There are already filters that watch packet content for several applications, so this would most likely exist for gnutella as well. Read some other posts on this forum for examples. Ports are just the easiest way to block stuff like this, however if an ISP decides to filter the data then there is not a lot that can be done about it escept maybe open an SSH connection.. which would not be hard either for an ISP to see.

If an ISP wants to block gnutella, it can do so very effectively.. Will they? I doubt it.

Tam