PROGETTO E REALIZZAZIONE DI UN PROTOCOLLO DI TRASPORTO PER RETI AD HOC MULTI-HOP

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A Mobile Ad hoc Network (MANET) is a collection of mobile nodes connected together over a wireless medium, which self-organize into an autonomous multi-hop wireless network. This kind of networks allows devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments.This thesis examines the problems encountered by TCP over multi-hop ad hoc networks. TCP is not able to efficiently deal with the unstable and very dynamic environment provided by multi-hop ad hoc networks. This is because TCP implicitly assumes that packet loss is almost always due to congestion phenomena causing buffer overflows at intermediate routers. Furthermore, it also assumes that nodes are static (i.e., they do not change their position over time). Unfortunately, these assumptions do not hold in MANETs, since in this kind of networks packet losses due to interference and link-layer contentions are largely predominant, and nodes may be mobile. This thesis presents a new lightweight transport protocol (TPA) designed from scratch, that provides a connection-oriented, reliable type of service. TPA differs from TCP in a number of ways. Specifically, the data transfer and the congestion control algorithms have been re-designed. Furthermore, TPA explicitly detects and deals with both route failures and route changes and it can also leverage cross-layer interactions with the routing protocol, when available. This thesis also includes a preliminary simulative evaluation of TPA