Explain the OSI ( Open Systems Interconnection ) reference model with diagram? Solution:-
OSI means open System Interconnect model. It was developed by the International organization for standardization in 1974. It consists of seven layer, each layer has specific processing function.
1. Application layer: It is responsible for providing network services to the user. It is also known as desktop layer.
2. Presentation layer: It is responsible for concerting data into standard format. eg. ASCII, JPG, MPG, BMP.
3. Session layer: It is responsible for establishing maintaining and terminating session. Session ID work at session layer.
RPC- Remote procedure call
SQL- Structured query language
NFS- Network File System
4. Transport layer: It is responsible for end- to- end connectivity. It is also known as the heart of OSI layers. Following tasks are performed at transport layer:
i. Indentifying service
ii. Multiplexing and De-multiplexing
iii. Segmentation
iv. Sequencing and reassembling
v. Error correction
vi. Flow control
5. Network layer: It is responsible for providing best path for data to reach the destination. Logical addressing works on this layer. Router is a Network layer device.
6. Data link layer: It is divided into two sub layers.
a. LLC: Logical link control which talks about WAN protocols.
b. MAC: Media Access Control which talk about physical address. It is responsible for error detection also.
7. Physical layer: It is responsible for electrical mechanical and procedural checks. Data will be converted into Binary (i.e.) O's and I's devices working at physical layer are Hubs, Repeaters, cable, Modem etc.
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