2N VoiceBlue Enterprise - User Manual - Manual (Page 65)

Insight into VoIP Gateway 5-3
It is because a PBX is not necessarily required in the IP telephony.
Signalling protocols are designed in such a manner that it is
possible to call from one terminal to another directly, without any
mediator. To do this, you have know the full ID of the terminal to
be called, i.e. also the IP address and destination port, of course.
This is the main disadvantage compared with the preceding model
for multiple-telephone locations.
LAN
VoIP telephones
voice stream
signalling
Fig. 21 – "Point-to-Point" Arrangement
If you use a PBX, the terminal points must know the PBX address
only. The PBX is able to route requests according to information
acquired in the process of telephone login to the PBX. With the
"Point-to-Point" arrangement, all telephones must be equipped
with information on surrounding telephones. This model is mostly
applied in direct calling via the Internet where you do not want or
cannot use services of any telecom provider.
The 2N VoiceBlue Enterprise gateway is capable of working in
both the types of environment, with a PBX and without a PBX.
LAN
VoIP telephones
VoIP PBX
(SIP proxy /
gatekeeper)
voice stream
signalling
GSM network
Fig. 22 – VoIP-to-GSM Gateway with PBX