Hi,
What you should decouple is the minumum 64 octet Ethernet requirement
from the actual use of these octets.
The 802.1Q spec only tells you that if the Ethernet II header contains a
type value of 0x8100 the next two octets are to be interpreted as VLAN
tag. That defines use.
When a frame is present on the wire it needs to be minimum 64 octets,
whatever the use of these octets.
These are seperate things.
Hope it helps,
Jaap
On Wed, 18 Jan 2006 Ran.Shenhar@xxxxxxxxxxx wrote:
> TnX Jaap,
> I know the CSMA/CD principles behind the 64 byte minimum requirement.
> However, my question is really focused on the 802.1Q change (or no change)
> in that demand, and I didn't understand the answer for that issue from your
> answer.
> Could you please try to clarify?
>
> TnX
>
>
>
> Jaap Keuter
> <jaap.keuter@xs4a
> ll.nl> To
> Sent by: Ethereal user support
> ethereal-users-bo <ethereal-users@xxxxxxxxxxxx>
> unces@xxxxxxxxxxx cc
> m
> Subject
> Re: [Ethereal-users] (Slightly OT)
> 18/01/2006 11:54 Ethernet length question
>
>
> Please respond to
> Ethereal user
> support
> <ethereal-users@e
> thereal.com>
>
>
>
>
>
>
> Hi,
>
> The layer protocol model is the best reference you can take in mind.
> The minimum ethernet frame length (that is bits on the wire) is 64*8.
> Together with the wirespeed this gives a minimum amount of transmission
> time. This time is needed for the other endpoint (in a point-to-point
> link) or other stations (on a shared medium) to assure recognition of the
> frame and collision avoidance. All this is Physical layer stuff.
>
> Then comes the meaning of the bits in the frame. If the ethernet header
> says that it's a VLAN tag that is following then the next 2 octets are to
> be interpreted that way. From there on the next protocol layer starts.
>
> That is the true meaning of VLAN, a VIRTUAL LAN. It's not a real one, as
> seen on the wires, but on a layer above that.
>
> Hope it helps,
> Jaap
>
>
> On Wed, 18 Jan 2006 Ran.Shenhar@xxxxxxxxxxx wrote:
>
> > Hi All,
> > I need help with a non-ethereal specific - I know that an ethernet frame
> is
> > of minimum length = 64 bytes, including FCS.
> > However, what is the minimum length of a VLAN tagged ethernet frame? Is
> it
> > 64+4, or is it still 64?
> >
> > I tried looking in IEEE 802.3q 2003 edition, however I was not able to
> find
> > a definite answer.
> > If you could also point me to a reference about the answer, it'd be even
> > better.
> >
>
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