docs: data transfer state

docs/protocol.tex

@@ -559,4 +559,10 @@ command state commands that don't require transfer of Assets/Profile data are
 available to command to the worker/master server. These commands include but
 not limited to: login, register, purchase asset, sell asset.
 
+\subsubsection{Data Transfer State}
+The data transfer state is switchable from the command state. Switching back to
+command state is done at the end of the data transfer. The data transfer
+commands include but are not limited to: get asset value, get past asset value,
+get predicted future asset value.
+
 \end{document}