5G NSA : selection of SGW/PGW for NSA

UE core network capability signalling allows the MME (via its DNS) to select the SGW and PGWs that are appropriate for the UE’s high data rate. Additional signalling allows the SGW-C and PGW-C to take the UE’s NR capability into account when selecting the SGW-U and PGW-U.

Refer - 29.303: 3GPP 29.303 Release 15.2.0 - Domain Name System Procedures. Dns proc 5.12.2 Procedures to support Dual Connectivity with NR

MME should select SGW/PGW slice which is meant for dual connectivity. Also SGW/PGW can select correct SGW-U/PGW-U which is capable of handling higher data rates.