<authentication mode="Windows"/>
 <sessionState timeout="120">

IIS -> application pools -> select pool -> Advanced settings -> section "process model" => Idle Time-out(minutes)

<sessionState mode="InProc" timeout="5" />

<authentication mode="Forms">
  <forms loginUrl="~/" slidingExpiration="true" timeout="5" />
</authentication>

<authentication mode="Forms">
  <forms loginUrl="~/" slidingExpiration="true" timeout="120" />
</authentication>