Technical Discussion
  >> Technical Issues

Register (or login) on our website and you will not see this ad.

  Print Thread
Standard User Ozil_416
(newbie) Thu 05-Sep-13 02:40:00
Print Post

Constant connection drops (CRC Spikes) & Speed Drop

[link to this post]
Hello All,

I'm here to try and get more/different opinions on what could be the cause for the issues i'm having with my connection.

I guess i should start from the beginning but i'll try to keep it brief so my post isn't to long.

For around 2/3 years i was with Be* Broadband (directly) and during that time my connection was rock solid for stability with my actual speeds of 20/21Mbps (3db w/ interleaving off). I decided to migrate to a new ISP (I didn't want to) when the news broke that Sky were buying out be* and all customers would move to Sky.

I migrated to a Be* Reseller, The migration went smoothly and for the initial 7/8 days my connection was what i expected rock solid with pretty much the same sync speed there was only a slight rise in latency from 9ms to 13ms.

But now the problems starts....

My connection would drop and keep dropping, what i mean by this is that my connection would be stable for several hours (up to 23hours) then my connection would drop, re-sync then roughly 6 minutes later it would drop again, resync and again around 6 minutes later it would drop again, this would repeat for up to 2 hour (but usually only up to 1 hour) then it would go away.

*I think it's strange the time between disconnects is so consistent.

*The period of disconnects would happen 2/3 times a day some times just once a day usual between 8-11am, 8-11pm sometime between 1-2pm but rarely. (My uptime will never last more than 23hours, on 2 occasions it would have an uptime of around 23 hours and 55mins and then the disconnects would start, on 1 occasion it lasted 23 hours and 59mins and the disconnects started) which i found very strange.

*During the 7/8 days via dslstats i noticed that i would get around 150 crc's per 24hours which i felt was pretty good, but since this issue has started while the period of disconnects aren't happening i now get 1000s of crc predicted per 24 hours based on how many crc's i get every second/minute. it appears what ever is effecting my connection is always there but intermittently gets worse.

* I done all the usual tests at my end, removed faceplate and used microfilters via test socket, different modems, 17070 (2) no noise etc and nothing worked

*Engineer went to the exchange and apparently replaced a 'fuse' which appeared to resolve the issue initially but problem came back (or was never resolved), engineer came to test my wiring and found no problem suggested the issue is at the exchange and a port change should fix it and said he'd request it but it never happened, requested a port change (at this stage it was only thing left to try) with ISP at the time said it would take up to 7 working days for the port change, but wasn't keen on this as it's a long downtime and also suggested it was line degradation but due to the nature of the issue and what i had observed i wasn't convinced my line had suddenly become so bad so quickly.

After around a month on 6db with interleaving on (suggested by isp) which was just masking/covering up the issue things got worse, my connection speed dropped now i can only get 16mbps.

At this stage i decided to move to a new ISP Be* Reseller again, but the disconnections and speed drop continued

This isp (current) was able to arrange a port change at the exchange which i'm not 100% convinced happened due to no downtime which i was told would happen for up to 24 hours while the work is done but if the port change did happen then my problems were not solved.

*via dslstats it appears that i have huge spikes in crc which cause the disconnects.

*I appear to have constant small spikes in crc while the connection isn't disconnecting, for the first 7/8 days i never had these small spikes in crc so often.

*I noticed via dslstats that during two of these periods of constant disconnects my speeds actually when back up to 20/21Mbps on a resync but went back down to 16Mbps when the connection dropped again after around 6mins so it appears the issue is effecting my speed.

Before the problems started my Max and Path were around...

Max = 24000kps
Path = 23000kps

no they are (see stats below) which give me around 16000kbps actual speed.

Here my router stats

xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 8000
Max: Upstream rate = 1382 Kbps, Downstream rate = 19128 Kbps
Path: 0, Upstream rate = 1377 Kbps, Downstream rate = 18667 Kbps

Link Power State: L0
Mode: ADSL2+
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 3.1 5.9
Attn(dB): 15.5 9.2
Pwr(dBm): 18.5 12.1
ADSL2 framing
Path 0
MSGc: 62 16
B: 254 39
M: 1 1
T: 2 3
R: 0 0
S: 0.4718 0.9968
L: 4323 321
D: 1 1
Path 0
SF: 258299 251935
SFErr: 39 1
RS: 0 0
RSCorr: 0 0
RSUnCorr: 0 0

Path 0
HEC: 59 0
OCD: 0 0
LCD: 0 0
Total Cells: 182449945 13450331
Data Cells: 185714 81900
Drop Cells: 0
Bit Errors: 11687 3

ES: 624 4
SES: 187 0
UAS: 653 653
AS: 4145

Path 0
INP: 0.00 0.00
PER: 16.04 16.44
delay: 0.11 0.24
OR: 33.90 10.70

Bitswap: 473 1001

Since Link time = 1 hours 9 min 3 sec
FEC: 0 0
CRC: 39 1
ES: 38 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0

1 x Master Socket w/ 1 x extension socket
Connected to Master Socket via BT Open Reach Faceplate
HG612 in Modem only mode bridged to a RT-N66U
Home Phone is corded and only plugged in when making/expecting calls.

*I did have a noise issue while i was with Be* directly a few months before i migrated but this was shiftily fixed (I thought i'd mention this although i think it's not related)

Q: Does anyone with better experience than me see anything wrong with these stats?
Q: What would cause my crc to spike so high roughly every 6 minutes which disconnects me?
Q: Has anyone had experience or come across disconnections like this before?

Any help/suggestions is appreciated.

Edited by Ozil_416 (Thu 05-Sep-13 02:47:02)

Standard User IamQ
(experienced) Tue 17-Sep-13 19:22:35
Print Post

Re: Constant connection drops (CRC Spikes) & Speed Drop

[re: Ozil_416] [link to this post]
Can you graph your signal to noise ratio or margin?

Your line appears short at 15dB - whats your cable routing to the exchange? Underground/Overhead/PCP served etc?

It still sounds like an interference issue for bursts of disconnections at specific times of the day, the general reduction in sync may just be tough luck and the sign of an aging or interfered with line and generally no one will care much about this (Since your still getting 19mbit sync)
  Print Thread

Jump to