Computer network - what is computer networks

 

Computer network - what is computer networks



Introduction to Computer Networks

Today the planet scenario is changing. digital communication and network have changed the way business and other daily affair works. Now, they depend on computer networks and internetwork. a collection of devices often mentioned as nodes connected by media link is called a Network. A node is a tool which is capable of sending or receiving data generated by other nodes on the network sort of a computer, printer etc. These links connecting the devices are called Communication channels.


A network may be a group of computers (or a bunch of smaller networks) that are connected to every other by various means, in order that they'll communicate with each other. the net is that the largest network within the world.


A network must be able to meet certain criteria, these are mentioned below:

1. Performance

2. Reliability

3. Scalability



Performance -

It may be measured in following ways :

  • Transit time : it's the time taken to travel a message from one device to a different.
  • reaction time : it's defined because the time elapsed between enquiry and response.


Other ways to live performance are :

1. Efficiency of software

2. Number of users

3. Capability of connected hardware



Reliability -

It decides the frequency at which network failure happen. More the failures are, less is the network's reliability.


Security -

It refers to the protection of information from the unauthorised use or access. While travelling

through network, data passes many layers of network, and data are often traced if

attempted. Hence security is additionally a really important characteristic for Networks.


Network Services

Computer systems and computerized systems help persons to figure efficiently and explore the unthinkable. When these devices are connected together to create a network, the capabilities are enhanced multiple-times. Some basic services computer network offers are.


1. Directory Services

A directory service could be a customizable information store that functions as one point from which users can locate resources and services distributed throughout the network.


  • Accounting

In a company, variety of users have their user names and passwords mapped to them. Directory Services provide means of storing this information in cryptic form and make available when requested.


  • Authentication and Authorization

User credentials are checked to authenticate a user at the time of login and/or periodically. User accounts may be set into hierarchical data structure and their access to resources will be controlled using authorization schemes.


  • Domain name Services

Network operates with the assistance of IP addresses and humans tend to recollect website names, the DNS provides website’s IP address which is mapped to its name from the back-end on the request of an internet site name from the user.



2. File Services

File services include sharing and transferring files over the network.


  • File Sharing

One of the explanation which gave birth to networking was file sharing. File sharing enables its users to share their data with other users. User can upload the file to a specific server, which is accessible by all intended users. As an alternate, user can make its file shared on its own computer and provides access to intended users.


  • File Transfer

This is an activity to repeat or move file from one computer to a different computer or to multiple computers, with help of underlying network. Network enables its user to locate other users within the network and transfers files.


3. Communication Services

  • Email

This is the idea of today’s internet features. Email system has one or more email servers. All its users are supplied with unique IDs. When a user sends email to other user, it's actually transferred between users with help of email server.

  • Social Networking

Recent technologies have made technical life social. the pc savvy peoples, can find other known peoples or friends, can connect with them, and may share thoughts, pictures, and videos.

  • Internet Chat

Internet chat provides instant text transfer services between two hosts. Two or more people can communicate with one another using text based Internet Relay Chat services. These days, voice chat and video chat are quite common.

  • Discussion Boards

Discussion boards provide a mechanism to attach multiple peoples with same interests.It enables the users to place queries, questions, suggestions etc. which can be seen by all other users. Other may respond likewise.

  • Remote Access

This service enables user to access the info residing on the remote computer. This feature is understood as Remote desktop. this will be done via some remote device, e.g. mobile or data processor.


4. Application Services

These are nothing but providing network based applications to the users like web services, database managing, and resource sharing.

  • Resource Sharing

To use resources efficiently and economically, network provides a mean to share them. this could include Servers, Printers, and Storage Media etc.

  • Databases

This application service is one amongst the foremost important services. It stores data and information, processes it, and enables the users to retrieve it efficiently by using queries.

  • Web Services

World Wide Web has become the synonym for internet.It is wont to connect with the internet, and access files and data services provided by the net servers.


5. Security Services

Network security can provide the subsequent services associated with a message and entity.

1. Message confidentiality

• It means the content of a message when transmitted across a network must remain confidential, i.e. only the intended receiver and nobody else should be ready to read the message.

• The users; therefore, want to encrypt the message they send so an intruder on the network won't be able to read the contents of the message.


2. Message Integrity

• It means the information must reach the destination with none alteration i.e. exactly because it was sent.

• There must be no changes during transmission, neither accidentally nor maliciously.

• Integrity of a message is ensured by attaching a checksum to the message.

• The algorithm for generating the checksum ensures that an intruder cannot alter the checksum or the message.

3. Message Authentication

• In message authentication the receiver must take care of the sender's identity i.e.the receiver must ensure that the particular sender is that the same as claimed to be.

• There are different methods to test the genuineness of the sender :


1. the 2 parties share a typical cipher word. a celebration is required to point out the secret code word to the opposite for authentication.

2. Authentication is done by sending digital signature.

3. A trusted third party verifies the authenticity. One such way is to use digital certificates issued by a recognized certification authority.


4. Message non-reproduction

• Non-repudiation implies that a sender must not be ready to deny sending a message that it actually sent.

• The burden of proof falls on the receiver.

• Non-reproduction isn't only in respect of the ownership of the message; the receiver must prove that the contents of the message also are the identical because the sender sent.

• Non-repudiation is achieved by authentication and integrity mechanisms.


5. Entity Authentication

• In entity authentication (or user identification) the entity or user is verified before access to the system resources.


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