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Design inputs
A Communication Manager system can operate as an independent entity, or can be networked
together with other Communication Manager systems. For networked systems, the various
Communication Manager systems in the network are generally interconnected by IP tie trunks.
If the two members of a given pair of Communication Manager systems in a network are not
directly interconnected by tie trunks, calls between the two systems must be tandemed through
other Communication Manager systems in the network.
When there is a need to accommodate endpoints in various geographic locations, the customer
has the choice to either set up a single Communication Manager system with a site at each
location, or use a network of multiple Communication Manager systems to span the locations.
The choice of which one is more appropriate pertains to the issue of scalability. An extremely
large number of endpoints might mandate the use of multiple systems.
While Communication Manager systems have been designed with an IP infrastructure, they
also support circuit-switched endpoints, and the full complement of traditional DEFINITY
features. However, customers usually realize a significant advantage when those customers
implement an IP-oriented solution for systems that are geographically dispersed.
Each endpoint and Media Gateway is assigned to a Network Region when its IP address is
administered. Also, each Network Region is administered with a codec preference list, which is
a list of up to five codecs that are supported by that Network Region. Uncompressed G.711 and
compressed G.729 are the most commonly used codecs in Communication Manager systems.
Each Communication Manager system is administered with the Internetwork Region
Connection Management (IRCM) matrix, which provides enough information to specify which
codecs to use when completing a call between Network Regions.
Conversely, if the IRCM does not specify a codec set between two Network Regions, calls
cannot be completed between those regions over an IP connection. For instance, the manager
of an office building can use a single Communication Manager system to service all the
individual lessees, with a separate Network Region for each company. Those Network Regions
generally would not be connected by the IRCM because independent companies would be
unwilling to share each others' resources. Subsequent sections of this chapter further explain
sharing resources across connected Network Regions.
Multiple Communication Manager systems are often networked together by IP tie trunks,
although circuit-switched tie trunks can also be used. If the two members of a given pair of
Communication Manager systems in a network are not directly interconnected by tie trunks,
calls between the two systems must be routed through other Communication Manager systems
in the network, or through the public switched telephone network (PSTN).
Although Avaya products are IP enabled, the products must interface with circuit-switched
endpoints and systems. For example, Communication Manager systems require
circuit-switched trunks to access the PSTN because central offices today are not equipped for
IP trunking. Some customers also prefer to continue to use their circuit-switched telephones in
Communication Manager systems.
Circuit-switched endpoints interface to circuit packs that reside in either an H.248 Media
Gateway or a traditional Port Network (PN). Although each Media Gateway belongs to one
particular Network Region, no correlation exists between PNs and Network Regions. PNs are
interconnected through a circuit-switched center stage or an ATM center stage (S8700
Multi-Connect systems) or an IP network (IP-Connect systems).
Issue 3.4.1 June 2005
143
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