In reply to a post by yarwell:

Unless I'm again sadly out of date in terms of information, 11mb out of 17mb would basically be a breach of the lower threshold which by ISP and Ofcom standards I believe is 30% of the rated speed for the line.

I think you're talking bout the FTR which is a 30% drop in sync speed not in throughput.

In this argument would the "rated speed for the line" be the "Attainable Rate" or "Max Rate" - the theoretical sync rate that could be attained if any line card or DSLAM restrictions were removed?

So actual sync rate should not see a drop of more than 30% from the theoretical "Attainable Rate"? And hence the 30% figure has nothing directly to do with throughput speed since that may be quoted within an acceptable range and the lower limit may be considerably less than 70% of sync speed.

Edited by 4M2 (Thu 20-Sep-12 12:44:53)

We are still in the 20th century for a bit, upgrading the exchanges to be 21CN doesn't fix the 20CN cabling infrastructure.

OK, if DLM sees a circuit as super stable, it will wind the snr down to 3db to produce it's highest sync. That the OP sees this, is an indication that the pair is in fine fettle, and not the cause of the issue.

and yes I have seen people on 3db margins having issues but then after a forced reset to 6db have a better time with their connection until the equivalent of Rambo kicks in and knocks it back down to 3db

I'm guessing you work for ISP of which many punters use a Cisco as modem/router of choice. If correct, this would explain the basis of your theory. Cisco's don't like a 3db profile. They will error, and quite often won't hold sync.
No need to worry about Rambo, get BT Wholesale to hard pin the snr to 6db.

In this argument would the "rated speed for the line" be the "Attainable Rate" or "Max Rate" - the theoretical sync rate that could be attained if any line card or DSLAM restrictions were removed?

None of the above. It would be a 30% reduction from the minimum stable line rate recorded in the initial training period.

In other words if a line originally synced at a lowest speed (MSR) of 16000 during its initial training it has to drop to a sync speed of 11200 for that in itself to be reportable as a fault.

The theoretical speeds reported by modems don't really enter into it - they are quite variable and commercial services can elect to run at SNR margins of their choosing and take the drop as experienced under their regime as the trigger for a fault.

In reply to a post by yarwell:

In this argument would the "rated speed for the line" be the "Attainable Rate" or "Max Rate" - the theoretical sync rate that could be attained if any line card or DSLAM restrictions were removed?

None of the above. It would be a 30% reduction from the minimum stable line rate recorded in the initial training period.

In other words if a line originally synced at a lowest speed (MSR) of 16000 during its initial training it has to drop to a sync speed of 11200 for that in itself to be reportable as a fault.

Yes I was aware of that with ADSL MAX connections - guess it applies to 21CN WBC also...

So in the context of this thread MSR would perhaps be the "rated speed for the line" and if that speed was to drop by 30% or more then a fault could be reported?

Therefore an ISP should be aware of the MSR and if consistently slow throughput speeds are reported by an average user then an investigation should be conducted into the current sync speed and whether it has dropped by 30% or more from the MSR.

If an ISP's support personnel imply that throughput should not be less than 30% of the "rated speed for the line" aka MSR then perhaps they are misinforming the customer...

If an ISP's support personnel imply that throughput should not be less than 30% of the "rated speed for the line" aka MSR then perhaps they are misinforming the customer...

They would be making a rod for their own back, yes.

The reliance on speed test data to indicate line condition depresses me.