SFU relay lab
Move the publisher, subscriber, network, and forwarding controls. Watch one upload become many selected downloads — and see exactly where the server's network bill comes from.
Lesson 12 — TopologiesBuild the forwarding policy
The publisher uploads once. Every choice below changes what the server sends back out.
Publishers
Each publishes one camera + audio set.
Subscribers
Viewers download; they do not publish.
The relay, right now
Subscriber network
Forwarding policy
Layer controls
Simulcast
High + mid + low from the publisher
Screen share
Adds a separate 1.5 Mbps track
HIGH 1.50 · MID 0.60 · LOW 0.15 MBPS
7.0 Mbps
Server egress
3.2 GB/h at this shape
878 kbps
Per-viewer downlink
Mixed cap 4 Mbps
2.3 Mbps
Publisher uplink
all three layers
16
Streams forwarded
0 transcodes; SFU
Egress against “send everything high”
72% saved
Adaptive forwarding is the SFU's main economic advantage: one publisher upload, many selected downloads.
The trade
Mesh comparison assumes every viewer also publishes high-quality camera video. Viewers in this SFU room only subscribe.
Fault injection
Break one layer at a time. The forwarding policy is what turns a failure into a graceful downgrade.
No fault is injected. The relay is forwarding every selected layer it can.
Optional · real SFU
LiveKitCompletion
Record the SFU lab
You have explored forwarding policy, simulcast layers, and failure modes. Record the lab to count it toward the certificate.