Software-Defined Networking 2

2Decentralized SDN Control: Major Open Challenges

2.1. Introduction

While offering the potential to transform and improve current networks, the SDN initiative is still in the early stages of addressing the wide range of challenges involving different disciplines. In particular, distributed control of SDNs faces a series of pressing challenges that require our special consideration.

This chapter provides a thorough discussion of the major challenges of distributed SDN control, along with some insights into emerging and future trends in this area. These challenges include the issues of scalability (section 2.2), reliability (section 2.3), state consistency (section 2.4), interoperability (section 2.5), monitoring and security (section 2.6).

In the previous chapter, we surveyed the most prominent state-of-the-art distributed SDN controller platforms and, more importantly, we discussed the different approaches adopted to tackle the above challenges and proposed potential solutions. Table 2.1 gives a brief summary of the main features and key performance indicators (KPIs) of the discussed SDN controllers. Physically centralized controllers such as NOX (Gude et al. 2008), POX and FloodLight suffer from scalability and reliability issues. Solutions such as DevoFlow (Curtis et al. 2011; Abuarqoub 2020) and DIFANE (Yu et al. 2010; Abuarqoub 2020) attempted to solve these scalability issues by rethinking the OpenFlow protocol, whereas most SDN groups geared their focus toward distributing ...