What is MSISDN?

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Sushanth P S

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June 20, 2024

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Key Takeaways

  • MSISDN, or Mobile Station International Subscriber Directory Number, uniquely identifies mobile subscribers globally, essential for calls and texts.
  • It follows the ITU-T E.164 standard, comprising a country code, national destination code, and subscriber number, often prefixed by "+" for international dialling.
  • MSISDN ensures unique global identification, supports security processes like two-factor authentication, and facilitates accurate routing and billing.
  • Widely used in telecommunications, banking, e-commerce, healthcare, and emergency services for secure communication and transaction notifications.
  • Challenges include privacy concerns, fraud risks, number portability, and regulatory compliance, but its role is expanding with technologies like IoT and 5G.

According to GSMA’s recent Mobile Economy Report of 2024, the number of unique mobile subscribers in the world is around ‘5.6 Billion’, this number is nothing but the total number of MSISDN issued to users globally.  

What is MSISDN?

MSISDN stands for Mobile Station International Subscriber Directory Number. It is a unique identifier used in mobile networks to identify a subscriber. Essentially, the MSISDN is the phone number that people use to call or text a mobile phone. It is the number that is dialled to reach a specific mobile device and is integral to the functioning of mobile networks worldwide.  

What is an MSISDN Number?

The term "MSISDN number" might seem redundant since MSISDN itself implies a number, but it is often used to emphasize the numeric aspect of the identifier. The MSISDN number is globally unique and follows international numbering standards to ensure that each subscriber can be distinctly identified on a global scale.

How Does MSISDN Work?

The MSISDN is embedded in the Subscriber Identity Module (SIM) card of a mobile device. When a call is made or a message is sent, the mobile network uses the MSISDN to route the communication to the correct recipient. The MSISDN is associated with the International Mobile Subscriber Identity (IMSI) and other network identifiers to facilitate accurate and efficient communication within and between networks.  

Difference Between MSISDN and IMSI:

While MSISDN and IMSI (International Mobile Subscriber Identity) are both essential for mobile communications, they serve different purposes:

MSISDN: This is the public number assigned to a subscriber. It is the number you share with others to make calls or send SMS. It is used for routing communications and is visible to users.

IMSI: This is a unique identifier assigned to a subscriber by the mobile network operator. It is stored on the SIM card and is used primarily for identifying and authenticating subscribers within the network. The IMSI is not typically visible to users.

In summary, the MSISDN is the number you dial, while the IMSI is the number the network uses to identify and authenticate your subscription.

Structure of an MSISDN:

The structure of an MSISDN is defined by the ITU-T E.164 standard, which ensures consistency across different countries and networks. An MSISDN typically includes the following components:

  1. Country Code (CC): This is a one to three-digit code that identifies the country. For example, the country code for the United States is 1, for the United Kingdom it is 44, and for India it is 91.
  2. National Destination Code (NDC): This code identifies a specific geographic area, mobile network, or service provider within the country. It varies in length depending on the numbering plan of the country.
  3. Subscriber Number (SN): This is the unique number assigned to the subscriber within the NDC. It varies in length and completes the MSISDN.

For example, in the MSISDN +44 7911 123456, "+44" is the country code for the UK, "7911" is the NDC, and "123456" is the subscriber number.

What Does the “+” Stand for in MSISDN?

The "+" sign in an MSISDN signifies that the number is formatted in the international dialling format. It indicates that the number should be dialled with the international access code, which varies by country. For instance, when dialling an international number from the United States, the "+" is replaced by "011".  

Benefits and Importance of MSISDN Number

The MSISDN plays a critical role in mobile communications for several reasons:

  1. Global Uniqueness: The MSISDN ensures that each mobile subscriber can be uniquely identified and reached anywhere in the world.
  2. Security and Verification: MSISDN is used in various security and verification processes, such as two-factor authentication (2FA), where a verification code or OTP is sent to the user's mobile number. Our team at Message Central can help you setup OTP verification service.
  3. Routing and Billing: It is essential for routing calls and messages correctly and for billing purposes. Operators use MSISDN to track usage and generate bills.
  4. Interoperability: The standardized structure of MSISDN facilitates interoperability between different mobile networks and countries.

Applications of MSISDN in Various Fields

MSISDN numbers have wide-ranging applications across different sectors:

  1. Telecommunications: MSISDN is fundamental to the functioning of mobile networks, enabling voice calls, text messaging, and data services.
  2. Banking and Finance: Banks use MSISDN for secure communication with customers, sending alerts, and conducting mobile banking transactions.
  3. E-commerce: Online platforms use MSISDN for user verification by sending OTPs, order confirmations, and transaction notifications through SMS.
  4. Healthcare: Healthcare providers use MSISDN to communicate appointment reminders and health information to patients.
  5. Emergency Services: MSISDN is used to quickly identify and communicate with individuals in emergency situations.

Challenges and Considerations

Despite its importance, the use of MSISDN comes with certain challenges and considerations

  1. Privacy Concerns: As MSISDN is a public identifier, it can be used to track and target individuals. Ensuring the privacy and security of MSISDN data is crucial.
  2. Fraud and Misuse: MSISDN can be exploited for fraudulent activities, such as SIM swapping and phishing attacks. Robust security measures are needed to prevent such misuse.
  3. Number Portability: The ability to port numbers between different operators can complicate the management of MSISDN and require additional infrastructure.
  4. Regulatory Compliance: Different countries have varying regulations regarding the use and storage of MSISDN data, which can complicate international operations.  

Other Important Facts about MSISDN

  • History: The concept of MSISDN was developed to provide a standardized way to identify mobile subscribers globally, facilitating the rapid growth of mobile communications.
  • Technological Evolution: With the evolution of mobile technology from 2G to 5G, the role of MSISDN has expanded to support more complex services and applications.
  • Future Prospects: As mobile networks continue to evolve, the importance of MSISDN is expected to grow, particularly in areas such as Internet of Things (IoT) and machine-to-machine (M2M) communications.

In conclusion, although MSISDN could appear to be a technical jargon word, it's actually the basis for our mobile phone connectivity. We can communicate with our loved ones, make calls to friends, and move around our digital life thanks to this invisible thread. Knowing MSISDN is about knowing the infrastructure that ties us all together, not just the technology. MSISDN is expected to continue playing a significant role as technology develops, expanding and changing to accommodate new phone using habits.

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