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The goal of recent high-speed TCP implementations is to allow scientists who have access to new high-speed networks to efficiently transfer large datasets to their remote colleagues. As of yet, there is no standard high-speed TCP. Because of this, scientists using one high-speed protocol may find themselves sharing a link with scientists using a different high-speed protocol. Previous work has evaluated such inter-protocol performance, but only with both flows starting at the same time-an unlikely situation. We perform an evaluation study using ns-2 to investigate the performance of competing high-speed TCP flows where one flow enters a network in which another high-speed flow has already reached its maximum data rate. The fairest result would be for the existing flow to cede half of its bandwidth to the new flow in order to allow both flows to evenly share the link. Our results show that in most cases this does not happen, but rather one high-speed flow dominates the other. Surprisingly, it is not always the existing flow that dominates.

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MANET is considered as an infrastructure less data network where the nodes can behave as source or router (packet forwarder) which helps the network to cover the longer distances with low power transmission. Since it does not require any centralized controlling system and can organize itself without external interfere it's a preferable choice for the small battery operated clustered system such mobile and PDA. The self-organizing nature of MANET makes it very flexible and dynamic which can adopt variety of system configuration. Although to provide such services the protocols designed for MANET contains many security loop holes which makes it prone to network attacks and easy target for attackers. Although many types of active and passive attacks currently known, this paper focuses on Sink-hole attack which is a sub-category of Black-hole attack. The sink-hole is considered as one of the most serious attacks in MANET because it force the traffic to pass through attackers node by manipulating the routing protocol and then node drops all the traffic, which causes degradation of networks performance. This paper present an individual trust managing technique to prevent against sink-hole attack. The proposed algorithm is simulated using network simulator NS2 and the results shows that the proposed algorithm greatly reduces the sink-hole impact and performs much better than previous algorithm. General TermsSinkhole attack, trust management technique.