ZyXEL B-320 User Guide - Page 33

ZyAIR Wireless LAN Utility its range to notify them to defer their transmission. It also reserves and confirms with the requesting station the time frame for the requested transmission. Stations can send frames smaller than the specified RTS/CTS Threshold directly to the AP without the RTS (Request To Send)/CTS (Clear to Send) handshake. You should only configure RTS/CTS Threshold if the possibility of hidden nodes exists on your network and the "cost" of resending large frames is more than the extra network overhead involved in the RTS (Request To Send)/CTS (Clear to Send) handshake. If the RTS/CTS Threshold value is greater than the Fragmentation Threshold value (see next), then the RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as data frames will be fragmented before they reach RTS/CTS Threshold size. Enabling the RTS Threshold causes redundant network overhead that could negatively affect the throughput performance. 2.7.3 Authentication Type The IEEE 802.11b standard describes a simple authentication method between the wireless clients and AP. Three authentication modes are defined: Auto, Open and Shared. Open authentication mode is implemented for ease-of-use and when security is not an issue. The wireless station and the AP do not share a secret key. Thus the wireless stations can associate with any AP and listen to any data transmitted plaintext. Shared authentication mode involves a shared secret key to authenticate the wireless station to the AP. This requires you to enable a security feature and specify a shared secret key (usually the WEP encryption and WEP key) on both the wireless station and the AP. Auto authentication mode allows the ZyAIR to switch between the open and shared key authentication modes automatically. Use the auto mode if you do not know the authentication mode of the other wireless clients. 2.7.4 Preamble Type A preamble is used to synchronize the transmission timing in your wireless network. There are two preamble modes: Long Preamble and Short Preamble. Short preamble takes less time to process and minimizes overhead, so it should be used in a good wireless network environment when all wireless clients support it. Select Long Preamble if you have a 'noisy' network or are unsure of what preamble mode the access point or the other wireless clients support as all IEEE 802.11b compliant wireless adapters must support long preamble. However, not all wireless adapters support short preamble. Use long preamble if you are unsure what preamble mode the wireless adapters support, to ensure interpretability between the ZyAIR and the access point/wireless stations and to provide more reliable communication in 'noisy' networks. Using the ZyAIR Utility 2-15