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Most of the traffic in today's network uses the Transmission Control Protocol (TCP) as the transport layer protocol for reliable end-to-end packet delivery. However, TCP considers packet loss to be the result of network congestion which makes it unsuitable for mobile wireless communication, where sporadic and temporary packet losses are usual due to fading, shadowing, hand-off and other radio effects. During the vertical hand-off between different wireless technologies, the problem of end-to-end connection and reliability management for TCP becomes more severe. Intermediate Switching Network (ISN) is an effective framework for vertical handover between the UMTS and the WLAN network. This paper evaluates the performance of TCP over ISN based framework. The proposed scheme uses a cross layer interaction between the data link and the transport layers to estimate TCP retransmit timeout and congestion window during handover. Simulation results establishes effectiveness of the proposed scheme.

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Abstract-In today's age of Next Generation Internet there have been a plethora of diversified overlapping networks where each of these communication technologies are optimized to provide user specific services and Quality of Service(QoS) parameters. The main objective of next generation networks focus at high bandwidth and high mobility. There are WiFi hotspots (WLAN) providing high data rates within smaller areas and UMTS networks providing larger coverage areas with low data rates. These two complementary networks can be combined to quench the thirst for ubiquitous communication enabling the smart mobile user to roam seamlessly between these technologies for best possible services. To ensure Always Best Connectivity, one of the main short comings to be addressed is efficient handoff management and there are a lot of works already published addressing various issues of efficient handoff management till date. This paper provides a comprehensive detail of different handoff management strategies reported so far in a systematic manner and also throws light on a particular scheme of handoff management between UMTS and WLAN providing QoS to the mobile users.Index Terms-RSSI, SINR, VHO.