Most BitTorrent clients offer security options along these lines:
- Allow the use of encryption as required
- Exclusively accept peer downloads only from those who will encrypt it
- Exclusively provide peer uploads only to those who will accept encryption
The purpose of encryption is indeed to avoid Packet Shaping (also known as Traffic Shaping), of which a description follows:
ISPs (Internet Service Providers) can and often will detect network activity that has been previously identified as detrimental to the overall reliable operation of their network. ISPs generally hate BitTorrent activity because it\'s a bandwidth burden they want to avoid (even though you\'re paying for it). Thus, enter Traffic Shaping. If BitTorrent activity is detected, a computer somewhere will heavily throttle the data ports being utilized to slow down bandwidth use drastically. Remember that such schemes are looking for signature data that can be associated with BitTorrent and not usually overall bandwidth use. Thus, if the data is encrypted then the ISP doesn\'t have a means to detect BitTorrent activity, and their efforts are thwarted. Ha!
So, some people are forced to use encryption methods. If you don\'t have a problem with this, you have little need to use encryption.