Third Generation Packet Voice DSP Modules


Cisco’s second generation integrated services router (ISR G2) introduces new digital signal processors (DSP) with up to four times the capacity of the Packet Voice DSP Modules used in the 2800 and 3800 series ISR routers. The 2800 and 3800 series router use PVDM2 (2nd generation) DSP modules on the motherboard of the router, while the 2900 and 3900 series ISR G2 routers ship with PVDM3 slots on the motherboard. A variety of PVDM2 and PVDM3 modules can be inserted into the PVDM slots on the ISR or ISR G2 routers enabling a different number of voice terminations, hardware conference bridges (CFB), transcoders (XCODE), or media termination points (MTP) . The identifier at the end of the PVDM part number identifies the number of G.711 calls that can be terminated on a PVDM3 hardware module: •PVDM2-8 •PVDM2-16 •PVDM2-32 •PVDM2-48 •PVDM2-64 •PVDM3-16 •PVDM3-32 •PVDM3-64 •PVDM3-128 •PVDM3-192 •PVDM3-256 Each quantity of 16 in the PVDM part number represents one DSP resource. The PVDM2-8 module is ½ of a DSP, while the PVDM2-64 is four DSP resources. At the time of this writing, the DSP calculator available at has not been updated with the 2900 and 3900 series ISR G2 routers. The number of sessions that can be allocated per DSP is based on the millions of instructions per second (MIPS) required for the termination and the number of MIPS available on the DSP module. Medium and high complexity audio codecs require more resource (MIPS) than low complexity audio codecs. The PVDM3-256 can support the following number of connections: •256 - G.711 sessions (low complexity) •192 - G.729a sessions (medium complexity) •120 – iLBC sessions (high complexity) The ISR G2 router natively accommodates the PVDM3 modules, but can also accommodate the PVDM2 modules if an adaptor is used (PVDM2-ADPTR). The 2800/3800 ISR routers cannot use the new PVDM3 modules. An ISR G2 router can accommodate both PVDM2 and PVDM3 modules, but they cannot be in the same domain. The motherboard of the router is one domain, while each network module slot is a different domain. PVDM3 modules allow the sharing of one single DSP resource between different media resource functionality, while the PVDM2 modules did not due to DSP firmware challenges in the PVDM2 modules that has been rectified.

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