Contention/Oversubscription maths

Jacob Broussard shadowedstranger at gmail.com
Fri May 27 08:40:02 CDT 2011


I apologize if you thought I was trying to call you out or correct you; I
was merely trying to provide some perspective.  Sorry if I came off as
hostile.  I understand that a 1000:1 does not mean that you get 1000th the
backhaul speed, no need for the snarky remarks.  I simply stated that it may
cause you headaches as in the past we had a 35:1 ratio and were at capacity
most of the day (12-16 hours). We offer peak speeds of 4mbps, and we have an
extrordinary amount of people using (abusing as some would say) streaming
video for many hours of the day causing headaches for us.  You probably
would be safe to assume that you can use a higher ratio for your higher
speeds as there will be fewer people that can take advantage of the full
connection speed.  Again, not trying to come off as aggressive or hostile,
just trying to provide some more perspective to help you out.
On May 27, 2011 6:07 AM, "Adam Armstrong" <lists at memetic.org> wrote:
> On 27/05/2011 14:02, Jacob Broussard wrote:
>>
>> I don't use almost any bandwidth outside of Netflix, Steam game
>> downloads, and getting my daily dose of streaming starcraft videos and
>> ntop tells me I averaged 1.7mbps over the last month. Mind you this
>> is on an 8mbps peak connection. With peak speeds of 8m I would be
>> pissed if I was getting 500k, much less if I had a 100m connection and
>> got less than a meg. I have no doubt that if I had a faster
>> connection that I would have used even more bandwidth... With the
>> popularity of streaming video now a 1000:1 or even a 100:1
>> oversubscription rate is almost definitely just going to cause you
>> headaches... Back in my days of noc, 9 out of 10 bandwidth AUP
>> abusers weren't even using torrents, they were almost all netflix or
>> people that got rid of cable to watch video online.
>>
> I suspect your average usage is an order of magnitude higher than that
> of the 'average' user.
>
> This is one of the effects that makes it hard for me to imagine the
> traffic profile, as my own usage patterns (and those of my circle of
> friends) is not what one would call typical.
>
> For example if 300KB/sec average peak holds true with only 1000 users,
> that's only 300Mbit usage, giving 700Mbit headroom. I suspect this will
> only become true with 10000 users on 10G though, and that 1G links will
> be much more bursty as a single customer can push 10% of the backhaul
speed.
>
> Remeber that 1000:1 contention *doesn't* mean that you only get 1000th
> of the backhaul speed, it means the *peak average* usage of all users
> should be under 1Mbit. Your peak is most likely 8Mbit, but there are
> probably 40 users who use very liuttle for every one of you, and they
> may only double the peak average to 16mbit, thereby giving a much lower
> peak average for all 41 of you (if you see what i mean?)
>
> I suck at maths, and I'm pretty sure I was at home playing Tekken 2 when
> I should have been in statistics class :)
>
> adam.



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