DNS (BIND) versus NIS (YP) versus "/etc/hosts"

John_E_Little at cup.portal.com John_E_Little at cup.portal.com
Sat Feb 9 01:07:34 AEST 1991

We recently attached to the Internet, and are using a sun as the
gateway.  We had all sorts of problems, including ypserv going into
infinite loops and sendmail bouncing mail as "host unknown" because of
nameserver timeouts.  After fighting with yp, dns, and sendmail for
a while, I learned several things:

1 - yp is not very tolerant of network timeouts, like busy nameservers.
While yp returns a timeout error code, the gethostbyname() routine has
no way to pass this information to the caller.  It either succeeds or
it fails.  If a program uses gethostbyname() and times out, then
it usually assumes that the hostname is invalid.  This is bad.

2 - sun engineering does not care about fixing the problems.  I was
told that unless I provided a more specific reason for the sendmail
problems I was seeing, that they would not look at the problem.  Since
I needed source to provide the level of detail they desired, and I do
not have a source licence, they were basically telling me to stuff it.

3 - sun support was somewhat more helpful. Once I convinced them that
my problems were real, and pointed out a few unfortunate interactions
between yp and gethostbyname(), they started investigating and found
some areas of concern in sendmail.   However, they said that these
fell under the category of rfe's rather than bugs, and that engineering
would probably not fix them.  Their solution: get the berkeley version
of sendmail and use that instead of the sun version.  It's pretty sad
when sun is advising me to throw away their (allegedly) supported software
and run some pd alternative instead.

4 - *Everyone* I have talked to who has attached a sun to the internet
has experienced similar problems.  For a company who claims "The Network
is the Solution," sun has a long way to go.

5 - smail is quite a nice program, it comes with source, the organization
makes sense, and it needs very little tweaking to work with the Internet.
Our mail reliability is *much* higher since we ditched sun sendmail and
took yp off our gateway machine.

6 - you can rebuild the shared C library to use the bind resolver instead
of the standard sun yp stuff.  The bind sources are effective pd, so you
could roll your own combination of bind and yp and perhaps avoid some
other the problems.

This is not directly applicable to your situation, I suspect,  but may
give you some clues.


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