The firewall installed at my college's router allows me to surf the internet but never allows me to download any package that has a size more than 100mb. I wonder how exactly does it differentiate between the two. According to my concept, they're both a flow of http packets so they should not be differentiable.
Furthermore, If I start downloading from proxysite.com (it encrypts all the traffic), the firewall couldn't differentiate and allows me to download even tens of GBs of data. Can you explain what exactly is going on here?