CDN Overload?

Jon Lewis jlewis at
Tue Sep 20 01:49:59 UTC 2016

On Mon, 19 Sep 2016, Mike Hammett wrote:

> The principal complaint is that upstream of whatever is doing the rate 
> limiting for a given customer there is significantly more capacity being 
> utilized than the customer has purchased. This could happen briefly as 
> TCP adjusts to the capacity limitation, but in some situations this has 
> persisted for days at a time. I'll list out a few situations as best as 
> I can recall them. Some of these may even be merges of a couple 
> situations. The point is to show the general issue and develop a better 
> process for collecting what exactly is happening at the time and how to 
> address it.
> One situation had approximately 45 megabit/s of capacity being used up 
> by a customer that had a 1.5 megabit/s plan. All other traffic normally 
> held itself within the 1.5 megabit/s, but this particular CDN sent 
> excessively more for extended periods of time.

It sounds like either the rate-limiting just isn't working, or the CDNs 
are trying too hard to ramp up the transfer rate in spite of your dropping 
some/most of the packets.  I assume drops are happening either as part of 
the rate-limiting/policing, or simply as a result of trying to stuff 
45mbit/s onto a 1.5mbit/s pipe....96.5% packet loss...and they're not 
slowing down at the sender?!?

This is kind of a funny problem though, because CDNs get paid to deliver 
data, and they get compared/graded according to who can deliver the bits 
the fastest...and here you are complaining that they're delivering the 
bits too fast (or at least faster than you'd like them to).

  Jon Lewis, MCP :)           |  I route
                              |  therefore you are
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