Types of Networks

LAN
Local Area Networks or LANs are a network of computers that span a relatively small space. Most LANs are in an office or home, connecting a series of PCs together. Each computer on the network is called a node, has its own hardware and runs its own programs like any normal PC, but they can also access any other data or devices connected to the LAN. Printers, modems and other devices can also be separate nodes on a LAN.

ETHERNET
Ethernet is a type of LAN. It is more or less a LAN protocol developed by Xerox Corporation in 1976.   The original supported transfer rates of 10 Mbps. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps.

WAN
Wide Area Network or WAN is a network that spans a larger area. It consists of two or more LANs connected to each other via telephone lines or some other means of connection.

INTERNET
The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups. With the meteoric rise in demand for connectivity, the Internet has become a communications highway for millions of users.

TOKEN RING
An older, archaic form of network configuration which differs from Ethernet in that all messages are transferred in a unidirectional manner along the ring at all times. Data is transmitted in tokens, which are passed along the ring and viewed by each device. When a device sees a message addressed to it, that device copies the message and then marks that message as being read. As the message makes its way along the ring, it eventually gets back to the sender who now notes that the message was received by the intended device. The sender can then remove the message and free that token for use by others.

Protocols
A common set of rules and signals the computers on the network use to communicate. There are many protocols, here are some common ones:

• TCP/IP : Transmission Control Protocol / Internet Protocol. This was originally developed by the Defense Department of the US to allow dissimilar computers to talk. Today, as many of us know, this protocol is used as the basis for the internet. Because it must span such large distances and cross multiple, smaller networks, TCP/IP is a routable protocol, meaning it can send data through a router on its way to its destination. In the long run, this slows things down a little, but this ability makes it very flexible for large networks.

• IPX/SPX: Developed by Novell for use with its NetWare NOS, but Microsoft built compatibility into both NT and Windows 9x. IPX is like an optimized TCP/IP. It, too, is a routable protocol, making it handy for large networks, but it allows quicker access over the network than TCP/IP. The downfall is that it doesn’t work well over analog phone lines. IPX continually checks the status of transmission to be sure all the data arrives. This requires extra bandwidth, where analog phone lines don’t have much to begin with. This results in slow access. Of course, the data is more reliable with IPX.

• NetBEUI : Designed for small LANs, this protocol developed by Microsoft is quite fast. It lacks the addressing overhead of TCP/IP and IPX, which means it can only be used on LANs. You cannot access networks via a router.

Architecture
For our discussion, we will examine the two primary types of network architecture:

Peer-to-Peer Network
With this networking configuration, there is no server, and computers simply connect with each other in a workgroup to share files, printers, and Internet access. This is most commonly found in home configurations, and is only practical for workgroups of a dozen or less computers.  

Client/Server Network
Typically, this network consists of one PC designated as the server and other PCs connected to the server using the central data stored on the server.  The server provides more security, preventing the client PCs from accessing one and other.  The server typically can provide access to a central printer and Internet access, (including e-mail), and file sharing,  This is most commonly found in corporate configurations, where network security is essential.