A method for unicast link establishment by a first User Equipment, in the following also referred to as UE, comprising: establishing a first sidelink Signaling Radio Bearer, in the following also referred to as SRB, for PC5-S message transmission if a unicast link or a PC5-Radio Resource Control, in the following also referred to as PC5-RRC, connection establishment is initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity, in the following also referred to as ID,; transmitting a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID; receiving a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE; and establishing a third sidelink SRB for PC5-RRC message transmission if the unicast link or the PC5-RRC connection establishment has been successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE, wherein the method further comprises: establishing a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE, characterized in that the method further comprises establishing a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE and the second sidelink SRB is established in response to reception of the second PC5-S message. establishing a first sidelink Signaling Radio Bearer, in the following also referred to as SRB, for PC5-S message transmission if a unicast link or a PC5-Radio Resource Control, in the following also referred to as PC5-RRC, connection establishment is initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity, in the following also referred to as ID,; transmitting a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID; receiving a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE; and establishing a third sidelink SRB for PC5-RRC message transmission if the unicast link or the PC5-RRC connection establishment has been successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE, wherein the method further comprises: establishing a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE, characterized in that the method further comprises establishing a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE and the second sidelink SRB is established in response to reception of the second PC5-S message. establishing a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE, characterized in that the method further comprises establishing a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE and the second sidelink SRB is established in response to reception of the second PC5-S message.