[asterisk-users] PRI auto-configure - continued from DEV list

[Tzafrir Cohen]

On Fri, Sep 12, 2008 at 09:53:48AM -0400, Bill Michaelson wrote:
> Tzafrir Cohen wrote:
> >
> >>>I usually configure the entire span of 24 channels (23 B + 1 D) and
> >>>only the turned up channels go into service.  This is good for a
> >>>couple of reasons.
> >>>      
> >
> >Also note that Zaptel will anyway reserve all the 24 (for T1) or 31 (for 
> >E1) Zaptel channels for the span. So the Zaptel channel numbers will not
> >change whether the span is fractional or full.
> >  
> What do you mean by "reserve"?  Seriously, I'm trying to get a good grasp.
> 
> I have always assumed that the signal presented by the Adtran TSU120e 
> appears as a full 24 channels.  But it was not clear to me how those 
> channels are transformed on the TDM side of the fork, if at all, by the 
> Adtran.  I supposed they might be remapped within the frames.  But 
> thinking (out loud) about it some more, I realize that remapping any of 
> the channel positions would likely invalidate some references embedded 
> within the Q.931 data stream on the D channel, vastly complicating the 
> process by requiring the Adtran to be aware of the content structure at 
> a protocol layer that would otherwise be unnecessary.  So I suppose that 
> it almost certainly does not remap these channels.  In fact, the nature 
> of this animal is such that I suppose for a PRI, each entire frame could 
> be passed to the TDM side unmodified and it would work just fine, with 
> the PBX ignore the IP channels.
> 
> And following this same line of reasoning, the zaptel code would have 
> little need to be told through its configuration which B channels are 
> available because such information is implicitly available via Q.931 - 
> and thus the channels specifications in zaptel.conf serve only to 
> restrict usage.  Have I got this right?

The configuration in zaptel.conf is applied to channels before layer 2
is up. 

So I guess your question could be rephrased as: do we really need to
specify 'bchan' in zaptel.conf? Any way to avoid that? I do need to
configure the D channel explicitly. But any way to discover the D
channels?

-- 
               Tzafrir Cohen
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