mulcast assignments

Thu May 3 22:44:23 UTC 2012

On Thu, May 3, 2012 at 3:32 PM, Nick Hilliard <nick at foobar.org> wrote:
> On 03/05/2012 21:00, Greg Shepherd wrote:
>> Sure, but GLOP predated SSM, and was really only an interim fix for
>> the presumed need of mcast address assignments. GLOP only gives you a
>> /24 for each ASN where SSM gives you a /8 for every unique unicast
>> address you have along with vastly superior security and network
>> simplicity.
>
> SSM is indeed a lot simpler and better than GLOP in every conceivable way -
> except vendor support.  It needs igmpv3 on all intermediate devices and SSM
> support on the client device.  All major desktop operating systems now have
> SSM support (OS/X since 10.7/Lion), but there is still lots of older
> hardware which either doesn't support igmpv3 or else only supports it in a
> very primitive fashion.  This can lead to Unexpected Behaviour in naive
> roll-outs.

I haven't seen a piece of network gear without SSM support in a very
long time. The weak link is the applications. It was the OS stacks but
that's finally caught up - it only took it 10 years...

The weakest link is simply multicast deployment - if it's not
everywhere it has little use. That's what AMT is promising to fix. And
with AMT comes the opportunity to bring SSM to non-SSM-capable apps if
it is implemented correctly.

Greg

> Nick
>