why does EZMODE start need to enable Permitjoin while they are on network？

Other Parts Discussed in Thread: Z-STACK

Hi all

       when  two  device begin trigger EZMODE  （all of  them are  on network），why does they need  to be enabled permit join ?

       and  when EZMODE finish, they disable the permit join .

  // if already on network, just go to identify state
  if ( zclEZModeInvokeData.onNetwork )
  {
    zcl_SetEZModeState( EZMODE_STATE_OPENER );
  }

    // openers will broadcast permit joining
    case EZMODE_STATE_OPENER:
      zclEZModeOpener = 1;

      // enable joining both locally and over-the-air
      zcl_EZModePermitJoiningRequest( *zclEZModeRegisterData.pTaskID, &dstAddr,
                                     (byte)(EZMODE_TIME / 1000) );

      // then go to identifying state
      zcl_SetEZModeState(EZMODE_STATE_IDENTIFYING);
    break;

BR!