What are your thoughts on good strategies for enabling legacy client support while rolling out 11ac?

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Migration plan for legacy clients
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Lisa Phifer

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Posted 5 years ago

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Dale M. Rapp

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Same type of question here... is it best to replace 802.11n ap devices with ac and run in some mixed mode format until all n aps are replaced, or build ac network separate of n network then turn off the n network and switch all clients to ac network? Guessing the progression of client devices supporting ac may push momentum to ac?
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Nick Lowe, Official Rep

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You'll still be using 802.11n at 2.4GHz, remember...
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Dale M. Rapp

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Our n network has multiple ssids running in both bands...
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Nick Lowe, Official Rep

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I only meant that, unless you plan to go to 5GHz only, you'll still end up having 802.11n as part of the equation. (The ac APs you buy will still be doing 802.11n at 2.4GHz otherwise.)
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Lisa Phifer

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Yes and you'll probably have plenty of 2.4 GHz only 11n clients to support, at least in the near term.
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Matthew Gast

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Fortunately, 802.11ac has good backward-compatibility support. Transmissions in 11ac start off in exactly the same way as 802.11a and 802.11n's mixed mode, so even the oldest 802.11a device can understand that an 802.11ac transmission is using the radio medium. For the same reason, management and control frames are transmitted on 20 MHz channels so they can be understood by previous clients.

It also helps that protocol features like the wider channels have backwards-compatibility features built in. Newer 11ac clients can use wider channels without interrupting access from older clients.

From a basic technology level, you can upgrade the infrastructure to 802.11ac, and 802.11a/n devices will continue to work just fine. What you need to do in the process is make sure that the newer devices don't take over the network by using their newfound capacity to swamp the older devices. Tools that give you visibility into the applications in use so you can protect important applications are likely to be an important part of your transition.
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EvaldasOu

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So if 802.11ac AP can understand 802.11a/n , will 802.11a/n AP understand that 802.11ac frame is on the air? ( I mean it of course will not understand the frame from the beginning till the end, but will it detect it and wait before sending?)
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Matthew Gast

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Yup, they will. The PHY-layer headers are exactly the same, so an 802.11a/n AP will understand how long the 11ac transmission goes for.
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Craig Mathias

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I think it's still a good idea to run dedicated legacy channels, rather than mixing .11n and .11ac on the same channel. Remember, those .11ac clients will need to wait for the .11n clients - Ferraris stuck behind Volkswagens (same analogy we used for .11n coexisting with .11g).
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Dale M. Rapp

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Awesome... thanks for the discussion! It seems like 802.11ac was just a buzzword and now it feels like everyone is scrambling to update their networks and it almost makes 802.11n a speed bump in the progression of wireless networks!