A method for performing initial registration is provided. The method includes receiving a server timeout message, the server timeout message including at least a field set to a value equal to a value received during a first registration. The method further includes initiating restoration procedures by performing an initial registration.

Methods for operating a device and for managing bootstrapping of devices are disclosed. The method (100) for operating a device comprises computing (102) a derivative of a secret shared between the device and a server entity of a network, generating (104) a temporary bootstrap URI by combining at least a part of the computed derivative with a static bootstrap URI for the network, and sending (106) a bootstrap request to the temporary bootstrap URI. The method for managing bootstrapping of devices comprises generating temporary bootstrap URIs corresponding to devices operable to connect to a network, and updating a network DNS registry to map the generated temporary bootstrap URIs to the IP address of at least one of a bootstrap server instance reachable via the network and/or a bootstrap load balancer. Also disclosed are a device, a bootstrap load balancer, a bootstrap server, and a computer program.

Apparatuses and methods for interworking stand-alone NPN-IMS are disclosed. In one embodiment, a method implemented in a proxy-call session control function (P-CSCF) node includes receiving, from a non-public network, NPN, user equipment, UE, an Internet Protocol, IP, Multimedia Subsystem, IMS, registration request, the IMS registration request including an NPN identifier associated with the NPN UE; and as a result of receipt of the IMS registration request, at least one of obtaining and using an IMS identifier associated with the NPN identifier of the NPN UE to register the NPN UE in an IMS network. In one embodiment, a method implemented in a non-public network (NPN) user equipment (UE) includes sending an IMS registration request, the IMS registration request including an NPN identifier associated with the NPN UE and the IMS registration request being for an individual IMS registration of the UE.

Methods for operating a device and for managing bootstrapping of devices are disclosed. The method (100) for operating a device comprises computing (102) a derivative of a secret shared between the device and a server entity of a network, generating (104) a temporary bootstrap URI by combining at least a part of the computed derivative with a static bootstrap URI for the network, and sending (106) a bootstrap request to the temporary bootstrap URI. The method for managing bootstrapping of devices comprises generating temporary bootstrap URIs corresponding to devices operable to connect to a network, and updating a network DNS registry to map the generated temporary bootstrap URIs to the IP address of at least one of a bootstrap server instance reachable via the network and/or a bootstrap load balancer. Also disclosed are a device, a bootstrap load balancer, a bootstrap server, and a computer program.

A method for performing initial registration is provided. The method includes receiving a server timeout message, the server timeout message including at least a field set to a value equal to a value received during a first registration. The method further includes initiating restoration procedures by performing an initial registration.

A communication session for a UE can be restored in the event of serving call session control function (S-CSCF) node unavailability and/or application server (AS) unavailability by storing, prior to IMS unavailability, attribute-value pairs (AVPs) at a home subscriber server (HSS). These AVPs can be used independently by individual IMS nodes to restore a communication session for a UE due to an unavailable IMS node. When a first S-CSCF node becomes unavailable, a proxy CSCF (P-CSCF) node can send a SIP request originating from the UE to a second S-CSCF node. The second S-CSCF node can then send a request to the HSS for an identifier of an AS associated with the UE. Upon receipt of the AS identifier (e.g., an active AS name AVP) from the HSS, the second S-CSCF node can send the SIP request to the AS in order to restore the communication session for the UE.

The disclosure relates to a communication technique for converging, with an IoT technology, a 5G communication system for supporting a higher data transmission rate than a 4G system, and a system therefor. The disclosure may be applied to intelligent services, such as smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail businesses, and security and safety related services, on the basis of 5G communications technologies and IoT-related technologies. A method for operating relay UE in a mobile communication system includes transmitting, to a network node connected to the relay UE, a remote UE report message including remote UE information about a remote UE accessing a network via the relay UE, wherein the remote UE information includes IP address information allocated to the remote UE; starting a timer upon transmitting the remote UE report message to the network node; receiving, from the network node, a response message in reply to the remote UE report message; and stopping the timer upon receipt of the response message from the network node. the IP address information includes an IP address and port information of the remote UE in case that IPv4 is used as an address type.

A Breakout Gateway Control Function (BGCF) determines a geographic location information (e.g., a major trading area (MTA) information) from a SIP INVITE header information (e.g., from a P-Access-Network-Info (PANI) header information) and modifies the SIP URI in the SIP INVITE request by adding, deleting, or modifying values (e.g., prepending a number prefix to the URI) to generate a SIP URI that is based on the geographic location information.

A method for improved handling of emergency calls in a roaming scenario includes: a voice call being initiated by the user equipment via the user equipment transmitting a first message directed to a network node of the home telecommunications network, the first message comprising the specific emergency call telephone number; wherein a second message is transmitted to the network node of the home telecommunications network, the second message comprising an emergency call information, the emergency call information being indicative of the use of a valid emergency call telephone number in relation of the voice call; and a third message being generated by the node of the home telecommunications network, wherein the third message is transmitted to a network node of the visited telecommunications network, and forwarded, as a fourth message, to the user equipment to trigger an emergency call procedure.

In an attempt to establish a communication session between a first communication entity and a second communication entity, a first message is received. For example, the first message may be a SIP INVITE message. A determination is made, based on a registration message from the first communication entity and/or the second communication entity, that at least one of the first communication entity or the second communication entity is Internet Protocol (IP) version intolerant. In response to determining that the at least one of the first communication entity or the second communication entity is IP version intolerant, one or more IP addresses are adapted in messages (e.g., the SIP INVITE message) for establishing the communication session. The adaption changes/removes the one or more IP addresses to a different IP version to ensure proper IP compatibility.