Best way to force a TC=1 response?
marka at isc.org
Tue May 26 23:28:47 UTC 2020
> On 27 May 2020, at 07:27, John Levine <johnl at iecc.com> wrote:
> In article <mailman.442.1590526210.942.bind-users at lists.isc.org> you write:
>> What's the best way to force an A query via UDP to return a TC=1 result:
>> a really long CNAME chain?
> I'd suggest lots of AAAA records. You could do it with A records but you'd
> need four times as many
Well ~2 times as many. Each additional A record requires 16 bytes and each
addition AAAA records requires 28 bytes. That means ~256 A records and ~146
AAAA records to force TCP with a 4096 byte UDP buffer size.
John’s example had 187 AAAA records.
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka at isc.org
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