[AG-TECH] Network Flow diagrams

[S.Booth]

On Mon, 20 Jan 2003, Philip J McCormick wrote:

> I've had a look in the AG docs for a diagram that shows the ports and
> network protocols used by the applications running on the AG machines
> (Display, Audio and Video), but I can't find one. Does anyone know the
> location of such a diagram or have one they can send me?
> 
> I've knocked up a quick example of the kind of thing I need. I'll use this
> one if there aren't any others out there......does it look correct?
> anything missing?
> 
> (See attached file: net_flow.jpg)
> 
> Thanks
> 
> Phil McCormick
> MCCORMIC at UK.IBM.COM

VIC and RAT use a PAIR of consecutive ports. You only specify the even one
of the pair.
Data packets are sent on the even numbered ports and control information
is sent on the odd numbered ports.
The necessary reference is:
   RFC 1889 http://www.ietf.org/rfc/rfc1889.txt

If you are doing this for firewall purposes then the other key bit of
information is that unless you are using a bridge these packets are all
going to multicast addresses. This makes them very easy to identify in a
firewall but on the other hand your networking people may have trouble
getting multicast routers to negotiate multicast-group membership properly
if there is a firewall in the way. 


Personally I no longer think the beacon is necessarily good idea it
consumes a
lot of bandwidth (proportional to the number of running beacons) and
unless your multicast has failed totally you can get much the same
information from RAT. At the very least the beacon should throttle back
the bandwidth it consumes proportional to the number of clients it is
aware of.

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