Louie Wong

IEEE 802.11 WLAN Standards

IEEE 802.11 is a set of standards for wireless network to provide wireless devices with a communication in the 2.4, 3.6 and 5 GHz frequency bands. They are originally developed and maintained by the IEEE (Institute of Electrical and Electronics Engineers) LAN/MAN Standards Committee (LMSC).

The first standard was created by IEEE in 1997 and had been named as 802.11. It uses unregulated radio signaling frequency (2.4 GHz) but only supported up to 2 Mbps maximum network bandwidth. Specific physical layers that enabled three faster radio layers had been defined by subsequent amendments of IEEE 802.11:

802.11b

802.11b was created based on the specification of original 802.11 in July 1999, and it support network bandwidth up to 11 Mbps.

802.11b uses unregulated radio signaling frequency (2.4 GHz) as same as the original 802.11 standard. It provides 3 radio channels. By using this frequency, the manufacturing costs could be lower down. Because of unregulated signal, 802.11b could incur interference from other appliances using the same 2.4 GHz range, such as microwave ovens, cordless phones. However, the interferences can be avoided by installing 802.11b a reasonable distance from other appliances.

• Pros of 802.11b – cost is cheapest; signal range is very good and not easily to be obstructed.
• Cons of 802.11b – maximum speed is still slower; home appliances may interfere on the unregulated frequency band.

802.11a

A second extension to the original 802.11 standard was created and called 802.11a. Due to its higher cost, 802.11a is usually found on business networks whereas 802.11b better serves the home market.

802.11a supports up to 54 Mbps network bandwidth and provides 8 radio channels in the 5 GHz frequency band. Because of this higher frequency, the range of 802.11a networks is also shortened. In addition, the higher frequency also makes the signal of 802.11a to have more difficulty in penetrating walls and other obstacles.

• Pros of 802.11a – faster maximum speed; regulated frequencies can get rid of signal interference from other home appliances.
• Cons of 802.11a – expensive in cost; shorter range signal and more easily to be obstructed.

802.11g

802.11g was created to combine the best of both 802.11a and 802.11b and supports network bandwidth up to 54 Mbps. It uses the 2.4 GHz frequency for wider range. 802.11g is backwards compatible with 802.11b, which means the access point of 802.11g will just work fine with all the wireless network adapters of 802.11b, and vice versa.

• Pros of 802.11g – fast maximum speed; signal range is very good and not easily to be obstructed.
• Cons of 802.11g – cost is higher than 802.11b; other appliances may interfere on the unregulated.

802.11n

802.11n is the newest IEEE standard in the 802.11 family. It improves on 802.11g in the amount of bandwidth by using multiple wireless signals and antennas instead of one. This is a technology called MIMO (multiple-input multiple-output). It will also operate on the 2.4 GHz band. Presently the development of this standard is still in progress. But when this standard is finalized, 802.11n connections will be able to support data rates up to 100 Mbps. 802.11n also offers better range over earlier 802.11 standards due to its increased signal intensity.

• Pros of 802.11g –best signal range and fastest in maximum speed; more ability to resist signal interference from other sources.
• Cons of 802.11g –cost is higher than 802.11g; the use of multiple signals may massively be interfered by nearby 802.11b or 802.11g based networks.

How to protect your wireless network

1. Secure administrative login credentials
   Every router comes with a preconfigured password, and intruders know about this. Thus it is exceedingly easy for them to hop onto the wireless network and gain full control over its administrative permission and wreak possible havoc. If the intruders detect the SSID (Service Set Identifier) of the wireless network is being named as “Linksys”, they can easily make a guess that the default username and password could be “admin” as this Linksys networks’ factory settings. The first task we should do is to change the default login credentials of the router to something else. While setting an administrative password for the router, choose a more complicated password, the best is a combination of letters and numbers.
2. Stop broadcasting the network’s SSID
   The SSID (Service Set Identifier) is a broadcast message that telling every device within range of the wireless network’s presence. If passers-by know what the SSID is, it will be very easy for them to detect the signal of wireless network and get connected to it. Thus stop broadcasting the network’s SSID will help to be invisible to unauthorized users.
3. Enable WEP or WPA encryption
   To prevent unauthorized users from eavesdropping on the wireless network, encryption of wireless data is essentially required. WEP (Wireless Equivalent Privacy) and WPA (Wireless Protected Access or Wi-Fi Protected Access) are ways of forcing authorized users to pass through the authentication by providing login credentials before getting connected to the wireless network. WEP is the most common but it is found to be fundamentally flawed as it can be easily cracked by determined hackers. WEP restricts access by identifying the password and shared key. Unauthorized users who know the WEP key can still hop onto the wireless network. WPA (Wireless Protected Access) is the next generation of encryption and designed to leverage the deficiency of WEP encryption. Recently WPA has been even supplanted by WPA2. WPA and WPA2 replace the WEP encryption with a mechanism called TKIP (Temporal Key Integrity Protocol). This protocol dynamically changes the key to prevent the sort of hacking techniques that used to crack WEP encryption before.
4. Restrict users access based on their MAC address of network devices
   A MAC address (Machine Access Code) consists of a series of unique number that every network device can be identified by. So we can setup our router based on MAC (Media Access Control) addresses to determine certain devices are allowed to connect to the wireless network, and certain MAC addresses that are not listed in a table contained in the router/AP will be banned from accessing the network.
5. Reduce the wireless network transmitter power
   Some routers or access points (AP) allow network administrator to adjust the power of the wireless network transmitter and thus the range of transmission signal is reduced. This practice helps to limit how far outside premises the signal can reach and minimizes the probability that passers-by may detect the wireless network.
6. Always turn on the firewall
   The communications between the wireless network and the rest of the network can be restricted by using firewall or router ACL (Access Control Lists). We can even control the access by wireless devices so that authorized users connected to the wireless network can only surf the Web, or only allowed to access certain folders and applications while connecting the wireless network to the internal network via a web proxy or VPN (Virtual Private Network).
7. Disable remote administration feature
   Most of the routers can be administered remotely through the Internet. We should turn this feature on only if the router lets us define a specific IP addresses or limited range of addresses that are allowed to access the router. If we can’t restrict the range of allowed IP, then anyone could potentially find and access the router from anywhere. As a matter of fact, it is always the best to turn the remote administration feature off.