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From: mohta@necom830.cc.titech.ac.jp (Masataka Ohta)
Newsgroups: comp.unix.internals
Subject: Re: Shared libraries
Message-ID: <177@titccy.cc.titech.ac.jp>
Date: 11 May 91 04:46:47 GMT
References: <1991May9.135637.5408@batcomputer.tn.cornell.edu> <172@titccy.cc.titech.ac.jp> <1991May10.134839.23763@batcomputer.tn.cornell.edu>
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In article <1991May10.134839.23763@batcomputer.tn.cornell.edu>
	shore@theory.tn.cornell.edu (Melinda Shore) writes:

>>The change [array of host addresses] was introduced with 4.3BSD to meet
>>the requirements of DNS.

>Now, here's the hard part - keeping in mind that while correlation
>often implies causality it doesn't prove it, can you explain *why* the
>introduction of a distributed mechanism would cause a change in the
>information being provided?

Read all RFCs or make a question in an appropriate newsgroup.

>Is there a necessary relationship between
>delivery mechanism and the content of the thing being delivered?
>Comments in source code don't count - we're looking for understanding
>and explanation, not rote repetition.

Comments in source code do count. But if you need more evidence, you
should investigate gethostbyname() of 4.3BSD by yourself. When /etc/hosts
is searched, it dose not return multiple IP addresses.

Thus, the capability to return multiple IP addresses are added because of
DNS.

>And, as some one else pointed out, this particular change would not
>break existing binaries.

Existing binaries won't work well without modification and recompilation.

For example, if you are running old sendmail, it should try all IP addresses
of a particular host. It is often the case that a gateway host shutdown one
of its interface for a logn period. Then, if sendmail only tries one IP
address of the unfunctioning interface, it can't deliver mail to the host.

						Masataka Ohta