Channels

18, 24, 36, 48 and 54 Mbps.

802.11i, ratified in 2004, defines an enhanced security mechanism based on AES.

802.11n, expected to be ratified in 2009, is backward compatible with 802.11a, b, and g, and will operate at 2.4 GHz and optionally 5 GHz. It can potentially support data rates up to 600 Mbps.

802.11b and 802.11g divide the 2.4 GHz spectrum into 13 channels, beginning with channel 1 and ending with channel 13. The center frequency of channel 1 is 2,412MHz, channel 2 is 2,417MHz, etc. The center frequencies of adjacent channels are 5 MHz apart. The bandwidth of each channel is 20 MHz which means that channels may “overlap.” The commonly-used non-overlapping channels are channels 1, 6, and 13. There is a 14th channel whose center frequency is 12MHz above channel

13.These frequency bands are referred to as channels and stations communicate using a particular channel.

802.11a and 802.11n operate in the 5 GHz range which is divided into a large number of channels. The center frequency of channel 0 is 5,000 MHz, the center frequency of channel 1 is 5,005 MHz. The formula for relating channels (n) to center frequencies in the 5 GHz range is:

Center frequency (MHz) = 5,000 + 5*n, where n = 0, …, 199,

Center frequency (MHz) = 5,000 – 5*(256 – n), where n = 240, …, 255.

Note that channels 240 to 255 range from 4,920 MHz to 4,995 MHz. As with the 2.4 GHz band, each channel is 20 MHz wide. 802.11n allows for “wide” channels – that is, two adjacent 20 Mhz bands (note that the channel numbers of the two adjancent 20 MHz bands are not adjacent) can be used “side-by-side” in order to be backward-compatible with 802.11a, b, and g, or they can be combined into a single 40 MHz channel in “Greenfield” mode.

The actual use of the channels, however, depends on the country. For example,in the USA, the FCC allows channels 1 through 11 in the 2.4 GHz band, whereas most of Europe can use channels 1 through 13. No matter where you are, you can use AirPcap to listen on any supported channel. The regulations for the 5GHz band are much more complex.

Each BSS operates on a particular channel, i.e., the access point and all of the wireless clients within a BSS communicate over a common channel. The same channel may be used by more than one BSS. When this happens, and if the BSSs are within communication range of each other, the different BSSs compete for the bandwidth of the channel, and this can reduce the overall throughput of the interfering BSSs. On the other hand, selecting different channels for nearby access points will mitigate channel

AirPcap User’s Guide

AirPcap Wireless Capture Adapters specifications

Cace Technologies AirPcap Wireless Capture Adapters are essential tools for network professionals aiming to monitor, analyze, and troubleshoot wireless networks. These innovative devices enable packet capture and analysis over 802.11 wireless networks, providing insights that are crucial for maintaining network integrity and performance.

One of the main features of AirPcap adapters is their ability to capture raw 802.11 packets in real time, including management, control, and data frames. This capability allows for a comprehensive view of wireless communications, assisting engineers in identifying issues like signal interference, unauthorized access points, and potential security breaches.

Another significant characteristic is the support for both 802.11a/b/g/n standards. This wide-ranging compatibility ensures that users can effectively analyze traffic across various network types, regardless of the generation of equipment being utilized. Additionally, AirPcap adapters are equipped with advanced features like packet injection, which is beneficial for testing network robustness and security defenses.

The wireless capture adapters are often praised for their seamless integration with popular analysis tools such as Wireshark. This combination provides users with a powerful interface for performing in-depth packet analysis, enabling the decoding of complex protocols and offering visualizations that aid in understanding network behaviors.

For ease of use, AirPcap adapters come equipped with a compact design and user-friendly software. They can be connected to laptops or portable devices, making them ideal for field use. Their portability ensures that field technicians or network analysts can perform assessments in various environments without the need for extensive setup or configurations.

Security is another critical aspect where AirPcap shines. These adapters allow for the capture of encrypted packets, provided the user has the appropriate decryption keys. This feature is particularly valuable for troubleshooting security protocols and ensuring that data transmitted over the network is secure.

In conclusion, Cace Technologies AirPcap Wireless Capture Adapters are versatile and powerful tools for any network engineer or security professional. With their ability to capture and analyze a wide range of wireless traffic, their compatibility with industry-standard tools, and their advanced features, AirPcap adapters are indispensable in today's increasingly wireless world. Whether used for routine monitoring, troubleshooting, or security assessments, these adapters offer a robust solution for wireless network management.