Subject: Re: [Design] Re: the KEY debate

From: "Eric A. Hall" <[email-masked]>
Date: Wed, 07 Aug 2002 16:45:15 -0500

on 8/7/2002 4:01 PM Ted Lemon wrote:

>> Cache overflow is already common in large ISPs.
>
> Can you add a little more to this statement?   By itself, it could mean
> "most ISPs don't make their caches big enough," or "lots of trash
> falls out of the cache, improving performance," or "we have a real
> problem."   You seem to be saying that it's the third option, but you
> haven't said anything to support that interpretation.

What I'm saying is (d) the more crap we stick into DNS, the more caches
will overflow, making the service less useful

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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From: David Conrad <[email-masked]>
Date: Wed, 07 Aug 2002 15:03:23 -0700

> will overflow, making the service less useful

Sorry, I don't get this.

If the cache is filling up, it is because it is being used for something.
This would seem to me to imply that it is being more useful.

What am I missing?

Rgds,
-drc

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From: "Eric A. Hall" <[email-masked]>
Date: Wed, 07 Aug 2002 17:08:02 -0500

> This would seem to me to imply that it is being more useful.

Assuming a FIFO queue drain, stuff that *was* cached (and which should
have stayed in the cache) will be bounced. When that data is needed again,
another round of queries will have to be issued. At that point, the
benefits of caching have been obviated. Projected outwards with a
come-and-get-your-new-RR-and-names mentatility in conjunction with a very
high load, it is not impossible to imagine scenarios with inifinite churn.
Would DNS without caching be as useful?

Obviously there are ways around this -- add more caches, add more memory
to fewer caches -- but it is a real concern, not FUD.

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From: Derek Atkins <[email-masked]>
Date: 07 Aug 2002 18:17:36 -0400

> Assuming a FIFO queue drain, stuff that *was* cached (and which should

Bad assumption.  Assume LRU.  The rest of your statement doesn't
follow anymore.

-derek
-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       [email-masked]                        PGP key available

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From: Jim Reid <[email-masked]>
Date: Wed, 07 Aug 2002 15:29:32 -0700

>>>>> "Eric" == Eric A Hall <[email-masked]> writes:

    Eric> What I'm saying is (d) the more crap we stick into DNS, the
    Eric> more caches will overflow, making the service less useful

This doesn't make sense. Cached data clearly must be of some use
because it's being cached. And if someone's cache overflows, where's
the problem? There are various well known and widely implemented
solutions for this. Like buying more RAM (at how many cents/Mb?) or
adding more caching name servers. Or have the name server discard
older data to make room for the newer stuff.

Even if caches overflow and servers die horrible deaths as a result
of caching too much data, this only matters if it generates excessive
DNS traffic or causes unbearably long lookup latencies. And once again
this would be an administration/engineering problem, not one of protocol
design.

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From: "Eric A. Hall" <[email-masked]>
Date: Wed, 07 Aug 2002 17:44:57 -0500

> Bad assumption.  Assume LRU.  The rest of your statement doesn't

I'd actually be interested to find out what different vendors do, if they
care to share.