Re: Re: ISP scenarios comments (multicast)

[Pekka Savola <pekkas@netcore.fi>]

On Thu, 19 Sep 2002, bkhabs wrote:
> >Ok; this is still a bit problematic with the one PIM domain requirement.. 
> >:-/
> 
> I don't think it is problematic when you consider the overhead that
> would have to occur in order to support PIM domain != site-local domain.
> 
> The major problem is that PIM messages are mostly sent hop-by-hop with
> IP addresses in the payload.  So, the Bootstrap message is transmitted
> hop-by-hop using the All-PIM-Routers link-local multicast address.  But
> the BSR address is in the payload.  That means that a site-local border
> router would have to recognize the Bootstrap message, parse into the
> PIM payload and check to see if the BSR-Address was a site-local.
> 
> In this case, I prefer simplicity.  Let pim domain == site-domain.

I agree with the simplicity -- but the problem I was referring to was due 
to the fact that for all practical purposes, currently there can only be 
one PIM domain.  That limits the applicability of multicast quite a bit.

For one perspective, look at one PIM-domain at:

http://sem2.renater.fr/m6bone/

Multicast works -- kinda.

> >This might be an interesting point to develop more.  It's quite possible
> >if we can hard-code assumptions about address assignment for the RP there. 
> 
> >Possibly through an additional bit flag in the address. This would have to
> >go to the PIM implementation then, though.
> 
> You can't encode the RP in the field.  

Which field?  Destination address could include the address of the RP,
with some rather strict assumptions.

> But, a new RP discovery mechanism
> could utilize the prefix information to know where to look for the RP.

That too.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords