Some advice please

[old Bill]

I know iam not a IDnet customer any more but I hope someone will be able to explain something to me. When I changed over to Sky I was put on their default NM of 7 and my sync speed was approx 6300kbps. About 10 days ago my nm went up to 10 over night and when I rebooted my 2700 in the morning my nm dropped to 8 but my sync speed went up to 7616kbps. I lost connection with Sky a short while ago and when I rebooted the 2700 it came up with this.


DSL Line (Wire Pair):   Line 1 (inner pair)
Protocol:   G.DMT Annex A
Downstream Rate:   8064 kbps
Upstream Rate:   768 kbps
Channel:   Interleaved
Current Noise Margin:   8.0 dB (Downstream), 13.0 dB (Upstream)
Current Attenuation:   42.3 dB (Downstream), 27.0 dB (Upstream)
Current Output Power:   19.3 dBm (Downstream), 9.4 dBm (Upstream)
DSLAM Vendor Information:   Country: {0xFF} Vendor: {GSPN} Specific: {0x800}
PVC Info:   0/38

Can anyone explain to me why my nm has gone up and also my sync speed ? I thought that if you nm went up your sync speed dropped.
Very happy with the speed it just seems very strange.

[Sebby]

I'm not exactly sure how Sky's LLU works in terms of target SNRMs and the like. But, it doesn't look like there's been a change in the target SNRM (if there is one on LLU, that is). It simply looks to be a case of varying levels of noise, just like on BT's IPStream.

[Inactive]

You may have more luck here OB.


http://www.skyuser.co.uk/forum/sky-broadband-help-support/

[plugwash]

I thought that if you nm went up your sync speed dropped.

That depends on why the noise margin changed.

For a given ammount of noise a higher noise margin means lower speed but more resiliance to drops.

On a rate adaptive system the head end equipment chooses the speed at sycn time to make your noise margin equal to your target noise margin (BT change the target noise margin when they detect instability. I dont' know what sky do but it doesn't look like your target noise margin has changed to me). Until that session drops your speed will stay the same but your noise margin will vary as the noise on the line varies.

So when you first synced your line was relatively noisy and so you synced at a low speed. Each time you have resynced your line has been less noisy (either through luck or maybe through actual improvements) and so you have synced at a higher speed with approximately (I don't belive the difference between 7 and 8 is significant) the same noise margin.