Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

Application Layer Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

Reference model

Node A Node B

1.Physical Layer

Node A Node B

Physical Layer Physical Layer

The Physical layer is the layer that decides what signals will be transmitted on the LAN medium. At this level, the network is concerned only with transmitting bits 1’s and 0’s through the network.

Node A

Data Link Layer Data Link Layer

Node B

Breaking message (frame) into bits and constructing bits to message (frame)

Responsible for node to node communication

2.Datalink layer

3.Network Layer

Node A

Network Layer Network Layer

Node B

Breaking packet into frame and construct frame into packet

The unit of information at the network layer is called a packet and the network layer is concerned with routing packets through a network.

4.Transport Layer

Node A

Transport Layer Transport Layer

Node B

A reliable service in a network term means that a transmitting node will always receive a confirmation when a message is correctly received and perhaps an error report in the message is messed up. The transport layer provides quality services and accurate delivery by performing error detection and correction .It ensures that data is received completely ad in a proper order.

Node A

Session Layer Session Layer

Node B

5.Session Layer

The session layer establishes a formal dialogue between nodes. Basically it does two works

(1) Synchronization : synchronize data transfer

(2) Token management: The node which have a token will connect with the server

Node A

Presentation Layer Presentation Layer

Node B

6.Presentation Layer

The presentation concerns with

(1) Data Encryption

(2) Data compression

(3) Format conversion

Node A

Application Layer Application Layer

Node B

7.Application Layer

The application layer is the layer that supports the application of users and enables them to connect to the network. This layer does following works.

(1) Protocol for remote file access.

(2) File transfer services

(3) Remote transfer services

(4) Global directory services to locate resources on the network.

(5) Remote job execution