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boscad
Aspiring Contributor
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Message 1 of 29

BT Infinity / VDSL2 connection speed question

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Hi folks,

 

            I won't go into all the details here, but, to save wasting you good folks time, briefly here's the situation.   Upgraded from ADSL to Infinity (FTTC) mid October.   We're 2Km line of sight from the cabinet, and, probably more like 3Km of copper.  I have one NTE on the incoming line, with NO extension wiring - my HH6 (Smart Hub) and cordless 'phone base station connect via a BT Microfilter to the socket on the NTE faceplate.   QLT is perfect.

 

            OK - ha !   I'm a hardware (largely digital, although I have a good appreciation of analogue) and software engineer.  I am always driven by curiosity, and, I created a small VB program to repeatedly interrogate the HH6 remotely.  The interrogation interval is programmable, currently, because of some "uncertainty" it has been extracting the hub stats once every 3 minutes and collecting the results in a log file.

 

            The typical speeds I have been achieving are 1.0Mbps / 2.8Mbps ( up / down )

 

            A couple of days back, the download speed crashed back to about 750K - which after that happened, I changed the interrogation period of my program from once per hour to once every 3 minutes.  

 

            Having read stories about not resetting the hub - I didn't and left it for a day - it was still stuck at the 750K.   I finally bit-the-bullet and did a hub reset, and, it came back on-line at the previous rates (1.0 / 2.8).

 

            Now - having witnessed this "disturbance" in connectivity speeds, I left my little monitoring program running, interrogating the hub every 3 minutes.

 

            Overnight, something happened - here's an extract from my log - each log entry has 2 lines - they should be understandable -

 

Report at 03:14 AM -

 

17/11/24 03:14:17 | FV: v0.09.03.07171-BT  | FU: undefined-undefined-undefined | DSS: 2.498Mbps | USS: 1.115Mbps | NU: 0d 07h 27m | SU: 0d 16h 53m |

 

17/11/24 03:14:17 | DR: 1.115 / 2.498 | MDR: 1.115 / 2.314 | NM: 6.2 / 5.9 | LA: 23.0 / 48.8 | SA: 23.0 / 35.5

 

 

Report 3 minutes later -

 

17/11/24 03:17:17 | FV: v0.09.03.07171-BT  | FU: undefined-undefined-undefined | DSS: 861Kbps | USS: 1.068Mbps | NU: 0d 00h 00m | SU: 0d 16h 56m |

 

17/11/24 03:17:17 | DR: 1.068 / 0.861 | MDR: 1.068 / 1.125 | NM: 6.8 / 7.8 | LA: 23.0 / 49.0 | SA: 23.0 / 35.7

 

Basically - all of a sudden, the DSS (downstream synch speed) has fallen again, this time to 860K.   Notice that the "Network Uptime" has reset - although the "System Uptime" is unchanged (well, it's been "up" 3 minutes longer than the previous report)

 

I went to the "wholesale" test site - and got this -

 

wt01.jpg

Having been "successful" by resetting the hub the last time this happened, I thought, let's do it again - and lo and behold - after the reset, and restarting my logger program -

 

Before hub reset -

17/11/24 06:59:17 | FV: v0.09.03.07171-BT  | FU: undefined-undefined-undefined | DSS: 861Kbps | USS: 1.068Mbps | NU: 0d 03h 43m | SU: 0d 20h 38m |

 

17/11/24 06:59:17 | DR: 1.068 / 0.861 | MDR: 1.068 / 1.571 | NM: 7.1 / 11.5 | LA: 23.0 / 49.0 | SA: 23.0 / 35.7

 

After hub reset -

*** Run started 17/11/24 07:27 - using HH6

17/11/24 07:27:17 | FV: v0.09.03.07171-BT  | FU: undefined-undefined-undefined | DSS: 2.742Mbps | USS: 1.119Mbps | NU: 0d 00h 09m | SU: 0d 00h 11m |

 

17/11/24 07:27:17 | DR: 1.119 / 2.742 | MDR: 1.119 / 2.820 | NM: 6.0 / 6.3 | LA: 23.0 / 48.8 | SA: 23.0 / 35.6

 

And the wholesale test now shows

 

wt02.jpg

  I'm just really curious about any issues around "resetting the hub" (which as I mention, I have read various things - like "No, don't do that it will have to re-train" and so on - along with other "contradictory" information - like "Reset it during a quiet time" and so on )

 

  I'm also really uncertain as to what the "Profile" concept is - my download speed profile clearly changed during whatever occurred at around 3AM this morning, and, changed again, after I "manually forced" a hub reset.

 

  I also don't get why the Upstream (which is actually super-important to me) Profile suggests 10Mbps - I would have thought (at 3Km copper) that might be a tad "optimistic" LOL.

 

   I'm open to any thoughts / advice / general clarification and so on.   I have a stack of other questions relating to NM, LA and SA - but - I'll keep that for later.

 

  Thanks in advance for your attention !

 

  Bill

 

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licquorice
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Message 2 of 29

Re: BT Infinity / VDSL2 connection speed question

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Quick answers to your questions.

 

Openreach have an automatic monitoring system (DLM) that will attempt to keep your connection stable. If it thinks the line can't support a given speed due to noise/line breaks etc it will lower your speed in an attempt to stabilise it. Re-setting the hub looks like line disconnections to DLM and can cause it to lower your speed if done too frequently.

 

The noise on your line will vary during the day and night and thus the theoretical speed (max speed) can vary. If you re-sync at a time when noise is at its lowest and max speed is at its highest, you might sync at a higher speed.

 

The IP profile of your line is the expected throughput at the IP layer rather than the sync speed and is calculated as a %age of sync.

 

For some reason the upstream IP profile is always given as 10 for Infinity1 and 20 for Infinity2 regardless of actual sync speed.

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boscad
Aspiring Contributor
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Message 3 of 29

Re: BT Infinity / VDSL2 connection speed question

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Thanks for that @licquorice - yeah - OK I get all of that - thanks for the clarfication on the "resetting too frequently" (fortunately, I don't 🙂 ).     And OK, so the "profile" is kind of like what you would/should expect after all the IP packaging overhead is removed ( hmm, or is it "added" - anyway you know what I mean...).     Haha ( on the 10 -20 upstream ! )

 

Cheers, and thanks 

 

Bill

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XRaySpeX
Recognised Expert
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Message 4 of 29

Re: BT Infinity / VDSL2 connection speed question

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It's still v. slow for fibre even at 3 km. I wouldn't have thought you'd have been sold Infinity, but what BT calls Faster BB.

 

Please post your full Router Stats. For a Home Hub see on here: Broadband Top Tips . Full router stats are key to any speed & connection issues.

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boscad
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Message 5 of 29

Re: BT Infinity / VDSL2 connection speed question

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Hi @XRaySpeX - sure - here's both the router and the dsl checker status - 

 

bbrouter.JPG

 

And the dsl checker stuff = 

 

bbdsl.JPG

 

   Thanks for your interest !

 

  Bill

 EDIT - OOPS - you might have meant the tech log - this is it - 

bbrouterlog.JPG

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XRaySpeX
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Message 6 of 29

Re: BT Infinity / VDSL2 connection speed question

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Thanks. I just wonder if you are on an Impacted line.

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boscad
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Message 7 of 29

Re: BT Infinity / VDSL2 connection speed question

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Yeah - I've seen reference to this - and that's another issue I'm not clear about ("Impacted line") - I mean I get the general sense of what it means, but wonder if - well, that's just the way it is ....  🙂

 

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XRaySpeX
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Message 8 of 29

Re: BT Infinity / VDSL2 connection speed question

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I'm not entirely clear about it either but it's to do with Bridge Taps, which is being reported as "Unknown" for your line. I believe it is just the way it is but can be fixed.

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boscad
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Message 9 of 29

Re: BT Infinity / VDSL2 connection speed question

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Well I had to google that - this was the wiki entry in summary - and - now, that's interesting....

Bridged tap or bridge tap is a long-used method of cabling for telephone lines. One cable pair (of wires) will "appear" in several different terminal locations (poles or pedestals). This allows the telephone company to use or "assign" that pair to any subscriber near those terminal locations. Once that customer disconnects, that pair becomes usable at any of the terminals. In the days of party lines, 2, 4, 6, or 8 users were commonly connected on the same pair which appeared at several different locations.

A bridge tap has no hybrid coil or other impedance matching components, just a “T” (or branch) in the cable. Thus the bridge presents an impedance mismatch. The unused branch of the T is usually left with no device connected to its end, thus has no electrical termination. Both the tap and its unterminated branch cause unwanted signal reflections, also called echoes.

Digital subscriber lines (DSL) can be affected by a bridged tap, depending on where the tap is bridged. DSL signals reflect from the discontinuities, sending the signal back through the cable pair, much like a tennis ball against a brick wall. The echoed signal is now out of phase and mixed with the original, creating, among other impairments, attenuation distortion. The modem receives both signals, gets confused and "takes errors" or cannot sync. If the bridged tap is long, the signal bounces back only in very attenuated form. Therefore, the modem will ignore the weaker signal and show no problem.

A bridge tap can also be referred to as a "multiple" or a telephone pair "in multiple".[1]

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licquorice
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Message 10 of 29

Re: BT Infinity / VDSL2 connection speed question

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A bridge tap (of which there are many practical causes) is just one of many causes of impairment to a circuit and unfortunately the longer a line is, the more susceptible it is to interference and dodgy joints etc.

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