asterisk users - Aug 2003 - Semi-newbie question "Softswitch" and Asterisk - Is there a difference?

I've been working in the VoIP industry for just a bit over a year now... 
Mostly taking care of the underlying systems.  I've now reached the 
point where I'm being drawn more and more into the call processing side 
of things.  My background is in computer and "classic" telephony
systems
(DMS250/MTX, DSC 400, T1, channel banks. telabs analog echo supressor 
modules and analog mux etc).

I've seen one commercial product recently based on openh323proxy called 
a transit softswitch and now I'm looking at asterisk.

Is there a difference between what asterisk is and a softswitch?  Can 
someone explain it in small words and phrases for me?

Thanks

Bruce Ferrell

Q: What's the difference between Asterisk and a softswitch

A: About $100,000

Soft switch - Hard to afford!

Regards,
Steve

Bruce Ferrell wrote:
> I've been working in the VoIP industry for just a bit over a year 
> now... Mostly taking care of the underlying systems.  I've now reached 
> the point where I'm being drawn more and more into the call processing 
> side of things.  My background is in computer and "classic"
telephony
> systems (DMS250/MTX, DSC 400, T1, channel banks. telabs analog echo 
> supressor modules and analog mux etc).
>
> I've seen one commercial product recently based on openh323proxy 
> called a transit softswitch and now I'm looking at asterisk.
>
> Is there a difference between what asterisk is and a softswitch?  Can 
> someone explain it in small words and phrases for me?

Hi Bruce,

On Wed, 6 Aug 2003, Bruce Ferrell wrote:

[...]
> Is there a difference between what asterisk is and a softswitch?  Can
> someone explain it in small words and phrases for me?
Sure, there is. First of all, * is much cheaper.

But technically, * does much more than a soft switch:
AIUI, a classicals "soft switch" _only_ serves the purpose of managing
call setup for a group of terminal devices.
* is more like a classical PBX:
Terminal devices can actually connect to *. Asterisk can either simply
transfer calls to the correct location (much like a soft switch), but it
can also function as a (quite universal) telephony gateway (or
"proxy").
Additionally, * provides advanced IVR scripting, Voicemail, call queueing,
and with some tweaking: a text-to-speech gateway, or even voice
recognition.

I guess you get the picture, but let's try to list asterisk's features
along with their "classical VoIP" pendant (AFAIK them) in brackets:

- manage call setup between end devices and gateways (soft switch)
- Convert VoIP calls to analog (or ISDN) lines (POTS or ISDN gateway)
- Connect otherwise incompatible VoIP devices, eg SIP<-->H.323
  (advanced soft switch)
- Convert incompatible audio codecs, eg GSM to G.711 (?)
- Provide outside access for an otherwise firewalled IP phone network
  (VoIP proxy)
- Voice Mail (voice mail system)
- IVR applications (IVR server)
- Music on hold source (?)
- ... (I'm quite sure I forgot something.)

As you can see, I'm not quite a specialist in classical telephony systems
(or maybe some of *'s functions just do not have a classical pendant), but
I guess you got an idea.

Cheers,
	Siggi