SFU (Selective Forwarding Unit)

SFU (Selective Forwarding Unit) is a video conferencing architecture which features the following data transmission processes between the server and the endpoints:

• The server receives incoming video streams from all endpoints.
• The server sends several copies of uncompressed video streams of other participants to each endpoint.
• The endpoints merge incoming video streams.

Thanks to this, the client does not need to send the same outgoing signal to each participant. Instead, the stream is sent to the server and distributed among all users. As a result, the client sends a single outgoing signal and receives streams from other users via the server.

SFU Architecture Advantages

• Since there is only one outgoing stream, the client does not require a high-bandwidth upstream connection.
• Incoming connections are not established directly with each participant, but rather with the media server.
• The SFU architecture is less demanding on server resources compared to other video conferencing architectures. It also allows for seamless monitoring, regardless of whether a dedicated network monitoring tool is used.

SFU Architecture Disadvantages

• The server sends video in excessively high quality to the layout, resulting in each participant receiving a video stream larger than necessary.
• Since the server cannot adjust the outgoing stream, it creates a weak link issue: if one participant fails to connect, the video quality for all others may degrade — potentially leading to a temporary video stream shutdown.
• The server requires more bandwidth compared to other video conferencing systems, as it must handle all copies of the video streams it generates.
• The client must decode multiple incoming media streams, which demands a more powerful CPU and a higher-bandwidth downstream connection than other architectures.
• By default, SFU does not support server-side recording: it merely proxies media data.
• Connecting to SIP/H.323 devices is not possible without gateway configuration.
• Since multiple media streams are not mixed into a single stream, live streaming is not supported.