The 4S server software (more properly called a SIP Proxy/Registrar) runs $8,000 for a 500-user license and comes in Windows, Linux and Solaris versions. The phones range in price, LED size, and functionality, between $200 and $250. You also need the snom media server to run the voice mail, auto-attendant, music-on-hold and conferencing features. You may also need the snom 4s NAT Filter server ($7,000 for the software), which enables calls to traverse NAT (network address translation) firewalls. The NAT filter uses new protocols, called ICE (Interactive Communications Establishment) and STUN (Simple Traversal of UDP through NAT) to find and use the shortest physical paths between media endpoints whenever possible. The server supports call recording, such as you find in brokerage call centers, where proof of all verbal transactions must be kept. It also allows wiretapping, a feature that snom promotes to those considering employing the server on a service-provider basis (such as ISPs). As service providers, they must be able to give the FBI and other law-enforcement agencies unobservable access to calls.Check out eWEEK.coms VOIP & Telephony Center at http://voip.eweek.com for the latest news, views and analysis on voice over IP and telephony.
Stredicke admits that for now, the SIP business phone system is fine for the basic office. SIPs specs alone dont cover some of the features needed for call centers, and those SIP-based systems that do support them may be presumed to have added proprietary extensions to the spec. One example of these features is agent coaching: A call center supervisor can listen in on service-rep calls and whisper advice into his ear, undetectable to the calling customer.