Wi-Fi roaming protocols.
Wi-Fi roaming protocols.
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Wi-Fi roaming means moving from one customer's base station to another in the territory and maintaining a connection during the base station switching process. Thus, the term is slightly different in mobile communications, where the same thing is understood as handover, but it is not very critical in mobile communications, because the density of base stations is hundreds of times higher in the mobile communications network.

The history of Wi-Fi networks goes back 20 years, and initially roaming was seen as the customer's ability to scan nearby base stations and decide for themselves which base station to choose. You can find roaming settings in the settings of many client devices. However, such a solution is no longer sustainable and reliable in today's situation, as the networks have become completely different, the density of base stations and the variability of services have increased many times over. For example, the ability to dynamically balance customers between 5 GHz and 2.4 GHz has been introduced, as well as VoWiFi or applications in industry or warehousing that require uninterrupted communication.

Here we describe what the 802.11 r / v / k protocols mean in a Wi-Fi network and why it is important that they exist on both APs and client devices. Let's just say that customer equipment support is still around at 20% today, so if you should choose equipment for a warehouse or a large area, or even for an office, it's always worth testing these features.

802.11k information exchange between APs and clients

802.11k allows customers to tell each other which base stations are nearby and thus better decide which decisions should be made in the roaming process. In this case, the customer does not have to scan the network when moving, firstly it would take time and secondly the picture would be inaccurate from the customer's point of view, because the information is often incomplete when moving.

802.11r fast roaming FT fast transition

If 11r is not supported on the client or AP, it is probably not a modern network. For example, for Android devices, without 11r protocol, even in case of a base station change, phones renew ip through DHCP and application connections are definitely lost.

The 11r protocol allows keys to be stored during the reassociation process, so there is no need to go through a complicated authentication and IP request procedure every time.

802.11v network driven roaming

Tihti ei tea kliendiseade võrgu hetkeolukorda, näiteks AP võib olla väga koormatud, antud kanalil võivad olla häired või on vaja AP-d restartida näiteks tarkvarauuenduse jaoks. 802.11v protokolli abil saab AP paluda kliendil roamida teise AP alasse. Ruckuse lahenduses kasutatakse seda näiteks ChannelFly protokolli puhul, kus AP vahetab sagedust ja seega peavad kliendid seda sama kiirelt tegema.

Often, the client device does not know the current state of the network, the AP may be very busy, the channel may be interrupted, or the AP may need to be restarted, for example for a software update. With 802.11v protocol, the AP can ask the client to roam to another AP area. In the Ruckus solution, it is used in the case of the ChannelFly protocol, where the AP changes the frequency and thus the customers have to follow it as fast.

For example, the load on 2.4 GHz channels is often too high today, and 802.11v allows customers to switch to dynamic 5 GHz. Apple, Windows and newer Android phones such as Galaxy S8, S9, S10 are able to support it.

How do we test client devices

The 3K office has a fixed Ruckus R series AP house-long corridor network in place, which allows debugging to monitor various roaming problems. Smartzone allows to collect diagnostic information from many APs at once and displays the results graphically. This diagnostics is suitable for studying most customer problems, but in this case we focus on Android handheld terminals used in warehouses.

In the following example, the client will not be able to roam at all, the client had to re-authenticate and unfortunately the client has also lost the ip. Such roaming behavior will definitely hinder the trouble-free operation of the applications.

With correct roaming, an FT auth request is made and an authentication response is received.

In this test sequence we used four AP monitors at a time. It allowed us to test the behavior of different operating systems and devices in roaming situations.

Autor: Support