Path: utzoo!attcan!uunet!wuarchive!udel!rochester!cornell!ken
From: ken@gvax.cs.cornell.edu (Ken Birman)
Newsgroups: comp.sys.isis
Subject: Re: Using ISIS in teaching distributed computing
Message-ID: <47109@cornell.UUCP>
Date: 15 Oct 90 15:39:02 GMT
References: <15516.27149de8@levels.sait.edu.au>
Sender: nobody@cornell.UUCP
Reply-To: ken@gvax.cs.cornell.edu (Ken Birman)
Organization: Cornell Univ. CS Dept, Ithaca NY
Lines: 36

In article <15516.27149de8@levels.sait.edu.au> macfs@levels.sait.edu.au writes:
>I'm thinking of using ISIS for the practical work in teaching....
>....the worst case scenario is that only [a single] Sun 4/490 could
>run ISIS, in which case there is no true distributed processing going on...

My group has heard from at least five or six departments about ISIS-based
courses.  My own experience doing this has been quite good, provided that
you don't change the system during the semester (around here, this happens
quite often).  Also, I usually ask people to implement some of the non-ISIS
protocols or system interfaces (i.e. Byzantine agreement, Linda tuple
space, etc) using ISIS as a communication environment only, so that they
get some experience with alternatives to the ISIS style of programming.

Regarding the single machine issue, this is not necessarily such a
restriction.  First, little ISIS code distinguishes the location of 
processes on a per-machine basis.  So, your students will write exactly
the same program whether they plan to run three copies on one machine or
one copy on each of three machines.  

Also, ISIS is capable of simulating a multi-site configuration on a single
machine. You use a slightly changed "sites file" format, in which the
machine name is qualified by a number, i.e.
	1: 2000,2001,2002 iserver.sait.edu.au/1 au
	2: 3000,3001,3002 iserver.sait.edu.au/2 au
	3: 4000,4001,4002 iserver.sait.edu.au/3 au
notice that the port-numbers are not repeated and that each machine has
a "private" name, if you count the /xxx part.

You will get a warning about possible problems with "isis remote" when you
start the system, but can ignore this.  (However, don't use isis_remote in
this configuration!).

The above mechanism was broken for V2.0 but is fixed in the general ISIS
V2.1 release.

Ken