Difference btw Data session & Data connection

Can someone tell me the difference between a Data session from Modem Data Control service API and a Data Connection from Data Connection service?

From the description of Modem Data Control: http://legato.io/legato-docs/latest/c_mdc.html and Data Connection: http://legato.io/legato-docs/latest/c_le_data.html, Data session from Modem Data Control service API can only be used to control Modem/Cellular data connection, but Data Connection from Data Connection service can also control WiFi, Ethernet WAN connection.