Content Delivery Networks

Patrick W. Gilmore patrick at
Tue Aug 7 13:07:28 UTC 2007

On Aug 7, 2007, at 3:59 AM, Michal Krsek wrote:

> 5) User redirection
> - You have to implement a scalable mechanisms that redirects users  
> to the closes POP. You can use application redirect (fast, but not  
> so much scalable), DNS redirect (scalable, but not so fast) or  
> anycasting (this needs cooperation with ISP).

What is slow about handing back different answers to the same query  
via DNS, especially when they are pre-calculated?  Seems very fast to  

Application redirection is far, far slower.  (I am assuming you are  
talking about something like HTTP level redirects.  Did you mean  
something else?)

As for anycast, with your own backbone, you don't need any  
cooperation.  Even if you don't, the cooperation you need from your  
providers & peers is minimal at worst.  (At least relative to writing  
the code for, say, DNS redirection.)  But anycast assumes "BGP knows  
best", and we all know that is not even close to the truth.


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