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Cisco IP Telephony Solution Reference Network Design
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Chapter 1 IP Telephony Deployment Models
Single Site
In addition, this chapter describes the following special design considerations and variations to the main
deployment models:
·
This section describes how to adapt the IP Telephony deployment models to support a full-mesh
routing technology such as Cisco IOS Multiprotocol Label Switching (MPLS).
·
This section describes how to use a single TFTP server to service multiple clusters and how to
distribute TFTP functionality across multiple servers to provide load balancing and redundancy.
·
This section presents guidelines for designing you IP telephony network to provide accessibility to
users with disabilities, in conformance with U.S. Section 508.
Single Site
The single-site model for IP telephony consists of a call processing agent located at a single site, or
campus, with no telephony services provided over an IP WAN. An enterprise would typically deploy the
single-site model over a LAN or metropolitan area network (MAN), which carries the Voice over IP
(VoIP) traffic within the site. In this model, calls beyond the LAN or MAN use the public switched
telephone network (PSTN).
The single-site model has the following design characteristics:
·
Single Cisco CallManager or Cisco CallManager cluster
·
Maximum of 30,000 IP phones per cluster
·
PSTN for all external calls
·
Digital signal processor (DSP) resources for conferencing, transcoding, and media termination point
(MTP)
·
Voice mail and unified messaging components
·
Only G.711 codecs for all IP phone calls (80 kbps of IP bandwidth per call, uncompressed)
·
Capability to integrate with legacy private branch exchange (PBX) and voice mail systems
illustrates the model for an IP telephony network within a single campus or site.