Taxonomy of controller placement problem (CPP) optimization in Software Defined Network (SDN): a survey

Abstract

The new network requirements are rising with internet scalability and expansion of its coverage. The traditional network cannot support recent needings, so a new architecture has been proposed for the future networks called Software Defined Network (SDN). This architecture makes the network more programmable, flexible, and controllable, though the scalability is the most important challenge on which the researchers are working in SDN. Multiple controllers are a necessity of current SDN, so the optimum number of controllers and their placement is a problem called controller placement problem (CPP). There are defined different functions to optimize scalability, reliability, and others in SDN which consider various metrics in recent research papers. This optimization problem is NP-hard. In this paper, we survey the CPP optimization in recent well-known papers to extract optimization strategies, objective functions, and solutions. We finally reveal a new taxonomy of cutting-edge studies about solutions of CPP optimization in the SDN from different dimensions. CPP solutions based on objective functions, metrics and traits are classified in this article. Furthermore, we put forward the new challenges and metrics which can be reckoned in CPP to be optimized. This paper can be useful for those working on CPP optimization in SDN to expose the objective functions, variables and metrics.