Serving large files to a nation-scale audience is a challenge. It is even harder if the downloaded file is a binary installer and a considerable percentage of users use an old version of Internet Explorer which reports a file only partially completed as finished successfully.
Our customer had an issue with shipping their binary installer to his users.
In 2009 we have designed and deployed a raw network dump analyzer in order to diagnose issues with the file-serving infrastructure. Thanks to this, several issues have been identified and fixed, reducing the failed downloads from up to 80% down to a few percent (almost exclusively gprs users and user-cancelled transfers were left).