Computer network

What is a (computer) network ?
•“an interconnected collection of autonomous computers”
interconnected = able to exchange information

•“a set of nodes connected by media links”
node = any device capable of sending &/or receiving data to &/or from other nodes in the network

•“a connected collection of hardware and software that permits information exchange and resource sharing”
information = data, text, audio, video, images, …
resources = printers, memory, link bandwidth, ...

Networks vary in:

•type:Ethernet, Cable TV, telephone network, Internet, cellular…
•size:from a few computers close together, to a world-wide
network of networks containing millions of computers
•technology:copper wire, coaxial cable, wireless, fibre optics…
•technical issues:services offered, rules for inter-computer
communications, how users are charged for network use...
 

Why all these variations ?
Due to a combination of factors, including:
•different target applications
•different operating environments
•historical reasons
•lack of (sensible) standards
•difficult problems ⇒no “optimal”solutions