Users are increasingly carrying their iPads, iPhones and Android smartphones into the workplace. These mobile devices and tablets introduce new security threats and IT management challenges.
Join us for the third in our series of webinars to learn about new Cisco innovations that will help you identify the devices, apply policies and enable user management across wired and wireless networks. Featuring special guest speaker Dan Larkin, Director of Strategic Operations for the National Cyber-Forensics and Training Alliance (NCFTA) who will share the new threat vectors introduced due the influx of mobile devices. Take control of your network now.
Live webcast Wednesday, May 4th from 10:00 -- 11am PDT (12:00 -- 1:00pm EDT) Register now!
One of the key tenets of engineering is to reduce complexity, but in doing so it is important to understand the implications. While we might try to view one technology as it relates to another to help us simplify the details, it is important that we recognise how and where they differ.
Case in point.
When it comes to wireless networks, I often talk about how there are two questions I dislike being asked more than any others:
How many clients can connect to an access point?
What is the maximum range of an access point?
The reason is that I believe they are the wrong questions. They are being asked from perspective of someone trying to relate to a wireless network as if it were a wired network. What they are really asking is “how many switch ports do I need to cover this area?”
But wireless networks are not switched networks. While each connected device in a wired network has its own physical cable, and thereby its own gigabit Ethernet link, in a wireless network, every device connected to a particular access point shares the same RF spectrum, the same total available bandwidth.
For a standard access point in today’s deployments, that means a maximum total bandwidth of 144Mbps on the 2.4GHz band with a 20MHz channel and 300Mbps on the 5GHz band with a 40MHz channel using channel bonding.
But that is an over simplification.
Those aggregate bandwidths assume each client is connected at the highest available data rate. As we increase range, however, the data rate decreases, thereby reducing the overall channel utilisation. Therefore, with fewer access points, we are not just sharing a limited amount of bandwidth with more clients, but we are actually reducing the total available bandwidth.
Interference, particularly as access points cover larger areas, becomes an even greater issue. An increase in the signal to noise ratio leads to a decrease in the maximum sustainable data rate. This again reduces the overall channel utilisation. The key here is that a wireless network’s ability to not only detect, but where possible mitigate interference is critical to its ability to sustain higher data rates and maximise the total available bandwidth in each cell.
All this assumes that the wireless clients connecting to the network are even capable of supporting those high data rates.
Most smartphones on the market today support only 802.11g in the 2.4GHz band, meaning that at most they can support 54Mbps.
Newer devices, such as the iPhone 4, support 802.11n, but only in 2.4GHz, and only with a single antenna, limiting them to a single “spatial stream”—in simple terms that means the maximum data rate they can support is 72Mbps.
This applies to tablet devices as well. While the new iPad2 supports 802.11n in both the 2.4GHz and 5GHz band, it too is limited to a single spatial stream. The Cius goes one step further with support for channel bonding in 5GHz, increasing the maximum data rate to 150Mbps.
Interestingly, we are now starting to see new access points enter the market using Atheros’ first-generation silicon supporting three spatial streams. While this increases the maximum data rate in the 5GHz band to 450Mbps, as we have just seen, this will have no impact on the multitude of mobile devices given their single spatial stream limitation.
Three spatial streams represents a key milestone for the 802.11 standard, and will become increasingly important over the next 2 to 3 years as battery technology improves and wireless chipsets incorporate better power saving designs. Of course, by that time we will be looking at access points supporting four spatial streams and 600Mbps—and again, be waiting for the mobile devices to catch up.
As we look to support these many different mobile devices entering the market today along with their high bandwidth applications, clearly the two key areas we must consider in our wireless network designs are access point density to control cell sizes, and interference detection and mitigation capabilities to ensure that we maximise the channel utilisation in each cell.
And so, I’d like to propose two different questions to consider at the start of a wireless deployment:
How many different devices do you expect to connect to the wireless network?
And what are the applications that will run across the network and what are their associated bandwidth requirements?
Wireless and wired networks fundamentally differ at the physical layer. While its not necessarily important to understand the details of RF communications, it is important to understand the implications.
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There’s a lot happening at our 15th Partner Summit—big news announcements for partners, not to mention keynotes, business breakout sessions, executive chats, and parties, too.
So what’s on tap for this week? To keep you in the know, we’ll have special Partner Update newscasts from New Orleans, so you don’t miss any of the Partner Summit news. And here’s what happened on day one of the event:
Can you believe it? We’re less than a week away from Cisco’s Partner Summit! Many of you will likely be attending the event virtually—if you haven’t yet registered, please visit the Virtual Partner Summit registration page to sign up (it’s free). The virtual event runs March 1 through March 3.
But maybe you’re wondering, “all right, what’s so cool about this Virtual Partner Summit thing?”and “What exactly do you do inside a virtual event?”
Glad you asked! Join me on a quick tour of Virtual Partner Summit (or VPS for short) so you can find out…
When you enter for the first time, the friendly face of none other than Edison Peres Cisco’s SVP of WW Channels will greet you. He will provide some background and give you a quick rundown of what you’ll find inside VPS and help you navigate the environment.
Using the kiosk behind Edison, you’ll be able to visit the various rooms and areas in Virtual Partner Summit allowing you to attend keynotes, breakout sessions, network, earn prizes, watch replays, and join live video chats with Cisco executives and guest speakers. To get back to this main screen, just click Home from the kiosk or use the menu bar at the top of the page.
