2N VoiceBlue Enterprise - User Manual - Manual (Page 64)

5-2 2N
®
VoiceBlue Enterprise
5.1. VoIP Network Arrangement
VoIP telephony communication has two components – signalling
and voice. Signalling is primarily used for establishing and
terminating calls, telephone login to a PBX, negotiating
parameters and control of the speech/voice channel. The voice
channel is only used for transmission of encoded digitised voice
information.
Typically, VoIP telephones are operated together with a PBX,
which coordinates their traffic. For a schematic arrangement see
fig. 20. The VoIP telephony PBX is a software application that
looks like a traditional PBX. Its functions include mainly
numbering plan consistence maintenance, routing, user or
telephone rights, call billing, call forwarding, DISA, etc. But it can
integrate more functions, e.g. voice mail. SIP telephone PBXs are
usually called SIP proxies while PBXs for H.323 are called
gatekeepers.
LAN
VoIP telephones
VoIP PBX
(SIP proxy /
gatekeeper)
voice stream
signalling
Fig. 20 – VoIP PBX Arrangement
To work properly, a VoIP PBX must process all signalling traffic.
Unlike this, voice channel data are transmitted directly between
the terminal points. This is, among others, a difference from the
model described below.