What is ESM (EPS Session Management)?

The EPS Session Management entity is a control plane function which upholds all parts of signalling for Packet Data Network session management. The EPS Session Management (ESM) protocol gives methodology for the management of EPS bearer contexts. Along with the bearer control given by the Access Stratum, it gives the control of user plane bearers. The transmission of ESM messages is suspended during EPS Mobility Management methods aside from the attach procedure.