Wireless access management design in software defined networks

Abstract

ISP based Wi-Fi Hotspot deployments have emerged potential for offloading cellular traffic through existing hotspot deployments, increasing indoor coverage and providing continuous service access to the end users. ISPs favors the utilization of existing Wi-Fi infrastructure for offloading the cellular traffic. Furthermore, growth in the number of hotspots continues as a result of ISPs investments on Wi-Fi based hotspots. Cisco VNI report also revealed the potential of Wi-Fi Hotspot deployment for service providers by estimating the number of Wi-Fi devices as three-fold of cellular devices by 2020. In addition, ISPs such as Turkish Telecom expands the Wi-Fi Hotspot coverage by offering contracted customers a free Wi-Fi access in public Wi-Fi access areas in exchange of using customer's equipment for broadcasting ISPs SSID and customer's line for carrying the traffic. Indoor coverage area of ISPs also increased with given marketing strategy. Furthermore, the customers benefit from the free access of carrier's Wi-Fi hotspots and reached a continuous service access in public places as well. However, management of radio resources such as channel assignments of hotspots, wireless user access control, flow admission control of the users and new service deployment are the main issues which need to be addressed by the ISPs. Lead access point vendors such as Cisco, Aruba and Ruckus Wireless which holds more than 50% of the market share in top five access point vendors offer vendor-specific solutions for the issues given above. However, architecture and protocol overlay of the Wi-Fi Access Network solution varies for different vendors. Thus, inter-operability of vendor-specific solutions are limited. To this end, service deployment process becomes unnecessarily complex for ISPs when vendor-specific solutions are applied to the field. Additionally, requirement for standardization is highlighted by ISPs and effort has been put by technology pioneers such as Cisco. As a result, CAPWAP [6] is developed and deployed as a solution candidate. What's more, CAPWAP [6] recently became the most common management protocol used for wireless access networks. As a result of bottleneck in traffic relayed to the wireless controller in CAPWAP [6] and requirement for vendor-specific implementation for resource utilization, research in ISP based Wi-Fi access management on vendor-agnostic solutions and resolving the bottleneck problem in controller still needs to be addressed. SDN separates the control logic and the forwarding logic of the network into two separate domains: control plane and data plane. A controller is employed in control plane for running the logical operations of the network such as forwarding logic, access control and firewall etc. The controller installs the forwarding and blocking rules into the flow tables of the access elements placed in the data plane of the SDN topology. The controller installs the rules to the flow tables using a protocol which is standardized by ONF and named as OpenFlow. The access elements placed in the data plane are generic devices designed to run forwarding logic installed in their flow tables by the controller and named as OpenFlow Switches. SDN approach enables the optimization of radio resources and load balancing in the access network using the global view of the controller. The highlighted features of the SDN enhanced together makes SDN a promising candidate for addressing the unresolved problems, vendor-specific nature of existing solutions and bottleneck in traffic relayed to the controller, in management of ISP based wireless access network. To this end, a new wireless access management protocol, SDN-WAM, has been designed within the context of this thesis. SDN-WAM virtualizes each wireless client as an interface of the generic access device. In addition, the access control of wireless users are mapped to the open and shutdown events of interfaces. Traffic monitoring interface module is developed to track the bandwidth consumption of each flow generated by the users. The flow admission is handled by the basic flow admission control algorithm module which utilizes information gathered by the traffic monitoring interface. Finally, the access control of wireless clients are handled by designed access control module, which aims to balance the load of access devices. Additionally, an SDWN testbed has been developed within the context of this thesis to prove the validity of the offered wireless access management protocol. Opendaylight is used as the controller of the SDWN network. Traffic Monitoring Interface Module, Flow Admission Control Algorithm Module and Access Control Module defined in SDN-WAM is implemented as a north-bound module to the Opendaylight. The hardware of OF switches implemented in the testbed consists of Raspberry Pi with Pi-Hut USB Wi-Fi dongle. The wireless driver of OF switches is modified to provide the virtualization function described in SDN-WAM. This thesis is finalized by presenting the monitoring results, which prove the applicability of the given protocol to real-life deployment scenarios.