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From: jaap@mcvax.UUCP (Jaap Akkerhuis)
Newsgroups: net.lan
Subject: Stretching the Ethernet specs
Message-ID: <425@mcvax.UUCP>
Date: Wed, 23-Jan-85 12:55:16 EST
Article-I.D.: mcvax.425
Posted: Wed Jan 23 12:55:16 1985
Date-Received: Mon, 28-Jan-85 07:05:13 EST
Reply-To: jaap@mcvax.UUCP (Jaap Akkerhuis)
Organization: CWI, Amsterdam
Lines: 50


According to the Ethernet specification Versions 1.0 and 2.0:

       "A maximum of two repeaters (or four half- repeaters, i.e. two remote
	repeaters) may be in the signal path between any two transceivers on
	the channel"

	Ethernet Specification  Version 2.0, November 1982, Paragraph 7.6.4,
	page 83.

To my suprise I'm offered two different brands of repeaters, which claim they
can have more then two.

Sension claims a maximum of six, and Isolan (Manufacturer BICC data networks
LTD) 4.

I don't have (yet) the info about Sension, but to quote the Isolan sales
blurb:

       "It performs signal retiming and communication between the two segments
	(...). Longer distance links between segments up to 2km (!) apart can
	be implemented width two (not two half-repeaters?) repeaters and fibre
	optic transceivers.
	Because each repeater fully regenerates each packet including
	preamble, up to 5 segments may be connected in series, allowing a
	network to be extended to 3km in diameter. The repeater performs the
	functions of regenerating preamble, extending collision fragments,
	enforcing the inter-packet gap, and automatic partitioning of the
	netwerk in the event of a segment failure. (...) The repeater has been
	implemented with the minimum of components (...) "

The box also claims to have been designed to the following list of standards:
	ISO DIS 8802/3, IEC 380, IEC 435, IEEE 802.3, FCC 20780, ECMA 80 and 81,
	ECMA TR/19, VDE 0871, VDE 0875 level N.

(Everything in the parenthesis are my comments, or left out non-interesting
details).

Well, notice the contradiction in the statement.

Anyway, the big question is of course "Can this be true? Has anyone experience
with the named products?"

Both firms are based in Engeland so another question arises immediately:
Could this be another feed to the famous quote "It's British so it
probably doesn't work".

Please answer by mail and I summarize to the net.

	Jaap Akkerhuis, {seismo,decvax}!mcvax!jaap