10.2.7 QoS Packet Marking (differentiated services)
29.1623GPPInterworking between the IM CN subsystem and IP networksRelease 17TS
The procedures in subclause A.7.1.2.2.4 of 3GPP TS 29.235 [29] are applicable.
Those procedures relate to Diffserv code point marking as described in IETF RFC 2474 [31]