18-03-2011, 06:37 PM
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 | M.Arsalan Qureshi | | Join Date: Oct 2008 Location: Garden Town, Multan Cantt
Posts: 616
Program / Discipline: BSTS Class Roll Number: 09-31 | |
 Network Layer: Delivery, Forwarding, and Routing
Network Layer: Delivery, Forwarding, and Routing
* UDP and TCP are transport-layer protocols that create a process-to-process communication. * UDP is an unreliable and connectionless protocol that requires little overhead and offers fast delivery. * In the client-server paradigm, an application program on the local host, called the client, needs services from an application program on the remote host, called a server. * Each application program has a unique port number that distinguishes it from other programs running at the same time on the same machine. * The client program is assigned a random port number called the ephemeral port number. * The server program is assigned a universal port number called a well-known port number. * The combination of the IP address and the port number, called the socket address, uniquely defines a process and a host. * The UDP packet is called a user datagram. * UDP has no flow control mechanism. * Transmission Control Protocol (TCP) is a connection-oriented, reliable, stream transport-layer protocol in the Internet model. * The unit of data transfer between two devices using TCP software is called a segment; it has 20 to 60 bytes of header, followed by data from the application program. * TCP uses a sliding window mechanism for flow control. * Error detection is handled in TCP by the checksum, acknowledgment, and time-out. * Corrupted and lost segments are retransmitted, and duplicate segments are discarded. * TCP uses four timers—retransmission, persistence, keep-alive, and time-waited—in its operation. * Connection establishment requires three steps; connection termination normally requires four steps. * TCP software is implemented as a finite state machine. * The TCP window size is determined by the receiver.
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