Do I Need To Deploy WDS?

Now, with all these point out in the open, is WDS really suitable to your needs?

If you have the need for Wi-Fi saturation coverage of a workplace and especially if you can run an Ethernet cable to each WDS-enabled access point and need to allow people to roam between access points, then WDS is most definitely worth investigating.  If you have no need for roaming users, then a standard Three Channel System as described in the 802.11b and 802.11g article (http://www.quarkit.com.au/content/view/49/49/) should be considered above the WDS system.  If you have the need for high throughput Wi-Fi networking, then WDS is going to REQUIRE a wired backbone.

Coming quickly back to the earlier example of a warehouse using WDS, if you recall the diagram I made in that last article, you can see that were this a warehouse floor where someone needed to roam the entire floor and remain connected, you'd need to have this Wi-Fi device connecting to multiple Wi-Fi APs with different SSIDs, making the list of accepted APs rather insane.  Using WDS will allow you to cut this back to a single SSID on a single channel.  The reason this sort of mesh networking is appropriate in warehouses is because of the havoc the high metal shelving plays with Wi-Fi signals - this will allow you to have a WDS network with an AP in every row and a few other in the open areas, allowing for much, much better coverage than would happen with a standard Three Channel System.

Until more 802.11n devices are available with WDS support, and until 802.11n is available by default in more laptops and PDAs, you can almost ignore this technology for now, unless you need WDS and high throughput and you are in a relatively RF-isolated environment.  If that’s your situation, then you can at least use the Buffalo WZR-G300N device, and possibly others, for 802.11n WDS.

Because of the differences between WDS implementations between vendors, the following information is generally true, but can vary depending on the devices and versions of the firmware that you choose to use.  However generally:

• When configuring a WDS-enabled Wi-Fi network, all of the APs must use the same Wi-Fi channel – preferably 1, 6, or 11.
• All WDS APs must have their SSID set to the same name if using WPA-PSK, however if using WEP (not recommended) the SSIDs may be different.
• All WDS APs must have an IP on the subnet to which the client devices (laptops, PDAs, etc) need to connect.  (If using a WDS network exclusively to act as a point-to-point wireless bridge, it is a good idea to use IPs on a different subnet.)
• If Spanning Tree Protocol support is available, configuring a loop will provide for some redundancy should a WDS AP fail.  This is especially true where there is significant overlap in coverage zones.  If STP is not available, a loop will cause serious networking issues.
• All WDS APs must have the same security settings, including pre-shared key.
• For maximum throughput, all WDS APs should have a wired Ethernet connection to a central switch.  Running a WDS mesh network where the WDS APs connect wirelessly to other WDS APs will roughly halve the throughput of your network.

For more complex mesh networking, a product such as the 3Com 3CRUS2475 – their Unified Gigabit Wireless PoE Switch 24 – can be used.  (http://www.3com.com/products/en_US/detail.jsp?tab=features&pathtype=purchase&date=9-29-2006&sku=3CRUS2475)  This switch allows centralized management of the attached 3Com access points, enabling password changes to be pushed out to all APs simultaneously, as well as taking the processing load off the access points themselves and enabling some load balancing between APs.  Other manufacturers such as Cisco and DLink have similar offerings in this area.  However, don’t expect interoperability between their offerings.