Ethereal-users: Re: [Ethereal-users] question about layer 2 in ethereal ?

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From: Richard Urwin <richard@xxxxxxxxxxxxxxx>
Date: Fri, 28 Nov 2003 16:45:36 +0000
On Friday 28 Nov 2003 3:47 pm, john g wrote:
> question about Layer 2 info displayed in ethereal
>
> difference between "IEEE 802.3" and "Ethernet II" ?
>
> since i am capturing frames on a 10/100 ethernet the
> layer 2 info should have been "IEEE 802.3", instead it
> is shown as "Ethernet II" (and type is IP 0x0800)
>
> it is commonly understood that ethernet 10/100 is ieee
> 802.3 ? is that correct ?
> only for some common cisco protocols like cdp packets
> the layer 2 shows up as ieee 802.3 ?
>
> so it seems that there is a difference in
> encapuslating the layer2 frame ? (between ethernet II
> and 802.3) is that correct ?

Yes.
Ethernet II encodes the protocol type of the next layer in the same two bytes 
that 802.3 encodes the frame length.
802.3 then uses another layer to encode the next protocol type.

-- 
Richard Urwin