NETWORK ARCHITECTURE

Client-server network architecture

A computer network in which on centralized, powerful computer (called the server) is a hub to which many less powerful personal computer workstations (called clients) are connected. The clients run programs and access data that are stored on the server.

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Client-server network

Peer to peer network architecture

A peer-to-peer network is created when two or more PCs are connected and share resources without going through a separate server computer. A peer-to-peer network can be permanent infrastructure that links a half-dozen computers in a small office over copper wires. Or a peer-to-peer network can be a network on a much grander scale in which special protocols and applications set up direct relationships among users over the internet.

Peer-to-peer

What's the difference between client server and peer-to-peer?

Some people think there is no difference between client server and peer-to-peer networks. Actually there is a huge difference between client server and peer-to-peer. For instance a peer-to-peer network has no central server while client server has. Each workstation on the network shares its files equally with the others. There's no central storage or authentication of users. Conversely, there are separate dedicated servers and clients in a client server network. The server will determine which users can access the files on the network.

Peer-to-peer networks should be installed in homes or in very small businesses where employees interact regularly. There are inexpensive to set up however they offer almost no security. Peer-to-peer are appropriate only for very small businesses or for home use. It also can support about ten workstation before it begins to suffer from some serious performance and management problems. Usually , peer-to-peer network are composed of a collection of clients that run either Windows NT Workstation or Windows 98,Windows 3.11, Windows 95, Windows 2000 Professional also support peer-to-peer networking. On the other hand, client server networks can become as big as you need them to be. Some support millions of users and offer elaborate security measures. As you can imagine, client server networks can become very expensive.The computer that contains the shared resources doesn't check on who's trying to access those resources. Any user can access them as long as the user know the password. If someone happens to write down a password, anyone who finds that password can access the share.

There are an al,ost infinite variety of client server networks, but all of them have a couple of things in common. For one thing, all have centralized security databases that conrol access to shared resources on servers. In the world of Windows, the server usually run NetWare, Windows NT, or one of the Windows 2000 Server products. The server contains a list of usernames and passwords.Users can't log on to the network unless they supply valid usernames and password to the server. Once logged on, users may access only those resources that the network administrator allows them to access. Thus, client server networks posses much more security than peer-to-peer networks.

The primary downside to a client server network is its cost. Servers can become very expensive. For example, you could pay 800 dollar for a copy of Windows NT hardware which mus=ch be more powerful than a standard workstation. Additionally, client server require an employee to manage them. Unless you have someone in your office who's trained in NetWare or Windows NT Server and in all the issues that are involved in client server networking, you'll have to hire someone from outside. And that qualified networking professionals don't come cheap.

ADVANTAGES AND DISADVANTAGES

ADVANTAGES 

1. Easy communication and speed, people can communicate efficiently by using a network such as emails, chat room, etc.
2. Ability to share files, data and information  to maintain their data in an organized manner and facilitate access.
3. Sharing hardware, it can reduce the cost of purchasing hardware.
4. Sharing software, it can reduce the cost of buying software.
5. Security, it can only be accessed by the authorized users.
6. Speed , save time while maintaining the integrity of flies.

DISADVANTAGES 

1. Breakdown and possible loss of resources, it may lead to loss of important data.
2. Expensive to build, for large scale organizations are very pricey especially to buy and replace cables and other hardware.
3. Security threats, there are hackers who are trying to steal valuable data.
4. Bandwidth issues, heavy users who consume a lot more bandwidth will affect other users.

COMMUNICATION DEVICE AND TRANSMISSON MEDIA

COMMUNICATION DEVICE 

Communication device is a communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device.

Types

1. Dial-up modem is a communications device that can covert digital signals to analog signals and analog signals to digital signals, so that data can travel along an analog telephone line. 
2. Digital modem is a communications device that sends and receive data and information to and from a digital line.
3. Wireless modem is a communication that uses the cell phone network to connect to the internet wirelessly from a notebook computer, a smart phone, or other mobile phone.
4. Network card is a communications device that enables a computer or device that does not have built-in networking capability to access a network. 
5. Wireless access point is a central communications device that allows computers and devices to transfer data wirelessly. 
6. Router is a communications device that connects multiple computers or other routers together and transmits data.
7. Hub is a connection device that allows multiple connection to the network. 
8. Switch is a connection device similar to hub but more sophisticated. 

TRANSMISSION MEDIA 

Transmission media is materials or substances capable of carrying one or more signals in a communication channel.

TYPES

Physical transmission media such as fiber optic that uses glass or plastic fiber to carry light signals.Twisted-pair cable consists of one or more twisted-pair wires bundled together.Coaxial cable is a single copper wire surrounded by at least three layers which is an insulating material, a woven or braided metal and a plastic outer coating.

Twisted-pair cable

Wireless transmission media such as microwave that provide a high-speed signal transmission. Communications satellite is a space station that receives microwave signals from an earth-based station.

NETWORK

COMPUTER NETWORK

What is computer network? 

Computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Network are commonly categorized based on their characteristics. 

What is network?

A network is a collection of computers and devices connected together via communications devices and transmission media.