802.11: Better, Stronger, Faster--and Greener
September 26, 2008
At Interop last week, experts gathered to discuss how far we've come and where we're headed next with 802.11n. Also on the docket: 802.11s mesh networks and the newer, green-minded standard, 802.11v. ("We have the technology.")
After a full year of draft 802.11n deployment, we've reached the point where all major technical challenges have been resolved and enterprise WLANs run as well-oiled machinesright?
Of course not. Although Wi-Fi products and networks that incorporate them have clearly matured, IEEE 802.11 standards remain a work-in-progress.
Last Friday, I had the privilege of moderating an Interop New York panel entitled "802.11 and Wi-Fi: What's Next and What It Means to the Enterprise." During this session, I asked panelists to describe emerging 802.11 standards, how they might be reflected in enterprise WLAN products, and their potential benefit to applications and users.
Peter Thornycroft, a Technology Analyst at Aruba Networks, kicked things off with an update on IEEE 802.11n progress and differences that might be expected in the final standard.
"New IEEE drafts are being produced pretty regularlywe're up to draft 6.0 now," said Thornycroft. "But what's most important to you and me are Wi-Fi Alliance profiles, because that is what vendors build products to." There are just two 11n Wi-Fi Alliance milestones: Draft-n 2.0 certification launched in June 2007 and "full-n" certification, which Thornycroft expects to start at the end of 2009.
Certification based on the final standard will encompass advanced technologies that were present in earlier draft standards, but not fully-baked. For example, today's Draft-n 2.0 certified APs usually support 3x3 MIMO with two spatial streams, achieving data rates up to 300 Mbps. Products based on the final standard may double that PHY data rate by implementing 4x4 MIMO with four spatial streams. Those products may also incorporate signal processing techniques like transmit beam-forming, space-time block coding, and improved 11a/g coexistence techniques.
"You'll also see the Wi-Fi Alliance split things up into separate profiles for handheld devices, consumer electronics, and the basic profile now used for laptops," said Thornycroft. "New chipsets will have better integration, making it much easier to develop smaller, more powerful devices." Not only will this enable 11n use in consumer electronics, but AP power consumption may dropalthough 4x4 MIMO configurations may still exceed 802.3af PoE budgets.
In short, the final standard will bring feature extensions, but it will not revamp the foundation established by Draft-n 2.0. "Honestly, I don't think [802.11n] ratification will be as big a deal as we once thought it would be," said Thornycroft. "If you've been waiting for the final standard [for stability] you can probably go ahead and deploy Draft-n 2.0 today."
Aerohive Networks vice president of Product Management Adam Conway discussed wireless mesh networks as defined by IEEE 802.11s draft standards. "There are basically two ways of doing wireless backhaul: mesh or tree," said Conway. "802.11s uses a mesh, relaying traffic from fully-interconnected mesh points through one Mesh Portal Point (MPP) connected to Ethernet."
Wireless mesh networks have many potential use cases, ranging from Ad Hoc meshes (i.e., temporary WLANs used by emergency responders and military personnel) to Infrastructure meshes (i.e., permanent WLANs composed of fixed nodes, typically deployed by municipalities, WISPs, or enterprises).
"Is mesh a corner case in the enterprise? Absolutely not," said Conway. "If mesh is easy enough to deploy, everybody will use it in certain locationsfor example, parking lots and older heritage buildings. Most of our customers do use mesh somewhere; the most common place is probably inside stairwells."
Despite the benefits of mesh networking, Conway identified a number of limitations present in the 802.11s mesh architecture. "802.11s does routing at layer two only, using MAC address instead of IP address. It creates a single broadcast domain, and that has significant implications for deployment. Specifically, you can only deploy one MPP per domain and you can only support a single subnet."
802.11s is based on a solid adaptive routing protocol and can work well in smaller networks, said Conway, but large enterprise WLANs may need proprietary mesh solutions (like Aerohive's). "You won't see a lot of 11s inside the enterprise for three reasons. The first is scale: 11s scales up to 32 APs nominally, maybe 16 effectively. The second is inability to handle multiple subnets, and the third is lack of resiliencya single MPP creates a single point of failure that most enterprises would consider unacceptable," he said.
Matthew Gast, author of the popular O'Reilly book 802.11 Wireless Networks: The Definitive Guide and Principal Engineer at Trapeze Networks, shared his insights on IEEE 802.11v wireless network management.
This standard is still in the early stages of development. A first draft emerged in July 2007, and the final 802.11v standard is not expected until March 2010. Gast chairs the Wi-Fi Alliance Wireless Network Management task group responsible for proposing new certification programs that will take advantage of 802.11v.
"Currently, we've broken things down into five broad categories," said Gast. "Power savingto let us create devices that use electrons more effectively. Station managementto enable trouble-shooting, diagnostics, and reporting. Locationingto let us build new services based on where devices actually are. Timingto support applications that require very precise calibration, like wireless audio and factory floor automation. And Coexistencea very important topic, but I have no idea what will develop here."
Enterprises may benefit from 802.11v in a wide variety of ways. For example, 802.11v will let clients conserve power by turning their radios off more frequently and sleeping more soundly. With 802.11v, a snoozing Wi-Fi phone may be able to wake only for incoming SIP messages, while wireless PCs might be awakened for remotely-initiated access or management operations. Such improvements would facilitate "green" offices that use new wireless devices to reduce overall power consumption.
"802.11v is a grab bag of neat ideas," said Gast. But only time will tell how these enhancements will be incorporated into products and applications that benefit enterprise WLANs.
Making the most
Emerging standards like these can be expected to boost performance, expand reach, and increase WLAN flexibility. However, all panelists agreed that many of the most interesting innovations will occur above the network, in the form of new wireless applicationssome of which have not yet been envisioned. 802.11 standards and Wi-Fi-CERTIFIED products give enterprises the ability to construct a pretty robust pipelinenow it's time to fill those pipes with richer applications.
Lisa Phifer owns Core Competence, a consulting firm focused on business use of emerging network and security technologies. She has been involved in the design, implementation, assessment, and testing of NetSec products and services for over 25 years.