...
>Image my suprise when the biggest causer of broadcast traffic, is the TSM
>AIX server, itself !!!!!
...

Zoltan - Good find!

I would like to see your network people narrow this down to get more
identifying details (protocol (TCP,UDP), port and packet type).  You know
the clogging traffic is coming from the AIX system...but from what within
it?

If not from them, then consider doing an AIX iptrace, ipreport sampling of
network traffic during the client backup.  You can also do 'netstat -s'
sampling and see what numbers are climbing as this is going on.  AIX does
Path MTU Discovery, per its Network Options settings ('no' command) utilizing
ICMP packet attempts, which may have issues with router blocking.
'netstat -s' will show those numbers, among others.

   Richard Sims