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Bug #5856

closed

Very annoying "this BTS model does not support TSC 7 != BSIC-BCC 0" error.

Added by keith about 1 year ago. Updated 10 months ago.

Status:
Resolved
Priority:
Normal
Assignee:
Target version:
-
Start date:
01/15/2023
Due date:
% Done:

90%

Spec Reference:

Description

Since some months ago, when connecting osmo-bts-sysmo to a remote osmo-bsc that is not directly on the LAN, (and very occasionally on the LAN), but rather on some higher latency link, I am often seeing

common/oml.c:991 OC=CHANNEL INST=(00,00,00): SET CHAN ATTR: this BTS model does not support TSC 7 != BSIC-BCC 0

Seemingly because in the OML bringup we are sending Set CHAN attrs before we have sent Set BTS attrs

I don't know what controls this sequence, but maybe it would be good if that were a little more robust.


Files

happy_bringup.pcap happy_bringup.pcap 21 KB keith, 01/14/2023 11:25 PM
sad_bringup.pcap sad_bringup.pcap 6.08 KB keith, 01/14/2023 11:25 PM
bsic_0.pcap bsic_0.pcap 39.2 KB keith, 01/14/2023 11:48 PM

Related issues

Has duplicate OsmoBSC - Bug #5977: osmo-bsc unable to bring up osmo-bts-sysmo (BSIC/TSC)Closedpespin03/27/2023

Actions
Actions #1

Updated by keith about 1 year ago

It might be of help to observe what happens if the TSC is set to 0 so that the OML bring up is not terminated, eventually we do send the set BTS attr. See bsic_0.cap

Actions #2

Updated by laforge 11 months ago

  • Has duplicate Bug #5977: osmo-bsc unable to bring up osmo-bts-sysmo (BSIC/TSC) added
Actions #3

Updated by laforge 11 months ago

  • Assignee changed from keith to pespin
Actions #4

Updated by fixeria 11 months ago

I submitted a WIP patch with might solve the problem, but I am not 100% sure:

https://gerrit.osmocom.org/c/osmo-bsc/+/32090 nm_channel_fsm: do not send SET CHAN ATTR before SET BTS ATTR [WIP]

keith please give it a try. Thanks!

Actions #5

Updated by pespin 11 months ago

Relevant code in osmo-bts:

static int oml_rx_set_bts_attr(struct gsm_bts *bts, struct msgb *msg)
    /* 9.4.9 BSIC */
    if (TLVP_PRES_LEN(&tp, NM_ATT_BSIC, 1))
        bts->bsic = *TLVP_VAL(&tp, NM_ATT_BSIC);

#define BTS_TSC(bts) BSIC2BCC((bts)->bsic)
        
static int oml_rx_set_chan_attr(struct gsm_bts_trx_ts *ts, struct msgb *msg)
{
    /* 9.4.60 TSC */
    if (TLVP_PRES_LEN(&tp, NM_ATT_TSC, 1)) {
        ts->tsc_oml = ts->tsc = *TLVP_VAL(&tp, NM_ATT_TSC);
        if (ts->tsc != BTS_TSC(bts) &&
            !osmo_bts_has_feature(bts->features, BTS_FEAT_MULTI_TSC)) {
            LOGPFOH(DOML, LOGL_ERROR, foh, "SET CHAN ATTR: this BTS model does not " 
                "support TSC %u != BSIC-BCC %u\n", ts->tsc, BTS_TSC(bts));
            talloc_free(tp_merged);
            return oml_fom_ack_nack(msg, NM_NACK_PARAM_RANGE);
        }
    } else {
        /* If there is no TSC specified, use the BCC */
        ts->tsc_oml = ts->tsc = BTS_TSC(bts);
    }
    LOGPFOH(DOML, LOGL_INFO, foh, "SET CHAN ATTR (TSC=%u pchan=%s",
        ts->tsc, gsm_pchan_name(ts->pchan));
    if (ts->hopping.enabled)
        LOGPC(DOML, LOGL_INFO, " hsn=%u maio=%u chan_num=%u",
              ts->hopping.hsn, ts->hopping.maio, ts->hopping.arfcn_num);
    LOGPC(DOML, LOGL_INFO, ")\n");

    /* call into BTS driver to apply new attributes to hardware */
    return bts_model_apply_oml(bts, msg, tp_merged, NM_OC_CHANNEL, ts);
Actions #6

Updated by pespin 11 months ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 50

I believe it should be fixed by this patch:
https://gerrit.osmocom.org/c/osmo-bts/+/32165 Clarify configuration of TSC on each timeslot

I first need to give a try with:
  • manual osmo-bts-trx
  • manual osmo-bts-sysmo
  • TTCN BTS_Tests
Actions #7

Updated by pespin 11 months ago

  • Status changed from In Progress to Feedback
  • % Done changed from 50 to 90

Tested this patch on top of current osmo-bts master in 201705-nightly, with BSIC=0x0a and pSetChanAttr with TSC=0x02, it works fine as expected.
TTCN3 BTS_Tests seem to be happy too.

Once merged, this ticket can be assigned to keith for confirmation and closed.

Actions #8

Updated by keith 11 months ago

It might be some days, or weeks until I get around to testing this in the high latency/VPN scenario I described.

Actions #9

Updated by pespin 11 months ago

  • Assignee changed from pespin to keith

Works for me now, assigning to keith to test it when he has some time.

Actions #10

Updated by keith 10 months ago

  • Status changed from Feedback to Resolved

Tested in my high-latency Abis scenario. It works for me know, so closing.
Thanks

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