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Tokyo high-speed access

It's that time again. Can anyone suggest any updates to this? (I'm starting
to get people asking me awkward questions about it, and I don't know what
to say. :) Any more cable modem systems out there? Anyone want to tell me
about ISDN?

Tokyo High Speed Internet FAQ

1.0 About this FAQ

This FAQ provides all the information I've been able to distil on
high-speed (over 56k) home internet access in Tokyo. The majority of the
information has come from reports of user's experiences on the Tokyo
Linux User Group mailing list ( More information
is always welcome; please feel free to fill in any missing sections or
provide your experiences with any high-speed internet products, and
email them to me at

2.0 ISDN

    [You write this!]

3.0 OCN

OCN is a service offered by NTT; it looks like ISDN, smells like ISDN,
and requires an ISDN terminal adapter, but it isn't ISDN. It's an
unmetered, statically allocated digital service, and comes in three
flavours: Economy is probably the one you want, but a misnomer at
32,000Y a month.

This'll give you a 128kbps line which is shared between the other OCN
subscribers at your local exchange. Naturally, your actual download
rates will vary depending on how many other subscribers are on your
exchange and their bandwidth usage. Personally, I had this service in
Jiyugaoka and managed to almost always get the full bandwidth, with
downloads averaging around 10 kilobytes/s.

The economy service will give you 16 IP addresses, so to use them you'll
either need a router or a clever Linux box. To connect to OCN with
Linux, just use pppd and have it go off hook with "ATDT0" or similar.

Now, with ADSL approaching, I'd say the only reasons for getting OCN is
that you can run services freely, and that it's available pretty much

4.0 ADSL

If you live in one of the following areas:

    Kayaba-Kabuto (Chuo-ku) 
    Aoyama (Minato-ku) 
    Mita (Minato-ku)
    Yotsuya (Shinjuku-ku) 
    Yodobashi (Shinjuku-ku) 
    Ikebukuro (Toshima-ku)

you're greatly in luck - it's likely there'll be an ADSL service available
to you. As the ASDL rollout continues, we can expect this list to grow.

As far as providers:

    4.1 NTT-ME

This is an ADSL service offered by NTT: it comes in two brands,
the "Personal" service and the "Professional".

The Personal service gives you one IP address at 6,890Y per
month. The Professional service is 26,400Y a month, but gives
you 13 IP addresses, your own domain, primary DNS and all the

Ayako Kato reports:

   The speed they advertise is 512Kbps downstream, 224Kbps upstream for this
   "personal" service I use. I usually get up to 40 - 50KB/s down at night,
   which is not bad at all. I was told it may be slower during daytime, but
   I'm never home during the day anyway. I have never felt anything was
   "slow" since I started using it.

   There isn't any filter that block incoming traffic to ports < 1024. I have
   a few ports open on the gateway box but have never had problems reaching
   them from outside. (Configuring them correctly is a different issue. A few
   very skilled people helped me set things up and gave me tons of advice.
   Thanks Chris. :) )

   I can see that a lot of my neighbours (IP-address wise) are running Linux
   and have various services enabled, ... http, ftp and even telnet(!!).
    4.2 Tokyo Metallic

Tokyo Metallic ( offer a "Single 640" plan at
5,500Y. While the address is theoretically dynamically allocated, it
seems not to change and is probably static DHCP. It used to be translated
using NAT so you couldn't connect to it from outside, but now they are
using real-world IP addresses; however, the DSL gateway they supply appears
to block well-known ports, so running servers from this is not an option.
(unless you want to run them on weird ports...)

According to Johnathan Shore:

    BTW, their service is excellent - have found that it delivers the
    advertised bandwidth (unlike many installations in the US).  I
    regularly get ~70KB/s on the 640, though you'll find that there are
    many places on the wan that cannot even sustain that. 

Their "business plan" is an SDSL which allows you to run servers is
32,000Y a month. (More information about this would be appreciated!)

    4.3 NTT's SDSL Plan

NTT is also doing a service from December 2000 at 7000Y per month.
Shimpei quotes a reliable source:

    It's supposedly SDSL rather than ADSL, and the advantage over Tokyo
    Metallic's offering is that it works over ISDN lines. This might be
    a big win for those of us who entered a deal to pay about Y700
    monthly to get ISDN rather than something like Y70,000 up front for
    an analog line. I don't know anything about IP policy, promised
    bandwidth, service areas, etc.

5.0 Cable Modem

    5.1 Tokyu Cable

[Thanks to Alberto Tomita for this section]

They use some sort of IP masquerading so that hosts inside their net can
not be seen from outside. UDP packets are blocked at the gateway. IP
addresses assigned by DHCP are in the private address space. Their own
Internet connection is provided by IIJ through a 100Mbps link.
Internally, they have a 622Mbps ATM backbone connecting their 6
re-broadcasting stations. Bandwidth from these stations to the cable
modem is said to be 14.3Mbps (the cable modem rental fee is included in
the service, 5200 yen per month, or 7000 yen/month for the Internet+CATV
service -- CATV alone is 3800 yen/month). The cable modem brand is
"Terayon" A hub
can be connected to it, allowing more than one computer to be on the net
(they all get their IP addresses by DHCP).

The most effective debugging tool is still careful thought, coupled with 
judiciously placed print statements. -Kernighan, 1978

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