[GnomeMeeting-list] making a call takes ages. Is that because of ILS?

[Jerome Lacoste <jerome coffeebreaks org>]

2 clients:

C1: gnomemeeting 1.0.2 on Debian unstable
C2: gnomemeeting 0.9.5 on Mandrake 9.2

C1 is behind a hardware router (DLink DI-624) which does NAT and port
redirection (and of course firewall)
C2 is on a simple PC with integrated iptables based firewall

test done this morning at around 01:AM GMT

C1 calls C2: (using h323:IP:port format) call screen takes below 3
seconds to be routed, 
C2 calls C1: (using callto:ils.seconix.com/login) call screen takes 35-
40 seconds to appear 

Why does this take so much time to contact C1 from C2? Is that because
of the directory redirection? shouldn't that be fast, much like a DNS?

Or is it because of the gnomemeeting version difference?

Or anything else?

Jerome