User's Manual

66 Creating WDS links
Using the 5 GHz band for WDS links
When the M220 uses WDS only to extend the network by providing a dedicated link to
another M220 (that is, it does not simultaneously act as an AP for wireless clients), it is
recommended that, whenever possible, the WDS links use 802.11n or 802.11a in the 5 GHz
band. This optimizes throughput and reduces the potential for interference, as follows:
• Most Wi-Fi clients support 802.11b or b/g; therefore, most APs are set to operate in the
2.4 GHz band. This frees the 5 GHz band for other applications such as WDS.
• 802.11a and 802.11n channels in the 5 GHz band are non-overlapping.
• Assuming an optimal implementation, 802.11a supports up to 54 Mbps and 802.11n
supports up to 300 Mbps, providing a fat pipe for traffic exchange.
Configuration considerations
The following guidelines apply when you create a WDS link between two or more M220s:
• The 5 GHz band has a shorter reach when compared to the 2.4 GHz band. This could be
a factor depending on the distance your WDS link span.
• All radios must be set to the same operating frequency and channel. This means that on the
Wireless > Radio page under Channel, you cannot select Auto.
• The Ethernet ports for all M220s must be connected to the same subnet, and each M220
must have a unique IP address.
• If WPA (PSK) security is enabled, the same link name and key must be defined on all
M220s that are linked by the WDS connection.
• IEEE 802.11n uses frame aggregation, whereby multiple frames are combined into one to
reduce overhead and increase throughput. WEP-encrypted frames are not aggregated,
however, so enabling WEP security over WDS will result in reduced throughput.
• Although the M220 can support up to four WDS links, only one wireless link can be
defined between any two M220s.