bart@videovax.tv.Tek.com (Bart Massey) (02/18/89)
This may be a naive question, but: What kinds of bad things can happen when 802.3 and Ethernet packets are present on the same piece of wire? What are the hardware differences, if any, between 802.3 and Ethernet hardware? Bart Massey Tektronix, Inc. TV Systems Engineering M.S. 58-639 P.O. Box 500 Beaverton, OR 97077 (503) 627-5320 ..tektronix!videovax.tv.tek.com!bart
mah@hpuviea.UUCP (Michael Haberler) (02/19/89)
> What kinds of bad things can happen when 802.3 and Ethernet packets are > present on the same piece of wire? What are the hardware differences, > if any, between 802.3 and Ethernet hardware? Re: 802.3 vs. Ethernet packets: Should not be a problem, because they're easy to distinguish: Ethernet packets have the layout +------------------------------------------------------+ | dst adr | src adr | type field | data.......| crc-32 | +------------------------------------------------------+ 6bytes 6bytes 2bytes IEEE802.3: +------------------------------------------------------------------------+ | dst adr | src adr | length | LLC data (SAP's) | data.......| crc-32 | +------------------------------------------------------------------------+ 6bytes 6bytes 2bytes So, as no legal IEEE length consitutes a legal Ethernet type field ( types start around 0x800), they can be distinguished by looking at the type/length field value. IEEE MAUs (aka transceivers) define additionial signals, like Jabber (inhibit transmit of oversized packets). My experience is that one can use Ethernet controllers with IEEE 802.3 MAUs but not vice versa. -mah -- Michael Haberler mah@hpuviea.uucp Hewlett-Packard Austria GmbH, ...mcvax!tuvie!hpuviea!mah Lieblgasse 1 ...hplabs!hpfcla!hpbbn!hpuviea!mah A-1220 Vienna, Austria Tel: (0043) (222) 2500 x412 (9-18 CET)
pat@hfsi.UUCP (Pat) (02/20/89)
In article <5379@videovax.tv.Tek.com> bart@videovax.tv.Tek.com (Bart Massey) writes: >This may be a naive question, but: > >What kinds of bad things can happen when 802.3 and Ethernet packets are >present on the same piece of wire? What are the hardware differences, >if any, between 802.3 and Ethernet hardware? > Bart Massey There are no hardware differences between 802.3 and ethernet v1.0 and v2.0 Now there are some protocol differences in how the packets are laid out, specifically in the legth field and when packets are < 46 Bytes. There is no hardware incompatibility (Physical layer) . There are some problems at the Media access control layer. Read the Bridge document on ethernet 802.3 compatibility. So the products may not exactly talk, they arenot mutually exclusive and with a little tweaking can be made to communicate. Your right it is naive, but we all start that way. Pat "8802 in my sleep" bahn