FEC Errors

Im trying to find out why my dsl is so slow and have been looking at my side as my isp have gone quet.
I was moved to LLU a while ago and connect at 13meg but get ~5-6mb down which is what I was getting for adsl1. I used to be able to download at full speed but it's slowly getting worse.
Im assuming my isp have decided to apply throtteling or are over subscribed.

The only thing that looks like it could affect it is the FEC errors. In 4 hours I have 70726 corrected and 4032
uncorrected.

Would this affect the thoughput?

Down Up
SNR (dB): 5.9 8.6
Attn(dB): 32.0 17.0
Pwr(dBm): 19.0 12.1
Max(Kbps): 16652 1208
Rate (Kbps): 14585 1021

Error Sec.: 261 / 133
FEC (Uncorrected): 4032
FEC (Corrected): 70726
FEC (RS Counter): 130364654

The corrected errors don't count (apart from indicating how often received packets need to be auto corrected).

The uncorrected errors may have caused a glitch, but I doubt you'd notice over the course of 4 hours.

How do you know downloads are slow?

I relise 4 hours isnt enough to really go on but we had a powercut last night
I know as I can download the same thing (from the same place) from my adsl and from a vm line and get completly diffrent speeds. With my speeds being 1/2 that of the vm line.

I've also done speed tests that show that even though sometimes it will peek at 9mb most of the time I get 5-6mb thoughput.

dan

Perhaps you are being rate limited. Just because you are on LLU it doesn't mean you're on an up to 24 Mbps service (e.g. I'm on O2 LLU but only pay for up to 8Mbps).

My current 2 thoughts are that althought im supposed to be on a upto 24mb sevice they havnt moved me (they cant tell me why I was moved to llu) or that im being heaverly throttled.

I want to ensure I've covered everything this end first.

Thanks

Might be worth posing the question in your ISP's forum as to what happens when people are moved to LLU.

In reply to a post by dreaddan:

Rate (Kbps): 14585 1021

Shows you have been moved to an "up to" 20/24 Meg service and you are getting a good speed from it.

Your low throughput is for other reasons. I understand that when ISPs throttle you they reduce your Sync; they haven't here.

You can analyse your errors here if you have an "adslctl" router which you seem to have: http://adsl.tin2tin.net/ . You should run your router for some time to get meaningful results.

ISPs thottle you on there routers/servers by queing your packets not by limiting your sync speec (usually afaik).
I have used tin2tins checker but it just says i have errors, and doent really say what the cause or effect is, which is why I wanted to know what the effect of them are.

Cheers

Ah, OK!

Yes, the tin2tins checker does not tell you cause of errors, but does show the significance of them and you can keep your eye on them and see how they vary over time.

I understand that when ISPs throttle you they reduce your Sync;

Wrong.

Would this affect the thoughput?

yep,
for every uncorrected error a timeout and retransmission occurs,
1000/hr will certainly be more than noticeable.
time to check filters etc.

I believe it unlikely that the OP would notice that level of errors. There are 4000 frames per second so in the course of 4 hours 57,600,000 would have been received. Unless the OP was downloading continuously the bulk of those frames will be idle frames. 4032 out of 57,600,000 is an error rate of 0.007%.

eta: mixed up my frames, error reporting is over superframes (68 ADSL frames) of which there are 58.8 per second so 847,059 in four hours giving an error rate of 4032 out of 847,059 or 0.48%.

Edited by deleted (Wed 15-Jun-11 21:21:01)

It does however give suggestions on how to improve

cheers it looks like a throttling issue as I got a speed test of 9mb this evening!