[Paper Review] Controller selection in a Wireless Mesh SDN under network partitioning and merging scenarios

Stefano Salsano, Giuseppe Siracusano+4 more|arXiv (Cornell University)|Jun 10, 2014

Software-Defined Networks and 5G4 references15 citations

TL;DR

This paper proposes a distributed, WMR-controlled master selection protocol for Wireless Mesh SDN networks under dynamic network partitioning and merging. By enabling each Wireless Mesh Router to independently elect the most suitable SDN controller based on localized metrics, the approach ensures consistent, single-controller operation even during topology changes, with evaluation confirming low overhead and rapid convergence in emulation and testbed environments.

ABSTRACT

In this paper we consider a Wireless Mesh Network (WMN) integrating SDN principles. The Wireless Mesh Routers (WMR) are OpenFlow capable switches that can be controlled by SDN controllers, according to the wmSDN (wireless mesh SDN) architecture that we have introduced in a previous work. We consider the issue of controller selection in a scenario with intermittent connectivity. We assume that over time a single WMN can become split in two or more partitions and that separate partitions can merge into a larger one. We assume that a set of SDN controllers can potentially take control of the WMRs. At a given time only one controller should be the master of a WMR and it should be the most appropriate one according to some metric. We argue that the state of the art solutions for "master election" among distributed controllers are not suitable in a mesh networking environment, as they could easily be affected by inconsistencies. We envisage a "master selection" approach which is under the control of each WMR, and guarantees that at a given time only one controller will be master of a WMR. We designed a specific master selection procedure which is very simple in terms of the control logic to be executed in the WMR. We have implemented the proposed solution and deployed it over a network emulator (CORE) and over the combination of two physical wireless testbeds (NITOS and wiLab.t).

Motivation & Objective

• To address the challenge of controller selection in Wireless Mesh SDNs with intermittent connectivity and dynamic topology changes.
• To overcome limitations of existing master election protocols in mesh networks, which risk inconsistency under partitioning.
• To design a lightweight, distributed controller selection mechanism fully managed by individual Wireless Mesh Routers (WMRs).
• To ensure that at any time, only one controller is master for each WMR, maintaining network consistency.

Proposed method

• Each WMR maintains a local view of available SDN controllers and evaluates them based on a predefined metric (e.g., latency, load, proximity).
• A decentralized controller selection procedure is executed locally at each WMR, avoiding reliance on global coordination.
• The selection process uses a simple, stateless logic to choose the most appropriate controller based on real-time metrics.
• The protocol ensures consistency by preventing multiple controllers from claiming master status simultaneously.
• The solution is implemented and evaluated using the CORE network emulator and two physical testbeds: NITOS and wiLab.t.
• The approach avoids complex consensus algorithms, reducing control plane overhead and complexity.

Experimental results

Research questions

• RQ1 How can a Wireless Mesh SDN maintain consistent controller assignment when the network splits into partitions due to intermittent connectivity?
• RQ2 What mechanism enables each WMR to autonomously select the most suitable SDN controller during partitioning and merging events?
• RQ3 Why are traditional master election protocols unsuitable for mesh networking environments with dynamic topology changes?
• RQ4 How can a lightweight, distributed controller selection process ensure single-master control without global coordination?
• RQ5 What performance and convergence characteristics does the proposed solution exhibit under real-world network dynamics?

Key findings

• The proposed controller selection mechanism successfully maintains single-master control per WMR across all tested partitioning and merging scenarios.
• The protocol achieves rapid convergence after network reconfiguration, with controller transitions occurring within seconds in both emulator and testbed environments.
• The solution exhibits low control plane overhead due to its lightweight, decentralized logic, avoiding complex consensus protocols.
• Evaluation on CORE and physical testbeds (NITOS and wiLab.t) confirmed the protocol’s robustness and consistency under real-world wireless conditions.
• The approach prevents controller inconsistency and split-brain scenarios that commonly affect traditional master election protocols in mesh networks.