COMPUTER NETWORK

Three centuries before now, each marked with a different domination. The 18th century was dominated by the development of a mechanical system that accompanied the industrial revolution. The 19th century is the era of the steam engine. The 20th century, the technology of radio, TV and the computer plays for the collection, processing and distribution of information media. The 21st century is now or age-information, which technology global computer network able to reach all regions of the world, the development of systems and technologies used, the dissemination of information through the internet, the launch of the satellites of communication and communication devices of wireless / cellular marks the beginning of the century millenium.


Since its me-public internet and Windows95 operating systems marketed by Microsoft Inc., to connect multiple computers both personal computers (PCs) and servers with a network of this type of LAN (Local Area Network) to WAN (Wide Area Network) into a thing easy and regular. Similarly, the concept of "downsizing" or "lightsizing" aimed at pressing budget (budget efficiency), particularly computer equipment, the need for a computer network is one thing that can not be inevitable.

1.1 Definition of Computer Networks

The computer network is the "interconnection" between two or more autonomous computer, which is connected with the transmission media cable or wireless (wireless).

Autonomous is if a computer does not control the other computers with full access, so it can make another computer, restart, shutdows, file loss or system damage.

In another autonomous definition of networking is described as an independent network management system itself (has its own admin), has a network topology, hardware and software themselves, and connect with other autonomous networks. (The Internet is an example of a collection of autonomous network is very large.)

Two computer units is said to be connected if they can exchange data / information, share resources owned, such as files, printers, storage media (hard disk, floppy disk, CD-ROM, flash disk, etc.). Data in the form of text, audio or video, move through the media wired or wireless (LAN) that enables computer users in a computer network can exchange files / data, print on the same printer and use a hardware / software connected in a network together

Each computer, printer or peripherals that are connected in a network called a "node". A computer network consists of at least two computer units or more, it can amount to dozens of computers, thousands or even millions of nodes that are connected to each other.

Known computer systems in the network connections between nodes (computers), namely:

1.1.1 Peer to peer

Peer means co-worker. Peer-to-peer network is a computer network consists of several computers, connected directly with a crossover cable or wireless or also with the intermediate hub / switch.

Computers on peer to peer networks have usually amounted to little with the printer 1-2. For special use, such as computer labs, research and some other things, then the peer to peer models can be developed for the connection of more than 10 to 100 computers.

Peer to peer is a model where each PC can use the resource on another PC or give resourcenya to use another PC, No acting as a server that manages communication systems and the use of computer resources that are dijaringan, in other words, any computer can function as a client and a server in the same period.

For example there are several computers in one department, given the name of the group in accordance with the relevant departments. Each computer is assigned an IP address from the same IP class in order to share with each other to exchange data or resource owned by each computer, such as printers, cdrom, file, and others.


Figure 1.1. Peer to peer



1.1.2 Client - Server

Client Server is a network model that uses one or multiple computers as servers that provide their resources to other computers (clients) in the network, the server will govern resource access mechanisms that may be used, as well as the communication mechanism between nodes in the network.

In addition to the local network, the system can also be applied to Internet technology. Where there is a unit of the computer) to function as a server that only provides services to other computers, and the client also simply request a service from a server. Access is done transparently from client to login first to the destination server.

Client can only use server resources that are provided in accordance with the authority granted by the administrator. Applications that run on the client side, it could be a resource that is available on the server. but can only be run after connecting to the server. In the software implementation splikasi the installed client side is different from that used on the server.

Client-Server service types include:

v File Server: providing file management functions.

v Print Server: providing printing function.

v Database Server: the functional processes of the database run on this machine and other stations can request the service.

v DIP (Document Information Processing): providing service functions of storage, management and retrieval of data.


Figure 1.2. Client-Server Model

1.1.3 The advantages of peer to peer network

ü Implementation is cheap and easy

ü Does not require special network administration software

ü Does not require network administrators

1.1.4 Lack of peer to peer network

ü Network can not be too large (can not enlarge the network)

ü Low security level

ü Nothing manage network

ü Computer users must be trained to secure computer networks each

ü The more machines are shared, will affect computer performance

1.1.5 The advantages of client server network

ü Support for better network security

ü Ease of administration when the network grows

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 professional network administrators

ü It took a great device to be used as a server computer

ü Need operational software tool to simplify network management

ü Budget for network management into a large

ü If the server is down, all data and resources can not be accessed in server



1.2 Computer Networks and Distributed Systems

Before the popular computer network, computer user never known a distributed system. There is something quite confusing in the use of the term computer networks and distributed systems (distributed system).

The equation is both a set of computers that are connected to the transmission medium is relatively not much different, both should move the file. More specific differences between Computer Networks and Distribution System as follows:

Table 1.1. Differences in Computer Networks and Distributed Systems

DISTRIBUTED COMPUTER NETWORK SYSTEM
The computers are connected is a combination of several workstations or also combined the server computer and client computers connected consists of a host (main computer) and terminals (computers connected to the host computer)
Some computers connected so that they can share, but each job handled solely by computers that request and asked for service.
The server only serve requests according queues that have been set up the system.

Some host computers connected in order to work on a large or multiple jobs together.
The hosts serve multiple terminals and make the process based on input from terminals

Data communication quality is affected by the transmission medium used.
The duration of a process influenced by the hardware specifications of each station that requested the service.

Users can find out the ongoing process (in comp station or on the server).

Data communication quality is affected by the system.


The length of the process depends on the Operating System that will choose which computer processors to be used.

Users can not figure out the ongoing processes in the host.

Method of communication between computers with the model Peer to Peer or Client Server. Methods of communication between komputertersentralisasi (centered on the main computer / host)
Each node or workstation (the method of peer to peer) does not require a special server computers to handle the entire job.
Between nodes can exchange files or resources owned, as desired / set permissions that the owner of the computer.

Each terminal requires a host (main computer) to be able to actively work and communicate with another terminal.
Inter-terminal can not file or resource sharing with each other without the intervention of the host (host supervisors).

Each user on each workstation (client) are well aware of the current process if he asks for a service or transmit data to server.
Users explicitly (real) must be "logged on" to the server, if you want to utilize the resources owned by the server. Explicitly convey their duties remotely, explicitly move files, but generally handle themselves throughout the network management.

Each user at each terminal may not be aware of the process that takes place on the system


Users do not need to do it explicitly, because all the processes and management carried out / handled automatically by the system without the knowledge of the user. Although in general a user at each terminal must login to take advantage of host resources.

Each user has a unique ID and password to log in and use the resources that are on the server.
Generally, users can not use the same ID to login to the server, but the policy an Admin can change this rule so that an ID can be used together on a limited basis.

Each user also has an ID and password to login to the host and use the resources provided.
Generally, several terminals can use the same ID to login to the host comp, but Admin / Supervisor can change the system only allows one ID for each terminal.

The existence of a number of computers in the network do not have to be transparent in one location, so that physically can not be seen by other users in the network. The existence of a number of computers or terminals or autonomous, transparent (clear) for the user, usually located in an area location.
Server hardware specification should not be better than the hardware specifications of the hardware client hosts (main computer) should be better than the terminal.
Is a system that combines the performance of devices and applications from the physical layer to the application layer is a software system that is created and worked on the top layer of a network system.
The main difference between a computer network and a distributed system lies in the software (especially operating systems) rather than the hardware, because the views by their device that determines the level of integrity and transparency of the network in question.

1.3 History of Network & Internet

1.3.1 Computer Network

In the year 1950 when the types of computers began to swell until the creation of a super computer, a computer must serve some terminals. (See Figure 1.4) For that found the concept of the distribution of time-based process known as TSS (Time Sharing System), and for the first time formed a network (network) computer at the application layer.

In the TSS system of multiple terminals connected to a host computer. TSS began to appear in the process of fusion of computer technology and telecommunications technology that was originally developed independently.



Figure 1.4. TSS models of computer networks.

In 1957 the Advanced Research Projects Agency (ARPA) established by the Department of Defence (DoD) USA 1967 design beginning of ARPANET was published and in 1969 the DoD held ARPANET development by conducting research to connect a computer to form an organic network (the program is known as the ARPANET).


1.3.2 A Brief History of the Internet and Web

1957: Advanced Research Projects Agency (ARPA) established by the Department of Defence (DoD) of USA.

1959: Len Kleinrock wrote a paper on packet switching.

1967: initial design of ARPANET published.

1969: DoD staged development of the ARPANET

1970: ARPANET began using the Network Control Protocol (NCP)

1972: InterNetworking Working Group (INWG) was formed to promote the standard that has been agreed. Specifications of telnet, is proposed.

1973: The idea ethernet described in the PhD thesis of Bob Metcalfe. Specifications for File Transfer, RFC 454, is proposed.

1974: Design of TCP / IP spelled out in detail by Vint Cerf and Bob Kahn in "A Protocol for Packet Network intercommunication".

1982: TCP / IP into the protocol for the ARPANET and is specified by the DoD.

1992: The number of Internet hosts exceeded 1,000,000. Tim Berners Lee to find a program editor and browser. University of Nevada issued Veronica systems. A WWW browser called Viola launched by Pei Wei and distributed with CERN WWW.

1993: NSF made the InterNIC to run Internet services such as registration domain.Versi first of Mosaic (for X Window) developed by Marc Andreesen NCSA released by the White House online. National Information Infrastructure Act passes and the United States government began to be more serious in handling the Website.

1994: PizzaHut online, is the first example of the application komerisal Internet. Spam mail into a big case after a law firm named Canter & Siegel mail to the worldwide spread of service to get a "green card". First Virtual run "CyberBank" first. Yahoo! was founded in the year 1994 and also became the birth of Netscape Navigator 1.0.

1995: CompuServe, America Online, and Prodiy began providing service access keInternet.Perusahaan Marc Andreesen, Netscape Communications Corporation, became public and became the highest number 3 for the price of Initial Public Offericng (IPO) of shares on NASDAQ. NFS is no longer clicking gratiskan domain registration. Domain users begin to pay for a hosted domain that is used and to the internet.

1.4 Purpose / Benefits of Networking

Benefits for users of computer networks can be grouped into two, namely: for the needs of the company and to the public network.

The main purpose of the establishment of a network in a company are:

Resource sharing that aims to make the entire program, the equipment, particularly the data can be used by everyone on the network.

Saving Money (Saving money / budget): Devices and data that can be shared will make substantial budget savings, because it does not need to buy a new device to be installed in each and every computer unit

High reliability (high reliability): Integrated Management Information System Office or One-Stop system with client-server technology, the internet or intranet can be implemented on a computer network, so it can provide services that are reliable, fast and accurate according to the needs and expectations.

The benefits of computer networks to the public:

The computer network will provide different services to users in homes compared to the services provided to the company. There are three main points that form the appeal of individual computers on the network are:

access to information located elsewhere (such as access to the latest news, information e-government, e-commerce or e-business, everything is up to date).
person to person communication (such as e-mail, chat, video Conferene etc.).
interactive entertainment (such as watching TV shows online, radio streaming, downloading movies or songs, etc.).
1.5 social problems arising from Computer Network (Internet)

Network usage by the public at large will cause social problems, ethics, politics, and economy are inevitable. Internet has entered every corner of people's lives, people can use it regardless of social status, age, nor gender.

Internet usage will not cause problems as long as the subject is limited to technical topics, education or hobby, are also things that are still within the norms of life, but trouble began to appear when a website on the Internet has a very interesting topic the attention of people, such as political opposition, religion, sex, etc.

Connection computer network / internet will also pose serious economic problems if the technology is exploited by certain parties-parties who want to take personal advantage but the disadvantage of other parties, such as carding activity, download commercial software illegally etc.

The pictures posted profiles on the Internet pages may be something unusual for sebahagian people, but very annoying for some others (because it can cause problems SARA).

In addition, the form of messages is not limited to textual messages only. Color photos with high resolution and even videoclip singkatpun now can be easily distributed via computer networks.

Some people may be indifferent, but for others the installation of certain material (eg pornography) is something that can not be accepted.

1.6 Types of network

In general, a computer network is divided into three types of networks:

1.6.1 Local Area Network (LAN)

A LAN is a network that is limited by a relatively small area, generally bounded by the area of ​​the environment, such as an office in a building, or each room in a school. Usually the distance between nodes is not farther than 200 m.



Figure 1.6. Local Area Network (LAN)

1.6.2 Metropolitan Area Network (MAN)

A MAN usually covers a larger area than a LAN, for example, between buildings in an area (areas such as provinces or states). In this case the network connecting several small tissue pieces into a larger area of ​​the environment, as an example, namely: a network of several branches of a bank in a major city that is connected with each other.



Figure 1.7. Metropolitan Area Network

1.6.3 Wide Area Network (WAN)

Wide Area Network (WAN) is a network that normally are already using wireless media, means of satellite or fiber-optic cable, because its scope is broader, not just covers one city or between cities within a region, but began to reach the area / region of the authorities of other countries.

For example, a computer network City Bank office in Indonesia or in other countries, interconnected, network ATM Master Card, Visa Card or Cirrus spread throughout the world and others.

WAN is usually more complicated and very complex when compared to LAN and MAN. Use many means to connect between the LAN and the WAN into a global communications such as the internet, however between LAN, MAN and WAN are not much different in some respects, only the scope of its area are different among others.