Voice conversation in home office with ICS

[AriJ]

I have had trouble with audio conversation in Windows Messenger inside
our home office. I have two PCs, a desktop and a laptop, one is
configured as an ICS server, the other is a client (I have tried both
ways). When I try to establish a voice conversation from the connection
sharing PC to my wife at the client, the result is a connection timeout.
The same holds also for the other direction, except for the case that
our desktop is configured as an ICS server. Both PCs are running Windows
XP Professional SP2, and Windows Messenger 5.1.0639

I have done some packet sniffing with ethereal, and the results are
attached at the end of this message. My conclusion is that in the failed
cases the second session acceptance message (sent by the peer that
initiated the conversation) includes an ip address that is a
UPnP-translated external address. This seems weird since the peers
should communicate without passing through ICS. Right?

My guess is that UPnP-enabled port opening/forwarding is used only for
packets entering the ICS PC through the external interface, not for the
packets originating from the client or the ICS PC itself. That would
explain the problems in SIP signaling.


-Ari Jasberg




ICS: public ip 80.186.xx.xx (ICF on),
internal ip 192.168.0.1 (ICF off)

Client: ip 192.168.0.100 (ICF off)


Setup 1:
------------

ICS = Laptop
Client = Desktop

a) Client invites ICS:

Client -> ICS: INVITE
ICS -> Client : ACCEPT, IP-Address 80.186.xx.xx
Client -> ICS: ACCEPT, IP-Address 80.186.xx.xx:5619
TIMEOUT


b) ICS invites Client:

ICS -> Client: INVITE
Client -> ICS: ACCEPT, IP-Address 192.168.0.100
ICS -> Client: ACCEPT, IP-Address 80.186.xx.xx:6970
Client -> 80.186.xx.xx:6970: SIP INVITE, Via: SIP/2.0/UDP
80.186.xx.xx:30956
Last message repeated 7 times
TIMEOUT




Setup 2:
------------

ICS = Desktop
Client = Laptop

a) Client invites ICS:

Client -> ICS: INVITE
ICS -> Client: ACCEPT, IP-Address 192.168.0.1
Client -> ICS: ACCEPT, IP-Address 80.186.xx.xx:52433
TIMEOUT


b) ICS invites Client:

ICS -> Client: INVITE
Client -> ICS: ACCEPT, IP-Address 192.168.0.100
ICS -> Client: ACCEPT, IP-Address 192.168.0.1:15973
Client -> 192.168.0.1:15973: SIP INVITE, Via: SIP/2.0/UDP
192.168.0.100:16140
....
....
Connection established