ZyXEL G-160 User Guide - Page 27

ZyAIR G-160 User's Guide 2.1.11 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 stations 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 stations 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. The ZyAIR and the access point MUST use the same preamble mode in order to communicate. 2.1.12 IEEE 802.1x The IEEE 802.1x standard outlines enhanced security methods for both the authentication of wireless stations and encryption key management. Authentication can be done using an external RADIUS server. EAP Authentication EAP (Extensible Authentication Protocol) is an authentication protocol that runs on top of the IEEE802.1x transport mechanism in order to support multiple types of user authentication. By using EAP to interact with an EAP-compatible RADIUS server, an access point helps a wireless station and a RADIUS server perform authentication. The type of authentication you use depends on the RADIUS server and an intermediary AP(s) that supports IEEE802.1x. The ZyAIR supports EAP-TLS, EAP-TTLS, EAP-PEAP and LEAP. Refer to the Types of EAP Authentication appendix for descriptions. For EAP-TLS and EAP-TTLS authentication types, you must first have a wired connection to the network and obtain the certificate(s) from a certificate authority (CA). A certificate (also called digital IDs) can be used to authenticate users and a CA issues certificates and guarantees the identity of each certificate owner. 2.1.13 WPA Wi-Fi Protected Access (WPA) is a subset of the IEEE 802.11i security specification draft. Key differences between WPA and WEP are user authentication and improved data encryption. User Authentication WPA applies IEEE 802.1x and Extensible Authentication Protocol (EAP) to authenticate wireless stations using an external RADIUS database. Therefore, if you don't have an external RADIUS server you should use WPA-PSK (WPA -Pre-Shared Key) that only requires a single (identical) password entered into each access point, wireless gateway and wireless station. As long as the passwords match, a station will be granted access to a WLAN. Using the ZyAIR Utility 2-7