[Bridge] Re: Small packets

Ben Greear greearb at candelatech.com
Mon Oct 29 08:48:54 PDT 2007

Andy Gospodarek wrote:
> On 10/29/07, Benny Amorsen <benny+usenet at amorsen.dk> wrote:
>>>>>>> "LS" == Leigh Sharpe <lsharpe at pacificwireless.com.au> writes:
>> LS> Standard e1000 hardware. The packets being bridged contain a VLAN
>> LS> tag, which is included in the 60 bytes.
>> The e1000 has VLAN acceleration. The VLAN tag is sent in a separate
>> register. If you do packet capture on the sender, the packet will
>> likely look 60 bytes long, even if it is 64 bytes on the wire.
>> The same thing happens on receive. Packet dumping with VLAN's is a bit
>> of a mess in Linux. If you're lucky you can find a card without VLAN
>> acceleration to do the packet dump.
>> /Benny
> Are these the lengths on the wire or when captured on the host?   The
> smallest VLAN tagged frame should be 68 bytes IIRC.  A tagged frame
> that is 64 bytes seems too small.

That is not correct per the 802.1Q VLAN RFC, though
I don't have the reference handy at the moment.

64 bytes is fine, vlan tagged or otherwise.


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Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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