Geo-local routing in IMS

A proxy server of a visited network arranged to route an IP Multimedia Services (IMS) service request message, the proxy server comprising:

• a communication unit configured to receive an initial message from a roaming user agent, the initial message being a geo-local service request message that is meaningful within the visited network;
• and
• a message generation unit configured to generate a modified message based on the initial message, the modified message being a session initiation protocol (SIP) message,
• the communication unit being further configured to:
• forward the modified message to a home network of the roaming user agent,
• receive a subsequent message from the home network of the roaming user agent, the subsequent message being a SIP message and including information for resolving a destination address corresponding to the geo-local service request message, and
• route an IMS message related to the initial message to an IMS entity of the visited network,
• the message generation unit being further configured to generate the IMS message related to the initial message to be directed to the IMS entity based on the subsequent message,
• the modified message including information apart from information included in the initial message and information to enable the home network of the user agent to route the subsequent message to the visited network.

A method for routing an IP Multimedia Services (IMS) service request message, the method comprising:

• receiving, at a proxy server of a visited network, an initial message from a roaming user agent, the initial message being a geo-local service request message that is meaningful within the visited network;
• generating, at the proxy server, a modified message based on the initial message, the modified message being a session initiation protocol (SIP) message, generating the modified message based on the initial message including:
• generating a user part of the modified message, the user part including a zone indication of a geographical zone served by the proxy server, and
• generating a host part of the modified message, the host part including an entity indication of an entity of the visited network resolvable at a home network of the roaming user agent to enable the home network of the roaming user agent to route a subsequent message to the entity of the visited network, the subsequent message being a SIP message and being related to the modified message, the generated host part also including a subdomain part identifying an IMS entity fully resolvable by a redirect server of the visited network and not resolvable in the home network of the roaming user agent;
• and
• forwarding the modified message from the proxy server to the home network of the roaming user agent.

A proxy server of a visited network arranged to route an IP Multimedia Services (IMS) service request message, the proxy server comprising:

• a communication unit configured to receive an initial message from a roaming user agent, the initial message being a geo-local service request message that is meaningful within the visited network;
• and
• a message generation unit configured to generate a modified message based on the initial message, the modified message being a session initiation protocol (SIP) message, the message generation unit being further configured to:
• generate a user part of the modified message to include a zone indication of a geographical zone served by the proxy server, and
• generate a host part of the modified message to include an entity indication of an entity of the visited network resolvable at the home network of the roaming user agent to enable the home network of the roaming user agent to route a subsequent message to the entity of the visited network, the subsequent message being a SIP message and being related to the modified message, the generated host part also including a subdomain part identifying an IMS entity fully resolvable by a redirect server of the visited network and not resolvable in the home network of the roaming user agent,
• the communication unit further configured to forward the modified message to a home network of the roaming user agent.