A method, performed by a second application node (521a2) of an application layer system (520a), for controlling a dedicated service session handover between a first network slice (NS1) and a second network slice (NS2), the method being at least partly performed during a first dedicated service session between a first communications device (512a) (512a) and a second communications device (512b) established over a first dedicated data session which is based on a first default data session of the first communications device (512a) on the first network slice (NS1) of a communications network (500a) comprising the first and the second network slices (NS1, NS2), wherein the first default data session is based on a first network slice identifier (S-NSSAI_1) such that a first network address (IP1) of the first communications device (512a), a first application node (521a1) of the application layer system (520a), and a first access gateway (523a1) of the application layer system (520a) is associated with the first default data session, and the method comprising:
- registering (1001) the first communications device (512a) in the application layer system (520a) for a second default service session to be established over a second default data session, based on a second network slice identifier (S-NSSAI2) such that a second network address (IP2) of the first communications device (512a), the second application node (521a2), and a second access gateway (523a2) is associated with the second default service session;
- receiving (1002), from a first application node (521a1) associated with the first network slice (NS1) and controlling the first dedicated data session, a session controlling message comprising:
- a) the second network address (IP2) of the first communications device (512a);
- b) a context of the first dedicated service session;
- c) a network address of an access gateway (523b) serving the second communications device (512b), to enable the second application node (521a2) to perform network resource reservation and establish a data path with the second communications device (512b) for a second dedicated service session between the first communications device (512a) and the second communications device (512b) based on the second default data session, such that handover of the first dedicated service session between the first network slice (NS1) and the second network slice (NS2) is enabled;
- reserving (1004) network resources of the second access gateway (523a2) for the first dedicated service session to be transferred to the second dedicated service session based on the received session controlling message;
- and
- sending (1005) to the first application node (521a1) a second session controlling message with information related to the reserved network resources of the second access gateway (523a2).