Implementation of WLAN manageable fast switching technology in AP (1)

In recent years, the demand for mobility has attracted more and more attention. Mobility refers to the ability to move or roam. Wireless LAN (WLAN) devices can provide unrestricted mobility. WLAN uses wireless communication technology to establish a network within a certain range. It is a product of the combination of computer networks and wireless communication technology. It uses a wireless multi-access channel as the transmission medium and provides the functions of a traditional wired LAN, enabling users to access broadband networks anytime, anywhere and freely.

WLAN technology uses electromagnetic waves to send and receive data in the air, so that computers on the Internet can be moved and can quickly and conveniently solve the problem of network channel connectivity that is not easy to achieve in wired mode. The task of the IEEE Standard Working Group for wireless LAN is to study the global standards of wireless devices and networks working at 1 Mb/s and 2 Mb/s data rates and 2.4 GHz open frequencies, IEEE published the June 1997 Protocol in 802.11, which is one of the first generation wireless LAN standards. 802.11 the Protocol physical layer defines the signal characteristics and modulation modes of data transmission. The media access control layer involves technical specifications such as air interface communication protocols, including switching content. Subsequently, in order to have higher data communication bandwidth, more functions, and more rapid development of wireless LAN, the IEEE workgroup has successively released IEEE 802.11a/B/g protocol. The improvement of WLAN's mobile performance is undoubtedly the key to the rapid promotion of WLAN.

Based on the analysis of the currently used WLAN switching technology, that is, the site (STA) Active switching technology, to ensure the efficiency and security of switching, this paper proposes a manageable fast switching (MFHO) technology. This technique can be implemented in two ways, namely, the switch instruction method and the switch application method. Both methods support switching between Access Point (AP) and Access Controller (AC.

1. Management of the implementation of the fast switching method on the AP

1.1 current WLAN Switching Technology

Currently, most wireless LAN systems follow the IEEE 802.11 protocol and adopt the site active switching technology defined in it. That is, in an extended service set (ESS), the STA is based on the signal quality of the blank port, select the AP with the strongest signal as the target access point, and in the roaming protocol (IAPP) between access points, the STA switching process between different AP in the same ESS is as follows:

(1) STA finds a new target AP, disconnects the current AP, and sends a reconnection request to the target AP.

(2) The target AP establishes a new connection with the STA, sends a switch notification to the current AP, and updates the L2 route.

(3) The current AP receives the switch notification, transfers the STA-related information to the target AP through the security channel of the distributed system (DS), and clears the local STA-related information.

(4) The target AP receives and stores STA-related information, and switches the STA to the target AP.

The above switchover is completed through the connection or re-connection (pre-Authentication) process, and the switching delay is long. Services with strict latency requirements will experience significant interruptions during the switchover. When switching through the reconnection process, the end-site switching process lacks security guarantee because no security authentication is required for switching the target AP. The random STA active switchover brings unnecessary difficulties to the optimization process such as server Load balancer. In the above switchover, the AP lacks a mechanism to effectively control and manage the switching process. Therefore, the switching efficiency, QoS requirements, security and optimization measures are difficult to guarantee.

1.2 MFHO Technology

Considering the shortcomings of the current STA active switching technology, this paper proposes the managed fast switching (MFHO) technology, which places the control of switching on the AP or AC side, during User Information transplantation, You can transmit a variety of user information, including user identification information, security information, and application business information, to the target AP through the Secure Channel of the wired network, it effectively ensures the switching efficiency and security, and supports switching requirements for different QoS services, facilitating the expansion of multiple services in the future. In MFHO technology, Stas perform the following switching between different APS under the same ESS:

(1) The STA reports the environment information of the wireless air interface (or applies for switching ).

(2) AP/AC determines whether a switchover is performed based on the environment information and DS information of the wireless air interface.

(3) port the STA information and update the L2 route.

(4) switch the STA to the target AP.

MFHO technology can be implemented through two air interface methods, namely the switch indication method and the switch application method. The difference between the two is that the former STA uses the wireless air interface environment information to convert the STA information, for example, the basic service Region ID (BSSID), Media Access Control (MAC) Address, authentication status, encryption mode, and key are notified to the AP. The latter sends information about the STA to the AP through the switchover application. The switch decision can be performed on the AP, or on the upper-level AC, and the judgment result is notified to the AP. After the AP obtains the switch decision result, it returns a switch Request Response to the STA or instructs a switch notification. The STA switches to the target AP based on the information.

Compared with the STA active switchover technology, the STA active failover technology has a large latency, including synchronization, reconnection, and L2 route update; the maximum latency of MFHO switching is determined by the maximum latency among synchronization, STA information transplantation, and L2 route update. MFHO uses pre-authorization and authorization dependency technologies, perform mutual authentication between the AP and the AC before switching, and extend the authorization of an AP to the STA to other trusted AP, thus reducing the authentication delay during the switching process. The STA active switching technology does not take into account the load of the target AP, which may easily lead to frequent switching between multiple APs, reducing the switching efficiency, the MFHO switching technology allows the AP to determine the Switching Based on the Load Distribution in the ESS and the load policies of each AP, which greatly improves the switching success rate and also provides a mechanism to avoid frequent switching. The STA active switchover technology does not provide a security guarantee for the switchover. Although the security switching process based on remote dial-up user authentication (RADIUS) is proposed in IAPP, the inefficient switching process still has the potential threat of DoS attacks. MFHO switching technology can use security policies in the wired network to ensure mutual authentication and authorization between the AP and AC, and ensure the switching security of the STA under the AP control.

1.3 Implementation of MFHO Technology in AP

With the support of the MFHO technology on the STA side, the implementation process of the MFHO Technology in the AP is as follows:

(1) The STA establishes a connection with the current AP.

(2) The current AP stores information about the connected STA, the load information of the current AP itself, and the load information of the entire wireless network.

(3) Send an air status change notification or switch application request to STA.

(4) The current AP determines whether the switchover has occurred based on the information of the wireless air interface environment (or switching application) and DS reported by the STA. The AP checks whether the target AP is valid Based on the AP's own load information and current network load information to determine whether the STA needs to be switched Based on the Air Port Environment update notification or switch application sent by the STA, and the target AP to be switched to (if there are multiple target APs ). If the current AP does not agree to switch, it is switched to (5). If the current AP requires switching, it is switched to (6 ).

(5) The current AP does not process the request or sends a rejected switch Request Response to the STA. The switch ends.

(6) The current AP copies the STA information to the target AP through the security channel on DS.

(7) The target AP updates the STA status to the switching status. If the STA information is successfully handed over, it is forwarded to (10 ). If the information transfer fails, it is switched to (8 ).

(8) The target AP sends a failed transplant response to the current AP.

(9) stop the current switch of the current AP and switch to (5 ).

(10) The target AP sends a successful transplant response to the current AP.

(11) when the current AP receives a request to send a switch request to the STA or allows a switch request, it notifies the STA to switch to the target AP.

(12) The current AP updates the local L2 forwarding table, changes the route of the STA on DS, and deletes the local STA information.

(13) The current AP publishes two-layer devices in DS to forward the update broadcast to the table.

(14) The target AP updates the local L2 forwarding table, and updates the local status of the STA to the switched status.

(15) STA sends a reconnection request to access the target AP.