SIP Phone

Hi Guys hope you can help

I have the Lastest Openfire installed on my Linux Server and the Lastest Spark Client on my Windowz XP Workstations. All is working Fine. All users can Chat, File Transfer etc. No Problems there.

I installed the Phone Plugin on the Openfire Server and have USB SIP Phones on my Windowz Desktops. Do I still need to install Astrisk Server on my Linux Server to get the Users to do VOIP or do I just Configure the SIP Phone Mappings?

What and how do I Configure on the Openfire SIP Phone Mappings Options to get VOIP to work?

Any help greatly Appreciated