Fulko, Guy thanks for explaining this!
regards, martin 2011/6/7 Guy Harris <[email protected]>: > > On Jun 6, 2011, at 3:02 PM, Martin T wrote: > >> As you can see, every second I sent and received one frame. The >> question is, why is the frame, which I receive, 18 bytes longer than >> the one I sent? I mean what are those 144 0-bits at the end of the >> each frame back from the hardware loop? > > Padding. Ethernet requires that a frame be a minimum of 64 octets if you > don't include the CRC at the end (64 octets if you include the CRC). If you > send a 42-byte frame, and you "receive" it by the networking stack on your > machine "looping back" the packet as capture input, you will receive a > 42-byte frame; however, on the wire, that frame will have an additional 18 > bytes of padding added to it, and if you receive it from the Ethernet > adapter, you will see the additional padding bytes. > > - > This is the tcpdump-workers list. > Visit https://cod.sandelman.ca/ to unsubscribe. > - This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
