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How to calculate the number of DSPs required on a Cisco IOS voice gateway in order to provide conferencing and transcoding information



The Digital Signal Processor (DSP) Resource Calculator is a web-based tool that helps calculate the number of DSPs required on the system. It also determines the number of calls that can be handled simultaneously, taking into consideration each of the Coder-Decoder (codec) standards. This tool requires information such as the platform type, Cisco IOS  release number, Voice Interface Card (VIC) slot configuration, and the type of codecs to be used on these interfaces. The tool then displays the number of DSPs required to run the configuration and generates the configuration required in order to start the system. Refer to the DSP Calculator in order to see the DSP Resource Calculator application.

In addition, refer to the Configuring Enhanced Conferencing and Transcoding on Voice Gateway Routers section of Cisco CallManager and Cisco IOS Interoperability Guide for more information on how to use Table 5 to show conferencing session limits per DSP.

In theory a DSP chipset resource is either allocated for conferencing, or voice termination/transcoding, due to the different firmware code loaded onto the DSP at router boot time. In other words, if there are unused resources in the voice termination/transcoding DSP, it cannot be allocated to perform conferencing. For conferencing, each DSP is capable to hold eight G.711 sessions, or two G.729 sessions. When a conferencing session is started, the whole DSP is utilized irrespective of the number of parties.

Refer to Relevant Interfaces and Modules for more information about interfaces and modules.

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