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Overview

The Distributed SBC (D-SBC) solution distributes the core SBC components (signaling, media and transcoding) into discrete functional elements that allow the SWe instance to instantiate and scale the components independently in their own respective clusters. This is ideal for greenfield (initial) 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 support signaling and media relay functionalities. The Media Resource Function (MRF) supports any media inter-working requirement that includes transcoding and transrating1. The S-SBC invokes the MRF using a 3PCC call model.

Media Resource Function – Resource Manager (MRF-RM) runs on the SBC and interacts with external third-party transcoder (MRF Server) to provide transcoding services. The 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.

Note

For the D-SBC on OpenStack, the SBC only sends a COMMIT INVITE to the MRF server – it does not send a RESERVE INVITE to the MRF (Reactive mode, enabled by default). 

  • COMMIT – If a call requires transcoding, the SBC commits resources to the MRF.
  • RESERVE – The SBC reserves resources for transcoding in case they are deemed needed (Proactive model, not currently used).

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.

1  The process by which video and audio files are converted to a reduced bit rate while still maintaining the original media format.

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