Internetworks come in a variety of topologies and levels of complexity—from single-protocol,
point-to-point links connecting cross-town campuses, to highly meshed, large-scale wide-area
networks (WANs) traversing multiple time zones and international boundaries. The industry trend is
toward increasingly complex environments, involving multiple media types, multiple protocols, and
often interconnection to “unknown” networks. Unknown networks may be defined as a transit
network belonging to a Internet service provider (ISP) or a telco that interconnects your private
networks. In these unknown networks, you do not have control of such factors as delay, media types,
or vendor hardware....