OpenBSC

openbsc@lists.osmocom.org

4315 discussions

Virtual layer 1 - Questions
by Sebastian Stumpf 03 Mar '17

03 Mar '17

Hi, The virtual layer 1 is currently in a state where the l23 app can successfully connect to the bts and most of the signaling messages will be forwarded and handled. TCH is not yet implemented. I have some problems still, not knowing if these are caused by configuration problems or my coding :). - Trying to initiate a call via the mobile vty will result in VTY: call 1 123 OsmocomBB# % (MS 1) % Call has been rejected call 1 123 OsmocomBB# % (MS 1) % Call has been released And no actual call setup message is transfered over the Um interface. What could be reasons for that? I am using the test-sim option the mobile app offers. - Occasionaly the T3210 timer is fired, which causes a new registering within the network. LOG: gsm48_mm.c:336 timer T3210 (loc. upd. timeout) has fired How can i prevent that? - I did not implement a tdma or multiframe scheduler in the mobile uplink as the logical channel is directly put to the gsmtap-header and thus known by the bts. As Harald used a multiframe based scheduling for the bts downlink, i wonder if this might be necessary, though. To submit msgs with the correct frame number for example. - In my wireshark capture files, the gsmtap messages sent over the multicast sockets are only recognized as UDP messages. I have to "cast" them with the wireshark context menu "Decode as...". Why? I would be super happy if someone of you could check out my project (osmo-bts, branch stumpf/virt-phy + osmocom-bb, branch stumpf/virt-phy) try to run it with the config files lying within the project folders and tell me the problems they see :). Here you can find a wireshark capture file of 2 mobiles connecting to a virt bts. I also tried to init calls from both of them but the call setup is not send. https://www.dropbox.com/s/2ccky4ljc8ngahz/mobilex2--ms-virt--bts-virt--bsc-… Kind Regards, Sebastian Stumpf

2 7

how to stop paging
by Neels Hofmeyr 02 Mar '17

02 Mar '17

I have a general question about the Paging procedure, specifically about how to stop paging. In libbsc, we have Paging management that receives a request to Page from the MSC and then repeatedly Pages the MS on all BTSes N times or until told to stop. In the NITB, we have code closely tied to the BSC and all BTS management, so that when we receive a Paging Response, we can right away stop sending Paging Commands on all BTSes. So can the standalone-BSC: it stops paging when it received a Paging Response. In OsmoMSC with Iu- and A-interfaces, that's not possible. Looking in 08.08, there seems to be no A-interface message that tells the BSCs "thank you, you can stop paging now". If one BSC or RNC has relayed back a Paging Response from one of the cells, the MSC has no way to tell the other base stations that it's fine to stop sending dozens of Pagings out for "minutes", which would be useless now anyway because the MS has called back via another base station already. Is that a fact of life? We continue Paging in all cells where the MS is not visible? Should the BSC/RNC part of the network page only once, so that "stop paging" is a no-op? Of course we first check which LAC the MS was first seen on and page only there. Is the idea to send paging to one cell, and that cell stops Paging by itself when it received a Paging Response that it relays to the MSC? But IIRC Paging is supposed to spread out across other base stations if at first it didn't succeed -- I recall to have read that in HNB-GW specs or somewhere close to that. Our OsmoHNBGW so far simply Pages everywhere. The practical reason I'm asking is that in the msc_vlr tests, I so far explicitly check whether the "stop paging" function was called. Now on the Iu branch, without libbsc, there is no such function. Should I drop those checks because we will never have that? Or should I add some shim function we call just for the tests so far, which will at some point tell the base stations that Paging has concluded? Thanks for any hints, ~N -- - Neels Hofmeyr <nhofmeyr(a)sysmocom.de> http://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Alt-Moabit 93 * 10559 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschäftsführer / Managing Directors: Harald Welte

1 0

my patches prioritized
by Neels Hofmeyr 02 Mar '17

02 Mar '17

I currently have a whole series of patches on gerrit, many of which fail to build. Here are the pivotal ones I am waiting for, the other patches can be mostly ignored until these are through: https://gerrit.osmocom.org/1682 (struct bsc_subscr) Waiting for a comment. VLR and 3G branches build on it. I'm happy to change the patch, but not sure whether I really have to. IMHO there are benefits to this unusual way, but one word ("no") is enough. https://gerrit.osmocom.org/1923 (cosmetic prep for 1924) https://gerrit.osmocom.org/1924 (python tests: VTY connection speedup) These two are needed for the openbsc python tests speedup patches to work. https://gerrit.osmocom.org/1962 (explicitly terminate ctrl_type_vals[]) https://gerrit.osmocom.org/1940 (find unterminated value strings) The first is a fixup for the second to work, the second one is needed for all of the other value_string topic patches to work. I'd like to add this check to jenkins now, so that all incoming value_string[]s are validated. https://gerrit.osmocom.org/1906 (python tests from separate build dir) I usually build 2G and 3G separately, and I'd like to run the py tests in each dev cycle, now that they are faster. So I'd love to merge this. Hope this helps to save some time... ~N

1 0

libosmo-netif failed on both jenkins FreeBSD and xUbuntu_16.04/i586
by Neels Hofmeyr 28 Feb '17

28 Feb '17

It seems to be a sporadic failure due to timing. Kicking off the same build on jenkins resulted in success. Can anyone relaunch the OBS build? I'm not too familiar with it... http://jenkins.osmocom.org/jenkins/job/libosmo-netif/ https://build.opensuse.org/package/live_build_log/network:osmocom:nightly/l… Also, it would actually be nice if the opensuse builds also printed all test logs as in osmo-ci/scripts/cat-testlogs.sh -- if anyone knows how and has the time to insert such, that would be great. (git clone https://gerrit.osmocom.org/osmo-ci) Thanks, ~N

2 1

Handover and load balancing on SysmoBTS 2050
by Keith 27 Feb '17

27 Feb '17

Hi list, Hi all. This is quite Rhizomatica, or at least litecel 2050 specific, please excuse me for that. I also don't know, maybe it applies to other use cases. Rhizomatica has one community where an attempt was made to increase coverage at the same time as capacity, by installing two 2050s with a somewhat overlapping coverage area. We have currently plans to do the same in other places. The goal of this email is to try to establish the work needed to be done in order to fix what I outline below, I may just be lacking knowledge in some cases, in other It seems we need to implement some things. I have grabbed fairwaves' meas_json and meas_web and modified a little to give me a visualisation of the neighbour meas reports. So my first doubt is about idle cell reselection on the part of the MS. It doesn't seem to be operating quite as I would imagine it should and I am wondering is there any parameter that might make a difference, such as cell_identity? Is cell reselection hysteresis/offset relevant when handover is disabled? These parameters are not described in the manual. If I understood them I could update that. In the meantime, we seem to be getting reports from users that "the signal is weak" near what I might call the secondary BTS. At the same time, user reports are not terribly reliable. However what seems to be happening is that the MS is camped on the primary BTS, subsequently they have moved away so their handset is showing less 'bars'. I'm sometimes seeing TCH in use on the primary BTS that are showing neighbour measurements from the secondary that are more favourable. Of course, I am often seeing messages such as: handover_decision.c:203 (bts=3,trx=0,ts=2): Cell on ARFCN 242 is better: Skipping, Handover disabled Obviously, this makes sense, and I am not sure why historically we have handover disabled, I presume it is issues with rtp, although we are using the rtp_proxy. I don't have two BTS so I can't test locally here. Could anybody comment on the state of that? I am assuming that there is no way we can do load balancing unless we first have handover enabled, at the same time it is unclear to me if it will even work with handover. I believe this is called "Traffic Handover" Is this already implemented in the BSC? As in, can the BSC assign a channel on another ARFCN to the MS if the current ARFCN (the one the MS makes the access request on) has no TCH available? I also have a doubt about operation with a Litecel/2050. Obviously you don't really want rescue handover operating between the two BTS that are present in the Litecel as it is the same antenna, and this shouldn't happen anyway as the signal levels should never be sufficiently different, but we do want load balancing handover. I do see "no resources available" log messages, (especially related to the BROKEN channels issue) when one BTS in a litecel has no more capacity but the other does, so it would seem that the BSC is not managing this. Is that correct? Would it be correct to assume that maybe some handover rules are required that would specify: Handover from BTS 0 to BTS 3 but not from BTS 0 to BTS 1? Finally, I have a doubt about the rtp proxy mode. Was it ever discussed to implement SIP Mobility aka re-Invite in order to be able to do BTS-MGW rtp and also handover? This would seem to me to be a good thing to have? k/

5 14

vlr+hlr: Insert Data
by Neels Hofmeyr 27 Feb '17

27 Feb '17

What should we do if the HLR sends no Insert Data? When a subscriber does a Location Updating, the VLR sends a Location Updating request to the HLR. The HLR typically responds with a Location Updating Result as success and, in a *separate* message, sends an Insert Data to the VLR to tell it the subscriber's MSISDN. So it is possible to do a successful Location Updating without being told the MSISDN (as my test verifies). What should the VLR do if it never receives the Insert Data from the HLR? In that case the subscriber is attached but cannot be reached by MSISDN. Should we actively wait for Inser Data and reject the subscriber if not successful? It would be fairly easy to just send the MSISDN along in the Location Updating Result. Why this separate message? Thx, ~N

4 7

Ki and OPC values change when programming MCC and MNC
by Giselle Gonzalez lopez 27 Feb '17

27 Feb '17

Hello, We have already contacted our SIM cards provider (sysmocom), and they have referred us towards this Mailing List. We have purchased sysmoUSIM-SJS1 cards and we are having the following problem when trying to program them: We want to change the MCC and MNC values to the ones of our OpenAirInterface LTE system, and Ki and OPC of the SIM card are changing despite we are not intending for that to happen. The main issue with this behavior is that as we have two sets of Ki and OPC values, when we are going to register the user in the LTE database, we don't know for sure which set of parameters we are supposed to introduce. Here on I'll describe the configuration we are using and the commands introduced when programming the SIM cards: As programming software we are using PySIM. The default parameters of the SIM we are programming are: ADM: 20168462 ICCID: 8988211000000099120 Ki: 5B868E2B30C61190ABEFBA1CA6F6D56F OPC: B3425076F23BA6054557FA359B4F9C0C The parameters we are meaning to program are: MCC: 001 MNC: 01 IMSI: 001010000009912 The command we are using to program in the SIM card is: ./pySim-prog.py -p 0 -a 20168462 -x 001 -y 01 -t sysmoUSIM-SJS1 -i 001010000009912 -s 8988211000000099120 And after programming the card, we are getting this: [image: Imágenes integradas 1] Do you what's the reason why this is happening? Thank you very much for your time Best regards, Giselle Glez

4 8

OsmoHLR and IPA unit id
by Neels Hofmeyr 25 Feb '17

25 Feb '17

I just ran my first tests of both OsmoNITB and OsmoSGSN connecting to OsmoHLR. It turns out OsmoHLR uses the ipaccess_unit data a.k.a. CCM (whatever CCM means) to route GSUP replies back to its sender. It looks like "NAME-00-00-00-00-00-00". However, all of our GSUP client code simply sets the unit id to: "SGSN-00-00-00-00-00-00". The result is that the VLR never receives an UPDATE LOCATION RESULT, because it is sent to the SGSN instead, since that was the first one to say that it is "SGSN-00...". I would extend the GSUP clients to allow setting an ID from VTY, or maybe a random ID. At this point it would suffice to make the MSC side say it is "MSC-00-00-00-00-00-00" but that's beside the point. Do we really want to do that? Any peer could come along and say it is someone else, very easy to misconfigure (and not very security sensitive when thinking of OAP -- which we're not using but maybe we will one day). For some messages, OsmoHLR uses the conn pointer from msg rx to route the response back -- that works. AFAICT it just receives messages and replies to them right away (but haven't seen / understood all of it). For the case of the UPDATE LOCATION RESULT, it would also be possible to use the same conn pointer, but the code chooses to resolve by id and then sends to the wrong peer. If it used the peer's IP address and port instead, things would work out. With the attached and possibly very stupid patch, OsmoHLR works for me with both MSC and SGSN talking to it even though they have identical IPA IDs: I bluntly store the conn in struct lu_operation and re-use it later. Which way shall we resolve this? ~N

2 2

Re: OpenBSC Digest, Vol 28, Issue 20
by Rajitha peiris 25 Feb '17

25 Feb '17

Hi all I have got trough the pcs 1900 nano bts if you have any doubts pls let me ... and these days I am trying to resolves OML issues with RBS 2308 ericson bts Thank you very much Regards Rajitha peiris Sent from my iPhone On Feb 24, 2017, at 9:42 PM, "openbsc-request(a)lists.osmocom.org<mailto:openbsc-request@lists.osmocom.org>" <openbsc-request(a)lists.osmocom.org<mailto:openbsc-request@lists.osmocom.org>> wrote: Send OpenBSC mailing list submissions to openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org> To subscribe or unsubscribe via the World Wide Web, visit https://lists.osmocom.org/mailman/listinfo/openbsc or, via email, send a message with subject or body 'help' to openbsc-request(a)lists.osmocom.org<mailto:openbsc-request@lists.osmocom.org> You can reach the person managing the list at openbsc-owner(a)lists.osmocom.org<mailto:openbsc-owner@lists.osmocom.org> When replying, please edit your Subject line so it is more specific than "Re: Contents of OpenBSC digest..." Today's Topics: 1. Re: Ki and OPC values change when programming MCC and MNC (Holger Freyther) 2. Re: Virtual layer 1 - Questions (Harald Welte) 3. OsmoHLR and IPA unit id (Neels Hofmeyr) 4. Re: Handover and load balancing on SysmoBTS 2050 (Keith) 5. Re: OsmoHLR and IPA unit id (Harald Welte) 6. Re: Handover and load balancing on SysmoBTS 2050 (Keith) ---------------------------------------------------------------------- Message: 1 Date: Thu, 23 Feb 2017 15:25:56 +0700 From: Holger Freyther <holger(a)freyther.de<mailto:holger@freyther.de>> To: Neels Hofmeyr <nhofmeyr(a)sysmocom.de<mailto:nhofmeyr@sysmocom.de>> Cc: "openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org>" <openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org>> Subject: Re: Ki and OPC values change when programming MCC and MNC Message-ID: <31579AC7-F837-49F1-9EDC-C0B8D2CCC85C(a)freyther.de<mailto:31579AC7-F837-49F1-9EDC-C0B8D2CCC85C@freyther.de>> Content-Type: text/plain; charset=us-ascii On 23 Feb 2017, at 09:53, Neels Hofmeyr <nhofmeyr(a)sysmocom.de<mailto:nhofmeyr@sysmocom.de>> wrote: On Wed, Feb 22, 2017 at 05:06:20PM +0100, Sylvain Munaut wrote: --help will tell you defaults for Ki and OPC is to randomize ... Ah, indeed, I never saw that. Could also be misunderstood. IMHO it should say right at the top that you normally want to pass -k and -o when calling pysim. After all, none of the other options do that. anyway... "normally".. for the batch mode as used at XC3 events the "normal" is to generate a random KI, you wouldn't want to do that by hand 4k times. :) holger ------------------------------ Message: 2 Date: Thu, 23 Feb 2017 15:41:24 +0100 From: Harald Welte <laforge(a)gnumonks.org<mailto:laforge@gnumonks.org>> To: Sebastian Stumpf <sebastian.stumpf87(a)googlemail.com<mailto:sebastian.stumpf87@googlemail.com>> Cc: openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org>, baseband-devel(a)lists.osmocom.org<mailto:baseband-devel@lists.osmocom.org> Subject: Re: Virtual layer 1 - Questions Message-ID: <20170223144124.mdba7w7avdujy23g@nataraja> Content-Type: text/plain; charset=us-ascii Hi Sebastian, On Sun, Feb 19, 2017 at 06:16:01PM +0100, Sebastian Stumpf wrote: I also see that the RACH requesets all are sent with a bogus frame number: 42. This will not work. The RACH request needs to be sent with the current frame number at the time being. I fixed that and calculate the proper rach fn like in https://github.com/osmocom/osmocom-bb/blob/master/src/target/firmware/layer… good. Also, RACH retransmissions are happening way too quick. Calculating a proper frame number didn't fix the fast retransmissions. They are caused by sending the channel request over the virtual um immediately after getting the rach-request from layer23. Thus also the rach-confirm is sent to l23 immediately, so layer23 thinks "oh fine its already transmitted" and will generate the next rach-request for my layer 1. i see. the confirmation should probably be delayed somehow. As a quick intermediate hack you might simply add a timer. I think one can do without on the MS side, but then the BTS must basically queue the incoming frames until the respective frame number indicated in the frame matches the current frame number. I think to fix the problem with the quick retransmission , I need some type of scheduling. Because if I queue the incoming uplink-msgs in the bts-virtual-layer1 instead, I don't know when they are processed on the ms side and thus don't know when to send the rach-confirm to layer23... My idea for a simple scheduler would be: -- no timing and timer interrupts on ms side, but just set the current fn in the ms state each time we receive a message on downlink to the fn of the received message, which is accessible in the gsmtap header. yes, that makes sense. -- queue the outgoing uplink messages with their confirm callback to l2 and process all that with a smaller fn than the current fn in the scheduling function. yes, but please keep in mind that the frame number is wrapping every so often, so "smaller" must consider that modulo-arithmetic, or you will (after fn wrap) have pending downlink messages for much higher fn which are not sent as the wrapped fn is now very small. -- calling the scheduling function each time we receive a msg on downlink (so I do not need to handle timer interrupts) yes. I think it is reasonable to not have any actual timers on the ms side and always depend on the frame numbers in the downlink messages from the BTS. After all, in the worst case you have periodic messages like the BCCH messages that can be used to update the fn. I hope that will be sufficent and try it out tomorrow. I am a bit afraid of trouble caused by the frame number skipping values with the upper incrementation logic. I don't think skips are that problematic. But then, I haven't tried it ;) -- - Harald Welte <laforge(a)gnumonks.org<mailto:laforge@gnumonks.org>> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6) ------------------------------ Message: 3 Date: Fri, 24 Feb 2017 06:43:26 +0100 From: Neels Hofmeyr <nhofmeyr(a)sysmocom.de<mailto:nhofmeyr@sysmocom.de>> To: openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org> Subject: OsmoHLR and IPA unit id Message-ID: <20170224054326.GB1368(a)my.box<mailto:20170224054326.GB1368@my.box>> Content-Type: text/plain; charset="us-ascii" I just ran my first tests of both OsmoNITB and OsmoSGSN connecting to OsmoHLR. It turns out OsmoHLR uses the ipaccess_unit data a.k.a. CCM (whatever CCM means) to route GSUP replies back to its sender. It looks like "NAME-00-00-00-00-00-00". However, all of our GSUP client code simply sets the unit id to: "SGSN-00-00-00-00-00-00". The result is that the VLR never receives an UPDATE LOCATION RESULT, because it is sent to the SGSN instead, since that was the first one to say that it is "SGSN-00...". I would extend the GSUP clients to allow setting an ID from VTY, or maybe a random ID. At this point it would suffice to make the MSC side say it is "MSC-00-00-00-00-00-00" but that's beside the point. Do we really want to do that? Any peer could come along and say it is someone else, very easy to misconfigure (and not very security sensitive when thinking of OAP -- which we're not using but maybe we will one day). For some messages, OsmoHLR uses the conn pointer from msg rx to route the response back -- that works. AFAICT it just receives messages and replies to them right away (but haven't seen / understood all of it). For the case of the UPDATE LOCATION RESULT, it would also be possible to use the same conn pointer, but the code chooses to resolve by id and then sends to the wrong peer. If it used the peer's IP address and port instead, things would work out. With the attached and possibly very stupid patch, OsmoHLR works for me with both MSC and SGSN talking to it even though they have identical IPA IDs: I bluntly store the conn in struct lu_operation and re-use it later. Which way shall we resolve this? ~N -------------- next part -------------- A non-text attachment was scrubbed... Name: 0001-RFC-add-the-osmo_gsup_conn-directly-to-the-lu_operat.patch Type: text/x-diff Size: 2550 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20170224/121d8d06/at…> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20170224/121d8d06/at…> ------------------------------ Message: 4 Date: Fri, 24 Feb 2017 16:42:35 +0100 From: Keith <keith(a)rhizomatica.org<mailto:keith@rhizomatica.org>> To: Alexander Chemeris <alexander.chemeris(a)gmail.com<mailto:alexander.chemeris@gmail.com>> Cc: OpenBSC Mailing List <openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org>> Subject: Re: Handover and load balancing on SysmoBTS 2050 Message-ID: <39e245c4-ba1a-600b-8e38-cb300c10133f(a)rhizomatica.org<mailto:39e245c4-ba1a-600b-8e38-cb300c10133f@rhizomatica.org>> Content-Type: text/plain; charset=utf-8 Hi Alexander, seeing as how you came in on the thread, as a side topic, you may have noticed I mentioned meas_json and meas_web in the OP. I fixed up a small thing with meas_json that was producing unparseable json in the neighbours array. I also did some stuff server side to filter for either SDCCH or TCH, although I think I would make this a clientside javascript filter option, rather than running multiple websocketd I added the neighbour levels to the displayed data. I hardcoded the ARFCNs for the site in question, but I would make that happen dynamically. I found this quite useful for monitoring in relation to analysis on this site and the would-be handover scenario. I'm wondering what to do with this work. Should I make a commit of meas_json to master? In that case I would appreciate some minor help getting the Makefile right. Maybe meas_json is not a candidate for the master branch, as it doesn't currently do anything particularly useful without the external dependencies, ie meas_web and websocketd or alternative. I can publish my work on meas_web to github. Keith. ------------------------------ Message: 5 Date: Fri, 24 Feb 2017 16:53:03 +0100 From: Harald Welte <laforge(a)gnumonks.org<mailto:laforge@gnumonks.org>> To: Neels Hofmeyr <nhofmeyr(a)sysmocom.de<mailto:nhofmeyr@sysmocom.de>> Cc: openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org> Subject: Re: OsmoHLR and IPA unit id Message-ID: <20170224155303.tuidxovd4qbzp5go@nataraja> Content-Type: text/plain; charset=us-ascii Hi Neels, IPA CCM made sense on the Abis interface, where each BTS reports with its unit_id and MAC address. I'm not quite sure how much sense that makes in the core network. I also don't know if existing implementations of e.g. A interface over IPA multiplex actually use it. In terms of future outlook, the MSC/VLR/SGSN should register at the HLR with some kind of identity. In MAP, it is the SCCP Address that is used for this purpose. In absence of SCCP on GSUP, I used the CCM identity as a replacement. However, it is used as an opaque string, so that any GSUP/MAP gateway might simply translate the SCCP address into a string of its choosing, and then talk to OsmoHLR. OsmoHLR would then simply do a strcmp() on the string to match the identity. Sooner or later, OsmoHLR will have to store this identity in the database, e.g. for imlpementing message-waiting-lists of SMSCs in case of MT-SMS from real SMSCs. All-in-all, I think the string approach is not too bad in terms of keeping GSUP simple while having a clan approach to interworkng with MAP. On Fri, Feb 24, 2017 at 06:43:26AM +0100, Neels Hofmeyr wrote: I just ran my first tests of both OsmoNITB and OsmoSGSN connecting to OsmoHLR. It turns out OsmoHLR uses the ipaccess_unit data a.k.a. CCM (whatever CCM means) to route GSUP replies back to its sender. It looks like "NAME-00-00-00-00-00-00". However, all of our GSUP client code simply sets the unit id to: "SGSN-00-00-00-00-00-00". The result is that the VLR never receives an UPDATE LOCATION RESULT, because it is sent to the SGSN instead, since that was the first one to say that it is "SGSN-00...". this is of course not good. I would extend the GSUP clients to allow setting an ID from VTY, or maybe a random ID. At this point it would suffice to make the MSC side say it is "MSC-00-00-00-00-00-00" but that's beside the point. A random ID would not be permissible, as it has to be persistent accross MSC/VLR/HLR re-starts, in order to make above-mentioned mechanisms working. I would say, why not simply use the same approach as in OsmoBTS, i.e. use the MAC address (together with the MSC or SGSN prefix). The MAC address is unlikely to change frequently or on short notice. For people who know what they're doing, we can have a VTY command to override the identity with a manually-specified string. If that option is not set, the default "(SGSN|MSC)-MAC" is used. Do we really want to do that? Any peer could come along and say it is someone else, very easy to misconfigure (and not very security sensitive when thinking of OAP -- which we're not using but maybe we will one day). I don't think we are aiming for anyone to use those protocols on public[ly accessible] networks. There's no message authentication or other cryptographic protection anyway. OAP seems like a funny but futile minor obstacle, but nothing that can provide any reasonable level of security. For some messages, OsmoHLR uses the conn pointer from msg rx to route the response back -- that works. This should be done in all request-response style procedures, I think. AFAICT it just receives messages and replies to them right away (but haven't seen / understood all of it). For the case of the UPDATE LOCATION RESULT, it would also be possible to use the same conn pointer, but the code chooses to resolve by id and then sends to the wrong peer. If it used the peer's IP address and port instead, things would work out. Looking up by ID would also work in case meanwhile the old connection has died and a new connection has been established With the attached and possibly very stupid patch, OsmoHLR works for me with both MSC and SGSN talking to it even though they have identical IPA IDs: I bluntly store the conn in struct lu_operation and re-use it later. For synchronous responses (i.e. no asynchronous activity in between) this will work. So I think it's an optimization for those cases, and we shouldn't rely on this to always work for all transactions at all time in the future. Rather, we should make sure it works even without that optimization? -- - Harald Welte <laforge(a)gnumonks.org<mailto:laforge@gnumonks.org>> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6) ------------------------------ Message: 6 Date: Fri, 24 Feb 2017 17:12:02 +0100 From: Keith <keith(a)rhizomatica.org<mailto:keith@rhizomatica.org>> To: Harald Welte <laforge(a)gnumonks.org<mailto:laforge@gnumonks.org>> Cc: OpenBSC Mailing List <openbsc(a)lists.osmocom.org<mailto:openbsc@lists.osmocom.org>> Subject: Re: Handover and load balancing on SysmoBTS 2050 Message-ID: <ca4d6dc2-fa43-8eaa-8c39-821939d87e52(a)rhizomatica.org<mailto:ca4d6dc2-fa43-8eaa-8c39-821939d87e52@rhizomatica.org>> Content-Type: text/plain; charset=windows-1252 On 21/02/2017 16:14, Harald Welte wrote: Just a quick response: jolly implemented "traffic handover" aka "load balancing" 3 years ago as part of a branch (I believe for a customer), but unfortunately this never was merged back to master. Reading the commit log, this looks terrific... Meanwhile, we already have all the code for execution of hand-overs in place. We also have dynamic timeslots in place. So the "mechanics" should all be there to add the two missing features from those old branches: a) de-fragmenting of channels (i.e. merging two separate TCH/H into one timeslot, so the other timeslot can be switched to TCH/F or PDCH on demand b) load/traffic based hand-over So essentially everything I was talking about is already implemented! My question then would be, and I understand maybe the answer is not so easily available without a full code review, but Was it unfortunately never merged back to master because Simply no one ever made the effort to do so. OR There were problems with the code, disagreement on the implementation or incompatibilities with other developments etc.. If it's the former, I'll have a go at this. If it is the latter, it's probably beyond my skills. The general strategy I would normally assume is to * switch to half-rate channels with AMR whenever possible * use dynamic channel switching to switch between TCH/H (default) and TCH/F (if neded) Absolutely, I must revisit this one. It was shelved for us due to my understanding a few months ago that if we implemented AMR, then we couldn't also use FR. As that's all now resolved, I can implement, test and report. :-) ------------------------------ Subject: Digest Footer _______________________________________________ OpenBSC mailing list OpenBSC(a)lists.osmocom.org<mailto:OpenBSC@lists.osmocom.org> https://lists.osmocom.org/mailman/listinfo/openbsc ------------------------------ End of OpenBSC Digest, Vol 28, Issue 20 ***************************************

2 1

Re: Handover and load balancing on SysmoBTS 2050
by Alexander Chemeris 25 Feb '17

25 Feb '17

Hi Holger, On Feb 22, 2017 1:02 AM, "Holger Freyther" <holger(a)freyther.de> wrote: > On 21 Feb 2017, at 21:40, Keith <keith(a)rhizomatica.org> wrote: Hi Keith, > On the question about SIP re-invite, I am talking about operating > without rtp_proxy, so that one can have the advantage of BTS<->BTS RTP > streams at the same time as handover. From what I've read, this is quite > feasable, as part of the SIP spec. > I think this is already considered as part of the development of the > osmo-sip-connector, which is a project I really want to see moving > forward and hope to find time to contribute to over the next few months. yes for the osmo-sip-connector I have ignored the topic of handover. In general I try to see how long I get away with not having to touch the UDP/RTP streams. You don't really need to touch RTP stream if you do re-invite. In case of hand-over the new BTS might send from a different src IP, src Port and will most likely have a new SSRC, timestamp seqno. It is a bit of a question of how "your" PBX will handle it. I can see a couple of outcomes. a.) It has some support for "NAT" handling and will just use the new stream and return packages to the new src IP/src port. It might go back and forth but at some point the old bts will stop sending things. b.) It will accept the new stream but will try to send to the old BTS. The we would have one-way audio. c.) It will reject it as it is a unknown src ip/port. I think for b.) and c.) we will require SIP re-invite but also need to look at the AoIP spec to see if they say how to handle this scenario. But that depends on how the PBX handles this as well. So it means for handover we always need to look at BSC/SIP+PBX and how it is handling SDP/RTP. If I remember correctly, (b) is what's going to happen if a client is following vanilla SIP spec, because changing RTP IP/port requires updating SDP which is done with a re-invite. (a) is a hack supported by many SIP clients, but it may depend not only on PBX, but also on its configuration parameters, on SBCs used on a network, etc So if you want to be nice to the other party and follow the spec, it's better to do re-invite :) Btw, re-invite will need to be implemented anyway if you want to support call hold. Please excuse typos. Written with a touchscreen keyboard. -- Regards, Alexander Chemeris CTO/Founder Fairwaves, Inc. https://fairwaves.co

3 5

Jump to page:

2026

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

OpenBSC