Content Delivery Networks

Chris L. Morrow christopher.morrow at verizonbusiness.com
Tue Aug 14 14:57:08 UTC 2007



On Tue, 14 Aug 2007, [iso-8859-1] Bjørn Mork wrote:

> "Chris L. Morrow" <christopher.morrow at verizonbusiness.com> writes:
>
> > This is still a client issue as, hopefully, the cache-resolvers don't
> > funnel their business through nscd save when applications on them need
> > lookups... (things like ping/telnet/traceroute/blah)
>
> nscd may represent a problem if the application in question is a
> http-proxy without it's own resolver.  There's also a number of
> more-or-less broken http-proxies doing their own resolver caching
> regardless of actual TTL.

that's fine, that's still a client problem, not a cache-resolver
problem... These devices look 'upstream' for a cache-resolver to do their
dirty work, these just add an extra layer of indirection for the CDN to
figure out (my client is in SFO, my proxy is in IAD, my cache-resolver is
in CHI).

>
> Such applications represent a problem wrt any DNS-based load balancing,
> including CDNs, since they can serve a large number of end-users,
> redirecting them to the "wrong" address long after the TTL should have
> expired.

Yup, people should be aware of what the systems in their path are doing,
or as was mentioned earlier, have lots of exceptions on the CDN side.



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