终端attach请求消息中Classmark 3信息介绍

终端在发起EMM或者MM attach request时，是否携带classmark 3消息，依赖终端的能力。

如果终端支持VoLTE以及4G和2G能力，则会携带classmark3 IE，3GPP Spec24.008中定义classmark 3为：

9.4.1.7 Mobile station classmark 3

This IE shall be included if the MS supports SRVCC to GERAN.

LTE attach，带有 classmark 3信息，Log参考

MSG_ID_EMMREG_SET_RAT_MODE_REQ //rat_mode=ERAT_LTE_UMTSFDD_GSM

[MS->NW]EMM_Attach_Request(EPS attach type=“EMM_ATTACH_TYPE_COMBINED_ATTACH”)

//1 = SRVCC to GERAN/UTRAN capability , Mobile station classmark 3