Q1：What is Wireless Access Point? What’s the difference between Wireless Router or Gateway and Access Point?
A1： An access point essentially functions as an extension from an existing wired network to a community of users with wireless laptops and desktop computers. A wireless gateway is an access point with NAT routing and DHCP server. An access point is a wireless gateway without NAT routing and DHCP server. Most homes and small offices use wireless gateways because they need the NAT routing to share Internet connection and DHCP server that simplify network management in the home or office. Most enterprises and large businesses use access points, not gateways, because their wired network (their "backbone") already has Router and DHCP server supplied by an industrial strength router or hub, which might also offers sophisticated firewall and VPN functions. In some cases, access point can be operated in different mode like Ethernet bridges. Then the device will be acting like a Wi-Fi interface card providing host computer WI-Fi connectivity. By supporting multiple client bridge functions, it provides multiple computer access to Wi-Fi networks via Ethernet extension.
Q2： What is SSID?
A2： Service Set Identifier. A unique address that identifies the access point/router that creates the wireless network. You can imagine SSID like the name of the network formed by the specific AP/Router. A unique 32-character network name, or identifier, that differentiates one wireless LAN from another. All access points and clients attempting to connect to a specific WLAN must use the same SSID. The SSID can be any alphanumeric entry up to a maximum of 32 characters. (See ESSID, network name).
Q3：What is WDS?
A3：It stands for Wireless Distribution System, which is a technology that enables access points to communicate with one another in order to extend the range of a wireless network. In some cases, you can imagine WDS as a repeater.
Q4：How many different protocols are defined by IEEE 802.11 committee? Can you summarize the status quo?
802.11a One popular wireless standard operates in the 5 GHz radio band. It offers up to 12 non-overlapping channels (as opposed to three with 802.11b). It uses Orthogonal Frequency Division Multiplexing (OFDM) to offer maximum standardized data rate of 54 Mbps. 802.11b One of the popular 2.4 GHz Wi-Fi standards, it offers only three non-overlapping channels. It uses complementary code keying (CCK) to achieve maximum standardized rate of 11 Mbps per channel. 802.11d 802.11d allows an access point to "describe" allowed configurations to clients to make deployment easier. It’s for simplifying world-wide spectrum management. 802.11e Quality of Service (QoS) enhancements for 802.11 networks. QoS may be critical for new applications, such as voice over 802.11. The Wi-Fi Alliance has released an interim snapshot called Wi-Fi Multimedia (WMM). 802.11f This standard defined an inter-access point protocol. It has not been widely implemented. 802.11g An update that uses the OFDM encoding of 802.11a in the 2.4 GHz band. Considering popularity of 802.11b, 802.11g is backward-compatible with 802.11b and this proved to make it the most successful Wi-Fi technology. If an 802.11b device enters an 802.11b/g environment, all 802.11g devices will use a "protection" mode for coexistence. 802.11h European radio regulations for the 5GHz band require products to have transmission power control (TPC) to limit RF energy and dynamic frequency selection (DFS) to minimize interference with other systems. 802.11h defined these functions to allow use of the 5 GHz band. 802.11i 802.11i offers dramatically improved security. Includes two new encryption algorithms: TKIP (Temporal Key Integrity Protocol), which synchronizes key changes between clients and APs; and CCMP (Counter Mode with CBCMAC Protocol), which is an AES-based system. 802.11j Japan has authorized a slightly different frequency band (4.9 GHz - 5 GHz) for 802.11a-like functionality. 802.11j brings OFDM PHY speeds to the authorized Japanese band. 802.11k 802.11 equipment does not report much about the health and status of the radio link, and network managers have little insight into its performance. This standard will make low-level data available to management systems so that equipment can dynamically change radio channels, power levels, and load balance clients across APs. 802.11n Pending project that will focus on increasing the speed of 802.11 beyond 100 Mbps using multipleinput/multiple output (MIMO) technology. 802.11p Wireless Access in Vehicular Environments (WAVE). Initial focus is on adapting 802.11 technology for use in automotive transponders, such as electronic toll collection. 802.11r Enhancements to roaming performance to enable faster handoff between APs. 802.11s Task group to develop 802.11 mesh networks. 802.11T Group to develop test definitions and methodologies for 802.11 networks. 802.11u Group to develop "interworking" functions with other networks, such as cellular networks. This is related to work in 802.21, but handles changes required by 802.11 to support the 802.21 effort. 802.11v Group to develop wireless management functions. 802.11k will enable monitoring of stations, but not configuration. 802.11v will add the ability to configure stations. 802.11w 802.11 management frames are currently authentication, and can easily be used for nefarious purposes. This group is studying the effort to add the protection of management frames into the standard, which would prevent attacks that depend on unencrypted and unauthenticated management.
Q5： What is WPA and WPA2?
A5： WiFi Protected Access (WPA) is based on draft 3 of the IEEE 802.11i amendment. WPA was designed to be a replacement for WEP networks without requiring hardware replacements, using a subset IEEE 802.11i amendment. It brings the following benefits: 1. Strong cryptography support from the Temporal Key Integrity Protocol (TKIP), based on the RC4 cipher; 2. WPA-Enterprise, a mechanism for network authentication using IEEE 802.1x and a supported EAP type, one of EAP/TLS, TTLS or PEAP; 3. WPA-Personal, a mechanism for using TKIP without IEEE 802.1x authentication by using a shared passphrase, intended for consumer networks. WPA2 is based on the Robust Security Network (RSN) mechanism, which provided support for all of the mechanisms available in WPA, as well as: 1. Strong encryption and authentication support for infrastructure and ad-hoc networks (WPA is limited to infrastructure networks) 2. Reduced overhead in key derivation during the wireless LAN authentication exchange; 3. Support for opportunistic key caching to reduce the overhead in roaming between access points; 4. Support for pre-authentication, where a station completes the IEEE 802.1X authentication exchange before roaming; 5. Support for the CCMP (Counter Mode with Cipher Block Chaining Message Authentication Code Protocol) encryption mechanism based on the Advanced Encryption Standard (AES) cipher as an alternative to the TKIP protocol. WPA2 certification is mandatory for all new equipment certified by the Wi-Fi Alliance, ensuring that any reasonably modern hardware will support both WPA and WPA2.
Q6： What is WEP?
A6： Short for Wired Equivalent Privacy, a security protocol for 802.11 standard. WEP is designed to provide the same level of security as that of a wired network such as Ethernet. Ethernet or other wired network are inherently more secure than WLANs because Ethernet or its like are somewhat protected by the physicalities of their structure, having some or all part of the network inside a building that can be protected from unauthorized access. Wi-Fi and its like, which are over radio waves, do not have the same physical structure and therefore are more vulnerable to tampering. WEP provide better security by encrypting data over radio waves so that it is protected when the packet is being sending over the air. However, it has been found that WEP is not as secure as once believed. WEP is used at the two lowest layers of the OSI model - the data link and physical layers; it therefore does not offer end-to-end security. Most popular WEP standard uses either 64-bit or 128-bit key to encrypt.
Q7： What is the spectrum used by 802.11? Will they pose interference to other device?
A7： Formerly, the term "Wi-Fi" was used only in place of the 2.4GHz 802.11b standard, in the same way that "Ethernet" is used in place of IEEE 802.3. Later, the technology expanded to 802.11g which also uses 2.4GHz and 802.11a uses 5GHz. Other devices also uses 2.4GHz include Bluetooth headset, DECT phone, different flavors of cordless telephone and microwave oven. Theoretically they are all considered as interferences to each other. However, technology advancement has minimized this issue but still you a re advised to use them in close distance.
Q8： What is 802.11? What is Wi-Fi?
A8： 802.11 is a protocol family governed by IEEE, it’s about wireless communication standard by which people can connect their computing devices without the need of wires. Most popular standard of 802.11 families include 802.11b, 802.11g, 802.11a and forthcoming 802.11n. Wi-Fi is short for “Wireless Fidelity” . Wi-Fi Alliance is a non-profit organization promoting the usage of 802.11 technologies. Wi-Fi certification encompasses numerous different standards, including 802.11a, 802.11b, 802.11g, WPA, and more, and equipment must pass compatibility testing to receive the Wi-Fi mark.