Connection Oriented Multiplexing And De multiplexing
TCP socket identified by 4 tuple:
a.Source IP address
b.Source port number
c.Destination IP address
d.Destination port number
When a TCP segment arrives form the network to a host the host uses all four values to direct the segment to the appropriate socket. In particulars with different source IP addresses or source port numbers will be directed to two different socket.
The server host may support may is simultaneous TCP sockets with each socket attached to a process and with each socket identified by its own four tuple when a TCP segment arrives to the host all fours fields are used to direct the segment to the appropriate socket.
The situations illustrated in figure in which host c initiates two HTTP sessions to server B and host A initiates one HTTP session B hosts A and C and server B each have their own unique IP address A , C and B, respectively host C assigns two different source port number its two HTTP connections. Because host A is choosing source port number independently of C. It might also assign a source port of 61452 to its HTTP connection. Nevertheless sever B will still be able to correctly de multiplex the two connection having the same source port number since the two connections have different source IP addresses.
figure two clients using the same destination port unmber (80) to communicate with the same web server application