VoiBRIDGE / VoxiPlus INSTALLATION MANNUAL
© 2008 TOPEX S.A.
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Routing calls
Routing is the process of selecting paths in a network along which to send data or physical
traffic. Routing is performed for many kinds of networks, including the telephone network, the Internet,
and transport networks.
Routing means a process of retrieving a route from the calling party to the called one. There
are various routing methods according to the type of call and place from which the call is coming.
The routing process usually directs forwarding on the basis of routing tables which maintain a
record of the routes to various network destinations.
Speaking of routing within a single VoIP network, we think of the activity executed by the PBX
whenever a registered user initiates a new call.
The result of this process is a route to another registered user based on the called number
analysis. The called number can be an IP telephone, GSM gateway, PSTN gateway, another IP PBX,
etc.
Figure 2 – VoIP Call routing to IP or Mobile
The routing options are dependent on the capabilities of the particular PBX. For SIP-based
telephones, a SIP proxy server can be used as a PBX.
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VoIP to GSM routing
An incoming call from the IP network (VoIP call using SIP or H323 protocol) is analyzed by the
Least Cost Router (LCR). The LCR decides which line the call shall use for going out. The decision
depends on the called number and LCR settings.
Figure 3 – Least Cost Routing
The Least Cost Router is designed primarily for searching the most cost-efficient route to a
GSM network, it is not limited just to this function.
Generally, it can interconnect incoming calls from VoIP lines to any lines that are available in
the gateway regardless of their types. This is very useful for interconnecting heterogeneous VoIP
networks, such as SIP and H.323 environments.
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