Cisco SA520-K9 Administration Guide - Page 101

Wireless Configuration for the SA520W Configuring the Radio 3 Advanced Radio Configuration This page is used to specify advanced configuration settings for the radio. STEP 1 Click Wireless > Radio Settings > Advanced Settings. The Advanced Radio Settings window opens. STEP 2 Enter the following information: • Beacon Interval: Beacon frames are transmitted by an access point at regular intervals to announce the existence of the wireless network. Set the interval by entering a value in milliseconds. The default setting is 100, which means that beacon frames are sent every 100 milliseconds (10 seconds). • Dtim Interval: The Delivery Traffic Information Map (DTIM) message is an element that is included in some beacon frames. It indicates the client stations that are currently sleeping in low-power mode and have buffered data on the access point awaiting pickup. Set the interval by entering a value in beacon frames. The default setting is 2, which means that the DTIM message is included in every second beacon frame. • RTS Threshold: Determines the packet size that requires a Request To Send (RTS)/Clear To Send (CTS) handshake before sending. A low threshold setting can be useful in areas where many client devices are associating with the wireless device, or in areas where the clients are far apart and can detect only the access point but not other clients. Although a low threshold value consumes more bandwidth and reduces the throughput of the packet, frequent RTS packets can help the network to recover from interference or collisions. Set the threshold by entering the packet size in bytes. The default value is 2346, which effectively disables RTS. • Fragmentation Threshold: Frame length that requires packets to be broken up (fragmented) into two or more frames. Setting a lower value can reduce collisions because collisions occur more often in the transmission of long frames, which occupy the channel for a longer time. Use a low setting in areas where communication is poor or where there is a great deal of radio interference. Set the threshold by entering the frame length in bytes. The default value is 2346, which effectively disables fragmentation. • Preamble mode: 802.11b requires that a preamble be appended to every frame before it is transmitted through the air. The preamble can be either the traditional long preamble, which requires 192 μs for transmission, or it can be an optional short preamble that requires only 96 μs. The long preamble is needed for compatibility with the legacy 802.11 systems operating at 1 and 2 Mbps. The default is Long. Cisco SA500 Series Security Appliances Administration Guide 101