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Standard User Andrue
(knowledge is power) Sun 21-Apr-13 10:48:37
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The 'guess that fault' thread.


[link to this post]
 
Connection running normally:

http://www.thinkbroadband.com/ping/share/33c68fedd7d...

Fault graph:

http://www.thinkbroadband.com/ping/share/378fe4a258e...

Comments?

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Andrue Cope
Brackley, UK

Just because he could. RIP.

Edited by Andrue (Sun 21-Apr-13 10:49:32)

Standard User Chrysalis
(legend) Sun 21-Apr-13 10:54:23
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Re: The 'guess that fault' thread.


[re: Andrue] [link to this post]
 
well for a start I think you have jumped the gun to say it cant be the copper.

BT Infinity 2 Since Dec 2012
Standard User R0NSKI
(experienced) Sun 21-Apr-13 11:02:26
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Re: The 'guess that fault' thread.


[re: Andrue] [link to this post]
 
To me it just looks like there is activity on the connection, causing the spikes in latency. My connection gets a lot of yellow spikes when my cloud backup is backing up.

But IIRC your speed tests reduce greatly when the problem occurs.

Have you tried disconnecting your home network/turning off wireless when it occurs to see what affect it has on the ping graphs?

Edited by R0NSKI (Sun 21-Apr-13 11:03:58)


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Standard User Andrue
(knowledge is power) Sun 21-Apr-13 11:59:38
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Re: The 'guess that fault' thread.


[re: R0NSKI] [link to this post]
 
In reply to a post by R0NSKI:
To me it just looks like there is activity on the connection, causing the spikes in latency. My connection gets a lot of yellow spikes when my cloud backup is backing up.

But IIRC your speed tests reduce greatly when the problem occurs.
Yeah, as usual roughly 50% drop in throughput. ISP status page shows that yesterday was actually an unusually low day for usage - 210MB downloaded.

---
Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User Andrue
(knowledge is power) Sun 21-Apr-13 12:01:19
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Re: The 'guess that fault' thread.


[re: Chrysalis] [link to this post]
 
In reply to a post by Chrysalis:
well for a start I think you have jumped the gun to say it cant be the copper.
Lol. The modem isn't showing anything.

xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 2
Max: Upstream rate = 26634 Kbps, Downstream rate = 76644 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 65847 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 5.9 15.0
Attn(dB): 0.0 0.0
Pwr(dBm): 12.5 6.4
VDSL2 framing
Path 0
B: 63 237
M: 1 1
T: 64 45
R: 16 16
S: 0.0309 0.3782
L: 20698 5373
D: 1043 1
I: 80 127
N: 80 254
Counters
Path 0
OHF: 598902396 750065
OHFErr: 206 522
RS: 3320109961 1801097
RSCorr: 1268545 3759
RSUnCorr: 10342 0

Path 0
HEC: 3073 0
OCD: 0 0
LCD: 0 0
Total Cells: 1275389047 0
Data Cells: 451167261 0
Drop Cells: 0
Bit Errors: 0 0

ES: 55278 2350
SES: 48 0
UAS: 51 51
AS: 892383

Path 0
INP: 3.00 0.00
PER: 1.48 4.25
delay: 8.00 0.00
OR: 129.36 60.17

Bitswap: 116597 5829

Total time = 1 days 43 min 13 sec
FEC: 2948848 24782
CRC: 3760 2539
ES: 55278 2350
SES: 48 0
UAS: 51 51
LOS: 9 0
LOF: 10 0
Latest 15 minutes time = 13 min 13 sec
FEC: 1790 4
CRC: 0 2
ES: 0 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 2362 3
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Latest 1 day time = 43 min 13 sec
FEC: 4758 11
CRC: 0 2
ES: 0 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 110364 365
CRC: 13 65
ES: 6 60
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Since Link time = 10 days 7 hours 53 min 3 sec
FEC: 1268545 3759
CRC: 206 522
ES: 38 488
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
#

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Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User WWWombat
(fountain of knowledge) Sun 21-Apr-13 15:51:24
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Re: The 'guess that fault' thread.


[re: Andrue] [link to this post]
 
On the fault graph, the symptoms you see are some very minor yellow peaks - showing that the maximum latency gets rather higher than normal, but not in any particularly continuous way, and with no special change during the evening peak hour

For comparison, here's mine. Note the evening peak - which is down to traffic at the ISP or on the WBC backhaul, not my link at all.

Note, especially, that your blue areas *don't* change in the same way as the yellow. That means the delays are happening to individual packets, on an occasional basis, keeping the average delays low.

[Detailed maths: My estimation is that your yellow mini peaks represent about 15ms delay, and that 1 horizontal pixel represents 100 seconds. That means at least 1 ping in 100 is getting delayed by 15ms, and the average additional delay is 0.15ms. When it gets to 7 pings in 100 delayed by 15ms, the average increases to 1ms - and the blue line moves 1 pixel higher.]

So yellow peaks alone mean 1-3 packets in 100 are being delayed by 15ms. Yellow peaks with a single extra pixel in blue means around 7 packets in 100 are being delayed by 15ms.

Conclusion: Every ping packet is getting to the modem, and 95%+ are getting back in the minimum latency. Even when there are delays, it only affects 10% or so of packets, by up to 15ms.

Like R0nski, I think this suggests that something else is transferring, that causes the ping packets to be queued slightly. But the queue could be happening *anywhere* between TBB and your router (or whatever you have responding to the ping).

The one place that wouldn't queue your ping packets is the modem (your modem or the cabinet's modem), at least due to errors: Errors in the modem-modem stream cause packets to be dropped, never queued. The modem probably could queue the ping due to QoS, but that would be triggered by some other download/upload happening.

Note, especially too, that there are no red areas - there is zero packet loss. Because ping packets are never retried (by design), and you can see zero loss, you know for certain that they aren't being lost on the modem-modem link either.

No red areas also means no resync's, for any reason at all. DLM hasn't intervened to turn anything on or off, and there has been no independent loss of signal.

On that evidence, there is *nothing* wrong with the copper.

There could be something wrong with your modem, that make it *look* to be working perfectly. For example, that it is responding perfectly to pings but choosing to delay or drop your downloads, but that would be a very individual fault. Seems unlikely to me.

HOWEVER

on your "working normally" graph, you get a blip of reduced latency.

There is no packet loss, so there have been no resyncs to cause this. Either we blame this on a brief re-routing of packets within BT's 21CN WBC network, or we suspect something with your modem.

It is hard to believe that your modem has a fault that just happens to manifest itself by appearing to work perfectly on the TBB Ping graph.
Standard User Andrue
(knowledge is power) Sun 21-Apr-13 16:19:20
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Re: The 'guess that fault' thread.


[re: WWWombat] [link to this post]
 
In reply to a post by WWWombat:
It is hard to believe that your modem has a fault that just happens to manifest itself by appearing to work perfectly on the TBB Ping graph.
Nor that manifests every 60 days starting at 1500utc:

April (4pm BST)
http://www.thinkbroadband.com/ping/share/1ae25650a99...

February (3pm GMT)
http://www.thinkbroadband.com/ping/share/1b414a57412...

Just have to wait for proper Support staff on Monday to where they go next with this. If nothing much happens I may switch to AAISP. Such a repeatable must be fixable if only we can find the right BT bloke to talk to :-/

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Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User WWWombat
(fountain of knowledge) Sun 21-Apr-13 16:59:37
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Re: The 'guess that fault' thread.


[re: Andrue] [link to this post]
 
Something behind the scenes, almost certainly!
Standard User Andrue
(knowledge is power) Mon 22-Apr-13 20:09:28
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Re: The 'guess that fault' thread.


[re: WWWombat] [link to this post]
 
In reply to a post by WWWombat:
Something behind the scenes, almost certainly!
Cleared now. BT apparently claim to have cleared a 'profile mismatch' over the weekend. I didn't know until Support got in this morning and there was no sign of a change. However this evening in an attempt to further diagnose I disconnected my router and therefore got a new session. Hard to say if it's just cleared because it's due or because of what BT did.

http://www.thinkbroadband.com/ping/share/8c5c9fd6841...

Modem has been up all through this :-/

---
Andrue Cope
Brackley, UK

Just because he could. RIP.

Edited by Andrue (Mon 22-Apr-13 20:11:29)

Standard User WWWombat
(fountain of knowledge) Tue 23-Apr-13 00:15:04
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Re: The 'guess that fault' thread.


[re: Andrue] [link to this post]
 
Graph fails to load here.
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