Q1: How long does it take to transmit a 1200-byte packet over a 56 kbps dialup link?

A1: T_xmit = L / R = size_in_bits / data_rate

             1200 bytes x 8 bits/byte        9600 bits
          =  ------------------------  =  ---------------  =  0.171 seconds
                56 x 10^3 bits/sec        56,000 bits/sec



Q2: How long does it take to download Floppy.jpg (1.0 MB) over a 2 Mbps ISP link?

A2: T_xmit = L / R = size_in_bits / data_rate

             1.0 MB x 2^20 bytes/MB x 8 bits/byte       8,388,608 bits
          =  ------------------------------------  =  ------------------  =  4.2 seconds
                     2 x 10^6 bits/sec                2,000,000 bits/sec



Q3: How long does it take for a 32-byte ICMP packet from Calgary to reach Toronto?
   (assumptions: one way; ~3500 km; two-thirds the speed of light; ignore T_xmit)

A3: T_prop = D / s = distance / speed

             3,500 km x 10^3 m/km        3,500,000 m 
          =  --------------------  =  -----------------  =  0.0175 seconds
               2 x 10^8 m/sec         200,000,000 m/sec