DH> Since then, some careful politicking has turned up an admission from a
DH> senior Telstra manager that there _is_ dynamic line bandwidth sharing
DH> (read limiting) hardware now fitted on high traffic trunks and exchanges.

DH> FNQ is a low enough traffic area that the equipment hasn't been fitted..:-(

RS> Cant be that, coz Dave Drummonds line is JUST as immaculate. One common
RS> feature of BOTH that FNQ line and Daves is that they are both within
RS> spitting distance of the exchange itself. Bet thats not a coincidence.

RS> AND we have LOTS of duplicated session stats from people
RS> calling Pauls system with a variety of modems at his end,
RS> with no evidence of ANY real variability in the stats at
RS> all, which is a bit hard to reconcile with the story about
RS> 'dynamic line bandwidth sharing', particularly as his end in
RS> Sydney presumably qualifys as 'high traffic trunks and exchanges'

DH> Fair enough.  Then we take the "all" with the same size grain
DH> of salt as we do the other information packages ex Telstra.

Or we can say that we dont have ANY evidence of it in measured sessions,
and that now that the absolute vast bulk of the inter exchange links are
fibre optic, with VAST surplus bandwidth, the proposition is hard to credit.

Maybe he actually meant that it can happen at times when for some reason
the inter exchange link is temporarily not yet upgraded or something.

RS> And a careful look at the Courier ATY11 line probe stats shows no
RS> sign of that claimed bandwidth limitation at all. What you can see
RS> with the worse lines like Bill Grimsleys home line and Poes is a rather
RS> pronounced slope of the entire bit of the curve which is horizontal
RS> with Daves, more loss at higher freqs, JUST what you would expect
RS> to see due to the physical cable run between the exchange and the
RS> modem itself when its rather long, rather elderly, and thinner wire.

DH> Doesn't explain my particular hobgoblins.

Yes, but you have said it affect ONE line and not another, and that
it has a very pronounced asymmetry too. Its MUCH more likely to be
some fault condition and not routine dynamic bandwidth sharing at all.

DH> I get sudden disconnects - classical effects that used to plague
DH> V.FC in the early days.  The line checks out wide band and low noise.

If its wideband, it cant be 'dynamic bandwidth
sharing 'pinching your bandwidth can it ?

RS> You can however clearly see a completely different effect
RS> on the calls to the US, which do appear to be more likely
RS> to be due to that sort of thing on bandwidth.

DH> Word currently is that they've "fixed" the fax processors.

Thats a separate issue to whether the overseas calls have always
been measurably different to the ones within Australia tho.

DH> I've been deluging Frank Nitzche with logs, complete with bandwidth
DH> measurement sets.  The "fault present" condition is a
horror.  We'll see.

DH> Could well be some digital sync problem.

Yeah, it sure smells like some fault rather than being a normal network
thing, most obviously because no one else but you is reporting anything
remotely like it and its on just one of your lines. Particularly with
the extremely pronounced asymmetry in the fault condition.

The other people who have problems have problems where, when you
look at the ATY11 graph you are amazed they get what they do achieve.

Bills got one for an overseas call which has an immense cliff where it is
trundling along at 40db and then falls over the cliff to 93 db and stays there
at 3150Hz and above. That clearly must be some brickwall filter on that call.

DH> Mind you - management doesn't know beans about digital sync -
DH> but line capacity planning they -do- know at least a bit about.

Yeah, it can apparently be a problem convincing them its the problem.

DH> I tend to believe that the report was at least
DH> believed by the source. (Credibility level??? well...)

Oh sure, he likely believes it.
@EOT:

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