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Weird HTTP throttling issues with newer firmware with QoS off!

Discussion in 'ASUS AC Routers & Adapters' started by aalba86U, Aug 19, 2018.

  1. aalba86U

    aalba86U New Around Here

    Aug 19, 2018
    [Moderator: please move this to AC thread if appropriate]

    Hi SNBers,

    I am having very weird TCP(HTTP/HTTPS) throttling issues (RT-AC68U, RT-AC86U) for sustained downloads (wget,curl) since the last 3-4 months with the latest set of firmware. Certainly has this issue.

    1. I update firrmware regularly and observed this starting about 3-4 months ago

    2. 86U(also tried 68U) in Wireless Router mode connected directly ISPs fibre modem with QoS turned off, the subscription is 1Gbps. Test site is a local fast HTTP mirror: the download starts fast > 50Mbps then drops to several hundred Kbps to 0 bps.

    4. Restarting the download repeats the same behaviour. All browser downloads/wget/curl show this behaviour.

    5. Strangely speedtest.net shows good speed > 800Mbps (Maybe speedtest.net is not TCP/HTTP based?)

    6. When I turned the RTs into AP-mode and used an old Netgear 1Gbps wireless router (for the Internet router part) I am getting great sustained download speeds consistent with 1Gbps

    7. When I connect my computer to the ISP modem directly I also get great sustained downloads consistent with 1Gbps

    8 . When I use a UDP-based VPN through the RTs(in router mode) I am getting good download speeds consistent with 1Gbps. Therefore my conclusion is that the router is doing some weird/unexpected throttling at TCP/HTTP. For now I have to downgrade my RTs just as APs and repurpose an old Netgear as the Internet router :(

    Any advice, recommendations would be appreciated.:rolleyes:

    P.S. I see that 32738 is out for RT-AC68U (but not yet for my usual primary node RT-AC86U). I will try 32738 for 86U - hopefully that will solve the TCP/HTTP issue...)
    Last edited: Aug 19, 2018
  2. ApexRon

    ApexRon Senior Member

    Jun 17, 2018
    Apex, NC
    To sum up your troubleshooting, correct me if I am wrong, it appears that your issue only occurs when the AC86U is directly connected to ISP modem. If so, this could be a physical connection or an auto-negotiation issue. Unfortunately, you can't configure the ethernet port on the ASUS and I suspect the same is true for the ISP router. I would recommend trying a different ethernet cable (CAT-6 would be best).

    I have found the Syslog in the AC86U either provides too much misleading information or nothing at all relevant but anyway for your situation anything of merit in the log?

    Another clue is the CPU utilization, what is your's when it fails compared to when it works?

    Final question: You state that you have QoS turned off but there are other traffic shaping options. Are they off as well?
  3. aalba86U

    aalba86U New Around Here

    Aug 19, 2018
    1. Changed the cable as suggested by @ApexRon.
    2. Upgraded firmware
    Now the TCP/HTTP throttling has gone away so things are back to normal.
    ApexRon likes this.