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DSL SNR

speedychuck
Hooked
Posts: 6
Registered: 3 weeks ago

DSL SNR

Hi, My VDSL SNR is running very low (1.6dB at the moment). I believe this could be the cause of some issues I'm having. Is it possible to force the SNR up to 6dB from your end? Or is it more likely to be a fault on the line causing the issues? It's always been fairly low, around 4dB but of recent times it's dropped much lower.

 

 

Thanks.

 

 

11 REPLIES
Community Gaffer
Community Gaffer
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Re: DSL SNR

Is your line dropping connection entirely on occasion, or do the issues you're experiencing manifest themselves in some other way?
Also, what router are you using?
We can't fix the target SNR, however I may be able to help in another way.

Bob Pullen
Plusnet Product Team
If I've been helpful then please give thanks ⤵

Moderator
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Re: DSL SNR

Moderator's note:

Thread moved from Broadband to Fibre Broadband.

Forum Moderator and Customer
Courage is resistance to fear, mastery of fear, not absence of fear - Mark Twain
He who feared he would not succeed sat still

speedychuck
Hooked
Posts: 6
Registered: 3 weeks ago

Re: DSL SNR

Hi Bob,
No the connection doesn’t appear to be dropping altogether, at least, not very often as there was nothing in the last few days log to say so. I’m having momentary issues loading webpages, which I presume is being caused by error correction. Initially I thought it may be a dns issue but I changed the servers and the fault is still there.

I restarted the modem last night and it the snr has improved slightly. The issues I was having have gone again for now.

Modem/router is a cisco 887va. The account this relates to is the IP address that this message is posted from if you can see it. Output from the routers show controller vdsl 0 is below.

Thanks.


 

Just re-posting that controller output as its badly formatted above.

Firmware Source File Name 

-------- ------ ----------

VDSL embedded   VDSL_LINUX_DEV_01212008

 

Modem FW  Version: 130205_1433-4.02L.03.A2pv6C035j.d23j

Modem PHY Version: A2pv6C035j.d23j

Trellis: ON   ON

SRA:  disabled disabled

 SRA count:  0 0

Bit swap:  enabled enabled

 Bit swap count: 0 0

Line Attenuation:         0.0 dB                0.0 dB

Signal Attenuation:      0.0 dB                0.0 dB

Noise Margin:              3.8 dB                6.1 dB

Attainable Rate:       32732 kbits/s     2409 kbits/s

Actual Power:            12.2 dBm            6.1 dBm

Per Band Status:               D1     D2     D3       U0    U1    U2   U3

Line Attenuation(dB):       25.5   78.6   90.3    13.1  65.2  N/A  N/A

Signal Attenuation(dB):    25.5   78.6   N/A     13.1  63.6  N/A  N/A

Noise Margin(dB):             3.8     3.9    N/A       6.2    6.1  N/A  N/A

Total FECC: 945948113 29512

Total ES: 6878 5428

Total SES: 291 0

Total LOSS: 6 0

Total UAS: 146 146

Total LPRS: 0 0

Total LOFS: 5 0

Total LOLS: 0 0

 

 

                                                 DS Channel1   DS Channel0 US Channel1   US Channel0

Speed (kbps):                                  0                     32008                0                   2409

SRA Previous Speed:                      0                         0                    0                     0

Previous Speed:                              0                      34019               0                   2461

Reed-Solomon EC:                      5871                 2571624             0                     0

CRC Errors:                                26297                  26297             6004               6004

Header Errors:                               0                         0                      0                     0

Interleave (ms):                           0.00                    0.00                 0.00                 0.00

Actual INP:                                  2.01                   50.00                0.00                 0.00

Moderator's note by Mike (Mav): Duplicate post released from Spam Filter and removed from the thread.

speedychuck
Hooked
Posts: 6
Registered: 3 weeks ago

Re: DSL SNR

Looking at today’s logs, my connection dropped at approx 1238hrs today.
Community Gaffer
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Re: DSL SNR

I guessed you had a Hub One. As that's not the case, what I was going to try isn't really an option. Depending on the uptime, those CRC errors may be cause for concern.
Odd though. If your line is suffering, DLM should be pushing the target SNR back towards 6db (and potentially beyond) if things aren't stable Huh

Bob Pullen
Plusnet Product Team
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Plusnet Help Team
Plusnet Help Team
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Re: DSL SNR

Sorry to hear you're having issues.

 

I've tested your line and it's not showing any major issues.

 

Unfortunately as Bob's advised we can't control the target SNR on fibre.

 

I'd recommend monitoring things and if they get worse raising a fault here

If this post resolved your issue please click the 'This fixed my problem' button
 Matthew Wheeler
 Plusnet Help Team
speedychuck
Hooked
Posts: 6
Registered: 3 weeks ago

Re: DSL SNR

Thanks Bob/Matthew, I appreciate your responses.

 

FYI- Although I have a Cisco router and am familiar with Cisco IOS, I am still very much a novice/hobbyist studying for my CCNA Routing/Switching and my DSL knowledge is limited. 

 

Bob, router uptime was a few weeks. I reset the router approx 12 hours ago. I have taken another snapshot of the show controller output. If you wouldn't mind, could you look it over and see if it looks normal? Especially the CRC errors as you mentioned previously? I know that CRC Errors are not normally present on internal interfaces unless there is potential cable damage, but don't know how that would translate to a DSL line.

 

Matthew, you mentioned there aren't any major issues, does this mean you did find some minor issues? I didn't know that you can't target a specific SNR with fibre. Thanks for that info.

 

 

I'm on an Exchange Only Line unfortunately and am a fair distance from the exchange in relation to what I would be from a street cabinet unfortunately, hence the slower than desired speed for VDSL. Don't know if this would influence the errors too?

 

Again, your help is very much appreciated. 

 

 

Router output is below.

 

Thanks.

 

Modem FW  Version: 130205_1433-4.02L.03.A2pv6C035j.d23j

Modem PHY Version: A2pv6C035j.d23j

Trellis: ON   ON

SRA:  disabled disabled

 SRA count:  0 0

Bit swap:  enabled enabled

 Bit swap count: 0 0

Line Attenuation:        0.0 dB            0.0 dB

Signal Attenuation:    0.0 dB             0.0 dB

Noise Margin:            3.6 dB             6.2 dB

Attainable Rate:         30400 kbits/s 2409 kbits/s

Actual Power:            12.1 dBm          6.1 dBm

Per Band Status:              D1      D2      D3          U0    U1      U2   U3

 Line Attenuation(dB):       25.5   78.6    90.3       13.1   65.2  N/A N/A

Signal Attenuation(dB):   25.5    78.6    N/A         13.1   63.8  N/A N/A

Noise Margin(dB):           3.6       3.8    N/A           6.1     6.3   N/A N/A

Total FECC:                   14362817                         120

Total ES:                         438                                   43

Total SES:                          1                                    0

Total LOSS:                       0                                     0

Total UAS:                        35                                   35

Total LPRS:                       0                                     0

Total LOFS:                       0                                     0

Total LOLS:                       0                                     0 

 

 

                                         DS Channel1   DS Channel0       US Channel1   US Channel0

Speed (kbps):                               0              31364                      0                     2409

SRA Previous Speed:                   0                  0                          0                        0

Previous Speed:                           0                  0                          0                        

Reed-Solomon EC:                  20195          14362817                0                      120

CRC Errors:                               1030            1030                      50                      50

Header Errors:                             0                  0                           0                        0

Interleave (ms):                          0.00             0.00                     0.00                  0.00

Actual INP:                                  2.01            51.00                   0.00                  0.00

          

Training Log : Stopped

Training Log Filename : flash:vdsllog.bin

 

 

Community Veteran
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Registered: 10-06-2010

Re: DSL SNR


@speedychuck wrote:

Modem PHY Version: A2pv6C035j.d23j

This looks quite old. Perhaps upgrading the firmware might improve things.

speedychuck
Hooked
Posts: 6
Registered: 3 weeks ago

Re: DSL SNR

ejs, do you know if there is a later version which is supposed to be suited to BT lines? I read this firmware was specifically designed to work with them.

 

Cisco are not helpful or open when it comes to firmware downloads unless you have a service contract.

Plusnet Help Team
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Re: DSL SNR

I've attached the test of your line below

 

Test Outcome Pass
Test Outcome Code GTC_FTTC_SERVICE_0000
Description GEA service test completed and no fault found .
Main Fault Location OK
Sync Status In Sync
Downstream Speed 29.7 Mbps
Upstream Speed 2.4 Mbps
Appointment Required N
Fault Report Advised N
NTE Power Status PowerOn
Voice Line Test Result Pass
Bridge Tap Not Detected
Radio Frequency Ingress Not Detected
Repetitive Electrical Impulse Noise Not Detected
Cross Talk Not Detected
Estimated Line Length In Metres 1399.2
Upstream Rate Assessment Reasonable
Downstream Rate Assessment Very Good
Interference Pattern Regular Interference Observed Daily
Service Impact No Impact Observed
Interference Duration Longest Occurrence ; 00:00 to 23:45
Interference Location Customer Premise
Interference Observed In Days 14
Home Wiring Problem Not Detected
Downstream Policing Discard Rate 0.0
Customer Traffic Level Upstream and Downstream Traffic Detected
Technology VDSL
Profile Name 0.128M-40M Downstream 3dB, Retransmission High - 0.128M-10M Upstream, Error Protection Off
Time Stamp 2018-05-19T11:00:00
Parameters MIN MAX AVG
Down Stream Line Rate 30.6 Mbps 34.0 Mbps 33.5 Mbps
Up Stream Line Rate 2.4 Mbps 2.5 Mbps 2.4 Mbps
Up Time 762.0 Sec 900.0 Sec 899.7 Sec
Retrains 0.0 1.0 0.0
Current and Last 15 Minute Bin Performance
Parameters Last Traffic Count(Upto 15 mins) Current Traffic Count(Upto 15 mins)
Start Time Stamp 2018-06-01T09:30:14Z 2018-06-01T09:45:14Z
Ingress Code Violation 0 0
Egress Code Violation 0 0
Errored Seconds 0 0
Severely Errored Seconds 0 0
Unavailable Seconds 0 0

At the time of the one I did yesterday there was a few errors but nothing major

If this post resolved your issue please click the 'This fixed my problem' button
 Matthew Wheeler
 Plusnet Help Team
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Re: DSL SNR

The Cisco firmware listed in the BT list of approved FTTC modems is 39m_B_38h3_24h.

I think it uses the same DSL chipset as the Openreach HG612 FTTC modem, the last firmware for them had A2pv6C038m.d24j, so I was thinking something similar to that might help.