Passive call recording method for SIP and H.323 trunks

The passive recording method is achieved by connecting the recorder server to a monitor port of a switch (SPAN/RSPAN port). The monitor port receives all of the traffic for each trunk that need to be recorded. The recorder captures all the traffic, including the RTP media streams and the SIP/H.323 signaling messages. SIP trunks usually connect the call control server with the PSTN gateways or establish a direct IP trunk connection with the service provider. Using Verba Recording System, multiple recording servers can be deployed in order to support multi-site configurations or branch office networks and/or high volume systems with or without redundancy.

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  • Due to the nature of the passive recording method, there is no extra bandwidth or resource requirement from the network or call control servers.
  • There is no connection to the call control server(s) or usage of TAPI/JTAPI.
  • In case of call control server failure, the recording system is not affected, the recording can work continuously if survivable telephony functionality is available on the site (e.g. Cisco SRST - Survivable Remote Site Telephony). In this case, a recording server is deployed at the site.
  • Because of the passive approach, the flow of the call is not affected at all.
  • Can be easily deployed and maintained.
  • Using Verba Recording System multi-site deployment architecture, the system can be adapted very well to a wide array of use cases.
  • If high-volume traffic should be recorded, the system can be scaled easily by adding new recording servers.
  • All types of calls traversing the monitored SIP/H.323 trunk can be recorded independently of the PBX or phone type.
  • Monitor port technology is widely used approach.
  • In most cases it can be easily configured and used.
  • Silent monitoring can be supported natively by the recorder.
  • Mobile phones can be recorded if the calls are routed through a SIP/H.323 based mobile adapter (makes sense for transferred or forwarded calls only).


  • Encrypted calls cannot be recorded.
  • Internal calls between IP phones cannot be recorded, because these calls are not traversing the trunk.
  • Only SIP and H.323 trunks are supported by Verba Recording System (MGCP is not supported).
  • Automatic announcement of the recording cannot be done by the recorder itself. An external IVR or TCL script on the gateway should be involved.
  • Phone number information for internal extensions might not available, if number translation hides internal numbers from the PSTN.


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