Mid-2013 13" MacBook Air high latency with E4200 router
When my new mid-2013 MacBook Air (i7/8 GB/512) connnects to my Cisco E4200 router, it gets terrible latency. If I ping the router, I get massively differing latencies from successive pings, between 1 and about 200 ms. Rebooting the router fixes the issue briefly, but it comes back after a few minutes.
This issue only occurs between this exact router and this MacBook Air. Any other systems have latency consistently under 1 ms when connected to this same router (two 2011 MacBook Airs, 1 2010 MacBook Pro, a Dell, and a Toshiba system). My 2013 MacBook Air also has normal latency (< 2 ms) when connecting to an older router I have around. The Air also works fine if I wire it directly into the router, however, the issue does not seem to be interference. It happens on both the 5GHz and 2.4GHz bands, regardless of channel used, and regardless of distance from the router - the symptoms are identically in all cases.
The issue also does not occur if I boot the Air into Windows 8 - pings are always under 1 ms, so it looks like we're talking a software issue. I've tried creating a new user profile and dumping all network preferences that I'm aware of, but it made no difference. I'm wondering if it's a very particular driver issues on the Mac side, although I find it very weird that rebooting the router temporarily fixes the issue (toggling wifi on and off has no effect). I've tried updating to the latest version of the router firmware, but it made no difference.
MacBook Air, OS X Mountain Lion (10.8.4), Mid-2013 13" i7 / 8 GB / 512 GB