How many SSID’s can a wifi access point provide?
The Big Question
This is a question we run into constantly when we are working with new and existing clients. They ask this question because they are under the assumption they need to provide a separate SSID for every type of new device that is introduced into their environment or for every new initiative that gets rolled out.
The answer to this question is technically dependent on the device manufacturer and the hardware they sell. From what I have seen advertised by various manufacturers the number of supported SSIDs runs between 8 and 64. While 8 SSIDs might be achievable there is no way 64 SSIDs would be due to the inherent traffic management overhead that wireless introduces.
Overhead
Wireless access points and client devices all create some type of traffic that is considered overhead. Wireless clients transmit probes through the air to find access points and access points transmit beacons and probe responses to the clients. All this beaconing, probing and responding creates a considerable amount of traffic and in some cases can create up to 7-10% of the wireless traffic. Now if you take that 7-10% and multiply it by the number of SSIDs you are using you can see how quickly the performance of your wireless network can degrade. A 5 SSID implementation could use up to 50% of the available bandwidth for wireless just in the management overhead!
What I advise my customers, new and existing, to use as a limit is no more than 4 SSIDs. In my experience 4 SSIDs seems to cover 99% of what all my clients need to support their users, devices and initiatives. The way the SSIDs break down is this:
SSID #1
This is used for staff, faculty, employees, studentsand the devices they use provided either by the organization or by the end user. With the proper WLAN solution you can provide a secure solution for even personal devices brought on premise that will not compromise the integrity of your network.
SSID #2
This is used for Visitor and Contractor access. Again, I point out that with the proper WLAN solution you can define the type of user; Guest or Contractor and allow them appropriate, secure access to your network or the Internet without compromising your network security.
SSID #3
This is used for devices with weak encryption (WEP) and possibly limited to 802.11bwhich has the effect of bringing down other wireless clients to their limited data rates. By segregating these clients to a separate SSID you eliminate the “penalty” they impose on faster 802.11g/n clients.
SSID #4
This your catch-all for all the other devices within the organization that can handle secure authentication and encryption schemes. With our wireless solution we can identify the type of device that it is and the types of packets it is transmitting and do QoS (Quality of Service) on that traffic to either give it priority (in the use of a Wi-Fi VoIP phone or streaming video) or bandwidth limit it when it is a gaming console or iPad trying to stream Netflix.
