On Tue, Aug 12, 2003 at 07:56:53PM +0700, Robert Elz wrote:
> queue limit there).   [And no, I didn't bother doing the arithmetic, even
> if I knew enough about 802.11 transmit procedures, which I don't, to figure
> out how many of the 19 packets should have departed the AP already via the
> wireless interface before the last of them arrived via the wired interface].

  The 802.11 preamble length is 192us, IIRC. The header length is 24
  bytes, there is a 4-byte CRC, and let's suppose the payload length is
  1500 bytes. 802.11 sends a 14-bit acknowledgement for each packet at 1
  or 2 Mb/s, and there are at least 10 microseconds between packets. So
  we have

    192us + (24 bytes + 1500 bytes + 4 bytes) * 8 bits/byte / 11 Mb/s +
    10us + 192us + (14 bytes) * 8 bits/byte / 1 Mb/s + 10us =

  1627us per full-sized packet transmitted. I guess that it takes a little
  more than 1516 * 8 / 100. ~ 121us to transmit a full-sized packet on an
  100Mb/s ethernet. In 1627us, 13 121us packets can arrive, So it seems
  that it is possible for all the packets to arrive at the AP on the wire
  interface before the second wireless packet has been fully transmitted.

Dave

-- 
David Young             OJC Technologies
dyoung@ojctech.com      Urbana, IL * (217) 278-3933