Network - two or more computers linked together in order to share resources e.g. software, hardware, data, information

Data communication - sending and receiving data from one computer or data processing device to another

• bits are sent via an interface one bit at a time over a single wire from source to destination
• very high data transfer rates e.g. 1000Mbits per second

• used inside the computer for short distances (up to a few metres) e.g. to printer
• parallel port can send 8 / 16 / 32 bits simultaneously down separate lines

Baud rate - (in bits per second) -> speed at which data is transmitted serially

Framing bits - (start, stop, error detection) are transmitted with each character

Bandwidth - the range of frequencies that can be sent / received (measured in Hz)

• timing signals control rate of transmission
• no start and stop bits
• used in main frames
• less error prone

• characters sent one at a time
• each character has start, parity and stop bit
• baud rate must be same at both ends
• used in PCs
• fast and economical for small amounts of data

Handshaking - exchange of signals between devices to establish their readiness to send / receive data

• to send data over telephone line must be in analogue format

• high speed digital communications network to replace current telephone network which requires digital-to-analogue conversions and to replace traditionally analogue forms of data, ranging from voice to computer transmissions, music, and video
• requires high bandwidth

Data compression - repeated bytes only sent once with count of repetitions

LAN -> 1 building / site (up to 2 km)

• on a client-server network the server is a computer running administrative software that controls access to the network and its resources
• on a 'peer-to-peer' network all computers can act as servers to the other computers on the network but one computer could be designated a printer server etc.

Twisted pair (copper cable) -> telephone line (analogue)

Fibre optic (digital)

Coaxial - insulated so that signals carried don't affect nearby components

Communication satellite - use satellites in geosynchronous orbit

Public lines - dial-up networking

Leased lines - fixed annual fee

WWW is a facility of the Internet -> series of web sites / pages which contain information and are held on host computers

Internet -> worldwide collection of networks

http / ftp / localhost -> protocol used for connection to server

Domain name -> name of server on which Web resource is held

IP address -> unique address of home page e.g. 177.234.443.968

The domain name system maps the domain name onto the IP address