Using Wireshark's Editcap to Reduce Your Trace File Size (by Tony Fortunato)
Slow Applications? Don’t Overlook Packet Loss (by Chris Greer)

Setting the Foundation: What to Remember When Moving to 802.11n (Jay Botelho)


Moving

The advent of 802.11n is delivering wireless networking speeds that are comparable to those of wired networks. But like any evolving technology, it is important to have a reason to migrate, knowledge on executing the migration, and the ability to manage your new system.

So, when should you start migrating to 11n?

The time to start moving to this new standard is when you need the bandwidth, and it’s quite likely that your WLAN is already beginning to feel the pressure. With the widespread adoption of smart phones and tablets that use WLAN networks whenever they are available, demand for WLAN access is skyrocketing. This is particularly true in high concentration areas, like university classrooms and common areas, but it is also increasingly common for hotspots and within enterprise WLANs. With nearly a 10-fold increase in throughput (from 54Mbps to 450Mbps) with currently available commercial equipment, a move to 11n is likely to satisfy your bandwidth needs.

In addition, you should migrate to 11n whenever you need to upgrade any component in your existing infrastructure, whether it’s because your equipment is nearing the end of its lifecycle or because certain components have simply failed.

The only reason to wait is if you really truly don’t need the bandwidth today, and decide it’s in your best interest to hold out for just a bit more performance. Although the 11n specification calls for throughput up to 600Mbps, most access points available today are only capable of 450Mbps, and there are fewer wireless clients that can achieve this level of performance. It took manufacturers several years after the ratification of the specification to advance the technology such that 450Mbps operation is feasible, and it will likely be several more years before equipment capable of the full 600Mbps starts to become widely available. Is it worth the wait to you?

How should you prepare?

Most 11n migrations can be pretty involved, and usually include a significant expansion of the current WLAN. It’s best to break the process down into three phases: design and requirements; deployment and verification; and management, troubleshooting and expansion. This is detailed in the following blog posts -- “Let’s Start Transferring to 802.11n” and “Three Considerations for Designing and Managing Your Wireless Network”.

Now, how do you monitor your new environment?

11n presents a significantly more complex environment, with many factors to consider including which software solutions are fully capable of monitoring and analyzing your entire network to what hardware is needed to analyze the maximum capabilities of your new deployment. Below are some of the key factors for you to consider, but if you need more in-depth insight please check out WildPackets’ webinar, 802.11n – Are You Seeing It All?

Wireless AND wired analysis
The WLAN is often treated as a completely separate entity, or “overlay”, of the wired network, but of course your WLAN is connected in some fashion to a wired network, so you always have a mixed environment to manage and analyze. The network must be viewed as a unified wired/wireless network that requires centralized management.

Insist on network analysis solutions that can handle wireless and wired analysis, simultaneously, and compare traffic from both sides of the network. And even if you’re not ready for a WLAN migration, you may be ready for a WLAN analysis system upgrade. Even if there are no 11n capable access points in your environment, the company next door or upstairs from you may have them in their WLAN, and they are bleeding into your environment. Make sure you can see, interpret, and analyze everything that can affect your WLAN performance.

Choose the Right Wireless Adapter
In the “old days”, specifying whether devices were “a”, “b”, and/or “g” was enough. But with all of the configuration and data rate options available in 802.11n, specifying only “n” is not enough. The maximum level of MIMO support, channel bonding support, and short GI (guard interval) support are all key to achieving maximum data rates in 11n, and are equally important when choosing wireless adapters for use in WLAN analysis. Below are key considerations for choosing a wireless adapter to ensure you can see all of the possible traffic in your 11n environment:

  • Remember NxM:n -- Where N equals the number of transmit antennas, M equals the number of receive antennas, and n equals the number of MIMO streams that the hardware can support, whether for an AP or a wireless client. It is critical to know the “NxM:n” ratings for all 11n equipment in use in your WLAN. For example, if you deploy APs that are 3x3:2, the APs will have 3 transmit and 3 receive antennas, but will only be capable of at most 2 unique data streams and will have a maximum throughput rating of 300Mbps. This is currently something that seems to be widely misunderstood, with many user expecting that if a device is 3x3 then it is automatically capable of 3-stream MIMO operation and will achieve 450Mbps throughput. Knowing the number of antennas is not enough. It must also be explicitly stated by the manufacturer how many MIMO streams are supported, or at least what the maximum supported throughput is.

    And when it comes to network analysis, the wireless adapters used to capture data with your network analysis solution must match the maximum capability of the equipment in your WLAN. So, even if you only plan to migrate a portion of your WLAN to 3-stream capable devices, you must have wireless adapters and associated network analysis software capable of capturing and analyzing 3-stream 11n data.

  • Support for three data streams is difficult to find -- There are lots of 3X3 wireless adapters and APs available. But 3X3:3 with support for three data streams is more difficult to find. There are more APs that fit this criterion than wireless adapters. To find out if the wireless adapter will work confirm that it supports 450Mbps.

When in Roam
Roaming is the cause of many wireless issues, especially with time-sensitive protocols like voice and video. Be sure to have a monitoring and analysis system in place that gives detailed and accurate measurements from many perspectives, and has the capability to analyze wireless roaming and perform multiple channel analysis.

Jay Botelho wildpackets HeadshotWp_logo Authors Bio: Jay Botelho is the Director of Product Management at WildPackets, Inc., a leading network analysis solutions provider for networks of all sizes and topologies. Jay holds an MSEE, and is an industry veteran with over 25 years of experience in product management, product marketing, program management and complex analysis. From the first mobile computers developed by GRiD Systems to modern day network infrastructure systems, Jay has been instrumental in setting corporate direction, specifying requirements for industry-leading hardware and software products, and growing product sales through targeted product marketing.

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