[Asterisk-Users] SS7 signaling/Softswitch

[Brad Waite]

Ray Burkholder wrote:

> The MWI you mention is probably part of CLASS services, and is probably a
> function of AIN on an SS7 SCP (Service Control Point), to which a Telco's
> switch is connected.

Close.  Normally, at least in Qwest-land, third-party VM provider systems dial 
into the switch and give it a DN and a MWI on-or-off command.  If the DN is 
serviced by that switch, it turns the message waiting indicator (stutter 
dialtone, MW light or both) on or off.  If the number is on a remote switch, the 
information gets sent over the SS7 network to the other Qwest switch.  I haven't 
seen MWI specifically mentioned as standard message sent via SS7, but obviously 
it's being done.  I don't know enough about the details of SS7 to know what 
messages can be sent or if there's a generic container message that can be used 
for anything.

> It doesn't directly answer your question, but I would guess that the Class 5
> switch has to make some sort of translation between what happens in the D
> channel on a PRI and what it needs to communicate over its backend SS7

 From my research that's correct.  The PRI's D channel doesn't speak SS7, 
although the protocols are extremely similar in function.  Everything I've read 
says that getting out-of-band signalling to the CP was the whole point in 
creating ISDN.  What I'm trying to find out is if there's some way to send a D 
channel message that would get translated directly into SS7.  The ISUP layer of 
the SS7 protocol is the ISDN User Part - is that designed to encapsulate CLASS 
messages?

Take ANI for example.  Your PRI sends the ANI information to the near end switch 
over the D channel which then passes it on (without verification, I might add) 
on to the destination switch via SS7.  This is a case where the information is 
transferred directly.  What about LIDB lookups or route information?  Is there 
any way to get this, which is definitely available over SS7, from the D channel?

> network.  I see two proper solutions:  a) implement SS7 directly so you have
> access to the signaling network for your application, or b) just handle the
> communications over the ip network in a converged network scenario.  By the
> way, why do you ask the question of the D channel message?  What is your
> application?

If you haven't already inferred this, we using * for, among other things, third 
party voice mail.  Qwest wants to charge $700/mo for their Message Delivery 
Service ( the dialup MWI I mentioned earlier), but if the information can be 
sent over my D channel, I shouldn't need their service.

> So, the proper answer is that if you really want to implement this PRI - SS7
> - PRI message, you should really be talking to your nearest CO Engineer or
> Telco Enterprise Business Office where they handle this all the time for
> enterprise call center applications.

Hah.  I've yet to have any luck talking to anyone that _really_ knows what's 
going on.  Or at least anyone that knows what's going on *and* can think out of 
the box.  I wish I could find a fone phreak that was hired by an RBOC and knows 
stuff from the inside and out.  I would fit the bill, but I didn't get to spend 
enough time on the inside to get a big enough handle on interconnections.

> On the other hand, maybe Gus could contribute a regular tutorial on how he's
> got various things interconnected.  The more the info, the better.  Gus once
> asked if we want the plethora of info he can provide.  I vote yes.

Hear, hear!