ISO and OSI Model:
- ISO Developed a standard for data communication called Open System Interconnection.
- OSI has seven layers.
- o Physical Layer
- o Data Link Layer
- o Network Layer
- o Transport Layer
- o Session Layer
- o Presentation Layer
- o Application Layer
- This layer deals with system of bits.
- Collect data from upper layer and send it to required computer in the form of bits.
- RS-232 connector is used for data transmission.
Data Link Layer:
- Responsible for node-to-node delivery of message.
- Control the rate of flow of data.
- It decides which path of data should send from one node to other.
- Switches, Routers and NIC Cards (Network interface card) decides the routing based on network conditions, priority of service and other factors.
- TCP/IP is very important protocol of this layer.
- Responsible for end-to-end delivery of entire message.
- If the link goes down then this layer send data into other link (Path).
- Arrangement of data in its order.
- Remove errors.
- Control rate of flow of data.
- Establish a connection between two-application across network.
- Its function is performing
- o Security
- o Logging
- o Administration
- This layer represents data in user understandable form.
- Techniques used are
- o Translation
- o Encryption
- o Compression
- This layer serves the user.
- User can control it directly.
- It includes services such as o E-mail
- o File sharing
- o File printing and other software