Content Delivery Networks

Chris L. Morrow christopher.morrow at
Sun Aug 12 01:21:31 UTC 2007

On Fri, 10 Aug 2007, Max Inux wrote:

> Of course the CDN wouldn't know or care, it would however possibly
> lead to that user experiencing negative performance or availability
> outside the realm of the CDN's control. I know where we are we move
> things via dns atleast 2xTTL early, usually more, but emergency
> situations (i.e. taiwan earthquake, fiber cuts, oc192 outages etc.)
> would have serious negative implications for users or servers
> ignoring the TTL- it is sometimes set for a legitimate reason.

I'm sorry, I think you or I miscommunicated... What I was asking, as 'how
does the CDN or CDN operator know that the recursive server is ignoring
the TTL returned with the RR as opposed to client side issues?' Your
response didn't really answer that part. I ask because you seem to have
data proving ( to some extent ) that 'many nameservers ignore ttls', I was
curious how you'd gathered that, and how you'd know that the nameservers
(aside from querying them directly) were ignoring TTLs on RRs.


> On Aug 10, 2007, at 6:22 PM, Chris L. Morrow wrote:
> >
> > On Aug 10, 2007, at 9:13 AM, Max Inux wrote:
> >
> >>   Working for a content delivery network I can tell you that there
> >> are many nameservers  ignoring TTL that affect many users (AOL
> >> being the largest american one).  Coincidentally AOL users aren't
> >
> > So, I'd also ask this, do you know it's the recursive server, or is
> > the
> > behavior that you see related more to the application caching and not
> > respecting the TTL? (IE for instance and it's default 30 minute, I
> > think,
> > ttl).
> >
> > How does a CDN tell the recursive server is doing this vice the client
> > app?

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