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Let's consider an alternate ending to Lesson #4. You need wireless access across an entire floor of your building, and a Wi-Fi vendor with shiny white tasseled loafers planted on your desk says he has just the solution: a single16-radio access point that will provide coverage across the whole floor and will save you a bundle in installation costs. How can you go wrong? Think of the cost savings: only one access point to buy, only one access point to wire.
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #5: eggs break - don't put them all in one access point.
What appears alluring at first glance is really false economy. One single failure and there's nothing between you and a totally dead network - you'll have lost the entire floor. A 16-radio access point on a single cable sounds cool but it only gives you coverage – not capacity (you'll need a lot more radios, cables, and switch ports for that. And it offers no redundancy against failures like a dead CPU or memory.How about just throwing in a second 16-radio access point for redundancy? Even if you could align it to deliver the same coverage pattern, your hardware costs would be blown sky high. And if you're using 802.11n, you’ll further drain the bank by needing additional expensive power supplies and even more cables and ports.
With a multi-access point, multi-channel design, any coverage gap created by the loss of a single access point is mitigated by nearby access points. Load balancing handles high density scenarios while airtime fairness handles different mixes of 80211a/b/g/n clients. And using separate access points allows you to cover rooms and labs and lathe walls and metal-foil wall paper that can't be penetrated from outside - even by a single, centrally-located 16-radio array.
The question to ask yourself is what is the cost of a failure? How much will you lose if the entire office wireless network goes down for a day? Or students can’t access the Internet? Or a trade show network stops running? For most users, the cost of putting all of your eggs in one access point is too high.
You've now discovered why no major wireless LAN vendors pack so many radios into a single access point. It's false economy because it puts your business at risk should a failure occur.
And as far as cost differences, they've all but evaporated with Aruba's newest 802.11n access points. You don't need to take my word for it - Gartner's 2009 Wireless LAN Infrastructure Magic Quadrant spells it out in black and white.
If you'd like to get the whole picture on Wi-Fi architecture you've only to download our free white paper, WLAN RF Architecture Primer. And leave it to someone else to relearn the lessons of Wi-Fi.
You've invited Wi-Fi vendors to your facility to discuss a new Wi-Fi project. You need wireless access across an entire floor of your building which includes open plan seating, conference rooms, and executive offices. This will be the primary form of network access and it needs to work. All the time.
It's late afternoon. A Wi-Fi vendor sits across from you in his white suit and black shirt, the very model of semi-neo-avant garde stylin. His shiny white tasseled loafers are firmly planted on the corner of your desk. He looks you straight in the eyes and says that his access point transmits radio signals farther than anyone else's. "It uses special technology. Yes, it's expensive, but by packing sixteen super duper radios in one unit you'll save a bundle because you only need one access point to cover the entire floor." Wow! How can you go wrong?
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #4: we all live by the same laws of physics, and no Wi-Fi vendor has yet bent them to their will.
The maximum output of a radio at any given frequency is dictated by local regulatory agencies. In most countries 100 milliWatts is the upper limit of what an indoor access point is permitted to output. Regardless of vendor and irrespective of Wi-Fi chip vendor - Atheros, Broadcom, Intel, etc. There is a level playing field when it comes to building radios.
What vendors can do is twiddle with antennas, using directional antennas to focus the allowed radio energy into more well defined beams. And, indeed, doing so can project radio signals longer distances.
The issue is that Wi-Fi networks are bidirectional - there's something on the receiving end of those directional antennas. Low power clients like iPhones and netbooks aren't equipped with directional antennas, much less ones that are easily focused on access points. They may be able to hear distant access points but the access points may be unable to hear them - even if directional antennas are used - because they don' use high power radios.
Additionally,as we learned in Lesson #3, bit rate is inversely proportional to range. In a shared medium like 802.11 where only one device transmits at any one time, lower data rates mean less available air-time for data on that entire 802.11 channel. So even if an access point and its clients can communicate, the throughput from the clients to the access point will be relatively low. Not good for voice. Not good for video. Not good for you.
You don't get something for nothing, but you can find yourself with nothing from something. The Wi-Fi standards anticipated the use of multiple access points, and that's how clients are designed to work. Pushing the limits of how far a Wi-Fi signal can be made to propagate has heuristic value, but when it comes to real-world deployments it can jeopardize the functionality and reliability of your network.
It's best just to tell the vendor to take his shoes off your desk and sell his wares elsewhere - you're having none of it.
If you'd like to get the whole picture on Wi-Fi architecture you've only to download our free white paper, WLAN RF Architecture Primer. And leave it to someone else to relearn the lessons of Wi-Fi.
You're excited - the two bids you were expecting for your new Wi-Fi network have just arrived. You rip open the envelopes and then stare in disbelief.
The first bid - the low bid - includes fewer than 100 access points and a note stating that the access points are specially designed to operate at full power at all times so fewer are required. The second bid includes 135 access points and a note about meeting bandwidth capacity requirements and providing resiliency in the event of failure. Both vendors had the same set of plans to review, both did a walk-through of the facility. How could their bids be so different?
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #3: wireless coverage ≠ wireless capacity. Designing for coverage means providing a discernible Wi-Fi signal everywhere without regard for network speed. The access points on these networks are typically run at full output power so the signal coverage is max'd out. They're also spaced with minimal or no overlapping coverage. As a result fewer access points are required.
The downsides of designing for coverage? Many. Consider these two:
- Bit rate: There is an inverse relationship between bit rate and range. The farther away a Wi-Fi device moves from an access point, the lower the bit rate. Wi-Fi devices operating at the fringe of the coverage area will be very slow indeed. Too slow for voice, streaming video, electronic white boarding, and many other applications;
- Failure happens - but this design can't deal with it. If an access point fails, nearby access points can't increase their output power to fill in the coverage gaps.
Designing for coverage is okay if consistent network performance and resiliency are unimportant. Otherwise it should be avoided.
In networks that are designed for capacity, the required bandwidth is available throughout the coverage area. Application performance will therefore be universally uniform.
Planning for capacity requires more access points because the distance to laptops, iPhones and other clients needs to be more limited (remember rate vs. range) for robust, high-speed operation. They're also needed to ensure adequate load balancing, a feature especially important in areas with densely packed clients such as classrooms, lecture halls, and trading floors. The benefits far, far outweigh the cost - you end up with a resilient network on which you can consistently depend for years of service.
Some vendors play on customers' lack of familiarity with the difference between coverage and capacity. When it comes to reviewing bids and proposals, take note of differences in the number of access points and claims about "unique" features affecting coverage. If you fall for the coverage
If you'd like to get the whole picture on Wi-Fi architecture you've only to download our free white paper, WLAN RF Architecture Primer. And leave it to someone else to relearn the lessons of Wi-Fi.
One the reasons for creating technical standards is to ensure interoperability between devices that need to work together. In the Wi-Fi world, the 802.11 standards serve this purpose, and encompass a very extensive set of guidelines that manufacturers of infrastructure and devices must follow to create a cohesive wireless system. Why then do we encounter situations in which Wi-Fi infrastructure is incompatible with Wi-Fi devices?
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #2: not all Wi-Fi networks are standards based. Some use proprietary technology that is not compatible with the way other Wi-Fi device manufacturers have designed their products.
Take, for example, Glenelg Country School and Frances Xavier Warde School, both of which experienced dropped connections with wireless classroom multimedia projectors. At Raytown C-2 School District radio interference affected laptops on rolling computer carts, while at Prairie Cardiovascular Consultants interference was so bad that it affected both office and clinical operations. Others have reported issues with different models of PCs or Apple Macintosh computers and iPhones.
What's interesting about these cases is that the problems were traced to one common source: the wireless LAN infrastructure. Once the infrastructure was upgraded - in these cases to Aruba wireless LANs - the problems went away.
All of these sites had used a non-standard, proprietary single-channel wireless LAN architecture. There are only two companies in the industry that make such systems, and both are small niche players with shrinking market share. So why would anyone buy such non-standard products in the first place?
Simple - product differentiation can be very alluring. It offers the opportunity for the adventurous to tout themselves as early adopters of what they hope will be "the next big thing." Wanting to be the first to use a new Apple iPad, Alienware laptop, or Google Nexus One makes perfect sense. These products embody innovative designs that redefine their markets. But they're also designed to work with existing networking infrastructure like 802.11 Wi-Fi - that they didn't redefine.
Where you run into serious trouble is deploying non-standards based infrastructure. That's akin to
being the first to try a 156 Volt, 76 Hz electrical system in your house. Some devices might work, but you run the very considerable risk that others will crash and burn.
And that's what happened to the single channel wireless LAN customers. The reason single channel architecture hasn't caught on isn't because it's a secret waiting to be discovered. It's because there's a secret to what makes it run, and therefore interoperability is not assured.
When it comes to living on the bleeding edge of technology, consider the importance of interoperability. If a new technology has to be seamlessly integrated with other existing devices - as is the case with Wi-Fi networks and devices - then using a non-standards based product is just asking for trouble.
If you'd like to get the whole picture on Wi-Fi architecture you've only to download our free white paper, WLAN RF Architecture Primer. And leave it to someone else to relearn the lessons of Wi-Fi.
You've invested thousands - tens of thousands - in new educational software, a fleet of new Wi-Fi enabled laptops, and even computer carts to chauffeur computers between classrooms. But when the students fire up the machines and try to access the shiny new instructional video you're trying to stream wirelessly, they get nothing. Nothing but static. Or jitter. Or dropouts. What went wrong?
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #1: not all Wi-Fi networks are created equal. They all have access points, and they may even be Wi-Fi Alliance certified. But the similarity ends there.
Streaming real-time video is a demanding Wi-Fi application that requires additional processing above and beyond the Wi-Fi standard. The main technology enablers for video over Wi-Fi are adequate bandwidth, quality of service (QoS), and multicast support.
While 802.11n - the newest high-speed Wi-Fi technology - provides a significant bandwidth boost, RF management algorithms are important to ensure continuous, high-rate coverage. These algorithms must include control of the access points and the laptops (clients) - a feature provided by Aruba's Adaptive Radio Management technology - to automatically calculate the optimum channel and transmit power assignments, move clients to the most appropriate access point, and optimize the network’s use of available radio spectrum. This function is especially important for mobile clients - like iPhones - and in the presence of densely deployed clients such as you would find in classrooms and lecture halls.
QoS for video uses the same mechanisms as for voice, however, the bandwidth requirements of video applications vary widely. It is therefore important that any content that requires special handling be correctly flagged. Aruba's integrated stateful firewall does just that.
Since video can account for a large percentage of network bandwidth, determining when to broadcast to multiple clients - multicast streaming - is essential. Here again, Aruba incorporates technology to monitor multicast group members, and only delivers multicast streams to access points whose clients require it.
If you'd like to get the whole picture on video over Wi-Fi you've only to download our free white paper, I Can See Clearly Now. And leave it to someone else to relearn the lessons of Wi-Fi.
One of the challenges of distance learning is how to replicate the "campus experience" for remote students. Doing so encourages collaboration with other students, and improves study opportunities, by leveraging the same electronic learning applications, library reference materials, and server resources as campus students enjoy.
It also builds school loyalty because if these services remain in place post graduation, it improves the chances of continued participation once students become alumni.
Providing secure access to your school's electronic learning resources is a challenge. Open access or password-controlled access won't protect against network attacks, password-sharing, or excessive bandwidth consumption by mischievous students.
A secure virtual private network (VPN) requires your IT staff to load and manage client software on every device a student might wish to use. This is an on-going burden because incompatibilities may be introduced as students upgrade operating systems or other applications on their computers.
Virtual Branching Networking (VBN) solves distance learning connectivity and security issues. Using a small, very inexpensive device called a Remote Access Point (RAP), VBN enables remote students to connect securely to your data network. RAPs enable students to use any IP-based devices with an Ethernet port or W-Fi - MacBooks, iPhones, iTouches, iPads, PCs, VoIP phones, printers - without loading any software clients.
A built-in firewall strictly enforces access policies set by your IT staff, and can even control how much bandwidth a student uses. All access policies are centrally managed and then pushed over the network to the RAPs. The same is true of software updates: they're pushed automatically to every RAP in the field.
New RAPs are shipped unconfigured. To connect one to your network the student pushes a button on the front of the unit and then enters the IP address of your data center.
A RAP controller in your data center then exchanges security certificates with the student's RAP and voila, the student is on-line. No IT staff involvement is required for this process to occur, meaning that it's possible to economically support a very large distance learning program without adding IT staff.
Since RAPs are shipped unconfigured, they can be sold or rented to students through your bookstore or by a third party with zero-touch involvement by your IT staff. If a student leaves your distance learning program, or fails to pay tuition, a simple change in the access policy will completely disable the RAP.
Alternately, when a student graduates the RAP settings can be changed to disable distance learning and enable Internet access using your alumni site as the home page.
VBN has been field-proven in enterprise teleworker deployments around the world, and is the ideal solution for distance learning applications of any size. To find out more please visit our Web site.
It was the best of Wi-Fi, it was the worst of Wi-Fi, it was the age of access, it was the age of stagnation, it was the epoch of mobility, it was the epoch isolation, it was the season of enlightenment, it was the season of bewilderment, it was the spring of tranquility, it was the winter of frustration, we had everything that was promised, we had nothing but words, we were all going direct to the Internet, we were all going nowhere (and slowly at that) — in short, the Aruba 802.11n wireless LAN at Educause Denver delivered the goods, the Xirrus arrays at Interop New York....well, read on.
The Educause 802.11n Wi-Fi network ran flawlessly and was smokin’ hot: 800 simultaneous users, 50% 802.11n clients, 50Mpbs delivered in client speed tests.
If you want to know what happened in New York see Jim Frey’s Network World posting, "Internet = InterNOT @ Interop."
If it looks like a skeet, and it flies like a skeet, and its connectivity is comparable to a skeet, then treat it like a skeet.
Brocade yesterday announced that it will be reselling a new line of wireless LANs. Foundry (now part of Brocade) has been reselling wireless LANs for some time, so aside from a new OEM supplier where is the news?
Well, it turns out that Brocade didn't just select another vendor. It selected a completely different wireless LAN technology.
For roughly three years Foundry has been reselling Meru's proprietary single-channel / virtual-cell architecture. Meru has long made what we consider to be outrageous claims about its proprietary technology - airtime fairness, high throughput, fewer required access points, and so on. The Foundry team has had years of experience understanding the real strengths and weaknesses of Meru's single-channel networks, their 802.11n technology, their network management. They have deployed wireless LANs with virtual-cell technology across a range of customer types - education, healthcare, business. They, better than any single customer, knew the strengths and weaknesses of the vendor and the technology.
The upshot of yesterday’s news? Single-channel wireless LAN technology was rejected by the customer that knew it best.
Changing an OEM supplier is a decision that is never made lightly because it profoundly impacts the customer base and the company's reputation. Customers who invested in the single-channel / virtual-cell architecture are surely asking why Brocade abandoned a network that was supposed to be so innovative. What are the limitations and deficiencies that caused Brocade to change the underlying architecture as well as the vendor? The Brocade announcement is a watershed because it is a repudiation of the proprietary single-channel architecture. It also serves as a cautionary tale that vendor claims that sound too good to be true generally are.
The technology shift from single-channel to a new architecture will likely be very disruptive to Brocade’s customers. Brocade has already removed the Meru-based products from its Web site, and support-related issues will no doubt be unpleasant. But all is not lost.
Aruba wants Brocade’s wireless LAN customers as our customers, and we have a generous trade-in program to ease the pain of the transition to our award-winning adaptive 802.11n networks. Switching to Aruba will be a real step-up for those customers because we have field-proven adaptive wireless management, wireless infrastructure control, remote networking, wireless intrusion detection, policy-based firewalling, and client-to-core security that were never before available from Meru. Our AirWave Wireless Management Suite will manage their legacy Brocade/Meru network from the same console from which they will manage their brand spanking new Aruba wireless LAN.
The transition will be smooth and Brocade’s customers will be stepping up to a more secure, more stable platform from Aruba. And instead of a story line they'll be getting the real deal.
The corded desk phone is becoming a rarity in most households, having long since been replaced by the more convenient wireless phone. Wireless phones offer untethered mobility, allowing us to make and receive calls wherever it's most convenient to do so. And we're not sacrificing features in the pursuit of mobility. Wireless phones today offer far more calling, conferencing, called ID, and answering options than corded phones ever did.
And then there's the office phone. Like a throwback in time, when we enter the typical place of work we enter a world of wired bondage. Why is the corded desk phone still so prominent in offices?
Single mode and dual-mode Wi-Fi enabled phones are available, but the small handheld devices don't offer the same user experience as a desk phone. There's something just right about a desk phone's handset that makes it ideal for hands-free talking when a speakerphone just won't do.
Problem is that the desk phone just hasn't made the same strides as the wireless handset. Sure, we've added IP connectivity, fancy displays for Caller ID, phone books that simplify dialing, and even wireless headsets to bring us a small measure of mobility. But the modern desk phone still requires a wired Ethernet port, and typically a Power over Ethernet power source, too.
This megalith with a direct lineage extending back to the telegraph is the last hurdle to the introduction of a wireless network edge. Replace the wired desk phone with an enterprise-class Wi-Fi desk phone and you can eliminate a big chuck of the wiring and edge switching infrastructure, lowering costs and saving electricity to boot. You also gain the freedom to locate the phone where you want it, and to make adds, moves, and changes at minimal expense.
134 years after the creation of the phone gave us the freedom to speak with the world, it today shackles us in wired bondage. It tethers us to Ethernet ports, to expensive infrastructure, to yesterday's way of working. Let's look forward to the day when Wi-Fi desk phones set us free at last.
With the ratification of 802.11n just around the corner, it’s a good time to reexamine the fundamentals of Wi-Fi design and determine how this blazingly fast new technology will affect you. Who Moved My Packets is about the design considerations associated with 802.11n data, voice, and video applications.
Let’s start with a discussion about designing for coverage or capacity. For some wireless applications simple connectivity is the biggest issue with which users have to contend. Designing a network for coverage ensures that a Wi-Fi signal can be received at any location in which a Wi-Fi device is likely to be used. Connectivity is the primary objective - bit rate, packet throughout, multi-media support, quality of service, and even redundancy of coverage are secondary considerations.
Consider an indoor application in which Wi-Fi is used to communicate with a pool of bar code scanners for inventory management. The users are few in number, the amount of data transmitted is relatively small. Since the bit rate of an in-building Wi-Fi connection typically falls with distance and in the presence of interference sources, what started as a high speed connection near an access point could drop to 1Mpbs or less just a short distance away. However, even at that low throughput, a network designed for coverage should be sufficient for the application.
Any Wi-Fi network can be designed for coverage, and as a rule, designing for coverage requires far fewer access points. Just crank up the access point power to full, space the access points so that their coverage patterns overlap slightly, and the design part is done. Interference compensation, fair airtime availability, security, and network management are another matter entirely, but they’re outside the scope of this discussion.
A handful of Wi-Fi vendors have made an art of promoting their products as requiring fewer access points. Some Wi-Fi array (multiple access points in one box) and single channel vendors go so far as to tout their “unique” ability to deliver what no other Wi-Fi vendors can accomplish.
It’s all smoke and mirrors. Wi-Fi vendors all use Wi-Fi chip sets from a small pool of IC suppliers, and by regulation the power output of the radios is tightly controller by the government. The distance over which they can transmit, using comparable antennas, is the same. If you pull back the curtain, the secret of their claims is simply that they’re designing for coverage. Nothing more.
In fact, it’s really something less. Why? Because many users need a system that is designed for capacity. In a network designed for capacity, coverage is a given but bit rate, packet throughout, multi-media support, quality of service, and often fault-tolerance are primary considerations.
A capacity-based network requires that the vendor pay keen attention to internal architecture, algorithmic processing, and packet handling necessary to service deployments with a high capacity requirement: (1) large number of users; (2) users that are densely congregated; or (3) applications using voice or streaming video or business-critical telemetry data. Coverage alone is not sufficient for these scenarios – they require guaranteed bit rate, high packet throughout, and quality of service.
These scenarios are already the norm in education, healthcare, and government applications, and are fast becoming typical in enterprise, retail, and industrial deployments. With the migration of data, voice, and video applications to 802.11n from wired LANs, the need for capacity-based Wi-Fi will skyrocket. Users will expect wire-like performance with virtually unconstrained capacity on their shiny new 802.11n networks.
So the next time you’re given a pitch for a wireless LAN with one half, one quarter, one eighth the number of access points of an Aruba network, ask the vendor if they’re designing for coverage or capacity. And ask for test data to back it up. Doing so will avoid following Maj. T.J. 'King' Kong on a ride that is a mistake from the outset.
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