1. 1 The Motivation




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5.4 Call Sequences
This subsection aims to provide an understanding of how voice calls are initiated within the application.
Diagram 11, illustrates a successful call; the calling application will initiate a call, and will wait for a reply. A reject will mean the call in cancelled and both system resume listing for incoming calls. If an Accept signal is received both systems will open the two data channels, one for sending and one for receiving and will send acknowledgements that both channels have been opened. Once the system has received an acknowledgement it will begin transmitting and receiving audio data until a system sends the hang-up signal which will terminate the call and return the systems to listing for connections. With using TCP which is a reliable transport protocol commands are not resent since TCP handles this, as well has closing the connection correctly.



Diagram 11, illustrates the process of a successful call.



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