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Rapid IE changes the TCP Window Size and Selective
Acknowledgement settings to optimize TCP parameters in
accordance with recommendations from request-for-comments
(RFCs) released by the Internet Engineering Task Force
(IETF).
The TCP Window controls how much data can be downloaded
before your computer must send an 'acknowledgement' - a
small piece of information acknowledging receipt of the
data. Larger windows yield better performance because less
time is spent sending acknowledgements. Smaller windows
yield better error recovery because the more frequent
acknowledgements help identify erroneous transmissions more
quickly. Each error requires retransmission of the whole
TCP window.
The TCP Window Size affects transmission speeds and
quality even more with asymmetric connections such as Cable,
ADSL and 56K modems because asymmetric connections deliver
significantly different upload and download speeds.
Selective Acknowledgements (SACK) lets your computer
request retransmission of only the lost packets, instead
of the whole TCP window. This provides potentially huge
performance advantages, especially with a large TCP Window
as only the lost bytes instead of the whole TCP Window
(which may be hundreds of kilobytes) is retransmitted
Rapid IE enables SACK and selects an optimal TCP Window
Size based on the type of connection. These two settings
can significantly speed up web page viewing.
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