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[Weaver]

With enormous respect to kitz et al, I can't see that it's an MTU problem. MTU tuning is only worth a few percent, and massive fragmentation or dropping of fragments or entire packets is normally interpreted by users as unreliability.

I would suggest that if the user were using Vista that this could easily be an instance of the window-scaling-support bug in a router.

The fact that the user has tested with several machines, even with a different o/s (a Mac was mentioned) seems to make the MTU thing impossible, and presumably the vista window scaling issue is ruled out too unless Mac OSX is also a victim (which I would have thought it should be [?] as recent *nix releases are similarly advanced are they not?).

I would have thought that the continuous throughput thing is a sign of a virus (run Windows Live Safety Scanner to check) or an app self-updating (such as a virus scanner downloading definition updates) or a BT or BBC-sponsored virus such as BBC "iplayer" or "BT Vision" or some such nonsense. And again, it would go away if you switched to an other machine. But if there are any other strange BT-supplied boxes, such as IP phones, BT Vision boxes then these need to be disconnected.

Since you have changed ISPs to no avail, I can't believe that routers or other boxes are at fault since you have changed router. And since you've used several PCs that rules out just about everything else software related.

BT's ISP division offer a service where they will send an engineer out who will look at routers and PCs and improve performance, advertised on the bt.com website. But surely kitz is right and this is a screw up in the exchange or in BT Wholesale's throttling policy somehow.

As far as I can see, apart from retesting just to be on the safe side with a known good PC, and possibly swapping out routers for a proper non-gimmicky non-insecure BT silly one :-) as a sanity check its now the time to throw the problem at BT.

[begin unsolicited rant :-) ] Or better yet, switch to an ISP that does not impose silly usage policies or ship farcically insecure kit to you and can be trusted not to thieve your personal data and monetize your browsing habits in secret only to get caught  red handed. There are plenty of good ones out there. [end of wholly unsolicited rant that slipt out there.] :-)

But seriously BT should be able to offer really good engineering support with their new initiative. Dig around on BT website.

[jeffbb]

hi

quote from Kitz :
One thing I do notice - just what is that continual upstream of 5.5KB/Sec and downstream of 4.4KB/Sec?  Theres something on your PC that looks like its continually uploading.

This reminds me of the effect I had using "Drspeedtouch" monitoring  the st330. that seemed to be continuously comunicating. with drspeedtouch of it disappeared .

regards Jeff

[BritBrat]

I was reading this thread and thought I would do some of the tests.

I seem to have similar readings !!!

On 5th day of training with O2 had a fixed 2Meg with Zen before and always had max download speed at any time of the day.

2Wire (BT2700HGV) router with SBC 4.25.19 firmware

It leveled out to about 1Meg from a spike of around 7Meg

I have no underlying upload activity.

Could BTW be doing something as we both have a BT line but different ISP's.



Router stats:



It is better with the BT speed test than downloading the test files @ 21:00..



Even better with Usenet using two accounts and 12 total server connections.  (I did hit 5.9Mbps).



Another day and:

Another test at 5:30am using one and then two usenet accounts but only 4 total max server connections.



Followed by the BT speed test.

[streetfarm]

The continuous background up/download seems to come and go and I've no idea what it is.  It only affects one of the computers. so although it's an issue, I don't want it to detract from the main problem of low throughput.  I accept that over time it could lead to FUP issues, but considering that I'm now only on day 11 with BT, and I've not received any warning emails from them, I don't think it can be a deliberate ISP throttling issue.  Of course, it may be an accidental one, but then it would be a coincidence that Pipex had also done this as I had the same throughput rate with them.

Just to clarify - all the computers except the Mac are running Windows XP.

Here are today's stats and speedtest results, after 7 days of continuous connection.  Are the errors significant?


Connection information
Line state   Connected
Connection time   7 days, 0:41:41
Downstream   8,128 Kbps
Upstream   448 Kbps

ADSL settings
VPI/VCI   0/38
Type   PPPoA
Modulation   ITU-T G.992.1
Latency type   Interleave
Noise margin (Down/Up)   7.5 dB / 24.0 dB
Line attenuation (Down/Up)   2.0 dB / 1.5 dB
Output power (Down/Up)   7.8 dBm / 12.4 dBm
Loss of Framing (Local)   3
Loss of Signal (Local)   4
Loss of Power (Local)   0
FEC Errors (Down/Up)   1145 / 5
CRC Errors (Down/Up)   4 / 2147480001
HEC Errors (Down/Up)   4 / 2
Error Seconds (Local)   6

Test1 comprises of Best Effort Test:  -provides background information.
    Your DSL connection rate: 8128 kbps(DOWN-STREAM),  448 kbps(UP-STREAM)
    IP profile for your line is - 7150 kbps
    Actual IP throughput achieved during the test was - 446 kbps

If you wish to discuss these results please contact your ISP.

If you are experiencing problems with specific applications, servers or websites please contact your ISP for assistance.

Your test has completed please close this window to exit the performance tester.

I'm at a bit of a loss as to what to do next.  I suppose I will have to call BT, and try to get them to understand that it's most likely a BTW issue.

Thanks for all the replies so far.

Phil

[BritBrat]

So are you only getting 446 kbps download?

Less than your upload speed.

Or am I reading that wrong?

As we are both on the same 10 day period although I am with O2 you can compare my training against yours.

I started MAXdsl on Monday 26th and my first time on MAXdsl.

Mine seems to have settled down now and I can get a download speed of 6,000 kbps

Strange thing is your IP Profile is higher than mine but you have a lot slower download speed, don't make sense unless it is not doing the training and is stuck in some way.

Just a thought, have you turned router off at all?

On Monday I turned mine off over night as I read it could make it start a new profile, could yours still be stuck on the old one with the other ISP?

Turn it off for a night, worth a try I think.

so although it's an issue, I don't want it to detract from the main problem of low throughput.

I know you don't want to talk about that part now, but should that upload be using more than 80% of your maximum upload speed you will never get a good download speed.
If I were you right now I would be more concerned with who was using my bandwidth without my knowledge than the lack of speed, and the speed issue would be taking second place.

So if your underlaying upload speed was 360kbps or more your download would be very slow

MY 2 P.

[streetfarm]

Hi BritBrat,

So are you only getting 446 kbps download?

Less than your upload speed.

Or am I reading that wrong?

So it would appear!  I ran NetLimiter 2 Pro to investigate the continuous up/down load, and I have posted the screen shots.  I don't really understand them.  It appears that when i select 'Local Network' as the zone, then all of the traffic is from svchost.exe and when this is expanded i get loads of entries all relating to 192.168.1.254:8000, i.e. the Homehub.  If I change the zone to 'Internet' i get no traffic.  What does this mean?

I will switch off the Homehub overnight as you suggested and see what happens.





[attachment deleted by admin]

[BritBrat]

Are you connected to the hub by wire (ethernet cable)?

If so turn off the wireless access and see what happens.

Obviously you cant do that if you are connect through wireless

If I change the zone to 'Internet' i get no traffic.  What does this mean?

I think it means your PC is not using the bandwidth but something else on your LAN is.

But I must be honnest I am not sure myself, but that could be the whisky and it may make sence tomorrow

[kitz]

Your line is also interleaved - which is doesnt need - so it may be worthwhile asking your ISP to get that turned off at some point.

ISTR that you could not have an 8128/7150 connection interleaved.
I did think that interleaved was 7616/6500 max.

I remember chacking and when I had my connection changed my sync changed from 8128 to 7616 and vice versa.

Have I got it wrong?

Yes its possible on good lines - it also depends on both the router and the dslam being able to support something called S=1/2 mode, which combines 2x RS code words. 
(see ANSI T1.413)

ADSL1 is limited to 8128 due to the overheads, but running in s=1/2 mode can  increases this up to 16Mbps.
8128 is an artificial upper limitation set on BTw MSANs which can/ are running in s=1/2 mode.  - regardless if the line is interleaved or not.

[kitz]

With enormous respect to kitz et al, I can't see that it's an MTU problem.

iirc I admitted it doesnt have the feel of an MTU problem - hence why I left it as more of a last resort.  However MTU problems can have a large impact on throughput speed sometimes.

I myself have first hand experience where a very good line was at times limited to 1.2Mbps - 2Mbps.  This problem went on for months and a lot of time was spent trying to find out the problem.  In the end it was MTU and something that could be replicated.  I had discussions with one of the ISP networking bods about this and we both scratched our heads and to this day we still cant figure exactly how it had such a drastic effect.

The conclusion is that it must be some weird combination of factors.  Router/dslam chip, ISP, MTU.... and also Ellacoyas was in the mix.  The account was put on several different profiles to see if that made any difference, different account logins were tried. - even 'god profile'.
If I had not seen this with my own eyes - I too would have found it very hard to believe.

Theres also one of the mods of this forum that once saw a huge speed increase after MTU tweaking.. so although in this case it may not be the solution.. it is something that cant be ruled out.


@ britbrat - Ive not looked properly, but sometimes I 'get a feel' for things by just looking at the graph - yours looks more like a pattern displayed by congestion... with streetfarms the spike/low, could be during a catchup phrase often seen with ellacoya limiting.. which gives an overall average.  IP profiling would be flatlined.

Over the years both I and mr_chris have seen many DUMeter/Netmeter graphs and both of us seem to get a 'feeling' when you see a particular pattern when ellacoyas come into it.

Unfortunately though I cant say for sure what it is - needs to go back to the ISP   

[BritBrat]

I think mine is OK Kitz,

Was just trying to give streetfarm something to compare against as it seems we both started the MAX line training on the same day.

[streetfarm]

I switched the router off overnight as suggested.  When switched it back on this morning everything was the same as it was.

I tried calling the BT helpdesk this morning.  I waited 45 minutes while they kept telling me how important my call is!  I gave up.  I may try again later.

Meanwhile, I hope no one minds if I also post this problem on the BT forums website.  There may be someone somewhere with an identical problem, you never know.

I will still post any updates here, and please continue to post suggestions.

Regards,
Phil

[kitz]

Please do streetfarm, someone may come up with something that we have missed, its important that you get this issue resolved.

So far eliminated:

• Not a sync/connection speed issue - Line is at full sync
• Not an IP profile issue - IP porfile 7150
• Not caused through line conditions - Lack of CRC/HEC errors
• Checked secure wireless
• Checked for other network traffic - although something as yet unidentified at one point was using some upstream.
• Checked FUP not exceeded

 
Set up

• Engineer installed NTE5
• Tried different routers
• Checked filters

[BritBrat]

Good luck Phil, let us know what it was when sorted.

[Weaver]

[me getting off-topic]

Kitz wrote
> Theres also one of the mods of this forum that once saw a huge speed increase after MTU tweaking.. so although in this case it may not be the solution.. it is something that cant be ruled out.

@kitz
Agreed. And again btw, _do_ feel free to correct me if I was talking complete garbage earlier on this subject, because I presume that you have far more experience of seeing sufferers of this type of ill than I have.

But I would assume that there would have to have been true weirdness present, that is, weird ISP, weird router, broken o/s, or else if it was not an across-the-board thing but was specific to certain destinations, then we would need to have a weird server you correspond with, or weird network surrounding it. Would that be correct?

And I suppose encountering fragmentation at some remote router in a system where PMTU isn't available or isn't working would kill your performance because not only would there be the extra overhead of a second IP packet and its additional IP header plus all the PPPoA overheads that go with that second packet but also the overhead of possible extra cell only part-filled too, say perhaps for a small transgression, 2 cells = 106 bytes extra for a cost of 106/1500=7%. But I believe that there are operating systems that react by going down to the smallest datagram size [?], which would hurt even more.

[kitz]

Its always been maintained that MTU problems cause weird and wonderful symptoms.  MTU tweaking isnt needed as often these days - although for some reason Orange users seems to be having a bad bout on and off.
The case I mentioned is rare and not something you'd expect on a good line and I will readily admit I too would have doubted it could make that much difference - but it did.  There werent any other real symptoms - could even access the usual sites that are first sign of MTU such as M$, ebay etc.  It did fall prey to not being able to view the AARSE site - which for some reason is one of the sites that people with Voyager routers and MTU problems display.

I dont think its the case though here - gut feeling again.  The case I mentioned only saw it at peak times which is what is even more weird.. its almost as if when things were busy then there was more chance of packets being dropped.  I cant pretend to understand the hows and whys of it - but I am pretty sure that it occurs if Ellacoyas are in the mix too.  (which BT use).

I suppose its just one of those things I now keep at the back of my mind.  Ive tweaked so often that it only takes me a min to do it.. so for me its something that it cant harm to try if all else fails...  and with an added bonus that the RWIN may give you a bit more speed.
Most speed increases are achieved by setting a higher RWIN more appropriate to your connection speed.

RWIN is the amount of received data that you can accept (buffer) without having to send an acknowledgement to the remote host. With TCP it's the stop start action whilst waiting for an ACK during the sending/receiving of data that can slow things down. Now since the default RWIN is often too small for higher speed broadband connections, you can increase the size of your RWIN thereby allowing more data to be transferred at once, in turn reducing the pauses and thus speeding up your connection

I will agree with you that most MTU problems these days occur through PMTU breaking...  due to servers/routers blocking ICMP, which is when you get total blackholing.
I dont recommend tweaking RWINs unless you know what youre doing or how to calculate it - again hence the MTU/RWIN calculator which gives 'safe' pre-calculated values.

The other thing why MTU may have fallen a bit by the wayside when it comes to tweaking is that  once upon a time you would see rock steady consistent speeds - ie 478kbps/960kbps/1920kbps so you could immediately see any increases  That all went out of the window with radsl and its seldom to see the same speed from one min to the next...  therefore its harder to observe any real changes that may occur.