A computing system to implement Quality of Service, QoS, over a Universal Serial Bus, USB, interface, by linking a network defined QoS at the USB device with an IP based application layer at the USB host, the system comprising: a host; a modem; a number of bearers; whereby each bearer supports a number of IP flows, each of which being associated with a specific application; the USB interface coupling the host and the modem, the USB interface comprising: a plurality of logical channels established for communication between the host and the modem, whereby each logical channel includes logical channel endpoints and; whereby a specific logical channel of the plurality of logical channels is associated with a specific set of packet filter rules for a specific QoS; the modem being adapted: - to receive traffic flow information from the network; - to generate packet filtering rules based on the traffic flow information whereby the packet filtering rules contain filter criteria to be used to determine the IP packets to be sent over each bearer; and - to send the packet filtering rules from the modem to the host; the host being adapted: - to implement a distribution function in accordance with the packet filtering rules, whereby the host uses the packet filtering rules to distribute IP packets to the correct logical channel endpoints; the modem being furthermore adapted: - to couple each bearer of the number of bearers with the appropriate logical channel (116; 118) of the USB interface in accordance with the applicable QoS rules, whereby each logical channel (116; 118) is associated with a particular bulk OUT endpoint, at which incoming IP packets from the host are received by the modem. a host; a modem; a number of bearers; whereby each bearer supports a number of IP flows, each of which being associated with a specific application; the USB interface coupling the host and the modem, the USB interface comprising: a plurality of logical channels established for communication between the host and the modem, whereby each logical channel includes logical channel endpoints and; whereby a specific logical channel of the plurality of logical channels is associated with a specific set of packet filter rules for a specific QoS; the modem being adapted: - to receive traffic flow information from the network; - to generate packet filtering rules based on the traffic flow information whereby the packet filtering rules contain filter criteria to be used to determine the IP packets to be sent over each bearer; and - to send the packet filtering rules from the modem to the host; - to receive traffic flow information from the network; - to generate packet filtering rules based on the traffic flow information whereby the packet filtering rules contain filter criteria to be used to determine the IP packets to be sent over each bearer; and - to send the packet filtering rules from the modem to the host; the host being adapted: - to implement a distribution function in accordance with the packet filtering rules, whereby the host uses the packet filtering rules to distribute IP packets to the correct logical channel endpoints; - to implement a distribution function in accordance with the packet filtering rules, whereby the host uses the packet filtering rules to distribute IP packets to the correct logical channel endpoints; the modem being furthermore adapted: - to couple each bearer of the number of bearers with the appropriate logical channel (116; 118) of the USB interface in accordance with the applicable QoS rules, whereby each logical channel (116; 118) is associated with a particular bulk OUT endpoint, at which incoming IP packets from the host are received by the modem. - to couple each bearer of the number of bearers with the appropriate logical channel (116; 118) of the USB interface in accordance with the applicable QoS rules, whereby each logical channel (116; 118) is associated with a particular bulk OUT endpoint, at which incoming IP packets from the host are received by the modem.