Page 174 - CISSO_Prep_ Guide

describe a circuit dedicated to the use of one customer. Even
though the data sent over these private lines were digital, they
were still operating over an analog-based phone system;
therefore, their network speeds were quite limited.

The problems with a private line were cost and efficiency. The
private line itself could still be a single point of failure. A cut
cable would cause a denial of service on what may be a network
connection that was critical for business purposes.
Then came the idea of packet-switched networks. Instead of
sending all the data over a committed private line in one
streaming flow of data, the idea was to divide the data into
individual packets and send them individually over the network.
This meant each packet had to have an address so that it could
be routed toward its final destination.

Now the idea of moving to packet switching became possible.
Instead of using the switches in the central offices to establish a
fixed circuit for the traffic to route across, now each switch
would operate as a cloud and allow each packet of traffic to flow
across the network of switches in whatever manner was best at
the time. This allowed much more efficient use of the cabling
since each packet of traffic could take whatever path was
available at the time, and the traffic from many companies could
share the same communications channels instead of having an
expensive dedicated private line. However, since different
packets could now take different routes to the destination, new
problems arose. Packets could arrive out of order. Packets could
experience various levels of latency and arrive at various speeds,
causing jitter. However, this is still fine for data. Data is well
suited for bursty and variable traffic. By fragmenting data into