Slow VPN

Discussion in 'Server Networking' started by Smart, Sep 30, 2004.

  1. Smart

    Smart Guest

    I used the following KBs to install and configure VPN on
    Windows Server 2003 and XPs pro.

    How To Install and Configure a Virtual Private Network
    Server in Windows Server
    2003http://support.microsoft.com/?id=323441

    How to configure a connection to a virtual private
    network (VPN) in Windows XP
    http://support.microsoft.com/?id=314076

    The data outbound is working fine and as expected, but
    the inbound is very slow at 28kb/s, which is creating
    kind of bottleneck in the connection adsl 512/128.

    Any help please ?

    Regards
     
    Smart, Sep 30, 2004
    #1
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  2. One thought is to tweak the MTU for your DSL connection. You would have to
    check the device docs for instructions. Make sure you document your current
    setting and change the setting just a bit at a time. I think aroud 1450 may
    be a good place to start. I don't use DSL anymore. --- Steve
     
    Steven L Umbach, Sep 30, 2004
    #2
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  3. Smart

    Smart Guest

    Hi Steve

    With all due respect, I didn't understand a thing you've
    said. "tweak the MTU" and "around 1450 may be a good
    place to start". I can't understand. I am sorry, there
    must be something more straightforward and better than
    that... :-D

    Regards
    You would have to check the device docs for instructions.
    Make sure you document your current setting and change
    the setting just a bit at a time. I think aroud 1450 may
    be a good place to start. I don't use DSL anymore. ---
    Steve
     
    Smart, Sep 30, 2004
    #3
  4. Smart

    Todd J Heron Guest

    Todd J Heron, Sep 30, 2004
    #4
  5. Smart

    Smart Guest

    Smart, Sep 30, 2004
    #5
  6. OK. See the link below for more details. MTU stands for maximum
    transmissiion unit and if it is too large you can end up with packet
    fragmentation that will slow down data transmission. The pppoe connectoid or
    the router device will have configuration settings to change the MTU size.
    Check your docs for what you are using. It may also help to contact your ISP
    if their support staff is on this planet. The manufactures of most routers
    will have their full manual on their website or a FAQ that may be able to
    help you out. --- Steve

    http://www.allaboutjake.com/network/linksys/mtu.html
     
    Steven L Umbach, Sep 30, 2004
    #6
  7. Smart

    Smart Guest

    Thanks

    I followed step-by-step KB 323441 and I contend that there is no reason why
    it should not work 100%. There must be something else somewhere else I
    should check or uncheck. With a network of 130 users, I am not quite keen
    on suggestions which may affect in one way or another my environment. I
    would very much appreciate a helpful suggestion or at least the reason why I
    am experiencing this problem, and if I need to change anything in relation,
    for example, to the hardware. Of course, I remain at your disposal for any
    further information you may require.

    Regards

    OK. See the link below for more details. MTU stands for maximum
    transmissiion unit and if it is too large you can end up with packet
    fragmentation that will slow down data transmission. The pppoe connectoid or
    the router device will have configuration settings to change the MTU size.
    Check your docs for what you are using. It may also help to contact your ISP
    if their support staff is on this planet. The manufactures of most routers
    will have their full manual on their website or a FAQ that may be able to
    help you out. --- Steve

    http://www.allaboutjake.com/network/linksys/mtu.html
     
    Smart, Sep 30, 2004
    #7
  8. Keep in mind that your uplink speed is one fourth of your download speed.
    Add into that the overhead of VPN with encryption and resultant extra packet
    size and it will seem slow. I had a that same uplink speed at my business
    and it was painfully slow. Also the thought of MTU adjustment would be an
    adjustment with your DSL router - not your actual VPN configuration with the
    server. I use a Netgear NAT router/firewall and I can adjust the MTU on it
    which will not in any way affect internal non WAN network performance. ---
    Steve
     
    Steven L Umbach, Sep 30, 2004
    #8
  9. Smart

    Bill Grant Guest

    It is worth noting that inbound traffic (ie inbound to the VPN server)
    will depend on the rate that the client can send. If the client has a slow
    uplink, that controls the throughput.
     
    Bill Grant, Oct 1, 2004
    #9
  10. I guess you said it better than me Bill. I had a VPN between work and home.
    Cable modem at home and DSL at work. They both had great download speeds
    with the cable modem being blazingly fast from places like Microsoft. But
    when using the VPN on either end from the other it was sloooooooow. I think
    they were both limited to 128k uplink. --- Steve
     
    Steven L Umbach, Oct 1, 2004
    #10
  11. The "slow side" of the DSL is the speed that VPN will always run at. It will
    not use the "faster side" of the DSL. So you start out with the slow side
    to begin with and then add all the other factors (and possible problems) on
    top of that.
     
    Phillip Windell, Oct 1, 2004
    #11
  12. Wouldn't that depend on the speed of VPN on each side though and the
    direction of the bulk to the network activity? If I had a 512/128 DSL with
    a VPN to a remote site with a 512/512 connection I would expect that for
    file transfers when I was copying a file to the remote VPN it would be a lot
    slower than when I would be copying a file from it. --- Steve


     
    Steven L Umbach, Oct 1, 2004
    #12
  13. Someone tried to explain it once and I think my eyes glazed over, but what
    it all said was that VPN always follows the slower "upload" speed of a duel
    speed DSL or Cable (runs at 128 for a 512/128 line). If the two involved
    Cable/DSLs were not the same speed (512/521 vs 521/128) then I am pretty
    sure it goes with the lowest common denominator (128) similar to the way it
    was with the old modem technology. I suspect that the creation of the
    Tunnel causes this in getting everything to be in sync.

    If you want exact details, I don't think I could give them.

    --

    Phillip Windell [MCP, MVP, CCNA]
    www.wandtv.com


     
    Phillip Windell, Oct 1, 2004
    #13
  14. Smart

    Bill Grant Guest

    Hi Phillip. That was me. Sorry your eyes glazed over!

    I'll try it again. The A in ADSL stands for asymetric. It indicates that
    the send and receive rates are not equal. Commonly, download is 4 times
    faster than upload. If you use it for Internet access, that's fine, because
    you normally download much more than you upload.

    Now look at VPN. As an example, take a site with a 1meg/256k ADSL
    connection and a client with a 256/64k ADSL.

    From server to client, the send rate is 256k and the client receive is 256k
    .. Great!

    Now look at the other way. Server receive rate is 1 meg, but client send
    rate is 64k ! Think dialup modem speed.

     
    Bill Grant, Oct 2, 2004
    #14
  15. Yes it was! Don't worry about the eyes glazing over :),...they do that
    sometimes.
    I understood that part. It was the part about the VPN itself seeming to
    lock into the slowest speed (lowest common denominator) no matter which
    direction it was going,...so the higher speed in one direction never gets
    used,...while other non-VPN traffic never suffered from that. I have assumed
    it was due to the Tunnel having to "sync" up at each end so it goes with the
    slowest speed similar to the way the old modems of different speeds settles
    on the speed of the slowest modem.
     
    Phillip Windell, Oct 4, 2004
    #15
  16. Smart

    Bill Grant Guest

    No, I haven't struck that. And the original poster (remember him way back
    at the top?) didn't seem to have it either. The transfer from server to
    client was good, client to server was slow.
     
    Bill Grant, Oct 5, 2004
    #16
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