Re: [dhcwg] DDNS-DHCP [6]: Relationship between DNS TTL and DHCP lease length

I agree with Ted ... in fact, I had a conversation about
exactly this problem earlier today.

In theory, any application shouldn't depend on just DNS to
identify and establish contact with the correct endpoint
(server).  In practice, we have many such applications
deployed today, so we should be careful not to provide
another path for breakage...

- Ralph

At 12:40 PM 6/19/2003 -0500, Ted Lemon wrote:
>On Thursday 19 June 2003 06:19, Robert Elz wrote:
> > That is, reworded, to make sure my understanding is correct, the
> > problem to be avoided is having a name referring to an address that
> > is now to be assigned to a different name ?
> >
> > Who cares?
>
>Let's say machine X has an SMTP listener, and machine Y also has an SMTP
>listener.   Machine X gets an IP address, Z, from the DHCP server.   Then the
>owner of Machine X wanders away, leaving the lease active.   The lease
>expires, and then machine Y gets the address.   But there is still an A
>record for machine X pointing at IP address Z.   So now, machine Q connects
>to Z because of that A record, and tries to drop mail for X on Y.   Y will
>either bounce it immediately, or bounce it after it notices that the A record
>for X is pointing at it.   So we'd really like it if the time that the A
>record goes away and the time that the lease goes away are fairly close
>together, so that the chances of this happening are slim.
>
>Of course, I would say that this is a broken configuration anyway - you 
>really
>want to use protocols that verify who they're talking to if you have a mobile
>computer.   But that's the basis for caring about this sort of thing, and
>while I don't think we can completely solve the problem, it's worth setting
>things up to minimize the damage that occurs in cases like this.
>
>
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