computer communications and networking notes

• network- a collection of connected computers plus their peripherals
• node- device on a network

LANs

• local area network
• confined to one site
• connected using equipment owned by the organisation
• maintained by the organisation
• central data storage makes data sharing possible and convenient and makes backups easier to do
• easily updated or reconfigured centrally
• computer use can be easily monitored
• security policies can be centrally administered
• users can communicate with each other
• expensive peripherals can be shared
• maintenance incurs an expense
• specialist staff may be needed
• network problems might affect all users
• security may be a problem because data is accessible from many places

WANs

• wide area network
• covers a large geographical area
• often connect LANs together
• make use of publically available telecoms facilities
• allow a business to function from any location

network hardware

NICs

• network interface controllers/cards
• aka LAN adapter
• built into the motherboard
• used to be installed as separate cards or circuit boards
• LANs make use of the network standard Ethernet
• makes sense to include an adapter as part of a computer becuase it will work nearly everywhere
• has a unique number stored in ROM
• called a MAC- media access control address
• allows each node on a network to be identified
• physical device
• generates and recieves suitable electrical signals
• can also carry out simple addressing by making use of MAC addresses

cables

• connections between devices on most LANs are made with copper cable
• UTP- unshielded twisted pair
• light and flexible- makes it easy to install
• for longer distances and use outside- fibre optic
• transmits signals by using light waves
• can carry more signals for their size than copper cables
• cheaper

hubs

• hardware devices that connect many network dvices together
• makes them into a single network segment
• segment- defined part of a network
• have a number of input and output ports which connect to each other
• a signal arriving at one is transmitted to all others

switches

• connect network segments or devices
• act as bridges- connect more than one network
• allows them to function as one network
• differs from a hub- transmits a message only to the device intended 

wireless access points

• allow connection to a LAN without the need for physical cables using standards e.g. wifi
• often connected to a router
• can save money and effort
• new nodes can be added without the need for more cable
• introduce security risks which have to be dealt with
• encryption, hiding broadcast identities, allowing access to only certain MAC addresses

routers

• receives data in packets
• forwards them to their destination
• direct traffic through large networks
• small routers are used in the home to connect individual computers to the internet service provider

types of network

client-server

• one or more servers provide servers to many client machines where the users work
• servers- computers set up to handle network functions
• typically high end computers with enough storage and speed to serve the needs of many connected computers
• database, file, mail, print, web, gaming
• possible to save hardware expense by having virtual servers- one physical machine…