Goal sofComput erNet wor k Right from the day of computer automation, a computer has developed computer in each department. For example, the task can be to keep of track off inventories, monitor productivity and maintain accounts. Initially, this computer in different department works as an isolation from other computer. These provided the the necessary necessary computer computer assistance in the activities activities pertaining pertaining to the respective department. It was not possible to share information among the departments. As a result, the information was replicated wherever needed. This increased redundancy caused increased in storage space, less data consistency etc. ence, at a point it was decided to connect the computers in various departments to extract the information and correlate information about the entire company. The following are the ob!ectives of the computer networks. 1. Resource sharing is the main ob!ective of the computer network. The goal is
to provide all the program, date and hardware is available to everyone on the network without regard to the physical location of the resource and the users. 2. The second ob!ective is to provide the high Reliability. It is achieved by
replicating the files on two or more machines, so in case of unavailability "due to fail of hardware# the other copies can be used. 3. $omputer organi%ation has helped organi%ation in saving money. This is due
to the fact that the small computer has much better price to the performance ratio comparison than the large computer like mainframe. &ainframe computer
are approximately ten times faster that the microcomputers, but they cost thousands times more. As a result of this imbalance, organi%ation has preferred to install interconnected microcomputer connected to the mainframe computer. 4. $omputer network have provided means to increase system performance as
the work load increases "load balancing#. In the days of mainframe when the system was full it was to replace with the other large mainframe computer, usually at and expensive rate not convenience for user. 5. $omputer network help people who live or work apart to report together. 'o,
when one user prepared some documentation, he can make the document online enabling other to read and convey their opinions. Thus computer network is a powerful communication medium. 6. (nly authori%ed user can access resource in a computer network. )sers are
authenticated by their user name and password. ence it is not possible to access the data without proper account. This increases security.
Appl i cat i onofNet wor k s: *. Marketing and sales + &arketing professional uses them to collect exchange and analy%e data relating to customer needs and product development cycles. 'ales application includes Teleshopping, which uses order entry computers or telephone connected to an order processing network, and online reservation services for railways, hotels, airlines, restaurants theatre etc.
. Financial services + It include credit history searches, foreign exchange and investment services and electronic fund transfer "-FT#, which allow a user to transfer money without going to bank. . Manufacturing + computer networks are used today in many aspects of manufacturing, including the manufacturing processes itself. Two aspects that uses network to provide essential services are computer Assisted design "$A/# and computer Assisted manufacturing "$A&#, both of which allow multiple user to work on a pro!ect simultaneously. 0. Electronic Messaging + -1mails transfer the messages between two and more users in a network. 2ith this application user can transfer the information in the form of text, picture and voice. 3. Directory Services + It allows list of files to be stored in central location to speed up the world wide search operation. -.g. search engines like 4oogle, 5ritannia, and 6ahoo etc. 7. Inforation Services + It includes 5ulletin 5oards and data bank. A 8www9 site offering the technical specification for a new product in a information services. :. Electronic Data E!c"ange #EDI$ + -/I allows business information "including documents such as purchase orders and services# to be transferred without using paper. ;. %eleconferencing+ It allows conference to occur without the participant being in the same location. It includes+
%e!t &onferencing +
computer monitors. 'oice &onferencing +
simultaneously through phone "talk#. 'ideo &onferencing +
=. &ellular %ele("one + 2ireless phone communication even while travelling through long distance. *>. &a)le %'+ This is widest usable thing today throughout the world.
Network Architecture Types Network architectures are sometimes classified into two broad categories: · client-server architectures, · peer-to-peer architectures. In the client-server architectural model, a system is decomposed into client and server processors or processes. Servers provide computational resources or services!, which clients consume. "ypically a server provides services to many clients. It is also common for clients to consume services from multiple services. Stated otherwise, there is generally a #:$ relationship between a server and its
clients, and it is sometimes the case that there is a #:$ relationship between a client and the servers that it uses. "he client-server architectural model supports the separation of functionality based on the service concept. %lient-server architectures are commonly organi&ed into layers referred to as 'tiers(. Tiered Architectures
· "wo-tier architectures. "he system architecture consists of a data server layer and an application client layer. )ata access computation is associated with the data server layer, and the user interface is associated with the client application layer. If most of the application logic is associated with the client application logic, it is sometimes referred to as a 'fat client.( If it is associated with the data access server, the application client layer is sometimes referred to as a 'thin client.( · "hree-tier architecture. "he system architecture consists of data server layer, an application server layer and a client application layer. "he application server layer facilitates the separation of application logic from presentation, and promotes distributed processing. · $ulti-tier architecture. "he system architecture is a superset of a three-tier architecture, and includes additional layers for data and*or application servers.
Peer-to-Peer Architectures
In a peer-to-peer architecture model, a system is decomposed into computational nodes that have e+uivalent capabilities and responsibilities. "his division is in contrast to a client-server architectural model, where client and server nodes are divided into server and client roles. n eample of a peer-to-peer architecture is a system of intelligent agents that collaborate to collect, filter, and correlate information.
Sometimes layered 'tiered(! and peer-to-peer architectures are combined, where the nodes in particular layers are in peer-to-peer relationships. or eample, a multi-tiered architecture might include an enterprise management layer, consisting of peer nodes for such things as network m anagement, event management, database management, /eb sever management, and workload balancing.
