Gateway devices and Call Managers are not limited to geographical boundaries. A properly designed system
would easily provide the scalability, redundancy and fault tolerance that highly available networks require. The
unified communications approach relates very closely to the Internet model that the Department of Defense
designed. The Cisco Call Manager server clustering approach represents a highly available network model that
can meet disaster recovery requirements when aligned with the proper underlying quality of service (QoS)-
enabled infrastructure. QoS is the glue of the network that guarantees the quality level necessary for real-time
communications, such as voice and video....