Contention/Oversubscription maths

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Fri May 27 07:02:57 CDT 2011


On Fri, 27 May 2011 10:49:05 BST, Adam Armstrong said:
> I'm talking of 1000 users on the end of a 1GE, not 50,000. I don't think 
> either of these scenarios are worrying.
> 
> 300MB takes <3seconds on 1GE or 30 seconds on 100M.

The pont is that it takes a lot longer than 3 seconds if that uplink is already
90% full - it just jumped to 30 seconds.  How long does it take for all 1000 users
to do it, assuming the pipe is 95% full already?

> A 5min HD youtube video is going to be a similar size.

What's the sound of 1000 Netfllix users streaming 1000 different 90 minute
long HD movies?  Why should they limit themselves to 5 minute videos? After
all, you sold them *gigabit*, which we know is 125 times as fast as the 8mit
you're likely to get from that cable company (and that's when you're going to
need those weasel words in your SLA when you can't deliver gigabit).

(You never said if this is a commercial or residential buildout - the traffic patterns,
concerns, and complaints will differ for the two. Good luck in any case)

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