[Cerowrt-devel] Correctly calculating overheads on unknown connections

Alan Goodman notifications at yescomputersolutions.com
Mon Sep 22 19:02:57 EDT 2014

On 22/09/14 20:52, Sebastian Moeller wrote:
>> >This test was ran on a BT Infinity VDSL/FTTC connection with the modem plugged directly into a CentOS 6 machine which is doing PPPoE.  The connection is synced at 80mbit down and 20mbit up.  BT restrict downstream speed to 77.44Mbps IP traffic.
> 	Thank you very much this is the first data set on a VDSL line I have seen, and clearly me hypothesis that overhead detection on PTM carriers will not work with the current code is nicely demonstrated. I need to ponder this a bit more and I might not be able to find a nice solution for those links...

You're welcome.  If you need any more data feel free to drop me a line.

>>>I can run the test on a slower BT connection over the week end if anyone is interested in the results?
>  I would love to see that especially if the other connection is much slower, as I see two possible issues with this data set:

The other connection is actually ADSL2, we probably know what the 
results there will be...  I think I shall run the test on a really slow 
ADSL connection later in the year to double check my overheads though. 
It seems like a very useful tool.

Also thanks for providing some example plots of how it should look. 
That will allow me to better interpret results in future.

> 1) Speed: It might be that your line is fast enough to hide the ATM quantization below another quantization (like the 4KHz symbol rate of the individual carriers) or two many concurrent carriers;)

Would it be useful if I limited my upload speed with say hfsc to 1mbit 
and re-ran the test?

Given the above comments in Sebastian’s very useful emails how would it 
be best to shape these FTTC connections at present?  Without overhead 
set or something else?


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