add more doc

interface.go

@@ -216,10 +216,15 @@ type EarlyConnection interface {
 type ConnectionIDGenerator interface {
 
 	// GenerateConnectionID generates a new ConnectionID.
+	// Generated ConnectionIDs should be unique and observers should not be able to correlate two ConnectionIDs.
 	GenerateConnectionID() ([]byte, error)
 
 	// ConnectionIDLen tells what is the length of the ConnectionIDs generated by the implementation of
 	// this interface.
+	// Valid lengths are between 0 and 20 and calls to GenerateConnectionID should always generate ConnectionIDs of
+	// that length, even if zero sized.
+	// 0-length ConnectionsIDs can be used when an endpoint (server or client) does not require multiplexing connections
+	// in the presence of a connection migration environment.
 	ConnectionIDLen() int
 }