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The Seven Layers of OSI Model

The Seven Layers of OSI Model:

OSI Model – TCP/IP Model

Application Layer 7:
This is the layer actually interacts with the OS or application whenever the user chooses to transfer files or read files or to perform other network related activities.
Protocols at Application Layer:
Network virtual terminal, file transfer, access management, mail services and directory services.

Presentation Layer 6:
It takes the data provided by the application layer and converts to a standard format that other layers can understand.
Encryption & Decryption: Responsible for translate, encrypt and compress data.

Session Layer 5:
It establishes, maintains and ends communication with receiving a device.
Dialogue control & Token management takes place at this layer.

Transport Layer 4:
This layer maintains the flow control of data and provides error checking and recovery of data between devices.
Flow control means that the transport layer looks to see whether the data is coming from more than one application and then integrates each application’s data into a single stream for the physical network.

Network Layer 3:
The way the data sent to receiving device is determined. Fragmenting, switching, routing, addressing, congestion control, packet sequencing.

Data Link Layer 2:
Appropriate physical protocols assigned to the data. Also, the type of network and packet sequencing is defined. Data sent by network layer is divided into frames and it deals network topology and ensures the data to be delivered on intended device on LAN.

Physical Layer 1:
This is the level of actual hardware and it communicates data between systems bit by bit. It defines physical characteristics of the network such as connections, voltage levels.
Physical layer gets frames sent by data link layer and converts them into signals to make it easy with the transmission media.
If a metallic cable is used then it will convert data into electrical signals.
If a wireless cable is used then it will convert data into electromagnetic signals.
When receiving data, this layer will get signals received and convert it into (0’s and 1’s) and send them to the data link layer.

What are the devices used at different layers of OSI model?

Physical Layer: Hubs.
Data Link Layer: Switches.
Data Link Layer: Bridges.
Network Layer: Routers, Gateway
Physical Layer: Repeater.

Complexities of Different Algorithm:

• Linear search algorithm (LSA) = O (n).
• Binary Search Algorithm (BSA)= O (log n).
• Bubble Sort Algorithm = O (n2).
• Merge Sort Algorithm = O(n log n).

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