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[Grapefruit]

An I correct in thinking that in 99.9% of cases, if broadband is running normally the line speed (or speedtest.net result) should exceed the FTR on the line, but will be below the MSR?

[kitz]

I've never though of comparing throughput to MSR before as afaik it's supposed to be compared to sync speeds. 

However, It's not impossible for some lines to run over the MSR, although it's less likely to happen on stable lines.  It entirely depends on what happens during the training period.

The MSR is based upon the lowest sync speed during the 10 day training period rounded down to the nearest 500kbps 

So just for example you could have say a line that during the training period syncs mostly at 8mbps but has one sync at 7400, so will mean an MSR of 7000.  Speedtest results would be circa 7100. 

What about decent lines on adsl2+ which have their target snrm lowered to 3db so that will give a slightly better sync and in turn more throughput.  Iirc 3db of Snrm when I was on adsl2+ gave me about 1.1 Mbps extra.

You may well be correct in thinking most lines should be pretty near, but I'm not sure if it would be quite as high as 99.9% 

[Black Sheep]

Just to add to the debate ....... I've found that 3dB of SNR gives a gain of approx. 0.75Meg across most circuits. Plus, as Kitz states, the line would have to be really decent to handle a 3dB target profile.   

[boost]

In 99.9% of cases, those lovely terms that KBD spits at you (like LTB) have zero impact on the attitude of the attending tech who is there to run his script and leave

[c6em]

When my line was first upgraded to ADSL2+ it was on 6dB target margin
The sync speed was 11600Kbps

after a few days the DLM then changed it to 3dBb target
The sync changed to and still is around 13900Kbps.

an increase of 2.3Mbps
It has remained there on 3dB now since around 2010 when the exchange was upgraded to 21CN
Line length 2.1Km, router's attenuation figure 35dB.

[Grapefruit]

Thanks for your replies. So if I have a line with MSR of 6800 and FTR of 5400 then something is quite likely wrong if speedtest runs at 1.1, ip profile is set to 1.3 and sync speed shows as 1400? Snr is set to around 11, but it's a pretty long line.

Thanks all.

[Black Sheep]

I'd love to be able to post a come-back c6em ............. but I'd be here all month collating evidence. On average, 3dB of SNR will give you approx. a 0.75Meg gain. Adding interleaving can also improve speeds, decrease latency yes, but can actually see the synch speed increase. 

[boost]

Full stats c6 inc interleave depth? I might try and help BS explain it as I don't understand it myself so this would be a good opportunity!

I suspect the words 'coding gain' might appear somewhere tho!

[c6em]

See below:
My DS interleaving depth has been 64 since the line was initialised for ADSL so both on 20CN and 21CN equipment.
NB The 2640B incorrectly reports the channel as "fast"
DS SNR margin is basically flat during the day recording just random +/- 0.1dB variations.
FEC's run at around 4000/min

As regards the physical line it is:
2 Km E side
100m D side - all underground (its ducted from PCP) to joint box which is opposite my house
Up pole to D.P feeding 3 houses - this is a rural area.
Total length of Drop wire from pole DP to NTE5 probably 30m.


adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime  Channel: FAST, Upstream rate = 888 Kbps, Downstream rate = 13979 Kbps
Link Power State: L0
Mode:                   ADSL2+
Channel:                Fast
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):       3.2             13.5
Attn(dB):       36.0            15.1
Pwr(dBm):       0.0             12.3
Max(Kbps):      16496           888
Rate (Kbps):    13979           888
                        G.dmt framing
K:              207(0)          14
R:              16              16
S:              1               8
D:              64              8
                        ADSL2 framing
MSGc:           62              10
B:              206             13
M:              1               8
T:              2               9
R:              16              16
S:              0.4727          4.0000
L:              3774            256
D:              64              8

[boost]

Thanks

That's all a bit odd, init?

What's the DSLAM vendor reported as?
PTM or ATM mode?

Looks like some hefty interleaving too.
Does it show the INP level?

[c6em]

That's all the 2640B will report.
To me there is nothing unusual about the data - it's always been like that!
The line seems to work exactly as expected with D/S download tests just below the IP setting (this is Plusnet with their wretched IP profile which is meant to mirror BTOR's less a bit)

[I recall when I was on 20CN the line ran at the full 8128Kbps sync limit with obviously as a result lots of spare D/S SNR margin  I recall it was usually around 10dB]

I did briefly borrow a Dlink 2740B in probably 2012.
It does report additional data
Fortunately I made a note of the additional stuff (not that it means anything to me) and the extra data for the D/S was.
INP  1.1
PER 16.08
delay 7.68
OR 33.32

Sadly neither routers report the DSLAM manufacturer and I know of no one else locally who is interested in this sort of thing or prepared to look into it even if they do have a unit that 'might' report it.

Basically I'm one of the lucky one whose line just works as it should and pretty well always has. 
I have had a couple of 'single line dis' faults which makes the sync drop to very low levels. BTOR have fixed fault and the broadband simply reverts to the as before data and sync levels.
When a thunderstorm passes nearby the CRC's go mad and the line effectively stops though it remains in sync and then continues as normal afterwards.
I did have one exchange located fault in probably 2011 which caused the target to be raised to 6.  Once fault was cleared the DLM monitored the line for a couple of days I think at 6dB and then took action and just returned it back down to 3dB again and on we went as before.

Oh yes and the ping test to www.bbc.co.uk this morning gives 30ms - again as normal and as it always has been.

[kitz]

Thanks for your replies. So if I have a line with MSR of 6800 and FTR of 5400 then something is quite likely wrong if speedtest runs at 1.1, ip profile is set to 1.3 and sync speed shows as 1400? Snr is set to around 11, but it's a pretty long line.

Thanks all.

Taking the thread back on topic.

A speedtest of 1.1 against an IP profile of 1.3 sounds about right.

Yes if the FTR is 5400 and you are only syncing at 1400 with an IPprofile of 1300, then it should be construed that the line has a fault somewhere.
If your Target SNRm is set at 12dB, that will account for some loss of speed, as will interleaving.

The Fault Threshold Rate is set for a reason, its there to provide an indication of what the line is capable of running at.  With the figures you quote its quite a lot below the FTR

Can you post your line stats to see if we can spot anything obvious. 

[Grapefruit]

Taking the thread back on topic.

A speedtest of 1.1 against an IP profile of 1.3 sounds about right.

Yes if the FTR is 5400 and you are only syncing at 1400 with an IPprofile of 1300, then it should be construed that the line has a fault somewhere.
If your Target SNRm is set at 12dB, that will account for some loss of speed, as will interleaving.

The Fault Threshold Rate is set for a reason, its there to provide an indication of what the line is capable of running at.  With the figures you quote its quite a lot below the FTR

Can you post your line stats to see if we can spot anything obvious.

Thank you very much indeed for your help. Please see attached line stat results I was sent. Please let me know if there is any further information I can provide.

[Black Sheep]

If you can get 6.8Meg on a 68dB line ...... tell me your secret.  ;

The clever ones will be pouring over your stats as we speak, and hopefully have an answer soon.

[Grapefruit]

If you can get 6.8Meg on a 68dB line ...... tell me your secret.  ;

The clever ones will be pouring over your stats as we speak, and hopefully have an answer soon.

It's all numbers to me i'm afraid, I understand very little of it.