[LINK] Congestion (was Re: NBN to cost 24 times South Korea's faster network, says research body)

[George Bray]

Thanks Richard.

So it's the switches that have knowledge about the MAC addresses to
send to? How is this managed without the equivalent of SAP for
discovery?

> My question: is there a reason that multicast is necessary for NBN Co?
> Couldn't the retail ISPs simply use IP multicast themselves?

For resources that need to go everywhere in AU, I'd say NBN Co would
need some sort of multicast.  It would be nice if all of the
free-to-air TV channels from all over the country were available to
all users on all RSPs. Seems rather silly for the broadcasters to have
retransmission agreements with individual providers when a national
backbone agreement (and appropriate amendments to the act) would serve
everyone.

George


On Sun, Feb 20, 2011 at 4:54 PM, Richard Chirgwin
<rchirgwin at ozemail.com.au> wrote:
> George, I'll pick this up, since it was my poor memory that gave this to
> IP multicast instead of Ethernet multicast.
>
> Simple answer - one happens at layer 2, the other at layer 3.
>
> Longer simplified answer.
>
> Ethernet multicast is based on MAC addresses - so the same incoming
> Ethernet frame gets switched to multiple MAC addresses.
>
> IP multicast works in routers - the same TCP/IP packet gets routed to
> multiple IP addresses.
>
> It used to be that Ethernet (switching) would handle the same thing
> faster than IP (routing), but I guess that gap is narrowed somewhat!
>
> In the case of the NBN - still sticking to a basic explanation that
> others can expand upon if they wish - it's because it keeps the roles
> clearly delineated. NBN Co is not supposed to route traffic; that's the
> job of the retail ISPs.
>
> My question: is there a reason that multicast is necessary for NBN Co?
> Couldn't the retail ISPs simply use IP multicast themselves?
>
> RC
>
> On 20/02/11 3:50 PM, George Bray wrote:
>> On Mon, Feb 14, 2011 at 10:39 AM, Paul Brooks
>> <pbrooks-link at layer10.com.au>  wrote:
>>
>>> Note also that as far as the NBN is concerned, 'multicast' is ethernet multicast, not
>>> IP multicast (although the two layers might need to be connected), and the multicast
>>> capability might well be unidirectional - from the PoI towards the user, not from
>>> user-to-user.
>>>
>>> Paul
>> Paul, what's the difference between ethernet multicast and IP multicast?
>>
>> George
>> _______________________________________________
>> Link mailing list
>> Link at mailman.anu.edu.au
>> http://mailman.anu.edu.au/mailman/listinfo/link
>>
>
>
> _______________________________________________
> Link mailing list
> Link at mailman.anu.edu.au
> http://mailman.anu.edu.au/mailman/listinfo/link
>