As you say SNMP doesn't make much in the way of error stats available on domestic routers.

With MRTG you don't have to use SNMP, you can have your own counters.

I wrote some scripts to examine /proc/avalanche/avsar_modem_stats every 5 minutes and return the upstream/downstream FEC and CRC errors. I then used MRTG to graph the history. I was wondering if there was any pattern in errors over time - there wasn't.

kwikbreaks - I was teasing!
Perhaps you haven't noticed by I was replying to John_ON the writer of the excellent RouterStats!

NB. RouterStats can record various bits of info not just SNR - I capture FECs and Error Seconds for example.

Fair enough but I'd no idea who wrote routerstats much less that it was the poster you responded to. I did try it with a non-netgear router with some success some time ago but as most of my troubles were down to that very router I haven't used it since changing it.

its the latter, the errored seconds dont go up with the crc errors. If I am on fast path and the crc and errored second count goes up then I get a retransmit, if the crc count goes up but errored seconds doesnt budge then there is no affect on my connection. I have also read somewhere that even without FEC there is some kind of error correction alogrithm so it maybe these crc occur but get corrected and the ones that dont get corrected are errored seconds. I usually get 5-10 errored seconds on the first few days of synch then after that pretty much 0 nearly every day.

Edited by Chrysalis (Thu 10-Jul-08 16:23:47)

I vaguely recall reading somewhere that single bit errors (over some size chunk which escapes me) are correctable on fast path. Usually a noise spike would wipe out several bits which is why interleave jumbles the datastream up converting (say) a 5 bit error into 5 single bit errors which are correctable.

HEC, CRC, and FEC counts accumulate for idle as well as data ATM cells. If you are doing general browsing, as opposed to P2P say, most of the transmitted packets will be idle ATM cells. There is no retransmission required if there are HEC or CRC errors on idle cells.

Total time = 1 days 18hours 7min 49sec
SF = 18757272 CRC = 19653
LOS = 4 LOF = 36 ES = 5158

Latest 1 day time = 18hours 7min 49sec
SF = 3839307 CRC = 1513
LOS = 0 LOF = 0 ES = 764

Previous 1 day time = 24hours 0sec
SF = 5078067 CRC = 8826
LOS = 1 LOF = 9 ES = 1266

this is latest stats from dmt today, is it possible to interpret whether my line is ok from any of this, i know basics but not enough to understand all the cec errors etc

please check what I said, it also is the same when I am downloading at full throttle. I dont think many cells will be idle then. I think what kwikbreaks said regarding single bit errors is the most likely explanation.

I am now using a billion 7402R2 on adsl2 which is currently showing 0 crc errors, not sure I believe that either. Since plugging in the billion I am getting some ping variance (no loss but varying ping latency) but tcp seems fine.

In reply to:

---

I think it depends on the router as some routers notably the speedtouch misreport errors.

---

That's not my experience:

Uptime: 28 days, 6:15:25
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 3,520
Data Transferred (Sent/Received) [MB/GB]: 703.00 / 10.48
Output Power (Up/Down) [dBm]: 11.5 / 18.0
Line Attenuation (Up/Down) [dB]: 31.5 / 55.0
SN Margin (Up/Down) [dB]: 18.0 / 8.5
Vendor ID (Local/Remote): TMMB / 
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): 17,201 / 0
FEC Errors (Up/Down): 4,148 / 5,878,531
CRC Errors (Up/Down): 2,258 / 59,541
HEC Errors (Up/Down): 1,580 / 52,508


If I force my SpeedTouch to sync at 4000+ (using the DMT tool) then the error rates do rise substantially as my SNR margin drops around 3 dB

In my stats (above), the error rates are all relatively low for a 55 dB attenuated line.

This is mine on a very similar line to CurlyWhirly on st 585v6 with filtered nte5 faceplate, firmware 6.1.4.3

Uptime: 9 days, 20:31:05
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 /4,160
Data Transferred (Sent/Received) [GB/GB]: 2.42 / 9.60
Output Power (Up/Down) [dBm]: 11.5 / 18.5
Line Attenuation (Up/Down) [dB]: 31.5 / 55.0
SN Margin (Up/Down) [dB]: 17.0 / 8.5
Vendor ID (Local/Remote): TMMB / 
Loss of Framing (Local/Remote): 4 / 0
Loss of Signal (Local/Remote): 1 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 311 / 0
FEC Errors (Up/Down): 2,400 / 502,924
CRC Errors (Up/Down): 0 / 599
HEC Errors (Up/Down): 0 / 453

Just to show what I had before I fitted the filtered faceplate

Uptime 8 days 3 hours

snr margin 9db sync rate 4160
Error Seconds (Local/Remote): 562 / 0
FEC Errors (Up/Down): 530 / 706,574
CRC Errors (Up/Down): 10 / 5195
HEC Errors (Up/Down): 4 / 4871

Edited by deleted (Sun 13-Jul-08 09:02:26)