A network benchmark update

Previously, I’ve posted several Comcast / Xfinity’s benchmarks for our CATV Internet service.  (Click on “Benchmark” topic at right.)




Lately, the IPv6 service seems pretty reliable with my system.  That was a problem for some time.  It may have been a bad interaction between the Comcast plant and my local routers, but it just went away.  It may have been a Comcast reconfiguration that helped us, but it also could have been an Asus firmware update. I am now running ASUSWRT-MERLIN firmware on the Asus RT-N66U router, which I can highly recommend as an expanded and improved version of the Asus distribution.(It cured a long-standing issue with JFFS2 overflow.)


Again, I highlight the DSL Reports speed test, which checks your “real world” network performance, including the dread “buffer bloat”.  Today is Boxing Day (Dec. 26), and DSL-Reports is giving me a so-so report and a good report. Here they are, separated by half an hour:

The variability may be partly due to the speed test’s different selection of test hosts.  But it may be something real about Comcast or the Internet “weather”.  These tests use IPv6, it appears.

For comparison, between these two tests, Comcast’s own speed test shows this:

This is the available speed within the Comcast network, which seems to be the best possible result — not fully representative of what you experience with a random Internet connection — even if the server is fast and well-connected. (Note that the driving distance from Branford CT to Boston is really about 144 miles, not under 50. Go figure.)

Hurry Up Future!

I signed on with Comcast for a couple of years to save some money, but when that agreement is up, I’m sure I will be cutting the cord… DirectTV and Sling streaming options.


The article mentions a cloud DVR service that’s got me excited, too. Having all my videos in the cloud and being dependent on the network would bother me – except that’s basically what my X1 is today.

28 Websites

The North Korea internet only as 28 sites, so maybe you could really surf to the end of the internet there.


IPv6: Things that fix themselves

In a January post, I commented on trying to make the new Internet Protocol (IPv6) work in my household.


Despite some detailed sleuthing, I could not get IPv6 working reliably on my WiFi/Ethernet local area network with its connection to our ISP, Comcast.  The router would give up after a day or so, reporting ICMP6 checksum errors and shutting down IPv6 service.  (IPv4 worked well, regardless.)

I had tried swapping out a lot of my devices, including routers, but nothing seemed to keep the service going for more than 24 hours.  Lacking more elaborate packet inspection tools, I put the whole thing on the shelf.

Now, after 5 months of computer / Internet life, I thought I’d check in again.  What do you know — IPv6 is stable now.  There have been quite a few updates to operating systems, routers, and other components since January, so it’s not possible to say what made the difference.  And Comcast may have secretly changed its service in a way that cured my bug.  (The log still reports bursts of ICMP6 checksum errors, by the way.)

We may never know what happened, and that’s a shame because it is good to know where the weak links are (or were) to help plan future developments.

Meanwhile, laissez les bon temps rouler!  We are ready for the next century.

p.s. This is mainly a hobby activity.  There is practically nothing you can do with IPv6 that you can’t do with the common IPv4.  (You can test your own IPv6 capability here.) Over time, since the IPv4 system is now almost out of available new addresses, new services will have to be provided on IPv6 only.  But that may be a while yet.

What’s Our Next Fight?

We won the battle for Linux, but we’re losing the battle for
freedom.

Linux turns 25 in August 2016. Linux Journal turned 21
in April 2016. (Issue #1 was
April 1994, the month Linux hit version 1.0.) We’re a generation into the
history of our cause, but the fight isn’t there anymore, because we won. Our
cause has achieved its effects.
more>>

IPv6: Light my Fire!

Our IPv6 story continues.  We removed our Asus RT-N66U router and showed that the problem (long periods of dropped IPv6 connectivity) was not in the Asus device.   The problem continued when we went back to the Comcast/Cisco DPC 3941T router, alone.   The Comcast device has very poor facilities for diagnosing network problems or anything that might confuse the general Comcast users.  It gives a log that says there were some problems seen by the firewall and that’s about it.

So we put the Asus device back in operation, switching the Cisco to bridge mode.  The Asus demonstrated the same IPv6 problems as before, but now it was time to scrutinize the log a little better.

We noticed a lot of ICMPv6 checksum errors like the following:

Jan 20 10:20:35 kernel: nf_ct_icmpv6: ICMPv6 checksum failed
Jan 20 10:20:35 kernel:  <0>nf_ct_icmpv6: ICMPv6 checksum failed
Jan 20 10:20:35 kernel: IN= OUT= <1>SRC=ff02:0000:0000:0000:0000:0001:ff6e:d2d3 DST=2601:0183:4002:0987:0000:0000:0000:0001 <1>LEN=64 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=136 CODE=0

They repeat up to once a second, when they start coming. All the erroneous packets originated from the …d2d3 address.  With a little work, we found…

The Guilty Party

The Amazon Fire tablet seemed like a good value at its ~$50 price.  Unfortunately, it appears to be sending the malformed IPv6 packets.  Powering off the Fire (or using airplane mode) cuts the errors, and seems to have stabilized the network.

Kindle’s version of Android gives you very little to adjust, and you can’t shut off v6.  We tried unloading most of the non-Amazon apps just in case one of them was causing the problem, but that had no effect.

Maybe $50 is just too cheap? That would be one moral of this story.

Another moral: Don’t expect a Comcast router to help you fix your network if something goes wrong.

Still slogging on Internet Issues

While trying to understand why IPv6 is (still) not reliable on my Comcast / Xfinity service, I rediscovered DSL Reports.  This is a great place to go to get your technical / support questions answered for DSL or Cable connections.

I have a post in for Comcast’s attention.  Meanwhile, I ran the nice speed test tool, which gave me the highest-ever speed report.

Comcast IPv6 – Asus RT-N66U Troubles

We were a dual-stack household — for a while.  Comcast is one of the leaders in the evolution of Internet services from the old IPv4 to the new IPv6 service.

The old IPv4 network has run out of easy-to-allocate IP addresses (the numerical kind, like 130.132.20.1, that are roughly equivalent to your telephone number).  Among other advantages, the new IPv6 allows for gazillions of new addresses.  It will be a key enabler of the new “Internet of Things” that you may have heard about.

As this transition occurs (slowly, as there are so many v4-only systems installed), many of us will need to operate “dual stack” systems that are capable of using both forms of addressing.  Any modern desktop PC (Windows 7 and onward, Linux, etc.) already knows how to do this.  The weak link for many users will be their Internet Service Provider (ISP) that will have to reorganize itself to provide IPv6 services.  So, the good news — our Comcast system does offer IPv6.

We were able to run dual-stack pretty well with the gateway device that Comcast rents us, a Cisco DPC-3941T.  (We need their gateway, because we use their VOIP telephone service.  That’s another story.)  Our Linux operating system (and probably Windows, too) will prefer to use IPv6 over IPv4, when a given Internet service offers both.  Google sites all seem to offer IPv6, for example.

But it wasn’t going to be that simple for us, because the Cisco gateway is “crippled”. Comcast seems to have decided that a downgraded gateway can offer more security with fewer support issues for the 99% of customers who have simple needs.  It does not support a moderately complicated home network, like ours, where you might want to use specific IP addresses, firewall setups, etc.  In this situation, Comcast recommends that you operate their gateway in a non-routing mode and that you attach your own WiFi router that will be more configurable to local needs.

Enter the Asus RT-N66U.  On paper, this looks like a fine choice for us, offering very good dual-band WiFi and lots of configuration control.  With its standard setup (IPv4), we’ve had no problems.  (The VOIP service stays with the Comcast gateway.)  When we enable IPv6, things worked well, too, despite the lack of documentation or help files from Asus.

Worked well, that is, for a number of hours.  After a time, the IPv6 service just stopped.   The good news is that Internet service continued with only minor delays using the old IPv4 protocol.  The bad news is that IPv6 isn’t reliable using the RT-N66U.  It starts up again if you reboot the router, but it will eventually die with the same symptoms.

According to the router system log, the router starts encountering ICMPv6 checksum errors.  After some substantial number of such errors have been reported, the router decides to drop IPv6 entirely.  That’s my interpretation, anyway.  Where the errors arise is not clear.  It could be the Asus router itself, or it could be an interaction with the Cisco device, or something even further upstream.

I have tried all variants of IPv6 setup that I could think of — enabling/disabling DHCP, response to Internet pings, etc.  Sometimes IPv6 seemed stay up for longer, but eventually it always dropped out.

So despite the initial excitement of operating a cutting-edge dual-stack household, we are back to plain old IPv4 for now.  Maybe someone will suggest a better router configuration, or maybe we will get a firmware update that fixes things.  Meanwhile, we’re coasting along on tried and true IPv4.


Note added: To keep things in perspective, there is no great reason to run IPv6 at the present time.  It’s just a game, until a significant number of services begin to be offered exclusively on IPv6.  That will happen eventually as the address exhaustion begins to be felt, but for now essentially all IPv6 services are also available via IPv4.

High speed, high cost: it’s Comcast!

Comcast (dba Xfinity) is giving us tons of Internet speed these days, at least in our corner of Connecticut.  They gave us a new gateway that is now provides the results shown to the right.  Our current service started out at 50 Mb/s, but has more than tripled with little price increase.

That’s all good, but the downside is that they are charging something like $1 per month per megabit per second. High speed is occasionally useful for downloading big files, but we could survive on a fifth of what they are giving.  I suppose a big household where 5 people are all looking at their own HD videos would need this bandwidth.  But that’s not us!

The question is whether a downgrade of our “triple play” service would put us at a more reasonable price / performance point.  We’ll see.

My home LAN gets used for special ham radio work, servers, and software development, so I need to set up DHCP with some assigned addresses and tailor the network in other ways.  Since Comcast has seen fit to cripple its gateway to prevent me from doing this, I’ve added a proper Asus RT-N66 WiFi router that runs off the Comcast unit operating in “bridge” mode.  The Asus unit is very nice, including IPv6 service, as you see above.

IPV6 ready

Comcast has blessed me with a working IPv6 connection, viz http://test-ipv6.com/:

What does it mean?  It means that we’re all set when some of the Internet service providers are forced to use the new IPv6 addresses when there are really no IPv4 addresses left. (That’s likely to begin soon.) It also means I’m behind the curve technically.  I understand IPv4, more or less, but v6 seems very different and a lot more complicated.

Comcast also upgraded us to 100 Mb/s download (from 50) without fanfare.  That’s nice, but I’d rather have had a 50% price cut.

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