AudioCodes Mediant 800B User Manual page 426

Parameter
Behavior]
RTCP Mode
sbc-rtcp-mode
[IPProfile_SBCRTCPMode]
User's Manual
According to the RTP redundancy SDP offer/answer negotiation,
the device uses or discards the RTP redundancy packets. The
parameter enables asymmetric RTP redundancy, whereby the
device can transmit and receive RTP redundancy packets to and
from a specific SIP entity, while transmitting and receiving regular
RTP packets (no redundancy) for the other SIP entity involved in
the voice path.
The device can identify the RTP redundancy payload type in the
SDP for indicating that the RTP packet stream includes redundant
packets. RTP redundancy is indicated in SDP using the "red" coder
type, for example:
a=rtpmap:<payload type> red/8000/1
RTP redundancy is useful when there is packet loss; the missing
information may be reconstructed at the receiver side from the
redundant packets.

[0] As Is = (Default) The device does not interfere in the RTP
redundancy negotiation and forwards the SDP offer/answer
(incoming and outgoing calls) as is without interfering in the
RTP redundancy negotiation.

[1] Enable = The device always adds RTP redundancy
capabilities in the outgoing SDP offer sent to the SIP entity.
Whether RTP redundancy is implemented depends on the
subsequent incoming SDP answer from the SIP entity. The
device does not modify the incoming SDP offer received from
the SIP entity, but if RTP redundancy is required, it will be
supported. Select the option if the SIP entity requires RTP
redundancy.

[2] Disable = The device removes the RTP redundancy payload
(if present) from the SDP offer/answer for calls received from or
sent to the SIP entity. Select the option if the SIP entity does not
support RTP redundancy.
Notes:

To enable the device to generate RFC 2198 redundant packets,
use the IPProfile_RTPRedundancyDepth parameter.

To configure the payload type in the SDP offer for RTP
redundancy, use the RFC2198PayloadType.
Defines how the device handles RTCP packets during call sessions
for the SIP entity associated with the IP Profile. This is useful for
interworking RTCP between SIP entities. For example, this may be
necessary when incoming RTCP is not compatible with the
destination SIP entity's (this IP Profile) RTCP support. In such a
scenario, the device can generate the RTCP and send it to the SIP
entity.

[0] Transparent = (Default) RTCP is forwarded as is (unless
transcoding is done, in which case, the device generates RTCP
on both legs).

[1] Generate Always = Generates RTCP packets during active
and inactive (e.g., during call hold) RTP periods (i.e., media is
'a=recvonly' or 'a=inactive' in the INVITE SDP).

[2] Generate only if RTP Active = Generates RTCP packets only
during active RTP periods. In other words, the device does not
generate RTCP when there is no RTP traffic (such as when a
call is on hold).
426
Mediant 800B Gateway and E- SBC
Description
Document #: LTRT-10296