public string ToUri() {
string relay = ((AHSender) _sender).Destination.ToMemBlock().ToBase32String();
string dest = _dest.ToMemBlock().ToBase32String();
return System.String.Format("sender:fw?relay={0}&init_mode={1}&dest={2}&ttl={3}&mode={4}",
relay, AHHeader.Options.UShortToString(((AHSender) _sender).Options),
dest, _f_ttl, AHHeader.Options.UShortToString(_f_option));
}