network layer esy to understand

TCP/IPThe Internet Protocol Suite, popularly known as the TCP/IP model, is a communication protocol that is used over the Internet. This model divides the entire networking functions into layers, where each layer performs a specific function.

This model gives a brief idea about the process of data formatting, transmission, and finally the reception. Each of these functions take place in the layers, as described by the model. TCP/IP is a four-layered structure, with each layer having their individual protocol. Let us have a look at the four layers:

Link Layer

As the name suggests, this layer includes the physical and logical connections from the host’s link. It is also known as Network Access layer and Network Interface layer. It explains how the data is transmitted from the host, through the network. The physical connectors like the coaxial cables, twisted pair wires, the optical fiber, interface cards, etc., are a part of this layer. This layer can be used to connect different network types like ATM, Token ring, Ethernet, LAN, etc.

Internet Layer

This layer is also known as the Network Layer. The main function of this layer is to route the data to its destination. The data that is received by the link layer is made into data packets (IP datagrams). The data packets contain the source and the destination IP address or logical address. These packets are sent on any network and are delivered independently. This indicates that the data is not received in the same order as it was sent. The protocols at this layer are IP (Internet Protocol), ICMP (Internet Control Message Protocol), etc.

Transport Layer

This layer is responsible for providing datagram services to the Application layer. This layer allows the host and the destination devices to communicate with each other for exchanging messages, irrespective of the underlying network type. Error control, congestion control, flow control, etc., are handled by the transport layer. The protocol that this layer uses is TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP gives a reliable, end-to-end, connection-oriented data transfer, while UDP provides unreliable, connectionless data transfer between two computers.

Application Layer

It provides the user interface for communication. This is the layer where email, web browsers or FTP run. The protocols in this layer are FTP, SMTP, HTTP, etc.

Read more at Buzzle: OSI
Implementation of OSI model Reference model
Model around which Internet is developed This is a theoretical model
Has only 4 layers Has 7 layers
Considered more reliable Considered a reference tool
Protocols are not strictly defined Stricter boundaries for the protocols
Horizontal approach Vertical approach
Combines the session and presentation layer in the application layer Has separate session and presentation layer
Protocols were developed first and then the model was developed Model was developed before the development of protocols
Supports only connectionless communication in the network layer Supports connectionless and connection-oriented communication in the network layer
Protocol dependent standard Protocol independent standard
Read more at Buzzle: 

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