Contention/Oversubscription maths

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

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,

I don't use almost any bandwidth outside of Netflix, Steam game
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.

This is pretty much what I expect. If you give a 4Mbit user 40Mbit, he tends not to even be able to use 10 times as much, so we can get away with much higher ratios.

Statistics and graphs i've seen offlist have been very helpful, and suggest that 1000 100mbit customers is doable on 1GE.

Atleast, today. Next year's (decade?) launch of the YouView platform in the UK should increase usage a lot, not to mention a service like Netflix starting in the UK. We have some movie streaming services, but they generally suck and are quite low bitrate.

Thanks for the thoughts

Statistics and graphs i've seen offlist have been very helpful, and
suggest that 1000 100mbit customers is doable on 1GE.

Probably.

Atleast, today. Next year's (decade?) launch of the YouView platform in
the UK should increase usage a lot, not to mention a service like
Netflix starting in the UK. We have some movie streaming services, but
they generally suck and are quite low bitrate.

The short version is: if you oversubscribe, you *will* eventually have Busy
Hours, just like telcos. The question is: how often. Telcos have books
that tell them this...

Cheers,
-- jr 'Royal Wedding' a

I run a WISP, where we have moved customers from 3mb/s to 8mb/s to 20mb/s
over the course of 5 years. We do this one tower at a time (about 150
customers) what we have learned is usage grows overtime not with the
increase in available bandwidth. Our Per-Customer-Avg (PCA) stayed about
the same with each bump in bandwidth, the avg user does not use more
bandwidth because they have more bandwidth or at least not our 1200
customers.

That said we have had our PCA move up more then 30% in the last 7 months due
mainly to Netflix, the nice thing is this usage is "off peak" for
our business customers and as such has not been a concern.

Shaun

Shaun Bryant
sbryant@thepit.org

Yeah, I fully expect this.

In previous networks I've generally seen a doubling of traffic every 12 months. Generally the traffic is static during spring/summer, and then doubles over 6 months in autumn/winter.

Though, I'm not sure how this will manifest itself with such high access speeds.

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.

I would bandwidth limit the ports, as someone else already mentioned. I
would also enable WRED, ECN and everything else I could lay my hands on.
What is that port connected to in the customer's end? Are they plugging
into a 8 port switch and fanning out that connection to their DVD player
which they use to watch Hulu and Netflix and a bunch of other services?
My Sony DVD player came with about 6 Internet video services programmed
in it and it has an ethernet port. Do they have a slingbox where they
are going to watch their home TV from work? And just having all those
users on a flat switched network would be one heck of a security hazard
(again, as someone else mentioned). But to be honest, I wouldn't deploy
that model at all. One person can DOS the entire building depending on
how it is deployed and that is without even touching the uplink port.

Now figure about a tenth of those computers will be infected by bot nets
and will sit there sending spam and click fraud all night long, too.

G