CDN Overload?

Mike Hammett nanog at
Wed Sep 21 14:40:33 UTC 2016

I've had DSL and AE service providers respond with the issues. 

So far there is not a common element other than CDNs. 

That's the point of the questions I'm asking, to gather a ton of information and then figure out how to act on it. 

You're assuming that the CDNs are using an unmolested, vanilla TCP stack. That may not be the case, especially if doing something like Fast TCP. 

Mike Hammett 
Intelligent Computing Solutions 

Midwest Internet Exchange 

The Brothers WISP 

----- Original Message -----

From: "Baldur Norddahl" <baldur.norddahl at> 
To: nanog at 
Sent: Wednesday, September 21, 2016 9:32:58 AM 
Subject: Re: CDN Overload? 

It appears all complaints are from SP doing wireless. I am going to go with 
a yes and put forth a these that these guys have a common factor somewhere. 
It could be equipment from a some popular vendor of wireless or maybe some 
common method to throttle that is popular in the wireless community. 

I note that while we have slow links we have no throttling or bandwidth 
management going on except for the buffering that happens in the DSLAM. 

Also there is no way to cheat. If you send 4 mbps to a 2 mbps DSL it will 
drop half of the traffic and TCP will not survive that. The CDN would have 
an effective transfer rate approaching zero for that customer. That seems 
to be a rather bad business proposal seen from the view if the CDN so they 
would not do that. The other customers will be unaffected as the DSLAM 
itself has plenty of capacity. 



Den 21. sep. 2016 14.36 skrev "Josh Reynolds" <josh at>: 

> With so many geographically diverse complaints on many hardware routing 
> and switching platforms, I'm going to go with a "no". 
> On Sep 21, 2016 4:04 AM, "Baldur Norddahl" <baldur.norddahl at> 
> wrote: 
>> How come we have never seen this problem? We have a ton of DSL and many 
>> of those are slow, but no customer complaints about overloaded lines from 
>> CDN networks. 
>> Could it be that the way you throttle the bandwidth is defect? It is easy 
>> to blame the other guy but could it be that you are doing it wrong? 
>> Regards, 
>> Badur 

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