AudioCodes Mediant 800B MSBR User Manual page 200

The siprec protocol specifies the use of SIP, SDP, and RTP to establish a Recording
Session (RS) from the Session Recording Client (SRC), which is on the path of the
Communication Session (CS), to a Session Recording Server (SRS) at the recording
equipment. The device functions as the SRC, sending recording sessions to a third-party
SRS, as shown in the figure below.
Figure 19-1: SIP-based Recording where Device Serving as SRC
The device can record calls between two IP Groups. The type of calls to record can be
specified by source and/or destination prefix number or SIP Request-URI, as well as by call
initiator. The side ("leg") on which the recording is done must be specified. This recording
leg must be one that is interfacing with one of the IP Groups. Specifying the leg is
important as it determines the various call media attributes of the recorded RTP (or SRTP)
such as coder type.
The device can also record SRTP calls and send it to the SRS in SRTP. In such scenarios,
the SRTP is used on one of the IP legs for SBC calls. For an SBC RTP-SRTP session, the
recorded IP Group in the SIP Recording Routing table must be set to the RTP leg if
recording is required to be RTP, or set to the SRTP leg if recording is required to be SRTP.
For SBC calls, the device can also be located between an SRS and an SRC and act as an
RTP-SRTP translator. In such a setup, the device receives SIP recording sessions (as a
server) from the SRC and translates SRTP media to RTP, or vice versa, and then forwards
the recording to the SRS in the translated media format.
The device initiates a recording session by sending an INVITE message to the SRS when
the recorded call is connected. The SIP From header contains the identity of the SRC and
the To header contains the identity of the SRS. The SDP in the INVITE contains:

Two 'm=' lines that represent the two RTP/SRTP streams (Rx and Tx).

Two 'a=label:' lines that identify the streams.

XML body (also referred to as metadata) that provides information on the participants
of the call session:
•
<group id>: Logging Session ID (displayed as [SID:nnnnn] in Syslog), converted
from decimal to hex. This number remains the same even if the call is forwarded
or transferred. This is important for recorded calls.
User's Manual 200
Mediant 800B MSBR
Document #: LTRT-12813