[AusNOG] Discussion point: Why aren't the NBNCo tails symmetric in speed?

Tristram Cheer tristram.cheer at ubergroup.co.nz
Wed Apr 9 07:24:20 EST 2014


I can’t speak for the NBN but the UFB in NZ was async to avoid last mile oversubscription given GPON’s 2.4/1.2gbit split. To offer 100/100 or 50/50 would either oversubscribe the GPON or require reducing the 24:1 split

From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Skeeve Stevens
Sent: Wednesday, 9 April 2014 8:39 a.m.
To: Damian Guppy
Cc: ausnog at ausnog.net
Subject: Re: [AusNOG] Discussion point: Why aren't the NBNCo tails symmetric in speed?

Yes, but how does that matter?

Google Fiber also uses GPON and they are delivering 1G/1G (see: http://networkmatter.com/2014/02/27/google-fibers-brewing-little-secret-exposed-its-gpon/)

While GPON may be asymmetrical for the end tail, the speeds it can achieve are clearly symmetrical in nature... and the speeds that can be achieved means that there is no reason at all that 100/100, 50/50, 25/25 or 12/12 can't be achieved - with no material impact to the network utilisation or cost.

Still sounds like an artificial restriction to me.

...Skeeve

Skeeve Stevens - eintellego Networks Pty Ltd
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On Wed, Apr 9, 2014 at 2:02 AM, Damian Guppy <the.damo at gmail.com<mailto:the.damo at gmail.com>> wrote:
NBN is built on GPON tech, which is normally asymmetrical. I believe it is ITU-T G.984 which supports 2.488Gbit/s down and 1.244Git/s up.  Most home users have an asymmetrical data requirement, so it makes sense to divide up the available spectrum with a bias to downstream. Same reason ADSL is used and is asymmetrical even through there are SDSL specs out there.

--Damian

On Mon, Apr 7, 2014 at 6:52 PM, Skeeve Stevens <skeeve+ausnog at eintellegonetworks.com<mailto:skeeve+ausnog at eintellegonetworks.com>> wrote:
Hey all,

I am sure this will spurn a healthy discussion... perhaps with conflicting views...

But I was wondering the other day 'Why aren't NBNCo tails sold as symmetric speeds?'

Considering:

- The transit the RSP buys is symmetric (nearly always)
- The network core of the RSP is symmetric
- The handoff to either NBNCo or an aggregator (and then NBNCo) is pretty much always symmetric
- The PoI's core is symmetric
- The fibre to the home is symmetric capable
- The NTU is just ethernet - symmetric
- Anything they plug into the NTU is symmetrical - ethernet

Google Fibre in the US is 1G/1G in speeds...

So... unless I am missing something obvious (always possible)... Why are NBNCo tails not sold as symmetrical speeds?

I am not sure why there is this artificial design in these products to make them asymmetric.  There doesn't seem to be any gain by doing this that I can think of.

Gone are the days of DSL like speeds and unbalanced design... even ATM was symmetrical.

Keen for peoples opinions.

...Skeeve

Skeeve Stevens - eintellego Networks Pty Ltd
skeeve at eintellegonetworks.com<mailto:skeeve at eintellegonetworks.com> ; www.eintellegonetworks.com<http://www.eintellegonetworks.com/>

Phone: 1300 239 038<tel:1300%20239%20038>; Cell +61 (0)414 753 383<tel:%2B61%20%280%29414%20753%20383> ; skype://skeeve

facebook.com/eintellegonetworks<http://facebook.com/eintellegonetworks> ; linkedin.com/in/skeeve<http://linkedin.com/in/skeeve>

twitter.com/theispguy<http://twitter.com/theispguy> ; blog: www.theispguy.com<http://www.theispguy.com/>

[http://eintellegonetworks.com/logos/ein09.png]

The Experts Who The Experts Call
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--

Tristram Cheer
Network Architect - Most problems are the result of previous solutions...

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