FreeBSD Traffic Shaping

Ted Mittelstaedt tedm at
Wed Apr 2 23:02:11 UTC 2008

> -----Original Message-----
> From: owner-freebsd-questions at
> [mailto:owner-freebsd-questions at]On Behalf Of
> freebsd at
> Sent: Wednesday, April 02, 2008 4:51 AM
> To: freebsd-questions at
> Subject: Re: FreeBSD Traffic Shaping
> As far as I know, every carrier bills by 95th percentile.

You better call your carrier and confirm this.

The last carrier we had in that did this did in fact NOT bill by peak,
they billed by average.  However, the contract language SEEMED
to say peak.  We were naturally concerned about this after the first
month due to our graphs indicating that we had exceeded the peak.
However, the carrier (AT&T) did not bill a surcharge.  After that
we regularly peaked over the designated MBs
during the contract term with no billing surcharge.  The last
2 months of the contract we got nailed with very high surcharge
fees for the last 2 month use period.  Needless to say we did
not renew the contract and the
matter is in litigation now.  We never got a satisfactory answer
from anyone there as to what calculation they used to determine
how the surcharge was calculated.

Of course it was our dumb fault.  In the future if we ever sign
any of those bandwidth contracts again we will require the carrier
to supply in the contract the mathematical formula they use to
calculate whether or not a surcharge applies.  We will then
read the formula and determine for ourself whether it means
peak or average.

> This particular server is colocated and the bandwidth average is  
> 2.35mbps while the 95th is 3.7mbps.
> I don't want my clients to have to compete for bandwidth - if 1000  
> users share a 3mbps fixed pipe, they will each get 3k/sec -. Rather I  
> want to guarantee a fixed output for each client. This ensures  
> adequate speed for everyone AND flattens out my peaks.

Except that during the vallys of your utilization your clients
will be limited as well - meaning that if for example your bandwidth from
2-3am is only .5Mbps, 3Mbps would be available - and if one of
your clients happened to want to use 3Mps, his transfer will be
pushed forward out of the 2-3am time period and into the 2-8am
period.  Meanwhile your carrier gets away scott-free because
they didn't have to supply you with the 3.5Mbs during the night,
even though you were entitled to it.

Anyway, I'm sure your going to do what you feel like and damn the
advice everyone is giving - hopefully it works out for you.  I
personally think these kinds of contracts are devices to make
the carrier a windfall they don't deserve, and I hope that
you manage to "beat" the contract and extract your last available
byte without penalty - because the more people that manage to
do this the less lurative these dumb contracts will be and the
less incentive the carriers will have to offer them - but I
think in your case your up against a telco who has a lot of
experience screwing over customers, and they will find out some
way to apply the surcharge no matter what you do.


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