[dns-operations] EDNS issue

George Barwood george.barwood at blueyonder.co.uk
Fri Feb 25 23:05:06 UTC 2011

----- Original Message ----- 
From: "Mark Andrews" <marka at isc.org>
To: "George Barwood" <george.barwood at blueyonder.co.uk>
Cc: <frnkblk at iname.com>; <dns-operations at dns-oarc.net>
Sent: Friday, February 25, 2011 10:32 PM
Subject: Re: [dns-operations] EDNS issue

> radar.weather.gov has a 5 second ttl and edge-ext.lb.noaa.gov has
> a 30 second ttl so every thirty seconds named does a double fallback
> and that takes too long for some clients.

Ah right, I see now that lb.noaa.gov DNSKEY has a TTL of 30 seconds, and fragments.

My resolver is using a different strategy, it uses EDNS with a buffer size of 1400 bytes,
and falls back to TCP on truncation, avoiding fragmentation issues.

I'm not saying this is better but if the configuration issues prove insuperable, it might be a way forward.
If BIND repeatedly fails to receive responses > internet MTU, could it fall back to this strategy automatically?

I also note the publication of RFC6013, "TCP Cookie Transactions"  http://tools.ietf.org/search/rfc6013

Looks interesting.


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