Re: [Doh] [Ext] a tad confused on response sizes

Paul Hoffman <paul.hoffman@icann.org> Tue, 05 June 2018 22:10 UTC

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From: Paul Hoffman <paul.hoffman@icann.org>
To: Tony Finch <dot@dotat.at>
CC: "doh@ietf.org" <doh@ietf.org>
Thread-Topic: [Doh] [Ext] a tad confused on response sizes
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Date: Tue, 5 Jun 2018 22:10:33 +0000
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Subject: Re: [Doh] [Ext] a tad confused on response sizes
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On Jun 5, 2018, at 1:26 PM, Tony Finch <dot@dotat.at>; wrote:
> 
> Star Brilliant <m13253@hotmail.com>; wrote:
>> 
>> In other words, a DoH with TC bit can happen, and that's a common error.
>> (Not as common as an unplugged network cable, but actually happens
>> really frequently on a busy recursion server.)
> 
> I would be interested to know of a query that produces a TC response over
> TCP.

Resolver 1 sends a query to a Resolver 2 (who allows forwarding) over TCP. Resolver 2 asks an authoritative,  gets a response with TC bit set on, tries on TCP, and gets a failure on TCP. Resolver 2 should send the partial answer it got over UDP to Resolver 1. That answer to Resolver 1 should have the TC bit set on, or not, depending on what you think that RFC 1035 "implies".

--Paul Hoffman