Download Networks

Data Transfer
The Kingsway School
Transfer Speed
Data Transfer is measured in bits per second
(bps)
 1 Kilobit per second is 1000 bps
 1 Megabit\per second is 1,000,000 bps
Networks
Networks are sometimes slow
This can be seen by software being slow to load
Saving and retrieving data takes a long time
Logging on is slow
Many things can affect the performance of the network:
 Topology – the way the network is set out.
 Hardware – the slowest component sets the network
speed
 Server – needs a lot of RAM and a fast hard drive
 Location of the files and software – if they are all on the
server it creates a lot of traffic on the network.
Bottlenecks
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These occur on networks. They are caused by
too much data and hardware that cannot cope.
Bottlenecks usually occur at the location of the
oldest components eg Hubs
Web Pages
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Most home users still use modems that
transfer data at 56 or 112Kbps
This can mean downloading is very slow.
When designing web pages care must be
taken to keep file sizes as low as possible.
Graphics should be kept to a minimum.
Transferring Images and Sound
Images and sound tend to be larger files.
 To reduce download time they are often compressed
to make them smaller.
Compression Standards
 JPEG (Joint Picture Experts Group) often used on
the internet compresses images down to one tenth
their original size.
 GIF(Graphics Interchange Format) This is often used
for web page buttons.
 MPEG (Moving Picture Experts Group) Used for
moving pictures
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