[LINK] NBN Broadband Plan

[Paul Brooks]

Tom Worthington wrote:
> David Lochrin wrote:
>   
>> I don't fully understand what layered services NBN Co. is proposing 
>> for the NBN.  Can anyone clarify this point? ...
>>     
>
> The NBN architecture document is reasonably clear: 
> <http://www.nbnco.com.au/content/upload/files/NBN001_concept_paper_final.pdf>
>
> My summary is at: 
> <http://www.tomw.net.au/blog/2009/12/nbn-broadband-plan.html>
>   
and in turn, the NBN plan closely models the wholesale services 
discussion paper from Communications Alliance, found at:

http://www.commsalliance.com.au/__data/assets/pdf_file/0016/20725/NBN-Wholesale-Service-Definition-Framework-Ethernet-Release1-Dec-2009.pdf
>
>> Ethernet at layer-2 is also fine, assuming it's just a standard for 
>> local interfaces  ...
>>     
>
> My understanding is that NBN plans to provide a similar physical 
> interface for home users as current ADSL modems. That is there will be 
> an RJ-45 socket for a copper cable Ethernet connection. The home user 
> will not have an optical connection to the network. The protocols to be 
> used are less clear.
>   
This part is likely to depend on what is available from vendors I would 
think. Very few home users have CPE with optical GigE ports, so copper 
10/100/1000BaseT ports would seem to be the logical choice for 
residential and most small business purposes, and matches what is on the 
market today from PON equipment vendors. Larger corporations are likely 
to be supplied from point-to-point fibre rather than PON if they need 
more than several hundred Mbps in any case.
As far as protocol goes, NBN Co ar elooking at providing ethernet - that 
much is clear. Anything at a higher level is up to the service provider 
to specify.


>   
>> But all the other services mentioned need layer-3 services... QoS ...
>>     
>
> Yes, NBN Co. are planning four levels of QoS. But keep in mind that the 
> layers are just an abstraction, they are not necessarily hard and fast 
> boundaries in real services. Providing something like telephony or IPTV 
> is likely to require specifications at all layers.
>
> I think NBN are taking the right approach by not trying to do too much 
> specifying too soon. It is not clear at present what customers will use 
> the network for (assuming they want it at all). So there is no point 
> wasting effort on complex specifications for services which may never be 
> used.
>   
Tom - thats a somewhat different position to the first reaction at the 
ATUG seminar a few months back - good to see :-)

>   
>> And in Tom's point-5,NBN Co. agree that IPTV will need layer-3. ...
>>     
>
> IPTV has implications down to the hardware layer. Multicast can be
> implemented in hardware on a passive optical network, as the one optical
> signal is split and delivered to several homes. However, the protocol
> used over this many not permit multicast, for example PPPoE. It would be
> a shame if most of the network was filled with millions of copies of old
> episodes of "I Dream of Genie" being sent by some pay TV company to
> subscribers.
>   
This is absolutely true, and has implications for prospective service 
providers over the NBN infrastructure. The NBNCo ethernet service is 
currently proposed to be very simple Q-in-Q VLAN tagged tunnels as a 
form of point-to-point service, which should work well for normal 
broadband Internet services, corporate VPNs, and IP telephony 
applications. Both the NBNCo model and the Communications Alliance model 
provides for ethernet multicast outside the point-to-point framework, as 
an enabler for multicast IP services such as IPTV. At this stage (and 
this is something the NBNCo paper asks for feedback on) it will be up to 
another service provider to build a PPPoE/L2TP framework. However, these 
are the things NBNCo are looking for feedback on.

Paul.