At 9:57 PM -0400 5/2/02, Rob Austein wrote:
>I do claim that there's a difference between letting the client make
>the choice of which servers to talk to and having the routing system
>decide for the client.

Rob,

It's not the routing system "deciding" the choice of servers, it's the
human who causes the host routes to be injected into the routing system.
Instead of a human putting three DNS server addresses into a DHCP
database, a human configures the three DNS servers themselves to
advertise the (three different) host routes.  The client still gets to
choose among them, using whatever criteria it wishes.

If, instead of using three unicast addresses, we were to use a single
anycast address, that would indeed take away the decision process from
the clients.  The human who causes the host routes to be injected could,
if it were really important, statically prioritize the choice of server
by suitable assignment of route metrics (if using an IGP with a big
enough metric space).

A couple questions, from one who is expert in neither DNS nor DHCP:
Do the bulk of DHCP servers today provide more than one DNS server
address to each client?  If so, do "consumer-level" IP devices (PCs,
laptops, PDAs, cell phones, etc.) really make sophisticated choices
among those multiple DNS servers, or do they just pick one and then,
only if that one fails to respond, try another?

Steve

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