Simulating Internet Lag
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Thread: Simulating Internet Lag

  1. #1
    AO Decepticon CXGJarrod's Avatar
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    Simulating Internet Lag

    2 Windows 2003 Servers SP1 Updated fully with SQL 2005 Beta 2

    We are testing out the replication features in SQL 2005 (since they are supposedly improved from 2000) and we have hooked up the two databases to replicate to each other when changes are made to eithier one. Since these databases will be on the internet (Between German and US offices) the boss wants to replicate internet lag. We are looking about an average of 160-170ms lag (source ) between this office and Germany so I was wondering how we could replicate this on our network between 2 Windows 2003 Servers.

    I have been playing with the following MS Paramaters:

    - TCPWindowSize
    - MaxMTU
    - DefaultRcvWindow
    - DefaultTTL
    - DefaultMSS

    with not much sucess.

    Any ideas?
    N00b> STFU i r teh 1337 (english: You must be mistaken, good sir or madam. I believe myself to be quite a good player. On an unrelated matter, I also apparently enjoy math.)

  2. #2
    Right turn Clyde Nokia's Avatar
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    Could try using ping with the -t and -l switches on. Set it for maximum buffer size and how ever long you want?
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  3. #3
    AO Decepticon CXGJarrod's Avatar
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    Originally posted here by Nokia
    Could try using ping with the -t and -l switches on. Set it for maximum buffer size and how ever long you want?
    Actually did a version of this. A ping -f -l 1320 Ip address gives me just about the right amount of lag over the net. (to another one of our servers in the US) However, when I did add it to the registry, it didnt change anything over the local network. I suppose I could of entered it wrong, but was following the MS directions.
    N00b> STFU i r teh 1337 (english: You must be mistaken, good sir or madam. I believe myself to be quite a good player. On an unrelated matter, I also apparently enjoy math.)

  4. #4
    Right turn Clyde Nokia's Avatar
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    You may need to increase the packet size of your ICMP packet to notice it over a LAN. Especially if your WAN has less bandwidth than your LAN(which i suspect is the case?).

    What type/speed LAN are you running.

    You may also need to use the -t switch to keep the pings constant.
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  5. #5
    AO übergeek phishphreek's Avatar
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    Have you taken a look at any stress testing tools?

    I know foundstone has a couple...

    FSMax v2.0
    A scriptable, server stress testing tool.
    Download this Tool Now Click here for more information.

    » Blast v2.0
    A small, quick TCP service stress test tool.
    Download this Tool Now Click here for more

    » UDPFlood v2.0
    UDP packet sender utility.
    Download this Tool Now Click here for more information.

    http://www.foundstone.com/resources/stress_testing.htm

    Using something like Blast... you can do a continued ping and modify the blast parameters to your liking to get the "lag" that you're looking for. Are you doing this in a lab environment? On one segment? Across routers? If routers, look into bandwidth management and tweak the settings... or setup a frame relay simulation with a smaller CIR, etc. Don't know how big of a "pipe" you are using for your testing...

    just a couple of ideas for you since I don't know exactly what type of setup you're going for.
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  6. #6
    AO Decepticon CXGJarrod's Avatar
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    Phish: Just between a small test lab in our office here. Win2k3 Server ----- Hub ------ Win2k3 Server

    Not much that can manage in between.

    Ill check out the stress testing tools and see if that cant do something for us.

    Missed Nokia's post: Running the servers on their own 10 mb hub. Old sucker. Yes, the LAN is faster than the WAN. (1.5mb down 800k up)
    N00b> STFU i r teh 1337 (english: You must be mistaken, good sir or madam. I believe myself to be quite a good player. On an unrelated matter, I also apparently enjoy math.)

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