Many enterprises add new service set identifiers to their wireless LAN infrastructure every time a new wireless use case emerges. This practice can crowd the network and degrade performance. Instead, network managers should consolidate service set identifiers with dynamic policy controllers.
Network managers first began assigning unique service set identifiers (SSIDs) to broad categories of users and services, such as guest, voice and corporate data traffic. As more use cases emerged, however, the number of SSID configurations expanded -- with some enterprise Wi-Fi access points advertising SSIDs in the double digits, said Andrew von Nagy, director of evangelism at Mountain View, Calif.-based AirTight Networks and Revolution Wi-Fi blogger.
"The more SSIDs on the network, the more advertisements or beacons [that] are constantly going out over the air for those SSIDs," von Nagy said. "This takes up shared airtime on that channel and detracts from the overall capacity for that wireless network, and even any other Wi-Fi network in range, since it's an unlicensed spectrum."
Multiple SSID network configurations and the impact on Wi-Fi performance
Some wireless LAN access points on the market today technically allow for the creation of upwards of 16 to 64 SSIDs per access point. But just because you can, doesn't mean you should, von Nagy said. Not all enterprises understand that more SSIDs can translate to lower performance rates. "The ideal range is three or fewer," he said.
Different user profiles today -- including mobile, bring your own device (BYOD) and guest users -- can be collapsed down to the same network, allowing IT to dial back the number of SSIDs using dynamic policy enforcement and profiling capabilities built into many access points -- like Aruba's ClearPass, Cisco's Identity Services Engine and Aerohive's HiveManager.
"Today, we can understand who the user is and what device they are on once they authenticate through device profiling, and the access point can dynamically place [the user] onto a different VLAN [virtual local area network] or firewall policy," von Nagy said. "You don't have to have separate SSIDs statically mapped to different access levels on the network anymore."
Not every organization will notice Wi-Fi degradation due to a multiple SSID network design, depending on the applications running on the wireless network, said Matthew Norwood, solutions engineer for BEDROC, a Franklin, Tenn.-based systems integrator. Once an organization starts to run applications sensitive to delay and loss -- like voice -- however, performance issues will become readily apparent, he said.
Wider channels, IT education could eliminate wireless LAN SSID overload issues
Some IT organizations have used multiple SSIDs to save money because the practice allows them to avoid buying more access points. Network managers can avoid the overhead caused by multiple SSID network architectures by using multiple channels -- especially the wider, higher bandwidth channels in the 5 GHz spectrum, said Craig Mathias, principal at the Ashland, Mass.-based advisory firm Farpoint Group.
"Enterprises will get advice both ways on this, but they should start by deploying Wi-Fi as they think they should, and then make adjustments as necessary," Mathias said. "As standards that use higher bandwidth channels -- like 802.11ac -- start to be more widely used, the percentage of time occupied by overhead goes down significantly because it's so much faster."
More on multiple SSID network configurations:
Configuring service set identifiers
Hiding wireless LAN SSIDs on an Aruba access point
Wireless AP SSID and channel configuration
The lack of Wi-Fi expertise within an enterprise can be a hindrance to network performance, BEDROC's Norwood said. Not many IT teams have a strong understanding of radio frequencies and of how traffic will flow through the wireless network from an air quality perspective, he said. "There is a common belief [IT] can just spin up another SSID for any new service [a business] might need, and performance can be fixed by adding in more access points, which means the broadcasting of more SSIDs, so the problem gets compounded over time."
Education on the policy and access control products and services that have entered the market in the past few years will be critical in helping IT professionals better understand wireless networks, and how older methods -- like deploying new SSIDs for new services -- can negatively impact Wi-Fi performance, Revolution Wi-Fi's von Nagy said.
"For enterprises that are weighing the differences between adding more SSIDs or rolling new services into existing SSIDs, they'll really need to take a look at the architecture they have deployed to see if they have the tools capable of policy enforcement," he said. "With BYOD and the myriad new use cases, it's really not going to be practical to constantly spin up new SSIDs moving forward."