Contention/Oversubscription maths

Adam Armstrong lists at
Fri May 27 12:54:11 UTC 2011

On 27/05/2011 13:44, Jeroen van Ingen wrote:
> Hi Adam,
>> 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. I don't think those
>> kinds of events will have an appreciable effect on the platform here. An
>> album is what, 100MB? A 5min HD youtube video is going to be a similar
>> size. Also too small to care about. These kinds of things don't get
>> worse in high speed, they get easier.
>> Same with patch tuesday, I think even a Win7 SP1-like release wouldn't
>> cause major headaches, as streaming SD TV for an hour is more bandwidth
>> than SP1 (nevermind HD).
>> I'm more interested in the levels of traffic that we will see consistently.
> Perhaps students are not average users, but our Resnet currently has:
> * Approx 2000 connections, most at 100 Mbps.
> * These are divided into 4 areas, each area is connected with 1 Gbps to
> central location (so on average you could say we have 500 users sharing
> a 1 Gbps link)
> * Central location has 10 Gbps uplink; stats for this link over the last
> 7 days at 10-min average polling interval are:
> in: min 422 Mbps, avg 883 Mbps, max 1570 Mbps, 95th pct 1250 Mbps.
> out: min 48 Mbps, avg 272 Mbps, max 571 Mbps, 95th pct 459 Mbps.
> Perhaps these numbers can be used as an indication for your
> sizing/design.
Most useful response so far, thanks very much :)


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