OpenCAPWAP: An open source CAPWAP implementation for the management and configuration of WiFi hot-spots

Abstract

The Control And Provisioning of Wireless Access Points (CAPWAP) protocol is under definition within the IETF to enable an Access Controller (AC) to manage a collection of Wireless Termination Points (WTPs). CAPWAP aims at simplifying the deployment and control of large scale, possibly heterogeneous, wireless networks. We present the first open source implementation of the CAPWAP protocol along with early experimental results aiming at the assessment of its reliability and performances. The paper ends describing applications of the CAPWAP protocol to management and QoS scenarios and discussing benefits and technical issues concerning its use.

Introduction

The notion of Mobile Internet relies on scenarios where mobile users may have access anytime and anywhere to conventional and emerging Web applications requiring multimedia and interactive communications. Wireless access networks are the key element to implement these scenarios and much work has been done in recent years to develop and improve wireless technologies, including the introduction of support for mobility and Quality of Service. In this respect, special interest has been paid to wireless local area networks (WLANs) based on the IEEE 802.11 standard [4], that exhibits characteristics useful to pursue the goals of the Mobile Internet, including a large number of installations in a wide range of contexts.

Large deployments of Access Points pose serious problems in defining consistent strategies for their management, configuration and control. These issues forced network vendors to propose proprietary centralized solutions aiming at simplifying functionalities commonly requested by network administrators. All proposed solutions share two common elements: (i) they split functionalities that APs provide and (ii) they add more centralized functions for the monitoring and the remote control of the network. Splitting functionalities of APs allows the implementation of more flexible network infrastructures. Indeed, it allows centralizing the management of critical functions like channel selection, authentication and encryption. Whereas, leaving in the APs time-critical functions, like beacon generation and frames’ acknowledgment, avoids the introduction of expensive components, like high performance interconnections, making proposed solutions competitive on the market. Moreover, the introduction of additional proprietary functions may further increase the level of flexibility in configuring and managing the network.

Recently, an Internet Engineering Task Force (IETF) Working Group, named Control and Provisioning of Wireless Access Points (CAPWAP), started its activity with the goal of defining standard solutions to such issues. In particular, the CAPWAP WG focused on problems like configuration, monitoring, control and management of large scale deployments of wireless networks in general, and of IEEE 802.11 networks [6] in particular, identifying a number of functions that should be provided in such scenarios. The WG is currently working on the definition of a protocol, the CAPWAP protocol, capable of providing interoperability among devices supporting these functions.

In this paper we present our open source implementation of CAPWAP based on [1], [2]. Section 2 describes the CAPWAP protocol and CAPWAP functionalities for the management of IEEE 802.11 networks. Section 3 describes the design and the implementation of OpenCAPWAP, our open source implementation [7]. Section 4 reports the results of some preliminary performance tests on the implementation, while Section 5 discusses scenarios where using CAPWAP may introduce improvements in network management and QoS support. Finally, Section 6 concludes the paper with the future perspectives of this activity.