OSI Reference Model:-
The seven layers of the OSI model are as follows:
- Physical layer:Converts the data into the stream of electric or analog pulses that will actually cross the transmission medium and oversees the transmission of the data
- Data Link layer:Provides an interface with the network adapter; maintains logical links for the subnet
- Network layer:Supports logical addressing and routing
- Transport layer:Provides error control and flow control for the internetwork
- Session layer:Establishes sessions between communicating applications on the communicating computers
- Presentation layer:Translates data to a standard format; manages encryption and data compression
- Application layer:Provides a network interface for applications; supports network applications for file transfer, communications, and so forth
TCP/IP Protocol Architecture
TCP/IP protocols map to a four-layer conceptual model. The four layers of model are: Application, Transport, Internet, and Network Interface. Each layer in model corresponds to one or more layers of the seven-layer Open Systems Interconnection (OSI) model.
The APRANET initially started with four Internet message processors (IMPs), located at the UCLA, UCSA, Stanford research institute and the University of Utah. In the early years, the purpose and usage of the APRANET network was widely discussed, leading to many enhancements and modifications as the users steady increased and requested demanded more from the network. As time passed many enhancements were made to the existing protocol but by 1973 it was clear that NCP (Network Control Protocol) was unable to handle the volume of traffic passing through it network and proposed a new functionality. A new protocol TCP/IP Transmission Control Protocol / Internet Protocol was developed over time to replace NCP.
Difference between TCP/IP and OSI Model
|
TCP/IP modal
|
OSI modal
|
|
1. The TCP/IP model doesn't clearly distinguish between service, interval and protocol.
|
1. The OSI model originally distinguishes between service, interval and protocols.
|
|
2. The TCP/IP model is an implementation of the OSI model.
|
2. The OSI model is a reference model.
|
|
3. In TCP/TP model, the protocols came first, and the model was really just a description of the existing protocols.
|
3. In OSI model, the protocols came after the model was described.
|
|
4. In TCP/IP model , the protocols are not hidden.
|
4. In OSI model, the protocols are better hidden.
|
|
5. The TCP/IP model has only 4 layers.
|
5. The OSI model has 7 layers.
|
|
6. The TCP/IP model supports both connectionless and connection-oriented communication in the transport layer. giving users the choice.
|
6. The OSI model supports both connectionless and connection-oriented communication in the network layer, but only connection -oriented communication in transport layer.
|
|
|
|