Fluctuating Sync

[Sp00n]

Not really a problem, more just a query really.

Why is it that some days I will sync @ 3200kbps and other days, like today, I can sync @ 5000kbps

My line stats are pretty ugly, but i don't really understand how it can decide that one day it will sync 2mbps higher than others, its not just the sync speed either, the throughput changes along with it so today I can download at 480+

My stats today:

DSL Status: UP
DSL Modulation Mode: G.992.5 (ADSL2+)
DSL Path Mode: INTERLEAVED
Downstream Rate: 5014 Kbps
Upstream Rate: 875 Kbps
Downstream Margin: 6 db
Upstream Margin: 6 db
Downstream Line Attenuation: 49
Upstream Line Attenuation: 57
Downstream Transmit Power: 22
Upstream Transmit Power: 12
LOS Errors: 0

 

[nheather]

The margins are quite low - this is typical of an ISP that is trying to get you on as high a bandwidth as possible.

What they do is set an SNR target and your line syncs to acheive that. If you use a target of say 9dB you will get lower speeds but more stability and reliability.

A low SNR gives the line the chance to try and connect at really good speeds when line conditions are good.

The trouble is that line conditions vary with the weather and time of day. A common thing is where telephone lines run close to streetlighting cables. At night the lights come on and the SNR in the telephone cable takes a hit due to the EMR.

Weather can also have an effect especially if water is getting round the cables.

So as these conditions change your line can sync at different rates. The fact that your ISP is using a low SNR target means that the line is more likely to experience problems and re-sync.

Cheers,

Nigel

 

[Sp00n]

Many thanks for that I didnt know they would run telephone lines near street light power!

My stats today:

DSL Status: UP
DSL Modulation Mode: G.992.5 (ADSL2+)
DSL Path Mode: INTERLEAVED
Downstream Rate: 3184 Kbps
Upstream Rate: 1071 Kbps
Downstream Margin: 9 db
Upstream Margin: 5 db
Downstream Line Attenuation: 50
Upstream Line Attenuation: 57
Downstream Transmit Power: 21
Upstream Transmit Power: 12
LOS Errors: 0