CDN Overload?

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).

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  Jon Lewis, MCP :)           |  I route
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