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Thread: Why is VPN slow to some sites, but not all?

  1. #1

    Why is VPN slow to some sites, but not all?

    If I run a Broadband speed test to sites in US and Europe from my PC I get speeds of nearly 1.5Mb which is as expected as my ISP download speed is 1.5Mb.

    I then connect to my own dedicated VPN server in the UK (same Windows XP over PPTP or OpenVPN), but the speed is maintained at a typical 1.3Mb to 1.5Mb.

    I then connect to my own dedicated VPN server in the US (Windows XP PC connecting via both PPTP or OpenVPN), and the speed drops significantly to 300Kb to 600Kb.

    My question is, why is there such a massive degredation in speed over the VPN, but only to certain countries? (I am connecting from the Middle East at the moment).

    That I get a fast UK connection, but slow US would seem to rule out the ISP at my end, I think....

    I am trying to figure out if perhaps the VPN server on the US server (CentOS) is misconfigured? Or could it be that my ISP somehow throttles or "shapes" VPN traffic traversing specific routes? (If they did that I'd have thought they'd do it to all sites?) Is it even feasible/likely that an ISP would deliberately look for and slow down VPN traffic?

    Just to complicate matters, a friend in Canada connects to the US VPN server and tells me he gets 3Mb download speed over VPN (has a faster ISP, don't know his max download speed). Perhaps this indicates that VPN performance degredes at a geometric rate depending on speed, eg up to 2,000 miles a small degredation, 5,000 miles a massive degredation?

    Does anyone have detailed VPN over Broadband knowledge that could shed some light on this?

  2. #2
    Moderator YeOldeStonecat's Avatar
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    VPN traffic isn't usually shaped by an ISP in the US. The important part of the VPN connection is the upload at the VPN host. What is the benchmarked upload at the VPN host of each of your 2 sites?
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  3. #3
    Thanks for replying.

    By "benchmarked" do you mean the advertised available speed, or actual measured speed?

    The US site is hosted at burst.net and they don't explicitly say what the speed is other than implying the server's on at least a 10Mb port. They tested the speed of the server and got at least 4Mb/sec. Someone from Canada allegedly got 3Mb/sec over VPN. That probably would have been downloading a file, but in order to download at 3Mb, that file presumably would have to upload at at least 3Mb?

    The UK site is hosted at rapidswitch.com and they advertise a 100Mb/sec connection. I don't have any specific measurements, other than being able to get a full 1.5Mb from it via the VPN which I am happy with.

  4. #4
    burst.net just told me that their server (the US one) can burst up to 100Mb/sec.

  5. #5
    Moderator YeOldeStonecat's Avatar
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    Quote Originally Posted by greenyoda2000 View Post
    Thanks for replying.

    By "benchmarked" do you mean the advertised available speed, or actual measured speed?
    Benchmark means tested measured speed by doing a bunch of them and getting an average, not what the ISP claims you can get up to. Measured at the host.

    What is doing the actual VPN server duties?

    "Bursting" speeds advertised by ISPs for co-lo'd servers can be misleading.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  6. #6
    Benchmark speeds:

    From the perspective of a PC connected to the VPN servers:

    US:

    Download: 7533Kbs
    Upload: 286Kbs


    UK:

    Download: 4007Kbs
    Upload: 461Kbs


    At the moment these VPN servers are pretty much idle otherwise.

  7. #7
    Moderator YeOldeStonecat's Avatar
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    Can you remote desktop to the servers? The reliable benchmarks are speedtests done at console right at the servers themselves...not through a connection.

    What is doing the actual VPN serving? Is this just RRAS service through Windows?
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  8. #8
    It's a Linux server with no desktop setup.

    I have a PPTP VPN and separate OpenVPN. Both are very slow. It seems they are only slow from client PC's connecting from across the Atlantic. Direct connections from the same PC to the same test servers, but without connecting over the VPN(s) run at full speed, which is why I don't think it is the ISP at this end.

    Could it be that the Server host has "dodgy" connection, with good routes to American cities where the speed servers are located, but poorer routes to the rest of the world?

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