HOW TO MEASURE A NETWORK ?

  • Performance parameters:

  • Latency: Time required to transfer an empty message between relevant computers.
    Sum total of
    1. delay introduced by the sender software.
    2. delay introduced by the receiver software.
    3. delay in accessing the network.
    4. delay introduced by the network.
  • Data transfer rate: is the speed at which data can be transferred between sender and receiver in a network, once transmission has begun. (bit/sec)
  • Message transfer time = latency + (length of message) / (Data transfer rate).
  • Bandwidth : is the total volume of traffic that can be transferred across the network.

Max. data rate (bit/sec) = carrier BW · log2 (1 + (signal/noise))

this maximum (Shannon's Limit) is theoretical, not reacheable in practice!

Ex.: phone line BW = 3 kHz, S/N = 30 dB = 1000 --> Max. data rate = 30 kbit/sec