Path: utzoo!utgpu!watserv1!watmath!att!rutgers!ucsd!swrinde!cs.utexas.edu!chinacat!uudell!mustang!jrh
From: jrh@mustang.dell.com (James Howard)
Newsgroups: comp.unix.questions
Subject: Re: Ethernet question
Message-ID: <7492@uudell.dell.com>
Date: 15 Jul 90 20:05:09 GMT
References: <7490@uudell.dell.com> <23877@adm.BRL.MIL>
Sender: news@uudell.dell.com
Reply-To: jrh@mustang.dell.com (James Howard)
Organization: Dell Computer Corp.
Lines: 57

In article <7490@uudell.dell.com>, stecz@hotwheel.dell.com (John
Steczkowski) writes:
 > In article <23877@adm.BRL.MIL>, terry@cssun.tamu.edu (Terry
Escamilla) writes:
 > > 
 > > Someone please settle an argument we've been having at work.
 > > 
 > > Is it possible for a workstation on an Ethernet to dynamically
 > > determine the Internet (or even Ethernet) addresses of the
 > > hosts/workstations immediately to its left and right?  
 > > I guess this would be like an "intelligent" ping or ARP.
 > 
 > I believe you use /dev/right to find the ethernet id for the machine to
 > your right, but to get the ethernet id for the machine on the left, you
 > need the new GNU addon device driver /dev/ambidextrous.  Implementation of
 > these devices is hemisphere dependent, the default is for the northern
 > hemisphere (except of course for the UK, since there internet addresses are
 > backwards).

I thought there was a new 'proximity calculating protocol' (PCP) available
that will attempt to determine the nodes immediately adjacent to the local
machine.  First of all, you must be running with a nameserver, which is used
as a reference point.  You must know where the nameserver machine is located
relative to your own system.  Then, go edit the space.c file under
/etc/conf/pack.d/pcp and uncomment out one of the following lines as 
appropriate:

/* #define DIR_SERVER	LEFT	*/
/* #define DIR_SERVER	RIGHT   */

Then, rebuild a kernel.  At which point, the driver executes 'ping' on
each host
recognized by the nameserver and saves the average round-trip time in
ms.  Then,
the shortest two values are returned as the most nearly adjacent systems
available.
At this point, the definition of DIR_SERVER above becomes important. 
For example,
if DIR_SERVER = LEFT, then the lowest time is assumed to belong to the machine
closest to the nameserver, hence on the left.  In the alternate case, it
must be
on the right side.  Of course, this is difficult if the shortest times
are identical,
or if the load average on the machines are not all identical, of if ....


No one is really taking this seriously I hope...  ;-)


---------------------------------------------------------
James Howard
Dell Computer Corp.
jrh@mustang.dell.com 

The opinions expressed are my own, and not necessarily
those of my employer.  
---------------------------------------------------------