Gigabit internet with Asus AC68U running slow

[Dixit]

Let me try to explain my issue. I have an Asus AC68U running the latest stable Merlin firmware (378.56). I just switched over to ATT Gigapower (gigabit internet via fiber to your house). When it was installed about 8-9days ago, they installed an ATT Gateway (like a modem, its a PACE 5268AC) but its also an all in one, takes the phone (if you subscribe to that service), also takes Coax for your TV, and also provides AC 4x4 wireless and 4 gigabit ports. So its really an all in one wifi router, with phone (RJ11) and Coax. Very impressive box. When they first installed it, running a speed test with a fairly high end desktop directly connected via one of the gigabit ports, I was getting around 850/950Mbps (down/up) off the ATT speed test server here in Tucker GA area.

I initially wasn't going to use the Asus router anymore except noticed the ATT Gateway's configuration page had a lot of features except one key one I needed, Static Route. I have a 2nd network via PTP wifi link to a 2nd building with its own ISP. But we use that PTP link for data redundancy for data we don't want to transfer using the ISP. So I put the Asus in there. The ATT GW has a special feature to allow the Asus to take control and give it the public IP like a standard cable modem would. So I believe there isn't a double NAT situation here. Speed test now on that same server is barely 70/3250 (down/up). So at first I thought great something (either Asus or this ATT gateway) is hampering the speed. So I spent days on that.

Then randomly tried a few other speedtest servers (not an ATT one which was the original one). Im getting now around 650/700 (down/up). So clearly don't think its entirely being hampered as using say a Charter server not to far from where I am is easily getting well over 600Mbps in both directions. However Im still baffled on why the speed got cut bigtime for the same server just cause the Asus is now the middle man on this? Id love to just use the ATT GW straight up, but without a static route feature on it, Im screwed in that sense.

Any idea on why this is happening?

Dixit

 

[Dixit]

Here some speedtests from just now with the Asus behind the ATT Gateway. These are done off my high end desktop (corei7, 16gb ram, SSD) connected via Gigabit to the Asus.

Now here is the same server, same test, except using now Charter's server which is also close by.

Clearly the download sideis almost 10x faster on Charter's compared to ATT even though Im on ATT. When we originally had this desktop directly connected to the ATT Gateway, it gets in the 800Mbps down and 900Mbps up range.

Dixit

 

[coxhaus]

The ATT device is a gateway device not a router. A gateway device does not route, it only performs NAT. That is why you can not enter a static route. You need a router for that.

 

[Dixit]

So I figured this out. Tried another machine hooked into the same Asus router , that machine was easily getting in the 700s both ways on the ATT Speedtest. So tried the original server again, same issue, still barely 70 down as the speedtest shows. So at this point knew it was down to the server. However remember I mentioned that server pointed to Comcast or Charter speedtest easily gets much more download so its not the link (like the ISP or even my LAN/Switch) in any way.

Tried to update the NIC firmware, got no change. BTW its a Windows Server 2012 box. So then ran across a cmd line feature for the NIC for windows and turns out it fixed it. It all had to do with ECN Capability.

Here is a link that shows how to enable/disable ECN
http://social.technet.microsoft.com/wiki/contents/articles/20204.how-to-enable-and-disable-explicit-congestion-notification-in-windows.aspx

Basically first ran the command of:
netsh interface tcp show global

This shows all the hidden features of the NICs for Windows. Shows whats enabled/disabled/auto

Then ran the command to disable ECN:
netsh int tcp set global ecncapability=disabled

Once I disabled it, I ended up on that same original problematic machine getting 800/950 on the speedtest (down/up) using the original problematic ATT speedtest server. So all is good now.

ECN is normally used for large networks/businesses. Not much use in my opinion for a home network.

Here is the latest speedtest after I disabled ecncapability.

 

[Skho]

@Dixit Thanks for the detailed walk through. I am running into the exact problem. I am much newer to all this advance networking. But I did follow your method (e.g., check for ECN capability) but I'm still seeing less 600 down and 100+ up. Very different from the 950+ down the tech was showing me on their fancy top end dell.

I'm also using the same equipment as you (e.g., my own router RT-AC68U, and they gave me the 5268AC PACER [from a fiber optic company called Sonic out in San Francisco]). Do you have any idea what else could be driving this?