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614 Chapter 16: Voice Techniques
Furthermore, Cisco CallManager and all phones, gateways, and applications may be distributed
across an IP network, providing a distributed, virtual telephony network.
The benefit of this architecture is improved system availability and scalability. Call admission
control ensures that voice QoS is maintained across constricted WAN links and automatically
diverts calls to alternative PSTN routes when WAN bandwidth is unavailable. Cisco
CallManager is installed on the Cisco high-availability server platforms, the MCSs. A Web-
browsable interface to the configuration database is available for remote device and system
configuration. HTML-based online help is available for users and administrators.
Cisco CallManager Version 3.0(4) significantly enhances the scalability, distributability, and
availability of the enterprise IP telephony solution. Multiple Cisco CallManager servers are
clustered and managed as a single entity. The capability to cluster multiple call-processing
servers on an IP network is unique in the industry and highlights the industry-leading
architecture of Cisco AVVID. Scalability for up to 10,000 users per cluster is provided. By
interlinking multiple clusters, system capacity can be increased to up to tens of thousands of
users per multisite system. Clustering aggregates the power of multiple distributed Cisco
CallManagers, enhancing the scalability and accessibility of the servers to phones, gateways,
and applications. Triple server redundancy improves overall system availability. TAPI
(Microsoft's telephone application interface) and JTAPI (Java's application programming
interface for Java-based computer-telephony applications) interfaces allow a rich set of Cisco
and third-party vendor IP-enabled voice applications to augment base system capabilities.
NOTE
The New Feature Release Notes section of the CCO is an excellent source of information and
is a good starting point to learn about new technologies and features supported in Cisco routers.
Quality of Service for Packetized Voice
QoS lets a network provide optimum service to voice and data traffic. QoS ensures that voice
traffic is prioritized over data and will always be delivered ahead of data. Cisco IOS offers a
broad range of QoS features. These features provide predictable network service by the
following:
·
Supporting dedicated bandwidth
·
Improving loss characteristics
·
Avoiding and managing network congestion
·
Shaping network traffic
·
Setting traffic priorities across the network
87200333.book Page 614 Wednesday, August 22, 2001 1:41 PM