[dns-operations] OARC's DNS Reply Size Test Server

Chris Thompson cet1 at cam.ac.uk
Wed Jul 8 21:35:32 UTC 2009

On Jul 8 2009, Duane Wessels wrote:

>Recent increases in DNSSEC deployment are exposing problems with
>DNS resolvers (clients) that cannot receive large responses.  DNS-OARC
>is pleased to announce the availability of a "DNS Reply Size Test
>Server." You can use a query tool such as dig to use this service:
>     $ dig +short rs.dns-oarc.net txt
>     rst.x4001.rs.dns-oarc.net.
>     rst.x3985.x4001.rs.dns-oarc.net.
>     rst.x4023.x3985.x4001.rs.dns-oarc.net.
>     " sent EDNS buffer size 4096"
>     " DNS reply size limit is at least 4023 bytes"

Maybe your documentation ought to point out that you will also see

   ;; Truncated, retrying in TCP mode.

as the dig-to-recursive-nameserver link needs to get 777-byte answers
through, i.e. specifying +bufsize=777 (or +vc) suppresses that warning.
(Yes, I do understand that isn't the path that is being tested!)

Chris Thompson               University of Cambridge Computing Service,
Email: cet1 at ucs.cam.ac.uk    New Museums Site, Cambridge CB2 3QH,
Phone: +44 1223 334715       United Kingdom.

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