STANDARDIZATION

There are:
· Many types of connection media: telephone lines, optical fibers, cables, radios, etc.
· Many different types of machines and operating systems
· Many different network applications
So the need for a STANDARD in communication technology: OSI model

THEORY: THE OSI MODEL
THE ISO STANDARD MODEL FOR COMMUNICATIONS: OSI

ISO (the International Organization for Standardization) has developeda standard model for communications, called the
OSI (Open Systems Interface) Model
Model = it means that it's only theory! In fact the OSI model is not yet fully implemented in real networks.
Open System: It can communicate with any other system that follows the specified standards, formats, and semantics.
Protocols give rules that specify how the communication parties may communicate.
Supports two general types of protocols. Both are common.
Connection-Oriented :
Sender and receiver first establish a connection, possibly negotiate on a protocol. (virtual circuit)
Transmit the stream of data.
Release the connection when done.
E.g. Telephone connection.
Connectionless
No advance setup is needed.
Transmit the message (datagram’s) when sender is ready.
E.g. surface mail