Sync rate increase

Hi,

I'd like to share my recent experience with FTTC and get some advice on whether I should resync my modem, just to see what would happen if anything.

I'm on BT Infinity, D-Side is 300 meters according to the engineers JDSU and it's been stable for 8 months at 38717/10000 with 37.5/8 Mbps throughput and 15ms latency. Been very happy with it.

10/06/2011 - Early morning the internet goes down, rang the status line and it's because of "planned maintenance and upgrades" in my area due to complete by 6 AM and I may need to reboot the hub. So I went to bed and checked the speed next morning, 38717/10000 but 32.5/7.7 Mbps throughput and 29ms latency. Not good but I presume the work isn't quite complete and it'll improve as the IPProfile hasn't changed.

Strangely the hub kept sync the whole time and didn't need rebooting so I left it.

13/06/2011 - Throughput not improved and now IPProfile has dropped, for the first time ever, to 33566.

So I contact support, while trying to get some action I do a few manual resyncs by rebooting the modem with 2-3 days apart. 34933 is the max I managed to get giving 33.7 Mbps throughput.

Eventually support agreed to book an engineer, the first one didn't show, a second was booked and immediately canceled so support got back onto OR. OR said they had trouble remotely testing my cuircuit but it would be fixed soon and they would then run some tests. The next day...

30/07/2011 - It seems OR have optimised the 36 Mb sync rate rather than put it back to 40 Mb, IPProfile is the same but throughput has improved to 34.2 Mbps and latency from 19 to 11ms.

Not what I'm after but the best I can probably hope for on a 36 Mb sync rate. At this point I've exhausted the support channels and have the option of going to the ombudsman, which i decide against becasue although I want the max performance my line can support (A) It's still very fast (B) latency is the best it's ever been (C) upto 80 Mbps is hopefully around the corner when the sync rate will be reset anyway.

So I give up, enjoy a stable line and note the hub is keeping sync day after day.

Hello, hang on...

30/08/2011 - Exactly one month since OR seemingly optimised the performance of my 36 Mb sync rate and with 42 days uptime on the hub, a resync is forced at 01:53 AM. IPProfile has risen to 37616, throughput to 36.5 Mbps and latency has stayed at 11ms.

I did not expect that!

So now I'm 1 Mbps down on throughput but have better latency than before the drop. That will do nicely. Though I can't help but wonder, if that profile will rise to the max 38717 if I do a manual resync during the day. What do you recon, shall I risk it? I'm very tempted if just to see what would happen but don't want it to fall back to the 36 Mb sync rate.

It seems it is possible for the sync rate to rise without the need for an engineer visit but whether it has gone up on it's own or as a result of OR intervention I'm not sure. Seems a pretty big coincidence that it changes exactly a month after OR seemingly optimised the 36 Mb sync performance.

I'd appreciate your thoughts and advice.

Thanks,
Darren

The SYNC rate is purely dependant on the line conditions, just like with ADSL and ADSL2+, although just a lot less due to there only being a short run of copper. It's nothing to do with an engineer

So, if the copper run has issues, or is quite long, then the SYNC can still vary from time to time on FTTC.

James

Did you read the whole post James?

Maybe I'm mistaken, the way I understand it is the sync rate is locked in during install, if it drops the only way to get it increased is to get an engineer visit, they would test the line and then phone a number to get it reset.

I know the IPProfile can vary with the line conditions but I'm talking about the sync rate.

Lots of people have had it done on the BT forums, however their speed dropped a lot further than mine so they had no problem getting an engineer out to reset it.

How are you testing the latency? as ping to each different address will differ ,so 11ms to what ? it also is Dependant on several other factors too

In reply to a post by Croftie:

the way I understand it is the sync rate is locked in during install, if it drops the only way to get it increased is to get an engineer visit, they would test the line and then phone a number to get it reset.

That sounds like a wholly inefficient way of working a DSL standard (to only allow a sync increase via an engineer visit).
Does that mean when BT switch vDSL profiles (later this year, or early next year) we are all going to have to ask for engineer visits to get us synced above 40Mbps.
Sounds like a very expensive way of doing things.

No, the sync is in no way locked. FTTC operates a DLM based on the Openreach platform (not BTW), but as with any DSL produduct (of which FTTC is being VDSL) its rate adaptive, so it will SYNC as high as it can based on a target SNR. Most lines never see this because they SYNC at 40000 anyway. But we have a customer in NI who syncs around 13-17Mb depending on the day and his line conditions. So completely variable and not fixed. Thats why the IP profile system still exists, so it can adapt dynamically to the SYNC event.

In reply to a post by Anonymous:

How are you testing the latency? as ping to each different address will differ ,so 11ms to what ? it also is Dependant on several other factors too

By pinging websites at the command line. I use the bbc as a baseline which is what the figures in the OP are based on but I also ping others aswell to make sure it's not just pings to the bbc that are changeing.

In reply to a post by adebov:

That sounds like a wholly inefficient way of working a DSL standard (to only allow a sync increase via an engineer visit).
Does that mean when BT switch vDSL profiles (later this year, or early next year) we are all going to have to ask for engineer visits to get us synced above 40Mbps.
Sounds like a very expensive way of doing things.

I agree, you can see many many times on the BT forums peoples sync rate dropping and engineers being sent out who run tests then phone a number to get it reset. If there is remote management on the modem why not just run a remote test, if that is clear increase the sync rate then if there are problems that the remote tests have not picked up the DLM will just lower the sync rate again. An engineer can then be sent out to find the fault.

OR saw no faults on my line and instead of seeing that as a good thing and increasing the sync it was seen as a reason not too. Surely they have history of recent sync rates and such to go on aswell.

In reply to a post by Adsl24:

No, the sync is in no way locked. FTTC operates a DLM based on the Openreach platform (not BTW), but as with any DSL produduct (of which FTTC is being VDSL) its rate adaptive, so it will SYNC as high as it can based on a target SNR. Most lines never see this because they SYNC at 40000 anyway. But we have a customer in NI who syncs around 13-17Mb depending on the day and his line conditions. So completely variable and not fixed. Thats why the IP profile system still exists, so it can adapt dynamically to the SYNC event.

I agree it's not locked as in it is set and then never goes down, but I don't accept that it also goes up based on current line conditions, at least not for everyone. No matter how many times I resynced the IPProfile wouldn't go any higher becasue the sync rate was locked at 36 Mb. Support also told me that it wouldn't.

It seems like OR have stepped in in my case, I'm very doubtfull it would of rissen on it's own.

I'm hopeing there are no more maintenance windows anytime soon, or if there are and it causes another sync rate drop that it is below 30 Mb so I can get it raised quicker than 11 weeks.

Edited by deleted (Wed 31-Aug-11 22:51:37)

In reply to a post by Croftie:

but I don't accept that it also goes up based on current line conditions,

Would help to have clarification from an expert (i.e. someone who works for the appropriate department in OR) as it just doesn't sound right that BT have modified a perfectly good working vDSL system such that you can not go faster than your very first sync speed without calling an engineer out (which will cost OR a fortune when the have to send an engineer back to every single FTTC install when the switch profiles later this year).

Of course, BT can "cap" the line to a max sync if they deem the need to (as part of a fault etc), but under normal conditions, the sync can both fall and rise.

As has been proved in my case, it can be changed remotely, why OR are so reluctant to do so though is anyones guess. I don't think for a second every line will need a visit to switch profiles.

So not "in no way locked" as you said before. Obviously it could be locked because it had been for me and many others.

I wonder if my cab is now using the 17a profile that a few others are seeing and that is what caused the sync rate reset.

"in no way locked" by default. Only a system or engineer intervention would cause the line to be capped on a particular sync/profile. Bt default it will vary.

No, the others who have reported this would seem to be using a Fritzbox modem router which is incorrectly reporting the VDSL profile.

So definitely possible it was locked then, I'd love to know why the maintenance caused it to drop and be locked.

It could be correct though?

I just rebooted the modem and it gave no improvement. Don't know what that means though, the line can no longer support a higher IPProfile or it's been locked or something else. Really missing line stats.

It's gone pear shaped again.

Throughput has dropped to 32.8 Mbps and latency gone up to 19ms, router uptime is 6 days, 18:08:54 and IP Profile still 37585.

It's the same situation as the first time speed dropped after the maintenance, this time no maintenance just inexplicable performance loss.

Performance up untill a few hours ago.
And now.

BT speedtest back on the 4th. Strangely throughput is higher than IP Profile.
BT speedtest just now.


So looks like the sync rate has been capped again. The line has been stable, with no disconnects and steady consistent throughput.

Any ideas what the hell is going on and what should I do now?

Edit, The speed seems to have dropped at midnight, could this be my ISP imposing a cap rather than the DLM?

Edited by deleted (Fri 09-Sep-11 01:36:27)

IP Profile now is the same as on the 4th. That suggests the slowdown is ISP-related. Nothing to do with a sync speed cap.

So what to do now presuming that is the case?

Surely ISP-related loss of performance has always been with us?

Monitor when speeds are good and bad for a few days, including a couple of weekends to see if there is the pattern we are used to on ADSLx. If that pattern emerges then I'm right. If it doesn't then in this case I am crying wolf. I hope the latter!

Only the technology between us and the exchange has changed, not the fundamentals of average bandwidth provision per customer.

That I expect has increased to some extent in anticipation of demand, or might increase in response to demand, but it will certainly never go away. Unlimited bandwidth at consumer prices with no consequential drawbacks is unsustainable.

Edit - The question of the IP Profile itself having fallen is something a few people have seen, and the theory is that it is increased cross-talk caused by increased take-up. As with ADSLx, a single modem power-cycle during daylight hours would be a good idea.

Edited by RobertoS (Fri 09-Sep-11 08:47:59)

That's just it, speed is good all the time, regardless of time of day/night or day of the week. The problems started because of that maintenance period of downtime. I was litterally working online as it went down and happened to run a random speedtest about half hour before. Speed was solid 37.5/8 Mbps with full 38717 IP Profile and 15ms latency as it had been for the previous 8 months. Barely a few hours after it had come back up I checked it and the IP Profile was the same but throughput reduced to 32.5/8 Mbps and 26ms latency. The IP Profile dropped a few days later.

It's too much of a coincidence to be cross-talk, surely cross-talk issues wouldn't happen overnight either would they?

Performance is good but the speed is getting capped/uncapped/capped.

I did a daytime power down on the 2nd, did another one earlyer and the only change is the IP Profile has dropped inline with the reduced throughput. I ran the bt speedtester after the resync and it shows very low throughput which doesn't match up with the actual throughput I'm achieving on file downloads or speeedtest sites. As you can see from task manager in the second screen shot.

BT Speedtester
Task Manager - First two peaks are from speedtest sites last one bt speedtester.

It's just occured to me that it's exactly 10 days since the speed increased. Maybe coincidence maybe not.

Don't really know what I can do from here, short of haveing a bash at unlocking the stats. Think I might get in contact with BT again and see what they say about the recent developments.

As always I welcome any thoughts.
Cheers.

Apparantly there are two openreach vans parked by the cab and the FTTC one is open. I'm going to have a strole round shortly, hopefully they are still there.

When is there a need to open up the FTTC cab once it's installed?

You need to open the cab up if:

There is a fault.
You are adding additional cards (used the first 96 ports).
You are adding additional cables to connect to the old cab (usually when you add new cards as in 100 pairs)

If the cab has exceeded 96 workers you may get cross talk on the pairs towards your house. This will exist all the time the relevent modems are on, day or night. Most people will leave theirs on 24/7.

So one new customer may have caused your decrease. It is thought this is why BT estimates are below the rates people saw when first connected. Many people on here are expecting the drop to happen at some point for some people.

Thanks kitcat, appreciate that. It is the second two in this case..

I couldn't get away on friday but the engineers are there again today, and I just went and had a chat. They are installing a new card and interconnect cable. He mentioned the fiber cab takes up to 288 connections and there are currently about 90 in use.

He said if I'm not happy with the speed to contact my ISP. I mentioned cross-talk and he just looked at me blank. He confirmed the route my line takes and that it's 300M as the enginneers JDSU measured on install.

One other point of note is that the line is aluminium, not sure how much of a difference that would make though on this relatively short line.

So what do you think, cross-talk or my ISP palying around with caps?

Cheers.

anyone else notice its getting colder outside...