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RE: survivability, rewriting
> I assume that in your example above you are considering the case where ISPA
> obtains addresses form ISP1 and ISPB from (ISP1 and ISP2), and ISPC from
> (ISP2 and ISP3), right?
> This implies that my site has 4 prefixes and in that case source address
> based routing is also required in ISPB and ISPC, correct?
That is what it would seem to imply; if you want to be able to use the source
address as a way to select between the "upper layer" ISPs to whom
the site isn't directly connected.
> But IMHO this is not how provider multihoming will be. IMHO ISPs will be
> able to get a /32 each one, especially those ISP that are multi-homed to
> multilpe upstream providers.
That is an address allocation policy issue and I don't think the answer
is that obvious. If anybody that says "I'm an ISP" can get a /32
then I can get one for my house since I provide network service for
all members of my family - hence I'm an ISP! :-)
To avoid giving everybody a /32 that asks there has to be some notion of
size taken into account in the policy. This means that a neighborhood
ISP might not be able to get a /32 - and for good reasons.
I think it would be shortsighted to assume that the word in which a multihoming
solution exists only consists of sites and of ISPs large enough to warrant a
/32 allocation. Perhaps that will be the future, but keeping the door open for
the existance of smaller ISPs would make a lot of sense to me.