The PCM traces are two different RTP streams made specifically to record all analog or
digital signals that are either sent or received by the telephony ports of the Mediatrix unit.
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 start-up, 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 start-up 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
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
PCM Traces are usefull at identifying problems with:
- Echo in the network
- DTMF signals
- Caller ID signals
- Fax signals (or false Fax detection)
- Message Waiting Indicator signals
- Any other analog signal
- Any voice quality issue