5.6 PFCP Session Handling

29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS

5.6.1 General

The following clauses provide details on PFCP Sessions handling.

5.6.2 Session Endpoint Identifier Handling

The SEID uniquely identifies a PFCP session at an IP address of a PFCP entity. The F-SEID is the Fully Qualified SEID and it contains the SEID and IP address. The PFCP endpoint locally assigns the SEID value the peer PFCP side has to use when transmitting message. The SEID values are exchanged between PFCP endpoints using PFCP messages. The PFCP entity communicates to the peer PFCP entity the SEID value at which it expects to receive all subsequent control plane messages related to that PFCP session via the "F-SEID" IE.

The PFCP session related messages shall share the same F-SEID for the PFCP session. An F-SEID shall be released after the PFCP session is released.

5.6.3 Modifying the Rules of an Existing PFCP Session

The following principles shall apply, unless specified otherwise in the specification.

When modifying an existing PFCP session, the CP function shall only provide in the PFCP Request message the requested changes compared to what was previously provisioned in the UP function for this PFCP session, i.e. the CP function shall:

– include IEs which needs to be newly provisioned in the UP function;

– include IEs which need to be provisioned with a modified value;

– remove IEs which need to be removed from the set of parameters previously provisioned in the UP function, as further specified below.

The CP function shall remove IEs which needs to be removed by either:

– removing the entire Rule if no other parameter of that rule needs to remain provisioned in the UP function, e.g. by including the Remove URR IE in the PFCP Session Modification Request; or

– updating the Rule including the IEs to be removed with a null length, e.g. by including the Update URR IE in the PFCP Session Modification Request with the IE(s) to be removed with a null length. For an IE with multiple occurrences, e.g. when the description of the IE contains the text "several IEs with the same IE type may be present", one occurrence of such an IE with a null length shall result in removing all the IEs with the same IE type.

The CP function shall set a URR ID and/or QER ID with a length "0" in the Update PDR IE within PFCP Session Modification Request, to request the UP function to stop applying the URRs and/or QERs for this PDR.

Upon receipt of a PFCP Request which modifies an existing PFCP session, the UP function shall add, update or remove the parameters as instructed by the CP function, as defined above, and shall keep unchanged the set of parameters previously provisioned in the UP function which are neither modified nor removed.