1. Field
The following description relates to a virtual network, and more specifically, to routing control for a software-defined networking (SDN).
2. Description of the Related Art
A programming methodology that has developed and matured in the computer industry is expanding into the area of networking. In light of this, software-defined networking (SDN) has emerged as a new networking paradigm that can provide flexibility of network configurations. SDN is a next-generation networking technology that enables the control of networks via software programming, enabling networks to be programmable by a network administrator unlike in the existing closed network environment, and thereby allowing for more convenient handling of network control and management. Specifically, SDN is gaining in popularity as a technology that can fundamentally solve high cost and complexity in construction, operation, management of existing networks. In SDN, network equipment is divided into the control plane and data transmission plane, which are connected via open interfaces. The control plane is controlled by a centralized controller, controlling the data transmission plane via programming. Current SDN is in the initial stage of research and development and has been applied to small scale networks, such as a data center network on a campus network, which have no compatibility issues with external networks. Also, various researches have been conducted regarding the application of SDN to large scale networks, such as the network of Internet service provider (ISP), to improve the efficiency of network operation/management.
Scalability is the most important issue in the construction of large scale SDN. Initially, SDN was designed to simplify the existing network control structure, providing a single centralized controller to control the entire network. However, as the scale of a network increases, there are more switches to be controlled and, in turn, the amount of control traffic generated by the switches increases. So as the control traffic concentrates on the controller and load on the controller increases, it becomes impossible to control the entire network using only one controller. In addition, as the distance from switches to the controller increases, the switches' flow processing speed may decrease. Also, if flow processing traffic occurs beyond the hardware capacity of the controller, the overall network control may not be properly carried out.
U.S. Patent Application Publication No. US 2012/0226733 discloses that a cloud computing system and method for distributing and controlling traffic in the cloud computing system, wherein the cloud computing system includes a plurality of local data centers and a control center coupled to the plurality of local data centers. The above US patent application only relates to a method for distributing traffic when an amount of traffic to the local data center exceeds a given threshold, and does not disclose the distribution of load from control traffic of virtual networks.