[AG-TECH] Unicast-Multicast bridges?

S.Booth spb at epcc.ed.ac.uk
Tue Feb 19 09:24:29 CST 2002

On Thu, 14 Feb 2002, Mike Daw wrote:

> At http://www.east.isi.edu/~tlehman/programs/mboneuctomcgw/ you'll find an
> easy to install and easy to use piece of code that seems to work pretty well
> as a bridge. Any site that has working multicast can deploy it and any site
> that has only unicast can access it.
> I tested it this afternoon with Newcastle, Cardiff and Edinburgh all coming
> in via our bridge. This was with multiple video feeds and audio from each
> (and 2 reflector processes on my machine). The quality was indistinguishable
> from normal multicast use.
> The network usage went up, of course, but there's no reason why multiple
> sites shouldn't be running the software, so easing the load on any one site.
> In terms of security, I'm told that it's possible to wrap the bridge machine
> within a strict firewall, so making it secure. Having looked at the code, it
> also looks pretty easy to insert a few lines so that a list of IP numbers is
> consulted before access is granted to a remote machine.

I have been playing around with this code. There were two main problems
1) No access control
2) The bridge remained a member of the multicast group even when there
   were no unicast clients. This can cause unnecessary bandwidth to the
   site running the bridge.

I am attaching a modified version with these fixed. I have also changed
the main data structure to make the code work under Solaris and optimise 
some of the loops.

I have done some rudimentary initial testing but would be keen to know
other peoples experiences.

access control is done using a bridge.acl file. You can add a network to
the list using lines like

An empty list or no acl file enables all clients.


|epcc| Dr Stephen P Booth             Project Manager           |epcc|
|epcc| s.booth at epcc.ed.ac.uk          Phone 0131 650 5746       |epcc|

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