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Collaboration, Voice & AV · Advanced

Selective Forwarding Unit (SFU)

A media server that receives streams from participants and forwards selected streams to others without decoding or mixing them.

Definition

An SFU relies on endpoints sending simulcast or scalable video so it can choose the appropriate layer for each receiver. Because it does not transcode, it scales efficiently and adds little latency, but endpoints must decode multiple streams and compose layouts themselves. WebRTC services, Webex and Teams use SFU-style architectures.

Example

A Webex media node forwards the active speaker's 720p layer and thumbnails' 180p layers to each client.

Exam tip

SFU shifts work to endpoints and requires simulcast or SVC; MCU centralizes work.

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