Comcast’s Speedtest Now Breaks Out IPv6 Speed Vs IPv4 Speed

A tip from John Jason Brzowski let us know that Comcast’s Internet speed test at now performs speed tests over both IPv6 and IPv4 and shows you the results separately.  This is a public test that anyone can use, regardless of whether you are a Comcast customer or not.  Perhaps obviously, for the IPv6 test to work you need to either have native IPv6 connectivity from your ISP or you need to have an IPv6 tunnel for your network.  Without that you’ll just get a regular old IPv4 test.

Naturally I had to try this out and was quite pleased with the results. I am NOT a Comcast customer so the results are for another ISP. I do have native IPv6 connectivity so this was not tunneled traffic. Here was my test yesterday with the closest geographic server (which may or may not relate to network proximity – I didn’t do much checking on that):

Comcast XFinity Speed Test

Of course I was pleased that IPv6 was faster!  I assume this probably had to do with more congestion on the IPv4 network at the precise time I did the test.  As you’ll see below, IPv6 was not always faster.

For those familiar with these type of speed tests, the test performed two separate upload and download cycles for IPv4 and IPv6.  As you can see from the center of the image a cool feature is that you can get a link to an image that you can then share out to social networks or use in other places.  For example, here is the link to my image:

Now, of course I had to try this multiple times during yesterday to see how the results varied – and as is true with pretty much all of these speedtest sites the results DID vary widely.  Some of the results included:


I tried other servers in other parts of the US and had similar types of variation.

And then to my amusement I tried the test today shortly before writing this post and found that my speed has degraded significantly. Two results from Boston and one from the New Jersey server:


Just to check I tried a couple of other speed test sites and they provided similar results today.  Now the explanation for this drop in my own bandwidth is probably pretty simple.


Today we’re experiencing a major snowstorm here in New Hampshire (and all of the northeast USA) and so all the schools are closed and many kids are at home along with parents who need to be home with them.  So people are undoubtedly streaming more movies, playing more online games and just consuming much more online bandwidth than they usually do during the day.  My Internet connection is through my local cable provider… so it’s shared through my neighborhood, and so there we are.  Tomorrow when everyone goes back to school my daytime speed should increase! 🙂

All comments about snow aside, this is very cool for Comcast to break out the speeds by protocol this way.  They are of course NOT the only speed test out there that does this.  Other IPv6 vs IPv4 speed tests include sites such as  and

Congrats to the team at Comcast for making this available!

P.S. I’d note that Comcast has to be collecting some fascinating measurements out of this effort because they are gathering test results from not only their own customers but also from all of their competitor’s customers who use this test site.  They can then come up with statistics and metrics about the performance of those competitor networks.  A rather brilliant move by someone within Comcast! Now… what would be great for the larger Internet community would be if they could also find some way to perhaps expose some aggregated level of information about what they are are seeing in terms of IPv6 performance across the range of ISPs from people using the site… maybe a topic for a presentation by someone at Comcast at a future event?  (Hint, hint…)

February 5th, 2014 by | Posted in IPv6, Statistics | Tags: , | 9 Comments

9 Responses to Comcast’s Speedtest Now Breaks Out IPv6 Speed Vs IPv4 Speed

  1. Mike Starr says:

    That for pointing us to this site, as you say it’s a great service. I don’t have ISP supplied IPv6, but have used IPv6 tunneling service for a few years now. I was amazed that there wasn’t much of a speed difference between IPv4 and IPv6, due to the overhead for IPv6 packets, which pass through my LAN as IPv6, gets converted to IPv4 and sent to the other end of the tunnel, then converted back to IPv6 again.

    Results at

  2. Jeffrey says:

    Where were you doing the testing from?

    The speeds you show are very, very, very slow.

    Just to give you an idea, my service provider
    (Comcast) here in the United States provides
    me with a high speed internet connection that
    easily hits 120Mbps for downloads, and provides
    a 12Mbps connection for uploads – guess you
    could say it’s an asynchronous (faster on the
    download speed, slower on the upload speed –
    similar to ADSL, but with much higher speeds
    on both downloads and uploads [ the only type
    of DSL that might possibly approach these
    speeds is VDSL2, which can, in theory, provide
    connections of up to 200Mbps total (combined
    download speed and upload speed – to quote
    Wikipedia source: “VDSL2 permits the transmission
    of asymmetric and symmetric aggregate data rates
    up to 200 Mbit/s downstream and upstream on twisted
    pairs using a bandwidth up to 30 MHz. It deteriorates
    quickly from a theoretical maximum of 250 Mbit/s at
    source to 100 Mbit/s at 0.5 km (1,600 ft) and 50 Mbit/s
    at 1 km (3,300 ft), but degrades at a much slower rate
    from there, and outperforms VDSL. Starting from 1.6 km
    (0.99 mi) its performance is equal to ADSL2+.) ] ).
    The only option beyond VDSL2 is to go with a technology
    known as “G.FAST”, which, in theory, could provide a
    total speed of 1Gbps (combined download speed and
    upload speed) – but the standard has not yet been officially
    approved / ratified, with approval / ratification expected to
    take place sometime this month and commercial hardware
    for the standard to be implemented is expected to become
    available sometime in 2015.

    • Dan York says:

      Jeffrey, the speeds I documented in the article were from my home office in Keene, NH, which uses another cable provider (the one that Comcast is seeking to acquire). I have their monthly “Turbo” package which should in theory get me 20 Mbps down. If I wanted to pay $20/month more, I could go up to 50Mbps down… but that’s the highest they currently offer. Glad to see you have a faster connection!

      • Tim says:

        Wow! I’m with Comcast here near Philadelphia, PA and I’m not getting those IPv6 at all. In fact, the test never finishes when running the IPV6 hangs with a 0.08Mbps transfer.

        The IPV4 tests work just fine and I get between 15-25Mbs which is consistent with my “Performance” plan.

  3. TonyW says:

    Great article!
    I was not aware there was a website that keeps up with the Internet standards. Found while look for Comcast speed test. I have to say that I have seen in some areas where when I do a speed test IPV6 is not available. Maybe not all footprint for Comcast High Speed Data will see IPV6, but I am sure IPV4 will suffice in those areas.

    Great website!

  4. Al. S says:

    I’m in Philly with Comcast my IPv4 is 120Mbps for downloads, and provides
    a 12Mbps connection for uploads, my IPv6 is 119.6 and 11.5. My slower connections all using Ethernet are a slow 94.6 and 11.4 Mbs IPV4 and same for IPv6..

  5. tom says:

    I get 48-56 download and 14 ping and 10 upload with Comcast high speed router.

  6. Hurrah! In the end I got a webpage from where
    I can in fact get valuable information concerning my study and knowledge.

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