Done by: Mardonov B

Level functions:

• establishes network connections;
• defines routing in the network and communication between networks (internet protocol);
• ensures the independence of higher levels from the physical medium used for information transfer

The main task of the network layer is data routing (transfer of data between networks)
NETWORK LAYER
Example of a network consisting of several networks (internet)
AB network address
Node address 10
AA network address
AA network address
Node address 3
AB network address
Node address 12
ROUTER
AA network address
Node address 10
AC network address
Node address 5
AC network address
DATA LINK LAYER
The link layer is intended for organizing access to the data transmission medium, converting packets into frames (frames) and data transfer from the network layer to the physical layer.
The level determines:

• logical topology of the data transmission network;
• method of access to the data transmission medium;
• physical addressing;
• services for establishing connections between stations.

The data link layer converts the data received from the network layer intoframe(frame), and then into a sequence of bits for transmission over the communication line (physical layer).
Frameis a logically organized structure in which data can be placed.

Link layeralso responsible for error control,atdata flow control and physical station addressing
DATA LINK LAYER
simple data frame
PHYSICAL LAYER
The physical layer defines the mechanical and electrical
characteristics of the transmission medium and interface equipment.
Leveldetermines the number and purpose of contacts on the network
connectors, in what form bits are transmitted, what types of cable can
be used etc. .
Functions at this level provide
establishing, maintaining and terminating a physical connection between
network nodes upon request from the link layer.
At this level, the package is considered asbit sequence

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