Friday, May 15, 2009

Difference between throughput and goodput?

Goodput measures the rate of data transmission/reception
at the application layer without taking into account
retransmissions. Applications like iperf typically report the
goodput seen by a typical application layer when operated
in TCP. However if iperf is used with UDP, which is a best
effort protocol, it is a better idea of the throughput seen on
the channel being measured.

Throughput is typically measured at layer 2/3 of the
network stack, thus including protocol overheads and
any retransmission. Hence in quite a few cases the
useful goodput is <<< throughput measured. For
example in file transmission, the "goodput" corresponds
to the file size (in bits) divided by the file transmission

Monday, May 11, 2009

What is an earth browser?

An earth browser can be defined as a
software that allows the user to view
2D and or 3D maps of the earth.

Examples of earth browsers are -
Google Earth,
Apart from being a viewer for the maps,
the google earth browser also supports
a XML based programming interface.
The language is called as the Keyhole
Markup language (KML) named after
one of the first reconissance satellites
launched in 76. The KML schema allows
the user to place and move objects over
google earth as a baseline application based
on point co-ordinates of the location.