Computer network
1. Definition
Computer network is a collection of computers, printers and other equipment connected. Information and data moving through cables, allowing network users can exchange documents and data, print on the same printer and with each using hardware / software that is connected with network. Each computer, printer or peripheral is connected to the network nodes. A computer network can have two, tens, thousands or even millions of nodes. A network usually consists of 2 or more computers that interconnected among each other, and sharing resources such as CD-ROM, printer, exchange files, or possible to electronically communicate with each other. Computer is connected, possible contact with the cable media, phone lines, radio waves, satellite, or infrared light.
2. Network Types There are 3 types of Network / Network are:
a. Local Area Network (LAN) / Local Area Network. A LAN is a network that is limited by the relative area small, usually limited by environmental areas such as a office in a building, or a school, and usually not distance of about 1 km square. Some LAN configuration model, a computer is usually on make a file server. Which is used to store software (software) that regulate network activity, or as software that can be used by computer-computer is connected to the network. Computers is connected to the network (network) is usually called with workstations. Usually more workstation capabilities under from the file server and has other applications in the hard drive in addition to the network application. Most LANs use media cable to connect between a computer with a computer another.
b. Metropolitan Area Network (MAN) / metropolitan area network A MAN, usually covering a larger area of the LAN, for example between regions within a province. In this case connects a network of several small networks into a environment larger area, for example as follows: Bank network where several offices of a bank branch in a city big connected to one another. BNI example in the entire region or Ujung Pandang Surabaya.
c. Wide Area Network (WAN) / Large Scale area network Wide Area Networks (WAN) is a network scope typically been using a cable or satellite facility under the sea as an example of the whole network BANK BNI in Indonesia or in other countries. Using WAN facilities, a bank in Bandung can contact the branch office in Hong Kong, only in a few minutes. WAN usually rather complicated and very complex, using many means to connect between LAN and WAN to the Global Communications as the Internet. But however, between LAN, MAN and WAN is not much differ in some respects, only the scope of just a different area one among others.
3. Protocol
Protocol is the main rules governing the communication among several computers on a network, including the rules in which the instructions apply to the ways or methods of accessing a network, physical topology, the types of
cables and data transfer speed. Protocol-known protocol is as follows:
1. Ethernet
2. Local Talk
3. Token Ring
4. FDDI
5. ATM
ETHERNET
Ethernet protocol is by far the most widely used, Ethernet access method called CSMA / CD (Carrier Sense Multiple Access / Collision Detection). This system explains that each attention to the computer from the network cable before sending something into it. If the network there is no activity or a clean computer will transmit data, if there is another transmission in the cable, the computer will wait and will try to re-transmission if the network has been clean. sometimes two computers transmit at the same time, when this happens, each computer will be back and will wait random chance to transmit data back. This method is known with the coalition, and will not affect the transmission speed of network. Ethernet protocols can be used for the network model line straight, Star, or Tree. Data can be transmitted through twisted wire pair, coaxial, or fiber optic cable at speeds of 10 Mbps.
LOCAL TALK
Local Talk is a network protocol that some developed by Apple Computer, Inc.. machines for Macintosh computers. Methods used by Local Talk is a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance). Almost the same as CSMA / CD .. Local Talk adapter and cable Special twisted pair can be used to connect several computers through the serial port. Macintosh Operating System allows connection network peer-to-peer without requiring additional specific applications Local Talk protocol can be used for Straight Line network model, Star, or tree model using twisted pair cables. The most glaring deficiency is the transmission speed. Speed transmission is only 230 Kbps. Token Ring Token protocol developed by IBM in the mid-1980. Access methods through the passing of a token in a circle like Ring. In token ring, the computers are connected one with others like a ring. A token signals move around in a circle (ring) in a network and move from a computer-go to the next computer, if at a stopover in one of There was a computer data to be transmitted, the token will be transported to where it wanted addressed data, the token moves on to another connect between each computer. Token Ring protocol requires a network model with the Stars using twisted pair or fiber optic cable. And can do transmission speed of 4 Mbps or 16 Mbps. In line with the development Ethernet, Token Ring, use less and less until now.
FDDI
Fiber Distributed Data Interface (FDDI) is a network protocol which connects between two or more networks even at great distances . Access method used by FDDI is a token model. FDDI uses two physical ring topology. Usually transmission using one ring, but if there is a problem is found to be automatically use the second ring. A profit of FDDI is speed with using fiber optic cable at speeds of 100 Mbps.
ATM
ATM stands for Asynchronous Transfer Mode (ATM) is a network protocol that transmits at speeds of 155 Mbps or more. Mentranmisikan ATM data into a single package in which the protocol Other transfer in the amount of the package. ATM supports a variation of media such as videos, CD-audio, and pictures. ATM working on Star topology model , By using fiber optic cable or twisted pair cables. ATM in generally used to connect two or more LANs. He also used by Internet Service Providers (ISPs) to increase the speed Internet access for their clients. Conclusions for Protocol: Protocol in use Cable used Speed Transfer Physical Topology Ethernet Twisted Pair, Coaxial, Fiber 10 Mbps Linear Bus, Star, Tree Twisted Pair Fast Ethernet, 100 Mbps Fiber Star Local Talk 0:23 Mbps Twisted Pair Linear Bus or Star Token Ring Twisted Pair 4 Mbps - 16 Mbps Star- Wired Ring 100 Mbps FDDI Fiber Dual Ring ATM Twisted Pair, Fiber Mbps 155- 2488 Linear Bus, Star, Tree
4. Hardware required
Hardware needed to build a network namely computer: Computer, Network Card, Hub, and everything that associated with a network connection such as: printer, CD-ROMs, scanners, Bridges, Routers and other necessary for the transformation process data within the network.
1. File Servers
2. Workstations
3. Network Interface Cards
4. Concentrators / Hubs
5. Repeaters
6. Bridges
7. Routers
File Servers
A file server is the network stout heart, a very fast computer, have a great memory, hard drive has a large capacity, with a fast network cards. Operating systems stored network here, also including some applications and data needed for the networkA file server is in charge of communication and information control among node / component in a network. For example managing the file transfer data base or from a word processor workstation or one node, the node which another, or receive emails at the same time with the task Other seen that the task is very complex file server, he also must keep and share information quickly. So that at least a file server has some characters such as those below:
- Processor minimum 166 megahertz or faster processor again (Pentium Pro, Pentium II, PowerPC).
- A fast hard drive and large capacity, or about 10 GB
- A RAID (Redundant Array of inexpensive Disks).
- a tape to back up your data (for example. DAT, Jaz, Zip, or CD-RW)
- Has a wide network port
- fast network card and Reliability Approximately 32 MB of memory
Workstations
Overall computer connected to the network file server referred to as a workstation. A workstation has a minimum; Cards network, network applications (network software), a cable to connect to the network, typically a workstation do not need floppy because data to be stored and can be placed on the file server. Almost all types of computers can be used as a computer workstation. Network Interface Cards (NICs) or Network Card Network Card (NIC) is a device that provides media to connect between computers, most network cards are cards inernal, ie a network card installed in expansion slot inside the computer. Some computers such as MAC computers, using a special box that is attached to a serial port or SCSI port of the computer. In computer there is slot for notebook network card is commonly called PCMCIA slot. A lot of network cards in use today are: network card Ethernet, LocalTalk connectors, and Token Ring network card. Currently popularly used is Ethernet, then followed by a Token Ring, and LocalTalk,
Ethernet Card / Ethernet Network Card
Ethernet network cards are usually purchased separately with a computer, except such as the Macintosh computers that already includes an ethernet network card therein. Ethernet network cards generally have to provide connections for coaxial cable or twisted pair cables, if designed for cable konenektorya is BNC coaxial, and if designed for twisted pair cables it will have a RJ-45 connectors. Some ethernet network cards are also sometimeshave connectors AUI. All were in connect with a coaxial, twisted pair, or with fiber optic cable. Figure Ethernet Network Card From Top to bottom: RJ-45 connectors, connectors AUI, and BNC connectors LocalTalk Connectors / LocalTalk connector LocalTalk is a network card for macintosh computers, this using a special adapter box and cable that is connected to Port for the printer. Lack of LocalTalk than Ethernet is speed of data transfer speed, bi Ethernet computer network is not something new today. Almost in every company there is a computer network to accelerate the flow of information in the perudahaan. Internet start popular today is a giant computer network is a network connected computer networks and can interact with each other. This can occurs because of the development of network technology is very rapid, so that within a few years the number of users of computer networks incorporated in the Internet-fold ganda.asanya can up to 10 Mbps, while LocalTalk can only operate at speeds of 230 Kbps or equal to 0:23 mps Token Ring Cards Token Ring network card looks almost the same as an Ethernet network card. One difference is the type of connectors on the back of the card network, Token Ring type generally have a 9 pin DIN connector that connects Card Cable Network to network.
Hub / concentrator
A concentrator / hub is a device that unites cables network of each workstation, server or other device. In topology Star, twisted pair cable coming from a workstation into the hub. Hub has a lot of slots concentrator which can be installed according to port number of the card to be addressed.
The characteristics of the concentrator is owned by:
- Usually consists of 8, 12, or 24 port RJ-45
- Star / StarUsed in topology
- Usually sold with special application to manage applications manjemen port.
- Commonly called hub
- Usually in pairs on a special shelf, in which there is Bridges, routers
Repeaters
The easiest example is on a LAN using the topology Star using unshielded twisted pair cable. Where known The maximum length for a unshileded twisted pair cable is 100 meters, is to strengthen the signal from the cable dipasanglah a repeater on the network.
Bridges / Bridge
Is a device that divides one network into two fruit tissue, was used to obtain an efficient network, where sometimes very fast network growth hence the need to bridge that. Most Bridges can know each address of each segment next to the computer on the network and also on other networks in the side also. Likened to that Bridges was like a traffic cop set at a crossroads during rush hour. He arranged for information between the two sides of the road network remains well and regularly. Bridges also can be used to connect between networks that use different types of cable or different topologies. The best path to send a message that Based on the address destination and source address. While Bridges can know the address of each computer in each side of the network, routers know the addresses computer, bridges and other
Routers.
router can know the whole network to see which side The most busy and he can pull data from the busy side until side of the net. If a company has a LAN and want to connect to Internet, they have to buy a router. This means that a router can translate information between your LAN and the Internet. This also means find the best alternative path to send data through the Internet.
This means the router is:
- efficiently signal path Set
- Manage messages between the two protocols
- Manage messages between linear bus network topology and Star (star)
- Manage messages passed between Fiber optic cable, cable or koaaksialm twisted pair
5. Topology / Network Forms
Topology of a network based on how to contact a number of nodes or in the form of a central network system. Network topology commonly used are: Mess, Star (Star), Bus, Tree, and the Ring (Ring).
a. mesh network topology
In this topology all centrally connected directly to transmission medium with a configuration called a bus. Transmission signal from a central not drawn simultaneously in two directions. This quite different from what happens in a mesh
b.network topology or stars,
which in both systems of communication can be done interconnection between the central or simultaneously.
c.bus network topology
is not generally used for interconnection between central, but usually used in computer network systems.
d. Network Topology Tree (Tree)
Network topology is referred to as multilevel network topology. This topology is usually used for the interconnection between the central to the different hierarchy. For the lower hierarchy described in location of low and getting up a hierarchy of increasingly high. This type of network topology suitable for network systems computer.
e. Network Topology Ring (Ring)
To form a ring network, each core must be connected series each other and this relationship will form a closed loop. In this system each core must be designed to interact with the adjacent central and far apart. Hence ability to perform switching to the central direction. The advantage of this network topology, among others: the level of complexity Low network (simple), also when there is disruption or damage to the a central flow of traffic can be passed to the other direction in system. The most widely used in computer networks is a bus-type network and the tree (tree), this is for reasons of complexity, ease of installation and maintenance and price to be paid. But only a tree-type network (tree) are recognized reliability because she decided one of the wires on the client, will not affect other client relationship
