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The Distributed SBC (D-SBC) solution distributes the core SBC components signaling, media and transcoding into discrete functional elements that allows SWe instance to instantiate and scale independently in their own respective clusters. This is ideal for greenfield deployments where all the three clusters are deployed; however, in an existing network, D-SBC uses the services of an external transcoder for audio transcoding.

In the D-SBC architecture, the virtualized Signaling SBC (S-SBC) and Media SBC (M-SBC) instances supports signaling and media relay functionalities. Media Resource Function (MRF) supports any media inter-working requirement that includes transcoding/transrating. S-SBC invokes the MRF using a 3PCC call model.

Media Resource Function – Resource Manager (MRF-RM) runs on SBC and interacts with external third-party transcoder (MRF Server) to provide transcoding services. S-SBC manages the transcoding resources on MRF server remotely using SIP interface. Any third-party transcoder that supports SIP interface is used as MRF server within the SBC to provide Audio transcoding services.


The SBC sends only a commit INVITE to the MRF server, and does not send any reserve INVITE to the MRF. This is applicable only for D-SBC on the OpenStack.

Key Features

  • Supports all audio features
  • Supports mid-call modification to insert or remove the transcoder
  • MRF related information is logged in CDR:
    • Signaling IP/Port information

    • Local/Remote End Point information for both Ingress and Egress private leg towards MRF

  • PSX Packet Service Profile (PSP) control is used to invoke transcoding

For more information on CLI changes, refer to D-SBC Cluster - CLI.

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