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Saturday, June 25, 2011

INTRODUCTION TO COMPUTER NETWORK (LAN)

INTRODUCTION TO COMPUTER NETWORK (LAN)

INTRODUCTION The computer network is a system that consists of computers and other network devices that work together to achieve a common goal. A computer that is connected in a network will be able to easily exchange data with other computers in the network. The goal of computer networks, among others: 1. Sharing of resources (resource); such as the use of shared memory, hard drive or printer, 2. Communication; such as electronic mail (e-mail), instant messaging and chat. 3. Access to information; such as web browsing.
Each computer, printer and other peripherals are connected in a network of computers called nodes. A computer network can have two, the client (client), while the nodes that provide services referred to as a waiter (server). Network architecture is called client-server, tens, hundreds or even millions of nodes. In order to achieve the objectives of computer networks, each node has a respective function, the node requesting the service (service) is referred to as network applications and is the most widely used today.

History of Computer Networking Before addressing the network even further, before we know the first history of the beginnings of the network. The concept of computer network born in the 1940s in America of a development project in the laboratory computer MODEL I Bell and Harvard University research group led by professor H. Aiken. Initially the project only wanted to use a computer device that must be shared. To do multiple processes without wasting lots of time was made vacant succession process (batch processing), so that multiple programs can be run in a computer with the rules of the queue.
In the 1950's when the types of computers began to swell until the creation of a super computer, a computer must serve multiple nodes. For that discovered the concept of time-based distribution process known as TSS (Time Sharing System), then for the first time a computer network (network) is applied. In the TSS system multiple nodes connected in series to a host computer. In the process of TSS began to appear a mix of computer technology and telecommunications technology that was originally developed independently.



Figure 1. Computer network model of TSS.

Entering the 1970's, when the workload increases and the price of many large computer software began to seem very expensive, then start to use the concept of the distribution process (distributed processing). In this process multiple host computers do a great job in parallel to serve a few nodes that are connected in series in each host computer. In the process of distribution is absolutely necessary in-depth blend of computer and telecommunications technology, because in addition to the process that must be distributed, all the host computer must serve a node-node in a single command from the central computer. 


 
  Figure 2. Computer networks distributed processing model

Furthermore, when the prices of small computers has begun to decline and the concept of the distribution process has matured, the use of computers and networks have started a variety of start dealing with the process and communication between computers (peer to peer) without the central computer. For that start developing a local network technology known as a LAN (Local Area Network). Similarly, when the Internet was introduced, it is mostly a stand-alone LAN started connecting and forming a giant network WAN (Wide Area Network).

Computer Network Topology
The purpose of the computer network is to connect networks that exist in the network so that information can be transferred from one lokawi to another location. Because the company divulging memuliki wants / needs are different so there are many different ways a network can be connected terminals. Geometric structure is called a LAN Topologies (Network Topology).
Network Topology is, things that explains the geometric relationship between the basic elements making up the network node, link and station. Network topology can be divided into two kinds, namely: physical topology (phisycal topology) and topology of logic (logical topology).
There are 6 (six) Network Topology, namely: 1.Star, 2. Mesh, 3. Ring, 4. Bus, 5. Tree, 6. Hybrid.
Each topology has berdeda different characteristics and each also has its advantages and disadvantages. Topology does not depend on the medium. Media used are usually in the form: 1. Twisted pair, 2. Coaxial cable, 3. Optical cable, 4. Wireless.
Physical Topology, is how the cable is held while the Logical Topology, is how the network (network) work on 'physical wiring'. It must be remembered that the logical representation of a topology may be very different from the physical implementation (physical implementation). For example, all workstations in a token ring, is connected in a logical ring. However, physically each station is connected (attached) to the 'central hub', like a star topology.
a. Bus topology or DaisyChain:
This topology has the following characteristics:  

1. Dengankedua connected via a single cable ends closed, nodes are installed along the cable.
2. Kesederhanaandalam customarily used for installation.  
3. The signals pass through cables in duaarah and very likely collision (two mixed data packet).
4. The downside: if either satusegmen wires breaking, then the entire network will stop. 
  Figure 3. Bus Topology

b. Ring topology:  
This topology mempuyai following characteristics:  
1. Form a closed circle yangberisi nodes.  
2. Simple in layout.  
3. The signal flow in satuarah, so it can avoid the occurrence of collisions, thereby allowing rapid data movement and collision detection is much simpler.  
4. The downside: the same sepertikelemahan of bus topology.  
5. Ring topology is usually tidakdibuat physically but realized with a consentrator and looks like a star topology.

  Figure 4. Ring Topology

c.
Star Topology:
This topology has the following characteristics:   

1. Each node communicates directly with the central node, the data traffic flowing from the central node to node and back again.  
2. Easily developed, since each node only has a cable directly connected to the central node.  
3. Advantage: if one cable cut off the other nodes are not disturbed.
4. Can use a cable that "lower grade" because only handle a traffic node, usually using UTP cabling. 
  Figure 5. Star Topology
d. MESH topology:

 
MESH topology constructed by placing a link between node-node. A 'fully-connected mesh' is a network where each node is connected directly to all other nodes. Usually used on a small computer network. This topology is theoretically possible but not practical and the costs high enough to be implemented. Mesh topology has a high level of redundancy. So if there is a link that is broken then a node can find another link. \ 


  Figure 6. MESH topology

e. Topology TREE:

 
Tree topology was built by a bus network which is connected secra together. Example: every building within a campus has a bus network that has been installed, then every network can be connected together to form a technology tree that can cover all campuses. Because the tree topology bus topology consists of a connected secra with the tree topology has the same characteristics with the bus topology.
f. Hybrid:

 
Hybrid Network is a network formed from a variety of topologies and technologies. A hybrid network may, as a sample, caused by a takeover of a company. So when combined the different technologies must be combined in a single network. A hybrid network has all the characteristics of the topology contained in the network.
 

BRIEF INTRODUCTION TO COMPUTER NETWORKS LOCAL AREA NETWORK (LAN) 

 If you work on computers that are not connected to another computer then it can be said you work in Stand Alone. If the computer where you work associated with computers and other equipment to form a group, then it is referred to as a network (Network). As for how kmputer can interact and regulate the existing source system called network (Networking). Now, increasingly popular use of computer networks, many different types of companies have computer networks in some form. Computer networks are classified into two main groups, computer network consisting of multiple computers to hundreds of computers disuatu office or building a local network or the so-called Local Area Network (LAN). Separate LANs can be connected using a particular communication pathway, such as telephone lines. The result is a vast network or a Wide Area Network (WAN).  
ADVANTAGES OF THE USE OF COMPUTER NETWORKS

With the construction of computer network systems in a company will provide benefits - benefits include: 
 • Can share (Sharing) use of existing equipment, be it hard disks, printers, modems, etc., without having to move the equipment to the needy. Thus an increase in time efficiency and cost of purchasing hardware
• Can share (Sharing) the use of files or data on a server or on each - each workstation. Thus, to obtain certain information can be done quickly. In this case an increase in time efficiency.
• Applications can be worn together (multiuser)  
• Access to the network using names, passwords and settings right to confidential data data  
• Communication between users via E-Mail or Lan Conference.
• Control of the users or data usage data centrally, and by certain people  
• System backups are easy because the centralized management 
• It depends on the people who store data (if the person does not exist) because of centralized data storage  
• Data is always up to date because the server was always there to uptodatekan data input (Data Entry) A Supervisor / Administrator can control user based on: access time, site access, the use of hard drive capacity, Detecting unauthorized users, monitor the work of each user. At this time with the development of software technology, it allows the use of the Internet together simultaneously, although only have one modem, one phone line and one Internet account. 



  Examples of computer network applications:  
- Client C, Client E was a print document to a printer on the Client A
- Client F is a print document to a printer on the Client B
- Client A, B, C, D, E, F can communicate with each other. 
- Client G access data on your office server from home.
- Internet on Client D is active, Client A, B, C, E and F can use the Internet facilities available on Client D simultaneously / concurrently.  
- Modem on Client D can function as a Fax Machine, Client A, B, C, E, F can use the facility, Using Fax on modem facilities will save money because they are unnecessary printing of documents on paper, but directly in the send to fax number be addressed, the document you are reading is one example of the results. 
 - General data can be used together - Data is confidential data protected so that only certain people can access - Access to the other gets determined by the supervisor or system administrator - Data of each user can be accessed / edited if the permission of the creator of the data or supervisor / system administrator 

 EQUIPMENT - EQUIPMENT REQUIREMENTS HARDWARE:  

1. One (1) Unit for Server computer.  
2. Approximately 8 Units kompuuntuk computer as a workstation or client  
3. Swich'Hub 8 Port 10/100 Mbps, For a network consisting of a Server and Client 7.  
4. 100 Mbps Ethernet Card, for each computer needs an Ethernet Card.  
5. RJ 45 jack, for each computer takes 2 PCS Jack RJ 45.  
6. UTP cable, length depending on the needs at the time of installation.  
7. 56Kbps modem if you want to subscribe to the internet as a dial-up Leased Line or ADSL model if you want to subscribe to ADSL  
8. Line Number.  
9. UPS. 

SOFTWARE:

Microsoft ® Windows 7, Windows XP Professional, Windows XP Home Edition, Windows 2000, Windows Me, Windos 98, Windows 95, Windows NT, Lynux to the Client Operating System.

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