On 10/29/07, Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote: > Andy Gospodarek wrote: > > On 10/29/07, Benny Amorsen <benny+usenet@xxxxxxxxxx> wrote: > >>>>>>> "LS" == Leigh Sharpe <lsharpe@xxxxxxxxxxxxxxxxxxxxxx> 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. > > > Thanks, > Ben > > Ah, you are correct, Ben. Thanks for pointing that out. Section C.4.4.1 of the IEEE 802.1Q spec does state that 64-byte tagged frames are OK, but that is only if you are able to drop padding from a 64-byte untagged one. Transmitting a 60-byte frame on the wire is incorrect. _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
