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[Alex Atkin UK]

It can be misleading though, as those packets will have a timeout so sometimes what appears to be packet loss is just packet delays, which wont necessarily have a massive negative impact.

Also depends on your router as in some cases that might drop a packet that actually arrived.  As such, ping monitors are meant to be a guideline only.

In AAISPs own words "Please note that both latency and packet loss are perfectly normal results of transferring data on your line. ".

You know, I'm actually quite impressed with Vodafone 4G now its settled down to normal:

[Edinburgh_lad]

The two bit-loading versus sub-carrier index plots look reasonable, to me. Obviously they have been created by a Fritz!Box device and the rather compressed format makes them difficult to (mentally) compare with other circuits' plots.

As an example, I have attached the bit-loading plot for my circuit. Note that it is provisioned using the Openreach 40/10 Mbps product and that I have a synchronisation speed which is, essentially, hitting the upper limit of the provisioned product.

Thanks for clarification. Would you clarify for me please: with the spectrum, does the graph not need to be filled right up to 17 to show that the line uses VDSL2? For example, in the attached screenshot, the spectrum goes up to 11,040 kHz - does this suggest that the line is more VDSL (say profile 8?), rather than VDSL2?

Apologies if these are stupid questions, but I don't have much knowledge of the VDSL technology, hence the questions on this forum where you all have more expertise.

Thank you.

[g3uiss]

The tones you see are what your line is capable of not what the VDSl2 profile is. Not all lines can manage the whole set of tones

[Edinburgh_lad]

The tones you see are what your line is capable of not what the VDSl2 profile is. Not all lines can manage the whole set of tones

Thanks very much. Is there a relationship between the tones that the line is capable of and performance? In other words, what are the advantages of having the whole set of tones, or disadvantages of having fewer?

Thank you.

[burakkucat]

As above.^ 

And a brief note to say that every VDSL2 circuit currently deployed in the UK is Profile 17a. (I.e. 4096 sub-carriers, numbered from 0 to 4095.)

It was way back in 2011 (when the VDSL2 product was first available), that Profile 8a was used.

[Edinburgh_lad]

As above.^ 

And a brief note to say that every VDSL2 circuit currently deployed in the UK is Profile 17a. (I.e. 4096 sub-carriers, numbered from 0 to 4095.)

It was way back in 2011 (when the VDSL2 product was first available), that Profile 8a was used.

Cheers. Is there a relationship between the tones that the line is capable of and performance?

[j0hn]

Cheers. Is there a relationship between the tones that the line is capable of and performance?

Yes.
There's are 4096 tones. Each tone can carry a maximum of 15 bits. Each bit is worth 4kbps. So each tone used is worth up to 60kbps (4kbps x 15 bits).

https://kitz.co.uk/adsl/adsl_technology.htm#vdsl_tones

[burakkucat]

Every tone (sub-carrier) can be loaded with up to a maximum of 15 bits. Due to prevailing, ambient, conditions along with power spectral density (PSD) (and other) masks, certain sub-carriers will have less than that full loading.

Hence the performance of the circuit is directly proportional to the number of sub-carriers that carry anything from 1 to 15 bits.

As examples, I attach the bit loading v sub-carrier index plot created for my own VDSL2 circuit (dated Jan 1st, 2022) and the equivalent plot created for a short length, test, VDSL2 circuit that I set up in "The Cattery" (dated Apr 24th, 2021).

The real circuit (Jan 1st, 2022) showed --

> xdslctl info --state
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 18373 Kbps, Downstream rate = 44123 Kbps
Bearer: 0, Upstream rate = 10000 Kbps, Downstream rate = 40000 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps

Whilst the test circuit (Apr 24th, 2021) showed --

> xdslctl info --state
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 48545 Kbps, Downstream rate = 139380 Kbps
Bearer: 0, Upstream rate = 48545 Kbps, Downstream rate = 97762 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps

[Edinburgh_lad]

Every tone (sub-carrier) can be loaded with up to a maximum of 15 bits. Due to prevailing, ambient, conditions along with power spectral density (PSD) (and other) masks, certain sub-carriers will have less than that full loading.

Hence the performance of the circuit is directly proportional to the number of sub-carriers that carry anything from 1 to 15 bits.

As examples, I attach the bit loading v sub-carrier index plot created for my own VDSL2 circuit (dated Jan 1st, 2022) and the equivalent plot created for a short length, test, VDSL2 circuit that I set up in "The Cattery" (dated Apr 24th, 2021).

The real circuit (Jan 1st, 2022) showed --

Whilst the test circuit (Apr 24th, 2021) showed --

Cheers, Burakkucat

I think I'm getting this: the higher the number of sub-carriers (those are the numbers 0-4000 along the bottom in your graph), the proportionally better performance of the circuit. Is that correct? But in what sense? In terms of speed, performance (fewer errors), volume of information being sent? Or something else? This would probably answer my question and explain why my sub-carriers end on 2560, rather than 4000 like yours., even though I'm only 545m away from the cabinet

Also, what does the 'bits' along the y axis refer to? Is it about how much information can be 'packed' in?

Thank you in advance.

[Alex Atkin UK]

Cheers, Burakkucat

I think I'm getting this: the higher the number of sub-carriers (those are the numbers 0-4000 along the bottom in your graph), the proportionally better performance of the circuit. Is that correct? But in what sense? In terms of speed, performance (fewer errors), volume of information being sent? Or something else? This would probably answer my question and explain why my sub-carriers end on 2560, rather than 4000 like yours., even though I'm only 545m away from the cabinet

Also, what does the 'bits' along the y axis refer to? Is it about how much information can be 'packed' in?

Thank you in advance.

Essentially yes its about speed, plus if you have more bits available than you need for your profile, then bitloading can shift things around if there is interference on a specific tone without your connection dropping.

The Y axis is as they said, its how many bits can be used in that tone (X axis).

[Weaver]

> Also, what does the ‘bits’ along the the y axis refer to? Is it about how much information can be 'packed' in?

The number of bits or y axis is indeed the amount of information that can be packed in on that tone/frequency, just as you said. More possibilities of subtlety per tone means a larger number count and that count needs more bits to represent it. In oversimplified musical terms, a note could be either one of ppp pp p mp mf f ff fff (loudness) that’s 8 levels so 3 bits needed to count the possible loudness values. Due to mathematical cleverness, the number of bits carried will be actually double that, so 6 bits in that case. If the line is louder and free of noise then it might be possible to get more loudness levels in and still have them distinguisheable by the receiver.

Each tone carries 4000 bits per second times the per-tone bit loading (number of bits that tone can carry due to having n distinguisheable described above). Every 1/4000 secs a fixed load of bits gets transmitted, the sum of all the per-tone bitloadings. (G.Fast is slightly different.) So more tones means more data transmitted/received hence more speed.

[Edinburgh_lad]

As of yesterday, my Thinkbroadband monitor reports packets being dropped. On my Fritzbox, min. effective data rate dropped to just 336 kbit/s.

Any comments, anyone? Thank you.

[j0hn]

If you aren't actually experiencing any actual packet loss then just ignore it.
It's very common that fritz boxes detect the BQM as a flood and drop the packets.