use this test to help understand whether your broadband line will support VOIP
http://myspeed.visualware.com/servers/namerica/iad.php?testtype=-1&codebase=mcslhr.visualware.com&location=UK:%20London&cm=no&ver=9&map=uk&lines=1&pps=50&bpp=160&codec=G.711&provtext=Visualware&provlink=http://www.visualware.com/&width=600