sentences:  Its procedures refers to the steps a GSM network takes to communicate with cell phones and other mobile devices on the network.IMSI attach refers to the procedure used when a mobile device or mobile station joins a GSM network when it turns on and IMSI detach refers to the procedure used to leave or disconnect from a network when the device is turned off.In a GSM network, when a Mobile Station (MS) is switched ON, the International Mobile Subscriber Identity (IMSI) attach procedure is executed.