User guide

101
Voice over IP (VoIP)
Voice over IP (VoIP)
The term “Voice over IP” describes the usage of IP-based data
networks for telephony. It is possible to distinguish between two
different types of VoIP:
z Telephony via Internet provides cheaper charge-models for
telephone services. For telephony directly via the Internet,
only the cost of data transmission is incurred. Various Gateway
providers can provide crossover into the PSTN (“Public
Switched Telephone Network”) for a fee. As well as
standardised protocols such as SIP and H.323, proprietary
protocols such as the Skype network, are used. Voice and
service quality via Internet is often indeterminable because
they are dependent on the communication lines of various
service providers. which have been optimised for data
communication
z Telephony via Intranet enables joint usage of existing
infrastructure for telephony and for data communication.
Integrating the two communication networks into a single
communications network can provide considerable savings.
The Forum 523/524 gives users all the features of system
telephony through its use of an IP-based protocol.
Furthermore, the standardised SIP protocol can also be used
on the intranet. The control of the data connections used
makes it possible to define exactly the voice and service
quality.
VoIP telephony over the Internet using the Forum 523/524 pro-
vides you with the following options (see also SIP Telephony start-
ing on page 117):
z You can use low-cost “SIP trunk lines” with your existing
Internet connection
z You can use the services of a SIP gateway service provider to
access the public telephone network (PSTN)
z Automatic fallback (bundle overflow) to ISDN connections in
case of the breakdown or over-occupancy of the SIP
connection