In order to provide services to the Network Layer, the Data Link Layer must use the service provided to it by the Physical Layer. What the Physical Layer does is, to accept a raw bit stream and attempt to deliver the data to the destination. The bit stream is not guaranteed to be error free. the numbers of bits received may be less than or equal to or more than number of bits were transmitted and they have a different values. It is the task of Data Link Layer to provide the error free transmission of the data. The usual approaches is for the Data Link Layer to break the bit stream up into discrete frames and compute the checksum for each frame. When the frame arrives at the destination the checksum is recomputed. If the newly computed checksum is different from the one contained in the frame, the Data Link Layer knows that an error has occurred and takes the necessary steps to deal with it. [Read more…]

Common uses of internet are:-

(i). Transfer of data

(ii). Remote accessing

(iii). E-mailing

(iv). File sharing

(v). Audio, Video and Graphics

(vi). World Wide Web

(vii). FTP

(viii). Chat

(ix). Telnet

(x). Newsgroup [Read more…]

Some of the network application in different field are as follows:-

1. Marketing and Sales :- Computer networks are used extensively in both marketing and sales organization. Marketing professionals use them to collect, exchange and analyze data relating to customer needs and product development cycles. Sales application include Tele-Shopping, which uses Order-Entry Computers or telephones connected to an order processing networks and online reservation services for hotels, airlines and so on. [Read more…]

For data transmission various methods are used:-

• Synchronous Transmission
• Asynchronous Transmission

Synchronous Transmission

This method of data transmission involves block of characters that are transmitted at regular time sequences. Each of the block of characters is marked with synchronization characters. The receiving end, accepts the data block, till it detects the ending character or after a predefined number of characters are received, indicating end of a message. [Read more…]

The information can be transmitted in either analog form or digital form or both with communication network. Computer generated data is digital whereas the telephone lines carry analog signals. On the basis of data transmission capabilities we can classify the data transmission as follows:-

• Analog Data Transmission
• Digital Data Transmission [Read more…]

Topologies:-is the arrangement of the nodes in a network.There are basic topologies used:

• Mesh
• Star
• Ring
• Tree
• Bus
• Hybrid [Read more…]

INTERNET is a wide term to be explained. INTERNET literary means network of networks i.e, it is the networking of the inter-related computers. There are two different terminologies to be kept in mind, that are:-

(i).INTERNET

(ii).INTRANET

INTERNET deals with WAN and MAN.Where WAN stands for Wide Area Network and MAN stands for Metropolitan Area Network.WAN deals with far flung areas and is also connected with plenty (millions) of people.The server built for this purpose is so strong that it provides subscription to millions of people.WAN helps in connecting different countries.WAN is the slowest one out of three.MAN is limited to the metropolitan cities of a particular country.The perfect example for this is the railways and airways, where two seat numbers are not possible.The database is maintained so that there is no repetition of numbers.This helps users not to get clash between same seat for two people.This data is remotely accessed and also provides it to the other cities.MAN is slower than LAN but faster than WAN.Very famous Ethernet is LAN.

INTERANET deals with the LAN where the network works within a particular organization or any company or any school or college.The LAN is fast as comparison with MAN and WAN.

Earlier internet was used for military purposes, for setting the trajectory of the missiles.ARPANET was first used for military purpose but later on the same was been used for basic purposes.INTERNET had become the basic need for every business and school or college, it has spread his web every where.You have come across so many times with this word “PROTOCOL”, but have you ever thought what is it and what is the use of it?

Well, PROTOCOLs are set of rules to be followed for completing a particular connection.Rules make any two computers to work and share data among each other.Now it comes to the question what will happen if protocols will not be there?The answer will be clear when history of the internet will be told.Earlier every company was using his own internet facilities given by different vendors.This was helpful for the particular company who does share data with any other company, when the issue came for sharing of data companies lacked behind.Then an ISO (International Standard Organization) came up with a superb idea, and that was internet with protocols which are going to be common for every company.This helped a-lot in making the sharing business more reliable as the data was directly transferred from one organization to another.

After this ISO introduced OSI REFERENCE MODEL, which stands for Open System Interconnection.This model consisted of seven layer, that is why it is also known as seven layered architecture model.The layers are as follows:-

(i).Physical Layer

(ii).Data Link Layer

(iii).Network Layer

(iv).Transport Layer

(v).Session Layer

(vi).Presentation Layer

(vii).Application Layer

Physical Layer is the first layer of OSI REFERENCE MODEL.It accepts the data from the other host(computer).It is the only layer which transfers the data to other subsequent layers.

Data Link Layer is the second layer of OSI REFERENCE MODEL.It accepts the data from the physical layer and it makes the data in frames(small parts of the huge data so that it will be transferred to the destination with out any error.Moreover the data transferred has a CRC code for checking the small parts of the data whether they are received at the destination with accuracy or not.

Network Layer is the third layer of OSI REFERENCE MODEL.It is important layer which helps in communication between two host.It actually makes a connection between the two host and helps in data transfer from source to the destination.

Transport Layer is the fourth layer of OSI REFERENCE MODEL.It is responsible for delivering data to the appropriate application process on the host computers. This involves formation of data packets, and adding source and destination port numbers in the header of each Transport Layer data packet.

Session Layer is the fifth layer of OSI REFERENCE MODEL.It provides the mechanism for opening, closing and managing a session(time period) between end-user application processes.

Presentation Layer is the sixth layer of OSI REFERENCE MODEL.This layer is responsible for the delivery and formatting of information to the application layer for further processing or display.

Application Layer is the last, seventh layer of OSI REFERENCE MODEL.This layer is users layer where the application is seen by the user.

After OSI REFERENCE MODEL, TCP/IP was introduced.It was a greater achievement as OSI REFERENCE MODEL is a connection oriented model and TCP/IP is connectionless model.Moreover, the layers introduced were only four in comparison with OSI MODEL.These layers are:-

(i).Link Layer

(ii).Internet Layer

(iii).Transport Layer(host to host Layer)

(iv).Application Layer

Link Layer is the lowest layer of TCP/IP and it results in end to end data transmission without the intervention of the router.

Internet Layer is the second layer after link layer.It helps in transforming the datagrams across the network.It has protocols TCP/IP for making the data reach the destination end, it consists of the IP address of the destination and it also has addressing and routing structures.These structures help in making the data route without any error.

Transport Layer is also called as HOST-TO-HOST Layer.It provides a uniform networking interface for hiding the topology layout of the network connection.It checks out data flow, error correction and congestion control.It helps in maintaining the connection between the host.It has UDP (user datagram protocol) for providing connectionless service.It is not reliable than a connection oriented one’s.It the channel is not dedicated then its obvious that the loss of data can be there.

Application Layer as usual is the users layer and provides the output to the user.It helps in making the user to get communicated to the other host.Here, we have higher level protocols like HTTP(hyper text transfer protocol), FTP(file transfer protocol), SMTP(simple mail transfer protocol).
TCP/IP works on the principle of ACK (acknowledgment), where the data is transferred form source to destination, after data reaches the destination then acknowledgment is send back that the is received

Networking is the connection of the autonomous computers. Networking is needed so as to make a web of the computers. It can be according to the AREAS, i.e. LAN, MAN, and WAN.LAN for Local Area Network, MAN for metropolitans Area Network and Wide Area Networks.

THERE ARE TWO COMMUNICATION MEDIAS IN MAKING A NETWORK:

(i). Guided

(ii). Unguided [Read more…]