Re: A new spin on multihoming: multihoming classes.

[Peter Tattam <peter@jazz-1.trumpet.com.au>]

On Sun, 9 Sep 2001, Iljitsch van Beijnum wrote:

> On Sun, 9 Sep 2001, Peter Tattam wrote:
> 
> > Finally I might add that I have to concede there is one fundamental flaw in the
> > host based or DNS based solutions to MH and that was eloquently pointed out by
> > someone else.  DNS needs routing so routing can't depend on DNS which means we
> > can't use it as it is currently implemented, primarily because DNS is agnostic
> > towards routing conditions.
> 
> Eloquent, but wrong. In the multi-address multihoming (MAMH) proposals
> we've seen lately, there are never changes to single homed routing. So as
> long as the domain name system only depends on single homed routing, there
> is no problem. Also, no actual forwarding decisions depend on DNS
> information, it is only used to find out addresses associated with a
> hostname (or possibly with another address). This is hardly a new thing
> for the DNS.


Umm..  There is a pathological situation where a DNS server within the site may
not be accessible if that DNS server were only visible from a single address
prefix.  A secondary DNS might be visible at another address range but may not
be for similar reasons as the primary netowrk fault. You could multi home the
SOA & NS entries but it might complicate lookups - however you are implying
this is not done. The site could be black holed from the DNS system if it were
relying on a single homing their DNS servers, even if it were visible via other
prefixes.  It can be avoided by strategic placement of secondary servers, but
in practice it might prove difficult.

What I'm saying is that the DNS needs multihoming to work for it to be
fully reliable.  Do you still disagree?  Show me what I'm missing here.

I'll respond to the rest of your message when I've digested it.

Peter

--
Peter R. Tattam                            peter@trumpet.com
Managing Director,    Trumpet Software International Pty Ltd
Hobart, Australia,  Ph. +61-3-6245-0220,  Fax +61-3-62450210