Research And Implementation Of The Wlan High Reliability Based On VRRP

With the rapid development of Wireless Local Area Network (WLAN) technology in recent years, it has become an indispensable data transmission means in the Internet Age. However, the continual increasing of the number of WLAN users and the expanding of the WLAN scale lead to the reach of the WLAN larger and larger and once the WLAN breaks down or even is disabled, it may bring immeasurable losses to users. Therefore, the reliability of the WLAN has become one of the biggest bottlenecks restricting the development of WLAN.The deployed network architecture of current WLANs mostly are access point controller (AC) plus Fit access point (AP). All the APs users accessed are centralized controlled by the AC and the breaking down of the AC may influence the entire WLAN. A way named AC backup is often applied to circumvent the AC breaking down and thus to improve the reliability of WLANs. The shortcomings of the widely used dual-link AC backup mechanism are analyzed and an AC hot-backup system solution based on Virtual Router Redundancy Protocol (VRRP) is proposed to better ensure the high reliability of the WLAN.Firstly, the802.11wireless network and the network architecture of the WLAN are introduced. The Control And Provisioning of Wireless Access Point Protocol (CAPWAP) used in the centralized WLAN architecture is described in detail, and the advantages and limitations of the centralized WLAN network architecture are discussed, then the AC backup mechanisms used to solve the limitations of the centralized WLAN architecture are analyzed, the disadvantages of the AC backup mechanisms are pointed out, and also the operating mechanism of the VRRP is in-depth researched.Subsequently, the basic design idea of the AC hot-backup system based on VRRP is described. In this scheme, for the reason that the real CAPWAP link between the backup AC and APs are not established, a backup CAPMAP tunnel is needed to be simulative established to ensure a smooth transition of the AP flow after the active-standby switch of the system, and the realization of the backup of the radio frequency information. As a result of that the synchronization of the relevant information of the APs between the master AC and the backup AC is necessary. The software requirement is analyzed and modeled by using a data flow diagram (DFD) method, a WLAN VRRP hot-backup state machine based on the project requirement is designed, and the processing of the main module based on different tasks when the state machine stays in different states is particular designed. Also, all the functions of the system are achieved according to the preceding design and the specific process flow is described.Finally, the system testing is performed in the network builded by real equipments. The experimental results show that the scheme can realize the hot-backup mechanism between the master AC and the backup AC and effectively ensure the reliability of the WLAN, and thus the feasibility of the design scheme is verified.