Until this point, we have focused on packet-switched networks, but for this chapter,
we shift our attention to circuit-switched networks. In circuit-switched networks,
connections between a particular source and destination are ï¬rst set up, then held
as data ï¬ows continuously through the connection, and then ï¬nally torn down.
Historically, non-blocking, circuit-switched networks were ï¬rst associated with the
telephone system. A call placed from one person to another represented a single con-
nection request. For the call to go through, an unused path through the network had
to be found and then allocated for