SNR at night

[woodsmic]

My SNR stays at 8 all day long, then from 6pm it goes down to 6, then later on 5, 4, 3 and back again.  Only fluctucates on a night..  Is this normal?

[Sean]

Yes, it's usual for SNR to drop at the night.

[pcman2]

Hi My SNR stays 8-9db all day as well then after 8 pm drops to 3 2 .then 1db and this makes it  hard to browse why dose it drop at night?

[Sean]

I'm not sure why, mine does it.

I had an engineer yesterday fit new socket, and new port at exchange.  He left me on a 2meg profile, i was previously on 4meg.

Tech support put it up to 7, and now 6meg.  My SNR is 6 during day, but on night it falls to 0 or negative.  My router is re syncing all night.

I told them to put me back on 4meg, the whole engineer visit was a mystery to me as my line is obviously not capable and we knew this, they decided to send an engineer not me;  I was actually complaining about none line related packet loss (i.e. packet shaping distubring my internet by losing packets).

[willcocks]

its because theres more interference at night as people are at home using their electrics. theres also more traffic on the phone system


packet shaping wont give you packet loss? never heard that one before - probably another kcom mystery

[Sean]

packet shaping wont give you packet loss? never heard that one before - probably another kcom mystery

I don't know what's wrong.  During the morning weekdays, everything is fine.  Afternoon into evening, and throughout night, packet loss.

Packet Loss?  Well, I turn wireshark on, capture packets, try and watch streaming iPlayer, or download from Microsoft and there is lots of packet loss.  The speeds are slow.  My SNR is however fine on the 4meg profile.

I do a www.karoo.co.uk 100MB test download and it's fine anytime.

I ping flood from a server in Canada, and ping flooding to any router upto the LINX peering point is 0% loss.  Pingflood my IP and 15-20% packet loss.  This is not a good indication though as ping packets are permitted to be given low priority and dropped.

[chrisbyrd]

I ping flood from a server in Canada, and ping flooding to any router upto the LINX peering point is 0% loss.  Pingflood my IP and 15-20% packet loss

Whats it like on the hop directly after LINX? KCOM have 2x 1gbps capacity to LINX, which is a little lame (we have 2x 10gbps!). Their ports could be congested there, but they'll incurr penalties from LINX if they're utilisting more than 80% of their capacity so technically this shouldnt happen

[miken]

Sean, have to disconnected the ring wire? only need wires 2 and 5 connected for phone and adsl, the ring wire acts as an aerial picking up interference especially at night for reasons willcocks said.
See http://www.dslzoneuk.net/socket.php?type=html

[Sean]

Whats it like on the hop directly after LINX? KCOM have 2x 1gbps capacity to LINX, which is a little lame (we have 2x 10gbps!). Their ports could be congested there, but they'll incurr penalties from LINX if they're utilisting more than 80% of their capacity so technically this shouldnt happen

Don't know the IP of the router on the next hop, if I traceroute out of my PC they identify themselves as internal 10.x IPs, and a traceroute from the server has no replies from the routers beyond LINX so I don't know their "external" IP addresses.

Sean, have to disconnected the ring wire? only need wires 2 and 5 connected for phone and adsl, the ring wire acts as an aerial picking up interference especially at night for reasons willcocks said.
See http://www.dslzoneuk.net/socket.php?type=html

I never had to do this before, but the engineer did clip some wires, so maybe he did it.  I will check.

Prior to the engineer visit, I always had SNR reductions but down to about 6 on the 4meg profile.  Now they are down to 0, so I fear that the engineer visit has made it worse and I will now need to be on the 3meg profile - I am hardly impressed with this.  He actually asked them to set me to 2meg when he did his tests, if I hadn't of known any better I wouldn't have cared, I have family on 2 meg profiles and now I know why.   It's not the engineer's fault, I think it's a mystery to us both as to why he was sent.

Currently, during the day, SNR is about 10 or 11 consistently.  On the evening, into the night, it's anwhere from 6 to 0, pretty random each time I refresh the stats.  Tonight, back on the 4meg profile, the router has had to resync 4 times.

That said, KC emailed me today to say they have changed something on my line and to test again - NO PACKET LOSS!  I think I know what they've done, stopped any traffic shaping, because even at 9PM I can get 4mbps on a speedtest, something I have not witnessed before (it's usually 1-2mbps).

I don't understand what interference occurs at night from my end, because even with no electricals on that aren't on during the day, the SNR is still unstable.

[friendlykcengineer]

The interference that causes SNR to drop in the evenings (and during the day at weekends) is due to the fact that a higher number of people are using their DSL connection. Once your telephone line gets from your house to the green cabinet in the street, it gets packed into tight bundles of 50, 100 or even 200 pairs of cables. With so many lines in such close proximity, there is bound to be interference between ADSL users. That is why you shouldn't aim for a low SNR margin which gives you the highest possible speed during the day - if you do that you are more likely to get dropouts in the evening. Also the interference can cause data loss which would then have to be corrected by interleaving, causing a slower download speed / higher ping times. Also TCP may have to re-transmit lost packets, causing even further slow down in throughput. I think it's much better to accept a slightly lower connection speed for the sake of reliability 24/7. Of course, if you are a 'silver surfer' who only uses your line during the day, then go for it!

And don't ask why KCOM don't do something about this. All telcos are in the same boat. It's just the laws of physics and economics that dictate this state of affairs.

The ultimate answer is FTTH - no interference with fibre! How much would you be prepared to pay for say an extremely reliable 10, 100, or even 1000Mbps connections? And how much more would you pay for it to be un-shaped at peak times?

[Sean]

friendlykcengineer:

1) I understand, but a drop from 12 to -2 is rather drastic, and I wouldn't really call 12 a low target.

2) Also, before the engineer visit, the 4meg profile was stable on the night, now it isn't.  It's as stable during the day, just not the night.

3) The packet loss was NEVER on karoo.co.uk test downloads, which to me eliminates line faults, because like any other site, this comes through the line, what it does bypass is the traffic shaping.  Now KC did "something", the packet loss is almost none existent, even on a 0dB noise margin.  I think the "something" is disabling any form of traffic shaping as I can download full speed without any issues.

Unfortunately my connection is rarely used during the day, this week I have had some time off hence my ability to run some tests and let the engineer in.

This is why I am confused about the whole visit which has actually worsened it for me.  We all work full time and use the internet during the evenings or weekends, I use it mostly for watching iPlayer, 4oD etc.

This was fine up to about 3 weeks ago when iPlayer become unusable, so I started a packet sniffer and noticed the TCP packet retransmissions, plenty of them.  The SNR was just fine, router uptime was fine (no resyncs) and karoo.co.uk was fine.  BBMax Speedtest, a random USA slackware iso mirror and Microsoft all showed packet loss as well.

I reported this, making a point of saying 100mb karoo download was fine, and immediately the responses talked about stabalising SNR (which actually made no difference, it still averaged on the night at about 6-8).  I emailed a few times asking why they mentioned SNR and wanted to send an engineer as it made no logical sense it could be a line fault.

I am not prepared to pay any more than I am now!

[willcocks]

The interference that causes SNR to drop in the evenings (and during the day at weekends) is due to the fact that a higher number of people are using their DSL connection. Once your telephone line gets from your house to the green cabinet in the street, it gets packed into tight bundles of 50, 100 or even 200 pairs of cables. With so many lines in such close proximity, there is bound to be interference between ADSL users. That is why you shouldn't aim for a low SNR margin which gives you the highest possible speed during the day - if you do that you are more likely to get dropouts in the evening. Also the interference can cause data loss which would then have to be corrected by interleaving, causing a slower download speed / higher ping times. Also TCP may have to re-transmit lost packets, causing even further slow down in throughput. I think it's much better to accept a slightly lower connection speed for the sake of reliability 24/7. Of course, if you are a 'silver surfer' who only uses your line during the day, then go for it!

And don't ask why KCOM don't do something about this. All telcos are in the same boat. It's just the laws of physics and economics that dictate this state of affairs.

The ultimate answer is FTTH - no interference with fibre! How much would you be prepared to pay for say an extremely reliable 10, 100, or even 1000Mbps connections? And how much more would you pay for it to be un-shaped at peak times?

I would pay a small fortune for FTTH. 100 a month reasonable? please