Understanding computer network
Three centuries before now, each characterized by different dominance. The 18th century was dominated by the development of mechanical systems that accompanied the industrial revolution. The 19th century was the age of the steam engine. 20th century, radio technology, tv and computer play a role for collection, information processing and distribution media. The current 21st century or the information-age, where global computer network technology that is able to reach all regions of the world, system development and technology used, Dissemination of information through internet media, the launch of communication satellites and wireless/cellular communication devices marks the beginning of the millennium.
Since the introduction of the internet and the marketing of the Windows 95 operating system by Microsoft Inc., connect multiple computers both personal computers (PC) as well as a server with a network of the LAN type (Local Area Network) to WAN(Wide Area Network) become an easy and ordinary thing. Likewise with the concept of "downsizing" and "lightsizing" which aims to reduce the budget (budget efficiency) especially computer equipment, then the need for a computer network is something that can not be avoided.
1.1 Understanding Computer Networks
A computer network is an "interconnection" between 2 computerautonomous or more, connected with wired or wireless transmission media (wireless).
Autonomous is when one computer does not exercise control over another computer with full access, so it can make another computer, restart, shutdows, file loss or system crash.
In other definitions of networking, autonomous is described as an independent network with its own management system (have own admin), have a network topology, own hardware and software, and connected to other autonomous networks. (The Internet is an example of a very large collection of autonomous networks.)
Two computers are said to be connected if they can exchange data/information with each other, share owned resources, as: file, printer, storage media (hard drive, floppy disk, cd-rom, flash disk, dll). Data in the form of text, audio as well as video, moving through wired or wireless media (wireless) thus allowing computer users in the computer network to exchange files/data with each other, printing on the same printer and using networked hardware/software together
Every computer, printers or peripherals that are connected to the network are called "node”. A computer network consists of at least two or more computer units, can number dozens of computers, thousands or even millions of nodes that are connected to each other.
In a computer network, there is a connection system between nodes (computer), that is:
1.1.1 Peer to peer
Peer means co-worker. Peer-to-peer network is a computer network consisting of several computers, connected directly with a crossover cable or wireless or also with an intermediary hub/switch.
Computers on this peer to peer network usually number in small numbers 1-2 printer. For special use, like a computer lab, research and other things, then this peer to peer model can be developed for connections of more than 10 until 100 computer.
Peer to peer is a model where each PC can use resources on other PCs or provide resources for use by other PCs, No one acts as a server that regulates the communication system and the use of computer resources on the network, in other words each computer can function as a client or server in the same period.
For example, there are several computer units in one department, given the name of the group according to the department concerned. Each computer is assigned an IP address from the same IP class so that they can share with each other to exchange data or resources owned by each computer., like a printer, cdrom, files and more.
Picture 1.1. Peer to peer
1.1.2 Client – Server
Client Server is a network model that uses one or more computers as a server that provides its resources to other computers (client) in the network, the server will configure the resource access mechanism that can be used, as well as communication mechanisms between nodes in the network.
In addition to the local network, This system can also be applied with internet technology. Where is a computer unit) functions as a server that only provides services for other computers, and clients who also only request services from the server. Access is done transparently from the client by logging in first to the destination server.
Clients can only use the resources provided by the server in accordance with the authority granted by the administrator. Applications that run on the client side, could be a resource available on the server. but can only be run after connecting to the server. In the implementation of application software that is installed on the client side, it is different from that used on the server.
Types of Client-Server services include :
vFile Server : provide file management function services.
vPrint Server : provide printing function service.
vDatabase Server : functional processes regarding the database run on this machine and other stations can request service.
vDIP (Document Information Processing) : provide storage function services, data management and retrieval.
Picture 1.2. Model Client-Server
1.1.3 Advantages of peer to peer network
ü Implementation is cheap and easy
ü No special network administration software required
ü Does not require a network administrator
1.1.4 Lack of peer to peer network
ü Network can not be too big (can't enlarge network)
ü Low security level
ü No network management
ü Network computer users must be trained to secure their respective computers
ü The more machines are shared, will affect computer performance
1.1.5 Advantages of client server network
ü Supports better network security
ü Ease of administration when the network gets bigger
ü Centralized network management
ü All data can be stored and backed up centrally in one location
1.1.6 Lack of client server network
ü Need a professional network administrator
ü Need a good device to use as a server computer
ü Need operational software tools to facilitate network management
ü Budget for network management becomes large
ü Bila server down, all data and resources on the server cannot be accessed
1.2 Computer Networks and Distributed Systems
Before computer networks were popular, computer users are familiar with distributed systems. There are things that are quite confusing in the use of the terms computer network and distributed system (distributed system).
The similarity is that both are a collection of computers that are connected to each other with relatively similar transmission media, both have to move files. The more specific differences between Computer Networks and Distribution Systems are as follows:
Table 1.1. Differences in Computer Networks & Distributed System
|COMPUTER NETWORK||DISTRIBUTED SYSTEM|
|KA connected computer is a combination consisting of several workstations or also a combination of server and client computers||Kthe connected computer consists of the host (main computer) and terminals (computer connected to the host computer)|
|Bseveral computers connected to share, however, each job is handled individually by the requesting and requesting computer.Sthe server only serves requests according to the queue that has been set by the system.||Bseveral host computers are connected to be able to do one or more large jobs together.Host serves multiple terminals and performs processing based on input from terminals|
|KThe quality of data communication is influenced by the transmission medium used.LThe safety of a process is influenced by the hardware specifications of each station requesting service.User can find out the ongoing process (on the comp station or on the server).||Kthe quality of data communication is affected by the system.LThe safety of a process depends on the Operating System which will choose which computer processor to use.User cannot find out which processes are going on on the host.|
|Mcommunication method between computers with modelsPeer to Peer orClient Server.||Mcommunication method between computerscentralized(centralized on the main/host computer)|
|Meach node or workstation (on the peer to peer method) does not require a special server computer to handle all the work.Antar nodes can exchange files or resources that are owned, according to the wishes/permissions set by the computer owner.||Meach terminal requires a host (main computer) to be able to actively do work and communicate with other terminals.Alater terminals cannot share files or resources without host intervention (supervisor host).|
|Meach user on each workstation (client) aware of the process that is going on when it requests service or sends data to the server.User secara explicit (real) must "login" on the server, if you want to take advantage of the resources owned by the server. Explicitly conveying the task from afar, explicitly move files, but generally takes care of the entire network management on its own.||Meach user in each terminal cannot be aware of the processes taking place on the systemUser does not need to do the job explicitly, because all processes and management are carried out / handled automatically by the system without the user knowing. Although in general a user on each terminal must also be logged in to be able to take advantage of host resources.|
|Teach user has an identity & a unique password to be able to login and use resources on the server.Ugenerally users can't use the same ID, to login to the server, but the policy of an Admin can change this rule so that an ID can be used together on a limited basis.||Teach user also has an ID and password to be able to login to the host & use the resources provided.Ugenerally multiple terminals can use the same ID to login to the host computer, but system Admin/Supervisor can change by only allowing one ID for each terminal.|
|KThe existence of a number of computers in a network does not have to be transparent in one location, so that physically it cannot be seen by other users on the network.||Kthe existence of one or more autonomous computers or terminals, transparent (clear) for users, usually in a location area.|
|Sserver hardware specifications do not have to be better than client hardware||Spesifikasi hardware host (main computer) must be better than terminal.|
|Mis a system that combines the performance of devices and applications from the physical layer to the application layer||Mis a software system that is created and works at the top layer of a network system.|
The main difference between a computer network and a distributed system lies in the software (especially the operating system) not on the hardware, because it is the software that determines the level of cohesiveness and transparency of the network in question.
1.3 Network History & Internet
1.3.1 Computer network
In the 1950's when the type of computer began to grow until the creation of super computers, then a computer must serve several terminals. (View image 1.4) For this reason, the concept of a time-based process distribution known as TSS was found (Time Sharing System), and for the first time a network is formed (network) computer on the application layer.
In the TSS system several terminals are connected to a host computer. In the process of TSS began to appear a combination of computer technology and telecommunications technology that initially developed on their own.
Picture 1.4. TSS model computer network.In 1957 Advanced Research Projects Agency (BARLEY) formed by the Department of Defense (DoD) USA, 1967 the initial design of the ARPANET was published and the year 1969 DoD held the ARPANET development by conducting research to connect a number of computers to form an organic network (This program is known as the ARPANET).
1.3.2 A Brief History of the Internet and the Web
1957: Advanced Research Projects Agency (BARLEY) formed by the Department of Defense (DoD) USA.
1959: Len Kleinrock wrote a paper on packet switching.
1967: Early designs of the ARPANET published.
1969: DoD rolls out ARPANET development
1970: ARPANET begins to use Network Control Protocol (NCP)
1972: InterNetworking Working Group(INWG) established to promote mutually agreed standards. Specifications of telnet, proposed.
1973: The idea of ethernet is illustrated in Bob Metcalfe's PhD thesis. Specifications for File Transfer, RFC 454, proposed.
1974: The design of TCP/IP is described in detail by Vint Cerf and Bob Kahn in “A Protocol for Packet Network Intercommunication”.
1982: TCP/IP became the protocol for the ARPANET and it was specified by the DoD.
1992: The number of Internet hosts exceeds 1.000.000. Tim Berners Lee invented the editor and browser program. University of Nevada issued Veronica system. A WWW browser called Viola was launched by Pei Wei and distributed with CERN WWW.
1993: NSF created InterNIC to run Internet services such as domain registration. The first version of Mosaic (for the X Window) developed by Marc Andreesen released by NCSA White House online. The National Information Infrastructure Act passed and the United States government began to be more serious in handling the Website.
1994: PizzaHut online, is the first example of a commercial Internet application. Spam mail became a big case after a legal institution called Canter & Siegel sends mail around the world about the service to get a “green card”. First Virtual runs the first "CyberBank". In year 1994 thisYahoo! founded and also the year Netscape Navigator was born 1.0.
1995: Compuserve, America Online, and Prodiy began to provide services for access to the Internet. Marc Andreesen's company, Netscape Communication Corporation, go public and be a number 3 highest price for Initial Public Offering (IPO) share di NASDAQ. NFS no longer frees domain registration. Domain users start paying for a domain that is used and hosted on the internet.
1.4 Aim / Benefits of Computer Network
The benefits of computer networks for users can be grouped into two, that is: for company needs, and network for the public.
The main purpose of building a network in a company is to::
Resource sharingwhich aims to make the entire program, equipment, especially the data can be used by everyone on the network.
Saving Money(Money/budget savings): Shared devices and data will make for considerable budget savings, because there is no need to buy a new device to be installed in each computer unit
High reliability(high reliability): Integrated Office Management Information System or One-Stop Service System with client-server technology, internet and intranet can be applied to computer networks, so that it can provide reliable service, fast and accurate according to needs and expectations.
Benefits of computer networks for the public:
Computer networks will provide different services to users at home compared to services provided to companies. There are three main things that become the attraction of computer networks to individuals, namely::
- access to information located elsewhere (such as access to the latest news, info e-goverment, e-commerce or e-business, everything is up to date).
- person to person communication (like e-mail, chatting, video conferene dll).
- interactive entertainment (like watching tv shows online, radio streaming, download movies or songs, dll).
1.5 Social problems caused by computer networks (internet)
The use of the network by the wider community will cause social problems, ethics, political, and the inevitable economy. The Internet has penetrated all corners of society, everyone can use it regardless of social status, age, also gender.
The use of the internet will not cause problems as long as the subject is limited to technical topics, education or hobbies, also things that are still within the limits of the norms of life, But difficulties begin to arise when a site on the internet has a topic that really attracts people's attention, such as political conflict, religion, sex, dll.
This computer/internet network connection will also cause serious economic problems if the technology is used by certain parties who want to take personal advantage but harm other parties., e.g. carding activities, illegally download commercial software etc.
The pictures posted on internet sites may be something that is common to some people, but very annoying for some people (because it can cause SARA problems).
other than that, the form of messages is not limited to just textual messages. High-resolution color photos and even short video clips can now be easily shared over computer networks.
Some people can be indifferent, but for others the installation of certain materials (e.g. pornography) is something that is unacceptable.
1.6 Network types
In general, computer networks are divided into: 3 network type i.e :
1.6.1 Local Area Network (LAN)
A LAN, is a network bounded by a relatively small area, generally limited by environmental area, like an office in a building, or every room in a school. Usually the distance between nodes is not further than approx. 200 m.
Picture 1.6. Local Area Network (LAN)
1.6.2 Metropolitan Area Network (MAN)
A MAN, usually covers a larger area than LAN, For example, between buildings in an area (regions such as provinces or states). In this case the network connects several small networks into a larger area environment, for example that is: a network of several branch offices of a bank in a big city that are connected to each other.
Picture 1.7. Metropolitan Area Network
1.6.3 Wide Area Network (VAN)
Wide Area Network (VAN) is a network that usually uses wireless media, satellite or fiber optic cable, because of its wider reach, not only covers one city or between cities in an area, but starting to reach the area/territory of another country's authority.
For example, the City Bank office computer network in Indonesia or in other countries, interconnected, ATM Master Card network, Visa Card or Cirrus spread all over the world and others.
Usually WAN is more complicated and very complex when compared to LAN or MAN. Uses many means to connect between LAN and WAN into global communications such as the internet, even so between LANs, MAN and WAN are not much different in some ways, only the scope of the area is different from one another.
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