IP Telephony Alternatives
IP enabled PBX
A private branch exchange (PBX) that supports the IP protocol along with
the traditional analog and digital circuit-switched (TDM) connections to
the PSTN and telephone sets.
IP Centrex or Hosted IP
Centrex is PBX services provided by a local telephone company. Switching
is done in the telephone company's central office. Some services do the
switching at the customer's site, but control it in the central office.
IP Centrex is a Centrex service that provides sophisticated PBX features
using network-based software. It is delivered over data lines to a mixture
of IP telephones, PC-based soft phones, and, via gateways, to conventional
and wireless telephones.
Pure IP Telephony
This method replaces the existing phone system with IP telephones, call
processing managers, gatekeepers, gateways, power distribution systems,
and cabling. In this method, voice is converted immediately at the IP
phone to a digital signal for transport over the IP network. Call
processing managers maintain and control the call setup and dial plans.
Gateways provide connectivity to the PSTN for off-net calling. All on-net
calls are routed over the IP network.
