AudioCodes Mediant 800 User Manual page 470

CHAPTER 19 Coders and Profiles
Parameter
'RTP Redundancy Mode'
sbc-rtp-red-behav
[IpProfile_
SBCRTPRedundancyBehavior]
Mediant 800 Gateway & E-SBC | User's Manual
Description
Note: The parameter requires DSP resources.
Enables interworking RTP redundancy negotiation support
between SIP entities in the SDP offer-answer exchange
(according to RFC 2198). The parameter defines the
device's handling of RTP redundancy for the SIP entity
associated with the IP Profile. 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 offered, it will support it in the
outgoing SDP answer. 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.
Note:
■ 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.
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