A Selective Forwarding Unit (SFU) is a service for optimising the number of streams being uploaded by users by forwarding media via 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 and network.
A Multipoint Control Unit (MCU) can act in the same capacity as an SFU while introducing the concept of media processing which involves our recording and archiving functionality. It is especially useful in applications where video transcoding is required.
The combined SFU/MCU component is what we refer to as the Skylink Media Relay (SMR).
Other articles you may be interested in:
Where are Temasys MCU/SFU servers located?
How can I enable/ disable Skylink Media Relay for my App?
How is MCU/SFU Bandwidth measured and billed?
Six Things You Need To Know About WebRTC SFUs.