Re: On the use of multiple PA prefixes or a single PI prefix for IPv6 multihoming

[marcelo bagnulo braun <marcelo@it.uc3m.es>]

El 22/10/2004, a las 14:28, Iljitsch van Beijnum escribió:

> On 22-sep-04, at 15:23, Cedric de Launois wrote:
>
> > CONCLUSIONS:
>
> > These observations show that, from a performance point of view, IPv6
> > multihomed stubs get benefits from the use of multiple PA prefixes and
> > should use them instead of a single PI prefix as in IPv4 today.
> > This study thus strongly encourages the IETF to pursue the development
> > of IPv6 multihoming solutions relying on the use of multiple PA
> > prefixes.
> > The use of such prefixes reduces the size of the BGP routing tables, 
> > but
> > also provides lower delays, more diverse Internet paths, which in turn
> > yields to better possiblities to balance the traffic load and to 
> > support
> > quality of service.
>
> "When considering dual-homed IPv6stubs, we see in fig. 13 or in fig. 
> 14 that the path diversity observed is already as good as the path 
> diversity of a 25-homed IPv4 stub."
>
> :-)
>
> But the question is: will this help us or hurt us? Basically, BGP 
> doesn't really know what the best path is, but it can usually detect 
> and avoid the bad ones. So you pretty much always get something 
> reasonable. With multi-address multihoming you get many more paths, 
> some of which are better than what BGP would have given you, but a lot 
> are worse. So the trick is to select the best one, or at least avoid 
> the bad ones. How do we do this?

Just a nit, note that in multihoming we are only selection addresses, 
not full paths.
This means that we are selecting the ingress and egress ISP of the 
source and destination sites, but that the interdomain path will be 
selected with other means i.e. BGP.

So we don't really need to know information about all the possible 
complete paths, just the ingress and egress parts of the path. I guess 
that this problem is more reduced and less ambitious than the general 
one.

Regards, marcelo

> Iljitsch
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