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From: mark@cbosgd.UUCP (Mark Horton)
Newsgroups: net.lan
Subject: ISO Protocol Suite
Message-ID: <1158@cbosgd.UUCP>
Date: Tue, 27-Mar-84 01:56:03 EST
Article-I.D.: cbosgd.1158
Posted: Tue Mar 27 01:56:03 1984
Date-Received: Wed, 28-Mar-84 00:51:01 EST
Organization: AT&T Bell Laboratories, Columbus
Lines: 79

I just read the March 1984 issue of Systems and Software.  They
have 50 pages or so about different networking suites, with a
LOT of information about the ISO suite.  From what I can tell,
the ISO suite has come a LONG way in the last year.  It's starting
to look pretty good!

I haven't seen any discussion of this stuff on net.lan.  Is it a
well kept secret or is my ear to the wrong ground?  Is this info
largely accurate?  (I notice some glaring errors elsewhere in the
magazine, which makes me wonder.  But then the press is never noted
for getting the technical details right.  For example, check out the
story about how UNIX on an IBM PC has to be slow because there is no
memory management hardware.)

Apparently the major remaining problem with the ISO suite is that the
standards are still incomplete.  But most of them are at least to the
draft standard stage, and there are claims of some kludged implementations
to be demoed soon.  The major delay is that there won't be a virtual
terminal protocol draft proposal until Feb 1985.  (I wonder what's
wrong with ANSI X3.64, which seems to be equivalent to what they have
in mind.)

They have recently added a "connectionless mode" to the ISO model
(which, in my interpretation, already covered it), and now apparently
DOD is seriously considering adopting it as their standard.  (I don't
know where this leaves TCP/IP, probably on an equal footing, although
we all know that with networks, standardization is everything.)  One
section puzzled me:

	"The addendum to the referenc model rules out any cross
	mode operation above the transport level.  This means
	that the three layers above a transport connectionless
	service must also be connectionless while the three
	layers above a connection-oriented service must be
	connection-oriented."

Huh?  Aside from keeping those datagram weirdos off in their own corner :-),
what possible use is this restriction?  How can it be enforced?
There is an obvious advantage to building virtual circuits ala TCP
on top of datagrams ala IP - you only have to solve the internet
problems once for IP.  Is the above paragraph correct?  Can someone
motivate it?  Expecially since the end of the same page suggests
that one way to internetwork is to "build a connection in the network
layer (such as an X.25 virtual circuit) on top of a connectionless
network."

Another point of interest:

	"The most important of the differences is the addressing
	scheme for nodes.  IS specifies a much larger address
	space that can accomodate many networks and network nodes.
	ISO also ues a heirarchical addressing structure that allows
	for incorporation of existig networks.  The structure is
	easy to use and administer from within any subnetwork.

	An ISO heirarchical address begins with an internationally
	standardized segment that is broken into two domains.  One
	is controlled by CCITT.  The secod is controlled by ISO.
	These address segments are further broken down into zones
	such as country codes.  When the breakdown reaches the
	finer levels of detail, where one authority administrates
	one or a collection of ntworks, then that authority
	determines the addressing structure within that subdomain.

	ISO has pointed out the addressing inadequacies in the
	Internet protocol to the DOD.  The DOD is taking steps
	to modify Internet along the lins ISO suggested.  This
	brings the IP even closer to ISO."

Fascinating.  Does someone have details of this address structure?
Size, fields, etc?  I remember a 14 decimal digit plan for international
host numbering, but that didn't divide the world between ISO and CCITT
(which is a pretty strange division.)

More discussion, opinions, flames, and more detailed information
about the ISO suite are invited.  Can reasonable implementations exist?
Even in a PC?  (TCP/IP can be done on an IBM PC or less.)  Is there
a mailing list on the ARPANET somewhere talking about this?  (Is
INFO-TCP/IP still dead?)