From: shava@hermes.oit.unc.edu (Shava Nerad Averett)
Subject: Re: 802.3 Non-Compliance (?)
Organization: University of North Carolina, Chapel Hill
Date: Wed, 2 Sep 1992 21:48:54 GMT

In article <1992Aug28.194558.4752@iplmail.orl.mmc.com> more@tcc.orl.mmc.com () writes:
>In this meeting (which unfortunately I wasn't in), the vendor made the statement
>that Netware Servers violate the 802.3. 

This is the gods' own truth.  Netware 802.3 (euphemistically called "802.3
raw" -- or "802.3 wrong" to some of us...;) has a frame type that looks 
like this:

	Preamble 	7 bytes
   	SFD		1 
	DestAddr	6
	SourceAddr	6
	Length		2
	Data		46-1500
	FCS		4

Real 802.3, with 802.2, looks like this:

	Preamble        7 bytes
        SFD             1
        DestAddr        6
        SourceAddr      6
        Length          2
        Data            46-1500
		DSAP	1st byte
		SSAP	2nd byte
		CONTROL 3rd, 4th (opt)
		Data and pad to minimum of 46...
        FCS             4	

But the real problem is that Netware *always* sets the *length* field to
all F's, meaning that if you are (from what I understand) running DECNet
Phase V or OSI protocols which *believe* this field, you could end up 
with a lot of confusion, because the packet will not be the length adver-
tised.

This is the only shred of verity I can find in the vendor's statement.
This has, however, nothing to do with collision detections and such.
Generally that's all in hardware...

>His statement was that when a netware
>server detects a collision, that rather than following the random backoff, 
>in the Ethernet world, the Netware server immediately attempts to retransmit
>the collided packet(after sending the jam sequence). This vendor stated that
>because of this, TCP/IP based systems running on the same ethernet as Novell
>netware servers could experience some performance problems due to the 
>noncompliant nature of the netware server. He further stated that for this
>reason, NASA has put a ban on Novell Netware at it's sites. 
>
I don't know about NASA, but IPX and IP are the two major protocols on our
campus, and they don't seem to have any difficulty at all living on the
same wires.  Could NASA be playing with OSI?

Note, that Netware *can* use Ethernet_II rather than Ethernet_802.3 in 
the configuration statement, and completely obviate even this argument.
Or Ethernet_SNAP...

>I personally feel that this is mostly a bunch of BS. I'm an open systems kinda
>guy, but I find it hard to believe that Novell would flagrantly violate the
>rules of engagement in CSMA/CD.
>
Well, for one thing, they probably wouldn't have the option.  They use boards
that use chips that have that layer in silicon, and nothing they did would
probably be able to mess with it from a driver standpoint.  Besides, the
.LAN files (netware 2.x/3.x drivers) are generally written by the vendors
(in compliance with Novell's standards, but...) and I doubt the vendors
would write radically non-compliant drivers on purpose without raising a
fuss (am I an idealist...? ;).


-- 
Shava Nerad Averett				shava_averett@unc.edu
/*  all materials (c)1992, Shava Nerad Averett, and have nothing significant
    to do with the University of North Carolina, a mostly owned subsidiary 
    of the NC Legislature, a mostly owned subsidiary of the DOT.      */
Newsgroups: comp.dcom.lans.ethernet