Take Advantage of Wireless Power
One of the primary advantages of a wireless network is the capability to add another computer more easily than on a wired network. And chances are, those added gadgets are some of the more sophisticated tablet PCs, smartphones, netbooks and notebooks.
The good news: These diverse devices are ushering in a new world of productivity enhancement, not only for road warriors but also for workers who spend their days inside offices. The bad news: The multitude of devices in use within organizations is putting a lot more pressure on the IT managers responsible for network performance and security.
Fortunately, IT shops are getting help from new standards and technologies. For example, upgrading to 802.11n wireless connectivity is truly a no-brainer. Why? Compared with predecessors 802.11b, g and a, 802.11n offers far superior speed, range, capacity and compatibility.
Wireless Takes Flight
A recent report from the Dell’Oro Group, specialists in networking and telecommunications, puts numbers to some of the excitement around wireless. Its research shows that the worldwide wireless LAN (WLAN) market grew 25 percent in 2010, to more than $5 billion.
It also found that enterprise WLAN deployments grew at one of the fastest rates in years, to more than $2 billion. That represents seven straight quarters of revenue growth for the enterprise sector alone, according to Loren Shalinsky, a senior analyst for wireless LAN at Dell’Oro.
Enterprise WLANs are getting a boost from the IEEE 802.11n wireless networking standard. Now being widely adopted by businesses, 802.11n ranks as the newest and highest performing iteration in this important family of wireless LAN protocols.
“Wired connections have become the secondary way to access enterprise networks, and 802.11n is what really triggered Wi-Fi becoming the primary choice,” says David Callisch, vice president of marketing for Ruckus Wireless.
What makes 802.11n so effective? There’s no denying that speed is a big factor. The latest specifications achieve theoretical throughput rates of 600 megabits per second, which now puts WLANs in the same class as standard 100-BaseT wiring. Long gone are the days when wireless networks topped out at 2Mbps and organizations considered wireless an afterthought to wired networks.
Higher performance is always a headline grabber, but that’s only part of the 802.11n story. The spec also includes multiple input, multiple output (MIMO), which allows multiple streams of data and sophisticated signal-processing techniques to process more bits through the same amount of space.
Another important 802.11n development is the ability to use 40-megahertz communications channels, doubling the 20MHz bandwidth available under the standard’s previous iterations. This is important because organizations can now use two adjacent channels as if they were one larger channel to double the theoretical maximum speeds available to each user.
Note that channel doubling runs into some practical limitations that require network administrators to limit the number of users who can simultaneously work at these theoretical speeds. But that doesn’t detract from the essential fact: Administrators now have many more tools for squeezing impressive performance out of today’s wireless networks.
Low cost is another reason products based on 802.11n are attractive. “The price differential between 802.11n products and ones using the earlier 802.11g standard are such that with ‘n’ you are getting roughly six times the raw performance but not paying anywhere near six times the price,” says Craig Mathias, principal with the wireless consulting firm Farpoint Group.
Get the Most Out of 802.11n
The latest version of 802.11 may be a leap forward, but like any standard, it doesn’t guarantee the highest level of performance at all times. In part, that’s because individual manufacturers interpret the specification differently, and organizations implement 802.11n products differently.
The first factor to keep in mind is that not all 802.11n devices are alike. Some access points, for example, may use a single antenna, while competing products use multiple antennae.
This is especially important for organizations that want to get the most out of the new MIMO capabilities: Devices need multiple antennae to take advantage of multiple data streams. Multiple antennae not only offer options for higher performance, they help minimize noise and interference problems that degrade the experience of business users.
Manufacturers are building on 802.11n benefits with innovative antenna designs to boost performance and reliability. For example, Ruckus uses high-gain antenna arrays to optimize the signals that pass between access points and mobile computers. “When the client device talks back to the access point, we can constantly adjust the signal so it’s always getting the most from the Wi-Fi connection,” Callisch says.
Implementation Issues
Network administrators also need to understand some important 802.11n nomenclature.
For example, manufacturers may describe an access points as being 2x2:2 or 3x3:3. At a minimum, in-building access points should be 2x2:2 with dual radios (2.4GHz and 5GHz bands, usually called the b or b/g and a bands) to obtain the advantages of 802.11n.
Dual data streams and 2x2 antennae deliver the high bandwidth of 802.11n. And dual radios will let network managers pack more users into a smaller space by making use of more radio-frequency spectrum.
Adding data streams speeds data processing, delivering better throughput. A device advertised as 3x3 will generally offer users a better experience than a 2x2 device. The 2x3:2 or 3x3:2 devices also offer end users a better overall experience.
Both 3x3:2 and 3x3:3 devices are common. The 3x3:2 device is limited to about 130Mbps performance in normal channels, while the 3x3:3 device can reach speeds up to 195Mbps in normal channels. For planning purposes, network managers should consider 130Mbps the maximum end-user speed that they will be able to deliver for the next five years.
The theoretical maximum 802.11n performance speed of 600Mbps may never be available to typical end users because it requires a 4x4:4 configuration and doublewide 40MHz channels. That’s more antennae, more radio power consumption and more CPU requirements than a typical notebook can achieve today.
An 802.11n device with only a single data stream — even if it is a 3x3 device — won’t be much faster than a typical 802.11g device.
Remember that for end users to see any benefit, the 802.11n clients will need to support multiple data streams as well. For the moment, most notebooks are limited to a maximum of two data streams.
This means that buying 3x3:3 devices may help future-proof a network, but they will not provide users with better performance than 3x3:2 devices because current notebooks are able to handle two data streams at most. If the manufacturer offers both, specify 3x3:3 only if the price difference is negligible.
When it comes to configuring the wide channels possible with 802.11n, network administrators will need to do some trial and error. Most managers stick with 20MHz channels in the 2.4-gigahertz band, sometimes called the 802.11b/g band. Because there are only three non-overlapping 20MHz channels, there’s only one 40MHz channel available.
When laying out a building network with multiple access points, many organizations keep the 2.4GHz band populated as 20MHz channels 1, 6 and 11. This is because access points and clients will interfere with each other if they are all crowded into the same single 40MHz channel. Besides the shortage of channels, there are other reasons to stay away from 40MHz in the 2.4GHz band.
Here’s why: 802.11n has a variety of protection mechanisms, including an aversion to any non-802.11n devices on the network. If an older 20MHz device appears in operation, then 802.11n devices will fall back to 20MHz channels.
The 5GHz band, sometimes referred to as the 802.11a band, has a much larger allocation of channels. The channel count varies because additional channels were added to the 5GHz band a few years ago. Only devices that have Dynamic Frequency Selection (DFS) support (required after 2007 to avoid interference with radar) are allowed to use these new channels.
Network managers still have to worry about older gear operating in the 5GHz band and reducing overall performance by causing 802.11n protection and noninterference features to kick in. Because there are more channels to play with and network design should call for fewer devices per access point, these effects can be minimized.
Also, consider the existing wired network infrastructure. To fully integrate 802.11n into “copper” networks, upgrade wired-to-wireless links so they support Gigabit Ethernet.
How to Gain Control
Ramped-up data transmission rates aren’t the only news in wireless networks. Centralized wireless LAN controllers also help network administrations do their jobs by letting managers adjust access point configurations and fine-tune performance from a central location.
“The controller executes policies that impact class of service, quality of service, security and other areas,” Mathias says. “The management capability resides entirely within the controller.”
Controllers can also help managers dynamically load-balance access points as conditions change, according to new guidance from wireless networking manufacturer NETGEAR. For example, a threshold may be set so that once an access point client reaches 20 percent of load, some users will be passed off to another access point.
WLAN controllers are also able to graphically represent wireless layouts and include information about each device’s specific location and performance level. The graphical consoles include utilities for making necessary changes when impending problems surface.
Security Grows in Importance
As organizations rely more heavily on wireless networks, larger volumes of sensitive enterprise data flow across the airwaves. To protect these important assets, network administrators can create virtual LANs, or VLANs, which restrict access to applications and data based on users’ security profiles. Alternately, IT managers may dedicate a wireless LAN controller for this purpose and use it to divert guest user traffic to a secure location outside the organization’s firewall.
In addition, Aruba Networks offers its policy enforcement firewall running on a WLAN controller to help administrators differentiate among employees and guests using the network. “I can also differentiate between different types of devices the user has and apply security policies based on that,” says Ozer Dondurmacioglu, Aruba’s product marketing manager for wireless LAN.
The technology can also limit an individual user’s network access to business hours only or make a set amount of bandwidth available for each device, Dondurmacioglu adds.
Other important security controls include engaging the encryption and authentication capabilities that come standard with 802.11n devices. This includes IEEE-standard Wi-Fi Protected Access 2 (WPA2). A wireless-N network providing WPA2 mixed mode is flexible enough to connect older devices with WPA+TKIP automatically when they can’t support WPA2+AES, NETGEAR points out.
