Networks

Networks

The benefits of Networks:

• Software and data can be accessed from any workstation on the network
• Data can be shared (shared areas)
• Users can have their own private work area
• Hardware can be shared (such as printers)
• Software can be shared (it only needs installing once on the network, rather than each workstation separately)
• Users can communicate with each other
• Networks are quite secure

Some disadvantages:

• They can be expensive to set up because often an expensive file server is needed
• If the file server breaks down the whole network is unusable
• Networks can be vulnerable to attacks from hackers
• Usually you need trained staff to maintain the network
• Performance can be slow if there are too many users all working on the network at once

WANs (Wide Area Networks)

A Wide Area Network (WAN) is a network that covers a large geographical area (eg Banks operate WANs). Business and government utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations.  The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable.

LANs (Local Area Networks)

A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications.

Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.

HANs (Home Area Networks)

A home network or home area network (HAN) is a residential local area network (LAN) for communication between digital devices in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important function is the sharing of Internet access.




Ethernet Cable

If a network is cabled the type of cable that will be used is an Ethernet Cable. All network cable from every era performs the same function of transporting data from one machine to another. The function of Ethernet cable it to send and receive information.

Wired / Wireless / Powerline Networks

This clip explains the benefits and issues between the different methods of  networking, whether that is Wired; Wireless or Powerline networking methods.

Security

Wireless networks are less secure than cabled networks.  If you do not secure your wireless network then anyone within range can access it (some people use neighbours wireless networks 'illegally' because they have not been password protected).

When you log onto your wireless network at home you often see other 'local' wireless networks like in this example:

You can see in this example that they second one on the list is unsecured!  This means that anyone could use that Internet connection and the person who's connection it is has to cover all the costs!  

Ways to Secure your wireless networks:

• Change the password (do not use the default password)
• Set up some form of encryption  **
• Set up Media Access Control (MAC) address filtering ***
• Hiding the router by stopping it broadcasting its Service Set Identifier (SSID) ****
• Turning off the router when it is not in use
• Reducing the transmitter power

**  Encryption - is where the data is translated into a secret code according to a set of rules in a special 'key'.  To convert the data back into plain text the receiver must also have the same key to be able to decrypt the data and make sense of it.

***  Media Access Control (MAC) -  This is a 12-character address that maps to a physical component such as your broadband router, wireless access card, network card and so on.  Since the MAC address is unique, it can be used as a filtering mechanism to keep devices on or off your wireless network. 

**** Service Set Identifier (SSID) - SSID is a case sensitive, 32 alphanumeric character unique identifier attached to the header of packets sent over a wireless local-area network. The SSID differentiates one WLAN from another

Network Topologies

Network topology is the word used to describe the layout/organisation of a network, the way that they computers and printers are linked together

Bus Topology:  The type of network topology is where all the nodes of the network are connected to a central line. All data transmitted between nodes goes through the central cable.

Advantages:

• Easy to add and remove items (computers)
• Requires a small amount of cable compared to other topologies so is less expensive and easier to setup and troubleshoot.

Disadvantages:

• A failure in the central line means the whole network will go down.
• Only one route for data to take so will performance will decrease as more data is transmitted (as data crashes into each other).

Ring Topology: In a ring topology all the nodes are connected together in a loop. Data is transmitted from node to node in a single direction.

Advantages:

• As all the data can only travel in one direction the transmission of messages is simple and high rates of transmission can be achieved.
• There is no need of a central computer or mainframe.

Disadvantages:

• If a computer or cable fails then data cannot continue to be transmitted between all the rest of the computers in the network.
• Harder to add new computers as it requires the network to be disrupted.

Star Topology: In the star network topology each node is connected directly to a central computer or mainframe.

Advantages:

• It is a more secure connection as data is sent directly between the server and the computer
• A failure of the cable will only affect one computer, this makes faults are easier to pinpoint.
• Easy to add new computers without any disruption

Disadvantages:

• Requires a server.
• Requires more cable and is therefore more expensive to setup.

Client Server Network

With a client server network the files will not be stored on the hard drive of each workstation. You will have a user account and log in using a username and password (like at school!).  When you log on like this, it firstly identifies you to the server so that it can locate all your files. Secondly it is for security, to ensure you are a legitimate user. On a large network there might be more than just the file server, there might be an email server, a web server, and a print server (at school we have all of these).

The advantages and disadvantages of Client Server Networks are as listed above.

Peer to Peer Network

This is where 2 or more computers are networked together without the need for a file server.  It can simply be 2 computers in the same room temporarily connected via a USB to enable them to transfer or share files directly with one another. It can also be a more permanent arrangement when a number of computers in an office are connected together via cables.  In this type of network every machine is acting as both a server and a client. Access rights are controlled by setting sharing permissions on individual machines.

Advantages are:

• It is easy to set up
• There is no need for a network operating system
• There is no need to an expensive server
• There is no need for specialist staff
• If one computer fails it does not affect any other part of the network

Disadvantages are:

• It can experience slow performance (as computers access other computers)
• You cannot do a central backup (you have to back up each individual machine)
• Files are not organised/kept in shared areas
• There is no central security systems to prevent viruses etc
• Security is reduced 

This clip has been produced by a student (somewhere in the World) and it explaines P2P (Peer to Peer) networking in simple terms:

Routers

Connecting to the Internet from a home network requires a router.  The router connects all of the computers to the modem by giving them an internal IP address so that it 'knows' where to send the data.  Most ISP (Internet Service Providers) will give you a modem and router combined.