Two Planes, Two Jobs
A mesh separates what moves traffic from what decides how. The data plane is the set of proxies that actually forward bytes. The control plane is the management layer that programs those proxies.
Data Plane Responsibilities
- Forwarding requests and balancing load.
- Applying retries, timeouts, and circuit breakers.
- Terminating and originating encryption.
- Emitting metrics and traces.
The data plane is on the hot path, so it must be fast and stay running even if the control plane is down.
Control Plane Responsibilities
- Distributing configuration to every proxy.
- Managing service discovery and endpoints.
- Issuing certificates for identity.
- Enforcing policy from a central source of truth.
Why the Split Matters
Because the data plane caches its last known config, a control plane outage degrades gracefully. Existing traffic keeps flowing using the rules already pushed. New routing changes simply pause until the control plane recovers. This separation is what lets a mesh survive partial failure.
Key idea
The data plane forwards traffic on the hot path while the control plane configures it from the side, so a control plane outage degrades gracefully rather than dropping requests.