AudioCodes Mediant 3000 User Manual page 414

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Calls between two SIP UA's in the same LAN and signals are sent to a SIP proxy
server (or hosted IP PBX) located in the WAN.
Figure 28-5: SBC SIP Signaling without RTP Media Flow
The benefits of implementing the No Media Anchoring include the following:

Saves network bandwidth

Reduces CPU usage (no RTP/SRTP handling)

Avoids interference in SDP negotiation and header manipulation on RTP/SRTP
The No Media Anchoring process is as follows:
1. Identifies a No Media Anchoring call - according to configuration and the call's
properties (such as source, destination, IP Group, and SRD).
2. Handles the identified No Media Anchoring call.
The No Media Anchoring feature is enabled using the SBCDirectMedia parameter. You can
also enable No Media Anchoring per SRD (using the IntraSRDMediaAnchoring parameter),
whereby calls between two UA's that pertain to the same SRD (source and destination) are
handled as No Media Anchoring (direct media) calls.
Notes:
User's Manual
•
No Media Anchoring can be used when the SBC does not do NAT
traversal (for media) where all the users are in the same domain.
•
No Media Anchoring calls cannot operate simultaneously with the
following SBC features:
- Force transcoding
- Extension Coders
- Extension of RFC 2833/Out-of-band DTMF/In-band DTMF
- Extension of SRTP/RTP
All restriction features (Allowed Coders, restrict SRTP/SRT, restrict RFC
2833) can operate simultaneously. Once No Media Anchoring is enabled,
the features listed above are disabled.
•
The Coder Restriction feature operates simultaneously with No Media
Anchoring calls. Restricted coders are removed from the SDP offer
message.
•
When two UA's pertain to the same SRD, the parameter
IntraSRDMediaAnchoring is set to 1, and one of the UA's is defined as a
foreign user (example, "follow me service") located in the WAN, while the
other UA is located in the LAN: calls between these two UA's can't be
established until IntraSRDMediaAnchoring is set to 0, as the device
doesn't interfere in the SIP signaling. In other words, parameters such as
IP addresses are not manipulated for calls between LAN and WAN
(although required).
•
When the parameter SBCDirectMedia is disabled, No Media Anchoring
calls between two UA's belonging to separate SRD's cannot be
configured. No Media Anchoring calls between two UA's belonging to the
same SRD is configurable only (in this case).
414
Mediant 3000
Document #: LTRT-89729