Network information system | basic and advance concept of networking and OSI Model of operating system.

What is Computer Network

Computer Network  is used to two or more computer are interconnected to each other to  the communicating data electrically. A network connection can established using either cable or wireless media.  

Information About Computer Network 

• Hardware and software are used to connect computers and tools in any network.
• A Computer network is a system that concepts numerous independent orders to share information and resources.
• The integration of computers and other different devices allows users to communicate more easily.
• A computer  networks interconnected to nodes that can transmit, receive and exchange data, voice and video traffic.
• A computer networks include servers or modems.
• Computer networks enables to the usage and sharing of any number of applications and services, included emails, video, audio and other many more types of data, over the internet.
• Computer networks commonly appear over all the place, such as homes, offices and government administration.

OSI Model of Computer Network System

• OSI stands for open System Interconnection Model.
• It is a reference model that describe how information moves through a physical medium to the software application in another computer.
• It is deals with the connection open system that systems are open for communication with other systems.
• OSI Model was developed by ISO (International Standard Organization) in 1984.
• It is considered as an architecture model for the inter computer communications.   
• OSI Model is consist of seven layers and each layer perform a particular network function.
  

     More Information about OSI Model to click here

OSI Model Seven Layers are given below:

1. Physical Layers

2. Data-Link Layers

3. Network Layers 

4. Transport Layers 

5. Session Layers

6. Presentation Layers 

7. Application Layers

1. Physical Layers:

• It is responsible for the actual physical connection between the devices.
• It define relation between a device and a physical medium.
• This is include the layout of pins, voltages, and cable specifications.
• The main used of application layer is to transmit data in bit form one node to another node.
• It is lowest layer of  the OSI Model.

Functions of a Physical Layer :

1. Line Configuration: 

It is used to how two  or more devices can be interconnected physically.

2. Data Transmission:

 It is used to transmission mode whether it is simplex, half duplex or full-duplex mode between the two devices on the network.

Simplex duplex is used to only send data one device to other device.

Half duplex is used to send and also receive data from one device to other device.

Full duplex is used to send and also receive data simultaneously from one device to other device.

3. Topology:

It is used to way how network devices are arranged.

4. Signal:

It is used to determined the type of the signal used for transmitting the information.

Data-Link Layer :

• The data link layer is responsible for the node-to-node delivery of the message.
• That it makes sure that the message indeed reach the other end without corruption or without signal distortion and noise.
• This layer is used to responsible for the error-free transfer of data frames.
• It is used to provide a reliable and efficient communication between two or more devices.
• It arranges the bits form physical layer into logical chunks of data, known as frames.

It is two sub-layers :

Logical Link Control Layer :

• It is used to responsible for transferring the packets to the network layer of the receiver that is receiving.
• It used Identifier the address of  the network layer protocol from the header.
• It provides flow control.

Media Access Control Layer :

• It is used for transferring the packets over the network.
• it is used to media access control layer is a link between the logical link control layer and the network physical layer.

 

Functions of Data-link Layer :

1. Framing:

It is used to data link layer translate the physical raw bit stream into packets.

The data link layer adds the header and trailer to the frame.

The  header which is  added to the frame contains the hardware destination and source address.

2. Physical Addressing:

When creating frames, the data link layer adds physical addresses of the sender and receiver in the header of each frame.

3. Error Control:

If any error occurs, then the receiver sends the acknowledgment for retransmission of the corrupted frames.

4. Flow Control:

It is used to constant data rate is maintained on both the sides so that no data get corrupted.

5. Access Control:

It is responsible for flow control and multiplexing for transmission medium.

Network Layer :

• It is used to determined the best path to move data from source to the destination based on the network conditions.
• The data link layer is responsible for routing and forwarding the packets from one layer to other layer.
• The network layer works for the Transmission of data from one host to the other located in different networks.
• This network layer provides the functional and procedural means of transferring variable length data sequence from a source to destination one or more networks while maintaining the quality of service requested by the transport layer.
• Routers operate at this layer sending data throughout the extended network and making the internet possible.

Function of Networking Layer :

1. Internetworking:

Internetworking  is the main responsibility of  the network layer.

It provides a logical connection between different devices.

2. Addressing:

Addressing is used to identify the device on the internet.

A network layer adds the source and destination address to the header of the frame.

3. Routing:

Routing is used to determines the best optimal path out of the multiple paths from source to the destination.

4. Packetizing:

A network layer receives the packets from the upper layer and converts them into packets this process is called as packetizing.

Transport Layer:

• The main responsibility of the transport layer is to transfer the data completely.
• Transport layer provides transport transfer of data between end users, providing reliable data transfer while reliability the upper layers of it.
• Transport layer controls the reliability of a given link through flow control, segmentation/de-segmentations, and error control.
•  It breaks the message into packets the reassembles them at the destination.
• It receive the data from upper layer and converts them into smaller units is called as segments.

Two protocol used in this layer:

Transmission Control Protocols:

• It established and maintains a connection between hosts.
• When data is sent over the TCP connection, then the TCP protocol divides the data into smaller units known as segments.
• The transmission control protocol recorders the packets reorders the packets in the correct order at the receiving end.

User Datagram Protocol

• It is an unreliable transport protocol as in the case receiver does not send any acknowledgment when the packet is received, the sender does not wait for any acknowledgment.

Function of Transport Layer :

1. Service-point addressing:

Computer system are run several programs simultaneously due to this reason, the transmission of data from source to the destination not only from one computer to another computer but also from one process to another process.

2. Segmentation and reassembly:

It is used to transport layer receives the message from the upper layer, it divides the message into  multiple segments and each segments is assigned with a sequence number.

3. Connection Control:

Transport layer is provides two services Connection-oriented service and connectionless service.

A connectionless service each segment as a individual packets and they travel in different routes to each destination to source. 

A connection oriented service all packets are travel in a single route.

4. Flow Control:

Transport layer  is perform end to end rather than across a single link.

Transport layer is also responsible for flow control.

5. Error Control:

Error control is performed end-to-end rather than across a single link.

The sender transport layer ensures that message reach at the destination without any error.

 

Session Layer :

• The session layer controls the dialogues connection between computers.
• The session is used to established, maintain and synchronizes the interaction between communicating devices.
• It provides half -duplex or full-duplex operation.
• It is responsible for relation between the end users.
• It is used to naming and addressing to identify a particular user. 

Function of Session Layer:

1. Dialog Control:

Session layer is act as dialog controller that create a dialog between two processes.

2. Synchronization:

Session layer adds some checkpoint when transmitting the data in a sequence Suppose some error occurs in the middle of the transmission of data, then the transaction will take place again form that checkpoints.

Presentation Layer :

• It is mainly used concerned with the syntax and semantic of the information between the two system.
• It is used to translate language used by the application layer.
• The presentation layer transforms the data to provide a standard interface for the application layer.
• This layer is used to operating system converts the data form one presentation format to another format.
• The Presentation layer is also known as the syntax layer.

Function of Presentation Layer:

1. Translation:

It is converts the data from sender-dependent format into a common format and changes the common format into receiver-dependent format at the receiving end.

2. Encryption:

Encryption is called a process of converting the sender-transmitted information into another from and sends the resulting message over the network.

3. Comprehension:

It is used to compressing the data it reduce the number of bits to be transmitted.

Data comprehension is very important in multimedia such as text, audio, video.

Application Layer :

• It also any issues requests to the presentation layer.
• It interfaces directly to the users and perform common application processes.
• This layer provide service to user-defined application processes.
• It is used to handles issues about network transparency, resource allocation, etc.
• It is provides the network services to end users.

Function  of Application layer :

1. File Transfer, access, and management (FTAM):

Application Layer allows a user to access the files in a remote computer, to retrieve the files from a computer and to manage the file in a remote computers.

2. Mail Services:

An application layer provides the facility for email forwarding and storage.

3. Directory Services:

It is used to provide that global information about various objects.

An application provides the distributed database sources.

Define Simple Duplex, Half Duplex, Full duplex

Simple Duplex

Simplex duplex is used to only send data one device to other device. 

Half Duplex 

Half duplex is used to send and also receive data from one device to other device.

 Full Duplex

Full duplex is used to send and also receive data simultaneously from one device to other device.