AudioCodes Mediant 4000 SBC User Manual page 445

CHAPTER 19 Coders and Profiles
Parameter
'RTCP Mux'
sbc-rtcp-mux
[IPProfile_SBCRTCPMux]
Description
■ [0] Don't Care = (Default) The device forwards the
SDP as is without interfering in the RTCP attribute
(regardless if present or not).
■ [1] Add = The device adds the 'a=rtcp' attribute to the
outgoing SDP offer sent to the SIP entity if the attribute
was not present in the original incoming SDP offer.
■ [2] Remove = The device removes the 'a=rtcp'
attribute, if present in the incoming SDP offer received
from the other SIP entity, before sending the outgoing
SDP offer to the SIP entity.
Note: As the RTCP attribute has been defined by the
WebRTC standard as mandatory, the support is important
for deployments implementing WebRTC. For more
information on WebRTC, see WebRTC.
Enables interworking of multiplexing of RTP and RTCP
onto a single local port, between SIP entities. The
parameter enables multiplexing of RTP and RTCP traffic
onto a single local port, for the SIP entity associated with
the IP Profile.
Multiplexing of RTP data packets and RTCP packets onto
a single local UDP port is done for each RTP session
(according to RFC 5761). If multiplexing is not enabled, the
device uses different (but adjacent) ports for RTP and
RTCP packets.
With the increased use of NAT and firewalls, maintaining
multiple NAT bindings can be costly and also complicate
firewall administration since multiple ports must be opened
to allow RTP traffic. To reduce these costs and session
setup times, support for multiplexing RTP data packets
and RTCP packets onto a single port is advantageous.
For multiplexing, the initial SDP offer must include the
"a=rtcp-mux" attribute to request multiplexing of RTP and
RTCP onto a single port. If the SDP answer wishes to
multiplex RTP and RTCP, it must also include the "a=rtcp-
mux" attribute. If the answer does not include the attribute,
the offerer must not multiplex RTP and RTCP packets. If
both ICE and multiplexed RTP-RTCP are used, the initial
SDP offer must also include the "a=candidate:" attribute for
both RTP and RTCP along with the "a=rtcp:" attribute,
indicating a fallback port for RTCP in case the answerer
does not support RTP and RTCP multiplexing.
■ [0] Not Supported = (Default) RTP and RTCP packets
use different ports.
■ [1] Supported = Device multiplexes RTP and RTCP
packets onto a single port.
Note: As RTP multiplexing has been defined by the
WebRTC standard as mandatory, the support is important
for deployments implementing WebRTC. For more
information on WebRTC, see WebRTC.
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Mediant 4000 SBC | User's Manual