CDN node locations

Martin Hannigan hannigan at
Sun Nov 17 20:32:06 UTC 2013

There are a number of us here.



On Sun, Nov 17, 2013 at 3:21 AM, Warren Bailey <
wbailey at> wrote:

> Uhhhh.. So who gets to field the Akamai questions now? ;)
> Sent from my Mobile Device.
> -------- Original message --------
> From: "Patrick W. Gilmore" <patrick at>
> Date: 11/16/2013 4:10 PM (GMT-09:00)
> To: NANOG list <nanog at>
> Subject: Re: CDN node locations
> On Nov 16, 2013, at 19:36 , Jay Ashworth <jra at> wrote:
> >> 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?
> #1: I could not possibly comment on customers. But since I've only worked
> at Markley Group for 3 weeks, I don't know all the customers, so I couldn't
> tell you even if they were customers at all, more or less how they do
> things. Besides, Markley Group ain't a CDN.
> #2: Assuming you are assuming I still work at Akamai (I don't), and are
> asking me if that's how Akamai does things, I couldn't possibly comment on
> customers at a previous position. Everything I've said up to now was either
> public knowledge or something I was more than happy to give out publicly if
> asked while I was at Akamai. The query above, specifically "is XXX how
> customer YYY does things", is neither of those.
> But in the more general sense, your hypothesis does not really fit the
> circumstances completely. DNS is orthogonal to serving bits. If Sprint's
> DNS is f00bar'ed, then you can't resolve anything, CDN-ififed or not. It is
> true some CDNs put some name servers inside other networks, but that is
> still a race condition, because (for instance) Akamai's DNS TTL is 20
> seconds. You have to go back 'outside' eventually to get stuff, which means
> relying on Sprint's recursive NSes.
> Plus the two sites you list (YouTube & DailyShow) are not on the same
> infrastructure. Google hosts its own videos, DailyShow is not hosted on
> Google (AFAIK), therefore they must be two different companies using two
> different pieces of equipment and two different name server algorithms /
> topologies. It would be weird that Sprint's failure mode worked fine for
> those two and nothing else.
> Sorry.
> --
> patrick
> P.S. I wasn't chuckling. :)

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