AirO is intended for technical and not-too-technical owners of Wi-Fi capable Android devices. It displays the health of the Wi-Fi (“Local Area”) connection, and measures the characteristics of a “Wide Area” connection to a server deeper in the network. It can be used to answer questions like:
• What’s wrong with my Wi-Fi today?
• How strong is my Wi-Fi signal?
• Is there evidence of wireless interference?
• Is the problem in the Wi-Fi connection, or out on the Internet (or corporate network)?
• Is the overall connection to the data center good enough to run my corporate apps?
The top “Wi-Fi and Local Area Network” section of the screen displays three measurements that show the health of the Wi-Fi connection:
• Signal Strength. In Wi-Fi terms, this is received signal strength, or RSSI. It is measured in dBm and is always negative. A larger (negative) number indicates a weaker signal.
o When right next to an access point, the figure might be -35 dBm
o When standing underneath a ceiling-mounted access point, perhaps -40dBm
o A ‘good’ signal is better than -68dBm
o The signal will be problematic below -75dBm
o A signal of -80 dBm is generally unreliable to unworkable
We measure signal strength first because if it’s poor, there is no chance of getting a good connection. The remedy, in simple terms, is to get closer to the access point.
• Link Speed. This is technically the modulation rate of the Wi-Fi link in Mbps.
o A new 802.11ac device (Samsung Galaxy S4) might show 200+ Mbps maximum
o An 802.11n device might reach 65 Mbps or 130 Mbps with 40 MHz channels
o Under normal conditions a link faster than 20 Mbps is very good
o Once a link drops below 5 Mbps it is likely to be unreliable
The usual cause of low link speeds is poor signal strength. But sometimes, even when signal strength is good, interference on the air from Wi-Fi and non-Wi-Fi sources reduces link speeds.
• Ping. This is the familiar ICMP echo test to the network’s default gateway.
o With good conditions, a stable delay of less than 20 msec is expected
o If ping times are consistently over 100 msec, application performance will suffer
o A ping time above 500 msec indicates something’s wrong
A low link speed will often cause long ping times. If link speeds are good but pings slow, it may be a long way to the default gateway over a narrow broadband connection.
The lower section of the screen displays results from tests between the device and a server computer, usually in the corporate data center or on the Internet. The address of this server is chosen from a number configured in ‘settings' – but once chosen, only one server address is used for these tests.
• Ping. There is a ping measurement to this server. It is the same ping test as above, but because this one goes farther it will normally (but not always) take longer. Again, 20msec would be fast and 500 msec would be slow.
Some networks may block ICMP (ping) traffic. In this case, the Wide Area Network ping test will always fail, but normal (e.g. Web) traffic may pass.
• Speedtest. The next tests are ‘speedtests’. For this, we use the iPerf function (iPerf v2). In a corporate context, this should be an iPerf server instance set up somewhere in the core of the network, probably a data center. Because it is a (TCP) throughput test, the figures here will never be more than about 50% of the ‘link speed’ figure for the Wi-Fi connection. The iPerf client in the app is configured to run in bidirectional mode, first an upstream test then downstream.
o In a corporate network, uplink and downlink speedtest should give a figure higher than 10M bps.
o In a home network, the speed will usually be limited by the broadband connection rate. A figure of 1 to 10 Mbps can be expected. In home networks, or behind firewalls, the downstream test may fail to pass the firewall, but this does not indicate normal (e.g. Web) traffic will fail.
AirO version 6 solves the 'empty email attachment' bug
- Because we're using iPerf v2, the downstream test can fail due to failure to negotiate firewalls. Inside a corporate network this shouldn't be a problem.
- There are two default IP addresses configured for the iPerf server, a public server and another that's only reachable inside the Aruba corporate firewall. The list of host addresses in 'settings' is an ordered list, and allows users to add their own server addresses.