On Oct 22, 2007, at 4:09 PM, <michael.dillon at bt.com> <michael.dillon at bt.com> wrote: > >> I can't think of an obvious way for a p2p client to detect this. > > Work through middleboxes installed in the ISP's network and configured > by the ISP. More comcast blocking http://kkanarski.blogspot.com/2007/09/comcast- filtering-lotus-notes-update.html