asterisk users - Feb 2010 - How does holdtime get calculated for queues

I had a customer ask me this question today, and I was surprised to say I
didn't have an exact answer for them.  They have a relatively small support
queue for their business (three agents, and rarely more than one person in
line at any given time in the queue, if all agents are on a call),  Their
support calls can range anywhere from 30 seconds to 30 minutes.
Occasionally, they'll get four or five calls in a short time span, and the
first three that are answered may end up being rather long.  The people in
line are listening to hold music and hearing the periodic hold announcements
and estimated wait times (you are currently caller number 2 in line, your
estimated wait time is ....).  The complaint they're receiving is that the
estimated hold time tends to jump around a bit - the example I was given was
that a caller was told when they entered the queue, they were currently
caller number 2 and the estimated hold time was less than 2 minutes.  The
caller waited upwards of 10 minutes, and then hung up when the estimated
wait time announcement told them the wait time was 8 more minutes.

This is on a queue with a 30 minute wait time (the customer specifically
asked for this for all of their queues, so that's not changing).  After the
timeout limit is reached (i.e the command is Queue(support,,,,1800)), the
dialplan jumps to voicemail.

So, how does asterisk calculate holdtime for queues?  Why would it go up the
longer a caller is in line?  Where does it determine the initial wait time,
etc?

-- 
Thanks,
--Warren Selby
http://www.selbytech.com
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On 02/17/10 03:39, Warren Selby wrote:
> I had a customer ask me this question today, and I was surprised to
> say I didn't have an exact answer for them.  They have a relatively
> small support queue for their business (three agents, and rarely more
> than one person in line at any given time in the queue, if all agents
> are on a call),  Their support calls can range anywhere from 30
> seconds to 30 minutes.  Occasionally, they'll get four or five calls
> in a short time span, and the first three that are answered may end up
> being rather long.  The people in line are listening to hold music and
> hearing the periodic hold announcements and estimated wait times (you
> are currently caller number 2 in line, your estimated wait time is
> ....).  The complaint they're receiving is that the estimated hold
> time tends to jump around a bit - the example I was given was that a
> caller was told when they entered the queue, they were currently
> caller number 2 and the estimated hold time was less than 2 minutes. 
> The caller waited upwards of 10 minutes, and then hung up when the
> estimated wait time announcement told them the wait time was 8 more
> minutes.
I have a call centre that is very similar to yours - two or three
operators, normally minimal hold times with occasional busy times
(although in this case, it's when there's a special event on that the
volume of calls pick up rather than the length of each call) and found
that Asterisk's estimated hold time simply wasn't accurate enough.  In
my situation, I simply disabled the hold time and the complaints about
inaccurate wait times were replaced by lots of praise for the mere fact
that they were told "your call is number 3 in line".

The problem seems to be when Asterisk is used to long periods of next to
no waiting time - something you can't really fault Asterisk for since
it's not psychic.  I found that after 10 or 15 minutes and a half dozen
calls, the wait time became pretty accurate and stayed that way until
the queue emptied again.  It may be for the type of queues that we're
talking about here that trying to calculate hold times simply isn't
feasible.