- Extreme Networks allows for up to 8 SSID's per radio, this is not practical in most environments due to the overhead associated with multiple SSIDs. Each SSID has a series of beacons and probe responses that are required for wireless management. These frames can increase the overall channel utilization. Each Access Point must send a beacon out every 100ms at the lowest supported data rate so all clients can receive it. Beacon frames are used by the Access Point to advertise out the SSID, it will inform connected clients that data is available for the client to receive. Wireless users discover available wireless networks using a series of wireless probe requests. When the Access Points gets a probe request, it will respond with a probe response which contains all of its wireless capabilities. Both probe requests and responses are always sent at the lowest supported data rates to ensure delivery to the end clients and Access Points. The more SSID's you have on a specific channel, the more increases in the number of beacon frames and probe responses needed to keep the wireless network running.
- A useful tool that industry experts use is provided by a site called Revolutionwifi. The SSID overhead calculator can help you visualize the overhead associated with multiple SSIDs and Access Points on the same channels. The more SSIDs with Access Points on the same channels and other non-802.11 interference can add up to a poorly working wireless solution.
- The goal of a successful wireless deployment should be to have the least amount of wireless SSID's available. An example might be a school system with multiple SSID's configured for various teams or functions. Example: Student, Faculty, AV Equipment, Guests, Printers, E Blackboards. An administrator could review and consolidate down SSID's by assessing device or user types, then apply Roles, Policy, and VLANs.
- Here are some common deployment scenarios:
- Secure High-Speed SSID: This SSID should be for authorized users or devices. The SSID will use WPA2-Enterprise Level encryption, network access via ExtremeControl, Windows Active Directory/NPS, or LDAP, different rules and roles (example Student/Faculty/Printers), VLANs, and bandwidth limits can be based on user roles or device types. Some variations are to only advertise this SSID out the 5GHz band.
- Guest SSID: This SSID will normally have no encryption. It is configured to provide internet access to clients while keeping them separate from secure resources on the network. Some deployment options use Guest Self-Registration through a Web Browser or Guest Sponsorship, both would be leveraging ExtremeControl.
- Legacy Rate SSID: This would be used for legacy speed devices or devices with lower encryption methods, this should be secured with policy roles to tighten down access. Some variations are to only advertise this SSID out the 2.4GHz Band
- The benefits of using ExtremeControl: