4 ms·

I’m no expert on these matters, but WiFi roaming is covered by 802.11r and WiFi-meshes by 802.11s. I assume these specs include mandated behavior in both the A

I’m no expert on these matters, but WiFi roaming is covered by 802.11r and WiFi-meshes by 802.11s. I assume these specs include mandated behavior in both the APs and the clients.

admax88q 8y ago
Traditionally roaming is left to the client device and most implementations are so bad that they won't give up on an old AP so long as they're seeing beacons every year or so. Who cares that I haven't successfully received a packet in the last hour, it's sure better than the 2 second interruption we'll get if we tried to switch. I'm only mildly bitter at the useless roaming behaviour of most clients. Turning transmit power down doesn't really help either. Some clients will roam better but other clients at the edge of the coverage now have no coverage.
- josteink 8y ago
  Using software on my smartphone I can observe that it changes AP it associates with as I walk around the house where I have a “traditional” 802.11r WiFi network with common wired backend. No new DHCP is triggered either. So it may not be perfect, but it can’t be that bad.
  - jtmarl1n 8y ago
    What do you use to verify which AP your device is connected to? I've not found a convenient way to do this for testing.
    - stupidthrottle 8y ago
      Net Analyzer for iPhone shows the raw BSSID (AP mac) for whatever network you connect to.
    - noselasd 8y ago
      You need to know the MAC address of each of your access points - also known as the BSSID. It should be available in the admin UI of the access point, and sometimes also printed on a label attached to the AP. Knowing that, you need something that shows you details about wifi connections, so you can view the BSSID (MAC address of the AP) you're connected to: Android, iOS: Install the "Network Info II" app Linux: use the iwconfig command Windows: Use the command "netsh wlan show interfaces"
- Nextgrid 8y ago
  802.11r solves this. I’ve got it configured at my place and roaming is seamless and takes less than 100ms.
  - spac 8y ago
    Can you elaborate on how you configured? What hardware are you using?
    - Nextgrid 8y ago
      I had a few Devolo powerline adapters (which include a WiFi access point) and I reflashed the firmware with OpenWrt as a last resort (the default firmware didn’t support 802.11r and it was hell without it). Works great since then and it saves me from buying a set of enterprise-grade APs.
  - admax88q 8y ago
    802.11r does not fix this. It makes the handoff slightly more efficient but the client still has to decide to actually do the handoff. And that's the part that never seems to happen, as many clients are stupid.
    - Nextgrid 8y ago
      From my testing with iPhones, the stupid behaviour goes away on an 802.11r-enabled network. I noticed the same issues on a legacy network but that all went away after enabling 11r.
      - admax88q 8y ago
        I would imagine that I phones has better roaming preference overall. But maybe having 802.11r enabled causes devices to be more optimistic in their roaming as they know they're not switching networks.
PaulHoule 8y ago
The Ubiquiti access points and I assume some other brands use the following method to implement roaming: All of the access points broadcast a certain SSID. When a client tries to connect, they coordinate with each other to choose which one will reply to that particular client. That is, the client things it is connected to one AP and doesn't know anything special is happening. If the system wants to move your client to another AP it just disconnects you from the first AP and when you try to reconnect the second AP will reply to you. In a case like that, assignment is driven as much as "having a clear channel" as "having a better connection on the channel". If you had a choice between two channels, once of which was shared and slightly "better" and another you can have to yourself, you are better off having one to yourself. (That way you aren't having to wait for other clients to stop sending or receiving, dealing with interference, etc.) A corollary to that is that if you have both 5GHz and 2.4GHz support on an access point you do best distributing clients between both sides, even if people think 5GHz is better or that 2.4GHz performs better in real life. I am amazed that instead of all the silly gimmicks that APs have been marketed with, nobody has come out with one that has a lot of radios working on different channels and just behaves like a large number of APs. Practically I think this would work way better than channel aggregation.
- patentatt 8y ago
  Is that how Ubiquiti APs work currently, or is this a description of the now deprecated “fast roaming” thing they were doing a while back? Edit: meant “zero handoff” per replies below.
  - exelius 8y ago
    That type of roaming actually ends up breaking a lot of WiFi implementations — it’s really only super useful for WiFi VoIP phones. I worked with a vendor (Bandspeed) doing that kind of WiFi roaming back in 2005, so it’s not remotely a new concept. Most other devices will jump to another AP broadcasting on the same SSID if the signal is a lot stronger. It’s not nearly as much of an issue as it used to be, but people expect WiFi to Just Work (tm) so it’s better to let the OS’ network stack manage it.
  - 8y ago

I’m no expert on these matters, but WiFi roaming is covered by 802.11r and WiFi-meshes by 802.11s. I assume these specs include mandated behavior in both the APs and the clients.

admax88q 8y ago

Traditionally roaming is left to the client device and most implementations are so bad that they won't give up on an old AP so long as they're seeing beacons every year or so. Who cares that I haven't successfully received a packet in the last hour, it's sure better than the 2 second interruption we'll get if we tried to switch. I'm only mildly bitter at the useless roaming behaviour of most clients. Turning transmit power down doesn't really help either. Some clients will roam better but other clients at the edge of the coverage now have no coverage.

josteink 8y ago
Using software on my smartphone I can observe that it changes AP it associates with as I walk around the house where I have a “traditional” 802.11r WiFi network with common wired backend. No new DHCP is triggered either. So it may not be perfect, but it can’t be that bad.
- jtmarl1n 8y ago
  What do you use to verify which AP your device is connected to? I've not found a convenient way to do this for testing.
  - stupidthrottle 8y ago
    Net Analyzer for iPhone shows the raw BSSID (AP mac) for whatever network you connect to.
  - noselasd 8y ago
    You need to know the MAC address of each of your access points - also known as the BSSID. It should be available in the admin UI of the access point, and sometimes also printed on a label attached to the AP. Knowing that, you need something that shows you details about wifi connections, so you can view the BSSID (MAC address of the AP) you're connected to: Android, iOS: Install the "Network Info II" app Linux: use the iwconfig command Windows: Use the command "netsh wlan show interfaces"
Nextgrid 8y ago
802.11r solves this. I’ve got it configured at my place and roaming is seamless and takes less than 100ms.
- spac 8y ago
  Can you elaborate on how you configured? What hardware are you using?
  - Nextgrid 8y ago
    I had a few Devolo powerline adapters (which include a WiFi access point) and I reflashed the firmware with OpenWrt as a last resort (the default firmware didn’t support 802.11r and it was hell without it). Works great since then and it saves me from buying a set of enterprise-grade APs.
- admax88q 8y ago
  802.11r does not fix this. It makes the handoff slightly more efficient but the client still has to decide to actually do the handoff. And that's the part that never seems to happen, as many clients are stupid.
  - Nextgrid 8y ago
    From my testing with iPhones, the stupid behaviour goes away on an 802.11r-enabled network. I noticed the same issues on a legacy network but that all went away after enabling 11r.
    - admax88q 8y ago
      I would imagine that I phones has better roaming preference overall. But maybe having 802.11r enabled causes devices to be more optimistic in their roaming as they know they're not switching networks.

PaulHoule 8y ago

The Ubiquiti access points and I assume some other brands use the following method to implement roaming: All of the access points broadcast a certain SSID. When a client tries to connect, they coordinate with each other to choose which one will reply to that particular client. That is, the client things it is connected to one AP and doesn't know anything special is happening. If the system wants to move your client to another AP it just disconnects you from the first AP and when you try to reconnect the second AP will reply to you. In a case like that, assignment is driven as much as "having a clear channel" as "having a better connection on the channel". If you had a choice between two channels, once of which was shared and slightly "better" and another you can have to yourself, you are better off having one to yourself. (That way you aren't having to wait for other clients to stop sending or receiving, dealing with interference, etc.) A corollary to that is that if you have both 5GHz and 2.4GHz support on an access point you do best distributing clients between both sides, even if people think 5GHz is better or that 2.4GHz performs better in real life. I am amazed that instead of all the silly gimmicks that APs have been marketed with, nobody has come out with one that has a lot of radios working on different channels and just behaves like a large number of APs. Practically I think this would work way better than channel aggregation.

patentatt 8y ago
Is that how Ubiquiti APs work currently, or is this a description of the now deprecated “fast roaming” thing they were doing a while back? Edit: meant “zero handoff” per replies below.
- exelius 8y ago
  That type of roaming actually ends up breaking a lot of WiFi implementations — it’s really only super useful for WiFi VoIP phones. I worked with a vendor (Bandspeed) doing that kind of WiFi roaming back in 2005, so it’s not remotely a new concept. Most other devices will jump to another AP broadcasting on the same SSID if the signal is a lot stronger. It’s not nearly as much of an issue as it used to be, but people expect WiFi to Just Work (tm) so it’s better to let the OS’ network stack manage it.
- 8y ago