Thursday, December 2, 2021

CUPS-Userplane Selection


In CUPS Architecture, Control Plane(SGW-C,PGW-C,SGWPGW-C) selects Userplane (SGW-U,PGW-U,SGWPGW-U) to serve the subscriber request during PDN session establishment.


 There are multiple ways CP selects UP for a particular request.      

    Based upon APN received in the Create Session request. (APN-level)

       Based upon the TAC received in Create Session request. (User-location)

    Based upon the Load information of a particular UP-capacity among multiple UP to be selected.

    Round-Robin. (Least-loaded)


Based upon the operator configuration among above mentioned options, UP selection is to be performed by CP.

APN-Level: Same UE can be served by different Userplanes when UP selection is configured based upon APN level configuration.

            Eg:    internet àUP1

    IMS àUP2


User-location: UE’s can be served by a particular UP based upon their location.


UP-Capacity: Based upon the Load Control Information (LCI), Overload control information (OCI) received from UP to CP. CP takes the selection decision based upon these values. These values gets updated from UP to CP in SX Response messages.

Round-Robin: When no specific matched condition is configured for UP selection then by default round-robin technique is used to distribute the load among all the connected UPs.