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Interfacing Osmocom GSM network to USA PSTN
by Mychaela Falconia 02 Jul '22

02 Jul '22

Hello Osmocom community, I have previously alluded in other threads here that I am seeking to interface my Osmocom-based GSM network to USA PSTN. In this post I shall provide details as to exactly what I am doing and how I go about it. I am currently experimenting with using bulkvs.com as my USA PSTN connectivity provider, chosen on the basis of cost economy: it is incredibly, mind-boggling cheap - the monthly "keepalive" cost is only 6 cents (yes, *cents*) per rented phone number! With phone numbers this cheap, I don't have to do any kind of "number economy" options: no need for "phone number NAT" (a single external phone number where a PBX answers, requiring callers to then dial an internal extension number), and no need for a mixed scheme where only one or two test SIMs get real outside numbers while all others get only fake internal numbers - instead I can give a real valid NANP phone number to every test SIM on my test/R&D GSM network. For context, my test GSM network is envisioned as serving two purposes: one is for development and testing of GSM handsets - real phone numbers are less important here - and the other purpose is demonstration to gathered audiences (American patriots and in-person freedom lovers who aren't afraid of some silly virus) for "oooh and ahhh" - and for this second purpose, having real phone numbers for every test phone will be a big boost. The interface to USA PSTN provided by bulkvs.com and other similar low-cost services is a SIP trunk, hence what I need to implement is a form of GSM to SIP gateway. But here is the part where I deviate from what appears to be the established canon in Osmocom-based community cellular networks: I don't want to run a heavyweight PBX like Asterisk or FreeSwitch, instead I want to run only a fairly thin, lightweight layer of extra sw between my OsmoMSC instance (MNCC interface) and the public-Internet SIP interface provided by bulkvs, with the needed thin sw layer put together by me, combining newly written code specific to my use case with bits of code borrowed from elsewhere. Here is the code I have written / put together so far: https://www.freecalypso.org/hg/themwi-system-sw/ The README file at the top level of the code repository explains what is there and how it works, in basic terms. One of the major pieces I will need to implement is an RTP bridge MGW that will transcode between GSM codecs (FR1, EFR, AMR) on the GSM side and G.711 (PCMU or PCMA) on the PSTN-via-SIP side. PSTN-via-SIP connectivity providers such as bulkvs don't support any GSM codecs (not one of them), instead they only support G.711 and G.729. I won't be doing G.729 in ThemWi (transcoding from one lossy vocoder to another seems like a terrible idea), hence I will run with G.711 on my PSTN-over-Internet interface and I will need to implement a transcoder between GSM codec family and G.711. I reason that what I need to implement is probably quite similar to the transcoding function in classic GSM E1 TRAUs, except that in the RTP bridge environment I also have to deal with the added complexities of packet loss, reordering and silence suppression, unpleasantries of the packet world that didn't exist in the olden days of TDM luxury. I don't know whether or not a transcoding RTP bridge MGW is already implemented somewhere in the bowels of either Asterisk or FreeSwitch - the size and complexity of both "major sw" choices is quite intimidating and off-putting. If someone who happens to know the answer gives me a pointer, it will certainly be very appreciated, but if not, then some time later I will undertake the big effort to dig in both projects and look for this transcoder. If the needed transcoder implementation already exists somewhere, then I will need to lift it out of whichever project and integrate it into themwi-system-sw - and if there is no existing published-source implementation, then I will be the first to produce one. M~

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Using a mixture of authentication-required and unauthenticated IMSIs
by Mychaela Falconia 01 Jul '22

01 Jul '22

Hello Osmocom community, A question: is it possible to configure OsmoMSC+OsmoHLR such that authentication is required for those IMSIs for which key material records are present in HLR subscriber db, yet allow unauthenticated access for certain other IMSIs (specific ones, *not* accept-all) that are entered into HLR subscriber db without keys? My use case: I generally operate my network with SIMs of my own issue, and I wish to continue enforcing authentication (and using ciphering) for all Themyscira SIMs. However, I would like to play with some old phone models which cannot be found unlocked - only operator-locked units can be found on ebay - and some of those historical operator- locked phones come with SIM cards in them, issued by historical operators who have bit the dust ages ago. It would be really nice if I could add the IMSIs of those defunct-operator SIMs to my HLR subscriber db and allow them to connect - which would have to be unauthenticated, as I don't know their Ki or even their A38 algorithm version - but do so _without_ dropping the authentication requirement for my own Themyscira IMSIs. Is what I seek possible with current OsmoMSC and OsmoHLR? And if it isn't possible with current code, any ideas as to what would be the right way to implement such a feature? TIA, Mychaela

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RFC: Reviving OsmoDevCall
by Harald Welte 28 Jun '22

28 Jun '22

[please follow-up-to openbsc(a)lists.osmocom.org so we don't cross-post all related mails] Dear Osmocom community, OsmoDevCall used to be rather successful for quite some time in recent years, but recently has been suffering quite a bit due to insufficient people volunteering to present. Big thanks to all who did! Interestingly, there's no shortage of ideas of topics at https://osmocom.org/projects/osmo-dev-con/wiki/OsmoDevCall - but then many of the potential speakers did not have the interest or time to follow-up. Most recently, the last few instances have not been taking place due to a lack of volunteers during my holidays. Last, but not least, while during COVID lockdown winter "friday night 8pm" was a good idea, this of course is more difficult during the summer, when people are more likely want to go out the weekend. So, to summarize, let me ask some questions: * would you be interested in OsmoDevCall continuing? * which day/time/timezone would you prefer ? * would you be able and willing to volunteer to give at talk within the next 3 or so months? Any other suggestions for or around OsmoDevCall are of course also welcome. Thanks in advance, Harald -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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dazed and confused.
by Keith 27 Jun '22

27 Jun '22

Often I struggle to understand memory allocations and the "weird" things of C, so please point out to me what I'm missing here (I must be wrong, because you guys would not miss this, right? cleared_ci = (struct osmo_mgcpc_ep_ci){ .ep = ep, .mgcp_client_fi = ci->mgcp_client_fi, .got_port_info = ci->got_port_info, .rtp_info = ci->rtp_info, .occupied = true, /* .pending = true follows below */ .verb = verb, .notify = { .fi = notify, .success = event_success, .failure = event_failure, .data = notify_data, } }; osmo_strlcpy(cleared_ci.label, ci->label, sizeof(cleared_ci.label)); osmo_strlcpy(cleared_ci.mgcp_ci_str, ci->mgcp_ci_str, sizeof(cleared_ci.mgcp_ci_str)); *ci = cleared_ci; LOG_CI_VERB(ci, LOGL_DEBUG, "notify=%s\n", osmo_fsm_inst_name(ci->notify.fi)); #define LOG_CI_VERB(ci, level, fmt, args...) do { \ if (ci->verb_info.addr[0]) \ LOG_CI(ci, level, "%s %s:%u: " fmt, \ osmo_mgcp_verb_name(ci->verb), ci->verb_info.addr, ci->verb_info.port, \ ## args); \ else \ LOG_CI(ci, level, "%s: " fmt, \ osmo_mgcp_verb_name(ci->verb), \ ## args); \ } while(0) How is ci->verb_info not being using uninitialized here? Would that explain random crashes with this code? https://osmocom.org/issues/5572

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Contract / Support
by jeff palmer 17 Jun '22

17 Jun '22

Hi, I am looking for contracted support on a osmocom based project, for a few days of configuration/setup assistance on a 2G / GPRS configuration. There are a lot of moving parts in the osmocom projects and versions of individual projects. Best to grab an expert on the subject than for us to dive in quite so deep just to work through some configurations. Please email me with contact details and will reach out immediately! Jeffery Palmer GSE

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call between different MSCs
by a.r.nasab＠chmail.ir 13 Jun '22

13 Jun '22

Hi I'm going to establish a call between two MSes on two different MSCs . Is This Scenario possible without an external application (for MNCC interface)? Are there any options other than LCR(Linux Call Router)? Best Regards

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Request - USIM/ISIM JavaCard Repo Access
by Jeremy Solmonson 07 Jun '22

07 Jun '22

Hi Osmocom Team, Long time listener, first time writer. Short Version: Would it be possible to get the source for your USIM/ISIM JavaCard applets that are installed on the sysmoISIM-SJA2, please? The Alternative: I've been researching a method to give my JavaCard applet default installation, and if my applet doesn't support the ADPU command, then it will revert back to your USIM/ISIM applet. Unfortunately, I have not found a solution. If you know of one, this would solve my ADPU update problem. Long Version: I've been looking into how SmartCards work and got interested in SIM card pertaining to JavaCard applets. I am interested in creating my own ADPU commands while still supporting all other ADPU commands that USIM/ISIM provide. Given the awesomeness of your products and dedication to open source research, I was hoping you can help me by providing the source. This way, I can overwrite the USIM/ISIM applets on the sysmoISIM-SJA2, and support my new ADPU updates. BTW, I looked/searched for these in your github repos and could not find these applets. Let me know if this is possible. Thanks for being awesome! -- Jeremy S.

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Using Osmocom CNI to operate a "real" cellphone network
by Mychaela Falconia 07 Jun '22

07 Jun '22

Hello Osmocom community, Is there anyone here who uses Osmocom CNI software to operate a "real" cellular phone network (2G or 3G or both) anywhere in USA, or am I going to be the first? By "real", I mean operating a cellular phone network that strives to provide a user experience to its subscribers that is as close as possible to what one would get from a "regular" operator like AT&T or T-Mobile, aside from much much smaller coverage area, perhaps as small as the operator's house and its immediate surroundings. But aside from the tiny coverage area, all other aspects of user experience need to be fully "real": each subscriber gets a real 10-digit phone number in the North American Numbering Plan, can receive calls and SMS at this number, and can place calls and send SMS to the outside world, with the user's real NANP number appearing as the source. The principal difference from a self-contained classic NITB setup is that subscribers' MSISDNs are real NANP, rather than made-up "extension" numbers, plus a PSTN gateway implementation for outside connectivity. Is there anyone in USA (or anywhere else in the world, substituting your country's "real" numbering plan for NANP) who operates an Osmocom CNI network in this manner? If there isn't, I will be happy to be the first, and I will also be quite happy to publish the source for all of the custom sw components I'm going to develop for this task - which I plan to implement as add-ons to Osmocom CNI, connecting via MNCC, SMPP and GSUP interfaces, rather than patches to Osmocom sw components themselves. However, if I am not the first to embark on such a venture, it would be nice to know how others have done it before me, so I can make a more informed decision as to what I can reuse vs which wheels I would rather reinvent per my own taste. Someone please correct me if I'm wrong, but it is my understanding that Rhizomatica (the most "real" and "production" user of Osmocom CNI I know of) does things differently from what I envision: aside from being in Mexico rather than USA (hence no NANP), it is my understanding (again, someone please correct me if I'm wrong) that they don't give their individual subscribers (end users) direct phone numbers in the Mexican numbering plan, directly reachable from anywhere in the world as +52-xxxxx, instead subscribers get "extension" numbers that are meaningful only inside those special village networks. In other words, a PBX-style network like the inside of a company with phone extensions, rather than direct PSTN phone numbers. I currently plan on using bulkvs.com as my North American PSTN connectivity back-end provider with real NANP phone numbers, at least for voice - I haven't found a solution for P2P SMS connectivity yet, but because of the complexity of the task, I decided to break it into pieces and focus on just voice at first. However, if someone else has already done something similar, operating your own cellular network where your subscribers get real 10-digit NANP phone numbers instead of just internal extensions, I would be interested in knowing whom you use (or used) as your back-end provider for PSTN connectivity and source of phone numbers, and if anyone was able to get P2P SMS included in the deal. M~

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sysmo-usim-tool error
by msfu 29 Apr '22

29 Apr '22

hi there, i have an issue with sysmo-usim-tool. If i do sudo ./sysmo-usim-tool.sjs1.py -a 4051049678932293688 -o my cli returns with sysmoUSIM-SJS1 parameterization tool Copyright (c)2017-2019 Sysmocom s.f.m.c. GmbH Initializing smartcard terminal... Traceback (most recent call last): File "./sysmo-usim-tool.sjs1.py", line 97, in <module> main(sys.argv[1:]) File "./sysmo-usim-tool.sjs1.py", line 94, in main Application(argv, "ucmI:", ["usim", "classic", "mode", "set-iccid="]) File "/usr/src/sysmo-usim-tool/common.py", line 125, in __init__ self._init() File "./sysmo-usim-tool.sjs1.py", line 76, in _init self.sim = Sysmo_usim_sjs1() File "/usr/src/sysmo-usim-tool/sysmo_usim_sjs1.py", line 240, in __init__ Sysmo_usim.__init__(self, "3B 9F 96 80 1F C7 80 31 A0 73 BE 21 13 67 43 20 07 18 00 00 01 A5") File "/usr/src/sysmo-usim-tool/sysmo_usim.py", line 40, in __init__ self.sim = Simcard(GSM_USIM, toBytes(atr)) File "/usr/src/sysmo-usim-tool/simcard.py", line 88, in __init__ self.card = USIM(atr) File "/usr/src/sysmo-usim-tool/card/USIM.py", line 188, in __init__ ISO7816.__init__(self, atr, CLA=0x00) File "/usr/src/sysmo-usim-tool/card/ICC.py", line 158, in __init__ self.cardservice = cardrequest.waitforcard() File "/usr/local/lib/python3.8/dist-packages/pyscard-1.9.5-py3.8-linux-aarch64.egg/smartcard/CardRequest.py", line 68, in waitforcard return self.pcsccardrequest.waitforcard() File "/usr/local/lib/python3.8/dist-packages/pyscard-1.9.5-py3.8-linux-aarch64.egg/smartcard/pcsc/PCSCCardRequest.py", line 208, in waitforcard raise CardRequestTimeoutException() smartcard.Exceptions.CardRequestTimeoutException: Time-out during card request maybe i spelled the adm wrong. but it is calculated from hex 3838383838383838. can you help me? Thanks msfu

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FCSIM1 cards availability and applications
by Mychaela Falconia 28 Apr '22

28 Apr '22

Hello Osmocom community, In my previous reply to Anonymous Internet User msfu666, I mentioned that I sometimes give out FCSIM1 cards free of cost to certain recipients, but I did not elaborate on the conditions. I did not spell out the conditions because I hadn't actually given much thought to what they should be - but thinking about it now, I realize that only one condition would actually make sense. My FCSIM1 cards are good for one and only one purpose: operating your own GSM network (presumably with Osmocom CNI software, no idea if OpenBTS/YateBTS would work or not) *for the purpose of* providing service specifically to vintage handsets. Therefore, the condition becomes quite simple: if there is anyone here besides just me who operates their own Osmocom-based GSM network _specifically for the purpose_ of providing service specifically to _vintage_ GSM handsets and you would like some of my FCSIM1 cards, please let me know and I'll send you a few. What are vintage GSM handsets? For the present purpose, we can define a vintage GSM handset as being one that: a) has a 2FF SIM socket, as opposed to 3FF or 4FF or eSIM; b) has a 2G-only radio; c) does not speak UICC/USIM protocol, only GSM 11.11 SIM. If anyone besides me operates their own GSM network specifically for the purpose of providing service to (or just playing with) such vintage handsets, then FCSIM1 cards would be a good choice for such operation: hence if you would like some, you can have them for the cost of shipping. OTOH, if you operate your own network, even if it's a 2G network radio-wise, for some purpose other than exclusively serving or playing with vintage handsets, then my FCSIM1 cards will NOT be a good choice for your applications. Specifically, if you are going to connect any kind of "modern" phones to your network, even if it's 2G RAN, those "modern" phones will want 3FF or 4FF SIMs - but my FCSIM1 cards are 2FF only, and thus a poor choice for such usage. Sincerely, Lady Mychaela Nadezhda Falconia, Mother of FreeCalypso, Dame of the Order of 2G, Champion of Published Source Code

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