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From: cayer@ireq.hydro.qc.ca (Cayer)
Newsgroups: comp.dcom.lans,comp.sys.novell
Subject: IPX Encapsulation over Ethernet
Message-ID: <6843@s3.ireq.hydro.qc.ca>
Date: 7 May 91 20:16:28 GMT
Sender: usenet@s3.ireq.hydro.qc.ca
Reply-To: cayer@ireq.hydro.qc.ca ()
Organization: IREQ, Hydro-Quebec, QC, Canada
Lines: 44


Using my sniffer, I have noticed the following encapsulation
of the IPX protocol over ethernet:

destination  source  length                       ...
 6 bytes       6       2                            .  MAC
                                                    .  layer
                                                  ...
checksum  length  transport  type                 ...
   2        2        1        1                     .  IPX
                                                    .  layer
destination network  node  socket                   .
               4       6     2                      .
                                                    .
source network  node  socket                        .
          4      6      2                           .
                                                  ...
                                                  ...
data                                                . Upper
                                                  ... layer

The third field of the MAC layer is a length field and not
a type field as in ethernet V.2.  

But, this is not IEEE 802.3 either since there is not an
IEEE 802.2 layer above the MAC layer.  The IPX packet is
directly over the MAC layer.

I think that this does not respect either ethernet nor
IEEE 802.3 encoding.

Can this cause problems inside a multi-protocols network 
(ipx, decnet, tcp/ip, ...) ?

I have heard that other forms of encapsulation do exist. 

So, I would appreciate if someone could tell me what are 
those other encapsulations, and why/when to use them.

Thanks.

--
Andre Cayer
cayer@ireq.hydro.qc.ca