Subject: RE: Proposed IPv6 DNS Discovery Requirements

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Mon, 29 Apr 2002 18:14:59 +0200

> At Fri, 26 Apr 2002 15:38:35 -0700, Bob Hinden wrote:
  > > 
  > > There are issues raised in solutions like this to insure that the 
  > > co-located services are adequately tied together.  For 
  > example in case of a 
  > > "DHCP server in the DNS server" the processes need to be 
  > tied together in a 
  > > manner that the DHCP process would not provide the 
  > address of the DNS 
  > > server if the DNS server process was down.  Or that the 
  > DHCP server not 
  > > provide the addresses for other DNS serves unless it 
  > knows that they are up 
  > > and available.
  > 
  > I suspect that upon close examination all solutions will have issues
  > along these lines (anycast certainly does).

=> How does anycast have this problem?
Specifically, how does the DNS discovery draft have 
this problem?

Hesham
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From: Rob Austein <[email-masked]>
Date: Mon, 29 Apr 2002 12:39:26 -0400

At Mon, 29 Apr 2002 18:14:59 +0200, Hesham Soliman wrote:
> 
> How does anycast have this problem?  Specifically, how does the DNS
> discovery draft have this problem?

Server location via anycast means that one is using the routing system
to keep track of the location of the DNS server.  That is, the
location of the DNS server is (somehow) injected into the routing
system, and the routing system is now responsible for handing out that
information to any client that wants to know.  If the server goes
down, moves, whatever, the DNS server becomes unreachable until the
routing system converges on a new useful answer, and how exactly does
the routing system know that the DNS server is gone, anyway?  Does the
DNS server now have to speak OSPFv3, or is there some human sitting at
a 24x7 desk somewhere waiting to push a button on failure, or what?

One could certainly build a system this way, but I'm not convinced
that it's more robust than the other options we've been discussing.
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From: Randy Bush <[email-masked]>
Date: Mon, 29 Apr 2002 22:37:18 +0200

magma is working on the subset of the problem of how the routing server
knows that an anycast service is up/down.

randy, not holding breath