Dave
----- Original Message -----
From: Peter Court <pc@hotkey.net.au>
To: Chris Cook <ccook@tcworks.net>
Cc: Lanham Rattan <lanham@montrose.net>; <portmaster-modems@livingston.com>
Sent: Tuesday, November 23, 1999 11:03 PM
Subject: Re: (PMOD) 'Bad' Modems on PM3
>
> From: "Chris Cook" <ccook@tcworks.net>
>
>
> > 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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