cancel
Showing results for 
Search instead for 
Did you mean: 

BBYW-1 @ 3Mbps - Reasonable?

Stewie
Grafter
Posts: 60
Registered: 09-06-2008

BBYW-1 @ 3Mbps - Reasonable?

Day 9 after activation. Are these BBYW-1 figures reasonable, or should I expect more speed.
[tt]BBYW-1 speed info (download)
----------------------------
router/DSL connection speed      8128 kbps
IP profile (speedtester.bt.com)  7150 kbps
IP thruput (speedtester.bt.com)  6375 kbps
Download speed (mybroadbandspeed) 3579 kbps (max at 0430AM)
Download speed (mybroadbandspeed) 1827 kbps (min 630pm)
Download speed (mybroadbandspeed) 3000 kbps (typical)
activespeed (ascentive.com test)  400 kbps (max)
router stats
link type    interleaved
noise margin  9 dB (downstream)
attenuation  23 db(downstream)  divided by 8 = approx 3. [/tt]
So expect 3mbps drop in thruput?
I am using the master socket.
After dialup, I am quite happy with this for now, it has been robust and the speed stable at around 3Mbps, dropping out only once, but if I can get more speed in the night that would be great, is that likely?
21 REPLIES
paulby
Grafter
Posts: 1,619
Registered: 26-07-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

As you're getting a reasonable speed on the BT tester you could try tweaking your MTU to see if you can get a better reult with PN.
If you're running Vista, you'll need to go here.
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

Yes that seems to help Paul thanks. I directly changed the routers MTU from 1500 to 1478. The benefit is more noticable on the upload rate because for the first time ever I'm getting upload rates > 384kbps,  namely 385 and 388 kbps. (testing with www.mybroadbandspeed.co.uk ).
The all important download rates seems better too @ 3404 and 3342 kbps, but its a bit early to tell given they vary a lot anyway and the tests are not very scientific. They certainly don't seem worse. Thanks. I may also try MTU = 1430 in the quiet hours. Huh
Community Veteran
Posts: 3,789
Registered: 08-06-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

More importantly, tweak your RWIN and make sure you reboot after changes.
With your connection stats, I would recommend an MTU of 1458 and an RWIN of 113440.  Try tweaking your connection to those values, REBOOT YOUR COMPUTER, then try another speedtester again (mybroadbandspeed)
B.
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

Gotcha Barry, will do exactly that. Thanks a lot!
paulby
Grafter
Posts: 1,619
Registered: 26-07-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

@Stewie
You can tweak RWIN if you're using Xp/2000.  It won't work in Vista however.  Vista manages RWIN automatically and it can't be tweaked and MTU changes need you to use the command prompt run as administrator. A reboot isn't needed with Vista.
If you're using Xp then I'd do as Barry suggests.  I found that the MTU=1430 and RWIN= 166800 settings suggested on Kitz's site gave me the best results. YMMV. (My Vista machine has its MTU set to 1430).
Also remeber to make sure that the MTU on your router has to be equal to or greater than that on your PCs (setting it to 1500 should be fine assuming it's adjustable).
Edit: typo
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

Yikes! With Pauls settings www.Mybroadbandspeed.co.uk now reports doubled download speeds of 6100kbps peaking at 6775kbps.
Uploads slowed from 380kbps to 340kbps.
According to http://www.dslreports.com/faq/578 my original XP default RWIN was 17520 and the default MTU was 1500.
That means we've gone from  RWIN == 12 x (MTU-40), to  RWIN == 120 x (MTU-40).
The only settings I changed in DrTCP were;-
[tt]Tcp Receive Window(RWIN)[      ] --> [166800]
MTU Path Discovery as  [default] --> [No]
Dialup RAS MTU as      [      ] --> [1430]
Adapter MTU            [      ] --> [1430][/tt]
Not sure about Path MTU Discovery. The documentation suggests it allow Windows to override your manual setting, so I made sure it couldn't anymore. No doubt this'll haunt me later if use a dialup on the pc.
My routers MTU setting is now 1500.


MickKi
Grafter
Posts: 543
Registered: 30-09-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

Both router and your PC(s) ethernet interface MTUs should be set at the same value.
To find out the maximum value that your MTU can be, set it at 1500 across all your devices then and run a ping test to a router/server of your choice out there in the WWW and set the don't fragment flag for different packet sizes: http://help.expedient.com/broadband/mtu_ping_test.shtml
These days most servers/routers are set with an MTU of 1500, so I doubt that the above test will show you a need for a lower MTU.  However, successive speed tests may reveal a difference and lower MTUs could give you a higher throughput, especially so with some servers/routers on the Internet and connections which carry a large overhead (e.g. VPN).
BTW, not all adapters have the same default MTU.  PPPoE is 1492, VPN is 1400, dial-up is usually 576 and BT ADSL used to advise 1458 for PPPoATM until they made some alterations at the BT exchange equipment to work with 1500.  Cable/ethernet MTU is 1500.
Path MTU discovery is a useful mechanism to ensure that your PC detects what is the maximum packet size that it can send to a remote host without fragmentation.  If you set EnablePMTUDiscovery 0 in your registry then all packets outside your local subnet will be reduced to just 576 bytes.  You are bound to achieve lower throughput speeds at that setting, so it's a better idea to set it at 1.
Hope this helps.
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

OK, Path MTU discovery is back on.
And I set MTU=1500 (and rwin=175200 =(MTU-40)x120), rebooted, and did the ping test.
ping www.bbc.co.uk -f -l 1472
was the biggest that worked, confiming that an MTU of 1500 is the optimum setting because the optimum MTU is the ping value + 28, say the instructions at http://help.expedient.com/broadband/mtu_ping_test.shtml.
After that www.Mybroadbandspeed.co.uk reported a download speed of 6873kbps, the fasted i've seen. Smiley
HOWEVER upload speed cut from 380kbps to 200kbps (with mybroadbandspeed) using these settings, so I looks like should have stayed with MTU of 1430 to avoid halving the upload speed.  Curiously the upload test 'fails' in a funny way, the speed indicator still reaches 384kbps as usual, but then at the end of the test it drops to 200kbps and continues a bit longer than normal - as if half the packets failed. Cry
paulby
Grafter
Posts: 1,619
Registered: 26-07-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

@stewie
Try pinging some other sites to see how you get on.  PN peers with the BBC so it's not necessarily going through a lot of poorly configured routers.
microsoft.com is worth trying!
I've seen instances where Windows Update won't work and reports strange errors unless the MTU is set to 1430!
You could spend hours tweaking trying to get a few more kbps out of your connection but in the end it's best just to pick a value that seems to work for you and leave it.  Remember also that your speed test results will vary depending on the time of day, network load etc.!
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

I'm now concerned about the halving of upload speed. Anyone any idea why the upload speed is now playing up (dropping to 200kbps after an upload).
Not even sure its connected with MTU RWIN tweaking, and not sure attempting to restore the assumed virgin defaults would work if I knew for what they were for sure.
What happens is that the progress dial gets to 100% at a speed of 380kbps approx but AFTER that the speed dial drops from 380 to 200kbps over a few seconds as if there is some slow buffering going on after the data was sent.
paulby
Grafter
Posts: 1,619
Registered: 26-07-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

@stewie
Use the settings I gave you and then try a speedtest here.  You could also retry the BT speedtester. (Different testers will report different results depending on where they're located etc.).  From your figures those settings were giving pretty good results - you're not going to notice much difference between 6775 and 6873 Kbps to be honest (it's also likely that these figures are within the bounds of normal variation).  A 40Kbps difference in upload also isn't going to make much difference (and may change with subsequent tests). You need to do a few tests to get an accurate picture of your line over time - one off "snapshots" will only tell you if things have moved significantly.  Changes of a few Kbps are within the normal spread of results for a line.
Here are the last few results for my line:
                         Downstream Upstream
18/06/08 21:25  5829.41 Kbps 340.10 Kbps   
06/06/08 23:50  6215.12 Kbps 340.24 Kbps 
04/06/08 23:37  6217.29 Kbps 340.24 Kbps   
02/06/08 23:11  6206.99 Kbps 340.31 Kbps   
27/05/08 20:53  5120.17 Kbps 260.12 Kbps 
26/05/08 23:16  5748.85 Kbps 332.39 Kbps   
25/05/08 20:48  6166.44 Kbps 339.93 Kbps

There's even a one-off drop to 260Kbps on the upstream side when things may have been busy on the network or at my exchange!
As I said before, you could spend hours tweaking the RWIN and MTU.  It's best just to settle on a value that gives you the best results and leave it.
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

Thanks - I am most grateful for you doubling my download speed, and I am NOT trying to squeeze 40kbps more out of downloads, as you say it's time consuming, and I am more than happy with that. Especially after dialup, and the problem others have - thanks.
Your reply suggests that I maybe right to consider a 200kbps typical upload rate as low. 
As a broadband newbie some expectations are still uncertain. I hope you understand.
My question is; is this halved upload rate caused by the tweaks? You may disagree but I think the cost of halving the relatively slow 380kbps upload rate may be significant  and I wondered if you'd suggest reverting the changes when there are uploads to do,  or finding a tweak/fix for the low upload speed, or accepting that 200kbps is a typical upload rate. Despite the coincidence it seemed to become the norm after the improved download rate.
I apologise if this is getting a bit annoying, especially since you've already been such a great help.  Wink
paulby
Grafter
Posts: 1,619
Registered: 26-07-2007

Re: BBYW-1 @ 3Mbps - Reasonable?

200Kbps is a bit low!
What have you got your MTU/RWIN set to just now?
Have you tried another speed test site?
It seems that your problem started (judging by your posts) when you set things back to an MTU of 1500!
Quote
And I set MTU=1500 (and rwin=175200 =(MTU-40)x120), rebooted, and did the ping test.
..... confiming that an MTU of 1500 is the optimum setting ....
...HOWEVER upload speed cut from 380kbps to 200kbps (with mybroadbandspeed) using these settings.

As I said earlier, this is only the optimum setting to the BBC site you pinged.

Set the MTU on your PC back to 1430 (you can leave the router at 1500) and RWIN to 166800 and see how your upload fares.
If it's any help, here are the settings I've got on my Xp machine:
TCP Receive window - 166800
Windows Scaling - Yes
Time Stamping - No
Selective Acks - Yes
Path MTU Discovery - Yes
Black Hole Detection - Yes
Duplicate Multiple Acks - 2
TTL - 128
Max MTU - 1430
To return to Windows defaults, leave the TCP receive window field blank and set the MTU=1500 and TTL to 64.
Stewie
Grafter
Posts: 60
Registered: 09-06-2008

Re: BBYW-1 @ 3Mbps - Reasonable?

I also had the same problems with your settings - except my TTL was 64 instead of 128.
I will use exactly the same settings as you and see if that helps.
Thanks.