Networks

Created from P.M.T. and Ada Comp. Sci notes

What is a network?

Two or more computers connected together with the ability to transmit data between each other

What are the advantages of a network?

• The ability to share files

• The ability to have multi-user systems

• The ability to share expensive hardware devices between multiple users

• The ability for the organisation to track what users are doing (this can of course be a disadvantage for the individual user)

What are the disadvantages of networks?

• Extra hardware costs (cabling and connection devices)

• Greater security risks

• Potential cost of having to have employ someone to look after the network (depending on the size and type of the network)

What is a local area network?

• A group of coputers/devices connected over a small geographical area.

• The infrastructure is usually owned by the network owner

LAN is the abreviation of…

…abreviation of local area network

What is a wide area network?

A group of computers/devices connected over a large geographical area, often using 3rd party communications channels

WAN is the abreviation of…

…abreviation of wide area network

What is a protocol and why are they important for network communications?

• A set of rules defining how computers communicate with each other

• They allow standardisation so that all devices have a designated method of communicating with each other, regardless of manufacture, OS, software etc.

• The sending system has no direct control over the way the receiving system responds

• Protocols allow for data to be exchanged in a predictable way/ in the correct format

What is a proxy?

A server that acts as an intermediary, collecting and sending data on behalf of the user

What are the benefits of using a proxy?

• The privacy of the user is protected and they remain anonymous

• Can be used by administrators to prevent access to sensitive or irrelevant information at work or at school

• The proxy server can cache frequently used website data making it faster to load

What is a network interface card/contoller?

• A hardware device that is used to connect a computer/device to a network

• Each NIC has a unique MAC address

What is a wireless access point?

A hardware device that allows wireless devices to connect to a network

What is a modem?

A hardware device used to modulate the electrical signal, i.e. to change the signal so that it can be sent through a cable that uses a different technology.

What is a gateway?

A network device that provides a link between two dissimilar networks (e.g. a LAN and the internet)

What is a firewall?

A hardware device or piece of software that monitors and filters traffic going to and from a network.

Why are firewalls used?

• To prevent unauthorised access to a network.

• To restrict websites that can be accessed from within the network.

• To restrict applications that are used internally and have internet access.

What is a bridge?

A network device that provides a link between local area networks

Purpose of a network switch

• Joins computers/devices together on a LAN 

• Receives packets/data 

• Recipient’s MAC address is given in packet header

• Send packets/data out the correct port to the specific computer device

What is a router?

A network device used to connect two or more networks together.

Describe a peer-to-peer network

• A network in which computers are connected to each other so that they can share files.

• Each device can both provide resources to other computers (peers) and request resources from other computers

What are the advantages of a peer-to-peer network compared to a client-server network?

• Cheaper to set up

• Easy to maintain - no specialist staff are required

• Not dependent on a central server, so no single point of failure

What are the disadvantages of a peer-to-peer network?

• Backups must be performed separately

• Poorer security

• May be difficult to locate resources

• Impossible to trace the origin of files

Describe the client-server network

• A network that consists of terminals known as clients connected to a server.

• The server is a powerful, central computer. The server holds all of the important information and resources.

• The server tends to have greater processing power than the clients

• The server provides access to a resource/service

• Client computers connect to server 

What are the advantages of client-server compared to peer-to-peer?

• One location to backup

• Centrally administered in one location - easier to manage users/access

• Easier to keep data secure. 

• Technicians can more easily remotely install / monitor

What are the disadvantages of the client server model?

• The server is a central point of failure

• Can be expensive to set up - server hardware is costly

• Can be expensive to maintain - requires specialist staff

Unshielded twisted pair cable

• Consists of twisted pairs of copper wires

• Resilient to interference - twisting means that any interference would affect both wires of the pair in the same way, which cancels out the interference

• Reliable up to 100 metres distance

UTP is the abreviation of…

…abreviation of unsheilded twisted pair

Fibre-optic cables

• Cables that carry light

• Not affected by electical interference

• Can carry signals over very long distances

Coaxial cables

• Type of electrical cable that can be used to carry data

• Has numerous issues with poor connections

• Not commonly used anymore