Peer-to-Peer Networks:
The simplest networks are called peer-to-peer networks. In these networks each client has its own storage area, which might be shared with other clients. There is no central storage in this type of network. Peer-to-peer networks are often used in small classroom computer labs.

Client / Server Networks:
More commonly we see client/server networks. These networks have storage devices on the network that may hold data forusers to share. If you have worked on a client/server network, you have probably heard the term file server used in reference to these storage devices. A client may use the network to connect to one of these storage devices and get some documents to view or edit.

LAN:
The term LAN has become almost synonymous with the word network. A local area network, or LAN, is a network in which all clients share a common infrastructure (wires) and are usually in the same building, or group of buildings.
 

Topology:
The topology defines the shape of a network. Some networks are shaped like rings with all the client stations connected in a logical circle; others are shaped like stars with all the client stations connected to a central point. Probably the most common network topology today is the star as exemplified by 10BaseT networking. This networking scheme draws from many standards including the IEEE 802.3 Ethernet standard and EIA/TIA standards for network cabling.

Protocols:
A protocol is a standard for how devices communicate. Protocols can be broken down into layers. For example, physical protocols specify things like voltage levels on wires, while network protocols might specify how a client might request a re-transmit of some data that it needs. A group of protocols that work together is called a protocol suite. An example of a common protocol suite is TCP/IP, which defines communication on the Internet.

WAN:
In contrast, a wide area network, or WAN, is one that spans a larger geographic area. For instance, a network that links two or more LANs that are separated by some distance might be called a WAN.

A Few Technologies for Networking the WAN:
Plain Old Telephone Service (POTS)
Just as its name implies, this technology relies on standard phone lines to connect schools. Using current analog modem technology, this service can run at speeds up to 28.8 Kbps in each direction. It is a cheap and usually easy way to get a machine connected to the Internet quickly. It has low start-up costs and low monthly rates. If an extra phone line is already available, the school can reuse it with no installation charge. An office can even share the line because it is only connected when it is in use, although this is not recommended. An ISP will need to provide Internet connectivity, but these are usually available at reasonable rates as well.

Leased line
Another type of WAN connection is a leased line. With a leased line, the district buys a permanent connection from the phone company, either
to another school or to an ISP. The district sets up a router and a Channel Service Unit/Digital Service Unit (CSU/DSU) at each school that
will connect and connects the leased line to the CSU/DSU. This establishes a network between the two ends of the
leased line.

Integrated Services Digital Network (ISDN)
ISDN is a technology that is finally becoming available from most telephone companies. It offers connections at either 64 Kbps or 128 Kbps
in each direction. It also expands by multiples of 64 Kbps. The basic service, called a Basic Rate Interface (BRI), contains two 64 Kbps data
lines called B-Channels and a 16 Kbps control line called a D-Channel.

Cable TV
Cable tv is another alternative to the phone company that is emerging. It allows a district to provide WAN connectivity using the cable tv
wiring. Although still a new technology, it promises to offer high speeds and low costs. However, several technical problems need solutions.
These are due to the current implementation of cable tv systems that send the same signal from a central office to many destinations.
 

Fast Ethernet:
This is a new enhancement of Ethernet that runs at speeds of 100 Mbps, ten times the rate of original Ethernet. Known also as
100baseT, it requires that the wiring it runs over be category 5 (cat 5) wiring, a higher quality than the cat 3 used by normal Ethernet. The
equipment needed to use Fast Ethernet is also more expensive than normal Ethernet, and although the prices are dropping, it is most likely too
expensive for schools to install initially. Like 10baseT, it connects as a star topology and has a 100 meter maximum length restriction. This
allows a district using cat 5 wiring to begin with 10baseT and later upgrade to 100baseT without replacing the wiring.