Why in OS X Mavericks internet is so slow?

Thank you, thank you, thank you, codybrianna! I've been fighting this for days. All fixed now!

OSX Maverick

iMAC 24-inch, Early 2008

Airport Extreme 2

10 yr old Terayon modem from Time Warner

Avg download speed over wireless had degraded down to 2M. Tested with iMAC and PC laptop. Used to be 8M. Cable service supposed to be up to 15M.

Using DSLREPORTS.COM java Speed tests with Safari as our browser on the iMAC.

Connected ethernet directly to old modem with PC laptop and got consistent 11M downloads.

Changed modem to new Netgear CMD31T.

This increased our iMAC wireless download speeds to approx 5M but PC laptop jumped to 10M over wireless. We definitely needed a new modem.

We then tried chattphotos suggestion of using DNS server 8.8.8.8 on the iMAC and gained another 2M.

Now downloading at 7M.

We then loaded Google Chrome and DSLREPORTS.COM speeds went to 8MB.

We then loaded Firefox and now get a consistent 14M. Jeez!!! We’ll take it! What a journey!

Thanks for everyones suggestions on this thread.

Summary:

New cable modem,

Changed DNS to 8.8.8.8

Switched from Safari to Firefox.

I was having trouble with slow (wired) internet and also timing out to my outgoing email server. My IT guy suggested to change the name of my computer to eliminate spaces and punctuation. This worked wonders for me.

You are the man!

I upgraded from Lion to Mavericks.

Currently I'm on OSX 10.9.3 and I had indeed corrupted network preferences.

Your solution worked flawlessly, I can use my macbook again!

I unplugged my ethernet, then opened a terminal and typed:

cd /Library/Preferences

[Enter]

tar -cvzf ~/system_configs_backup.tgz SystemConfiguration

[Enter]

sudo rm -fr SystemConfiguration

[Enter]

Then I restarted and after boot I plugged in the ethernet.

Everything is working fine now!

N.B.: in the terminal command with tar, ~ is like writing /Users/your_user_name

Thank you!

If you're going to change the radio channel and have neighbours, you want to make sure to stay on channels 1, 6 or 11 though. Any other setting will create interferences due to overlapping. For instance channel 9 will interfere with both 6 and 11. Bad for you and for the networks you're jamming...

Hey guys,

I have had the same problem, after reinstalling the Mavericks.

But after optimizing WiFi Channel in Mac OS-X, watched the video in the link below,

now it seems the WiFi on my mac works like use to.

https://www.youtube.com/watch?v=Lrr-dgSNCVw

Check it out!

thx changing channel worked for me

If you're using Wifi, and have an Apple keyboard or mouse, try disconnected bluetooth and see if it speeds things up.

Unbelievable, the Bluetooth for those devices causes interference with the WiFi. I've had to stop using mine because of this..

I've had this issue for a good part of this year and have now finally found a solution on this page, which is also the selected answer in a different post (Mavericks and Failed ARP causing network drops!). The bug seems to be related with ARP unicast requests, which can be disabled by applying:

sudo su
touch /etc/sysctl.conf
echo net.link.ether.inet.arp_unicast_lim=0 >> /etc/sysctl.conf
chown root:wheel /etc/sysctl.conf
chmod 0644 /etc/sysctl.conf

and then rebooting. Please find more background information in the first link or in my answer on a corresponding StackExchange question.

I had a problem with slow internet.

Check out "netstat" (or the Network Utility) and look for an excess number of tcp connections especially in the other than ESTABLISHED state.

IF this symptom shows up, then the problem is probably your DHCP/NAT server.

I had a Ubee cable modem. Once I figured out how to get it into bridge mode and move the DHCP/NAT to my airport express, my internet became responsive again.

Thx Boxx.... helped me out!