Packet Loss + Line Speed issues with FTTC

Hey,

Wall of text incomming, and I should preface it by saying that we recently (10th Jan) got upgraded to FTTC, but there were problems with the old line before then, in that it couldn't hold sync speeds very well. The prevailing theory was that this maybe an issue with water getting into the street cabinet or something, as the issues tended to occur when the weather was bad. With the move to the new cabinet for the FTTC, it was hoped that this problem would be resolved., however it doesn't appear to have been (or possibly it was resolved and now an entirely new problem has cropped up! /positive thinking).

When the BT guy came around to install it, he did mention that there were large amounts of errors on the line when he was running his tests, but the line worked well enough when it was all plugged in, so his suggestion was just to leave it and then see what happens, and if problems occured then to contact their support (Which is the next stage now if no other options present themselves).

For the first 7 days the line was working flawlessly, a solid 27Mbps-ish. However, starting on the 17th we began to notice packet loss start to appear (there were trace amounts of packetloss before the 17th, but not this bad.

See: 12th January

17th January

Running speed tests has also turned up weird results. In the days following the install the thinkbroadband speed test was fine, but it has deteriorated massively:

SpeedTest Results

However using the bt speedtester, it shows the line as being perfectly fine, 27Mbps. and the results from other testers such as speedtester.net fluctuate wildly, but often display 14-27Mbps while thinkbroadband is showing 4mbps.

I also just tried downloading a game off Steam and was getting 1.3MB/s. Which is slower than the 2.7MB/s we could theoretically be getting, (and in fact, slower than the 14Mbps we're supposedly guaranteed) , but still much faster than the 4.4Mbps that the speedtest i ran before hand just quoted me.

ISP: Zen Internet
Modem: BT Openreach/Echoreach HG612
Router: Buffalo Airstation WZR-HP-G300NH
Operating System: Windows 7

The BT number checker thing says up to 27.5 up, 11 down, though when the guy came round to install it his tests indicated up to 36 up and 2 down.

I'm not sure how to get at the line data for my modem, as it goes through the router, so any help there would be appreciated.

Edited by deleted (Thu 19-Jan-12 10:31:53)

Not good, but where the cause is I can't think for the moment, sorry.

Re the line stats from the modem, you can't get at them without hacking it. Have a browse/search in the Fibre Broadband forum, but I wouldn't advise doing that sort of thing in this situation. You would almost certainly invalidate all sorts of warranties.

Getting FTTC does not move you to the new cabinet, so it could basically be the same problem as before, though probably all the connections for your line will have been replaced in the cabinet. See this page for an outline of the setup.

It will be easier with BT if you build a case to prove that you have problems. Run a series of speedtests every couple of hours and record the results.

The process I tend to use takes a few minutes to complete.

Ensure Task Manager is running in the Network Tab so you have a graphical indication of what is happening.

Then run each of the following tests about 10 seconds apart - just so they are spaced out. Results maybe given in kbps, Mbps or both - record both and you can convert using 1024. There will be variations - for example the BT Beta gives 39.19 Mbps (40131 kbps) but the main BT 35293 kbps with the others in between - that is reasonable.

BT Beta test - http://speedtest.btcentralplus.com/beta/
BT Beta test - a second time
BT primary tester - http://speedtest.btcentralplus.com/
TBB Java - http://www.thinkbroadband.com/speedtest.html (results will also be recorded here, as you know)
TBB Flash - http://www.thinkbroadband.com/speedtest/broadband.html
Speedtest.net - http://speedtest.net/ using the recommended server and also create an account so you have access to tests
Speedtest.net a second time with a different server but close by and in a different block.

Capture and save the Task Manager screen image - host a couple so we can see.

Repeat at intervals - keeping the same order

When you have several sets of data that prove the case - BT will normally only accept their own test but if you have other evidence, they will consider it too. Recently, I was getting 30-32Mbps from the main BT - no where near the fault threshold but with the other data they agreed there was a major issue.

Thanks for the speedy replies, I have to wait an hour or so til I can do that rotation again MHC because i just recently did the BT primary tester one, but when it's free again i'll run through them and post the results.

In the meantime maybe you guys can help me understand what is going on here:

TBB Monitor

I was just messing around testing different things to see what speeds I was getting, and I can't understand the disparity between them all. I guess the Steam servers might be busy, and capping the download at the 1.4MB/s I was getting there, but the thinkbroadband test file downloads only got up to 600kB/s, and surely they can't be capped? That would defy the point.

I have to admit though I am pretty ignorant when it comes to this kind of stuff, so no doubt there is some explaination that I just don't understand, but it baffles me that clearly the connection CAN download at 27mbps, but occasionally just throws a hissy fit and refuses to.

Edit: Should add that I'm hoping BT won't require too much in the way of evidence when we contact them now, as we've been back and forth with them for months now. The engineer who installed the FTTC also made sure to flag up the errors on the line etc when he wrote up his report, and told me to contact them if we had problems.

Edited by deleted (Thu 19-Jan-12 11:35:11)

Try the download using multiple threads option in tbbmeter.

BT Speedtest avoids ISP network/management usually.

So suggestion is that maybe ISP is limiting the speed of any single download thread. Is this BT Infinity, as had someone with similar yesterday, and the more threads the faster they went.

Have seen similar with non tbb test files on another provider that uses traffic management on a non-fttc product.

There is a discussion about the TBB test files: Here! That is possibly a different issue.

To look at this type of problem, I prefer the Task Manager graph rather than TBB meter - both are accurate but the sampling/processing on TBB seems to give the very "spiky" top whereas TM does not and is easier to use for comparisons.

As for what is going on? Something odd! And again, using a series of Speedtests should help to demonstrate the problem.


Have a look at: TM_graphs and you will see a problem set at the top and a good below - but the BT speedtest in the top has a good data rate.

The Multithreaded file is now a little small to use effectively on a 40Mb line - 2 seconds of download when perfect.

Is it worth adding a 100MB multithread?

My ISP is Zen Internet, not BT, if that is what you meant? Or is it just that the FTTC part of the line is called "BT Infinity" ?

I just tried the single thread/multiple thread 10MB downloads

Single thread capped out at ~5Mbps
Multi thread was ~10Mbps

In the options are you can increase the number of threads to five, taking it to 25MB of data.

Some dev work to cope with Giga bit will happen this year.

The spiky is probably the packet sniffing and firewall interactions.

TM uses the network card stats, you can swap tbbmeter to do the same.

That makes things more interesting.

the FTTC part is ran by Openreach and nothing to do with Infinity. Just to clear that up. The majority of people are with infinity.

Can you try something the files at http://fuller.zen.co.uk/test/

1. Download a single file
2. Download two or more at the same time

Also visit http://www.dslreports.com/tweaks and let us know the results of the tweaktester

Downloaded one of the 100MBfiles, ~270kB/s
Downloading two at the same time, they both do ~270kB/s

In reference to www.dslreports.com:

4. Notes and Recommendations
Change MTU to 1500 (FAQ #652, #695)
Choose RWIN between 281386 and 750834 (FAQ #586)
If you have GlobalMaxTcpWindowSize registry entry (do a REGEDIT Find) then change it to -1 (decimal)
Please fill in OS field <------- (I have windows 7 and that wasn't an option )
Read the tweak FAQ

Observations:
Good data stream (no/few rexmits)

Observations:
Looking good

Edit:

Did several iterations of the 5-threaded test DL from TBBmeter:

TBB Meter graph

Task Manager graph

Seems very regular to me... starts off at ~10Mbps, then tails off to ~5Mbps every time.

Edited by deleted (Thu 19-Jan-12 12:34:31)

Windows 7 the rwin should automatically adjust, but what did it say you have set new e.g.
Receive Window (RWIN): 56720
Window Scaling: off
Path MTU Discovery: ON
RFC1323 Window Scaling: OFF
RFC1323 Time Stamping: OFF
Selective Acks: ON
MSS requested: 1418
TTL:
(less any hops behind firewall)
132
TTL remaining: 117
TOS flags: none set


270KB/sec as in 2.1Mbps is pretty slow. When you said both do 270KB/sec, you mean a total of 540KB/sec at the same time.

IMPORTANT: Dont go on what Windows reports, the green part of tbbmeter is more accurate.

In reply to a post by MrSaffron:

270KB/sec as in 2.1Mbps is pretty slow. When you said both do 270KB/sec, you mean a total of 540KB/sec at the same time.

Yeah sorry I wasn't clear, both downloads were doing 270ish each, a totalling 540 at the same time.

Just ran that tweaker again:

Receive Window (RWIN): 66456
Window Scaling: 2
Path MTU Discovery: ON
RFC1323 Window Scaling: ON
RFC1323 Time Stamping: OFF
Selective Acks: ON
MSS requested: 1414
TTL:
(less any hops behind firewall)
136
TTL remaining: 119
TOS flags: none set


Also, this time I got:

Observations:
Run a line quality test
loss with large packets shown
Check tweak FAQ

Edited by deleted (Thu 19-Jan-12 12:49:55)

MTU - it recommends 1500 however BT recommend using 1492 for their Infinity service and given the infrastructure, I would have though your ISP would be recommending it to. BT Business hubs actually set the MTU to 1492.

Just finished doing that series of tests, here are the results:

TBB Meter results

This was at 8ish this morning, I'll try it again at peak time.

Sorry to bump this guys but the situation hasn't improved any since my last post. We've been in contact with Zen Internet, and they basically said "run some tests using the BT speed tester, because we can see those results". Which is annoying because the BT speed tester always shows our line as acting perfectly, so they just go "Well everythings fine then!" meanwhile i'm still downloading files at less than 2Mbps, even their own test files.

Is there anything I can say or do to get Zen Internet to take this a little bit more seriously? I hate that we're basically just getting passed off when there's clearly a problem.

Edited by deleted (Mon 30-Jan-12 05:35:03)

If BT Speedtester ok, but multiple thread downloads from ocean.zen.co.uk are bad, then suggestion is an issue in the WBC network or Zen - i.e. nothing to do with FTTC itself