Path: utzoo!attcan!uunet!mcsun!ukc!tcdcs!swift.cs.tcd.ie!dit.ie!alawlor
From: alawlor@dit.ie (Aengus Lawlor)
Newsgroups: comp.dcom.lans
Subject: Re: Multiple Novell Servers on on eEthernet
Message-ID: <7288.25e915df@dit.ie>
Date: 26 Feb 90 11:41:19 GMT
References: <539@opus.NMSU.EDU> <1990Feb20.113920.19222@hellgate.utah.edu> <7270.25e3b569@dit.ie> <1990Feb23.185608.8785@hellgate.utah.edu>
Organization: Dublin Institute of Technology
Lines: 58

In article <1990Feb23.185608.8785@hellgate.utah.edu>, haas@cs.utah.edu (Walt Haas) writes:
> In article <7270.25e3b569@dit.ie> alawlor@dit.ie (Aengus Lawlor) writes:
>>Two questions.
>>  1) Can somebody explain to me what ECONFIG is for?
> 
> When a Novell device puts a packet onto an Ethernet, it puts a header
> around it.  There are two standards for such headers:
> 
> 1) The original Ethernet or DIX (DEC/Intel/Xerox) standard, which
>    consists of:
> 	48 bit destination address
> 	48 bit source address
> 	16 bit protocol type
> 	...    user data
> 
> 2) The IEEE 802.3 standard, which consists of:
> 	48 bit destination address
> 	48 bit source address
> 	16 bit length
> 
> The two packet formats can be intermixed on one wire, because all Ethernet
> protocol types have numbers greater than the maximum legal 802.3 length,
> thus a received packet can be examined and assigned confidently to one
> class or the other.
> 
> HOWEVER the proper thing to follow the length field in format 2) is an
> IEEE 802.2 header.  Instead, Novell inserts an XNS checksum of all one's
> (I think I got that right).  This would appear to the world as an IEEE 802.2
> DSAP=FF and SSAP=FF.
> 
> Router vendors who support Novell protocols, such as cisco, deal with
> the DSAP=FF SSAP=FF packet as a special case.  I fear that this hack will
> break in the next year or two as the use of the 802.3 framing style becomes
> more widespread.  The easiest precaution, and the one that we take here,
> is to use the ECONFIG option which causes the Novell device to generate
> header format 1).  This makes the packet fully conformant to standard so
> there should be no problem.
> 
> Cheers  -- Walt
Thanks Walt.
This may be a stupid question, but what does this mean in practice. My ethernet
has a 3Com server (which I'm told uses XNS packets), a Netware server, and,
will probably have some workstations talking TCP/IP. 

Will Econfiged drivers for Netware allow, for instance, NetBios Broadcast 
Datagrams from a Novell station to be picked up by a 3Com station? Or will the 
standard header make Netware-TCP/IP messageing more straightforward? Or is 
EConfig just going to make life easier sometime in the future? 

(These are very much "inquiring minds want to know" types of questions. I'm
learning a lot here, and I appreciate any extra enlightenment you people out
there can through my way!)

Thanks,      Aengus
-- 
Aengus Lawlor    Dept of Computer Science.           Time flies like an arrow,
ALAWLOR@DIT.IE   Dublin Institute of Technology.     Fruit-flies like a banana
                 Kevin Street. Dublin 8. Ireland.