[多选题]ZXUN CSCF网元升级过程包括哪些步骤?( )
The upgrade process of the ZXUN CSCF includes the following steps: ( ). A.升级准备
Upgrade preparation B.网管升级
OMM upgrade C.前台升级
Foreground upgrade D.升级后验证观察
Verification and observation after upgrade E.应急恢复
Emergency recovery