I did some tests regarding this issue and it seems that several Apple products are affected. The devices I tested are:
* Late 2013 MacBook 13" Retina
* iPad Air 1
* iPhone 5s
All of them show fluctuating ping times between 20ms and 300ms, but only if they are pinged. If I ping a non-Apple device from an Apple device the times are normal below 4ms.
The scenarios I tested:
ThinkPad -cable-> AP -wifi-> Apple-Device == fluctuating pings
Apple-Device -wifi-> AP -cable-> ThinkPad == constant pings
Nexus 5 Wifi Hotspot -wifi-> Apple-Device == fluctuating pings
Though I tried different APs the last scenario shows that the AP has no influence on this issue because there is no AP in that scenario
Also, pings are only fluctuating in the direction of the Apple device.
My guess is that Apple puts its wifi modules in some kind of energy-saving mode causing them to receive packets only at certain time frames. Another test backs up my assumption, use the following command:
ping -c50 -f IP-of-apple-device
The first packet shows a high delay, but all following packets are very very fast, as they should be. Hence, as soon as we receive a packet we wake from energysaving and can handle further packets immediately.
Unfortunately, I have no solution for this problem as only Apple can change their wifi implementation. Nevertheless, I hope I brought some light in the dark
Cheers,
Nico
Edit:
Try this: ping -c50 -i 0.2 IP-of-apple-device
And vary the 0.2 value. This is the delay between consecutive pings. For me, 0.2 is OK, but 0.4 already yields fluctuations.
