An interworking entity comprising: a first network interface configured to communicate with a remote unit over a non-Third Generation Partnership Project, non-3GPP, access network, wherein the non-3GPP access network is a WLAN access network; a second network interface configured to communicate with a mobile core network, wherein the mobile core network is a Fifth Generation 3GPP mobile core network; a processor configured to: receive a first authentication request for the remote unit, over the non-3GPP access network, the first authentication request being part of a first authentication procedure for the remote unit; create an attach request for the mobile core network on behalf of the remote unit in response to the received first authentication request; send the created attach request to the mobile core network to initiate attachment of the remote unit to the mobile core network; receive a second authentication request from the mobile core network, wherein the second authentication request is part of a second authentication procedure different from the first authentication procedure; transform the second authentication request into a third authentication request of the first authentication procedure; and use an authentication response of the first authentication procedure to complete attachment of the remote unit to the mobile core network. a first network interface configured to communicate with a remote unit over a non-Third Generation Partnership Project, non-3GPP, access network, wherein the non-3GPP access network is a WLAN access network; a second network interface configured to communicate with a mobile core network, wherein the mobile core network is a Fifth Generation 3GPP mobile core network; a processor configured to: receive a first authentication request for the remote unit, over the non-3GPP access network, the first authentication request being part of a first authentication procedure for the remote unit; create an attach request for the mobile core network on behalf of the remote unit in response to the received first authentication request; send the created attach request to the mobile core network to initiate attachment of the remote unit to the mobile core network; receive a second authentication request from the mobile core network, wherein the second authentication request is part of a second authentication procedure different from the first authentication procedure; transform the second authentication request into a third authentication request of the first authentication procedure; and use an authentication response of the first authentication procedure to complete attachment of the remote unit to the mobile core network. receive a first authentication request for the remote unit, over the non-3GPP access network, the first authentication request being part of a first authentication procedure for the remote unit; create an attach request for the mobile core network on behalf of the remote unit in response to the received first authentication request; send the created attach request to the mobile core network to initiate attachment of the remote unit to the mobile core network; receive a second authentication request from the mobile core network, wherein the second authentication request is part of a second authentication procedure different from the first authentication procedure; transform the second authentication request into a third authentication request of the first authentication procedure; and use an authentication response of the first authentication procedure to complete attachment of the remote unit to the mobile core network.