Anoop,
I've found that bandwidth speed testers are hit and miss on the internet. To get a true accurate asessment from them I've had to do it over a span of a few days. Most sites only take into consideration the stream of data they are sending to and from you. If that stream of data is being limited do to other factors it won't give you an accurate test. Other factors include streaming music file transfers or just plain bandwidth limmiting queus. These are factors that are from your end point perspective. If there isn't anyone else shareing the same dsl then you should be able to turn everything off.
Factors that may be limiting do the the dls speed test site can include the amount of users using it at the same time. If the test site is smart they'll only allow the amount of users to use there test that won't saturate there connection. Another item could be somewhere in the path to that site your data could be going across a saturated link or it could be going across multiple paths. If it's going across multiple paths the packets could show up out of order tainting the test ever so slightly. But in the grand scheme of things every little bit counts.
I would say get a good test try a couple different days and at a couple different sites.
Patrick
