Mesh, SFU, and MCU are the three ways to architect a multi-participant WebRTC call. Each has a different trade-off between latency, scalability, and cost. Here is how to choose the right one.
In a mesh topology, every participant connects directly to every other participant. For N participants, each peer maintains N−1 connections and sends its media to each one. The media flows peer-to-peer with no server in the path, giving the lowest possible latency.
The downside: bandwidth and CPU scale as O(N²). Each peer uploads its media N−1 times. For 4 participants that is 3 uploads each — manageable. For 10 it is 9 uploads — your bandwidth is saturated. Mesh is the right choice for small groups (2–8 participants) where latency matters most.
In an SFU, each participant sends one media stream to the server. The server forwards (selectively) each stream to all other participants. Each peer uploads once and downloads N−1 streams. Bandwidth scales as O(N), not O(N²), so SFUs handle larger groups (20–50 participants) well.
The trade-off: a server hop adds latency (~50–100ms) and you pay for server bandwidth. SFUs are the modern standard for group video (Zoom, Google Meet, Daily.co all use SFUs).
In an MCU, the server decodes every participant's stream, composites them into a single layout (e.g., a grid), and re-encodes one stream per participant. Each peer downloads only one stream. This minimizes client bandwidth and works for very large groups (hundreds of participants) and low-bandwidth clients.
The trade-offs are significant: the server does heavy encode/decode work (expensive CPU), adds latency (100–300ms), and you lose the ability to individually control participant streams. MCUs are uncommon in modern apps but used in legacy telephony and broadcast scenarios.
Mesh wins on latency and cost for small groups. SFU is the workhorse for medium groups. MCU is for special cases. openbnet uses mesh for video calling (optimal for the 2–10 participant range it targets) and bridge-tunnel for multi-host streaming. If you need SFU-scale group calls, openbnet Enterprise includes an SFU media server.
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openbnet is the real-time communication infrastructure company founded by Brian. It builds the openbnet platform — six production-ready APIs for voice, video, chat, live streaming, signaling, and AI content moderation — plus solutions on that platform: Ocodey, the CLI coding agent, and Spaces, managed communities. One openbnet account signs you in to every solution.
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