CRC and HEC Errors on new ADSL2+ connection

[#1]

Hi,
Connection went live last night.  Sync speed and throughput all seem good and in line with expectations. Connection appears to be working well based on a few hours use last night..  Sync about 8.9 MB/s and IP Profile 7.15.  So far so good.The thing that looks strange is the number of CRC and HEC errors reported in the Modem control panel.  This is a brand new Plusnet supplied Thomson 585 v8.
These stats are as the cummulative totals look as of now.  I don't believe the router has resynched since connecting at 5.30pm yesterday for the first time.
Are these worrying?  Will they cause any problems?  Can it be resolved or fixed?
Thanks
Andrew
Link Information
   

Uptime: 0 days, 14:51:07

DSL Type: G.992.5 annex A

Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,128 / 9,404

Bandwidth (Up/Down) [kbps/kbps]: 443 / 8,952

Data Transferred (Sent/Received) [MB/MB]: 52.64 / 536.75

Output Power (Up/Down) [dBm]: 12.5 / 20.5

Line Attenuation (Up/Down) [dB]: 14.5 / 27.5

SN Margin (Up/Down) [dB]: 27.0 / 7.0

Vendor ID (Local/Remote): TMMB / IFTN

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 0 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 10 / 0

FEC Errors (Up/Down): 0 / 0

CRC Errors (Up/Down): 0 / 495,372

HEC Errors (Up/Down): 0 / 124,188

[#2]

Nothing unusual there. ADSL2+ uses higher frequencies than ADSL1 to get the additional sync rate which can pick up more noise and thus more errors - it is stretching the technology to the limits
If the connection remains stable and does not disconnect then the router is doing what it should to detect and correct such errors. It will mean a slight reduction in data throughput due to retransmits but the higher speed probably compensates for the reduction so the overall speed will be better than ADSL1.
If you do see frequent disconnects then you could try forcing the connection to use ADSL2 (not 2+) which may improve things. This does involve telneting into the router to change the auto detection to a fixed ADSL type, it can't be done via the web interface.

[#3]

Oh, OK thanks Peter.
Throughput seems good.  Streaming internet radio and TV at present and BT W Speed tests indicate data throughput at or above IP profile.  I.e. IP Profile 7.15 MB/s data throughput 7.33 MB/s! A bit strange that it is higher!
Previously the line here (a different CLI though) was on a BT DSL Max service, which had higher upload speeds but at best, on speed checkers, download throughput was around 5 MB/s.  so ADSL2+ appears significantly better even if the errors impact a bit.
The CRC and HEC errors are continuing to rise with use and there are now a few error seconds creeping in.  I haven't noticed any impact on using the connection though so I suppose leave it as you suggest and only raise a problem if disconnections become a problem?
There seems to be a lot of config missing from router web control. Are there any good instructions for Telneting the 585, I haven't done that before?
Latest cumulative total stats @ 9.45AM:
Link Information

Uptime: 0 days, 16:13:40

DSL Type: G.992.5 annex A

Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,116 / 9,368

Bandwidth (Up/Down) [kbps/kbps]: 443 / 8,952

Data Transferred (Sent/Received) [MB/GB]: 76.20 / 0.98

Output Power (Up/Down) [dBm]: 12.5 / 20.5

Line Attenuation (Up/Down) [dB]: 14.5 / 27.5

SN Margin (Up/Down) [dB]: 26.5 / 7.0

Vendor ID (Local/Remote): TMMB / IFTN

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 0 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 18 / 0

FEC Errors (Up/Down): 0 / 0

CRC Errors (Up/Down): 0 / 601,199

HEC Errors (Up/Down): 0 / 143,855

[#4]

Can't answer the speed difference, maybe some compression is being used somewhere.
You can get faster upload speeds on 21CN (ADSL2+) and it's FREE. Just raise a ticket and ask for the upload cap to be removed and you will probably get 800k+. There may be a downside to this though as it could result in more instability on the line and a slight reduction in DS speeds (US pinches a few frequencies from DS to get the higher throughput), but it's worth a try and if you hit problems just ask for it to be capped again.
The 585's telnet interface is a bit of a nightmare for configuring things so best to stick with a few well known commands like the following to change the ADSL type. Just use DOS command mode in XP (or see the link below for Vista/W7) to telnet to the routers IP address and use the password you normally login to the router with.
See http://community.plus.net/library/hardware/forcing-adsl-modulation-on-thomson-585v7/
ADSL1 only
xdsl debug multimode config=g992.1_annex_a
ADSL2 only
xdsl debug multimode config=g992.3_annex_a
ADSL2+ only
xdsl debug multimode config=g992.5_annex_a
auto ADSL selection
xdsl debug multimode config=t1.413issue2+g992.1_annex_a+g992.3_annex_a+g992.3_annex_m+g992.5_annex_a+g992.5_annex_m
To save setting and cause a reboot type
saveall
then type
exit

[#5]

Excellent, thanks for the advice Peter.
On the upload speed, that sounds like a great idea.   I wouldn't mind comprimising download a little, for a significant improvement in upload speed.  Somewhere nearer to 1MB/s would be nice!
I didn't know you could ask for upload speed changes!  Out of interest, why do they apply an articificial cap?  Reading your response, the answer is probably there - to maximise downstream bandwidth and stability?
I am still in day 1 of the 10 day training period so thinking it may be best to wait for that to complete before altering service spec on the line.
Thanks again,
Andrew

[#6]

Quote from: Peter

You can get faster upload speeds on 21CN (ADSL2+) and it's FREE. Just raise a ticket and ask for the upload cap to be removed and you will probably get 800k+. There may be a downside to this though as it could result in more instability on the line and a slight reduction in DS speeds (US pinches a few frequencies from DS to get the higher throughput), but it's worth a try and if you hit problems just ask for it to be capped again.

The frequency range for annex A is fixed for both upstream and downstream and no frequencies from the allocated downstream is used to increase the upstream speed.

[#7]

HI AndrewD,
No difference in the training period, I can uncap it if you like. Just let me know when you raise a ticket and I'll do it?
Jojo

[#8]

Hi Jojo,
Thanks very much for the offer, call me a sceptic but I think I'll just wait for the end of my 10 day training period before requesting the upload speed restriction.
Re the router error reporting.  I'm not sure I trust the stats.  Following a retrain to a slightly higher speed (I'm only on day 2 of the 10 day training) see the below stats:  Instead fo the CRC and HEC errors which were prevalent before, now in this session the FEC errors seem majorly significant.
How could the same connection on such similar sync sppeds and noise margins produce such different error stats on the same day,  Again, it doesn't seem to affect the line functionality and throughput still seems really good.
Link Information
   

Uptime: 0 days, 2:33:43

DSL Type: G.992.5 annex A

Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,164 / 10,196

Bandwidth (Up/Down) [kbps/kbps]: 444 / 9,144

Data Transferred (Sent/Received) [MB/MB]: 16.10 / 779.70

Output Power (Up/Down) [dBm]: 12.5 / 20.0

Line Attenuation (Up/Down) [dB]: 14.5 / 27.5

SN Margin (Up/Down) [dB]: 28.0 / 6.0

Vendor ID (Local/Remote): TMMB / IFTN

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 3 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 65,537 / 0

FEC Errors (Up/Down): 49,888 / 12,745,781

CRC Errors (Up/Down): 1,279 / 105

HEC Errors (Up/Down): 0 / NA

[#9]

I am sorry to advise but you have a problem.
Disregarding the downstream corrected errors (FEC) which horrible on there own there is no way you should be seeing the number of upstream errors with a noise margin of 28dB
Can you try the test socket behind the removable lower part of the master socket

[#10]

I can't test in that way.  My main socket is a twin BT socket as the place used to have two active BT lines.
Up to Monday last week BT Broadband was on the line without any obvious problems.  The errors counts do worry me but don't appear to be affeecting performance very much.
Why would sessions vary so much with the different error counts?  HEC/CRC vs FEC?
I have nothing else on the line other than a cordless phone and a brand new ADSL2+ filter supplied with the router.
Rgds
Andrew 

[#11]

Still getting ridiculous error stats. Really wondering if the error reporting in the router is misleading. Is it possible it is wrong? The line throughput, speed tests and Internet use are all good despite errors.