jezzzz . a écrit :
Thanks for your response. I'm looking specifically at
Asterisk in a SIP-only implementation. So no need for
Asterisk to transfer calls between PSTN and SIP. Is
there in such a case still a need for a PBX/Asterisk?
As you can see in a typical SIP communication diagram, Asterisk (proxy,
register, ...) can be useless during the communication (communications
over RTP). But before having the communication, you must do different
things :
--> find your correspondant : if you know his IP adress, you can call
him directly, if no, you need something to find him for you, with
information you have (generaly his name). It is like DNS on the web, you
can connect you to a web server if you know its IP adress, but it is
less comfortable.
--> try to establish a communication to him : with IP adress, you can.
But if he is busy, or if he does not answer, the communication is over.
But maybe you want a telephony service (and not only voice service), I
mean forward to voicemail on busy, forward on voicemail if no answer,
tell to try 10 sec and then pass to an another phone number, if you want
the caller listen a message ("Welcome on MegaWorld company, we will you
connect to the commercial service"), if you want to make the call
ringing 5 phones in the same time (like call center), ... for all theses
services, you need something between the two (or more) terminals (User
Agent). There Asterisk has his place for building a _dialplan_.
--> build a callcenter : make queues, define phone groups, implement a
CTI, you need Asterisk and its scripting power.
--> have a interactive vocal server : you need Asterisk.
--> you want security : you should want to forbid person to call some
phones (if you want to call the director from your phone, you will
directly routed to the secretary. If the call come from the financial
director the the enterprise director, the call will not be rerouted).
--> ...
You must see Asterisk like an intermediate for adding _telephony_ services :
{phone1} -------- {asterisk} ---------- {phone2}
{UAC}--------{UAS|add service|UAC} -------{UAS}
From what I understand, as long as two users know
eachother's IP addresses there's no need for Asterisk,
is this correct? I'm talking here about a pure SIP
implementation.
so if you have u1 and u2 and they simply wish to
communicate and they have eachother's IP, do they need
Asterisk for something?
Also, in a pure SIP implementation, what does Asterisk
offer and what is Asterisk required for?
Finaly, if you want make a simple call, no need to have Asterisk. If you
want to make simple calls with more comfort (call by name and not by
@IP), install Asterisk. If you want some _telephony_services_ you need
Asterisk.
Bye
GL
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