Friday, March 18, 2011

Docomo data plans will be expensive for phones that support tethering

I've been holding off posting anything about something so trivial as phones given the situation, but with what seems to be a situation getting under control at the plant, here you are:

From April 1, Docomo is scheduled to begin allowing overseas phones, including the iPhone 4, on its network. But there are some catches, potentially deal-killing catches.

First, according to a Docomo press release, there will be some restrictions on which devices can get access to the packet houdai for a reasonable price. Any phone that is capable of tethering (hot spot) will be charged the premium rate, bringing the full price to 10,395 yen for unlimited data. (Along these lines.) Otherwise, a phone can be used with the tiered plan for 5,985 yen for month or the flat rate plan Nicholas announced for 5,460 yen.

Next, there is still the issue of certification (lightning +〒 mark =技適マーク画像). Juggly-kun reported (just prior to the quake) that uncertified phones would be allowed but would be charged the premium price.
ちなみに、SIMロックフリー端末で技適マークのある端末(例えばiPhone 4)であれば、パケット定額プラン上限5,985円で利用できるとのこと。技適マークの無い端末では10,395円。技適マークがあってもテザリングは10,395円。技適マークのチェックがドコモショップで行われるそうです。
But this must be wrong. According to the press release.
They could be flat out denied, and I expect they would be. I understand from @havill that phones like the nexus one are entirely comprised of bits and pieces (except for the battery, which can be changed) that are certified for use in Japan. It will be interesting to see how these phones, which don't bear The Mark, will be treated.

Docomo will update their site with information regarding which phones will be allowed, which won't, and which will be charged a premium. In the meantime, if you were planning on installing that update that gives you the ability to tether, I'd hold off if you plan to put your phone on Docomo. If your current Android ROM has built-in hot spot support, I'd suggest to start doing research into ROMs that don't include that feature.

The details in the press release are subject to change, and probably will change. Given the current situation, the entire thing could be delayed, especially if the plant that was supposed to be stamping out microSIMs is shut down to save power.


  1. Techniker TechnologeMarch 19, 2011 at 12:07 PM

    currently I am tethering a lot... due to... umh ... some "travelling". How do they detect tethering? I mean, low-level packet inspection? Or by using the IMEI? For the latter, an original HT03a might be safe, no?

  2. Currently IMEI has nothing to do with it. After April 1, I still don't think
    it will. My guess is that Docomo will keep doing what they are now. What
    they are doing now is unknown, but I don't think they are *actively* looking
    for tethering.

    So after 4/1 if you tether with an ht-03a, or with something you brought
    from another carrier, my guess is that you will be running the same risk
    either way.

    NOW, if Docomo determines that average bandwidth usage patterns change for a
    large number of users, or if people who brought phones to Docomo start using
    significantly more bandwidth than users with Docomo-branded handsets, then
    they could always start looking for tethering (ie, non standard ports,
    packet inspection) rather than what I think they are doing, which is simply
    looking for anomalously high bandwidth usage.

    Yamada said that 99% (or something like that) of FOMA users consume less
    than 5 GB a month. 5 GB is also the limit for Xi LTE, so in my mind, 5 GB is
    a magic number that should be approached with caution.

    I come nowhere near 5 GB a month, BTW.

  3. When I tether with my rooted Xperia, the connection is so slow that I can only use it for websites that the bigger screen is more useful for, or ones that use flash. Regarding bandwidth, tethering doesn't result in me using any more. Watching youtube on my keitai is the biggest user of bandwidth.

  4. There are actually several ways to detect tethering. One way is to use techniques for counting hosts behind a NAT device, others are passive OS fingerprinting and less reliable ways will rely on the useragent string (but this can easily be faked by the use). Close to 100% accurate tethering detection systems are currently on the market, so if DoCoMo cares enough they'll have no problem finding you.

  5. i would really appreciate any URL confirming the 100% accurate method of counting hosts behind the NAT. especially i would like to hear how would you count the hosts behind the NAT. consider me running android on the phone and any flavour of linux on the tethered machine.

  6. I've found some information on tethering, and we were discussing it here before, but I'm afraid if I post the comment here no one will see it. Is ther a forum section for sbs or are you thinking about such for the new site?

    Anyway, here goes. I'm not sure if this is new info.

    Here: readers of theregister are discussing AT&T's clamp-down on tethering. Most of the discussion is about how repugnant it is or how it is within the contract. The thing that I'm finding useful right now is more how AT&T even knows who is tethering. So far, there are two ideas:
    1) http / browser headers and such identifying the applications
    2) TTL indicators

    There are ways around the former. You don't want Chrome browser identifying itself as such since there is no Chrome browser for android or iOS. A plugin might be able to solve this -- as would routing everything through a VPN.

    Regarding the latter, Julian3 said:
    For all you wondering how they can tell:
    All IP packets have something called a TTL associated with them. It stands for Time To Live. Every "hop" along the network from one router to the next reduces the TTL by one. When it reaches 0, the packet is dropped. This was introduced to keep routing problems from overloading the network. If for example, by some error a packet was going around in a circular path, the TTL would eventually reach 0 and prevent a packet storm.
    The thing is, ALL routing devices do this. OSes use standard TTLs. For example, let's say both your iPhone and laptop use 127 for the TTL. AT&T will receive packets from your iPhone with a TTL of 127, but since the packets from your laptop pass through your iPhone first, they arrive at AT&T with a TTL of 126. They can detect a tethered device this way.
    Apple uses a TTL of 64 for the iPhone, by the way. So change the TTL on your computer to "65" and there should be no problem. Here's how to do it:
    1. Click Start - Search and type “regedit”. This launches the WIndows Registry.
    2. In the registry, navigate to the following registry key [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters] HKEY_LOCAL_MACHINE
    3. In the right pane, right-click and select New – DWORD (32-bit value) and set its name as “DefaultTTL” and set its value anything between “0? and “255?. The value sets the number of Hops or links the packet traverses before being discarded.
    Kudos to Ryan Laster1. I don't have an iPhone to test this.

    This was followed up with guessing on whether the hone was acting as a modem giving the external device its own IP or as a NAT which would result in the TTL being predictable diminished (pardon me if I screwed up the details there...)

    The TTL was not brought up here before in our discussions on this, from what I recall. I guess using a VPN would hide all of this as well, but the information might be useful to someone here, I thought.


  7. Thanks for that. There is a third way. The lazy way. Just ding everyone who uses an astronomical amount of packets under the assumption that they had to be tethering. 99% of the time, they'll be correct. Early discussion I saw indicated that this is likely what AT&T was doing.

  8. That's what I had seen before with people who heavily use youtube and the like getting the notices, but it seems that with the above two methods the carrier could get reasonable verification that another device is being connected through the phone.

    And if it is this easy, the carriers would not shy away from enforcing the no-tethering rule even on low bandwidth users. I think this is, after all, a play for control of the device not so much as an attempt at minimizing data usage. AT&T, etc. want to lay the ground rules now that they control the whole experience. Then they can do what they want with streaming music services, tethering, and anything else they decide is an enhanced service down the road.

    They will fight with everything they have to not just become dumb data pipe maintainers. There is less money in that.

  9. The certainly can be 100% sure if you are tethering by those methods, and in theory it would be simple to check.

    But realistically, the carriers must balance the expense of checking for "illegal" (if you will) packets versus the cost of actually doing the checking. If 99% of people aren't tethering and they check 100% of people's packets, then they will spend more money than they will recoup.

    It comes down to how efficiently carriers can check. I don't know the answer, but based on the fact that more carriers haven't been aggressively hitting people with tethering charges, I'd wager that they are not setup to do it easily and affordably.

  10. VPN and TTL live on a different levels of the protocol stack and have nothing to do with each other. TTLs are visible no matter how you encrypt the traffic, because every device on the way needs to inspect and decrement them. However, any reasonably smart tethering application should have reset TTL to the default value for the device, thus hiding any suspicion of packets originating from another computer.

    About "browser headers" -- how can anyone get a browser header from a ftp client? Or a torrent client? Or any other piece of software which does not directly download pages over HTTP? And what exactly should prevent the end user from installing mobile version of Opera or Firefox on his handset (both with their own "http-useragent" id strings)? Moreover, the deep packet inspection incurs additional hardware and software costs, and I think most providers are quite reluctant to invest in something which does not really guarantee results because it applies only to the very small part of the user base.

    Summing all the above, there's NO WAY anyone can reliably detect tethering unless the handset is rigged to report the fact directly to the provider. Which is how I would do that if I was the provider. And which is why I mostly use custom made ROMs I'm sure my provider haven't had a chance to touch.

  11. I just picked up the Optimus Pad from Docomo today and was surprised to see that they hadn't disabled the tethering feature. I changed devices but kept my existing contract, is this a feature I should leave alone?

  12. I would check what APN you are connected to. If it is then that is the unlimited one. If it is anything else then you will get a fat bill. My guess is they don't know it can tether. I would say using it once in a while should be fine if you have the correct APN. But don't go hog wild if they notice too much traffic they might take a closer look.

    I'll let others chime in though.

  13. Really, it had tethering? Are you sure? That is just mind boggling. I'll try and look into but I've officially used my allocation of blogging time (and then some today). It is inconceivable that they just overlooked that. As Nicholas hints at the APN, I'd be a little worried that the firmware is tweaked to not work at all with the bizho APN. Actually, I'd be more worried that the APN would switch to something no flat rated but I also can't imagine that either....

  14. Yeah, I was shocked when I saw it. I don't know if it's because it's running stock 3.0 or what, but it's there. The APN is

  15. The APN is not the unlimited APN so you are going to get charged for every MB. Be careful because you could very easily end up with a 10,000円 or 20,000 円 bill. See if you can't connect to the APN. Add it manually if you need to.

  16. I'm not familiar with that APN but a quick google search shows it as moperaU, which is something that allows tethering. But I was under the impression that you had to pay extra for mopera. I admit I'm a bit in the dark with how all the providers integrate.

  17. Nicholas, I don't think so. It is a flat rate APN, but I thought to use the mopera APNs, you had to pay extra for the service. I think the best thing for him to do is first figure out what is going on with his bill. And maybe confirm with a shop what he'll be paying.

  18. reading now ↓

  19. Oh I see. I was under the impression that all others were pay as you go.

  20. Your Japanese is much better than mine and Goggle translate only made it more confusing.

  21. I guess I'll just wait and see, try it a few times and see if it makes a measurable difference on my bill. Like I said, I couldn't believe it was even there. How quickly do the charges show on mydocomo? I'll let you guys know either way. Great site!

  22. @ chris, the below has gotten a bit mucked up, so starting a new thread here.

    This is something that I need to confirm for my own benefit. Mopera has always been a bit of a mystery to me. Basically, that is one of the mopera APNs that is used for tethering. So having the tethering option available and that APN set is not strange. It makes sense if you have subscribed to Mopera U for tethering a computer from your tablet or phone.

    I was always under the impression that Mopera U service was in addition to your data fees to Docomo, so that you had to pay for both, which brings your bill to (wait for it) ¥10,395 per month.

    Now I could be wrong so no need to panic. If you just got it, they could have set it up strange, or you could have accidentally subscribed to Mopera for a massive extra fee each month. Or maybe you just discovered the best way to get cheap service with docomo: cancel the biz houdai flat plan with docomo and subscribe to Mopera U. But if it was this easy, everyone would be doing it, I'd think.

    At the very least mydocomo should show your billing info from the previous day, so I'd suggest to check it and see what your are currently being charged.

    Do you see the following line items(内訳)?
    1) パケ・ホーだい*定額料 (where * could be ダブル) = packet houdai flat rate fee (should be the minimum you'd pay)
    2) FOMAパケット通信料(合計)= This should be the total you'll be charged so far - if it's in excess of 6000 yen you've got a problem)
    3) FOMAパッケト通信[一般] = General packets that DON'T fall into the flat rate. This is where extra stuff shows up when the APN is set wrong.
    4) FOMAパッケト通信料 スマートフォン定額 This should be how much you are paying for the smartphone.

    If you see these and line items for Mopera, then you are paying for both.

    Maybe a screenshot would be good, if you can.

  23. I sent a screen shot to your twitter account. You'll notice a cancellation fee for the 7" Galaxy Tab. I'm an AF guy and am still really confused by the complexity of the mobile carriers here. Maybe you can make sense of it.

  24. Ok - it seems as though the issue is moot. I hadn't actually tried connecting via tethered connection because I was afraid of exorbitant charges. Now that I've actually attempted it seems that the tablet loses internet connectivity as soon as you make it a wi-fi hotspot. It still broadcasts a SSID that my computer can connect to, I just can't reach the internet from it.

    Sorry for wasting your time.

  25. No worries.

    Since I was looking at it, here is what you bill is in English. Basically, I didn't think about it but don't have bizhoudai because you don't have a phone. The tablet is data only, right? Actually, you do have the data plan that supports tethering. It is the same plan that people would have for a 3G mobile hotspot router. It might be good to play around more with the tethering function. It might actually work.

    If you didn't have a two year contract, this would cost you a lot more. The low price of 4200 yen could be limited to the first year only. It could go, but only by a 1500 yen or so. Good to look into that at some point.

    基本使用料(定額データプランS バリュー)¥1,905 "Flat data plan S value"
    定額データ スタンダード割 -¥952 "Flat data standard discount"
    ¥953 Total basic usage fee.

    Now add to this packet charges

    定額通信料(定額データプランS バリュー)¥8,348 Flat rate data fee
    定額データプランS(無料通信分)適用額 -¥953 worth of free data.
    定額データS割(キャンペーン)-¥4,184 promotional discount

    Leaves you ¥3,247 in packet charges.
    Add the basic fee of ¥953 and you get exactly

  26. You know, you really should be able to tether I think.

  27. Yeah, data only. It caught my eye because I was using the same plan on a Galaxy Tab before changing devices. The menu option wasn't there on the Tab. I'll have to figure out how to make it work if it's in my plan. Thanks again.

  28. Check out what Fujislider had to say here. I am pretty sure you have the same data plan as he does.