Re: CDN node locations

[Phil Bedard <bedard.phil () gmail com>]

On 11/16/13, 7:36 PM, "Jay Ashworth" <jra () baylink com> 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 8.8.8.8, and 4.2.2.1, 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?


It seems more likely the Sprint resolvers you were using were having
difficulty reaching external authoratative servers but the devices they
proxy all the media content through wasn't...  All major media content
these days is CDN'd but I don't think that had anything to do with it.

Phil