NTT Flet’s fails in the Covid traffic crunch

NTT FLET’S internet service has been around forever in many configurations, the latest being Flet’s Hikari ‘optical fiber’. I call it flexible fiber because NTT uses the term Hikari when they should not. My Hikari only comes into the apartment building junction box then branches into each apartment with good old cooper wire phone lines and a VDSL modem. NTT calls that Hikari, I don’t.

PPPoE/IPv4 traffic has been tapped out in Tokyo since at least 2017. When I first upgraded from PPPoE/IPv4 to IPoE/IPv6, I saw a pleasant bump in speed with none of the night time internet traffic meltdowns when using PPPoE.

I thought my problems were solved but over time IPoE/IPv6 download speed has slowed down while iPhone NTT Docomo 4G LTE speed has skyrocketed past NTT Flet’s:

A year ago Twitter user shao, who posts wonderful network and payment tech tweets with the deep tech background to back them up, noted that the Japanese Internet Provider Association was in a collective hissy fit with NTT. IPoE/IPv6 junction points to NTT main lines where tapping out and providers needed more junction points, they also wanted IPoE access pricing brought in line with PPPoE and better traffic control. NTT gave internet providers the cold shoulder with ‘we’ll consider it if you do the work.’ The result of that is NTT East/West Flet’s service is seriously slowing down in face of stay home telework, bored kids streaming content and too much online shopping.

As shao notes 4G and KDDI au Hikari nuro service are, so far, unaffected. The strange thing here is that KDDI is simply renting NTT dark fiber for nuro. So yes, NTT has the capacity, but doesn’t seem inclined to put in the effort to share it unless providers do the work, and also pay up. To be fair I think one of the problems is hinted at in a recent annual NTT financial report: a shortage of field engineers and technicians. Somehow it seems fitting that the human problem of Covid is also the human problem of slow internet speeds.

Choosing the right WiFi router for Japan NTT FLETS


My father had WiFi problems in his apartment, too many dead spots for a decent FaceTime conversation unless he stayed tethered near his Comcast Xfinity WiFi box. Like most people my father likes to walk around and talk resulting in broken connections and conversations.

I picked up a Linksys Velop mesh WiFi router set for him while in the USA, set bridge mode on his Xfinity box and plugged in the Velop router. It could not have worked out better. All the WiFi dead spots were gone, my father can FaceTime wherever he wanders. Velop truly ‘just works’ out of the box.

Linksys has been absent from Japan for some time but seems to be using Velop to dip a toe back into the Japanese market. Velop and similar ‘mesh’ WiFi routers from Google Nest, Amazon erro et all are good products but I do not recommend any of them for WiFi use in Japan: they all lack support for the IPv6 protocols used by NTT FLETS Japanese internet service providers (ISP) and the NTT NGN backbone.

Goodbye PPPoE (IPv4) Hello IPoE (IPv6)
The problem with Velop is the same one with the Apple AirPort Extreme (part 1, part 2) and Google Nest WiFi: no support for DS-Lite and Map-E IPv6 protocols used by NTT FLETS. Both DS-Lite and Map-E use IPv6 IPoE (IP over Ethernet) that replaces the IPv4 only PPPoE connection protocol.

IPoE is also called IPv4 over IPv6. This means IPv4 packets are encapsulated inside IPv6. Fast internet connections in Japan use IPv6 but this means that your home router needs to encapsulate everything IPv4 in IPv6 before going out on the NTT internet backbone.

Any router that does not support IPoE/IPv6 on the internet in Japan does not get priority routing at crucial exchange points between local area lines, the ISP, and the NTT backbone. PPPoE is worthless because PPPoE/IPv4 in Japan is ‘tapped out’ and sits in a traffic jam on the local internet highway on-ramp while IPoE/IPv6 whizzes by on the IPv6 super highway.

Japan Internet Setup
Do yourself a favor and do not waste time and money with any WiFi router that does not support DS-Lite/Map-E protocols and IPoE/IPv6 service. Completely eliminate PPPoE on your home network if you want fast internet service in Japan.

The first step: get a free IPv6 service option. All of the Japanese internet providers offer free ‘v6 Plus’ or ‘IPoE’ or similar sounding service options for connecting your home internet directly with IPv6. This is easy to do by phone or online.

The second step: get a WiFi router that supports DS-Lite and Map-E. Either rent a pre-configured WiFi router from your internet provider or purchase one. The major Japanese WiFi home router manufacturers all support these protocols and maintain IPv6/IPoE lists of internet providers and services qualified with their WiFi routers:

Always make sure your WiFi router is updated with the latest firmware.

If you are not a DIY networking guru, save time by renting a pre-configured WiFi router from your Japanese internet service provider. Rental prices vary, So-Net for example charges ¥400 a month. If you are in Japan for the long-term and futzing with internet configurations is not a problem, a good WiFi router investment from the list above can save you money.

UPDATE June 2020
NTT FLETS is under a lot of speed stress from people working at home during the COVID crisis. If you have not done so already, migrate from PPPoE IPv4 to IPoE IPv6. Otherwise peak internet hours will be unbearably slow. A good stress free service is KDDI au Hikari nuro which uses excess bandwidth that KDDI rents directly from NTT dark fiber exclusively for nuro.

Farewell to AirPort Base Station Part 2

Airport Extreme 8th Generation

After posting Farewell to Airport Base Station a reader who also suffered from slow NTT Flets internet speeds asked for a few details to help him troubleshoot his own setup.

Before starting out here is a warning: rental devices from NTT and internet providers like So-net are constantly being updated with firmware updates, backend services running on them are constantly updated as well. NTT Router IPv6 and PPPoE IPv6 settings shown in online documentation may not match router settings of the most recent firmware versions. Also remember that rental NTT router models are different depending on your connection plan.

When in doubt confirm with NTT Flets or your internet provider tech support.

My Setup

I have a NTT Flets Hikari Phone + ‘Mansion’ internet connection plan with So-Net as the internet provider. As I wrote in the first piece, IPv4 traffic is extremely congested in my local area which So-net tech support checked and confirmed. So-net suggested their free IPoE IPv6 option service as a possible solution.

Unfortunately my AirPort Express Base Station was not very good routing IPv6 traffic. Even in Bridge mode most of the network traffic outside of YouTube remained stuck in the clogged IPv4 stream. This makes sense as AirPort was conceived in the IPv4 era and Apple isn’t updating the software features anymore. The So-net IPoE IPv6 support site mentions that Apple routers “may not be compatible.”

So-net IPoE IPv6 Support Site

The So-net site does list NEC, BUFFALO and I-O DATA WiFi Routers that are compatible with IPoE IPv6. The key is IPv6 Bridge / IPv6 Pass-Through support which all of them appear to have.

Instead of buying my own WiFi router to replace the AirPort Extreme however, I decided to rent a So-net WiFi router preconfigured for IPoE IPv6 service and DS-Lite (IPv4 over IPv6). The So-Net WiFi router is free for the first 7 months, ¥400 a month there after. So-net tech support said I could return the router at any time in the first 7 months, no questions asked. These things can change so be sure to confirm any rental agreement with your internet provider.

NEC, Buffalo and I-O DATA WiFi Routers can be configured for DS-Lite and Map-E as well but after a year of wrangling with AirPort Extreme configurations, I was done with doing my own IPv6 setup.

I ran with both AirPort Extreme and the So-net rental WiFi router for a few weeks until I was sure IPoE IPv6 and DS-Lite were working OK, then pulled the plug on AirPort. The only tweak on the So-net WiFi router side was renaming the default WiFi network names and login passwords.

The final step was shutting off PPoE on the NTT router. PPoE is a IPv4 only legacy technology and leaving it on can hamper DS-Lite/IPoE performance. The easiest thing to do is reset the NTT router to factory defaults and do not set it up for PPoE.

Confirming IPv6
There are some simple ways for NTT Flets and So-net customers to confirm if IPv6 running correctly:

1) NTT Flets IPv6 Speed Test site If IPv6 is configured correctly you can access the site and test NTT Flets connection speed.

2) Download the Ookla SpeedTest App from the Mac App or iOS App Store. If So-net IPoE IPv6 and DS-Lite are correctly configured your should see “INTERNET MULTIFEED” as the home network name.

Ookla Speedtest

Lastly, here are some helpful links:

So-net IPoE IPv6 setup site
So-net IPoE WiFi Router Rental site
NTT Flets Router IPv6 Configuration site
Be careful of the NTT site as the configuration information may be out of date. When in doubt call tech support.

Farewell to AirPort Base Station

Airport Extreme 8th Generation

I used AirPort since the first generation in 1999 and always found the AirPort series to be reliable and easy to configure. But starting in mid 2016 I noticed my NTT Flets mansion (PPPoE – VDSL) service slowing down to analog modem speeds at night and during the weekends.

And so began a year-long tech support journey with NTT and internet provider So-Net to find the problem. Many configuration tests, speed tests, and traceroutes later one thing was clear: IPv4 traffic in Suginami Tokyo was chronically congested. It was time to switch to IPv6 service which So-Net offers as a free option.

The IPv6 option came with a warning: “some of our customers have problems accessing sites like Amazon or Rakuten and switch back to IPv4.” I took the plunge anyway and tried using Airport Extreme (Generation 8) via PPPoE bridging and IPv6 tunneling options.

That worked better than the previous IPv4 only setup at first but it wasn’t long before using the internet after 9 pm was impractical. I then tried using Airport Extreme in bridge mode. That helped for a while but nighttime internet speed degraded over time, by summer of 2017 I was back at square one.

Another set of tests later So-Net tech support suggested a So-Net wireless router for free (the first year) “tuned for routing IPv4 over IPv6.” At wit’s end I decided to give the NEC ATERM WG1810HP wireless router a try. Like magic my internet speed problems were over.

Poking through the ATERM settings I noticed everything was preset for DS-Lite, clearly optimized for NTT FLETS. It’s also clear from reading Japanese forum posts that the NTT FLETS transition to DS-Lite has been in place for some time and AirPort Extreme routers are not equipped for the change. With Apple getting out of the wireless router business time to say goodbye to AirPort Extreme. It was a good run.

Update: more details and migration explanation here