Expand ConnectionStart doc.
@@ -53,7 +53,13 @@ The function returns a [QUIC_STATUS](QUIC_STATUS.md). The app may use `QUIC_FAIL
# Remarks
-**TODO**
+`ConnectionStart` initiates the connection from the client application. A server application doesn't start its side of the connection until it returns `QUIC_STATUS_SUCCESS` from the `QUIC_LISTENER_EVENT_NEW_CONNECTION` event.
+
+No packets are sent until `ConnectionStart` is called, which starts the handshake, generates the initial cryptographic keys, frames 0-RTT data if present, and then sends the initial flight of packets to the server.
+
+Since 0-RTT data is opportunistically sent during the connection handshake, it should be queued for send **BEFORE** calling `ConnectionStart` otherwise it may be sent after the handshake. Queueing 0-RTT data after calling `ConnectionStart` will race with the creation of the inital flight of packets and may not consistently be sent as 0-RTT data.
+
+Some settings on the `Configuration`, and on the `Connection`, only take effect if set before `ConnectionStart` is called. See [ConfigurationOpen](ConfigurationOpen.md) and [SetParam](SetParam.md) for more details about settings.
# See Also
