Quick Start: How to Choose Media Mode
- To use DSP resources, (due to transcoding, Lync interoperability, etc.) select DSP mode.
- For SIP-to-SIP calls using Proxy, select Proxy mode.
- To use the same call routes where the inbound call route could be both TDM/SIP, select Proxy preferred over DSP.
- To use DSP resources, rather than proxy or switch media stream between endpoints, use DSP preferred over Proxy.
Media Mode enables you to choose how the SBC handles call signaling and Audio/Fax media stream during a call. Five options are available:
DSP (default entry). The SBC uses DSP resources for media handling (transcoding) but it does not facilitate the capabilities/features between endpoints that are not supported within the SBC (codec/capability mismatch). When DSP is configured, the Signaling Groups enabled to support DSP are attempted in order. To enable a Signaling Group for DSP mode, see Creating and Modifying SIP Signaling Groups.
Proxy. The SBC will proxy or switch the media stream between endpoints and let the endpoints negotiate common media capabilities and handle unsupported/unknown audio codecs. The media flows through the SBC without using DSP resources. For example, this mode is used when both inbound and outbound calls are SIP and both Signaling Groups are enabled for Proxy mode. If one Signaling Group has Proxy mode disabled or one of the inbound Signaling Groups is TDM, the call is rejected. Route configuration does not allow Destination Signaling Groups of TDM type if Stream Mode is set to Proxy. The failover mechanism can then be used to re-route to another Signaling Group. We strongly recommend using Proxy preferred over DSP mode since it allows the same routing entry with different Signaling Groups.
The SBC prefers to use DSP resources, rather than proxy or switch the media stream between endpoints. This mode is chosen during the call setup based on the call routing, and used for call routes where the inbound call route is both TDM and/or SIP (this avoids duplicate call routes). If the inbound Signaling Group is a SIP Signaling Group not enabled for DSP, then Proxy is used. NOTE: If RTP encryption/decryption is expected, it is necessary to set the Proxy SRTP Handling field to 'Local', so that encryption/decryption is supported when switching to proxy.
Proxy preferred over DSP. The SBC prefers to proxy the media stream between endpoints rather than choosing DSP mode (which uses the DSP resource). This mode is chosen during the call setup based on the call routing result, and used for call routes where the inbound call route is both TDM and/or SIP (this avoids duplicate call routes). If the inbound or outbound Signaling Group is NOT in Proxy mode (either SIP signaling group is not enabled for Proxy mode or Signaling Group is TDM), then DSP is used.
Direct: The SBC media flows directly between compatible end-points without using either the SBC processor or a DSP resource.
Disabled. The Audio/Fax media selection process is disabled. When Disabled is selected, the SBC will reject incoming Audio/Fax streams.