Assuming a Cisco 3825 router, if the Cisco SCCP phones on the network are using G.711 µ-law and are traversing a CUCME system connected to a SIP trunk that supports G.711 µ-law, is a PVDM2 DSP card required since the codecs are the same? Does having a Unity Express module installed on the system require a DSP card?
2 Answers
You should be good without DSPs. The major use of DSPs on a router is when you have to convert from a TDM trunk (FXO or T1/PRI) to an IP resource. Since SIP is all IP-based, you shouldn't have to do any conversion.
Do be aware that any conference calling features will consume DSPs unless you have a hardware conference bridge.
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It depends on whether or not transcoding is required. If you are using a codec in-house that is incompatible with your SIP providers gateway then yes. Otherwise, no.
Same with Unity Express voicemail. If the voicemail is using the codec you run in-house, no transcoding required. However if you are compressing voicemails (recording them in g.729, for example), then you will have to invoke the DSP to transcode. Otherwise, users can't leave VM's.
answered Feb 2, 2017 at 15:35
