[Asterisk-Dev] libpri ISDN features

[Peter Svensson]

On Thu, 25 Nov 2004, Andrew Kohlsmith wrote:

> On November 25, 2004 09:30 am, Steve Underwood wrote:
> > Q.921 fully specifies the link protocol.
> > Q.931 fully specifies the messages, and the call states that relate to
> > them.
> >
> > How useless is that? :-\ What they don't tell you is whether any of
> > these messages, or fields within messages, will actually exist in any
> > particular network. You need to look at consult ETSI, or national
> > documents to find out about that.
> 
> I could not find a pdf on their site that gave me the "this is what's 
> travelling over the wire, this is what each structure looks like and what the 
> bits mean" -- only the high level hand waving.

Hm, I have always found the itu specs to contain everything. Just not in 
one place. Then again, it is a layered protocol stack. Anyway, q.921 and 
q.931 does define most things in detail. 

Telephony is quite complex and as a consequence you need an understanding 
of a lot of different standards. What you are asking for is sort of like 
asking what standard describes the Internet, at bit detail up to dns/ssh 
etc.

Peter