11. Computer Networks Service Primitives A service is formally specified by a set of primitives ( operations) available to a user process to access the service. Send a message to the peer SEND Terminate a Connection DISCONNECT Block waiting for an incoming message RECEIVE Establish a connection with a waiting peer CONNECT Block waiting for an incoming connection LISTEN Meaning Primitive

12. Computer Networks Client Machine Server Machine 1)Connection Request 2)ACK 3)Request for Data 4)Reply 5)Disconnect 6)Disconnect How communication takes place?

15. Computer Networks Layers in OSI

16. Computer Networks Layers in OSI

23. Computer Networks Windowing: The quantity of data segments (in bytes) that the transmitting machine is allowed to send without receiving an acknowledgement for them is called window. Acknowledgments: Non-duplication of data is achieved through positive acknowledgement with re transmission. The sender documents each segment it sends and waits for this acknowledgement before sending the next segment. It starts a timer and retransmits if it expires before an acknowledgement is returned from receiving end. The Transport Layer ( Cont…)

25. Computer Networks The Network Layer ( Cont…)

28. Computer Networks The TCP/IP Model

32. Computer Networks The Host to Host Layer TCP/IP Segment Format

34. Computer Networks The Host-to-Host Layer The Internet Layer