What is an MSISDN?
On a cellular network, MSISDN (Mobile Station Integrated Services Digital Network) is the phone number that shows up when one device makes contact with another. It performs a crucial function in ensuring secure, efficient connectivity between the different components within an IoT network.
What is an MSISDN?
When you make a call on your mobile, there needs to be an effective way of connecting you to the right recipient, and that recipient needs a way of identifying you. The same applies to one device linking up with another on an IoT network.
This is where an MSISDN is crucial. It is the unique number that identifies a subscriber on a network.
The exact length of an MSISDN varies from country to country, depending on the numbering procedures set by local regulatory bodies. Typically however, it is 14 or 15 digits long (15 is the maximum). It is made up of three elements:
- Country Code (CC)
- National Destination Code (NDC)
- Subscriber Number (SN): This is the part that is unique to each subscriber.
What is the difference between an MSISDN and an IMSI?
The main difference between an MSISDN and an IMSI is:
- The MSISDN is the full “phone number” for a device.
- The IMSI is basically a technical identifier, used by the network operator.
Both of these numbers are types of identifiers; each performing a distinct role.
The international mobile subscriber identity (IMSI) is a 15-digit number that enables the network operator to identify subscribers. It is stored on the SIM (subscriber identity module). If a SIM is moved from a device, the IMSI moves with it. You cannot dial up an IMSI. These numbers are used mostly by operators for network management purposes: e.g. for checking the location of users.
MSISDNs are much more focused on facilitating connections between users and devices. Unlike an IMSI, MSISDNs are not bound to a particular SIM. They can be transferred from device to device and SIM to SIM. You can even have multiple MSISDNs associated with the same SIM or device.
Benefits of MSISDN
In any system of interacting devices, you need a means of differentiating between different users. Those users need a way of making themselves known, and of identifying each other. MSISDN is an effective, globally-recognised way of achieving this.
The transferability of MSISDNs is another advantage of the system. Let’s say you have several employees that will all need to use the same connected device from time to time. You can potentially assign multiple numbers to the same device to match different employee profiles.
Disadvantages of MSISDN
From a security perspective, the transferability of MSISDNs can pose a risk. Say, for instance, a threat actor gains knowledge of an MSISDN associated with a particular user on a network. They contact the operator, perhaps saying that the SIM or device is lost or damaged, and are issued with a new one. Before you notice, the threat actor is able to access your data. SIM fraud is one of the reasons why you need measures in place to authenticate users quickly, securely and reliably.
Device and user management is another potential challenge. For instance, if you are using a manual spreadsheet to keep track of the numbers associated with various users and devices, it’s a big task to ensure the information is up-to-date. If it’s managed through a dedicated IoT portal, all of this should be managed automatically.