Selection of successive authentication methods

A method of authenticating a user accessing a service in a second network, the user being subscriber of a home network and previously authenticated in a first network through which the user accesses the service, the method comprising the steps of:

• authenticating the user in the first network, which the user accesses through, with a first authentication method selected in an authentication server of the home network in accordance with access and subscription information for the user;
• where the user accesses the service in the second network, requesting reservation of resources for the service to a rules enforcement device, in charge of handling resources;
• requesting control rules for the resources from the rules enforcement device to a control rules server in charge of installing control rules;
• submitting to the control rules server information about the first authentication method applied to the user;
• determining at the control rules server, by applying authentication policies, that a further authentication of the user with a second authentication method is required;
• and
• instructing from the control rules server to the authentication server to force the further authentication of the user with the second authentication method,
• wherein the authentication server is a Home Subscriber Server (HSS) where the user holds a subscription,
• wherein the rules enforcement device is a Policy and Charging Enforcement Function (PCEF) providing service data flow detection, and
• wherein the control rules server is a Policy and Charging Rules Function (PCRF) providing control functions and installing corresponding control rules.