A communication system , comprising: a plurality of messaging systems for delivering messages based on a respective message signaling protocol ; a plurality of packet core networks , wherein each packet core network is designed according to a respective packet core network technology; a subscription and location server , configured to store for each subscriber of a plurality of subscribers associated with a corresponding User Equipment, UE : a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a UPSMS system , configured to extend a message received from one of the messaging systems based on a message signaling protocol extension that extends the message signaling protocol by including an indication that the UPSMS service is supported for a respective subscriber, and to forward the extended message to the subscription and location server , wherein the subscription and location server is configured to authenticate a subscriber based on the subscriber identity, and to identify for an authenticated subscriber, for whom the UPSMS service is supported, a packet core network of the plurality of packet core networks that is connected to the corresponding UE , based on the subscriber identity, and to deliver the extended message via the identified packet core network to the corresponding UE . a plurality of messaging systems for delivering messages based on a respective message signaling protocol ; a plurality of packet core networks , wherein each packet core network is designed according to a respective packet core network technology; a subscription and location server , configured to store for each subscriber of a plurality of subscribers associated with a corresponding User Equipment, UE : a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a UPSMS system , configured to extend a message received from one of the messaging systems based on a message signaling protocol extension that extends the message signaling protocol by including an indication that the UPSMS service is supported for a respective subscriber, and to forward the extended message to the subscription and location server , wherein the subscription and location server is configured to authenticate a subscriber based on the subscriber identity, and to identify for an authenticated subscriber, for whom the UPSMS service is supported, a packet core network of the plurality of packet core networks that is connected to the corresponding UE , based on the subscriber identity, and to deliver the extended message via the identified packet core network to the corresponding UE . <EOS>