Kitz Forum
Broadband Related => ADSL Issues => Topic started by: konrado5 on August 10, 2013, 01:27:40 PM
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I have ADSL2+ Internet. My router is TP-Link TD-W8950ND. I'd like to check CRC and FEC errors but my router shows only HEC, OCD, LCD, super frame errors. I see CRC errors on ATM tab: AAL5 VCC statitstics but I think these errors are not the ADSL CRC errors shown on other routers. Where could I check CRC and FEC errors?
My router screenshots:
http://img89.imageshack.us/img89/92/rv4m.png
http://img823.imageshack.us/img823/3029/z62a.png
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It appears to be a Broadcom-based router, so
FEC = RS Correctable Errors
CRC = Superframe Errors
Your connection isn't interleaved, so you won't see any FEC errors.
If you want to monitor the connection, I think DSLstats should work with this model if you select the TD-W8960N from the router list.
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My router haven't Telnet.
What is norm for CRC and HEC errors/12 hours?
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Apparently you can enable telnet: http://portforward.com/english/routers/port_forwarding/TP-Link/TD-W8950ND/TELNET.htm
There's no norm for CRC and HEC errors. The levels depend on numerous factors. Possibly a more useful indicator is the ES (Errored Seconds) figure. Roughly how many ES do you get in an hour?
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I have roughly 50-100 ES on 12 hours per 5.0-6.0 snr margin, 250 per 4.4 Db snr margin.
For upstream: about 20 ES on 12 hours but above 100 HEC errors. Sometimes on one second appear 100 HEC errors for upstream.
I can forward port for telnet but I can't enable telnet of the router.
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I can forward port for telnet but I can't enable telnet of the router.
Port forwarding the telnet port (23) makes the router's telnet server accessible. You should be able to telnet into the router then.
Your levels of ES are quite unremarkable. By comparison, I currently average about 11 ES per hour down and 4 ES per hour up. Occasional short bursts of HECs are also not unusual.
If you can get a monitoring program working to plot the SNR margin it will enable us to see if there's anything which needs attention on your connection. If you can't enable telnet, I understand that Routerstats-Lite works with your router.
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Port forwarding the telnet port (23) makes the router's telnet server accessible. You should be able to telnet into the router then.
Port forwarding makes the my computer's telnet port accessible from Internet.
Your levels of ES are quite unremarkable. By comparison, I currently average about 11 ES per hour down and 4 ES per hour up. Occasional short bursts of HECs are also not unusual.
What is ideal level of ES on snr margin 6 dB? What is ideal level of ES on snr margin 4 dB?
If you can get a monitoring program working to plot the SNR margin it will enable us to see if there's anything which needs attention on your connection. If you can't enable telnet, I understand that Routerstats-Lite works with your router.
Routerstats-lite works but I use mainly Linux.
I've haven synchronization's break during synchronization. What was it? The problem have disappeared when I have disconnected phone cable connecting master phone socket with second phone socket.
Jul 11 10:40:36 user crit kernel: ADSL G.994 training
Jul 11 10:40:44 user crit kernel: ADSL G.992 started
Jul 11 10:40:48 user crit kernel: ADSL G.992 channel analysis
Jul 11 10:40:54 user crit kernel: ADSL G.992 message exchange
Jul 11 10:40:55 user crit kernel: ADSL link down
Jul 11 10:40:56 user crit kernel: ADSL G.994 training
Jul 11 10:41:04 user crit kernel: ADSL G.992 started
Jul 11 10:41:08 user crit kernel: ADSL G.992 channel analysis
Jul 11 10:41:14 user crit kernel: ADSL G.992 message exchange
Jul 11 10:41:14 user crit kernel: ADSL link up, interleaved, us=1237, ds=17844
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Port forwarding makes the my computer's telnet port accessible from Internet.
I'm not familiar with your particular router, but you should be able to restrict the port forwarding to the LAN only.
What is ideal level of ES on snr margin 6 dB? What is ideal level of ES on snr margin 4 dB?
That's impossible to answer. There's no ideal level. The lower it is, the better. But if you consider that there are 3600 seconds in an hour, and (say) 20 ES in an hour, then that's only about 0.55 % of the seconds having errors, which is fairly insignificant.
Routerstats-lite works but I use mainly Linux.
Routerstats-lite works very well in Linux with Wine.
I'm afraid I can't interpret your log, but it appears that the connection was dropped and quickly restored.
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As Roseway has said, there is no target for ES per se. An Error Second is just a second's duration in which at least one unrecoverable (generally CRC) bit error has occurred. There are various definitions of a S(erious)ES, such as 10 or more consecutive ES, but Asbokid has also suggested a rate of 320 CRCs/s.
If you know the rate of ES, e.g. 1 ES on average every 36s, then you ought to be able to calculate (theoretically) how may bits have been transmitted at your sync rate in that time. This might give you a lower bound on the BER. If you also have no SES, then 320 * that figure might give you an upper bound on the BER.
I believe that a BER of 1*10^-8/s is the sort of target error rate used by DLM (i.e. less than that figure is good, more than that bad).
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My ISP doesn't use DLM.
roseway: how do you know that super frame errors=CRC errors? I can't find this information in Google.
Screenshots from my router:
http://img89.imageshack.us/img89/92/rv4m.png
http://img40.imageshack.us/img40/5896/asmu.png
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It's still a typical target error rate, whether or not your ISP uses DLM, and is therefore a more relevant measure of the error rate than ES values. But feel free to make up your own.
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I edited post.
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roseway: how do you know that super frame errors=CRC errors? I can't find this information in Google.
By inspecting the stats reported by numerous Broadcom-based routers. All of them report SFErr (superframe errors) and some also report CRCs. In the ones that also report CRCs, the value is always the same as the SFErr value.
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ADSL BER Test - Result
The ADSL BER test completed successfully.
Test Time (sec): 360
Total Transferred Bits: 0x000000015B641800
Total Error Bits: 0x0000000000000000
Error Ratio: 0.00e+00
ADSL BER Test - Result
The ADSL BER test completed successfully.
Test Time (sec): 360
Total Transferred Bits: 0x000000015B641800
Total Error Bits: 0x0000000000000000
Error Ratio: 0.00e+00
ADSL BER Test - Result
The ADSL BER test completed successfully.
Test Time (sec): 360
Total Transferred Bits: 0x000000015B641800
Total Error Bits: 0x0000000000000000
Error Ratio: 0.00e+00
ADSL BER Test - Result
The ADSL BER test completed successfully.
Test Time (sec): 360
Total Transferred Bits: 0x000000015B641800
Total Error Bits: 0x0000000000000089
Error Ratio: 2.35e-08
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Are HEC and bit errors for upload downloded from DSLAM? I've seen that number of HEC and bit errors for upload doesn't erase after router's reboot.
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Are HEC and bit errors for upload downloded from DSLAM? I've seen that number of HEC and bit errors for upload doesn't erase after router's reboot.
This is a weird one, and something that Ive never seem to have been able to get to the bottom of. To this day I dont think anyone knows for sure one way or other.
Going back about 5 yrs I was trying to find a way to reset these errors. (Theres a few threads on here about it).
On the ST585v6 it used to save the upload error figures and somewhere retained in memory. There is/was no way to do a reset. For a while it was assumed to be a firmware issue... and later it was assumed that these figures were being stored on the DSLAM as there were a couple of broadcom based routers that were reproducing these figures. Then it was seen to be a profile related issue that could be reproduced.. ie a change of line profile via the router could reset them, but go back to the old profile and they would be back again.
However a complete change of router would often reset these figures to 0 ???
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Edit to add link (http://forum.kitz.co.uk/index.php/topic,2103.0.html) to one of the threads on this topic
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I've had much bit and HEC errors for upload on the first run of the TP-Link TD-W8950ND. My router showed 0 errors when my ISP rebooted DSLAM port.
However a complete change of router would often reset these figures to 0
Perhaps some routers doesn't show bit errors from time of run DSLAM.
I have another problem. There is changing snr margin of the upload. At the one synchronization I've 5.0-5.5 dB snr margin and output power 12.4 dB and at that moment I've resynchronizate and I've much higher snr margin 6.6-6.8 dB and lower output power 5.9 dB. Is it problem with snr margin measure for upload? My router and DSLAM don't know what are conditions on line? It's strange that the results of snr margin measue depend on concrete synchronization and not only of speed and time.
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>> Perhaps some routers doesn't show bit errors from time of run DSLAM.
Not all show 'bit errors', but they will usually show HEC/CRC/FEC type errors.
>>> There is changing snr margin of the upload
Sorry not quite sure if I understand what you are getting at here?
However, if you mean changing at sync time... Thats not unusual as you are capable of reaching the max 1.2Mbps on adsl2+.
When the line rate reaches the maximum DSLAM configured speed then adjustments can be made to the power output. This is done on purpose to avoid crosstalk affecting longer lines. If your power output is reduced, then naturally it will affect your SNRm. This is called Power Cutback and its a deliberate feature of adsl.
So in your case if you are able to sync at the maximum configured speed at a default target SNRm of 6dB or above, then the MSAN will apply power cutback (hence you see 5.9 dBm for power). Dont worry though.. because if line conditions get bad, then it should easily be able to up the juice again.
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I have snr margin 5.3 dB per 1261 kbps and power output 12.4 dBm. I'm restarting router and I have higher snr margin 6.8 dB per 1277 kbps and power output 11.9 dBm. I wonder what is cause of these differences of snr margin measure. I think that lower power output cause lower snr margin. Can't devices correctly measue snr margin? Is it possible to increase snr margin by new synchronization?
I can reset HEC error statistics for upload but I can't reset bit errors for upload. However if I reboot the router it shows many HEC errors for upload to the time while I reset these statistics.
My router doesn't show any bit errors for downlad unless I do ADSL BER test.
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I didn't get reply
http://forum.kitz.co.uk/index.php/topic,12783.15.html
Possibly because Ive not been here all day & had other things to do... I havent even had chance yet to sort out my own line fault.
Please be aware that every one here volunteers their time, theres a good bunch of people on here who will always answer if they can.
PMing me 3 times every time you dont get a response wont get you a quicker reply
Now excuse me.. Im going to get some food as Ive not eaten all day.
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I did see your post this morning. I just didnt have time to type a reply before I had to go out, because I knew it wasnt a 2 minute reply. :/
>>> I wonder what is cause of these differences of snr margin measure.
SNRm fluctuations are normal, I've passed the links a few times before for SNR, SNR Margin & Target SNR. If you have a read here (http://www.kitz.co.uk/adsl/linestats.htm#SNR) it may help you to understand what is going on.
>>> I think that lower power output cause lower snr margin.
As mentioned above, power output will have an effect on your SNRm & Increasing the power output will increase SNR figures, so yes you are correct in that lower output power will cause lower SNR. However bear in mind that SNRm fluctuates normally without changes in power. The Power cut back is there to prevent SNRm getting to high and your signal getting too strong and drowning out neighbouring signals.
There are certain power cut back profiles, however no-one knows what the power cut back parameters actually are. They are an adsl standard that has to be there, but are industry standard masks and profiles which may vary from country to country and line length.
>>> Can't devices correctly measue snr margin?
Devices do a pretty good job at measuring the Signal to Noise RAtio (http://www.kitz.co.uk/adsl/linestats.htm#SNR), so yes the SNR Margin should be fairly accurate.
>>> Is it possible to increase snr margin by new synchronization?
Yes and No
On the face of it, it may appear to change as your router reports it.. but the reality is, that because its linked to your REAL SNR which definitely isnt affected by new syncs, all youve done is adjust other parameters so that the SNRm gets as near as possible to the Target SNR.
Resync is one of the times when you may see a change in power output though, as this is one of the times when a check is made to ensure your signal isnt too strong.
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Sorry, English is not my first language and you didn't understand me. I have situation:
upload 1257 kbps snr margin 5.3 dB power output 12.4 dB and I disconnect. 20 seconds later: upload 1277 kbps snr margin 6.8 dB power ouput 11.9 dB therefore higher snr margin despire raised synchronization and lowered power output. I think that DSLAM can't correctly measure snr margin. Snr margin for upload is stable but new synchronization=new snr margin measurements. I'm afraid that sometimes DSLAM gives too much output power because snr margin for upload is bad measured (lower than in reality).