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Tools for testing streaming media
So here's a neat trick for testing how streaming media and web applications perform for users with limited bandwidth connections. OK...I'm getting some rolling eyes at the premise. "Does anyone have limited bandwidth connections anymore?" Turns out that, "Yup...they do."Two cases in point:
- Last fall, the Harvard Alumni Association offered an all-online version
of the popular undergraduate course, "Justice" to Harvard
alumni and their invited guests. Over 3000 participants
signed up for the term-length 24-lecture course, delivered via Flash
streaming (rtmp) video encoded for broadband (~400kbps). Most common
technical complaint from users: video performance and rebuffering due
to insufficient bandwidth.
- So, I've got one of those Verizon Wireless Cellular Modems, a little USB one. Great 500kbps+ broadband in the city, but when I go on one of my frequent trips to coastal Maine, I'm lucky if I get 80kbps. Actually, I really am lucky, as the alternative is 56k dial-up. Wide swaths of the geography are not covered by cable or DSL, and cellular is the best I can do. People have to drive into town to get Wifi at the local cafe, or suffer with a slow connection from home.
For Windows, Netlimiter, an inexpensive bandwidth simulator utility I wrote about on streamingmedia.com (and commented on here) a while back, lets me set my throughput to whatever I like. I can pretend I'm on my coastal-Maine cell-modem, or a dialup, or anything else easily.
For the Mac, it's already built in to the OS's Unix roots. It's in the ipfw command. You set up the bandwidth limits by creating filters with bandwidth limits, then associating those filters with the ports you want limited. Here's how to set up a bandwidth limiter for testing rtmp Flash streaming (port 1935). Note that if you're not logged in as root, you will need to use sudo to run these:
sudo
ipfw pipe 1 config bw 400kbps
sudo ipfw add 10 pipe 1 tcp from any to me 1935
sudo ipfw add 11 pipe 1 tcp from any 1935 to me
sudo ipfw add 10 pipe 1 tcp from any to me 1935
sudo ipfw add 11 pipe 1 tcp from any 1935 to me
Change it at will by issuing the pipe command again...
sudo
ipfw pipe 1 config bw 1400kbps
You can also introduce simulated network latency, control outbound bandwidth separately from inbound, and control bandwidth to or from a single IP address or subnet. There's great documentation at Luigi Rizzo's Dummynet site. Thanks also to Ask Bjorn Hansen for his mini-tutorial on this.
Posted by larryb at 07:12 AM [permanent link] | Comments (1)
Category: Streaming Media Technology Tips , Video and Multimedia Technology , Web and Software Development
Category: Streaming Media Technology Tips , Video and Multimedia Technology , Web and Software Development
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Thanks for giving all the details.
Posted by: Web Programming | April 22, 2009 07:08 AM