Introduction ============ The Envoy xDS APIs are defined as `proto3 `_ `Protocol Buffers `_ in the :repo:`api tree `. They support: * Streaming delivery of :ref:`xDS ` API updates via gRPC. This reduces resource requirements and can lower the update latency. * A new REST-JSON API in which the JSON/YAML formats are derived mechanically via the `proto3 canonical JSON mapping `_. * Delivery of updates via the filesystem, REST-JSON or gRPC endpoints. * Advanced load balancing through an extended endpoint assignment API and load and resource utilization reporting to management servers. * :ref:`Stronger consistency and ordering properties ` when needed. The APIs still maintain a baseline eventual consistency model. See the :ref:`xDS protocol description ` for further details on aspects of xDS message exchange between Envoy and the management server.