CCIE must know:Detailed WLAN WDS technology
The wireless distribution system WDS (Wireless Distribution System) means that APs connect two or more independent local area networks through wireless links to form an interconnected network to realize data transmission.
In a traditional WLAN network, a wireless channel is used as the transmission medium between the STA and the AP, and the uplink of the AP is a wired network. In order to expand the coverage area of the wireless network, devices such as switches need to be used to connect APs to each other, which will result in a higher final deployment cost and a longer time. At the same time, when APs are deployed in some complex environments (such as subways, tunnels, docks, etc.), it is very difficult for APs to connect to the Internet in wired mode. Through WDS technology, wireless connections can be made between APs, which facilitates the deployment of wireless LANs in some complex environments, saves network deployment costs, is easy to expand, and realizes flexible networking.
The advantages of WDS network include:
① Connect two independent LAN segments through a wireless bridge, and provide data transmission between them.
② Low cost and high performance.
③ The scalability is good, and there is no need to lay new wired connections and deploy more APs.
④ Suitable for companies, large warehousing, manufacturing, docks and other fields.
Service VAP: In the traditional WLAN network, the AP is the WLAN service function entity provided for the STA. VAP is a concept virtualized on AP equipment, that is, multiple VAPs can be created on one AP to satisfy the access services of multiple user groups.
WDS VAP: In a WDS network, AP is a functional entity that provides WDS services to neighboring devices. WDS type VAP is divided into AP type VAP and STA type VAP. AP type VAP provides connection function for STA type VAP. As shown in the figure, VAP13 created on AP3 is a STA VAP, and VAP12 created on AP2 is an AP VAP.
Wire virtual link WVL (Wireless Virtual Link): WDS link established between STA-type VAP and AP-type VAP between adjacent APs.
AP working mode: According to the actual location of the AP in the WDS network, the working mode of the AP is divided into root mode, middle mode and leaf mode.
(1) Root mode: AP as the root node is connected to AC through wired connection, and at the same time, AP type VAP is used to establish a wireless virtual link with STA type VAP.
(2) Middle mode: AP as an intermediate node connects with STA type VAP upwards and connects with AP type VAP downwards to STA type VAP.
(3) Leaf mode: AP acts as a leaf node and connects to AP-type VAP with STA-type VAP upwards.
In terms of mode, WDS has three working modes, namely self-learning mode, relay mode and bridge mode.
The self-learning mode is a passive mode, which means it can automatically recognize and accept WDS connections from other APs, but it will not actively connect to surrounding WDS APs. Therefore, this WDS mode can only be used on the main access point router or AP, can only be used on the extended main AP, and cannot be used to extend other APs through WDS.
The relay mode is the WDS mode with the most complete functions. In this mode, the AP can not only realize the expansion of the wireless network range through WDS, but also has the function of the AP to accept the connection of the wireless terminal.
The bridge mode is very similar to the bridge in the wired network. It receives data packets from one end and forwards it to the other end. The WDS bridge mode is basically the same as the relay mode except that it no longer has the AP function at the same time. Therefore, in the WDS bridge mode, the AP no longer accepts the connection of the wireless network terminal, and you cannot search for its existence.
In terms of roles, the members of the WDS network can be divided into main equipment (Main), relay equipment (Rely) and remote equipment (Remote).
The equipment with Internet connection or local area network outlet is usually used as the main equipment to access the backbone network through the Ethernet cable; the equipment in the middle of the network to relay signals is the relay equipment; the edge of the wireless WDS network provides wireless access and sends data to The device forwarded by the master device is the remote base station.
With the replacement of current home-class wireless routers, the price of wireless routers with WDS generally goes down. In this way, wireless users can spend a relatively small amount of money to achieve the purpose of expanding the coverage of the wireless network, effectively increasing the coverage area of the wireless network, and reducing the dead angle of the wireless network signal.
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