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From: Mohamed Ellozy <ellozy@netman-mel.dfci.harvard.edu>
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Subject: Re: BIND 4.9.3 Beta11 Patch4 is available
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Date: Thu, 8 Dec 1994 23:20:47 -0500 (EST)
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In-Reply-To: <9412090153.AA07907@gw.home.vix.com> from "Paul A Vixie" at Dec 8, 94 05:53:28 pm
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Paul A Vixie writes
> 
> i am willing to look at checker if someone sends me a copy.

Date: Fri, 28 May 93 16:09:43 PDT
From: smiller@caldera.usc.edu (Stephen B. Miller)
To: ellozy@farber.harvard.edu
Subject: The Checker Project

Mohamed,

Please ftp from ~ftp/pub/checker on caldera.usc.edu for the code and 
documentation on our research work with the DNS query traffic that I 
mentioned yesterday.  Also included there is the announcement that I 
am mailing to the bind mail group about the project.

Stephen Miller

Its still there, here is the announce.txt:

The earlier request for aid from Mohamed Ellozy has prompted me to go
ahead and release some information on a project ongoing at USC that 
might be of some aid to others like him.  With this announcement I
am hoping to get some discussion on the concepts implied below, and
suggestions for things that I should be testing for.  Please feel free
to dredge up any old history as I have only been watching bind activity
for about a year and have only managed microscopic domains by comparison
to some of you.

                         The Checker Project

The following work is an extension of the paper titled "An Analysis of 
Wide-Area Name Server Traffic" by Danzig, Obraczka, and Kumar from the 
1992 SIGCOMM.  A postscript copy of the paper is available on anonymous 
ftp from caldera.usc.edu in the ~ftp/pub/checker directory.  Design,
coding, and testing has been conducted by Stephen Miller (smiller@
caldera.usc.edu), Peter Danzig (danzig@usc.edu), and Anant Kumar
(anant@isi.edu) in the USC networking research laboratory.

The Checker Project is an attempt to build onto named the ability to 
scan the incoming query traffic looking for client machines that may be 
experiencing problems getting their requests satisfied.  The project
itself is a set of C code that builds a database from the nameserver 
query and response traffic.  Whenever a query or response is passed 
through the checker code its timing and response code is checked against 
some historical parameters to see if the client's activity falls within 
some behavioral patterns previously identified with some broken resolver 
or nameserver implementations.  Reports are generated upon request and 
include such things as: activity summary, client address sorted by 
number of different queries, query name sorted by number of requests, 
and client addresses that have had behaviors that fall with the 
predefined patterns.

Knowing that Paul Vixie was putting immense effort into the 4.9 version 
I chose to make as few incursions into named as possible, which resulted 
in 5 lines of code being changed in each of ns_req.c and ns_resp.c (not 
including some ifdef/endif sets).  As far as I can tell the changes that 
we made to let us test with bind 4.8.3 are still valid in 4.9.  Even
though the code is present in the ftp directory mentioned above I would
respectfully request people to email me before taking a copy as there
are changes being made.  Please feel free to get a copy of the postscript
installation and operations guide.  Any comments on that are especially
welcome.  The C dialect is pretty generic, but testing has only been done
using SunOS; following Paul's style for handling multiple platforms is
on my list of things to do.

The current alpha version of Checker has been running one of the roots
for the US domain for a few weeks with no failures, under a load of
several thousand queries a day.  Our initial experiences show some good
stuff, along with some things to look at.  We have had no problem seeing
the clients that seem to be making a lot of absurd queries, but I doubled
named's dynamic memory usage at the same time.  Memory usage is configured
by the record cache time though, and I tend to run long periods on our
research machine. Other upgrades coming include altering the reports to
show query rates rather than absolute counts.  After running for a week
without rebooting the counts get very large, but divided by the time
factor show no real problem.

An interesting feature, currently disabled for the US domain testing, is
the ability for the program to randomly choose a query name, and eat all
replies to that name for a short (configurable) period of time.  The
theory behind this is that the client should choose another server pretty
quickly and stop using the one that isn't replying.  If the client keeps
asking then the DNS implementation the client is running may need to be
upgraded.  During the first phase of testing when I directed USC's 
networking laboratory toward a named-checker installation we found that
most of our installations behaved as predicted.  I have not turned this
feature on yet for the US domain as we still have yet to fully understand 
the passive mode for the larger amount of traffic.

Stephen Miller
University of Southern California
smiller@caldera.usc.edu.
