Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site decwrl.UUCP Path: utzoo!linus!decvax!decwrl!dec-rhea!dec-bergil!lauck From: lauck@bergil.DEC Newsgroups: net.lan Subject: Ethernet 1 vs. Ethernet 2 vs. 802.3 Specifications Message-ID: <4178@decwrl.UUCP> Date: Fri, 9-Nov-84 10:18:36 EST Article-I.D.: decwrl.4178 Posted: Fri Nov 9 10:18:36 1984 Date-Received: Sat, 10-Nov-84 20:29:18 EST Sender: daemon@decwrl.UUCP Organization: DEC Engineering Network Lines: 33 >It is well known that the 802.3 Standards Committed is well influenced by >manufacturers who are entering the LAN market well after the emergence of >Ethernet 1 as a standard, and they went out of their way to make Ethernet 2 >(802.3) incompatible with Ethernet 1, to negate the market-place lead-time >that the existing Ethernet 1 manufacturers had gained. As one of the reviewers of Ethernet 1 and one of the developers of both Ethernet 2 and 802.3, I would like to correct a mistaken assumption. The changes between Ethernet 1 and 2 (most of which were adopted by the 802.3 committee) were instituted to correct problems with Ethernet 1 and to improve the system reliability and maintainability and, where possible, permit lower cost VLSI implementations. An example of a difference is the Collsion Detect Heartbeat signal (aka SQE Test). This signal makes it possible for a controller to detect that the tranceiver collision detect hardware (e.g. the cable) has failed. This protects the network from a run-away station which would otherwise not back-off. 802.3 and Ethernet 2 are quite similar. Most of the differences are in terminology, which is needed so that 802.3 can conform to the overall 802 terminology. The most significant differerence is in the frame format, a software (driver) issue in most implementations. There are several harware specification differences. Most of these are either clarifications, tightening of certain specifications to improve system margins, or relaxing of certain specifications to reduce product costs. No doubt there will be further changes along similar lines in future versions. As a member of the 802.3 committee when it was adopting the standard I can assure you that compatibility with existing equipment was a key concern. There were many representatives from companies with products on the market. However, this was not the only concern. The committee was also concerned with longer term technical issues, similar to those which motivated the change from Ethernet 1 to Ethernet 2.