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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!rutgers!rochester!rit!mjl
From: mjl@cs.rit.edu
Newsgroups: unix-pc.uucp,comp.sys.att
Subject: Re: Machine names on the net ...
Message-ID: <1530@cs.rit.edu>
Date: 14 Jan 90 18:07:48 GMT
References: <33@suntau.UUCP> <25902@cup.portal.com>
Sender: news@cs.rit.edu
Reply-To: mjl@prague.UUCP (Michael Lutz)
Followup-To: unix-pc.uucp
Organization: Rochester Institute of Technology, Rochester, NY
Lines: 49

In article <25902@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes:
>forrie@suntau.UUCP (Forrie Aldrich) in <33@suntau.UUCP> writes:
>
>	I am confused about names of computers... I have been told that you can
>	only have a maximum of 6 characters for a machine name... 
>
>	Could someone please explain the limitations, and the why's?  I sure
>	would appreciate it.  I have looked into books, etc... and nothing
>	specific...just generalizations.
>
>The Usenet protocols were based on the (then) Arpanet protocols (now known as
>the Internet (collectively, due to what connects onto it)).

Not quite.  The USENET message interchange format has some relationship
to SMTP, and is now and Internet standard (I think), but has nothing to
do with machine names.  Nor is the 6 character limit the result of the
use of DEC systems on the early Internet.  Instead, it is a limitation
in some versions of UUCP -- definitely a Unix artifact, and in no way
connected with any Internet standard.

Most UUCP systems use the destination site name to set up control
files, which are then processed by uucico (a separate program) to do
the file transfers.  Uucico determines the destination by examining a
fixed portion of the control file name -- on Unix systems based on the
V7 version for the PDP-11 (such as BSD), this field was 7 characters
long.  However, one of the early commercial releases from AT&T (System
III or and early rev of System V) used only 6 characters.

To avoid chaos on the UUCP network, the convention was adopted that all
sites are unique in the first 6 characters.  This helps insure mail,
etc., will get through arbitrary forwarding sites.

Sites on the Internet proper, with no direct connection to UUCP, need
not obey these conventions.  And, indeed, "snorklewacker" or whatever
may be unique in the first 6 characters, so the others are simply
ignored (sort of like some C compilers' handling of external
identifiers :-( ).

There are some sites, such as uunet, that explicitly advertise the
ability to handle longer site names, some of which may specify
gatewaying to the Internet (or other network).  Thus, I *think* the
following will work to send mail to foo.baz.bar on the Internet:

	...!uunet!foo.baz.bar!recipient

Mike Lutz
Mike Lutz	Rochester Institute of Technology, Rochester NY
UUCP:		{rutgers,cornell}!rochester!rit!mjl
INTERNET:	mjlics@ultb.isc.rit.edu