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Re: Updates to Navigation Timing errata

From: McCall, Mike <mmccall@akamai.com>
Date: Tue, 14 May 2013 12:36:22 -0500
To: Arvind Jain <arvind@google.com>, Boris Zbarsky <bzbarsky@mit.edu>
CC: public-web-perf <public-web-perf@w3.org>
Message-ID: <CDB7EA67.E3E1%mmccall@akamai.com>

On 5/14/13 1:13 PM, "Arvind Jain" <arvind@google.com> wrote:

>Taking the example of DNS resolution, with a pre-resolve, the spec seems
>to state that domainLookupStart would be the time when the pre-resolve is
>actually started. But I think it makes more sense to talk in context of
>user navigation - a pre-resolve
> should be treated like a cache hit, so if a pre-resolve finished before
>navigationStart, we should report domainLookupStart and End == fetchStart.

I don't like the idea of treating a pre-resolve as a cache hit.  Having a
domainLookupStart/End == fetchStart in a pre-resolve makes it useless as a
metric as browsers become more aggressive about pre-resolving hostnames.
If you're a site owner and interested in your DNS provider's real-world
performance, having the browser effectively zero it out for a pre-resolve
means you're missing out on hostname resolutions that occurred for your
site as a user was navigating to it.  I'd want to know about this stuff
irrespective of whether or not it was perceived by the user.  The same
goes for TCP connections.

Mike  
Received on Tuesday, 14 May 2013 17:36:51 UTC

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