[asterisk-dev] Additional SNMP stats request

Justin Killen jkillen at allamericanasphalt.net
Mon Aug 20 13:43:41 CDT 2007

The system in question here is an automated call-in line.  People will
call in on a daily basis and put in their employee number, and the
system will tell them their schedule for the next day.  Wanting to know
the average length of calls and their frequency will better equip me
with information about the number of incoming lines I will need.

The metric of calls over the last 5 minutes is more geared toward
current mrtg implementations with network cards - there is a value for
the number of transmitted bytes.  E.g. you could check now and see that
there are 100 bytes transmitted, then check again in 5 minutes and see
that there are 200 bytes transmitted, then you could know that there was
100 bytes transmitted over that 5 minute span.  Taking this concept into
initiated calls, there could be a 'number of initiated calls' node that
could simply count incoming calls on a particular interface.  So it's
not the numbers themselves that are interesting, but rather the deltas.

For my application, the average call length (during testing) is under
two minutes, so the concurrent calls statistic doesn't give me enough
granularity over time.

As for the average time aspect, what' I'm really looking for is line
usage.  Similar to the above, if I know that the delta of my Zap
interface's UP status over the last 5 minutes is 2 minutes and 30
seconds, and I know I have had 5 calls since then, I can assume an
average call length of 30 seconds.

As for the CDR approach, I'm sure that there are other ways to gather
the information that I'm looking for - but I also know that there are a
LOT of different tools out there (mrtg, munin, cacti, openNMS, etc) that
already know how to interact with SNMP, so that seems like a logical
place (IMHO) to expose such data natively.

Justin Killen
-----Original Message-----
From: asterisk-dev-bounces at lists.digium.com
[mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of Steven
Sent: Monday, August 20, 2007 9:29 AM
To: Asterisk Developers Mailing List
Subject: Re: [asterisk-dev] Additional SNMP stats request

On Mon, 2007-08-20 at 08:50 -0700, Justin Killen wrote:
> All,
> I am trying to do some trend graphing of certain statistics within
> asterisk, but I'm having a hard time finding them.  My current
> implementation is an 8 port TDM card that users dial into from the
> PSTN, so I have Zap/1-1, Zap/2-1, Zap/3-1, etc.
> What I would like to be able to query is the total number of answered
> calls, and the current 'UP' time.  My eventual plan would be to hook
> these numbers into MRTG or something similar that would give me the
> number of calls over the last 5 minutes.  I have tried using the
> 'concurrent calls' node, but that misses a lot of information (e.g. I
> gather stats, a person calls and hangs up, then the stats gather
> again).
> So, in having these two nodes I would be able to deduce the average
> call length and true concurrent calls over time.

See I think that is the problem. The information you are looking for in
this last question is really best handled with the CDR not with SNMP.
You have a lot of things that might not be observable at the collection

Your metric of number of calls over the last 5 minutes seems like a
strange request when viewed from a operator of a asterisk system that
doesn't see very many calls under 5 minutes duration. Do you want
completed calls in the last 5 minutes, do you want call initializations
in the last 5 minutes, do you want something else? 

This is why I think your problem is actually 2 problems. SNMP captures
snapshots of the running system at collection times. Your question of
average call lengths would be handled by the cold hard CDR records.
Concurrent calls is a snapshot problem. I also at one time wrote a perl
app that created graphs from the CDRs to reproduce the data collection
Steven Critchfield <critch at basesys.com>

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