North American Network Operators Group

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Re: That MIT paper

  • From: Joe Shen
  • Date: Tue Aug 10 22:39:14 2004

Hi,


>The paper doesn't pass any judgement on types of lookups, but obviously
>not all DNS lookups are equal from the end user perspective.

In our observation, looking for IP address consists 70% of our cache server load,
MX consists of 14% and PTR only occupies 5%. And, on the other hand, the coarse
analysis of our network traffic shows, Web traffic occupies only 8% while 
stream meadia occupies the most part of traffic. So, the authors the conclusion
may be correct as viewing film online does not rely on DNS so much as 
browsing web pages.

But, to my understanding a too short TTL will do harm to cache server performance
esp. the amount of RR cached is so large that BIND have to wait for swapping I/O
and re-fetching those timeout RR again.

>"In our follow-up measurement study, [we found] that DNSBL related
> DNS lookups at CSAIL in February 2004 account for 14% of all DNS
> lookups. In comparison, DNSBL related traffic accounted for merely
> 0.4% of all DNS lookups at CSAIL in December 2000."

Is these work published or available publicly? Any work done with performance tuning
with cache server?

> 1. almost nobody has time to invest in reading this kind of paper.
> 2. almost everybody is willing to form a strong opinion regardless of that.
> 3. people from #2 use the paper they didn't read in #1 to justify an opinion.

people rely on their experience, but science tries to find on basis of analysis.
Usually, we met problems which is caused by people replace scientific conclusion with  
their experience. 

Joe






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