What you need to know about 802.11n

Though the 802.11n standard has yet to be ratified by the Institute of Electrical and Electronics Engineers (IEEE), industry experts say corporate wireless administrators should consider upgrading to n.

Wireless local-area networking is the fastest growing market within networking, said Maryam Zand, global mobility product manager for Hewlett-Packard Co.’s ProCurve Networking division.

“We see higher and higher integration of mobile devices into wireless LAN networks. Customers are expecting the same experience that they have at home…The growth of wireless LAN networks is expected to be exponential as customers deploy and adopt 802.11n.”

802.11n offers higher throughput, larger coverage areas and is better at avoiding interference and obstacles, said Mark Tauschek, senior research analyst at London, Ont.-based Info-Tech Research Group. “If you are in the position where you are doing a refresh anyway, you should absolutely go with n, or at least consider going with n,” he said.

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Cautious about 802.11n

The draft status of 11n shouldn’t scare enterprises away.

“The draft is in such a place right now that there will not be any hardware changes,” he said. “When the standard is finalized and ratified, there may be firmware and software updates that have to be applied, but it will not change the hardware. So you know you are safe if you implement 802.11n based on the draft today.”

The transition towards 11n from the enterprise space is driven largely by refresh cycles, said Chris Kozup, manager of market management for mobility solutions at Cisco Systems Inc. of San Jose, Calif. “Analysts are predicting within three to four year window, you’ll see a complete replacement of available technology on the market with 11n being the dominant technology.”

He added 802.11n comes in handy when you’re using your wireless network for more than one application or service.

“That also typically tends to guide them to 11n, because 11n provides around six times the throughput and increased reliability and predictability of existing a/b/g networks,” said Kozup.

What to think about when upgrading

While moving from a b/g network to n is “not terribly challenging,” enterprises that simply replace the access points [APs] in their current locations may experience too much coverage and end up turning down the power output on their NAPs, said Tauschek.

“There are other challenges on the back end, not so much with the wireless component itself, but on your network’s ability to support that additional bandwidth, for instance. At some point, your wireless access points are going to plug into your wired network and your wired network needs to be able to support GB to the access points. So if you have a 10/100 wired network, you’re not going to get full value for your wireless APs. They just won’t support the throughput required,” he said.

He added power over Ethernet (PoE) may not provide enough electricity to APs.

“They’re getting around that by scaling back the power. Cisco has introduced a proprietary [PoE] standard and a new standard is in the works, but it’s something you want to think about. Can my current [PoE] infrastructure support these APs?”

The trade off is either decrease the performance of the access point or increase the power of delivery, said Kozup. “We realized that customers that are deploying 802.11n are doing so because they typically want the performance…we looked at ways to resolve the issue around power and essentially developed a power scheme called Enhanced Power over Ethernet, which basically builds on the existing 802.3af standard,” he explained.

Cisco Discovery Protocol (CDP), which shipped in November 2007, allows the access points to request additional power from the switch port, said Kozup.

“You could make the argument that this is a proprietary solution in that it does require [CDP] on the access point side and on the switch port side and that is typically something that is only supported in Cisco products,” he said. “The reason we delivered this wasn’t so much to come out with a different standard. Cisco will continue to support the development of the next-gen Power over Ethernet standard, which is 802.3at…but what we realized is that we really needed to solve the problems that our customers are having in terms of deployment issues today.”

APs can double as radar detectors

One key concern in deploying 11n, according to Kozup, surrounds the use of the 5GHz frequency. “There’s an FCC regulation that’s called Dynamic Frequency Selection, or DFS, that basically requires the access point to be able to detect the use of military radar in those frequencies. So if a radar signal is detected, the access point can effectively stop transmission on a certain subset of that spectrum, freeing it up for government use.”

DFS creates a problem for vendors who don’t support that feature, said Kozup. “They are effectively handicapped and can only use a portion of that 5GHz frequency…because they do not support this DFS capability, and by law, therefore, they cannot use about 50 per cent of the available spectrum. So the products they are delivering to market really are operating in some respects at half the performance that a Cisco solution is offering.” According to Kozup, expanded bands within the 5GHz frequency are typically used by government military systems in several countries, including Canada.

Another concern is bottlenecks and choke points.

“You need to plan your network such that you don’t create any bottlenecks at any point on the network,” said Zand. A distributed network allows you to scale your network for more users, and you get better coverage that way, she said. “You get the promise that 802.11n is offering.”

But don’t abandon your wired system just yet.

“Even though we’re getting to the point with n where you get actual, practical throughput beyond 100Mbps, there are still applications and certain verticals where demand might be higher for throughput,” said Tauschek. Examples include engineering firms with multi-gigabyte CAD files, large MRI images and CT scans in healthcare and massive video files in the media industry.

Certain applications rely on wired networks, said Zand, pointing to ProCurve’s engineering team. “Each one of them has a 2GB drop to their desk. They need that because they are sharing libraries of design with virtual teams around the world…Time is very important and critical. For those applications, they are hooked to the network.”