23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS
The following text describes the general principles used by an SGSN using S4 when mapping between PDP Contexts and EPS Bearers.
The MS is using PDP Context Activation, Modification and Deactivation functions, and PDP Contexts are therefore used between MS and SGSN. An SGSN using Gn/Gp only will use these procedures towards GGSNs as well. An SGSN using S4 will for a specific PDP Context towards an MS map these procedures into equivalent procedures using EPS Bearer towards S‑GW and P‑GW. EPS Bearer procedures will not be used between MS and SGSN.
The following principles are to be used:
– 1:1 mapping between one PDP context and one EPS Bearer;
– 1:1 mapping between NSAPI and EPS Bearer ID;
– The P‑GW treats an MS-initiated request, e.g. a Secondary PDP Context Activation Request, according to the UE requested bearer resource modification procedures in TS 23.401 ;
– PDN GW and Serving GW need to be RAT aware to allow for 2G/3G specific handling of EPS bearers, e.g. MS initiated secondary PDP Context activation must make the P‑GW to activate a new EPS bearer.
– The QoS profiles of the PDP context and EPS bearer are mapped as specified in TS 23.401 .
– If the S4-SGSN receives the EPS subscribed QoS profile per subscribed APN from the HSS, the S4-SGSN enforces this QoS for the first PDP context which is activated to the given APN. Otherwise the S4-SGSN restricts requested QoS according to the QoS Profile Subscribed which defines the maximum QoS per subscribed APN.