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taylor85345's avatar
taylor85345
New Contributor II

Does Cox artificially favor Speed-Tests? Real-World speeds slower than SpeedTest results.

I am on the Internet Preferred 150 plan, and in the last few months I've been having issues with my transfer speeds. Based on my plan, I should be getting 150 Mbps down / 10 Mbps up, and results from speedtest.com or fast.com always show my connection meeting or exceeding those transfer rates with speeds around 175 down and 10.5 up on average.

The problem is that these speeds are not holding up under sustained real-world loads, particularly on the Upstream side. I operate a Plex Media Server in my home and routinely stream from it throughout the day. In the past I was able to reliably stream at 8 Mbps, but in the last couple of months I have had severe buffering issues and had to bump down to 4 Mbps or less to get a stable stream. I have backed this up with a series of iperf3 tests, all of which show an initial transfer speed of 10 Mbps, which almost immediately drops to 4-4.5 Mbps after about a second of testing. Regular large transfers to other cloud storage services tell a similar story.

For the record, I disconnected my router and did a wired test with my laptop connected directly to the modem, which did show an overall increase to 5-5.5 Mbps in iPerf3, but that is still well below the service I pay for. Unless there is a problem with my modem (it has not given me any noteworthy trouble to date), I can't think of any hardware bottlenecks on my end that would limit my speeds, so it really feels like Cox is under-delivering my internet service and masking it by prioritizing speed test traffic.

10 Replies

  • taylor85345's avatar
    taylor85345
    New Contributor II

    Here are consecutive results from speedtest and iperf3. I am well aware that the iperf3 server is significantly further away. I have run speedtests to a server in the same Fremont, CA data center and seen results consistent with the Phoenix results, I just couldn't find the server ID to enter in Speedtest-cli for purposes of this comparison. I'll also now that today's iperf results are the best I've seen yet. 

    taylor in taylor-kbox in ~

    ❯ iperf3 -c iperf.scottlinux.com -4

    Connecting to host iperf.scottlinux.com, port 5201

    [ 5] local 192.168.0.153 port 32972 connected to 45.33.39.39 port 5201

    [ ID] Interval Transfer Bitrate Retr Cwnd

    [ 5] 0.00-1.00 sec 2.75 MBytes 23.0 Mbits/sec 12 52.3 KBytes

    [ 5] 1.00-2.00 sec 730 KBytes 5.98 Mbits/sec 8 17.0 KBytes

    [ 5] 2.00-3.00 sec 730 KBytes 5.98 Mbits/sec 2 26.9 KBytes

    [ 5] 3.00-4.00 sec 730 KBytes 5.98 Mbits/sec 8 11.3 KBytes

    [ 5] 4.00-5.00 sec 365 KBytes 2.99 Mbits/sec 5 11.3 KBytes

    [ 5] 5.00-6.00 sec 365 KBytes 2.99 Mbits/sec 6 11.3 KBytes

    [ 5] 6.00-7.00 sec 365 KBytes 2.99 Mbits/sec 6 11.3 KBytes

    [ 5] 7.00-8.00 sec 730 KBytes 5.98 Mbits/sec 3 15.6 KBytes

    [ 5] 8.00-9.00 sec 365 KBytes 2.99 Mbits/sec 5 18.4 KBytes

    [ 5] 9.00-10.00 sec 365 KBytes 2.99 Mbits/sec 8 9.90 KBytes

    - - - - - - - - - - - - - - - - - - - - - - - - -

    [ ID] Interval Transfer Bitrate Retr

    [ 5] 0.00-10.00 sec 7.38 MBytes 6.19 Mbits/sec 63 sender

    [ 5] 0.00-10.03 sec 6.64 MBytes 5.56 Mbits/sec receiver

    iperf Done.

    taylor in taylor-kbox in ~ took 10s

    ❯ speedtest

    Retrieving speedtest.net configuration...

    Testing from Cox Communications ([IP REDACTED])...

    Retrieving speedtest.net server list...

    Selecting best server based on ping...

    Hosted by Cox - Phoenix (Phoenix, AZ) [DISTANCE REDACTED]

    Testing download speed................................................................................

    Download: 164.75 Mbit/s

    Testing upload speed......................................................................................................

    Upload: 10.63 Mbit/s

    • taylor85345's avatar
      taylor85345
      New Contributor II

      Alright, status update on this. In the interest of eliminating as many external variables as possible I connected to a public "Cox WiFi" hotspot hosted by one of my neighbors, and I was able to achieve stable 10Mbps uploads from my Plex server at home streaming to my phone. Results were similar for other workloads, meaning that there are no bottlenecks on my home network or the local Cox infrastructure. Since streaming is consistently slower on non-Cox networks, I'm thinking a bottleneck further up the chain and not directly related to my personal hardware or Cox internet service. While the issue still exists, I am going to consider this effectively solved as any solution would be well above my pay-grade.

      • this_dude's avatar
        this_dude
        New Contributor

        About that hotspot thing. I asked a chat rep if my modem was broadcasting a wifi hotspot. He said no. Is there any way I can check if that's true or not? They keep charging me for extra data so my $109 plan comes out to around $200.

    • JonathanJ's avatar
      JonathanJ
      Former Moderator
      @Taylor85345

      Are you speed test results based on being hardwired directly to the modem, router, or wireless? In regards to internet speed, third party speed test services are off of Cox's network and may not provide an accurate picture of your speed experience on Cox's network. These tests do not measure only the speeds that the Cox network delivers, but they also demonstrate how long it takes to download/upload data across many elements of the internet connection, including the Cox network, the public Internet, the network the speed test service is connected to, and your home network, devices, and browser settings. However, I believe they are still useful and should return results in the same ballpark as the Cox Speed Test Tool. I’m happy to troubleshoot with you so we can further investigate the speed problems.


      Jonathan J
      Cox Moderator
      • taylor85345's avatar
        taylor85345
        New Contributor II

        Hi @jonathanj,

        The specific test results that I posted here were from a desktop machine with a wired connection to my router. However, as I mentioned in my initial post, I performed a similar round of testing with my computer hard-wired directly to the modem. While the results were marginally better, the 1mbps difference was small enough to be attributed to standard network overhead.

        I have run numerous tests on speedtest.net, specifically choosing servers which were geographically distant and NOT hosted on the Cox network, and results achieved through speedtest.net and fast.com consistently show results in the neighborhood of my plan's 150 Down/10 Up rates. I also specifically ran several tests to the BayNIC speedtest server in Fremont, CA, which is hosted in the same Hurricane Electric datacenter as iperf.scottlinux.com, the public iPerf server that I have been using to run my iperf tests.

        Regarding iPerf and iperf.scottlinux.com, that server is confirmed to have at least 1 Gbps upstream and downstream, and in running off-site iPerf tests outside of my home network (i.e. via the T-Mobile network and my work's enterprise network)  I have consistently been able to achieve upstream and downstream results to that server well above what I see at home, indicating that there are no bottlenecks on the server side. 

        Note that iperf is just the best tool I have found to specifically test speeds outside of the widely used speed test platforms, but the upstream results I see via iPerf are consistent with the transfer rates I see with real world loads such as Plex Media Server streaming, syncing to Google Drive, syncing my devices remotely via Syncthing, or performing large file transfers over an OpenVPN connection. Under all of these loads, my upstream transfer rates are consistently in the range of 2.5-4.5 Mbps up

        I should also note that neither I nor the Cox support rep that I spoke to on the phone have found any evidence of packet loss on my modem, and in the past I have been able to consistently achieve 8-10 Mbps upstream using my current hardware configuration, so I am increasingly convinced that this is not a hardware issue on my end.

        If you have any additional suggestions for further troubleshooting, I am all ears.

    • felicityc's avatar
      felicityc
      New Contributor

      they do not artificially favor any speed test. however, the speed test they encourage (the one on the website) is to their own servers, which is one of the most direct node pathings. it is a bit disingenuous on their part. 

      Go to speedtest or ookla or dslreports and set the server manually to literally anything that isn't a Cox hosted server, and you will see the real world slowdown by distance and node hops. 

      "The problem is that these speeds are not holding up under sustained real-world loads, particularly on the Upstream side. I operate a Plex Media Server in my home and routinely stream from it throughout the day. In the past I was able to reliably stream at 8 Mbps, but in the last couple of months I have had severe buffering issues and had to bump down to 4 Mbps or less to get a stable stream. I have backed this up with a series of iperf3 tests, all of which show an initial transfer speed of 10 Mbps, which almost immediately drops to 4-4.5 Mbps after about a second of testing. Regular large transfers to other cloud storage services tell a similar story."

      This sounds like your networking hardware is overheating, or more likely, a line in the ground got shifted somewhere and it cut one of the up lines. If you are running a media server then overheating is very likely, however. 

      • taylor85345's avatar
        taylor85345
        New Contributor II

        Thanks for the suggestions. I have solid hardware in the chain, and I routinely monitored thermals and cpu usage on both my Media Server PC and my Router throughout my testing process, and neither were particularly taxed by the workloads or had any thermal issues to speak of..

        As I mentioned in my follow up post a moment ago, I am considering this solved as I was able to achieve proper upload speeds to a local Cox hotspot, validating the performance of both my home network and the local Cox infrastructure.