Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!karn
From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: 802 (.2).3 TCP/IP
Summary: Ignore 802.2/3
Keywords: interoperability?
Message-ID: <1080@thumper.bellcore.com>
Date: 13 May 88 17:14:37 GMT
References: <1919@ssc-vax.UUCP>
Distribution: na
Organization: Bell Communications Research, Inc
Lines: 25

In my humble opinion, IEEE 802.2/3 is yet another standards committee
that the world would have been far better off without. The changes they
made to DIX (DEC-Intel-Xerox) Ethernet, already a well-proven de-facto
industry standard, were utterly gratuitious. The existing 16-bit type
field provided plenty of expansion room to build whatever additional
capability they wanted while maintaining compatibility with existing
protocol encapsulation formats.  The new "length" field not only breaks
compatibility, but is useless, redundant information for the protocols
that already ran on Ethernet since they have their own type fields.
(If a length field was considered necessary for other protocols, it
could have been provided AFTER the type field, and only for certain new
values in the type field).

Because the DIX Ethernet type fields are invalid as 802.3 length values,
it is possible to write packet receiver code that will accept, say, IP
datagrams in either DIX or 802.3 framing, but real problems come when
you need to decide how to SEND packets to another host you haven't
spoken to before.

I see only one easy answer to the gratuitous compatibility problems
imposed by 802.3: IGNORE IT!  Also be sure to tell the manufacturers
why. Maybe someday the standards-mongers will get the message.  (Begin
Bernstein music here) Someday, somehow, somewhere...

Phil