7.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:
■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 pro- tocols 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
■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 Aastra 800 gives users all the features of system telephony through its use of an IP-based protocol. Furthermore, the standardised SIP pro- tocol 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 Aastra 800 provides you with the fol- lowing options (see also SIP Telephony starting on page 66):
■You can use low-cost “SIP trunk lines” with your existing Internet connection
■You can use the services of a SIP gateway service provider to access the public telephone network (PSTN)
VoIP Telephony via intranet with the Aastra 800 offers the following possibilities:
■Use of IP-based system telephones and of SIP telephones connected to Cat5 twisted-pair ethernet cables
■Use of IP-based system telephones and of SIP telephones via VPN, RAS, Branch or WLAN connections
■Use of PC-supported system telephones (so-called “Softphones”) without extra hardware costs
