1. A customizable mobile broadband network system, comprising a forwarding layer, a control layer, and a capability opening layer, wherein: the forwarding layer connects to the control layer through a first open interface, and is configured to provide a forwarding capability of the mobile broadband network system, wherein the first open interface is configured to open the forwarding capability to the control layer; the control layer connects to the capability opening layer through a second open interface, and is configured to provide a control capability of the mobile broadband network system, wherein the second open interface is configured to open the control capability and the forwarding capability to the capability opening layer; and the capability opening layer is configured to receive, through a third open interface, a network customization request from a user, and combine the control capability and/or the forwarding capability according to the network customization request, so as to manage a customized-network instance.