response case in-sensitivity?

Barry Margolin barmar at
Thu Jul 30 14:46:50 UTC 2015

In article <mailman.2375.1438232213.26362.bind-users at>,
 Mark Andrews <marka at> wrote:

> In message <23DEE83F-7476-432B-92B9-F8D34D617C2F at>, Mathew Ian Eis 
> writes:
> > Howdy BIND,
> > 
> > Weve been troubleshooting an issue with iOS print discovery using DNS-SD 
> > for the last several weeks. We made a little bit of a breakthrough this 
> > evening when we observed in a packet trace that the response case was 
> > fully lowercase, regardless of the query case. It seems iOS is doing some 
> > kind of case sensitive comparison between the query and the response, 
> > causing DNS-SD to fail when they dont match.
> Then iOS (or the application) is broken.  Domain names should always
> be compared case insensitively.  Please report a bug to the app
> vendor and / or Apple.

Isn't this the DNS 0x20 security enhancement? Clients send a random mix 
of case, and check that the response matches, to protect against spoofed 

Barry Margolin
Arlington, MA

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