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Intermittent latency issues

I've been working from home during COVID lockdown and audio/video calls are completely useless frequently breaking down for 10s of seconds at a time. This is so awkward that I bought a 4G router and have had to use that for work.

Running an outbound ping continually from my machine shows that the latency is pretty decent at about 15-20ms most of the time, but often spikes to 500-700ms which completely kills any ability to operate on calls. I've even noticed netflix downgrading to potato quality which means the drops can be quite sustained since there should be a buffer. Lots of post-rs errors too.

BQM: 35d45cf44b5605ec97f1e31a37b795e983f217ea

Status

Acquired Downstream Channel (Hz)
323000000
Locked
Ranged Upstream Channel (Hz)
32600000
Locked
Provisioning State
Online
 

 

Downstream bonded channels

ChannelFrequency (Hz) Power (dBmV)SNR (dB)ModulationChannel ID
13230000000.540256 qam24
21390000003.238256 qam1
31470000003.540256 qam2
41550000002.540256 qam3
5163000000340256 qam4
61710000003.240256 qam5
71790000003.240256 qam6
81870000002.940256 qam7
91950000002.240256 qam8
102030000002.440256 qam9
112110000002.240256 qam10
122190000002.240256 qam11
132270000002.240256 qam12
142350000001.740256 qam13
152430000001.540256 qam14
162510000001.240256 qam15
172590000001.240256 qam16
182670000001.240256 qam17
192750000001.240256 qam18
202830000001.240256 qam19
212910000001.240256 qam20
222990000001.240256 qam21
23307000000140256 qam22
243150000000.740256 qam23

  

ChannelLocked StatusRxMER (dB)Pre RS ErrorsPost RS Errors
1Locked40.33759164899
2Locked38.921171304709
3Locked40.958273267820
4Locked40.962492265668
5Locked40.953126275985
6Locked40.918724309508
7Locked40.318969309892
8Locked40.39395315459
9Locked40.96740320828
10Locked40.34371318253
11Locked40.33377318277
12Locked40.92966303998
13Locked40.32744303639
14Locked40.92814309715
15Locked40.32906300909
16Locked40.33399267466
17Locked40.32816292805
18Locked40.93405260705
19Locked40.32488316903
20Locked40.32789302644
21Locked40.32934300021
22Locked40.32559168054
23Locked40.92565215809
24Locked40.9207593676

 

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Re: Intermittent latency issues

Upstream

ChannelFrequency (Hz)Power (dBmV)Symbol Rate (ksps)ModulationChannel ID
1326000004.05512064 qam5
2394000004.15512064 qam4
3462000004.15512064 qam3
4537000004.2512064 qam2
ChannelChannel TypeT1 TimeoutsT2 TimeoutsT3 TimeoutsT4 Timeouts
1ATDMA0000
2ATDMA0000
3ATDMA0000
4ATDMA0000

General Confiuration

Network access
Allowed
Maximum Number of CPEs
1
Baseline Privacy
Enabled
DOCSIS Mode
Docsis30
Config file
kldJKDHSUBsgvca69834ncxv98732

Primary downstream service flow

SFID10578
Max Traffic Rate117000047
Max Traffic Burst42600
Min Traffic Rate0

Primary upstream service flow

SFID6112
Max Traffic Rate10500047
Max Traffic Burst16320
Min Traffic Rate0
Max Concatenated Burst16320
Scheduling TypeBestEffort
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Re: Intermittent latency issues

Network log

TimePriorityDescription
14/06/2020 06:15:4criticalNo Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 15:04:24noticeDHCP Renew - lease parameters tftp file-cmreg-vmdg505-rtsl10016u-b.cm modified;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 15:04:24ErrorDHCP REBIND WARNING - Field invalid in response;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 12:13:54ErrorDHCP RENEW sent - No response for IPv4;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 10:56:14criticalNo Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 09:23:27ErrorDHCP RENEW sent - No response for IPv4;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 09:07:45criticalNo Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
13/06/2020 03:42:34ErrorDHCP RENEW sent - No response for IPv4;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 17:34:34criticalNo Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 16:20:47ErrorDHCP RENEW sent - No response for IPv4;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:43Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:43criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:42Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:39Warning!Lost MDD Timeout;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:35criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:35Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 11:03:34criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 10:28:28criticalNo Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 10:28:28Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
12/06/2020 10:28:27criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
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Re: Intermittent latency issues

Hello

Post RS errors are noormally indicitive of noise on the line, in cases like this go around and make sure all coaxial connectors to all VM equipment are finger tight, also checking that there are no unterminated connections or damage/sharp bends to the cable.

Power off hub for 30 secs and back on if the post RS errors are increasing still at a vast rate then an engineer will be need to find the cause of the noise.

Regards Mike

I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more

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Re: Intermittent latency issues

12 hours later and the post-rs errors haven't increased but I have still been having issues, the BQM graph looks pretty ropey, and my outbound ping requests still sometimes jump to 500-700ms for anything from 1-60seconds at a time.

I checked connections and restarted the modem now, but assuming we don't see any more post-rs errors then there must be another cause.

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Re: Intermittent latency issues

HI Geoffrey, thanks for messaging us and we are sorry to see that you are having issues with the service. We will send you a private message to have a closer look. ^Chris. 

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Re: Intermittent latency issues

Had the visit on Saturday, and the engineer inspected and reterminated a bunch of the connectors, measured the slope of the signal (attenuation at higher frequencies) and replaced the 3db attenuator with an equalizer to reduce the slope a bit, but wasn't really of the opinion that any of this would fix the issue. It's always difficult with an intermittent issue as you can't tell if it's fixed immediately.

Things looked relatively good over the weekend but I suspect that's just lower overall traffic volumes at the weekend. Today we had a full outage while a Virgin Media van was parked further up the road so there is clearly more work ongoing. I'll leave it another few days to see if that maintenance may have changed anything.

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