Kitz Forum
Broadband Related => Broadband Technology => Topic started by: tiffy on July 03, 2020, 11:40:59 AM
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Noted on the 3 VDSL lines I monitor, same exchange, different Huawei cabinets, they all had a DLM re-synch this morning within 15 mins of each other at around 02:00 hrs.
The DSLAM FW revision has not changed, in all cases there has been an increase in DS & US synch speeds with associated decrease in SNRM's, my line had the most significant change with a US synch speed increase from approx 5 to 7 Mbps. (40/10 package)
Certainly not complaining, with no change in DSLAM FW noted just wondering if there is any other significance associated with the DLM action ?
Edit: Typo correction.
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There might have been changes to the head-end OLT, from which the fibre links to the cabinets originate, and thus a re-start of all associated DSLAMs was deemed prudent.
I'm sure that other scenarios, which would fit with your observations, are also possible . . .
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Yes, makes sense, there has to be two ends to every comm's link !
I know re-connections to end user modems can be a bit of a lottery after a DSLAM outage depending on which user synch's first and so limits the cross talk factor, however as all 3 lines on different cabinets showed US synch speed improvements thought there might be some common factor ?
My line has certainly synch'ed at the fastest US speed I have ever seen which I would suspect will be very likely to return to "normal" on the next re-synch.
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in all cases there has been an increase in DS & US synch speeds with associated decrease in SNRM's,
So what are the SNRm values now?
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SNRM values before & after DLM re-synch's:
My line, PN 40/10 service:
DS, 3.3 to 2.8 dB
US, 6.2 to 2.9 dB
Son's line, BT 80/20 service:
DS, 3.2 to 2.5 dB
US, 5.5 to 4.8 dB
Daughters line, PN 40/10 service:
DS, 8.3 to 8.3 db (no change)
US, 5.6 to 4.8 dB
My line is the longest of the 3 and showed the biggest impact, ie., increase of close to 2 Mbps US synch speed.
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This is confusing to get such low SNRm for US also it is common to see the "before cross-talkers sync." effect on DS and SNRm would be around 1.xdb so yeah the line will resync. in no time but the DS SNRm is not bad really and the lines can keep in sync, the US part is the puzzling with such drop on your line in specific do not know if this can cause a resync. unless there is a 3db SNRm profile for upload that is applied to your line :hmm:
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None of the SNRM targets in the examples above were changed, just the current SNRM is lower than the target.
This is because the whole DSLAM rebooted and some lines came back on before crosstalkers.