Cellular Network Infrastructure » Radio Access Network » OsmoBTS

When we receive configuration for the T200 timeouts of the LAPDm layer from the BSC, we ignore them, see the following code snippet:

»·······/* 9.4.53 T200 */
»·······if (TLVP_PRESENT(&tp, NM_ATT_T200)) {
»·······»·······payload = TLVP_VAL(&tp, NM_ATT_T200);
»·······»·······for (i = 0; i < ARRAY_SIZE(btsb->t200_ms); i++) {
»·······»·······»·······uint32_t t200_ms = payload[i] * abis_nm_t200_ms[i];
#if 0
»·······»·······»·······btsb->t200_ms[i] = t200_ms;
»·······»·······»·······DEBUGP(DOML, "T200[%u]: OML=%u, mult=%u => %u ms\n",
»·······»·······»·······»·······i, payload[i], abis_nm_t200_mult[i],
»·······»·······»·······»·······btsb->t200_ms[i]);
#else
»·······»·······»·······/* we'd rather use the 1s/2s (long) defaults by
»·······»·······»······· * libosmocore, as we appear to have some bug(s)
»·······»·······»······· * related to handling T200 expiration in
»·······»·······»······· * libosmogsm lapd(m) code? */
»·······»·······»·······LOGP(DOML, LOGL_NOTICE, "Ignoring T200[%u] (%u ms) " 
»·······»·······»·······»·······"as sent by BSC due to suspected LAPDm bug!\n",
»·······»·······»·······»·······i, t200_ms);
#endif
»·······»·······}
»·······}

AFAIR this relates to the T200 values bein in milli-seconds, and shorter than our overall delay between the LAPDm implementation and the actual air interface (L1-L2 queue, radio modem, ...). So the counters would have to be clocked by the GSM time, not by system time?