View Poll Results: Is anybody else suffering with slow connections on BT Broadband?

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Thread: BT Broadband speed question

  1. #1
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    Question BT Broadband speed question

    A very warm hello to you all from a new member. I got a reasonable question to start off with, and would very much appreciate your opinions on this one.

    I currently am subscribed to BT Broaband in the UK, up to 8 megabit, and I am connecting via an etec/connexant/hasbani modem-router (PT-3812). As far as I am aware this router is well capable of 8 megabit, and I have updated to the latest STABLE firmware for it.

    I am also connecting via cat 6 cable (1 gigabit capability) although the router is only capable of 100 Megs, which it achieving admirably.

    I am running with Windows XP Professional, Service Pack 2 and Internet Explorer 7. I am using a third party firewall (ZoneAlarm Pro) and have disabled the Windows firewall.

    Now to the questions. Upon interrogating my router, it is telling me that my line speed is between 7 mbit and 7.5 mbit (which is fair enough, I don't expect the full 8, no problems). So I have adjusted my MTU to 1500 and my MSS to 1460, as recommended. I have also run the Optimiser and adjusted the Windows registry to reflect these changes, and adjusted my rwin settings.

    Here is the result of the TCP/IP Analyzer:

    TCP options string = 020405a00103030301010402

    MTU = 1480
    MTU is optimized for Windows XP PPoE DSL broadband. If not, consider raising MTU to 1500 for optimal throughput.

    MSS = 1440
    MSS is optimized for Windows XP PPPoE DSL broadband. If not, consider raising your MTU value.

    Default TCP Receive Window (RWIN) = 514080
    RWIN Scaling (RFC1323) = 3 bits (scale factor of 6)
    Unscaled TCP Receive Window = 64260

    RWIN is a multiple of MSS
    Other RWIN values that might work well with your current MTU/MSS:
    506880 (MSS x 44 * scale factor of 8)
    253440 (MSS x 44 * scale factor of 4)
    126720 (MSS x 44 * scale factor of 2)
    63360 (MSS x 44)

    bandwidth * delay product (Note this is not a speed test):

    Your TCP Window limits you to: 20563 kbps (2570 KBytes/s) @ 200ms
    Your TCP Window limits you to: 8225 kbps (1028 KBytes/s) @ 500ms

    MTU Discovery (RFC1191) = ON

    Time to live left = 44 hops
    TTL value is ok.

    Timestamps (RFC1323) = OFF
    Selective Acknowledgements (RFC2018) = ON

    IP type of service field (RFC1349) = 00000000 (0)

    TCP Window based on setting the slider to 7000 to reflect the speed reported by my router. Maybe I should set this at around 90 percent of what my router is telling me?

    SG Speed Test as follows:
    4281 kbps down (~4.28 Mbps, 523 KB/s) ↓
    345 kbps up (~0.35 Mbps, 42 KB/s) ↑
    Details:

    10240 KB downloaded in 19.594 seconds
    1024 KB uploaded in 24.313 seconds
    Speed @ 213% of the average for btcentralplus.com
    81 times faster than 56k dialup
    Tested on: 2007.04.04 20:14 EDT
    Tested from: host-easy.co.uk
    Test ID: 0GP7YUXSDWIR
    User Test History: User Stats
    Browser/OS: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)
    IP Address: 86..xxx.xx.xxx
    Latency: 129ms
    Provider: btcentralplus.com
    Location: UK

    A latency of 129ms is apparently good for my geographic region (?)

    These speeds are a best-case scenario, they actually get a lot worse on average, sometimes down as low as 2 mbit.

    Now to the questions:
    At a reported line speed of approximately 7 mbit at the modem-router, I am currently only realising around two-thirds of my reported maximum, and that is after tweaking.

    Is this the best speed I can achieve using these settings or should I be getting a little more?

    Should I reduce my TCP Window downwards to limit it to the throughput values reported in the speed test?

    Notice the MTU and MSS are reporting 1480 and 1440 despite me having set them to 1500 and 1460 in BOTH the router AND windows. My ISP actually requires a pppoA setting so something is amiss here methinks. Is this reporting correctly?

    I am getting around 11 crc errors every hour (around 8.5 errored packets) which I assume is very good. Is this acceptable?

    Please peruse this at your leisure and post back your opinions when convenient, I would be very interested in your answers.

    Many thanks
    Shadstar

  2. #2
    Elite Member trogers's Avatar
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    Try the following with TCP Optimizer to see if your MTU can be increased:

    General Settings tab:
    Custom settings - check
    Modify All Network Adapters - check
    network adapter selection - your NIC
    MTU 1500
    TTL - 64
    TCP Receive Window - leave blank
    MTU Discovery - Yes
    Black Hole Detect - No
    Selective Acks - Yes
    Max Duplicate ACKs - 2
    TCP 1323 Options:
    Windows Scaling - checked
    Timestamps - uncheck

    Advanced Settings tab:
    Max Connections per Server - 10
    Max Connections per 1.0 Server - 20
    LocalPriority - 1
    Host Priority - 1
    DNSPriority - 1
    NetbtPriority - 1
    Lan Browsing speedup - optimized
    QoS: NonBestEffortLimit - 0
    ToS: DisableUserTOSSetting - 0
    ToS: DefaultTOSValue - 80
    MaxNegativeCacheTtl - 0
    NetFailureCacheTime - 0
    NegativeSOACache Time - 0
    LAN Request Buffer Size - 32768
    Then select "Apply Changes" and reboot to take effect

    After reboot, post a new TCP Analyzer report.

  3. #3
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    Thank you for your reply, much appreciated. My apologies for the delay in replying, it was around 3am local time when I posted, and I had to get some sleep, so I have just got back online.

    I have done as you suggested, and here are the resluts:

    TCP Analyzer results:

    TCP options string = 020405a00103030e01010402

    MTU = 1480
    MTU is optimized for Windows XP PPoE DSL broadband. If not, consider raising MTU to 1500 for optimal throughput.

    MSS = 1440
    MSS is optimized for Windows XP PPPoE DSL broadband. If not, consider raising your MTU value.

    Default TCP Receive Window (RWIN) = 1073725440
    RWIN Scaling (RFC1323) = 14 bits (scale factor of 28)
    Unscaled TCP Receive Window = 65535

    RWIN seems to be an excessively large number. If you're on a line lower than 20 Mbps (that is not satellite), consider using a smaller value.
    For optimum performance, consider changing RWIN to a multiple of MSS.
    Other RWIN values that might work well with your current MTU/MSS:
    506880 (MSS x 44 * scale factor of 8)
    253440 (MSS x 44 * scale factor of 4)
    126720 (MSS x 44 * scale factor of 2)
    63360 (MSS x 44)

    bandwidth * delay product (Note this is not a speed test):

    Your TCP Window limits you to: 42949018 kbps (5368627 KBytes/s) @ 200ms
    Your TCP Window limits you to: 17179607 kbps (2147451 KBytes/s) @ 500ms

    MTU Discovery (RFC1191) = ON

    Time to live left = 44 hops
    TTL value is ok.

    Timestamps (RFC1323) = OFF
    Selective Acknowledgements (RFC2018) = ON

    IP type of service field (RFC1349) = 00000000 (0)


    SG Speed Results:

    5243 kbps down (~5.24 Mbps, 640 KB/s) ↓
    348 kbps up (~0.35 Mbps, 43 KB/s) ↑
    Details:

    10240 KB downloaded in 16 seconds
    2048 KB uploaded in 48.188 seconds
    Speed @ 261% of the average for btcentralplus.com
    99 times faster than 56k dialup
    Tested on: 2007.04.05 05:17 EDT
    Tested from: host-easy.co.uk
    Test ID: VY0JGI69UWM9
    User Test History: User Stats
    Browser/OS: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)
    IP Address: 86.xxx.xx.xxx
    Latency: 130ms
    Provider: btcentralplus.com
    Location: UK


    A slight improvement although I still can't seem to get my MTU over 1480 for some reason, and the RWIN value seems to have jumped to a very large number.

    I hope this helps you guys.

    I have also emailed my isp as well, and have asked about the latency (which seems to be a common value for the area I live in, so I am told), just to be sure that there isn't a problem with my connection. I have already had their usual reply of "your line appears to be wiorking correctly sir..." (bless 'em) (!)

    Thanks again
    Regards
    Shadstar

  4. #4
    Elite Member trogers's Avatar
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    Try the following with TCP Optimizer:

    General Settings tab:
    Custom settings - check
    Modify All Network Adapters - check
    network adapter selection - your NIC
    MTU 1480
    TTL - 64
    TCP Receive Window - 253440
    MTU Discovery - Yes
    Black Hole Detect - No
    Selective Acks - Yes
    Max Duplicate ACKs - 2
    TCP 1323 Options:
    Windows Scaling - checked
    Timestamps - uncheck

    Advanced Settings tab:
    Max Connections per Server - 10
    Max Connections per 1.0 Server - 20
    LocalPriority - 1
    Host Priority - 1
    DNSPriority - 1
    NetbtPriority - 1
    Lan Browsing speedup - optimized
    QoS: NonBestEffortLimit - 0
    ToS: DisableUserTOSSetting - 0
    ToS: DefaultTOSValue - 80
    MaxNegativeCacheTtl - 0
    NetFailureCacheTime - 0
    NegativeSOACache Time - 0
    LAN Request Buffer Size - 32768
    Then select "Apply Changes" and reboot to take effect

    After reboot, test your speed at this link using the test servers in the UK:

    http://www.speedtest.net/

  5. #5
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    Thumbs up

    Hello

    Yeah, definitely improved. The Speedtest link you recommended gave me around 5657 down (around 80 percent of my reported line speed) and 354 up (kilobits). The SG Speed Test link on this site gave me slightly lower:

    4898 kbps down (~4.9 Mbps, 598 KB/s) ↓
    347 kbps up (~0.35 Mbps, 42 KB/s) ↑

    but nevertheless, despite the differences, better than I was getting.

    I notice that data throughput is a lot more stable as well. On a second test I fired up Windows Perfmon and monitored activity through my nic and there was a lot less "jumping", the stream seemed to be quite stable which is a good sign.

    Am I correct in assuming that my MTU is at the optimum value at 1480?

    Thank you for you guidance in this, it is very much appreciated.

    Regards
    Shadstar

  6. #6
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    Thumbs up

    Just a quick update, I have stumbled across a live webcam from Oxford University which is streaming at an incredible rate of around 600k.

    Since applying the tweaks kindly mentioned in this post I am getting this with no breaks or delays at all. It is still running even as I am posting this.

    Thanks to trogers for his help so far, much appreciated.

    Regards
    Shadstar
    Last edited by ShadStar; 04-05-07 at 08:11 AM. Reason: spelling error

  7. #7
    Elite Member trogers's Avatar
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    Quote Originally Posted by ShadStar View Post
    Am I correct in assuming that my MTU is at the optimum value at 1480?
    I believe BT Broadband is using ADSL system and normal ethernet connection can have MTU set to 1492, meaning MTU is set to 1492 in both the Windows registry and also at the router.

    You are running Windows DSL PPPoE and that is why your MTU is fixed at 1480.

    Speed difference is only 1-2% between these 2 MTU values. If your system is now running smoothly, keep your present MTU and RWIN values.

  8. #8
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    Hi
    Not a problem, I am happy with these settings, it has increased my speed from around 66 percent to around 80 percent of my reported line speed. I do appreciate your advice and I will be staying with these values.

    Just as an aside, it is interesting that BT Broadband actually advise setting the router for a PPPoA connection, however I do understand that I am connecting via ethernet to my router, which of course means that Windows uses PPPoE values. The actual modem inside the router would be transparent to the operating system...

    No matter, the connection is now stable and I am a happy bunny and no more tweaking will be done. Thanks for your help.

    Regards
    Shadstar
    Last edited by ShadStar; 04-05-07 at 12:45 PM. Reason: Made my response a lot clearer to understand.

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