Re: [RRG] DNS Map: Mapping Resolution Combining Pull/Push Advantages

["William Herrin" <bill@herrin.us>]

On Tue, Feb 26, 2008 at 3:57 AM, Christian Vogt
<christian.vogt@nomadiclab.com> wrote:
>  I would like to propose DNS Map [1], a DNS-based mapping resolution
>  system that combines advantages of push and pull systems.  DNS Map
>
>  [1] http://users.piuha.net/chvogt/pub/2008/vogt-2008-dns-map.pdf
>      or via RRG homepage

Hi Christian,

Four comments:

1. Fetching the map alongside the the hostname presents a nasty cache
poisoning problem. The hostname response is not necessarily coming
from a server authoritative for the address map and the resolver has
no way to know the difference without performing additional lookups.

2. Prefetching the map in this manner assumes that the ITR uses the
same DNS resolver as the client. Unless the ITR is on the client, that
could get hairy fast.

3. Typical behavior of DNS resolvers assume that equal-priority
records can be reordered at will and they often do. You're asking for
the map records to be implemented in a way that is inconsistent with
that behavior.

4. If you haven't already read TRRP, you should:
http://bill.herrin.us/network/trrp.html . TRRP uses DNS in much the
way you propose and has already ground through a lot of the problems
you're likely to encounter.

Regards,
Bill Herrin



-- 
William D. Herrin                  herrin@dirtside.com  bill@herrin.us
3005 Crane Dr.                        Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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