Networks And Connectivity Essay, Research Paper
Networks and Connectivity ByGeorge Vagenas Trying to give a definition to the term COMMUNICATIONS we can say that Communications is the dispatch of a message from one point to another and the confirmation of the complete , right and conceivable receiving of the message by the authorized addressee . As we can see from the history there was a huge try to achieve the communication between people . The signals of smoke , the sounds of the drum , the fire were some of the basic ways for the transfer of a message in a era years ago . But these ways of communication was neither accurate nor has the certainty of the success . Also the transfer speed of the information was small , the size of the information tiny and the security of the communication was almost absence . The need for networks appears for the first time when Graham Bell set in use the telephone . He was talking with a friend of his with a single line , but later when he wanted to talk to another friend of his he needed to use another line to connect his phone and the phone of his friend . So imagine that he has X friends , he would need X(X-1)/2 lines and X-1 phones , that was impossible so the need of networks come up . The network first developed for the need of the voice communication but after the appearance of data communications need the same network was used . From the time that electricity and electronics had developed there was rapidly changes at the section of the communications . After the decade of the 1950 the computers started developing , and the communications started playing an important role in peoples life . Also the evolution of the voice communication has created an extensive telephone network which today covers a very large part of the planet , and computers have taken advantage of that network in a great rate so as to satisfy their needs for data communication . Terms Talking about our days , when we are referring to the term computer connectivity we have a complex of hardware , software and physical appliance, and we mean the way and how computers can communicate and share common sources with the use of an intelligent or common network . With the term Data Communication we mean the exchange of information under the form of data between Data Terminal Equipment . These information are data which compose from characters such as the letters of the alphabet , numbers , punctuation marks and other symbols . We have to define some key terms for better understanding of our subject. Information at the communications we mean every organized signal , whereas when we say data we mean the notation which represent the coded form of the information with the use of letters or symbols . The encoding happens with a specific way (usually digital) in order to make the information proper for process , storing or transfer . With the concept Data Transmission we determine the transfer of the information within physical appliance . By the evolution of the computers the Data Terminal Equipment reach the point to have enough process power to maintain a part of the application or a part of the data base . This architecture is the CLIENT / SERVER . It is useful to examine some computing environments , so we have single-user , multi-user and client / server computing . When we say single-user environment we usually referring in a network that has PC for Data Terminal Equipment . As the name says , they are the systems that allow access to one user each time . All the applications and the peripherals that the network offers can be available in only one user each time . The restrictions that the single-user environment set, we are trying to skip them with the multi-user environment . The multi-user systems share their abilities between the users with techniques which we characterize them as time sharing . In these environments we use dump terminals , one monitor and one keyboard . In a client / server computing environment every Data Terminal Equipment is a PC and the environment works like the multi-user environment . So every user with his own PC shares with the others the applications , and the peripherals that the network provides like printers , streamer, hard disks etc. Trying to compare this three environments we are going to see an example of how we can run an application in each environment . In a single-user system we load the application on the RAM of our PC and we execute it , from now on the CPU is occupied with this application only . At a multi-user environment the RAM is shared to many users while the CPU dedicates one percentage of the whole power to this application cause it has to serve and the other users . In contrast , in a client / server environment we load the application in our PC ( client ) from the file server and we execute and process it on our PC . Every time the application needs some data asks it from the server and then it processes It . LAN – WAN With the convenience that the modern telecommunications gives , every user has the ability to use the power of a workstation through Data Terminal Equipment . By now the Data Terminal Equipment aren t restricted to be in the same place with the workstation, but they can be installed in different places , different cities or even in different countries . So we have two different type of data communications which we distinguish them with the factor of the distance between the Data Terminal Equipment which are going to be connected . The LAN ( Local Area Network )and the WAN ( Wide Area Network ) . The only difference between LAN and WAN is the physical appliance that we use to connect the main computer with the nodes . So we are going to talk for the LAN which is most famous these days . Local Area Networks , are the networks that consist from a number of Data Terminal Equipment (nodes ) and exist in a restricted geographical area .
The basic elements that a LAN consist are these :Ø The physical appliance and the communication devices .Ø The D