Internet really slow after upgrading to Lion from Leopard!

As noted in previous posts, I have been having non-wireless internet slowdown and lagging on some but not all sites with 10.7 that was fized compeltely by applying an old hack to restore DNS-related files from 10.6.4. DId the 10.7.1 updae and I am not somewhere in the middle. Not as bad as before but some sites horribly lag or do not ever load. Very lame.

I noticed a similar connection to disk I/O. While copying a large file via the command line my network connection would stall or timeout. If I paused the file transfer, it sped up (but was still slower that 10.6). Then resuming the transfer would again slow it to a crawl.

I tried the upgrade to 10.7.1 and still get the issue.

In my case the problem was router firewall/DoS protection related.

I've been plagued with unreliable connections since Lion and after a weekend away using someone else's WiFi realised that I wasn't getting the same problems using their router. When I got home I checked my own router logs and found a lot of "SYN FLOOD ATTACK" entries relating to my MacBook Pro.

A quick search around (once I got the WiFi working again!) lead me to this http://forums.mozillazine.org/viewtopic.php?f=38&t=883835&start=0 which explains how an over sensitive router security setting can make it think something untoward is happening and kill off the connection.

In my case the router's "Maximum incomplete TCP/UDP sessions number from same host" setting was at the default setting of 10, after increasing this to 30 (some people have set it as high as 50) Safari demonstrated a very noticable improvement in performance and reliability. To date it hasn't faltered and the router is no longer logging "SYN FLOOD ATTACK".

I'm speculating that Safari (or Lion in general) is substantially more aggressive when accessing the Internet/network and this is upsetting some routers and making them close down connections (I think mine kills it off for 300 seconds by default) believing that it is involved in a DoS attack.

I'm not claiming to have the definitive answer, but the simple router configuration change I made has made a big difference for me and if you've not tried it yet then why not give it a go?

Message was edited by: Coupaman - Corrected confusing typo

Coupman: What router are you using? I have a Linksys RV082 which is relatively sophisticated but there is no setting to adjust any of these settings. Thanks!

Neurorad: It's an old cheap rebadged belkin. If you can't adjust the settings mentioned in the link I posted then is there anyway you can disable the router's firewall even if it's only temporary while you see if it makes a difference? I'm afraid I'm not familiar with your particular router.

I might try and look at different routers' settings tomorrow and see if there are any other similar settings that may have the same effect. If I see anything potentially significant I'll post it back here.

Cheers

Hi again Neurorad: Just had a look at the manual for your router. In the router settings there is a "Log" tab. You can enable router logging there and also view the entries it has logged. If you enable this you should be able to see if the router is logging Syn Flood events the timestamps of which will coincide with the network hangs on your Mac.

If this is the case then you can disable the router firewall on your "Firewall" tab. Save the change and restart the router and also your Mac (just to be sure). If this cures the problem then you can re-enable the firewall on the router and then disable the "DoS (Denial of Service)" firewall option only instead. This should still work but give you the benefits of most of the firewall other features on your router.

You may want to leave logging enabled for a couple of days (if you do not have it enabled by default) just to keep an eye on events and see if it has sorted the problems.

For me the types of sites that seem to cause problems like this are the data heavy ones such as Google Maps or pages with a lot of individiual images on them to download.

I can't issue any guarantees but if it's not an avenue you've previously explored then worth a try.

Cheers

*

Message was deleted by: Coupaman : Posted in error

Coupaman - thanks for your help. I am going to get rid of the LinkSys router entirely since there are other reports of incompatibilities. Your thread does make the most sense.

Hello all,

After spending time with Apple Support today I have isolated my problems to router related issues as well. My problems stem from some faulty network ports which I didn't pick up until spending time going through things methodically.

Steps that might be useful for you all, I also had multiple machines available which helped. This will also be dependant on each setup.

1. Test with both machines plugged into the network

2. Test both machines via wireless.

3. I also reset my routers connection and reconfigured it from scratch

4. Test individual ethernet ports on a wired router (if it has more than one).

Thanks for all other suggestions, hope you all end up getting there, in my case I am happy that I know the reason but sad I have to fork out $$$ for a new router.

Andrew

Thank you for your suggestion! I have just attempted to follow your directions and hope that

I will no longer have the same problem.

You have to remember that iPhones and iPads run iOS, whereas your Mac is running Mac OS X. Even though iOS is based on OS X, it's not identical. That's probably why you were seeing differences between the devices. Now, if you had two Macs, then it would be an apples-to-apples comparison of the connection performance.

Most likely, replacing the modem fixed things up. Modems can go bad over time, and the Mac would put far greater demands on it than the iOS devices.

the only problem I have with that theory is that I have an iMac i7 (mid 2010) and an iMac i5(mid 2011), both running wireless off a linksys g router. The i5 came with Lion preinstalled. It consistently gets download speeds of aroun 20-22Mbps. My i7 was in the 18Mbps range (and is actually just down the hall from the router, whereas the i5 is in the basement) when I had Snow Leopard. After upgrading to Lion, my i7 sunk back to 5-10Mbps speeds. So it seems more the upgrade to Lion is the issue vs just Lion itself.

The Apple tech had me reset the NVRAM and that seemed to help temporarily (while he was on the phone, of course). Afterwards it went back to the slower speeds.

Still puzzling.

Mark

Same here, updated to Lion, the whole internet experience has degraded.

From 9.8mb/s before to 1.20, 2.50mb/s. And I have reset the router and the modem, and I tryed with wi-fi and cable ethenet, no difference at all.

On my previous edition MacBook Pro, alluminium 2.33 Ghz Intel Core 2 Duo is going ok, and running 10.7.2 and safari 5.1.1 too.
This is a unibody 2.8Ghz Intel Core 2 Duo.

Why nobody from apple is answering?

p.s. the customer service in UK let you wait for 12 minutes before answering the phone...

Then a power reset is not all what we need...

Guys, I am buying a PC is it goes on like this

I had applied a previously described patch that restores hidden DNSResponder files to those of 10.6.5 with great success through 10.7.1, Prior to 10.7.2, I totally revamped my network and got rid of a Linksys/Cisco router (RV082) that was attached to my cable modem. The network is now compeltely Apple Airport. NO slowdown with 10.7.2. Other threads have described problems with Linksys/Cisco routers and my experience appears to confirm this. No problems at all, with the full 50 MBps available to my comptuers.