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Standard User XRaySpeX
(eat-sleep-adslguide) Tue 18-Apr-17 23:50:17
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Fast Path FEC Correction


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Please somebody remind me. Is it correct that you don't get Forward Error Correction (FEC) on a Fast Path connection? It just doesn't do the checks. It may be called other terms but that's what EE routers call it.

I've a user who has millions of FEC Corrections on a Fast Path line in a few hours & I've been telling him his line must be noisy & he needs to track down the source of these errors. Now I suddenly realise he shouldn't be getting any FEC Corrections at all on Fast Path, only on Interleaved. Is that right?

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
Standard User RobertoS
(elder) Wed 19-Apr-17 00:34:36
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Re: Fast Path FEC Correction


[re: XRaySpeX] [link to this post]
 
In principal you are right. However some combo modem/routers on ADSLx report Fast Path incorrectly in their output when it appears in words early in telnet reports, with no distinguishing between downstream and upstream. Inspection of the D: line often shows a high downstream depth (Interleaving), with 1 (Fast Path) showing for upstream.

Do you have that detail available?

I haven't seen the same effect on FTTC, but don't recall any telnet outputs with the worded line on that.

Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
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Standard User XRaySpeX
(eat-sleep-adslguide) Wed 19-Apr-17 01:04:29
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Re: Fast Path FEC Correction


[re: RobertoS] [link to this post]
 
Thanks, Bob, for confirming.

This is VDSL with an EE Brightbox. (This is not a Netgear wink.) It has no Telnet but I'm quite sure it never mixes up its Interleaving for Fast Path (as observed by me on ADSL2+).

I'm also sure that I've never had any FEC Corrections whilst on Fast Path, which I've been on from almost the beginning of EE WBC. Can't check just at the mo' cuz I've just rebooted it for a diff investigation & of course Fast Path FEC Corrections show 0. If I ever had any they must have been not noticeable smile.

FYI: This is the user's stats:
STATUS
Configured Current
Line Status -- UP
Link Type -- Fast Path
Operation Mode Automatic G.993.2 (VDSL2)
DATA RATE INFORMATION
Upstream 14325 (Kbps)
Downstream 34998 (Kbps)
DEFECT/FAILURE INDICATION
Operation Data Upstream Downstream
Noise Margin 6.1 (dB) 10.9 (dB)
Line Attenuation 0.0 (dB) 19.5 (dB)

Indicator Name Near End Indicator Far End Indicator
Output Power 6.8 (dBm) 6.8 (dBm)
Fast Path FEC Correction 3482951 206
Interleaved Path FEC Correction -- --
Fast Path CRC Error 0 0
Interleaved Path CRC Error -- --
Loss Of Signal Defect 0 0
Fast Path HEC Error STR 0 0
Interleaved Path HEC Error -- --
Error Seconds 0 34

System Uptime is: 05:54:43
Any thoughts? User has always shown high no. of FECs, so I've been blaming that for his reduction in sync from 55 Meg to 35 Meg whilst the DLM compensates.

Also wouldn't the ES be much higher when the FECs are so high? Case for a faulty router?

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC

Edited by XRaySpeX (Wed 19-Apr-17 01:15:08)


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Standard User Ignitionnet
(knowledge is power) Wed 19-Apr-17 11:07:04
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Re: Fast Path FEC Correction


[re: XRaySpeX] [link to this post]
 
FEC doesn't have to involve delay and where FEC corrects blocks they don't increment the errored seconds counter.
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