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4315 discussions

GSMTAP new version (3?)
by Mauro Levra 06 May '24

06 May '24

Dear Osmocom developers, In our project we have been using the gsmtap pseudo-header to store UMTS and LTE signalling traces in pcapng format. This is very efficient compared to our previous implementation based on DLT_USER, and thanks to the gsmtap dissector, it allows any *shark app to read our output file. When looking for the proper type and sub_type for NR signalling traces, I discovered they are not yet part of the standard. I found several threads of discussion about this, from about 2017 onwards, and I understand it is a matter of time and resources if the version 3 of GSMTAP has not been released. The most interesting feature I have read about is the ability to extend the header with a TLV approach. EARFCN, eNodeB-ID, PCI, are useful metadata we would like to add to our traces. In an ideal world, I would like things to be put in motion so that a new version of GSMTAP could see the light. More humbly, I ask you what kind of help is needed. Are you waiting for a draft specification? Are all requirements well known? I suppose that LTE and NR are not the main focus today for liboscmocore development, but there are many projects out there waiting for the GSMTAP format to be updated. Thanks! Mauro

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asynchronous non-blocking I/O
by Neels Hofmeyr 01 May '24

01 May '24

Hi all, we are currently having lots of discussions on (non-)blocking I/O. I'd like to put these thoughts out there for that discussion, because there seems to be a misunderstanding in terms. Blocking never goes away, it is just reduced to other orders of magnitude. Types of "blocking": - blocking or non-blocking pipes: will writing to a file or socket stop the program until the pipe is ready for writing? (basic "OS level" I/O) - synchronous or asynchronous event handling: will the program stop until a remote side has responded, or can the program handle other events in the meantime? (one job queue, one worker == osmo_select_main()) - sequential or parallelized event handling: can events be handled concurrently, or just one after the other? (one or more job queues, more than one worker) - concurrent access of resources: a given resource is not thread-safe, hence one thread needs to wait for the other to release a resource lock. (This is always present, the aim is to hit a sweet spot of least locking.) In osmo programs I have worked on, we do the first two, but not the other two. Asynchronous event handling is the bare minimum for a server program to be functional. Non-blocking pipes is a common addition that is easy to do. From then on we enter the world of parallelization, and things get very complex very quickly. It is possible to cause more blocking than before. It is possible to significantly increase the load, instead of improving. I am familiar with parallelized non-blocking event handling and I/O, from realtime audio+video+control hacking. We do not use any of these techniques in osmo programs I have worked on -- for good reasons, I thought. The spectrum, from most blocking to most non-blocking: - single-threaded, single queue with async defer; - task queue with multiple worker threads; - scheduling based on fairness or urgency; - map/reduce across a cloud, in a functional language. We're almost all the way to the blocking end of the parallelization spectrum. So far I thought that this was a conscious choice. Async-but-blocking is low complexity, with large benefits in maintainability and stability. Example: If we have pending, say, 10 incoming packets on three different links, we handle each packet one by one when it is its turn. If one subscriber's incoming measurement report triggers longish handover calculations, any events like an MGCP ACK or SCCP CC for some other subscribers will have to wait in line, even though they might take a thousand fold less time to complete. OsmoBSC works well in that fashion, even for hundreds of cells and multiple MSC: compared to audio+video+control, CNI signalling has huge tolerances on timing. This is why 3GPP separates control-plane from user-plane. It is important to balance all of these aspects! --- It was mentioned somewhere that our VTY is both asynchronous and non-blocking. I do not agree at all and would like to explain, as an example of the above. Our vty server is NOT asynchronous. When a VTY request comes in, the vty function must directly vty_out() the response. We cannot defer the VTY response asynchronously like any other protocol can (see example below). Our VTY structures, and the program-specific internal state that VTY manipulates and queries, are not thread-safe. The VTY server cannot be parallelized as it is now. A contrived example: Let's say we wanted to query nft counters from a VTY command: * read VTY command from user, * do some nft command asynchronously, * and print back the result when nft is done. Naively, we could store the struct vty * somewhere, and exit the vty handling function. When nft is done some time later, just vty_out() the result to that struct vty * that we still have from earlier. But there are problems: If the user closed the telnet session in the meantime, this struct vty * is stale and the program will crash. We need a cancel mechanism to avoid that. Also when a VTY command function is done, we directly transmit the next VTY prompt. vty-test scripts (`expect`) won't function properly when more response data arrives after the prompt is received; human users may be confused. So our VTY server is *both* Synchronous and Blocking. It is not trivial to make it async (like all of our other protocols are) and non-blocking (which we have nowhere in osmo-cni yet). --- These are the kinds of mechanisms I care about in our discussions: - "blocking" on what time scale? - tradeoff with code complexity and maintainability. - tradeoff with code stability and determinism. - tradeoff with system performance load due to additional management and caching. One does not simply put things in threads. There are very non-trivial aspects that *always* come with it, one of them is super good, most of them are pretty bad. ~N -- - Neels Hofmeyr <nhofmeyr(a)sysmocom.de> https://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Siemensstr. 26a * 10551 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschaeftsfuehrer / Managing Director: Harald Welte

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error in libosmosccp
by Sandeep Kumar 30 Apr '24

30 Apr '24

Dera Team, I am facing this error. [root@ip-172-31-27-63 libosmo-sccp]# ./configure.ac ./configure.ac: line 1: dnl: command not found ./configure.ac: line 2: syntax error near unexpected token `[libosmo-sccp],' ./configure.ac: line 2: `AC_INIT([libosmo-sccp],' [root@ip-172-31-27-63 libosmo-sccp]# Kindly help here . Thanks . Regards, Sandeep Malik

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New Themyscira specifications for enhanced RTP transport in GSM RAN
by Mychaela Falconia 30 Apr '24

30 Apr '24

Dear Osmocom community, About a year ago I published this specification: https://www.freecalypso.org/specs/tw-ts-001-v010001.txt TW-TS-001 is a spec, written in 3GPP language style, for enhanced RTP transport of FR and EFR codec frames in an IP-based GSM RAN. I got OsmoBTS support for this RTP extension on branch falconia/rtp_traulike, but I never submitted it to Gerrit for mainlining: when I mentioned it in OsmoDevCall in 2023-06, the feedback from Harald was that the extension would need to be somehow requested from the CN via signaling, rather than manually switched on via OsmoBTS local vty. Since then I have familiarized myself with 3GPP specs for AoIP user place (TS 48.103 and TS 26.102 it refers to), and I see the problem with my initial "brute force" method: when 3GPP specs explicitly call for standard RTP formats at the AoIP interface, intentional deviations from that standard need to be negotiated/signaled in some clean manner. So here is my new solution: https://www.freecalypso.org/specs/tw-ts-001-v010100.txt https://www.freecalypso.org/specs/tw-ts-002-v010100.txt https://www.freecalypso.org/specs/tw-ts-003-v010001.txt There are 3 new specs in the above set: * The new version of TW-TS-001 clarifies some deficiencies in the original, and refers to TW-TS-003 for how the enhanced RTP format is to be invoked at the AoIP interface. * TW-TS-002 is a new spec that does for HRv1 codec what TW-TS-001 does for FRv1 and EFR. The enhanced RTP payload format here is an extension of RFC 5993, which I named super-5993. * TW-TS-003 is an extension to BSSMAP for communicating the use of enhanced RTP payload formats between MSC and BSS. I will now be preparing some patches for TW-TS-003 support - see you in Gerrit code review soon. :-) With love and greetings from Themyscira, Mother Mychaela

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Looking for captures of TRAU-UL frame stream from E1 BTS
by Mychaela Falconia 28 Apr '24

28 Apr '24

Hello Osmocom community, Would anyone here happen to have a capture of a TRAU-UL frame stream from some historical E1 (or T1) BTS? And if no already existing UL capture is available, if I found someone with access to such equipment who would be willing to do a few tests for me, what would be the way to make such capture? I mean raw Abis UL capture, *not* converted to RTP or anything else, and because I don't have any T1/E1 hardware currently, I am not really familiar with Osmocom tools for working with such hw and what tap/trace/capture mechanisms are available. And yes, I see on the wiki page for OsmoDevCon that some E1 BTS hw will be present at the event - but my lack of an updated travel document from USCIS still precludes me from traveling anywhere outside of USA+Canada+Mexico territory. :( M~

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OsmoDevCon talk: Your favorite Osmocom related productivity tips and tools
by Oliver Smith 22 Apr '24

22 Apr '24

Hi all, I'm making a talk about tips and tools for doing more effective Osmocom related development. Some ideas I have for it currently: * how to build your own (deb, rpm) packages with OBS * how to run CI stuff (like the checkpatch linter) locally * running tcpdump over SSH and piping it into wireshark * finding what regression caused a ttcn-3 failure systematically Is there anything (within this list or other ideas) you would find particularly interesting, or boring? If you have a couple of tips or tools to share, and would like to present them yourself: let me know as well, then we could turn this into a quick lightning talk series with multiple presenters. Best, Oliver -- - Oliver Smith <osmith(a)sysmocom.de> https://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Siemensstr. 26a * 10551 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschaeftsfuehrer / Managing Director: Harald Welte

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osmo-bsc, mgw and AoIP Transport Layer Address
by jheyrendt.ext＠orange.com 18 Apr '24

18 Apr '24

Dear experts We try to configure osmo-bsc / osmo-mgw to be able to communicate with ERICSSON MSC/MGW. The UE is well registered but we don't know how to well configure bsc. We have this config file osmo-bsc.cfg: - 172.20.10.10 is a local BSC address to communicate to STP, MSC, MGW osmo-bsc mgw 0 local-ip 172.20.10.10 local-port 2427 remote-ip 172.20.10.10 remote-port 2727 reset-endpoint rtpbridge/* We have on the BSC a local mgw, and here is the osmo-mgw.cfg file: 172.20.10.19 is another address on the BSC towards the osmo-bts-trx. osmo-mgw mgcp domain mgw bind ip 172.20.10.10 bind port 2727 rtp port-range 4002 16001 rtp bind-ip 172.20.10.19 rtp ip-probing rtp ip-dscp 0 rtp keep-alive once rtcp-omit rtp-patch ssrc rtp-patch timestamp no rtp-patch rfc5993hr sdp audio-payload send-ptime sdp audio-payload send-name number endpoints 512 osmux off Sure we made errors and misunderstood. During test call, we can see in the trace, a Call proceeding, then a BSSMAP Assignment Request followed by a BSSMAP Assignment Complete. The problem is that the IP choosen as AoIP Transport Layer Address is the OAM address of the BSC (seen in In GSM A-I/F BSSMAP Assignment Complete trace section - UDP port 4004). How to change this in order to set 172.20.10.10 as the AoIP Transport Layer Address ? Many thanks in advance, best regards Jean-Marc

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Channel Requests not being responded when running CS-only 2G network
by JPichel 07 Apr '24

07 Apr '24

Hi, I am trying to setup a simple Network In The Box 2G network. I am only interested in CS capabilities (voice calls, SMS, USSD). I am currently running the following elements with the default configurations: - osmo-bts-trx (connecting to osmo-trx-uhd driving a USRP B205mini-i) - osmo-bsc - osmo-msc - osmo-hlr - osmo-mgw - osmo-stp I built all the programs from source on Ubuntu 22.04. Everything is running locally on one machine. Everything seems to function correctly at first, but I noticed that sometimes when I try to execute an USSD code or make a call, my Channel Requests are not being responded. I noticed when this happens, osmo-bts shows the following notice: DPCU notice PCU socket not connected, dropping message (pcu_sock.c:1018) As I understand from the documentation (https://osmocom.org/projects/cellular-infrastructure/wiki/Osmocom_Network_I…), this component is not required for circuit switched services as the ones I am requesting, so I do not understand why this is happening. I assume something in the configuration files is telling the BTS or some network element that the PS side of the network is active, but I haven't found anything related to PCU in any of configuration files.

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DevCon: CSFB proposol / a general playground
by Keith 26 Mar '24

26 Mar '24

While I'm here looking at the mailing list, I have been thinking about asking about the following, and no need to delay it, I suppose - Upcoming OsmoDevCon attendees may have noticed the proposed and scheduled session on CSFB testing. Well, since - and sort of because that session was accepted, (and also an iPhone 6 that supports the band of an eNB I have at home dropped into my possession) - I've been prompted to advance my knowledge and understanding of issues, and the iPhone (6 at least) is now doing MO CSFB perfectly, and I think I see what some other observed issues are about. I'm still happy if there's interest to do the session of course, although maybe some might question whether it is more productive to just file tickets/issues and work them out the usual way. This email is not to suggest in any way to cancel the session, but rather to ask if maybe we might expand the scope. I'm thinking for example also testing 2G data. The older basic 2G + GPRS "chocolate bar" type phones I have don't work anymore, they used to. (not sure what one might actually do with such a device and GPRS these days, but that's not the point, right?) Someone (vadim?) brought a 2G (was it a credit card?) terminal once to devcon. Does it work? that kind of thing. So thinking about all this, I'm asking the question of whether there is interest to have a kind of events style setup during the conference. lynxis I think has a server for that, or maybe it's only a VM? I don't mean a distracting always-on setup, and I don't mean to put emphasis on cellular projects. But if we did want to have something multi RAT, available for anybody who might want to glance in that direction (during a USSE for example), then some (small) amount of logistics preparation is necessary, no? Thanks. k.

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PyHSS / pyhss-tool
by Harald Welte 23 Mar '24

23 Mar '24

Hi all, While working with open5gs + kamailio, one traditionally always needed two HSS: * the open5gs one with its mongodb and nodejs hell * the FHoSS one for the kamailio IMS core For some time there's now PyHSS, which supports both EPS and IMS subscriptions, which is of course nice. docker_open5gs meanwhile also has switched to using it as default. The big problem is that it doesn't actually state which license it is under, which makes it legally impossible to [re]distribute it, or to even make a fork of the repository, as that would be a violation of copyright. At least German users are abel to legally use it, as under German copyright law you don't need a license from the copyright holder to use a program that you have obtained legally. In order to automatize the steps described in the open5gs_docker to create subscribers, I've just hacked up a small tool, see https://gitea.osmocom.org/laforge/pyhss-tool/src/branch/master/pyhss-tool.py Using that tool, it's as easy as pyhss-tool.py subscriber-create --imsi 001011111111111 --msisdn 1111 --k 000102030405060708090a0b0c0d0e0f --opc 00000000000000000000000000000000 or pyhss-tool.py subscriber-delete --imsi 001011111111111 to add/remove subscribers. You will still need to manually create the internet and ims APNs via the REST interface; I'll probably also add that capability to the tool. Once it's a bit more tested, I also would like to contribute it upstream, at least once that is possible. To do that I'd have to make a pull request, and making that pull request requires me to create a fork, which is a copyright violation. wtf. If that legal situation has cleared up, it might be worth considering either adding native GSUP support to PyHSS (so it can be used by osmo-{msc,sgsn}, or to have a converter like osmo_gsup2dia (the inverse of the existing osmo_dia2gsup). Regards, Harald -- - Harald Welte <laforge(a)osmocom.org> https://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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