanism shows a sizable improvement in terms of reducing the total packet loss during the video communication. Keywords - DiffServ , IntServ ,srTCM, trTCM, QoS