> Peter Court wrote:
> >
> > > -----Original Message-----
> > > For a long time we have checked our PM3's for call
> > > success rates, as it seems that some 'modems' on the
> > > digital cards can go 'bad'. Normally about 95% of calls
> > > result in a carrier established.
> > >
>
> Are you sure that a percentage of this does not have to do with the
> users modems being defunct/crappy? I ran that script on our portmasters
> and get 90% as the average on about all of them. Does anyone else have
> interesting feedback on that script? Thanks for the info Peter.
>
> --
> Chris
The cause of failed carriers is a whole mixed bag of reasons including
User Modem, Local Loop, Telco, PRI interface and PM box and PM3 modem.
90% sounds low as we have averaged over 95-96% for a long time and
I've heard from Ascend and Cisco that this is a reasonable average
(at least here in Australia). This is not that different even in
our regional areas with more suspect local loops etc.
What we more importantly do with this is identify modems that are
substantially below the average. The local distributor was RMA'ing
any cards that had modems under 92% (for at least a 200 call sample).
We noticed that often a clutch of modems on the one card (not
necessarily sequential however) would often 'fail'. Rarely was it
one.
These seemed to stay faulty. If you moved the card the same modems
would stay bad (mostly). I'm retesting this now, after my discussions
with Ascend and Notel who had similar issues if they didnt reset their
modems. I've since discovered however that the PM3's reload the modem
DSP firmware before EVERY call to eliminate this sort of prob (ie.
flaky firmware in the DSP's).
A bad modem like this on a PM3 is VERY dangerous, since the PM allocates
modems sequentially. If for example modem 11 is failing often (eg 50%
failures)
then it will attract a large no of calls as it will be free often,
while the other modems hold longish sessions for normal users.
If you dont detect this you can have some very upset users quite
quickly. A bit like the old PSTN Rotaty issues with dud analog modems.
Other vendors make a big deal about diff allocation schemes for modems
to calls, including masking out bad ones automatically.
rgds .. Peter
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