With the rapid development and integration of the Internet, wireless communication network and the Internet of Things, the Internet faces many challenges as a bearer network: a large volume of information exchange, multi-level QoS and smoothly switching multiple access protocols. The Internet should be able to provide a variety of network capacity in a more dynamic and on-demand way, not just only limited network resources provision through virtualization. The elastic network is expected to adapt to network changes by enabling network protocols selection and combination dynamically. Cloud computing illustrates a new Internet-based model of IT resources (hardware, software, data) provision, delivery and consumption as a service. Therefore, network protocols as a service can provide guaranteed quality of service and good quality of experience to users who do not care about any network configuration and network management. In this paper, we proposes a novel idea of network capacity on demand by combining the service provision model of cloud computing with the openness of the network protocol. The related conception and stakeholders of network protocol as service are depicted. Cloud-based network architecture is design to present the provision, delivery and consumption of network capacity on demand and discuss the key features of cloud-based network. Finally, a prototype of cloud-based network is implemented by extending OpenFlow architecture.