•Physical – transmission of raw bits over a communication channel, e.g. RS-232-C
•Data Link – reliable transmission of a block of data (frame)
•Put as special bit pattern on the start and end of each frame.
•Compute a checksum by adding up all the bytes in the frame.
•Network – describes how packets in a network of computers are to be routed.
•IP (Internet Protocol) is a connectionless protocol.
•The virtual channel in ATM (asynchronous transfer mode) is a connection-oriented network layer protocol.
•Transport – logical communication channel between processes (message)
•TCP (Transmission Control Protocol): connection-oriented, reliable communication.
•UDP (Universal Datagram Protocol): connection-less unreliable (best-effort) datagram communication.
•TCP for transactions (T/TCP): A TCP protocol combines setting up a connection with immediately sending the request, and sending an answer with closing the connection.
•RTP (Real-time Transport Protocol) is used to support real-time data transfer.
b) Transactional TCP.
•Session – dialog control between end applications
•Presentation – data format translation
•Application – e.g. ftp, telnet, Web browser, and etc.
•FTP (File Transfer Protocol)
•HTTP (HyperText Transfer Protocol)
