Mac OS X 10.5.2 Special Report: Slow LAN transfers

A number of users have reported that transfers of large files on local are dramatically slower under Mac OS X 10.5.2. MacFixIt reader John Albergo remembered a fix that we noted in our Mac OS X 10.4.9 special report that involves modifying the delayed_ack parameter of Mac OS X's TCP/IP configuration by entering the following command in the Terminal (located in Applications/Utilities):

• sudo sysctl -w net.inet.tcp.delayed_ack=0

then pressing return.

This workaround solved his slow throughput immediately.

"I recalled an issue from around the time of the Macbook Pro introduction, for which the workaround was to force the tcp parameter "delayed_ack" to zero. Suspecting a return or variant of that bug, I tried the workaround on both of my machines and the slowdown has not returned.  I hesitate to declare a cure, but the throughput is rock solid so far, and at the speed I would normally expect.  This implies that delayed ACKs are not being delivered in a timely manner.

"The blogger at this site wrote a small install script at the time to put an item in Startup Items to do the same thing each time you boot up -- making it easily removed when no longer needed."

Index:

• Release Notes an update procedure recommendations
• Determining whether problems are caused by Mac OS X 10.5.2 or Leopard Graphics update
• Downgrading to Mac OS X 10.5.1

• "ACL found but not expected" in Disk Utility
• Active Directory issues
• Adobe application slowness, fixes
• Advice at work
• AirPort slowness, disconnects and more
• Applications fail to launch
• Clicks from speakers
• Finder not starting
• Freezes when using DVD Player
• iCal calendars disappearing
• iPhone syncing problems
• Mail.app issues
• Microsoft Office applications slow to launch
• Missing display resolutions
• Poor Performance: Slow startups; general sluggishness
• Override automatic disk shutdown mechanism
• Parallels problems
• Repair Disk/Permissions to the rescue, again
• Screen savers not asking for passwords
• Slow LAN transfers
• Startup stalls or fails
• System utilities (Cocktail, LCC) must be updated
• Misc. third-party application, device problems (Bluetooth, etc.)
• Time Machine not work properly
• Trackpad, mice, keyboard not working -- reset SMC
• Undocumented fixes
• Wake-from-sleep issues (inadvertent restarts, more)

Resources