Network Environments

A network as a series of points or nodes connected by communications channels. Each node may be a computer or a dumb terminal. There are two types of network distinguished by the distances separating nodes and called LAN and WAN networks.

LAN Networks

Local Area Networks are installed within a single room, building or site normally connecting PC's together although they may include a mini computer. There are two methods used for providing LAN networks.

Firstly there is the peer to peer LAN. Here the computers are connected to each other. There is no central storage, but each user will store his or her own work on the local hard disk. Files and software on other users' computers will be available through the network but access to files on other computers will normally be dependent on the other user granting access privileges to other users. Similarly hardware devices attached to other computers will also be generally available. This type of network is less structured than the server-based LAN and it therefore entails fewer maintenance overheads. However each user will be responsible for his or her own local disk, including backing up.

There are two types of server based networks. A print server and a file server. A file server-based network has a central file-server which may store central copies of both software and data files. Each user will be allocated disk space on the server (like your P: drives) and access will be controlled by use of log in names and passwords. This type of system is more dependent on the connection to the server being maintained. Cable failure or server crash disrupts the network and users may not be able to use their workstation at all - especially if software has been installed on the server rather than on the local hard disk.

In addition to a file server, this type of network will often have one or more print servers which will manage print jobs. Network printout would be spooled to the server disk to be despooled by the appropriate printer server. This approach allows a number of users to apparently access a single printer at the same time. A print server was (is) a computer attached to a printer that is used by several machines. This is uncommon now printer-sharing devices can be attached directly to the network.

A sever based network is more complex to set up than a peer to peer network and it needs a network manager to set up users, grant access rights and allocate space on the server as well as install software on both the server and the workstations. Control and consequently security is therefore easier to maintain. Since users' data is stored centrally on the server, a proper backup strategy for the server will ensure that all data is safely backed up without relying on individual users remembering or bothering to back up their own data files.

A principal advantage of having either type of LAN is the ability to share printing and other peripherals - such as scanners and the facility to send and receive messages using the network. Cable may be fibre optic or simple twisted pair. Data usually transmitted digitally as pulses. This limits the length of cable that can be used.

WAN Networks

Wider Area Networks link computers - usually including mainframes, PC's and dumb terminals situated on different sites. These may be in different towns, countries or continents either using public telephone links or a dedicated landline to communicate data. If the link is electrical then a modem will be needed at each node. Electric cabling is now being replaced by fibre optic that can transmit digital data directly so that a modem is not required. In addition a single fibre optic cable can carry a large number of different transmissions simultaneously and it is not subject to the electrical interference associated with wire transmissions.

The differences betwqeen LAN and WAN

Advantages and Disadvantages of Networking

The following are some of the advantages of networking:

• Expensive hardware resources can be shared - e.g. expensive colour printer
• Only one copy of important data files required. Accessed by all and changes apparent to all users as they happen.
• Access to data can be centrally controlled.
• Electronic communication possible. Mail/messaging systems.

There are however some disadvantages

• It may not be possible to do anything at a local station if the network is down.
• A virus introduced at a single machine may quickly spread to all network stations.
• Users may suffer unacceptable delays when the network is busy.
• A network station can only be used where there is a network connection available.

Obviously these can be looked at from a different point of view to arrive at advantages and disadvantages for a stand alone system.

Additional Information:

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