Attainable throughput

I have FTTC, and my router (a FritzBox 7530) shows "attainable throughput" numbers (Rx and Tx) on its DSL info page. The numbers update every few seconds, so seem to be a real time calculation, I guess based on current signal strengths, S/N ratios, error rates etc. The router help says only "The maximum volume of data that can be sent on the line" and googling isn't much use either. Where are these numbers calculated, is it the router, DSLAM, or what, and is there any standard definition or formula?

No particular problem, just interested.

Isn’t this just showing max sync rate the router thinks is possible ?

Yes, probably it is, but I can't find anything that definitively says so.

It was discussed on this thread recently as if it were a fairly standard parameter. This post indicates it might he a number maintained by some modem chipsets. If it's a fairly standard thing, I'd just like to know how it's calculated and exactly what it means.

I have a 40/10 FTTC service. My router shows a max attainable download speed of 47.271Mbps so were I to pay for an 80 service I would only get another 7.271Mbps. So only interesting to me if I could get the higher speed for free.

I tend to ignore Max Attainable values as they are calculated by the modem with unknown algorithms, so can in some cases be completely wrong. One well known scenario is on interleaved lines which give can give ridiculously high attainable values. On my 80/20 FTTC line running at full sync speeds with G.Inp enabled but a low SNRM of around 1.6dB the downstream attainable can be anything in the range of 70Mbps to 90Mbps or more. So basically a meaningless random number

The max attainable rate uses a whole bunch of characteristics to calculate that figure.
For starters there are 3 possible max attainable calculations/algorythms that a modem can use.

The Fritzbox uses a Lantiq chipset which means depending on the age of the firmware installed it could be using 1 out of 2, of the 3 algorithms.

Lines connected to an ECI cabinet with INP (Interleaving enabled) on the line cause the max attainable rate to be exaggerated by around 10%, unless using a newer Lantiq firmware, in which case it will be relatively accurate.

In short, it's likely an accurate figure unless interleaving is enabled, in which case it is likely to be exaggerated (but not necessarily).

I hope that is as clear as mud.

Thanks. Not sure what type of cab I have (I could take a look, is it possible to tell from the outside?). The router thinks it's connected to a Broadcom DSLAM.

In the DSL info INP is given as "45" (Rx) and "0" (Tx). There are no units for these numbers. The router help says only the higher the number the lower the impulse noise, but since it doesn't give a possible range that's about as helpful as a chocolate teapot. G.INP is shown as "on" (Rx) and "off" (Tx). I don't understand this stuff in any detail.

I've only had the 7530 a few weeks, so I would hope its firmware is reasonably up to date. It says it is version 07.29 and alleges it is up to date.

It's a Huawei cabinet.
The INP numbers tell me G.INP/Retx is enabled on the downstream. That's the default mode on Huawei cabinets.

The max attainable figure will be fairly accurate.

Edited by j0hn83 (Mon 16-May-22 11:27:21)