With all the chatter about VOIP products in the marketplace, I think it is important for new comers who are still trying to understand the technology and offerings out there of 1 very clear distinction. VoIP and IP Telephony are not the same.
In its infancy, most everyone was reffering to VoIP. As you research IP-PBXs, and the different approaches Avaya and Cisco, and Alcatel and others bring to the table, be aware that VoIP is merely one application of IP, the ability to run voice over it. The larger picture, which you should really focus on, is IP Telephony, which entails not just voice, but voice, video, data, etc. as applications that use IP as the mechanism for transport. The two sound similar, but there is a difference. Understanding this difference will better help enable you to udnerstand the idfferent approaches companies are using, and what the pros and cons of them are.
With this said, many companies are using a dual approach to IP Telephony. Solutions that are designed for those who have exisitng legacy PBX’s in place, and wish to IP enbaling them), and those who want to start from scratch with an IP telephony solution, and use a differnt product which has been more truly engineered for data transport.
Be aware of the differences, and be careful of appraocehs that compromise the data or voice aspects; especially the voice (QoS, 5 9’s reliability, and PBX capabilities).