Gigabit Ethernet Troubles

[RcktMan77]

I'm looking to see whether the community has any networking experts available to help resolve an issue I'm having with OS X. I recently signed up with AT&T's Gigapower service which is roughly a 1Gbps symmetric internet connection. Upon activating the service, I noticed I wasn't getting the guaranteed speed on my Late 2014 Retina iMac. Instead speed tests were showing download speeds ranging between 250 and 450 Mbps and upload speeds limited at 60Mbps.

AT&T sent a couple of technicians to confirm that their service was working as advertised. They plugged an older Dell laptop running windows directly to the modem and sure enough were seeing the advertised transfer rates of around 800-850 Mbps for both upload and download. In so doing, they ruled out any issues with the ethernet cable my iMac was using by plugging the same ethernet cable into their Dell laptop. This prompted me to boot into Windows via my BootCamp partition to run a speed test using the same iMac, and sure enough my iMac running Windows 8.1 was getting 950Mbps transfers. I will also note that I have a 2015 Macbook Pro which I plugged in via ethernet and it has the same slow ethernet transfer speed while in OS X; thus, why my suspicions are revolving around the OS as the culprit.

I called Apple's support line to see if they had a solution, and they weren't willing to troubleshoot the issue beyond having me reset the PRAM, boot into safe mode, and re-run the speed tests. Their suggestion was to blame AT&T's service, which I'm not apt to do at this point. In any case, any support from Apple on this issue doesn't seem to be an option.

The Hardware tab in the Advanced settings of the Ethernet network configuration shows that everything is being configured Automatically with the following settings:

Speed: 1000baseT
Duplex: full-duplex, flow-control
MTU: Standard (1500)

I switched the configuration once to configure it manually while changing the MTU setting from Standard (1500) to Jumbo (9000) to see if that made any difference, and unfortunately it didn't. I would welcome anyone else's suggestions or any other similar experiences related to this issue if anyone has them.

 

[nebo1ss]

Are you connecting your Computer directly to the ATT router. I have Gigabit Internet in my house and i regularly see 800Meg down and 850Meg up I am using a Macbook Pro late 2008. During the busy part of the week I might see speed reduction down in the 400 range but my up speed is always higher than the down speed. Have never seen anything like the 60Meg you are reporting. You should try another computer perhaps you have a faulty Ethernet port.

You might want to try an alternative browser to Safari to do your speed test.

 

[RcktMan77]

Are you connecting your Computer directly to the ATT router. I have Gigabit Internet in my house and i regularly see 800Meg down and 850Meg up I am using a Macbook Pro late 2008. During the busy part of the week I might see speed reduction down in the 400 range but my up speed is always higher than the down speed. Have never seen anything like the 60Meg you are reporting. You should try another computer perhaps you have a faulty Ethernet port.

You might want to try an alternative browser to Safari to do your speed test.

So my residence has ethernet jacks in every room one of which is used by the router and another by my iMac. While the AT&T technician was out we connected another of my computer's a 2015 MacBook Pro laptop directly to the router via ethernet, but I was experiencing the same 250 - 450 Mbps transfers. We did try Chrome instead of Safari also, but it didn't change anything. As I mentioned, I don't believe the ethernet port is faulty because the same iMac shows transfers at the full 950 Mbps rate when booted into Windows 8.1, and the AT&T technician plugged his Dell laptop into the same ethernet cable which is being used by my iMac with now degradation in transfer speeds from when he was plugged directly into the router. I'm running OS X 10.10.4 if anyone is curious, but thanks for sharing your experience as that gives me at least one data point that it may not be due to OS X.

Thanks

 

[Significant1]

If you have a switch, Try and check the ethernet speed between your two macs, by copying som big files between them.

 

[RcktMan77]

If you have a switch, Try and check the ethernet speed between your two macs, by copying som big files between them.

A good suggestion. I connected the MacBook Pro via Ethernet to my Time Capsule (which is in bridged mode) and transferred an 826 MB file from my iMac to the MacBook Pro via rsync, and was only seeing transfer rates of ~28 MB/s or about 224 Mbps which is on the low end of what I was seeing via speed test results.

 

[Significant1]

A good suggestion. I connected the MacBook Pro via Ethernet to my Time Capsule (which is in bridged mode) and transferred an 826 MB file from my iMac to the MacBook Pro via rsync, and was only seeing transfer rates of ~28 MB/s or about 224 Mbps which is on the low end of what I was seeing via speed test results.

That is strange and way to slow, but also too fast for 100Mbps connection. It does looks like your Mac's themselves are the source of the problem and not communication with the modem.

I have the same setup and get 100+MB/s when copying between my macs running 10.10.

Since it is both of them, I wonder if you are running som kind of security software scanning your connection or vpn. If it is software related, maybe you can spot a process with high network activity on the network page in activity monitor.

 

[RcktMan77]

That is strange and way to slow, but also too fast for 100Mbps connection. It does looks like your Mac's themselves are the source of the problem and not communication with the modem.

I have the same setup and get 100+MB/s when copying between my macs running 10.10.

Since it is both of them, I wonder if you are running som kind of security software scanning your connection or vpn. If it is software related, maybe you can spot a process with high network activity on the network page in activity monitor.

Ahh, another good idea. I do have Sophos Antivirus installed on both. Turning that off seems to have resolved the issue. Speed test shows transfers at 815Mbps down and 200Mbps up. That's sort of a shame that the Antivirus software is the culprit, but thanks for pointing me in the right direction!