[AusNOG] Simon Hackett's presentation from Comms Day yesterday - NBN fibre on copper prices

[Paul Brooks]

On 21/07/2013 1:06 PM, John Edwards wrote:
> I think this argument is a distraction when compared to the costs of a FTTH network.
> Today there are millions of Australian mobile subscribers bringing their own CPE to
> a data network on a shared medium that has a much greater surface area than 31
> neighbours, and everyone seems quite content, even preferring this situation over
> the certainty of a fixed line.
I'm not sure its comparable - a rogue mobile handset can still only block out a single
channel, other handsets in the immediate area will be using slightly different
frequencies to transmit and receive on, as allocated by the signalling. if the rogue
handset decided to ignore the frequency required by the basestation and used a
different channel, its unlikely to affect more than a few handsets/calls in the
immediate area. Plus, if it *was* doing a broad-spectrum transmission and blocking a
large number of calls, its battery would soon be flat.

> I am pretty sure the OLT can do something about this in 2013.
Nope - upstream on GPON every terminal transmits upstream on precisely the same
frequency, and the whole system relies on each one keeping to its timeslot so that
only a single terminal's upstream laser is active at any moment. One rogue ONT
activating its upstream laser out-of-sequence or on permanently will stomp over all
upstream comms from every other terminal on that splitter, blinding the OLT receiver -
and there's nothing the OLT can do about it.

The reason certification of ADSL CPE wasn't kept up is that a malfunctioning ADSL
modem only affects that customer and its dedicated DSLAM port - if your modem is
cactus, it doesn't hurt anyone but yourself, and it can't see anyone else's traffic so
there aren't the same security concerns. The security concerns with user-subverted
GPON CPE are significantly greater as each CPE sees every packet destined to all the
other CPE on the PON.

P.