topic Re: FEC / CRC / HEC Errors - Are these in a normal range? in Broadband

FEC / CRC / HEC Errors - Are these in a normal range?

angiejolly — Sat, 27 Feb 2010 13:19:51 GMT

Hi
I have received a test router from PN in order to try to locate my slow ADSL speeds. Can anyone tell me it the Errors shown at the bottom of the screen shot are normal for the time the router has been connected?

Re: FEC / CRC / HEC Errors - Are these in a normal range?

W1ngD1ngs — Sat, 27 Feb 2010 14:01:40 GMT

Hi,
the FEC errors show that you have interleaving on and it is doing it's job. With that amount of attenuation you are a long way from the exchange and very lucky to get synced at 1,799Kbps!
My attenuation is 63.5dB and (after lots of work by BT & PN) I have been informed that I am on the end of approx 7Km of copper wire! I sync at 1,440Kbps.
I don't see how you are going to get a faster connection before FTTC or without moving home!

Re: FEC / CRC / HEC Errors - Are these in a normal range?

itsme — Sat, 27 Feb 2010 14:09:54 GMT

Mine are below and I'm not concerned.

Quote
Uptime: 6 days, 20:59:35
Modulation: G.992.3 annex A
Bandwidth (Up/Down) [kbps/kbps]: 959 / 3.069
Data Transferred (Sent/Received) [MB/GB]: 334,33 / 1,17
Output Power (Up/Down) [dBm]: 12,5 / 0,0
Line Attenuation (Up/Down) [dB]: 27,5 / 48,5
SN Margin (Up/Down) [dB]: 5,5 / 8,0
Vendor ID (Local/Remote): TMMB / IFTN
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 6 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 54 / 0
FEC Errors (Up/Down): 0 / 4.130.757.870
CRC Errors (Up/Down): 0 / 2.328
HEC Errors (Up/Down): 0 / 1.748

Re: FEC / CRC / HEC Errors - Are these in a normal range?

angiejolly — Sat, 27 Feb 2010 14:21:07 GMT

@ Dawnrider
If only I were connected at 1,799! I am actually connecting at around 160Kbps. The PN router seems to be showing my maximum potential connection speed. I am 4.9 Km from my exchange, BTW.
@ itsme
Thanks for your feedback. I looks as though the test router has proved that it is not my equipment that is faulty as it's performance is worse than my BT Voyager 205. The 205 was connected for 47 hours when I swapped it out for the test unit.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

W1ngD1ngs — Sat, 27 Feb 2010 14:27:20 GMT

I didn't say connected, I said synced! Have you run a BT Speed test (mainly to see what your IP Profile is) and checked your PN profile?
http://www.speedtester.bt.com/ for the BT Profile and
https://portal.plus.net/my.html?action=data_transfer_speed for the PN one.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

angiejolly — Sat, 27 Feb 2010 15:15:54 GMT

@ Dawnrider
Here are the data you requested.
Telephone number:
01909xxxxxx
Phone exchange:
WORKSOP
Estimated line speed:
1.0 - Checked on 2010-01-08 15:09:41
Current line speed:
250

Re: FEC / CRC / HEC Errors - Are these in a normal range?

W1ngD1ngs — Sat, 27 Feb 2010 15:37:25 GMT

Your BT IP Profile is set to 135Kbps, so you are never going to connect any higher than that until the BT equipment has seen that you have a stable connection syncing at 1,799 for three days when it will adjust your IP Profile upwards.
Your PN profile will follow in the next 24 hours, or if not ask PN to give it a shove.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

Apprentice — Sat, 27 Feb 2010 16:52:55 GMT

Quote from: angiejolly
Hi
I have received a test router from PN in order to try to locate my slow ADSL speeds. Can anyone tell me it the Errors shown at the bottom of the screen shot are normal for the time the router has been connected?

After looking at the stats I notice that's an ADSL2+ connection you have, some would say your line is rather long to get any advantage from that, in fact you should try (if it's possible) and connect on ADSL2 (ITU G.992.3/4,ITU G.992.3 Annex J,ITU G.992.3 Annex L) with your router as you might get a better sync rate with better stability.

Alastair

Re: FEC / CRC / HEC Errors - Are these in a normal range?

angiejolly — Sat, 27 Feb 2010 17:18:03 GMT

Thanks Alastair. I will try this what I am back up to normal speed.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

itsme — Sat, 27 Feb 2010 17:46:41 GMT

Quote from: Apprentice
[(if it's possible) and connect on ADSL2 (ITU G.992.3/4,ITU G.992.3 Annex J,ITU G.992.3 Annex L) with your router as you might get a better sync rate with better stability.

I would say it's not possible for a user to specify the annex. Annex J have no POTS so this is a major disadvantage if the user require a telephone. Annex L require the power to be increased and I would say this require manual configuration by BT.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

WWWombat — Sat, 27 Feb 2010 20:08:25 GMT

Speed analysis of the router stats over on this thread.
I wouldn't worry about the FEC/HEC/CRC values either. They're not too bad.
FEC errors are ones that have been corrected, so aren't really errors.
CRC errors are the real errors.
As ADSL runs at about 60 frames per second, and the connection has been up for 150 minutes, this represent 4100 corrections and 49 errors in 540,000 frames, or about 1% needing correction, and 0.01% needing re-transmission.

Re: FEC / CRC / HEC Errors - Are these in a normal range?

itsme — Sat, 27 Feb 2010 22:18:19 GMT

60 frames a second? What is this?

Re: FEC / CRC / HEC Errors - Are these in a normal range?

WWWombat — Sun, 28 Feb 2010 04:06:56 GMT

Quote from: itsme
60 frames a second? What is this?

A mistake Its actually 60 superframes per second.
The ADSL modem, and the exchange-side equipment, communicate back-and-forth using a frame-based structure to carry data, into which goes both the error-detection,correction and interleaving information as well as the user data. Even though the modem/exchange carries a variable amount of user-data (the "up to 8 mbit/s"), depending on how well the synchronisation went, the data is still structured into a set number of frames.
The general rate is 4000 frames per second.
These frames are then structured into a "superframe", which consists of 68 ordinary frames, then 1 synchronisation frame. This is a rate of (just under) 58 superframes per second.
The relevance to the CRC count is that the CRC check seems to be done per superframe, so if the CRC count increments, it is one superframe that has failed and needed re-transmission.
If the count is going up at a rate of 60 per second, then you have 100% failure rate.