At 02:43 AM 10/28/02, Markku Savela wrote:
> When a multi-sited implementation gets site-local addresses from
> the DNS (assuming that it runs two-faced DNS and returns site-locals),
> how will the multi-sited host know which site the addresses are in?
My guess, and tentative implementation is that the resolver library
completes the scope id to the address using the interface from which
the DNS reply came in.
I keep winding-up back here, myself, but it isn't really a satisfactory
answer for several reasons:
(1) A multi-sited node might receive different sets of
addresses in response to the same query, based on
which site's DNS server was tried first. There is
no provision to try another DNS server if the first
one succeeds, so there is no way to be sure you've
gotten all of the available addresses to reach a
node.
(2) This solution presumes some relationship between the
routing hierarchy and the organization of DNS servers.
For example, it assumes that I will use the DNS
server that is configured with two-faced DNS for my
site.
(3) The two-faced DNS solution requires that we store routing
information in a DNS configuration file. This creates
another way for the network to break when routing
information changes.
(4) If the DNS requests are done via global addresses, I am
not sure that it is safe to assume that the results
will always come back through the correct interface.
What if there were a partition in Site1, but parts of
Site1 could still reach other parts of Site1 using
global addresses, by sending across the global
Internet. Is that possible?
Anyway, we'd certainly have to document the "two-faced" DNS concept
and describe this solution in more detail before I'd feel comfortable
counting on it to work.
Margaret
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