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Author Topic: Sync speed lower after line fault repaired  (Read 2613 times)

AggroBoy

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Sync speed lower after line fault repaired
« on: October 23, 2008, 05:03:48 PM »

Hi guys,

I'm having some trouble with my adsl sync speed. It's not terrible, but it is irritating in the circumstances. First, some background. I've been in the same flat for a couple of years now, and have never had any bother with my connection before, it's been a pretty stable connection (often for 2-3 months at a time,) at 4000- 5500. There was even a three month period where it reliably connected at about 7000. During this time the noise margin fluctuated roughly between 5db and 11db, and the line attenuation was about 50db.

A couple of weeks ago (Thus 9th Oct,) I came home to find the connection had dropped, I raised a call with Enta support (I'm with UKFSN, one of Enta's V-ISPs,) and then the connection came back at a terribly low sync. Over the next week or so, I chased the fault, while the line continued to loose sync frequently, and resync at speeds between about 100 and 800kbps. Eventually BT identified and fixed a line fault, so I hoped things would be back to normal.

But it's not. It's definitely better, but it's not as good as it was. The reliability seems fine - I haven't seen a single sync-loss, but the sync speed is just over half of what it was before the fault. My router lists the downstream sync as being slightly over 3000kbps, varying by about 100kbps either way when I reconnect. The ip-profile looks like I'd expect for that sync: 2500.

I've done all the usual stuff; tried different filters (I usually use a filtered NTE5 faceplate,) plugged directly into the test socket, tried different routers, and nothing seems to make a difference. The line sounds clear (there was an audible crackle while the fault persisted,) and the stats on the router look fine: a solid 15db noise margin and the same 50db line attenuation it's always had.

My question is: does anyone know what might be going on here? Why might a line that always had a good connection before deteriorate like this? Doesn't that 15db noise margin suggest there's room for a faster sync? Is sync speed somehow adaptive and I'm just suffering for the week of terrible sync stability (I'm pretty sure it's not, but I'm grasping at straws here  ;))? Is my line just not as good as it was before the fault?

Thanks for any insight you can provide.


Will
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roseway

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Re: Sync speed lower after line fault repaired
« Reply #1 on: October 23, 2008, 06:43:28 PM »

Hi and welcome

What's almost certainly happened is that, when your line was going through its unstable period, DLM increased your target noise margin to stabilise the connection. It looks as though the target noise margin is now 15 dB, which would account for the lower speed connection.

In theory DLM should progressively lower the target noise margin in 3 dB steps if the connection is now really stable, and error counts are low. This is a very uncertain process, and if it hasn't started to happen after three weeks or so, you might ask your ISP to get BT to do it manually. BT don't really like doing this, so whether you get success depends on your ISP.
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  Eric

Hillfly

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Re: Sync speed lower after line fault repaired
« Reply #2 on: October 27, 2008, 02:00:38 PM »

Enat can ask BT to change the target margin.

They did this for me after a simialr issue and within an hour it was actioned by BT.

Enta are very good at support i have found.
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AggroBoy

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Re: Sync speed lower after line fault repaired
« Reply #3 on: October 28, 2008, 06:53:02 PM »

Thank you both so much for your input; It's really helpful. It sounds to me like the best thing to do is leave it a few more weeks (the connection still looks solid from a reliability standpoint,) and then get enta to poke BT if the speed hasn't improved.
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