>X tends to run over TCP, which is "multicast challenged", yes?

    There are multicast "group" addressing modes in IP.  An application on
    the client issues its TCP/IP stack a command to join a specific group.

The IP part of TCP/IP has multicast capabilities.  TCP as the "transport
layer" reliable protocol does not include multicast.  I think there is a
multicast reliable stream protocol (experimental) analagous to TCP, but X,
as far as I know, is pretty married to TCP itself.  (All that display
independence, and stuck with a single network protocol.  Sigh.)

BillW
cisco

PS: Just wrote an application for cisco access servers that can multicast
data from async lines (using raw, unreliable UDP protocols.)  So when I say
"TCP doesn't support multicast", there's a bit of experience behind it.