Top 5 Wireless LAN Performance IssuesBy CWNP On 06/22/2010 - 29 Comments
As I have been working closely with wireless security over the last several years of my life, I have demonstrated a clear tendency towards blogging about security issues. However, once an enterprise starts moving towards a secure WLAN, the problems naturally shifts towards performance. This blog is dedicated to WLAN performance issues. Several dozens of WLAN performance problems are common. However, in a typical enterprise scenario, what are the Top 5 issues that bother the WLAN operations team the most? In my experience working with customers, these 5 issues are at the top of the list. Let me know if you disagree.
- Client connection issues: I believe that one of the most common problems to-date is the fact that users are not able to connect to the enterprise Wi-Fi network in the first place. Often, this will be due to poor coverage at a specific location or some wrong configuration on the Wi-Fi client. Although enterprises have started using sophisticated tools for Wi-Fi coverage planning, note that this is mostly a one-time activity. Hence, given the dynamic nature of RF and perhaps changes in the physical environment as well, coverage can change at certain locations. In some cases, even though coverage may be good, clients may not be able to connect due to configuration issues. It can be as simple as a user not choosing the right WLAN profile. Or, it can be due to the fact that the user does not remember his password or has “lost” his prior configuration (It has happened to me more than once - due to some weird Windows issues. Our IT team had to re-install my WLAN drivers and its configuration). Regardless of the specific issue, clients (not the infrastructure) are often responsible for most performance related problems.
- Insufficient capacity: Planning for proper coverage may be hard, but planning for capacity is harder. Given the varying number of users that can access an AP and the fact that it is very hard to predict the workload of each user, getting the WLAN capacity right is a challenge. Hence, it is quite possible that a WLAN may not meet the bandwidth or latency requirements under load. Also, given the shared nature of the medium, a single client operating at a low-speed (e.g., 1 Mbps) can bring down the overall performance of your WLAN (Note that that this is possible even if your enterprise allows only high-speed connections – think about your friendly neighborhood). Another reason for the capacity issues is asymmetric load on your APs – for example, APs in a conference room may get choked during large meetings. Just adding more APs may not help – it can lead to the next problem
- Interference: It is well-known that WLANs are interference prone. Interference can be Wi-Fi based or non Wi-Fi based. Wi-Fi based interference can occur when users make the mistake of increasing the density of APs in the hope of increasing capacity. Or, it can occur due to neighboring APs operating on the same (or adjacent channels). Non Wi-Fi interference can occur as a result of RF-generating equipment that shares the spectrum with your WLAN – e.g., microwave Owens, cordless telephone, surveillance cameras. The exact impact of such interference depends on several factors – proximity of the interfering source, power of interfering source, power of the Wi-Fi device, type of RF emission, etc. Based on some of these factors, the impact may or may not be obvious. But, it is always a good idea to monitor for such interfering sources and see if any action can be taken to minimize them (e.g., remove the interfering source if it is in your control or see if you can configure your WLAN on a less “crowded” channel).
- VoIP quality Issues: As more and more users start relying on Wi-Fi for voice, the QoS expectations from a WLAN will only increase. However, given the shared nature of RF, providing wire-like quality is very challenging. Although vendors are implementing various (standard and proprietary) techniques to deal with this problem, getting VoWiFi right will continue to pose issues for the enterprise network ops team. Voice calls can get easily impacted by common hurdles such as heavy data traffic or uncontrolled roaming.
- Implementation issues/bugs: As new devices and standards enter the market, you are never sure whether their implementations are thoroughly baked. Apple iPad Wi-Fi issues that made a lot of news recently are an unfortunate example of this. Even if we treat this specific incident as an exception, I am still worried about the issues introduced by the rapid flurry of new devices in an enterprise. With the time-to-market pressure always present, it is likely that other devices will have bugs/issues, which can affect your entire WLAN operations.
Do let me know if your WLAN performance experiences indicate a completely different story.