RE: Re: [magma] RE: [MBONED] FW: WGLC:draft-ietf-behave-multicast-06.txt

> > It is an idea regarding the BEHAVE Internet Draft and how 
> > the multicast
> > NAPT can allow outside multicast routers to uniquely 
> > identify different
> > multicast SSM channels (S,G) coming from inside interfaces 
> > in the case
> > two inside interfaces use the same multicast group.
> 
> How prevalent do people expect the scenario of a SSM sender being
> located behind a NAPT?

Not very prevalent with today's broadcast model for SSM where
the broadcaster is the video service provider.

However, we don't want to encourage proliferation of NATs which
are compliant with a BCP that do not allow SSM senders behind
those NATs.  With today's bandwidth to the home we might 
consider someone running a 'radio station' from behind a NAT.
With tomorrow's bandwidth, we might considering someone doing
video sharing to their family from behind a NAT.  Hard to say;
I would like to do this once if we know how to do it today.

> > In the BEHAVE draft, REQ-4, if there is a host on the 
> > inside interface
> > sending UDP packets to a multicast group, the NAPT can 
> > change the source
> > address and the port but not the multicast group address. 
> > In this way, I
> > think the outside routers can not differentiate the two 
> > channels because
> > they have the same source (the public interface) and the 
> > same multicast
> > group address.
> > 
> 
> Is it possible for the NAPT to have multiple external addresses to use
> as source addresses?

Some NAPTs do that, yes -- larger ones used by service providers
and by enterprises.  Your traditional residential-class NAPT doesn't
do that, though.

> > Allowing the NAPT to change the multicast group address in 
> > the case two
> > sender behind the NAPT use the same group address in a 
> > similar way the
> > NATP changes a UDP port is a possible solution. There are other
> > possibilities.
> 
> From the global perspective, how does a receiver outside the 
> NAPT know the (S,G) combination to join?

-d


> Regards,
> Brian
> 
> 
> 
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