Source : Free On-Line Dictionary of Computing

IP Telephony
     
         (IPT, Internet Telephony) Use of {IP} data
        connections to exchange {voice} and {fax} data that have
        traditionally been carried over the {public switched telephone
        network}.
     
        During the late 1990s, an increasing number of telephone calls
        have been routed over the {Internet}.  Calls made in this way
        avoid PSTN charges.  Unlike traditional telephony, IP
        telephony is relatively unregulated.
     
        Companies providing these services are known as {Internet
        Telephony Service Providers} (ITSPs).  They include telephone
        companies, cable TV companies and {Internet Service Providers}
        (ISPs).
     
        There are still many problems with voice quality, {latency},
        {compression} {algorithms}, and {quality of service}.
     
        {Voice over IP} is an organised effort to standardise IP
        telephony.
     
        See also {Computer Telephone Integration}.
     
        {Internet Telephony Overview
        (http://www.fokus.gmd.de/research/cc/glone/projects/ipt/)}.
     
        (1999-03-17)