The PCM traces are two different RTP streams made specifically to record all analog signals that are either sent or received on the analog side of the Mediatrix.
These RTP streams are sent to a configurable IP address, normally an IP address on your network where it can be recorded with a packet sniffer (such as Wireshark). Moreover, they are independent from the regular RTP streams of the VoIP call. On the analog devices, the streams are sent instantly at device startup, with an average ptime of 5 ms. The resulting streams, depending on the model, are around 15 kB/s.
Only the configured port, port #1 and/or #2 send the PCM traces for a maximum of four simultaneous RTP streams.
All streams are sent instantly at startup with an average ptime of 15 ms. This means that until the PCM traces are disabled, even an idle unit will continuously send up to 66.6 packets/s X 4 streams = 267 packets/s using approximately 174 bytes each, for a total of 46 Kbytes of upstream bandwidth.
On digital devices, the streams will be sent once a call is in process of being established (ISDN SETUP, SIP INVITE). This means no data will be sent if the gateway is idle with no calls in progress.
PCM Traces is efficient at identifying problems with:
The test calls must be done on port #1.
This IP address does not have to be listening on ports 5001/2 – 6001/2, as it is easy to filter out ICMP “port unreachable” messages afterwards.
Enabling PCM traces on a 1204
If G.723 is available, you MUST disable the G.723 and enable the G.726 codec to load the PCM code into the 1204. This can be done by setting the voiceIfCodecG723Enable MIB variable to disable and the voiceIfCodecG72616kbpsEnable MIB variable to enable in the voiceIfMIB.
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