WebPagetest Forums
parallel downloads - Printable Version

+- WebPagetest Forums (https://www.webpagetest.org/forums)
+-- Forum: Web Performance (/forumdisplay.php?fid=3)
+--- Forum: Discuss Test Results (/forumdisplay.php?fid=4)
+--- Thread: parallel downloads (/showthread.php?tid=10257)

parallel downloads - trx - 12-23-2011 11:17 AM

Hello All,
From what I understand, IE browser 8 allows up to 6 connections.
From the page test below, the waterfall starts off around 6 parrallel downloads and then kind of starts dropping off in numbers of parrallel


Any ideas on why this is happening?



RE: parallel downloads - pmeenan - 12-24-2011 12:50 AM

Scroll down to the connection view waterfall and you can see that it is fully using 6 parallel connections to your domain (it is 6 connections per FQDN, not total). The other domains have fewer because there just aren't enough resources coming from them to need more.

RE: parallel downloads - pmeenan - 12-24-2011 12:51 AM

Needless to say, re-compressing your JPEG images at a lower quality level (which will save 70% of the bytes - 2.7MB) will go a long way to making it faster: http://www.webpagetest.org/result/111223_V9_2M4T3/1/performance_optimization/#compress_images

RE: parallel downloads - trx - 12-30-2011 06:54 AM

Yes, I'm aware of the images not being compressed. It was an marketing decision to keep it that way.
I'm was just concerned about the waterfall parallel connections as it looked like it went drop from 6 downward.

Looking at the connection view, it shows 7 connections to "www.qad.com".
I'm assuming you're only counting 6 for the static resources, correct?

Also do you know what the green line is for at the 2 second mark of the waterfall means?
Do you know of a page that helps interprets all the results on webpagetest?

Let me know.

Thanks again!


RE: parallel downloads - pmeenan - 01-03-2012 01:36 AM

The limit is 6 parallel connections open at any given point in time, not for the life of the page load. I'm not sure why #2 wasn't re-used but it opened up additional connections instead.

The green line is the start render time (the point at which something was first displayed on the screen).

RE: parallel downloads - trx - 03-07-2012 04:11 PM

Thanks. What you explained makes perfect sense. The only thing that can be confusing is in the water fall, there are 6 parallel connections, but why does it seem that the TTFB is not received at the same time or is it NOT suppose to be?

ex) you see #15-#20, the FFTB is received around the same time, but farther down the water fall, #178 to #183 FFTB seems to be received NOT around the same time.

Maybe I"m over thinking this, but do you have any thoughts on my observation?


RE: parallel downloads - pmeenan - 03-08-2012 12:28 AM

As each piece of content downloads on each connection they start getting out of alignment (because it takes different amounts of time to download each resource). Even if they were all identical sizes there would still be some level of contention.

That's a long way of saying "you're over thinking it" :-D

RE: parallel downloads - trx - 03-08-2012 02:57 AM

lol. Thanks pmeenan! Appreciate your quick responses.