OSI is the acronym for open system interconnection. It describes how information from one software application in one computer moves through communication medium to software application in another computer. OSI itself is not a network architecture because it does not specify the exact services and protocols to be used in each layer. It just tells what each layer should do.
Physical and Data link layer are implemented in hardware and software. Other remaining layers are implemeted in only software.
- PDU: packet
- provides routing and related functions that enable multiple data links to be combined into and internetwork. This is accomplished by using logical addressing of devices.
- supports both connectionless and conection-oriented services from higher layer protocol.
- Network layer protocols typically are routing principle but other types of protocols are implemented as well
- provides congesgtion control , best path determinations.