| The statistics of telephone voice traffic are well-understood. |
| Years of measurement and study led to the development of a branch of
mathematics, queueing theory, for dealing with voice traffic. |
| The Poisson distribution (similar to the
normal distribution)
describes the statistics of voice traffic. |
| Voice traffic is |
| nearly homogeneous, |
| of constant (low) information rate, and |
| typical calls last a fairly long time (very long by computer standards). |
|
| Because of the low information
rate per call, many concurrent voice calls can be multiplexed: they can share a common
circuit because the circuit's information capacity greatly exceeds the requirements of a
single call. |
| Voice traffic is controlled by circuit switching:
routers keep track of
the connections from link to link, so each message is uninterrupted. |
| If I call TicketMaster
in Chicago, a circuit is established between here and there, and it stays open until I've
bought my Tori Amos tickets. |