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Configuring a Wireless Distribution System (WDS)

With the 3com Office Connect Wireless 11a/b/g Access point

This document explains the WDS (wireless distribution system) features provided by the 3com office connect wireless 11a/b/g access point (3CRWF454A72). These features allow you to build a completely wireless infrastructure because the network equipment no longer has to be connected toa wired LAN. Also, WDS features allow you to create large wireless networks by linking several wireless access points with WDS links. WDS is normally used in large, open areas where pulling wires is cost prohibitive, restricted or physically impossible.

Point to-Point-WDS link

Point to-Multipoint-WDS link

Figure 1. Configurations

Wireless Bridge and Wireless Repeater

As shown infigure 1, WDS can be deployed in several configurations. In this document, we will introduce two basic WDS configurations: a wireless bridge and wireless repeater.

Wireless Bridge

The wireless distribution system shown in figure 2 is often called a “wireless bridge” configuration, because it allows you to connect two LANs at the link layer. In figure 2, the access point (AP) behaves as astandardbridge that forwards traffic between WDS links (links that connect to other AP/wireless bridges) and an Ethernet port. As a standard bridge, the access point learns MAC addresses of up to 64 wireless and/or 128 total wired and wireless network devices, which are connected to their respectiveEthernet ports to limit the amount of data to be forwarded. Only data destined for stations which areknown to reside on the peer ETHERNET link, multicast data or data with unknown destinations need to be forwarded to the peer AP via the WDS link.

Figure 2. Wireless bridge configurations.

If, for example, an 802.3 Ethernet frame is sent from a wired station I (sta1) to sta3 in figure 2, frame translations are required while the frame forwards through the WDS link between AP1 and AP2. When AP1receives the 802.3 frame, the frame is translated to a IEEE 802.11 standard four- address format frame before it is sent to a WDS link. In the four-address format frame, the MAC address of Sta1, MAC address of AP1 MAC address of AP2 and MAC address of Sta3 are all included in the 802.11 frame header, and the frame data is same as the original Ethernet frame .based on information in thisfour-address format frame, AP2 will reconstruct the 802.3 Ethernet frame when the frame is forwarded to LAN2 .if a security algorithm is configured on the Aps,AP1(AP2) will encrypt(decrypt) this four-address format frame before frame forwarding. From Stat3´s point of view, the bridging function is transparent; i.e., the received frame is frame is the same as if Sta1 and Sta3 resided on the same LAN.Figure 3. Wireless Repeater Configurations

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Wireless Repeater

In figure 3, AP2 is used to extend the range of the wireless infrastructure by forwarding traffic between associated wireless stations and another repeater or AP connected to the wired LAN. Note that the local Ethernet traffic is not forwarded in this mode. Traffic between Sta3 and Sta4 is not forwarded across the WDS link, noris traffic between Sta5 and Sta6. As with a wireless bridge mode, Aps operating in wireless repeater mode need to translate frames into different frame formats when forwarding frames between wireless connections and WDS links; the 802.11 three-address frame format is used on WDS links connected to other access points. Encryption/decryption algorithms are also invoked if the AP is configured to besecure.

The Office Connect Wireless 11a/b/g Access Point can function as a wireless repeater or wireless bridge if WDS links are configured between the connected AP pairs appropriately.

Configuring WDS links on 3com Office Connect Wireless11a/b/g Access Points

A WDS link is defined as the MAC address pair of the connected APs. To create a WDS link between two Office Connect Wireless...