Here is an explanation from ICSI about network buffering: »
n1.netalyzr.icsi.berkele ··· fer.htmlsaid by ICSI :About this test: In addition to latency and bandwidth, one final, often overlooked aspect of network quality is the amount of buffering.
Often, your computer wants to send or receive data faster than some point in the network allows. Thus that point needs a buffer to store this data until it is able to send it. The problem arises when the buffer is too large or too small. If the buffer is too small, network protocols such as TCP are unable to send as fast as the network allows. If the buffer is too large, a single transfer will fill up the buffer, delaying all other traffic.
Currently, a lot of users have networks which are significantly over-buffered. As a result, if the network is running at capacity, packets may be substantially delayed. This is why, for example, BitTorrent may slow down a user's web surfing, even though TCP is able to share all the bandwidth, the file transfer fills up the buffer which now slows down all other traffic.