USING INFORMATION

Network Strategies

Topologies

A network topology is basically the way in which the network has been built.  Although there are several different variations on each of these basic topologies we are only going to look at the generic types.

LAN

lan

This stands for Local Area Network and it is a network that is restricted to one room, building or site. The cabling and hardware (infrastructure) that defines the network are usually owned by the organisation.  LANs allow users to share data and peripherals like printers, often they are able to log on anywhere on the network and access their own data from any computer.  The network manager is able to control access through the use of usernames and passwords and ensure that data is kept secure and backups made.

wan

This stands for Wide Area Network and is a network that uses some form of external communications for computers to communicate with each other.  Some large companies, local authorities and government departments operate WANs.  Their regional and district offices can be connected via leased lines and their computers will all operate as if they were workstations on a LAN. More common nowadays is for these organisations to use telephone lines and run a web-based service or Intranet.  By far the biggest WAN in the world is the World Wide Web running the Internet.

Distributed networks

Distributed networks have been made possible on LANs by the use of modern networking software and by having multiple servers around the network.  Each server can run a mini network within a sub-group of switches and this can reduce network traffic significantly.  Users’ data can be kept on the server they are most likely to access although their user area should be transparent from any station on the network.  A distributed network can make the working of a network like a school or college much more efficient, and in a business environment much more secure as well. Server failure at one node is unlikely to render the entire network useless

Network hardware

Client-server network

client server

This type of network has a central computer called a server, although large LANs may have more than one server. Data files and software are usually stored on the server but can be accessed from the network stations (nodes). Some software is installed centrally so that it only has to be installed once, although applications are usually installed on each workstation and this software can often be installed remotely to several stations at once. All files are stored centrally, providing a pool of data that is accessible to all workstations on the network. The network can support computers of differing types and usually different versions of the same operating system. Backup is easy to perform and there is no need to rely on users backing up their own files.

This sort of network is heavily dependent on the server. Servers need to have fast processing speeds, large memory and large hard disks. They are expensive and server-based networks are complicated to install.  The commonest type of server-based LAN is based on Ethernet technology.

Peer-to-peer network

peer to peer

This type of network has no central server, as all workstations on the network are equal. Installing software takes more time, as it has to be installed on each computer. Workstations on a peer-to-peer network can access work stored on other computers on the network. This type of network is less secure as access to and from workstations needs to be open.

As a server is very expensive to buy, a small peer-to-peer network is a lot cheaper then a client-server network. A peer-to-peer network is ideal in a small office where a handful of computers need to be networked.

Network adapter card

Every computer attached to a network needs a network adapter card. Very often now the card is built-in to the computer at the time of manufacture. The network cable plugs into the card and the other end into a socket and it therefore allows the computer to send and receive data across the network.

Structured cabling

Cables are the commonest form of transmission media used to build a network. They are usually made from copper wire, such as co-axial and twisted pair. Fibre-optic cables are also used for fast, large-capacity networks or to connect sections of a network in a large building like a school or college.

In an Ethernet network, twisted pair cabling is normally used, and each network point will be connected back to a hub or switch, which in turn is connected to the server.  However large a network becomes (and networks of 200–500 stations are not uncommon in large schools and colleges) this simple structure applies.  Of course complications develop and when longish distances are covered a repeater boosts the signal, at regular intervals to prevent the signal deteriorating until it is unusable.

Network software

Network operating system

There are two parts to the network operating system, the version that runs on the server and the version that runs on the personal computers to turn them into network stations. The server software is needed to control which users and workstations can access the server, keep each user’s data secure, and control the flow of information around the network. It is also responsible for file and data sharing, communications between users, and hardware and peripheral sharing.

Each workstation (computer) connected to the network needs the Network Operating System installed before it can connect successfully to the network facilities. It may be extra software added to the operating system, or more likely on modern computers running Windows 2000 or XP it comes as part of the operating system and only needs to be run to connect the computer to the network.  Thereafter it runs automatically after start-up and makes any user log in before they can access either the computer or the network

Network auditing and monitoring software

This software keeps a track of network activity. It not only records user activity, but workstation activity as well. It records who has logged in where, at what time, for what duration, which applications have been used, printer requests and file access activity.  This allows the network manager to see exactly what was happening if a problem is reported, and also to monitor any person who may be acting suspiciously as far as the network is concerned.

In a commercial organisation this sort of auditing and monitoring can be used to detect fraud and suspicious activity.

 



 

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