CDN node locations

Jay Ashworth jra at
Sun Nov 17 00:36:40 UTC 2013

> Second, a list of CDN nodes is likely impossible to gather & maintain
> without the help of the CDNs themselves. There are literally thousands
> of them, most do not serve the entire Internet, and they change
> frequently. And before you ask, I know at least Akamai will _not_ give
> you their list, so don't even try to ask them.

I find myself unsurprised.

I was led to a very interesting failure case involving CDN's a couple weeks
ago, that I thought you might find amusing.

I have a Samsung Galaxy S4, with Sprint.  On a semi-regular basis, the 
networking gets flaky around 1-2am ish local time, but 3 weekends ago, 
the symptom I saw was DNS lookups failed -- and it wasn't clear to me
whether it was "just some lookups failed", or that Big Sites were cached 
at the provider, and *all* outgoing 53 traffic to the greater internet
wasn't being forwarded by Sprint's customer resolvers.

I know that it was their resolvers, though, as I grabbed a copy of Set DNS, 
and pointed my phone to, and, and OpenDNS, and like that, 
and everything worked ok.

Except media.

(Patrick is starting to nod and chuckle, now :-)

Both YouTube and The Daily Show's apps worked ok, but refused to play
video clips for me.  If I reset the DNS to normal, I went back to "not
all sites are reachable, but media plays fine".

My diagnosis was that those sites were CDNed, and the DNS names to *which*
they were CDNs were only visible inside Sprint's event horizon, so when I 
was on alternate DNS resolution, I couldn't get to them.

But that took me over a day to figure out.  Don't get old.  :-)

Patrick?  Is that how (at least some) customers do it? 

-- jra
Make Election Day a federal holiday:  100k sigs by 12/14

Jay R. Ashworth                  Baylink                       jra at
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St Petersburg FL USA               #natog                      +1 727 647 1274

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