Cellular Network Infrastructure » Radio Access Network » OsmoBSC

Today I saw the following trace:

<0004> abis_rsl.c:1871 BTS 0 CHAN RQD: no resources for SDCCH 0xf
<0004> abis_rsl.c:1848 BTS 0 CHAN RQD: reason: Location updating (ra=0x09, neci=0x01, chreq_reason=0x03)
<0000> chan_alloc.c:366 Failed to allocate SDCCH channel
<0004> abis_rsl.c:1871 BTS 0 CHAN RQD: no resources for SDCCH 0x9
<0004> abis_rsl.c:1721 (bts=0,trx=0,ts=1,ss=2) T3101 expired: no response to IMMEDIATE ASSIGN
<0004> abis_rsl.c:1848 BTS 1 CHAN RQD: reason: Location updating (ra=0x0d, neci=0x01, chreq_reason=0x03)

<0004> abis_rsl.c:2026 Unimplemented Abis RSL TRX message type 0x14

<0004> abis_rsl.c:1848 BTS 0 CHAN RQD: reason: Location updating (ra=0x0a, neci=0x01, chreq_reason=0x03)
<0000> chan_alloc.c:366 Failed to allocate SDCCH channel
<0004> abis_rsl.c:1871 BTS 0 CHAN RQD: no resources for SDCCH 0xa
e<0004> abis_rsl.c:1721 (bts=0,trx=0,ts=1,ss=4) T3101 expired: no response to IMMEDIATE ASSIGN
<0004> abis_rsl.c:1848 BTS 0 CHAN RQD: reason: Location updating (ra=0x09, neci=0x01, chreq_reason=0x03)
<0000> chan_alloc.c:366 Failed to allocate SDCCH channel
<0004> abis_rsl.c:1871 BTS 0 CHAN RQD: no resources for SDCCH 0x

RSL message type 0x14 is "DELETE INDication". It can be found in spec 08.58, section "5.3 Delete indication" and "8.5.4 DELETE INDICATION"

This procedure is used by BTS to indicate that due to overload on the downlink CCCH, an IMMEDIATE ASSIGN
COMMAND has been deleted.
For that purpose BTS sends a DELETE INDication message to BSC.

Handling is (not) done in abis_rsl_rx_cchan:

    case RSL_MT_DELETE_IND:
        /* CCCH overloaded, IMM_ASSIGN was dropped */
    case RSL_MT_CBCH_LOAD_IND:
        /* current load on the CBCH */
        LOGP(DRSL, LOGL_NOTICE, "Unimplemented Abis RSL TRX message " 
            "type 0x%02x\n", rslh->c.msg_type);
        break;

Not sure what should we do when we receive this message. Release the channel and schedule it for later instad of waiting for timeout T3101 (t3101_expired)?