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Future Aeronautical Communications Part 5

Tham khảo tài liệu 'future aeronautical communications part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 88 Future Aeronautical Communications to reduce the unnecessary packet retransmissions and congestion control actions due to vertical handovers. In other words they developed mechanisms to help TCP to reduce retransmission overhead when operated in wireless environment in which handovers may occur on events such as the links properties are interchanged between high low delays high low bandwidth or upon retransmission timeouts RTOs during disconnection. On the other hand allowing TCP to establish a session for every transmission brings three disadvantages. Figure 5 illustrates this approach in comparison with the single TCP connection discussed previously . First for every message to be received Tw should be waited before the first bit of the actual data delivery which affects the delivery time of the message. Secondly the overhead introduced by TCP because of the connection initiation and shutdown is on average large compared to the sizes of the messages produced by the ATM services. Finally the cwnd of a TCP sender will not be able to capture the congestion status when operating below aeronautical services because of the traffic pattern they adhere. Fig. 5. Transport layer TCP connections as envisaged in c and d In Muhammad Berioli 2010 we developed a model to theoretically estimate the overhead produced by different transport protocols when transferring a file. The investigations showed that for small file sizes reliable connectionless transport protocols with no congestion and flow control have the lowest overhead cost. In this work we extend the model to measure the overhead produced by the connection establishment and shutdown mechanisms of TCP. According to the specification of TCP in Postel 1981 to start a session a client should send a SYN packet to the server that will respond with a SYN ACK and finally the client will confirm with an ACK 3-way handshake . On the other hand when the server finishes transferring the file it will send a FIN packet and the .