[AG-TECH] RE: [AG-DEV] Bridge Information

Ivan R. Judson judson at mcs.anl.gov
Wed Mar 8 09:14:42 CST 2006

Touching a bunch of packets (filtering for the SDES Name packet and
modifying it) seems extremely intensive to meet the end goal.

Are you trying to determine if the local client is bridged or if any of the
remote clients are bridged?

Seems like it's a bit of information the venueclient already has and should
be able to simply show the user on the local end. It might be something
simple like updating something in the venue to share that so you can see the
state of all non-local clients.

Does that make sense?


> -----Original Message-----
> From: owner-ag-dev at mcs.anl.gov [mailto:owner-ag-dev at mcs.anl.gov] On Behalf
> Of Andrew A Rowley
> Sent: Wednesday, March 08, 2006 4:49 AM
> To: AG-TECH mailing list
> Cc: ag-dev at mcs.anl.gov
> Subject: [AG-DEV] Bridge Information
> Hi,
> I have another idea that someone might like to implement (I will try if I
> have time at some point).  Currently, it is difficult to work out if a
> client is bridged or if they are using multicast.  The bridge forwards the
> traffic from the client without modification.
> One idea that would make it easier to determine if someone was bridged or
> not would be to add some information to the RTCP packets when they arrive
> in the bridge program (quickbridge, InSORS bridging software or other
> software), such as adding " (B)" to the end of the NAME SDES packet.  This
> would be fairly simple to do I think - when a packet comes in with an RTCP
> header:
> 1. Search the RTCP packet for the SDES header
> 2. Search for the SDES NAME packet
> 3. If the NAME field exists:
> 3.1  Add 4 to the length of the SDES header (note that padding does not
> need to be altered in this case)
> 3.2  Add 4 to the length of the NAME field
> 3.3  Shift the bytes after the name field up by 4
> 3.4  Add " (B)" to the name field.
> I guess the main problem here would be if the packets were encrypted.  In
> this case, the RTCP packet would not be detected, and therefore nothing
> would happen.  Alternatively, the bridge could be given the encryption
> key.
> An alternative to modifying the bridge would be to modify the actual RTP
> tools (VIC, RAT, InSORS, etc) to add the " (B)" to the name when a unicast
> connection was being made (or " (U)" if that is more generic).  This may
> actually be the easier option.
> Just an idea...
> Andrew :)
> ============================================
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