Virtual Wi-Fi

Meru Networks has announced "virtual ports" for its wireless networks - a development it claims will finally enable Wi-Fi to replace Ethernet by making it as reliable as a switched Ethernet port.

The new fast version of Wi-Fi, 802.11n, can match the performance of Ethernet, but it can still be unpredictable, said Meru's vice president of marketing, Rachna Ahlawat. Virtual ports, introduced to the latest software on Meru's wireless controllers, give each user a dedicated network service, which can be tied to quality of service and delivered data rates.

Laptops and phones connecting to a Meru network with virtual ports will each see a dedicated BSSID or Wi-Fi Mac address, analogous to a wired switch port, said Ahlawat. This will follow the user throughout the network.

"It's like having a wired network port following you, hopping from radio to radio as you move," said Meru's chief architect, Joe Epstein. "One client can't affect the performance of others," added Ahlawat.

"The approach is very interesting," said analyst Craig Mathias of Farpoint Group, "providing greater control over the relationship between the infrastructure and a given client. I'm looking forward to testing it."

The feature is made possible by Meru's existing virtual cell architecture, said Ahlawat. This "virtualises" the Wi-Fi network, so access points do not all have separate identities: the BSSIDs are centralised, and network resources can be pooled for all users. Virtual ports take this further, by partitioning the pooled resources, to deliver service level agreements to individual clients, said Ahlawat.

Most rival wireless network equipment can also set up multiple BSSIDs, sometimes called "virtual APs," for instance to provide multiple wireless networks for guests and contractors on a site. But they cannot offer virtual ports, because the BSSIDs are held on the individual access points, and not centralised and pooled, Epstein said. "In that situation, attempting to assign a BSSID per client would be wrong - the network would rapidly run out of addresses. Without pooling, virtual ports would be the utter worst case of preprovisioning - not a virtualisation solution."

"Aruba, Cisco and others are trying to find ways to optimise a hublike technology," said Epstein, making a comparison with the old-fashioned hubs that shared access to Ethernet networks until they were replaced by switches which give each client its own port. "They make it work as well as a hub can work, but there will still be a difference between that and a switch-like technology."

Virtual ports can't make capacity out of nothing, acknowledged Epstein: they still share the bandwidth of a limited number of channels. But Ethernet switches are also limited by the uplink bandwidth - and the virtual port puts the two technologies on an equal footing: "The reaction of a switch to load is predictable."

The virtual port was designed for fast Wi-Fi in mind, using the IEEE 802.11n standard, but works on the previous 802.11abg standards, and is already available on Meru's 802.11abg products, said Epstein.

Meru launched a new 802.11n AP

SUNNYVALE, Calif., Apr. 21, 2008 – Meru Networks has introduced the AP440, a four-radio IEEE 802.11n wireless access point that provides the data rates and functionality to let enterprises replace aging wired infrastructures with wireless networks without compromising access speed, throughput capacity, security or resiliency.

The AP440 has four radios that can each support the full draft IEEE 802.11n standard, in either the 2.4GHz or the 5GHz band. Meru's "channel blanket" architecture means that all four can be in use at once, though likely set-ups will probably use one radio for monitoring, intrusion detection, and protection from rogue access points.

Each of the AP440's four IEEE 802.11n radios supports access at up to 300 megabits per second (Mbps), for 1.2 gigabit-per-second (Gbps) capacity. Because the four radios work together to provide internal redundancy, load-balancing and security, enterprise users can dramatically reduce the number of access points and additional security sensors they need, realizing significant savings on cabling, connection and deployment/installation costs.

"By 2010, we predict that 79 percent of new connections will be wireless," said Rachna Ahlawat, Meru's vice president of marketing. "Security is no longer the number one concern - it is now reliability, followed by capacity, scalability, security and price."

Although the access point will be announced at next week's Interop conference in Las Vegas, it won't be available until the third quarter of this year. This could be useful in that it may allow electrical power to catch up with it. The current standard for power over Ethernet, IEEE 802.3af, will not deliver enough electrical power to run four Wi-Fi radios, but the next specification, 802.3at, should start to be available in products by then, said Vaduvur Bharghavan, Meru Networks chief technology officer.

The four radios should operate omni-directionally and without interfering with each other, said Bharghavan. With four channels, it will be easier to avoid unexpected interference, such as that from microwave ovens, said Bharghavan. "The best thing is to have a parallel channel available in the same band," he explained, saying traffic can move across right away, whereas in a channel-planning WLAN, such as those of Aruba, Trapeze and Cisco, moving an AP from one channel to another would mean dropping all the clients, and then changing the channel - and then changing channels on neighbouring APs. "If clients need to change channels, we are optimised to do that. It's not been done before."

The access point also includes a USB port, so the user can plug in a Wi-Fi monitoring device, on a few access points, such as the Metageek Wi-Spy spectrum analyzer, which improves on plain Wi-Fi monitoring by spotting other sources of interference such as microwave ovens and Bluetooth. "We have software on the AP that interfaces and pulls spectrum analysis off the Wi-Spy" said Bhargavan. "As spectrum analyzers get more sophisticated, it won't require a hardware upgrade to the AP - you can just plug in a different analyzer."

Meru is also announcing a virtual-reality visualisation tool which can display three-dimensional "heat-maps" of Wi-Fi coverage in a building. It relates access points on different floors, so should give a better indication of coverage, and allows the network manager to move through the building checking on likely coverage from his or her desk. This is an additional extra to Meru's existing management software, and costs $9,995.

The AP440 Access Point is priced at $2,995 and the MC5000 4-Gbps Acceleration Module at $15,000 (U.S. list). Both products will be available in the third quarter of 2008.

More: Meru

The four generations of wireless LAN networking

1st generation: early consumer Wi-Fi equipment, with minimal amounts of security

2nd generation: first release of enterprise-oriented wireless products. Access points still stand alone, but security was improved.

3rd generation: most current enterprise wireless products. Central controllers help regulate AP connections, much improved security, but deployment issues remain: proper layout and channel spacing needed for maximum benefit.

4th generation: All access points share a channel, with a central controller determining which access points communicate with various devices. Denser implementations become possible without risk of co-channel interference.

Fourth-generation APs, currently developed by Meru and Extricom, use a smart, centralized controller to create a large, virtual wireless cell that spans several APs, making the handoff between cells transparent to endpoint devices such as laptops and, ideally, reducing dropped connections as a user moves around a wireless LAN. As far as the device can tell, an entire office is just one large wireless zone (see sidebar for a look at the other wireless generations).

Extricom's APs have much less intelligence than typical offerings. They act similarly to antenna extensions that are intelligently tuned in to the appropriate device by a central switch to which each AP is directly connected. Meru's devices, on the other hand, have more intelligence in the AP, allowing them to communicate to the network on layer 3.

Each company claims its technology is superior in several ways, but King said they were similarly capable for most tasks.

These fourth generation methods also have the benefit of reducing planning complexity -- no more careful spacing of APs at set intervals, overlapping – but not by too much – connectivity zones to provide maximum range and throughput. Instead, these options can pack APs more closely to ensure stronger cover without the fear of radio interference.

But is it time to jump aboard? Maybe, maybe not. The technology is promising, but it is so new that network architects don't understand all its pitfalls.

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