[AG-TECH] Bridge Information

Andrew A Rowley Andrew.Rowley at manchester.ac.uk
Wed Mar 8 05:49:29 CST 2006


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 :)

Access Grid Support Centre,
RSS Group,
Manchester Computing,
Kilburn Building,
University of Manchester,
Oxford Road,
M13 9PL, 
Tel: +44(0)161-275 0685
Email: Andrew.Rowley at manchester.ac.uk 

More information about the ag-tech mailing list