named

[Richard Pieri]

On Dec 2, 2010, at 1:28 AM, Derek Martin wrote:
A bunch of stuff that my experience does not bear out.  In over 20 years of being a DNS admin with a variety of ISPs involved, I have rarely seen a local DNS cache prove to be inferior to going out to the ISP for every lookup.  To the contrary, running a local cache provides superior lookup times for all but the first lookup in all but the most dodgy edge cases.

The CDN argument falls flat.  If the CDN looks at the ISP's source addresses on DNS lookukps then it still isn't going to get you something geographically local.  A node on Speakeasy in Maine gets a list of name servers geographically located in New York City even though Boston is closer.

The super-short TTL argument falls even flatter.  Suffice it to say that DNS roulette is not load balancing.  There have been many papers written about why it is bad practice.  That Akamai uses DNS roulette doesn't make it better.  In fact, it's a lot of why Akamai is derided for making the web go slow.

--Rich P.