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From: jmn@ariel.UUCP (J.NERVIK)
Newsgroups: net.lan
Subject: IP variants
Message-ID: <757@ariel.UUCP>
Date: Tue, 2-Oct-84 11:51:54 EDT
Article-I.D.: ariel.757
Posted: Tue Oct  2 11:51:54 1984
Date-Received: Wed, 3-Oct-84 19:36:58 EDT
Organization: AT&T-ISL, Holmdel, NJ
Lines: 43

[]	In looking at the documentation on IP, there appears to
be two dialects of IP.  This looks like chaos to me, and I wonder
if someone with perspective on these developments would clarify
the situation.

	One IP is specified in DARPA documents, mainly;

	-RFC-791, "Internet Protocol", September 1981.

Critical parameters include source-address and destination-address
as fixed length fields of 4 octets each.  The maximum header size
is 60 octets, but typically is 20 octets.  All hosts must be
prepared to accept datagrams of up to 576 octets.  This allows for
a 512 octet data field, a header, plus some octets for the higher
level protocols.

	The second IP is specified in ISO documents;

	- TC 97/SC6 N, "Information Processing Systems - Data
	  Communication Protocol for providing the Connectionless-Mode
	  Network Service", May 1984.  My copy has DIS8473 handwritten
	  on it.

	- Draft Proposal ISO/DP 8348/DAD2, "Information Processing
	  Systems - Data Communications - Addendum to the Network Service 
	  Definition Covering Network Layer Addressing", April 1984.

The source-address and destination-address are variable length fields of 
up to 20 octets or 40 digits each.  The maximum size of the header is 254 
octets.  Datagram size is not specified, other than to recognize that a 
datagram must at least hold one octet of data to have any use at all.

	The general features of these two IP dialects seems to be about
the same.  However, reading these documents is a good way to cure insomnia,
and I suspect a close reading will find many differences in detail.

	It is my understanding that the ISO documents have been generated
as part of the process to get RFC-791 accepted by the international
standard bodies.  The ISO documents describe a much fatter protocol.  Why???
Has the IP of RFC-791 been destroyed???  If ISO adopts these documents,
will ARPANET and/or MILNET switch to the ISO version of IP???

						John M. Nervik