1. Config ingestion (inputs to the system)
1. Config translation
1. Config serving (XDS)

### Config Ingestion

Istio reads from over 20 different resources types, and aggregates them together to build the proxy configuration. These resources can be sourced from Kubernetes (via watches), files, or over xDS; Kubernetes is by far the most common usage, though.

Primarily for historical reasons, ingestion is split into a few components.