Q: Does my Nokia device support voice over IP (VoIP)?
A:
Yes, your Nokia device support VoIP telephony based on the SIP (Session Initiation Protocol). This means that the service has to be based on the same technology standard.
Please consult your VoIP service provider for more information about compatibility.
In the first phase, your Nokia device has been designed to be used with a SIP based VoIP server which resides on the same side of the firewall as the phone, for example inside company premises.
Mobile VoIP telephony is unique compared to the fixed VoIP telephony, because users expect to be able to use their mobile phones in multiple different WLAN locations, such as the office, home or WLAN hotspots. Hence the IP phone call should be able to cross different kinds of firewalls on its way to the server. In order to be able to do this, a method called Network Address Translation (NAT) is needed to translate different IP addresses on different sides of the firewall. Your Nokia devices do not support NAT traversal, a technique to enable the crossing of the firewall.
Your Nokia device support compatible enterprise voice solutions from Avaya and Cisco which operate inside the company firewall and hence do not require NAT traversal.
Dies scheint auch der E-Mail-Support von Nokia so zu bestätigen, wie in den Nokia Support Discussions hier erwähnt wird.
