topic Re: just a quick question - What is/are HEC errors? in Broadband

just a quick question - What is/are HEC errors?

rogadodge — Thu, 21 Oct 2010 20:56:49 GMT

Got a test router. looks good to my untrained eye, excet the HEC errors. Can someone explain what they are please? Thanks.
Uptime: 0 days, 0:31:24
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 444 / 1,151
Data Transferred (Sent/Received) [kB/MB]: 0.00 / 15.35
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 25.0 / 43.0
SN Margin (Up/Down) [dB]: 14.5 / 27.5
Vendor ID (Local/Remote): TMMB / TSTC
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): 0 / 0
FEC Errors (Up/Down): 0 / 2
CRC Errors (Up/Down): 0 / 0
HEC Errors (Up/Down): 97,778 / 0

Re: just a quick question - What is/are HEC errors?

VileReynard — Thu, 21 Oct 2010 21:30:58 GMT

Since no data was sent, 97,000 errors is not believable.
ADSL sends data as 53 byte ATM cells, each cell contains a CRC code which can detect errors (and correct a maximum of one error) in the header part of the cell.
So HEC=Header Error Control
Excessive errors can be corrected by Forward Error Correction (FEC).

Re: just a quick question - What is/are HEC errors?

rogadodge — Thu, 21 Oct 2010 21:37:46 GMT

Ok. think the HEC must cummulative on the line and not reset. However after over an hour the stats are pretty much the same.. Somehow don't think I want to give this router back.....
Uptime: 0 days, 1:15:53
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 444 / 1,151
Data Transferred (Sent/Received) [kB/MB]: 0.00 / 21.48
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 25.0 / 43.0
SN Margin (Up/Down) [dB]: 14.5 / 27.5
Vendor ID (Local/Remote): TMMB / TSTC
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): 0 / 0
FEC Errors (Up/Down): 0 / 2
CRC Errors (Up/Down): 0 / 0
HEC Errors (Up/Down): 97,778 / 0

Though i know i ought to....

Re: just a quick question - What is/are HEC errors?

Wheel_nut — Thu, 21 Oct 2010 22:22:04 GMT

Have you tried re-booting the Router by switching it off (using the Power Switch next to the Power Plug on the Router) and on againafter 10 seconds.
Your Sync Speed is incredibly LOW because your SNR Margin is incredibly HIGH at 27.5db.
This is dynamically set by the DSLAM at the Exchange to obtain a stable connection but I believe that the upper limit set is 15db. On a good line to the exchange. the SNR Margin shold be 6db.
Your 43db attenuation suggests that you are about 4Km from the exchange and I haven't spotted any other parameter that is seriously mismatched.

Re: just a quick question - What is/are HEC errors?

rogadodge — Thu, 21 Oct 2010 22:29:41 GMT

try that now.
done it and the results are pretty much the same.
Link Information

Uptime: 0 days, 0:01:40
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 444 / 1,151
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 25.0 / 43.0
SN Margin (Up/Down) [dB]: 14.5 / 28.0
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 13 / 0
Loss of Signal (Local/Remote): 1 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 1 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 0
HEC Errors (Up/Down): 97,787 / 0

Re: just a quick question - What is/are HEC errors?

pnf — Thu, 21 Oct 2010 23:00:12 GMT

Is your router a Thomson Speedtouch by any chance? On ADSL2+ (G.992.5 annex A) these routers seem to report a large number of upstream FEC, CRC and HEC errors at the time that the router is powered on but these errors do not seem to increase whilst the router is in use; the number of errors reported increases each time the router is restarted or rebooted and seems to be cumulative as you say. I believe this is a feature of some Thomson routers and is nothing to worry about. Mine is the same, but it works perfectly well.

Re: just a quick question - What is/are HEC errors?

carrot63 — Fri, 22 Oct 2010 01:44:08 GMT

Quote from: rogadodge
try that now.
done it and the results are pretty much the same.
....
Bandwidth (Up/Down) [kbps/kbps]: 444 / 1,151

The results are exactly the same. That looks very much like the DLM has you on one of the dreaded banded profiles that limit your sync to an upper/lower level. I was stuck on one of these when I was first on 21cn and couldn't figure out for the life of me why the downstream always synced at 2848; in my experience the router never syncs at exactly the same speed twice. This would obviously consequently push up the SNR figure beyond the target SNR set by the exchange if the banding was sufficiently low. The DLM seemed very reluctant to remove the banding in my case, taking 6 months to do so. There have been quite a few threads on this in the forum, and there's a list of the bands at:
http://community.plus.net/library/broadband/dynamic-line-management-dlm-on-adsl2/
Perhaps the DLM has seen the errors and decided to apply some of it's usual irrational OTT logic to a non-problem? I've recently been sent a Thomson 585v7 by PN, and have noticed that, as @pnf says, it seems to generate a glut of errors on startup (not always however) with no more appearing after connection.
I was sent this router because CSC apparently see "a lot of upstream errors" (as you appear to have here) with Netgear DG834xx routers, although from the stats I've seen from the Thomson, I can't see any difference at all, except for the predilection for that initial burst of errors.
@A Fox is Evil,
Although you wouldn't expect much data transfer less than 2 mins after the router has rebooted, I have noticed that my Thomson is very slow to cough up the data stats - they don't appear till quite some time after the others.

Re: just a quick question - What is/are HEC errors?

rogadodge — Fri, 22 Oct 2010 08:20:50 GMT

Thanks all for replies. Is a Thomson 585v7 , and my line speed was dropped to 250 initially,because of line faults.Has been increased to 750. And these are the results from a test router. Waiting and hoping this resolves issues and my line speed can be increased.