There are 2 methods to record VoIP phones, we call them Active VOIP recording or Passive VoIP recording. Let’s talk about passive VoIP recording in this post. The passive recording method is achieved by connecting the recorder to a monitor port of a switch (SPAN/RSPAN port). The monitor port receives all of the traffic for each trunk that needs to be recorded. The recorder captures all the traffic, including the RTP media streams and the SIP signaling messages. Passive SIP recording can be deployed almost anywhere on the network, depending upon which calls and call scenarios are required for recording. Usually, the SPAN is configured to either mirror all the SIP traffic for specific extensions to the recorder, or for mirroring SIP trunks when a only external calls are required for recording. SIP trunks usually connect the PBX with the PSTN gateways or establish a direct IP trunk connection with the service provider. Using Red Box Recording System, multiple recording servers can be deployed in order to support multi-site configurations or hosted office networks and/or high volume systems with or without redundancy.
The SIP RFC allows for almost any codec to be supported and as standard supports the most Common – these are G.711 (PCM either µ- or A-Law) and G.729A. Calls using any other codec would require minimal additional configuration.