OpenBSC April 2024

openbsc@lists.osmocom.org

11 participants
25 discussions

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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OpenBSC April 2024