Ronja Twibright Labs

Measuring BER with ping on 2x Metropolis

Measuring Bit Error Rate on 2x Metropolis



  • 2 PC's to which Ronja can be connected
  • Full duplex AUI network cards or Half Duplex Reduction(s)
  • Access to one of the PC's or 3rd PC connected to one side of the link by full-duplex wired or fiber optic network.
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Connecting just electronics

If you are testing just bare electronics on the floor, connect the components according to the picture.

IP setup

Set up IP networking. If you are using half duplex reduction to emulate full duplex card, read how to emulate full duplex card on IP level.

Running ping

  • You can select payload length in ping. The flag for this selection varies depending on ping vendor. Select suitable one to get packetloss between 0% and 100%. 56 bytes are default. Use max. 1472.
  • If you have neither scientific calculator, nor access to www nor local running copy of Ronja web, then select only 14, 56, or 1472 bytes of ping payload
  • If the ping allows you to specify -c to send packet as soon as the previous one arrives, use this flag.
  • If you are using the -c flag, then run two instances of the ping at the same time (in different xterm windows or consoles).
  • Do not use the -f (flood ping) option. This would render the measured BER invalid.
  • Leave the ping to run long enough to have multiple dropped packets. The longer the better precision.
  • Press ctrl-c and read out the packetloss (in %)

Calculate BER

  • Online BER calculator
  • If ping payload is 14, 56, or 1472, use the graph, page 22 (PDF), (PostScript) with the correspondence between ping payload and ethernet payload
    Ping payloadEthernet payload
    1. nbits=8*ping_payload+400
    2. bgr=(1-packetloss/100)^nbits, where packetloss is in % (from 0 to 100) and x^y means x powered (exponentiated) to y
    3. ber=1-bgr
An expected information missing here?