As mobile and wireless networks have evolved, the ability for users to move between different networks while maintaining service, known as roaming, has become essential. WiFi roaming, while convenient for users, introduces several complexities for service providers, particularly in managing billing and user identity securely across network boundaries.
The Chargeable User Identity (CUI) parameter was introduced to address these challenges. While the specification RFC 4372 for CUI has existed for quite awhile, the implementations are now popularising as commercial Wi-Fi is becoming more sought after.
Chargeable User Identity uses and benefits
Chargeable user identity is a parameter used mostly by service providers to identify users for accounting in roaming networks, while ensuring their privacy is not compromised with trackable credentials. The CUI allows service providers to charge users based on their usage, even when users roam across different networks. It is primarily intended for billing purposes, but also provides other benefits to both public and commercial networks.
The main benefit of using Chargeable User Identity parameter is that it solves the business problem of anonymity in commercial networks, while not making any compromises in privacy and security. It provides a robust mechanism for calculating usage, which can be used not only for billing but also analytics purposes. For example, with CUI, roaming network providers can track whether their 100 sessions come from 10 users with 10 sessions each or by 2 users with 50 sessions each. This allows for more accurate analytics, but does not allow the networks to identify the users. This is possible in deployments where the CUI is the same across all of the user’s devices.
The use of Chargeable User Identity also allows public institutions to restrict and ban roaming users who violate their terms. Previously, when administrators decided to take action against users who violate their visiting terms, the user can simply log on with another device. With a CUI parameter that is mutual across user’s all devices, this is not possible.
Chargeable User Identity deployment
Chargeable User Identity is transmitted in RADIUS packets using dedicated RADIUS attribute 89: Chargeable-User-Identity. The implementation is specified in RFC 4372.
Upon sending the authentication Access-Request to the home organisation for a roaming user’s authentication, the visiting organisation should add the Chargeable-User-Identity parameter into the request with a null value. This signals the home organisation that a CUI is requested. The home organisation check’s for an existing valid CUI and sends either a new or existing valid CUI included in the Access-Accept.
The Chargeable-User-Identity parameter will remain the same for the duration of the roaming user’s session and is included in the accounting packets and responses.
Want to know more?
Are you looking to deploy Wi-Fi offloading or other Wi-Fi roaming functionality for your customers or members of your organisation? Or are you setting up a commercial Wi-Fi infrastructure to provide roaming services for operators? For both cases, Radiator AAA is the product for you.
Radiator AAA provides functionality for Wi-Fi roaming host organisations, with dozens of completed deployments for the biggest Wi-Fi roaming networks (eduroam, govroam, OpenRoaming). Combined with the Radiator SIM Pack, Radiator provides seamless authentication for Wi-Fi offloading, roaming between mobile networks and Wi-Fi. Both products and use cases include Chargeable User Identity function for Radiator.
For more information about CUI deployments, please contact our sales team at sales@radiatorsoftware.com
