Difficulty with Simulate Modem Speeds

[mitch]

Hello,

I recently downloaded Fiddler so I could simulate a slower network speed while developing an application. As a simple test I clicked on Rules > Performance > Simulate Modem Speeds. I then tried running a speed test at speedtest.net in Chrome and IE but they both showed my normal speeds of several tens of Mb / second. I tried uninstalling Fiddler4 and installing Fiddler2, restarting, other applications, but in no case am I able to perceive the slower network speed measurements in speedtest.net.

I checked the CustomRules.js file and the settings are set to the default. Am i missing something basic here?

        if (m_SimulateModem) {

            // Delay sends by 300ms per KB uploaded.

            oSession["request-trickle-delay"] = "300"; 

            // Delay receives by 150ms per KB downloaded.

            oSession["response-trickle-delay"] = "150"; 

        }

After some more testing, I tried increasing those trickle delays above by a factor of 10 and it does seem that perhaps my network is running more slowly but I'm not sure. Speedtest.net is not loading in my browser. Perhaps speedtest.net is only reporting speeds to my computer but not speeds between my network drivers and my applications?

Can you please advise how I might test what types of speeds I'm actually getting?

thanks,

Stuart

[Eric Lawrence]

I believe the site in question may be using a Flash connection that bypasses the proxy. Rest assured that if you set the simulate option and browse normal pages, you won't fail to notice how slow they are.

[Eric Lawrence]

Also, if you have the "Stream" button set in Fiddler's toolbar, try unsettling that.

[mitch]

Stream was not set. One other thing that is puzzling me is that I'm downloading a 40 megabyte file using FileZilla. It takes about 20 seconds to perform this download regardless of whether Simulate Modem Speeds is checked. That's about 16 megabits per second.

I've got these settings at the moment. What could i be doing wrong? Is there possibly some sort of caching that is going on that is allowing these transfers to happen much more quickly than I would expect?

if (m_SimulateModem) {

            oSession["request-trickle-delay"] = "6000"; 

            oSession["response-trickle-delay"] = "4500"; 

        }

[EricLaw]

I've verified that SpeedTest.net uses a Flash applet to communicate directly with the load server over TCP/IP, using a custom non-HTTP protocol; this bypasses the proxy and isn't HTTP traffic, which is why the Chrome Dev Tools don't show the requests and why Fiddler's "Simulate Modem Speeds" doesn't impact the response. In practice, direct use of TCP/IP (bypassing the proxy) is rare as it often does not work behind company firewalls.

FileZilla appears to primarily be a FTP client, and it's not clear that it uses CERN-proxy mode to talk to the system proxy. You may need to manually configure it: https://www.google.com/?gws_rd=ssl#q=filezilla+proxy