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FEC/CRC/HEC

krodgers
Grafter
Posts: 85
Registered: 11-09-2007

FEC/CRC/HEC

I use a d-Link DSL-504, several years old now (2001, in fact).
Recently (just over a week ago) I started the MaxDSL saga.

Things were not too good at first.
- downloads were still limited to <2000kbps
- then that jumped to >4100kbps (external speedtester)
- and my max stable rate went up to 6500kbps at the same time
- but I got a lot of "fade outs" (very slow, had to
power-cycle the router. Down to 63kbps once!)
- also, a lot of disconnects.

- now that has changed, and things seem much better.

HOWEVER, something is puzzling me.

Here is the "line condtion" page from the router:-
----------------------
Line Condition

Data Path Interleave
Operation Mode G.DMT

Rate
Downstream 5760
Upstream 448

Near end
FEC 49004
CRC 515
HEC 476

Far end
FEC 4
CRC 7
HEC 7
----------------
It's that "near-end FEC 49004" that's worrying me.

I've kept an eye on it all day, and it increases steadily at a rate of about 3500 per MINUTE (even when I'm not accessing the 'net), and "rolls over" at just over 65000 to start again (I assume it's a 16-bit unsigned counter going round).

All other figures are after 24 hours running.

Please guys, what DOES this mean?

Ken Rodgers
5 REPLIES
N/A

FEC/CRC/HEC

FEC = Forward Error Corrections
CRC = Cyclic Redundency Check
HEC = Header Error Checksum

These are error corrections.

It just means the router is infact doing its job and actually those numbers are very low, dont worry about it atall.

Infact I've seen FEC errors in the high millions before at about 30000 a second with no problems atall.

Here's some numbers for ya Cheesy

Tue 28 Nov 2006 23:27:31 Rx-Noise= 5 Rx-Sync= 4576 DL FEC Errors= 38471440
krodgers
Grafter
Posts: 85
Registered: 11-09-2007

FEC/CRC/HEC

That's reassuring, and thanks:-)
I was just a bit worried that if my router only goes up to 65,535 (and then starts again) maybe the designers weren't expecting my error rates!
I reckon I'm getting about 5 million a day from what I see.

One more question if I may though - what is it correcting or finding errors with if I'm not doing anything?

Kind regards
Ken Rodgers
N/A

FEC/CRC/HEC

Because when you are synced with the DSLAM you are still transmitting and receiving information/communicating and these communications are just as affected by the noise on the line as data is.
krodgers
Grafter
Posts: 85
Registered: 11-09-2007

FEC/CRC/HEC

Ah - thank you, thank you!
Finally (finally finally, I promise!) that has nothing to do with my "download allowance" etc from Plusnet? It is just what we might call "the overhead between me and the exchange?"

If the answer to that is "yes", you've put my mind completely at rest, and please accept my sincere thanks:-)

Ken Rodgers
N/A

FEC/CRC/HEC

Nothing atall.

And you are very welcome! Smiley