Gaps in internet explorer tests

Web Performance Discuss Test Results
1

Hi,

I see gaps in waterfalls with tests in internet explorer I don’t understand:
http://www.webpagetest.org/result/150521_HR_Q58/1/details/

If these gaps between DNS lookup and connection initialization or between connection/ssl-handshake and ttfb would appear in follow-up resource requests I would assume the browser performs DNS pre-resolution and/or TCP pre-connection. But in initial (HTML-)request?

I don’t understand these gaps.
Is that a bug in rendering of wpt waterfall and dns lookup or connection initialization last longer than bars in waterfall chart look like?
Or is it a problem in wpt or browser software on agent machines and browser is busy in these gaps? But there is nothing eye-catching in cpu utilization…

Best regards, Nils

2

You can capture a tcpdump and look at the packets to verify but last time I did that for IE 11 the gaps were real and I have no idea what IE is doing in that time.

3

IE is… well IE. It is often derided for doing things it shouldn’t and it is pretty much a law unto itself.

My best guess was that there were other processes being kicked off in the background (looking at the CPU utilisation graphs).