Feature Description

The SMF supports the UE performing initial attach on E-UTRAN via MME and S-GW to create the default bearer.

Initial attach on E-UTRAN or EPS follows the procedure defined in 3GPP specification 23.401, Section 5.3.2.1. There are few deviations from the defined procedure to enable connectivity through the 5G core. The deviations are as follows:

  • The Packet Data Network Gateway (P-GW) in the procedure is replaced by SMF+PGW.

  • The IP-CAN Session establishment and modification is replaced by SM Policy Association Establishment procedure.

  • The online and offline charging functionality using Gy and Gz interfaces is replaced by integrated charging over Nchf interface with Charging Function (CHF).

  • The interface with the user-plane node is through N4 interface instead of Sxb interface.