NETWORK:
A network is a combination of hardware and software that sends data from one location to another. The hardware consists of the physical equipment that carries signals from one point of the network to another. The software consists of instruction sets that make possible the services that we expect from a network.
DATA TRANSFER:
Data is transmitted from one machine(sender) to another(receiver).
In which data goes through many layers and then it will be received by receiver at the next end. Data transfer is the process of using computing techniques and technologies to transmit or transfer electronic or analog data from one computer node to another. Data is transferred in the form of bits and bytes over a digital or analog medium, and the process enables digital or analog communications and its movement between devices.
The OSI model is a layered framework for the design of network systems that allows communication between all types of computer systems. It consists of seven separate but related layers, each of which defines a part of the process of moving information across a network . An understanding of the fundamentals of the OSI model provides a solid basis for exploring data communications.
1.Physical and Data link layer.
Ø Physical layer which is the 1st layer of OSI model,is responsible for transmitting the data over the different types of physical media .
Ø Data link layer,its function is to primarily prepare packets for transmission over the physical media.It also serves to control the flow of data that will traverse the physical media.
Ø Main functions of Data link layer and physical layer:
· Framing of packets received from the net-work layer.
· Control of how data is handled by the physical media through MAC and detection of errors.
· The type of medium and connectors.
· The data encoding and the control information.
· The types of transmitters and receivers in the network.
2.Network Layer:
Ø The network layer controls the operation of the subnet.The main aim of the layer is to deliever packets from source to destination across multiple links(networks).It also divides the outgoing messages into packets into message for higher levels.
Ø Functions of Network layer:
· It translates logical network address into physical address .Concerned with circuit,message or packet switching.
· Routers and gateways operate in the network layer.Mechanism is provided by network layer for routing the packets to final destination.
· Connection services are provided including network layer flow control,network layer error control,network layer packet control.
· Breaks larger packets into smaller ones.
3.Transport Layer.
Ø The Transport layer is responsible for end to end communication over a network.It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components.
Ø Functions of transport layer:
· Transport layer collects the messages segments for applications and transmit them into network layer.
· It is also responsible for the management of error correction ,providing quality and reliability to end users.
· This layer enables the host to send receive error corrected data ,packets or messages over a neywork and is the network component that allows multiplexing.
· Transport layer can fix any discrepancies in order caused by packet drops or device interruption by reordering them.
4.Application Layer.
Ø The application layer in the highest absraction layer of model that provides the interfaces and the protocols needed by the users.It combines the functionalities of the session layer,the presentation layer.
Ø Functions of application layer.
· It facilitates the user to use the sevices of the network.
· It is used to develop network based application.
· It provides user services like user login,naming network devices ,formatting messages ,e mails ,transfer of files etc.
· It also concerned with error handling and recovery of the message as a whole.
#At sending end:
1.Physical and data link layer:
It receives data from network layer and first divides data into frames and then encodes them to signal and transmit them to medium.
2.Network layer
It accepts data from the transport layer ,divides it into packets,adds addressing information and passes it to data link and physical layer.
3.Transport layer.
It receives data from application layer,divides it into units called segment and sends it to network layer.
4.Application layer.
This layer first enables users to communicate data to the receiver .Data is translated into required language and then adds check points to it called syn bit and then transport data to transport layer.
#At recieveing end:
1.physical and data link layer.
This layer receives the signal from transmission medium and decodes back into data,and this data is converted back into the frames and sends to the network layer.This process is called framing.The main responsibility is hop to hop transmission.
2.Network layer.
At the recieving end the network layer receives the frames send by data link layer and converts them back into the packets ,verifies the physical address(if received address match with own address or not)and send those packets to transport layer.
3.Transport layer.
This layer receives packets from the network layer and converts and arranges into proper sequence of segments and sends it to application layer.
4.Application layer.
Here first check points are removed inserted previously then decompress and decrypts the data as required and translate it back to original and allows access to the senders network.
In this way data is transmitted and received.
