[AusNOG] NBN Co Layer 2 vs. Layer 3 Services

[Lincoln Dale]

On 22/04/2010, at 11:18 AM, Mark Newton wrote:

>> At the moment there is a lot of talk of NBN and whether they are going to deliver Layer 2 or Layer 3 services.
> 
> If the NBN runs layer 3, then the choice of layer-3 protocols it's capable 
> of carrying will be limited to whatever protocols NBNCo chooses to deploy.

not sure that i agree with this.  where does L2 end and L3 begin?
case in point is DSL infrastructure today.  is it L2 (ATM, PPP) or is it L3 (IP to LAC/LNSs)?


> 
> If it runs layer-2, then gluing NBNCo services together to create Ethernet,
> IPv4, IPv6, MPLS, L2TP, etc retail offerings would be reasonably trivial, and as more
> protocols emerge in the future they'd be supportable without NBNCo needing
> to do anything.  I believe the politician-friendly word for that outcome is 
> "future-proof."

i'd disagree that choosing L3 rather than L2 precludes any options.
case in point is something i've been involved in creating: Cisco OTV (flash demo <http://bit.ly/c7y5XN>).
it provides L2-over-anything.

> 
> It's difficult to see what value NBNCo would be adding by getting involved in
> Layer-3.

many things are harder to achieve at L2 than they are at L3.   loop-free link-aggregation, >2 links and broadcast/multicast distribution without suboptimal trees, flooding or storm events in one place propagating to other locations, etc.

i'm not casting an opinion one way or another (either officially or personally) on what NBN should be technology wise.
whatever it is, i have no doubt that nimble smart operators will find ways of adding value beyond just moving bits.  just as they always have.

current arguments seem to be a bit like the bell-head vs net-head discussions of the 90s.  probably the same outcome(s) too.
http://www.wired.com/wired/archive/4.10/atm.html


cheers,

lincoln.