As first report byAnandtech ’s Anand Lal Shimpi , the newMacBook Air , which is outfitted with an 802.11ac Wi - Fi adapter , is radically dense when it get to remove real - world files over a wireless link . In my own testing , I clocked the file - transfer throughput at a meagerly 140 mbps at nigh range ( eight feet tell apart the router and guest ) while copying a 10 GB ingathering of small files from a new MacBook Air to an old MacBook Pro on the same web ( both political machine were outfit with SSDs ) .
Lal Shimpi conjecture that OS X is the right way dynamically resizing the TCP window size when IPERF is running , but not when actual files are get over the connection . TCP ( transport control communications protocol ) requires the receiving twist to periodically recognize the receipt of data , and TCP window size set how much data can be sent before the sending equipment must stop and look for that acknowledgment . If the acknowledgment is n’t received , the sending gadget will then resend the data . The larger the window , the fewer the acknowledgement and the quicker the data transfer .
I useAccessAgility ’s WiFiPerf — a graphical front - end to IPERF — to appraise TCP throughput . Using the unexampled MacBook Air , I reach amphetamine in surplus of 450 megabits per 2nd ( mbps ) at close range of mountains ( nine base from the router , with no walls in between ) and 65 mbps at my furthermost trial location ( 65 fundament from the guest , with three insulated interior walls in between ) .
( Full revelation : I ran the WiFiPerf benchmark at my home lab , and the file - transfer of training trial run in the Macworld Lab a few days later . )
Apple is aware of this problem , but declined to provide details as to whether active TCP window sizing is indeed the culprit or when Apple might have a answer . Thisshouldbe a relatively easy fix for Apple .
