Evaluation and Prevention of MAC Layer Misbehaviours in Public Wireless Hotspots

IEEE 802.11 protocol assumes all the nodes in the network cooperate and adhere to the standard. However, nodes may purposefully misbehave in order to obtain extra bandwidth, conserve resources or disrupt network performance. Previously, Kausanaur proposed a Receiver Trusted MAC protocol (REC-TR-MAC) by extending IEEE 802.11 to prevent Medium Access Control (MAC) sender misbehaviours. This protocol trusts the receiving node (Access Point) in a WLAN and enables the Access Point to allocate the MAC protocol random backoff values for wireless clients. Our research investigates MAC layer node misbehaviours in the context of a Public Wireless Hotspot. REC-TR-MAC has been implemented by porting the legacy code-base to the latest ns2. Furthermore, our evaluation has been extended to incorporate several Access Point misbehaviours to simulate the scenario of an untrusted hotspot (misbehaving access point), which has not been investigated much in the literature. In public wireless hotspot the misbehaving wireless senders could run a malware at the Hotspot to gain the access to, alter the MAC protocol operation. The experiment results show that Hotspot misbehaviours significantly affect the network performance, nodes throughput reduced by 50% and misbehaviour detection accuracy by 40%. The results have also been compared with the standard IEEE 802.11 protocol. This evaluation is important to understand the design principles for a reliable MAC protocol which should be resilient against MAC layer misbehaviours. Finally, this paper describes future improvements for detecting and preventing MAC layer misbehaviours in Wi-Fi networks.

I. Introduction

Public wireless Hotspot uses Wi - Fi technology and acts as an internet Access Point (AP) in public locations. Widespread of public Hotspot making wireless network security important than ever, such networks are more exposed to attackers more than any other network type. Wireless LAN is an infrastructure-based network which is controlled by a centralized AP, which is the receiver of the network of all the connected client nodes. Most of the devices in these networks are running standard IEEE 802.11 protocol. The IEEE 802.11 MAC protocol is used for the coordination and scheduling of transmissions among competing nodes in wireless networks. It assumes that all the nodes in the wireless network ad-here and fully cooperate. However, MAC layer node misbehaviours have been a problematic scenario for WLAN network performance. Due to the vast enhancement of network device adapters' programmability, changing the MAC layer protocol parameters has become easier.