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Bandwidth Graphs
06-24-2010, 07:02 PM
Post: #4
RE: Bandwidth Graphs
(06-24-2010 05:58 PM)green-watch.org Wrote:  Hey Markus,

Thanks for the great explanation for the bandwidth graph.

So If I have a 364 KB file which is being downloaded on a DSL connection (1.5 Mbps), in a perfect world I would have a maximum throughput of 0.1875 MBps and it would download in ~1.8958333 seconds.

364 KB * 1 MB / 1024 KB = 0.35546875 MB File Size

1 MBps (megabyte per second) = 8 Mbps (megabits per second)

0.1875 MBps = 1.5 Mbps

0.35546875 MB File Size / 0.1875 MBps Maximum ThroughPut = 1.8958333 seconds download time

http://www.webpagetest.org/result/100624_EER/4/details/

It looks like the reason this bandwidth was bad is because of the earthmail.jpg file took so long to download before the document complete events began, which brings me to my next question:

Yep, between 2.7 and 4.7 seconds it downloads just 2.5 KByte worth of true data. That corresponds to a bandwidth of close to zero.

(06-24-2010 05:58 PM)green-watch.org Wrote:  Is it possible to trigger the document complete event before images are done downloading?

I know it is possible to start downloading after the document complete event. I also know that the document complete event fires even if asynchronous javascript files are being downloaded, so why not images? Is there a way that anybody knows of?

I assume that this could be done. Anyway, the question is, if that would improve the perceived performance by the customer? Or would be a rather "scientific" improvement, with no perceived improvement?

(06-24-2010 05:58 PM)green-watch.org Wrote:  In addition, you said one reason bad bandwidth occurs is because of latency sometimes caused by long times to first byte.

I started discussing this here a bit:

http://www.webpagetest.org/forums/showth...hp?tid=262

Times to first bytes on coldfusion pages for example can be caused by many backend database queries, but what causes long time to first bytes with images?

Sincerely,
Travis Walters

A reason could be Network congestion. Your TCP SYN or HTTP GET is delayed or even dropped in an overloaded routing queue along the network path.
Other reason could be an overloaded machine or Webserver, which is busy answering requests from other visitors to your site.

Kind regards,
Markus
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Messages In This Thread
Bandwidth Graphs - green-watch.org - 06-24-2010, 05:18 AM
RE: Bandwidth Graphs - LeptienM - 06-24-2010, 05:21 PM
RE: Bandwidth Graphs - green-watch.org - 06-24-2010, 05:58 PM
RE: Bandwidth Graphs - LeptienM - 06-24-2010 07:02 PM
RE: Bandwidth Graphs - green-watch.org - 06-24-2010, 07:28 PM
RE: Bandwidth Graphs - pmeenan - 06-25-2010, 03:30 AM

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