| CPC H04L 65/4061 (2013.01) [H04L 65/1104 (2022.05); H04W 4/10 (2013.01); H04W 4/16 (2013.01)] | 15 Claims |

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1. An apparatus, comprising:
at least one processor; and
at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:
receive, from a first client, a call request comprising address information for calling at least one second client, the address information being a Functional Alias, wherein the Functional Alias is activated by the at least one second client;
in response to receiving the call request at the apparatus, send, to a server, a request to resolve the Functional Alias to at least one Mission Critical Push to Talk Identifier of the at least one second client that has activated the Functional Alias;
receive, at the apparatus from the server, the at least one Mission Critical Push to Talk Identifier of the at least one second client;
receive, at the apparatus from the server, two or more Mission Critical Push to Talk Identifiers of the at least one second client;
in response to receiving the two or more Mission Critical Push to Talk Identifiers of the at least one second client, determine, based on a policy, whether to: send a call request to each Mission Critical Push to Talk Identifier of the two or more Mission Critical Push to Talk Identifiers; or select one Mission Critical Push to Talk Identifier of the two or more Mission Critical Push to Talk Identifiers to send the call request; and
based on the determining, send, from the apparatus, the call request to the at least one second client.
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