Regional registration for a mobile IP enabled system

A gateway foreign agent included in a system having a hierarchical structure comprising a mobile node, at least one foreign agent, at least one said gateway foreign agent and a home agent, said gateway foreign agent being configured for:

• intercepting a registration request from a mobile node to its home agent, said registration request including a first care-of address for said mobile node;
• determining whether there is an existing entry in a visitor list for said mobile node;
• if said entry exists, updating said entry;
• if no entry exists, creating an entry in said list for the mobile node, adding a second care of address as an extension to said registration request, and sending said registration request with said address extension to said home agent;
• sending a registration reply to said mobile node;
• and
• maintaining in a gateway foreign agent a first and a second lifetime value, wherein said first lifetime value corresponds to the lifetime of a registration by said mobile node with its home agent, and said second lifetime value corresponds to the lifetime of a registration by said mobile node with a gateway foreign agent.