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Secure 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
Secure 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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