Using Standard Ethernet V2 and IEEE 802.3 simultaneously

Using Standard Ethernet V2 and IEEE 802.3 simultaneously

Post by Wouter Lieftin » Fri, 02 Apr 1999 04:00:00



Couldn't find anything in the documentation.

As you know, there are two variations of ethernet around, Ethernet V2
(the original Xerox standard) and IEEE 802.3 (the IEEE variant).

I need to use them both, simultaneously on the same wire from a Linux
box, so that they form a different subnet. For instance, 10.0.1.0/24 is
standard ethernet, and 10.0.2.0/24 is IEEE.

Any suggestions on how to do that? I use Red Hat 5.2 with the default
kernel (2.0.36 or so) but don't mind upgrading/experimenting etc.

I know on AIX this is not a problem: en0 is standard ethernet and et0 is
IEEE ethernet, both are interfaces to the one and only ent0 device.

Regards, Wouter.

 
 
 

1. Support for Ethernet V2 and IEEE 802.3


|>
|> >1.  How do you know which type of Ethernet frames a particular machine/program
|> >    is sending?
|> There is only one difference in the frame format. The 2byte type field
|> of Ethernet V2 is a length field in 802.3. As most of the defined types
|> (at least the registerd ones) are outside the packet size range of ethernet,
|> you could use this to differentiate.
|>
Well, almost. There is a Novell format which isn't 802.3, but does use
the length field instead of a type field. The first two bytes of
what would be the 802.2 header (the DSAP and SSAP) are both FF, so that's
what is required to differentiate those.

Also, there is another minor difference. For DIX Ethernet frames, the
minimum length is guaranteed by the code above the layer 2 driver. For
802.3, the layer 2 driver must pad to minimum length on transmission, and
remove the pad on receipt.

|> >2.  Is it necessary for you, assuming you are writing some networking application,
|> >    to expect both types of frames to be sent to you?
|> Normally not, except you write some special application which has to
|> gateway between different protocols.
|> If you use some standard protocol like IP, OSI, DECNET as your underlying
|> transport protocol, you even did not have to fiddle around with that
|> differences.
|>
|> >3.  Is Ethernet V2 ever going to be phased out, or will it need to be supported
|> >    indefinitely?
|> Nope, as TCP/IP which is one of the largest installed base on Ethernet
|> uses V2.
|>
|> Sincerely,
|> Klaus
|> --
|> Klaus Steinberger               Beschleunigerlabor der TU und LMU Muenchen
|> Phone: (+49 89)3209 4287        Hochschulgelaende
|> FAX:   (+49 89)3209 4280        D-85748 Garching, Germany

Regards,
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