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On 17/06/2010 11:22 AM, Tim McCullagh wrote:
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----- Original Message ----- </div>
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<a moz-do-not-send="true" title="JLindsay@internode.com.au"
href="mailto:JLindsay@internode.com.au">John Lindsay</a> </div>
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<a moz-do-not-send="true" title="ausnog@ausnog.net"
href="mailto:ausnog@ausnog.net">ausnog@ausnog.net</a> </div>
<div
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Thursday, June 17, 2010 9:59 AM</div>
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Re: [AusNOG] Why not Symmetric ingress and egress?</div>
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<div>There are also some limits in the FTTH network architecture
that mean there is less total bandwidth in the back channel.</div>
<div> </div>
<div><font size="2" face="Arial"><strong>Not necessarily, that may
be true for GPON which is what NBN is going to use, but GEPON equipment
has no such limitation. Even for GPON it can hardly be used as an
excuse to have a 25 down 5 MB up etc. Unfortunately with NBN we will
be locked into GPON. </strong></font></div>
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Which variant of GEPON did you have in mind Tim? 802.3ah GEPON provides
1.25 Gbps in both upstream and downstream directions. GPON has the same
upstream capacity, with double the downstream capacity. Thats hardly
"no such limitation".<br>
<br>
As far as speeds and up/down ratios for individual services go, you
have to look at the RSP's choice of packaging more than the choice of
PON technology - and also recognise that the RSP (not NBN) has to
backhaul all the traffic over the water to Tasmania which aint cheap,
so may have very good reasons to currently offer a variety of speeds,
at a variety of price points, to ensure there is something to suit
everybody's budget.<br>
<br>
<blockquote cite="mid:002701cb0dbb$8dc9f720$6500a8c0@hal" type="cite">
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<div><strong><font size="2" face="Arial">Some of the issues has
come down to the choice of equipment vendors. As always in choosing a
vendor big is not always better. </font></strong></div>
<div><strong></strong> </div>
<div><strong><font size="2" face="Arial">Much of the equipment
deployed (presently) in Australia is not the same vendor as NBNs
choice. Other than Telstra, most deploy Wave7 / Enablence kit in either
GPON or GEPON or both varieties. Then there is some hills equipment.
Personally I don't see why a GPON solution was chosen over a GEPON
solution other than that the GPON vendor was familiar to the powers to
be at NBN. In fact I think it was a dumb choice, but that is just my
2 bobs worth. This is all really back to the future stuff. I wonder
how long it will take to hear the cries from the public re lack of
competition and choice re NBN, in the same way as happened in the
1970s. </font></strong></div>
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<br>
GPON provides twice the downstream capacity, the same upstream
capacity, as GEPON. On the other hand, GEPON gear may be cheaper than
GPON gear. GPON supports TDM services for legacy migration, GEPON does
not. These are tradeoffs which will come out in the selection RFP
process. NBNCo hasn't made a vendor choice yet for the main mainland
rollout as far as I know, perhaps you have better inside insight.<br>
<br>
<br>
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<div><strong><font size="2" face="Arial">It strikes me that there
are too many so called experts that have never done any FTTH
deployments that simply do not understand the issues. Fibre is sexy so
we should do it stuff, when fibre should be driven by a business case.
</font></strong></div>
<div><strong></strong> </div>
<div><strong><font size="2" face="Arial">I really do pity the 55%
of homes that are going to get aerial FTTH, talk about recipe for
disaster. It isn't the same as copper, you can't just scotch lock a
bit into it when it gets brought down by wind, fires trucks etc. For
those that want to remind me about backhoe fade, yes that happens in
one spot. In the case of fire and wind it will happen in many spots,
over large geographic areas. Trying to reconstruct quickly will take
time. You cant run fibre acress a driveway to effect quick repairs
like copper. I could go on but I am already off topic.</font><br>
</strong></div>
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I'm confused by this Tim - you first say that fibre should be driven by
a business case, then in the next breath argue for underground
deployment which is significantly more expensive than overhead. You
worry about wind, and ignore that aerial fibre cable is lighter than
aerial copper cable, and less affected by strong wind. You worry about
overhead cabling and bushfires, ignoring that most suburban areas
aren't close to any bush, and haven't seen bushfires for a hundred
years - and in bushfire-prone rural areas, fibre is usually ploughed
safely underground. In fact, all the downsides with overhead cabling
you raise - which are all valid concerns by the way - apply equally to
copper cables as well as fibre cables, so overhead fibre will not be
any less reliable than the current overhead copper network.<br>
<br>
The two countries with highest FTTP deployment are Sth Korea and Japan.
Over 95% of Japan's FTTP deployment is on overhead cable. They've been
doing it for a while now, I'm happy to call a few of them experts.<br>
<br>
I realise your main point is that a fibre core takes longer to repair
than a copper pair - which in an emergency can be quickly twisted or
soldered to a new cable segment - but it also only takes 3 minutes to
put on a couple of field-installable fibre terminations and plug them
into a joiner. Quicker than waiting for the soldering iron to heat up.<br>
<br>
Its not a black-and-white, right-or-wrong issue. There will be areas
where overhead makes more sense than underground, and areas where the
opposite is true. You use the most appropriate construction technique
to suit the local conditions, which vary enormously across the country.<br>
<br>
BTW Tim, which FTTH deployments have you done, and which GPON and GEPON
gear did they each use??<br>
<br>
Paul.<br>
<br>
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