What is the difference between imsi and msisdn?

Answer 1

IMSI - International Mobile Subscriber Identity MSISDN - Mobile Directory Number Both are two different numbers. One is used to identify a subscriber by operator. Other is used to route the call. A subscriber becomes customer of an operator by buying the SIM card of the operator. At this point the subscriber is allocated an IMSI and an MSISDN. IMSI is used to identify a subscriber by the operator. But MSISDN is the number which is used for dialing. So when you call your friend/a mobile, you call the MSISDN number of the mobile, not the IMSI. For Eg: Consider 2 subscriber's A & B. And assume the values given below; IMSI (A) : 987123111111111 IMSI (B) : 987124111111111 MSISDN (A) : 9448012121 MSISDN (B) : 9448121212 So when A would like to call B, A dials the MSISDN number of B, i.e, 9448121212. And same is true for vice-versa. Now coming to need of IMSI, when a mobile is switched on, it needs to identify and authenticate the subscriber with the network. Only then the mobile will be able to use the network services. So to identify the user in this scenario, the IMSI of the subscriber is used. In fact the IMSI is burned in the SIM card, which will be used while authenticating with network. MSISDN will not be stored in the SIM. 220.227.79.138 10:18, 3 September 2007 (UTC) : A couple of important things were left out of that description. There are three identities IMEI, IMSI and MSISDN. The IMEI is the mobile phone's identity which is burned into the phone. The IMSI is the identity of the SIM card. And MSISDN is the phone number. You can change the phone number of the phone without changing its IMSI (the sim card). You can keep the same phone number (MSISDN), change phones (the IMEI) and just move the SIM card (IMSI). By separating the three identities, it makes it easy for subscribers to easily upgrade phones without having to change phone numbers or accounting information. Kgrr (talk) 23:57, 2 June 2008 (UTC)