Re: [DNSOP] Possible slower response with minimization

[Tim Wicinski <[e-mail]>]

I think part of the work on qname-minimization will spend some time 
studying performance, as well as operational issues as Peter brought up.

It could very well be that what Peter pointed out will be true and there 
are operational issues that could cause acceptance.  But part of this 
work will be to understand and document these effects, correct?

tim
(finally back home and catching up)


On 10/20/14 5:03 PM, Bob Harold wrote:
> I support the idea of qname minimization, but I think there is a common
> case where it will cause additional DNS round trips, slowing the
> response and increasing the number of packets and queries the servers
> must handle.
>
> Consider “www.host.group.department.example.com
> <http://www.host.group.department.example.com>” where the company’s
> servers are authoritative for the zones:
>
> example.com <http://example.com>
> department.example.com <http://department.example.com>
> group.department.example.com <http://group.department.example.com>
>
> Without minimization (typical today):
>
> 1. Query root for “www.host.group.department.example.com
> <http://www.host.group.department.example.com>”, get list of “com” servers.
> 2. Query a com server for “www.host.group.department.example.com
> <http://www.host.group.department.example.com>”, get list of
> “example.com <http://example.com>” servers.
> 3. Query an example.com <http://example.com> server for
> “www.host.group.department.example.com
> <http://www.host.group.department.example.com>”, get answer.
>
> With minimization:
>
> 1. Query root for “com”, get list of “com” servers.
> 2. Query a com server for “example.com <http://example.com>”, get list
> of “example.com <http://example.com>” servers.
> 3. Query an example.com <http://example.com> server for
> “department.example.com <http://department.example.com>”, get list of
> “department.example.com <http://department.example.com>” servers (which
> happens to be the same as the list of “example.com <http://example.com>”
> servers).
> 4. Query a “department.example.com <http://department.example.com>”
> server (likely the same server as step 3) for
> “group.department.example.com <http://group.department.example.com>”,
> get list of “group.department.example.com
> <http://group.department.example.com>” servers.
> 5. Query a “group.department.example.com
> <http://group.department.example.com>” server for
> “host.group.example.com <http://host.group.example.com>”, get probably
> just an A and/or AAAA record, indicating there is no zone cut at that level.
> 6. Query a “group.department.example.com
> <http://group.department.example.com>” server for
> “www.host.group.department.example.com
> <http://www.host.group.department.example.com>”, get answer.
>
> Note that it takes twice as many queries, and each depends on the
> previous, so it is twice as many round trips.
>
> I realize that caching will reduce the extra queries in many cases, but
> can we estimate the impact of this somehow, to determine if it is
> significant?
>
> --
>
> Bob Harold
>
> DNS hostmaster, University of Michigan
>
>
>
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