The following parameters are defined for a switching network: N $=4=$ number of hops between two given end systems L $=6000=$ message length in bits B $=$ data rate, in bits per second $($bps$),$ on all links P $=1080=$ fixed packet size, in bits H $=80=$ overhead $($header$)$ bits per packet S $=0\mathrm{.}2=$ call setup time $($circuit switching or virtual circuit$)$ in seconds T $=0\mathrm{.}02=$ call teardown time $($circuit switching or virtual circuit$)$ in seconds D $=0\mathrm{.}001=$ propagation delay per hop in seconds