Normally to set up a new VAS service, we need to connect them to SWITCH (NGN). Earlier we  have  to  add  additional  dedicated  E1s  between  new  server  and  SWITCH.  But  now
situation is different. New services are implemented using IP technology. Magic voice is an
example for that.

What is Magic Voice?

You can call to another Same Network Customer using different predefined voice (Cartoon voices,
Kings  Voices,  etc.).  This  service  is  provided  through  an  Application  which  is  provided
by a 3 rd party company. That application will do the conversion of the voice. 

We  can  use  Session  Initiation  Protocol  (SIP)  &  Real  Time  Protocol  (RTP)  protocols  to implement this service. We only have to configure IPs on both sides as shown in the Figure.
SIP will handle signaling phase and RTP will handle the data phase.
Call setup will be done in the usual manner and after successfully setting up the call VoIP
tunnels will be created between the called party and calling party.