Talk:International mobile subscriber identity

Stored as a 64-bit field?
I don't think this is relevant. It used to say "stored as a 64-bit field on the SIM" (which is possible I suppose, although without a citation I'd say it's dubious, most GSM numbers are BCD, but is still irrelevant) but now just says "it is stored as a 64-bit field" which simply isn't true - I can store an IMSI scribbled on a piece of paper. There are also many systems that store IMSIs in (eg) BCD or ASCII. gwinkless (talk) 16:45, 6 September 2018 (UTC)

Note that 16 digits can fit into 55 binary bits. I suppose the original note might have meant stored in 64-bits as BCD (4 bits per digit) which is probably more likely. I still think it's irrelevant to the article though. gwinkless (talk) 16:49, 6 September 2018 (UTC)

Untitled
From discussion added to my talk page is the following N.B. this is only part of Kieth's original comment:Mozzerati 22:01, 29 May 2004 (UTC)

E.214 dictates that you convert the MCC->CC part first, then the MNC+MIDN->NC+etc part second. (Which has problems which are documented elsewhere.) Your example does MCC+MNC->CC+NC as one step (which is probably how it should be done, but not how E.214 dictates). TIA, KeithTyler 18:37, May 25, 2004 (UTC)


 * I have been looking quite carefully at this (please note a number of articles added whilst I did it including NPI page with E.214 numbering plan listed). I've added some sources at the end of the section on GT problems.  Reading E.214, I can see how it could be interpreted to mean that the analysis should be done separately, but it's clear that there is no fixed relation from MNC to NC so that part of the analysis can only be done in the context

A further discussion is, which of the problems listed in the GT problems section are actually still valid. I've seen the exchange (actually found it on the internet, which makes a great change!!). The GSM Numbering Authority clearly addressed that


 * analysis is done all at once (not MCC separately from MNC), the conversion between countries works
 * there is no need or intention to switch away from E.214 numbers in Europe
 * billing systems do have problems with threee digit MNCs
 * most modern mobie phones cope with three digit MNCs
 * older "legacy" phones don't all cope.

I think that probably the section should be rewritten with attribution as far as we can (who wants to replace E.214???) also some history so it's clear which concerns are really valid and which have already been addressed. Mozzerati 22:01, 29 May 2004 (UTC)


 * Given that the North American problems with the E.214 global title scheme have partially been "solved" by serious underutilization of the U.S. and North American IMSI space, can it really be considered no longer a problem?


 * Also, how did you determine that NC for Cingular? 4054? I've been trying to find a source on how GT downconversion is done from MNC to NC inside NANP.


 * TIA, KeithTyler 23:52, May 30, 2004 (UTC)


 * The best source for all of the network codes is the IR.21 form from the GSM MOU exchanged from operator to operator to allow setting up roaming agreements. You may need to join the MOU to get access to it for some operators (though others have published theirs at certain times). I know a bunch of this stuff in memory from having designed or typed in the source data for roaming agreements.  This isn't secret as such (it has to be known by all the operators in the world outside America), but it's certainly not easy to find a source on the internet (I've been looking, since I wanted to reference it).

I've been reading around, and it seems that the issues with the three digit MNC are more related to what is broadcast by the base station to the mobile phone than to the IMSI in the core network. There were a bunch of concerns expressed (as I said above) but for most of the core network, there is no difference between a two digit and a three digit MCC since we just treat the whole thing as one big number and analyse as deep as we want (most switches I know) or to at least seven digits (switches the GSM NA Checked).

Now I have to speculate about some details. Why would Non American GSM systems have to handle a three digit MNC?


 * 1) : if the network wants be able to have three digits in their own country
 * 2) : for the billing center be able to send billing data to the correct roaming partner in inter operator clearing
 * 3) : for the core network to be able to route correctly IMSI messages to the correct roaming partner
 * 4) : for the mobile phone to be able to tell between two different networks when roaming in a 3digit MNC country based on cell broadcast information.

1) is seems to be a question which the NA says will not be solved soon if ever.

2) is a problem, apparently

3) is solved automatically I believe by the current analysis in international switches

4) is a problem which is going away. All modern mobiles can handle both 2 and 3 digit codes

Reading the documents, the IOC has decided to use only MNCs like XX0 until 2008. Based on figures of approximately 400millon phones produced each year against a user base of 1billion, of which we can assume a large percentage already support three digit MNCs, we can see that 4 should be more or less solved by that time (not forgetting that phones often get 'recycled', so there can be some quite old ones in certain networks). In those phones that have sufficient frequency support to roam from America to Europe, I doubt severely that there's a high percentage of phones without dual length support, if any. That, then won't be a big problem by then.

Looking at the billing systems, I remember why I've been avoiding working on billing for about four years. Billing updates are a total nightmare, not to mention that some companies still try to sell COBOL based billing systems which problably have the 2 digit MNC totally hard coded. However, this matters mainly for their home customers. The international clearing can be separated (e.g. at a mediation device) and then they will be able to update by 2008 if they have to. This means that it will be a problem for individual networks which fail to update in time, but it won't be a problem for the overall network, since

There's another other problem that I can see related to IMSI space limitations


 * a mobile phone which doesn't know about the full American country codes won't know that two different networks with different MCCs actually both belong to the same country - this seems to cause problems with some national roaming situations

Now, I'm trying to analyse this, it seems to me that it's an inevitable problem however, since e.g. eventually a new MCC may be added to the American range and at that point old mobile phones would have no way of knowing if it was American or not.

there's yet another hypothetical problem


 * a network with multiple MNCs may have a single NC

According to the IOC documents, there is a situation where each licence a network gets comes with its own MNC. Now, if a network did declare all of these as mapped to the network's own NC then there would be a true loss of information in the E.212->E.214 conversion process. This would cause a problem if, on loss of a license, the networks subscribers were transferred to a different operator. The solution would be to have one NC for each MCC, either by having multiple allocations, or by adding an extra digit at the end of the NC (which the operator could probably just do themselves).

Now, what else have I missed??!!!??


 * The argument for non-US systems to recognize 3 digit MNC seems to be that if they did that, then IMSI (E.212) could be used for global title, which GSMNA seems to think would be the best solution. But there's also compatibility problems with some international legacy switches that prevent that from happening.


 * Hmmm yes. I (as a "GSM person") agree with the GSMNA.  At present GSM networks have to maintain a table of E.212 to E.214 and and a table of E.214 to "next hop".  If we could do analysis in E.212 then the first table wouldn't exist (well, actually it would, but it would have no "maintainance").  On the other hand, the fixed networks have to maintain a table of E.164 routing and an identical table (they can probably actually use the same one) of E.214 routing.  If we switch to E.212 routing, they have to maintain two tables, one for E.164 and one for E.212.  So we are asking for


 * monopoly PSTNs
 * and government regulators
 * in hundreds of countries
 * to understand a new numbering system
 * to do more work
 * for free!!!


 * A whelk's chance in a supernova.. always worth trying though :-)


 * The main concern seems to be that we can't ensure international roaming between NANP and elsewhere if we can't establish a one to one correspondence between the country and network portions of the global title and the respective portions of the IMSI (or what those portions represent, that is). The solutions taken by GSMNA is that they are only distributing MCC 310, and on top of it, they are trying to keep MNCs distinct within all of NANP (meaning no overlap of MNCs between U.S. and Canada, for example) so that MNC alone can determine MCC on global title downconversion. This is particularly problematic when you consider that they are also limiting MNC to XX0 format codes.


 * That was the main concern in the original letter from the IOC; agreed. The GSMNA letter clearly (well, actually not so clearly, but it's there if you read carefully) answers that since the analysis is done all at once, there should be a one to one relation.  It is the responsibility of American nubmering people to have a separate NC for each of their HNIs.  Now there are 10^6 available network codes (based on 7 digit analysis as stated for international switches) or more if you don't need full analysis at the international level (as is normal), so there's space.  The only thing I can think of that would lead to an exahustion of NCs is some other limitation of American E.164 allocations of NCs.


 * Most of the time, networks declare only one NC. However I have configured roaming agreements with networks which declare multiple NCs (I think that was one from the UK.. I definitely don't remember which operator), so multiple NCs would be perfectly okay in practice.


 * The full source data is available at https://infocentre.gsm.org/ but that's restricted access (and I don't have it right now, and probably wouldn't use it without explicit permission even if I did..) see http://www.gsmworld.com/about/index.shtml for more info. I'm not clear if it qualifies as "Use of GSMA Roaming Agreements" or "Infocentre - members' secure website" which will decide whether it's only for operators or also for associate members.  I've managed to find [and IR.21 on the internet] also [the same IR.21 in HTML on Google] getting the same form for each American network would answer many of your questions, so if some official representative is reading this and would like to help Wikipedia, please send by mail.. Discression will be guaranteed if (and only if :-) you ask for it.


 * Everthing is confirmed. I had a discussion with a roaming agreement coordinator from an operator.  American networks with multiple MNCs declare a separate MGTs for each MNC.  The two or three digit MNC is a per country choice.  There is no problem in the GSM core.  Mozzerati 07:06, 2004 Jun 1 (UTC)


 * I don't think that multiple MCC is a problem for the mobile, as long as the mobile is properly maintained. Aren't those MCC/MNC lists supposed to be updated regularly (with modern models, via OTA) anyway? Otherwise, mobiles wouldn't know about MCCs for brand new countries, either.


 * I'm not sure why, (I suspect the answer is that phase one mobiles only listen for a two digit MNC), but the GSMNA does state that there is a problem.. Needs further investigation.


 * Generally the lists aren't updated (and OTA often requires a user accept, depending how the mobile is configured). It normally doesn't matter anyway, since as long as we know our own MCC then all others are roaming MCCs.  Having multiple MCCs visible is also normal (try the various European border regions, e.g. around Basel) and we won't care if they happen to be different American ones.  It would, however, be a perfectly valid requirement for future mobiles.


 * As far as MNCs having a multiple NC, that may already be happening -- I know of one NA carrier that has about 12 MNCs, though they are trying to consolidate to one.


 * Does this mean they are actually replacing SIMs? Mozzerati 06:27, 2004 Jun 1 (UTC)


 * KeithTyler 16:20, May 31, 2004 (UTC)

Keith, if you have any further references for all of this, even if they are in industry insider documents, please give me them and I can attempt to find them and read more. Mozzerati 06:27, 2004 Jun 1 (UTC)

Global Title Problems
The U.S. is no longer only using 310 as a MCC. At least 311 is used also. I recognize that some of this info is a little dated (we all know how fast things change in this industry) but carriers no longer translate based on the first two digits of the MCC. If so, 310 and 311 would translate the same. However, I presume the reason that the U.S. branched off into MCC 311 may be because MNC's are most commonly looked at by the first 2 digits still. This of course restricts MCC 310 down to 99 MNC's instead of 999. Kenny D 22:29, 23 February 2007 (UTC)

Incomprehensible, ungrammatical sentence

 * "In idle mode behavior, IMSI attach/detach location updating means the updating process was initiated by the mobile station to notify the BSC if the handset is powered on or off."

Please correct. -Pgan002 04:33, 12 July 2007 (UTC)

Merge with IMSI detach
The IMSI detach article does not present sufficient information to stand on its own; it should be merged here. Neelix (talk) 19:42, 23 August 2009 (UTC)

Disagree. IMSI detach doesn't have a lot to do with the idea of IMSIs; it doesn't belong here (much like prostitution doesn't belong in the article about money). It belongs with articles on other "procedures" in cellphone systems, if anyone cares enough to write them properly. JöG (talk) 19:40, 28 September 2009 (UTC)
 * Agree with your suggestion. I'll setup a stub incorporating IMSI attach and IMSI detach. → AA (talk) — 14:21, 14 April 2010 (UTC)

The artical says "The problem lies in de-translation of the global title back into a mobile network E.212 IMSI. Since E.214 recommends that the country part of the translation be done first, it presumes that a given E.164 country code only relates to a single E.212 mobile country code. Unfortunately this is untrue in NANPA member nations, and doubly untrue in the US. So, a global title with CC of 1 can indicate any of 7 US MCCs, or Canada, or any Caribbean nation."

This is wrong as there is no need to do any de-translation for E.214 back to E.212. In fact this is impossible for much more cases than only NANPA, in all cases where CC-NC is more digits than MCC-MNC the last digits of the IMSI are lost. — Preceding unsigned comment added by 62.159.77.166 (talk) 14:33, 24 October 2011 (UTC)

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