[asterisk-users] PRI: sometimes Asterisk drop calls

Steve Davies davies147 at gmail.com
Wed Sep 13 02:48:09 MST 2006

On 9/13/06, Giorgio Incantalupo <gincantalupo at fgasoftware.com> wrote:
> Hi Steve,
> I agree with you..telco knows better!
> If telco sends a ring on channel X  and asterisk has already used it,
> couldn't asterisk "shift" that call on another channel Y or it is
> obliged to answer on channel X?

The telco is "in charge" and is not asking, it is telling asterisk
that there is a call on channel X. If asterisk thinks this channel is
busy, then it is wrong because it must agree that a channel is busy
(SETUP/SETUP_ACK) with the telco first.

Probably, a now finished call was made on that channel, and some old
data in asterisk has not been cleaned-up when the call went away.

> In other words, if asterisk get a ring on channel 3 and channel 3 is in
> use, Asterisk should use channel 6 to answer the call and so connect
> channel 3 to 6. Isn't it? Or I have not correctly understood how telco
> and Asterisk speak between them?

BRI/PRI channels are like point to point data pipes, they cannot be
cross connected in that way. If the telco knows that channel 3 is busy
and channel 6 is available, it will just use channel 6 in the first

(I stand ready to be told I am wrong here)

> My PBX configuration is (may change due to upgrades):
> Debian Sarge 3.1 r0a
> asterisk-install: v6
> Asterisk:
> Zaptel: 1.2.6
> Libpri: 1.2.3
> BRI: install-misdn-mqueue 0.3.1-rc23

No obvious common factor then...


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