CGN and CDN (was Re: what about the users re: NAT444 or ?)

Alexander Harrowell a.harrowell at
Fri Sep 9 16:06:37 UTC 2011

On Friday 09 Sep 2011 16:25:35 Valdis.Kletnieks at wrote:
> On Fri, 09 Sep 2011 11:09:38 EDT, Jean-
Francois.TremblayING at said:
> > A very interesting point. In order to save precious CGN resources, 
> > it would not be surprising to see some ISPs asking CDNs to provide 
> > a private/non-routed behind-CGN leg for local CDN nodes. 
> > 

The actual problem here is that everyone assumes it'll be donkey's years 
before every last web server in the world is on IPv6.

If you're a CDN, though, you can solve this problem for your own network 
right now by deploying IPv6! Akamai says that you need 650 AS to cover 
90% of Internet traffic. I propose that effort getting content networks 
to go dual stack is better used than effort used to work around NAT444.

Further, if making your hosting network IPv6 is hard, the answer is 
surely to give the job to a CDN operator with v6 clue. I actually rather 
think CDNs are an important way of getting content onto the IPv6 

In my view CDNing (and its sister, application acceleration) is so 
important to delivering the heavy video and complex web apps that 
dominate the modern Internet that this should be a killer. 

Still, breaking the BBC, Hulu, Level(3), Akamai, Limelight, and Google's 
video services will probably reduce your transit and backhaul bills 
significantly. Can't say it'll help with customer retention.

> > For this to work, the CGN users would probably have a different 
> > set of DNS servers (arguably also with a private/non-routed
> > leg) or some other way to differentiate these CGN clients. Lots 
> > of fun in the future debugging that.
> Especially once you have 10 or 15 CDNs doing this, all of which have 
> rules of engagement. "Akamai requires us to do X, Hulu wants Y, Foobar 
wants Y
> and specifically NOT-X..." ;)
> And then Cogent will get into another peering spat and.... :)

The only thing worse than e-mail people who send e-mail 
to lists complaining about them
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