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I've been reading a lot about iPhone probing in particular lately for a project I am working on involving device detection and I just wanted to be clear on some of the terms I've been seeing.

Here's how I currently would define these 3 words at a high level:

  1. Roaming - the decision a device makes to search for a new AP given certain requirements determined by the device

  2. Probing - The act of finding APs by making 'probe requests' or requesting information from detectable APs

  3. Scanning - I honestly think this is synonymous wth probing? I've read about active and passive scanning and I'm not sure how smartphones utilize that or whether that is any different from probing.

In general I think of Roaming as the umbrella term and probing/scanning as the method by which the client roams.

Are there any more details I'd need to distinguish between these terms? Thanks for the help!

AIntel
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1 Answers1

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You have done your research quite well. Probing is an active scanning method, which is faster than passive scanning by waiting for beacons sent periodically by an AP.

Both active and passive scanning are used for gathering information. Roaming, i.e. changing between APs, is always a decision made by a client, based on such information.

Currently there isn't a method an AP could use for suggesting a client to roam to a different AP, despite centrally managed wireless networks might have better intelligence on the overall situation than the client. However, the roaming has become smarter as the signal strenght isn't the only variable used for this decision anymore:

IEEE 802.11k and 802.11r are industry standards that enable seamless Basic Service Set (BSS) transitions in the WLAN environment. The 802.11k standard provides information to discover the best available access point. 802.11k is intended to improve the way traffic is distributed within a network.

Esa Jokinen
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