A Selective Forwarding Unit (SFU) is a service for optimising the number of streams sent in a room by forwarding media to a central server, essentially replicating and redistributing inbound streams without modifying them to remote Peers. This decreases bandwidth required for multi-party calls and the amount of load on client software.
A Multipoint Control Unit (MCU) has the capacity to act as an SFU while introducing the concept of media processing which involves our recording and archiving functionality and is especially useful in a video conferencing application.
The combined SFU/MCU component is what we refer to as the Skylink Media Relay (SMR).
For more information about how SFUs work, see our Blog Post! Six Things You Need To Know About WebRTC SFUs.