A method of a trusted wireless local area network access gateway for quality of service differentiation via a trusted wireless local area network, the method comprising: receiving, from a user equipment, a packet data network connectivity request including an indication that the user equipment supports Wireless Local Area Network Control Plane multiple bearer packet data network connectivity; determining, based on the indication, that multi-connection mode is available between the user equipment and the trusted wireless local area network; establishing a packet data network connection between the user equipment and the trusted wireless local area network to connect the user equipment to a core network with a default bearer; establishing one or more additional bearers, wherein each of the additional bearers and the default bearer are established with a quality of service characteristic and a quality of service mapping; and causing data traffic to be transmitted over the default bearer and the one or more additional bearers, wherein the data traffic is caused to be transmitted according to a differentiated quality of service based on the quality of service characteristic and the quality of service mapping, wherein the method further comprises a bearer modify procedure comprising: transmitting, to the user equipment, a bearer modify request, including a bearer identity of a bearer to be modified, wherein the method is characterized in that: the bearer modify procedure further comprises: receiving, from the user equipment, as a response to the bearer modify request, a bearer modify reject message which includes the bearer identity and a cause value indicating a reason for rejection of the bearer modify request, wherein the cause value indicates whether or not an invalid bearer identity is the reason for rejection, wherein upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is not the reason for rejection, the trusted wireless local area network access gateway aborts the bearer modify procedure, or upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is the reason for rejection, the trusted wireless local area network access gateway locally deactivates the bearer. receiving, from a user equipment, a packet data network connectivity request including an indication that the user equipment supports Wireless Local Area Network Control Plane multiple bearer packet data network connectivity; determining, based on the indication, that multi-connection mode is available between the user equipment and the trusted wireless local area network; establishing a packet data network connection between the user equipment and the trusted wireless local area network to connect the user equipment to a core network with a default bearer; establishing one or more additional bearers, wherein each of the additional bearers and the default bearer are established with a quality of service characteristic and a quality of service mapping; and causing data traffic to be transmitted over the default bearer and the one or more additional bearers, wherein the data traffic is caused to be transmitted according to a differentiated quality of service based on the quality of service characteristic and the quality of service mapping, wherein the method further comprises a bearer modify procedure comprising: transmitting, to the user equipment, a bearer modify request, including a bearer identity of a bearer to be modified, wherein the method is characterized in that: the bearer modify procedure further comprises: receiving, from the user equipment, as a response to the bearer modify request, a bearer modify reject message which includes the bearer identity and a cause value indicating a reason for rejection of the bearer modify request, wherein the cause value indicates whether or not an invalid bearer identity is the reason for rejection, wherein upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is not the reason for rejection, the trusted wireless local area network access gateway aborts the bearer modify procedure, or upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is the reason for rejection, the trusted wireless local area network access gateway locally deactivates the bearer. the bearer modify procedure further comprises: receiving, from the user equipment, as a response to the bearer modify request, a bearer modify reject message which includes the bearer identity and a cause value indicating a reason for rejection of the bearer modify request, wherein the cause value indicates whether or not an invalid bearer identity is the reason for rejection, wherein upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is not the reason for rejection, the trusted wireless local area network access gateway aborts the bearer modify procedure, or upon receipt of the bearer modify reject message with the cause value indicating that an invalid bearer identity is the reason for rejection, the trusted wireless local area network access gateway locally deactivates the bearer.