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Thread: MTU problem

  1. #1
    atropal
    Guest

    Cool MTU problem

    Previously posted in another Forum
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    After running the 'TCP/IP Analyzer' I got this message:
    <MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput>
    I looked everywhere to find out how to change the MTU. Can you help ?
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    Posts: 5 | From: Montreal, Canada | Registered: Apr 2001 | IP: Logged

    blebs99
    Advanced Member
    Member # 7113
    posted 04-25-2001 08:19 AM
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    Could you copy and paste a copy of your TCP/IP test please. How do you connect? What operating system? Any proxy or routers installed? Have you installed any tweak patches of any kind?
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    Posts: 697 | From: N. Canton, Ohio | Registered: Dec 2000 | IP: Logged

    atropal
    Member
    Member # 11467
    posted 04-25-2001 08:48 AM
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    I run on Win98 from a P3-450 computer, connected through a router (Netgear) using a DSL connection (with Bell-Sympatico in Canada). Copy of the test below.
    Thanks, Philippe
    I have not installed any patch myself. Explorer 5.5, Win98

    HERE IS A COPY OF MY TEST:
    ==========================
    TCP options string = 02040578010303020101080a000000000000000001010402

    MTU = 1440
    MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput.

    MSS = 1400
    Maximum useful data in each packet = 1388, which is less than MSS because of Timestamps, or other TCP/IP options used.
    MSS is not fully optimized for broadband (although it might work well for slower connections). Consider increasing your MTU value.

    Default Receive Window (RWIN) = 256960
    RWIN Scaling (RFC1323) = 2 bits
    Unscaled Receive Window = 64240
    For optimum performance, consider changing RWIN to a multiple of MSS.
    Other values for RWIN that might work well with your current MTU/MSS:
    515200 (MSS x 46 * scale factor of 8)
    257600 (MSS x 46 * scale factor of 4)
    128800 (MSS x 46 * scale factor of 2)
    64400 (MSS x 46)

    bandwidth * delay product:
    Your RcvWindow limits you to: 10278.4 kbps (1284.8 KBytes/s) @ 200ms
    Your RcvWindow limits you to: 4111.36 kbps (513.92 KBytes/s) @ 500ms

    MTU Discovery (RFC1191) = OFF

    Time to live left = 50 hops
    TTL value is ok.

    Timestamps (RFC1323) = ON
    Note: Timestamps add 12 bytes to the TCP header of each packet, reducing the space available for useful data.

    Selective Acknowledgements (RFC2018) = ON

    IP type of service field (RFC1349)= 00000000


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    Posts: 5 | From: Montreal, Canada | Registered: Apr 2001 | IP: Logged

    blebs99
    Advanced Member
    Member # 7113
    posted 04-25-2001 08:52 AM
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    I'm not a dsl person myself, but is this a PPPoE dsl connection-do you have to dial in to log on?
    Is the IP address being tested the IP that is on your computer or your router?
    [ 04-25-2001: Message edited by: blebs99 ]


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    Posts: 697 | From: N. Canton, Ohio | Registered: Dec 2000 | IP: Logged

    atropal
    Member
    Member # 11467
    posted 04-25-2001 08:55 AM
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    I really do not know. This is past my technical knowledge.
    Hoe can I tell ?
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    Posts: 5 | From: Montreal, Canada | Registered: Apr 2001 | IP: Logged

    blebs99
    Advanced Member
    Member # 7113
    posted 04-25-2001 08:59 AM
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    Go to start/run/type in winipcfg/click more info/ look for header that says IP Address.
    Just be sure that the tester isn't grabbing the results for the wrong component. Your Computer IP is the one to be concerned about at this point.
    You don't have to dial up to log on to the ISP do you?
    [ 04-25-2001: Message edited by: blebs99 ]


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    Posts: 697 | From: N. Canton, Ohio | Registered: Dec 2000 | IP: Logged

    EvilAjax
    Advanced Member
    Member # 10646
    posted 04-25-2001 09:29 AM
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    He might have PPPoE and not know it, the router does the dialing for him (if he indeed does have a PPPoE connection). Right click Network Neighborhood, click Properties. Look at the list of network components, if you see any of them with PPPoE then you are connected by PPPoE. Another way to know is, do you see two green little monitors (its an icon) in your system tray? (that's where your clock is) If so, then that means you had to log in in order to establish a connection. Download the cablenut adjuster from my signature, tell me all the answers from what I stated above. We're going to turn off timestamps, change your MTU for maximum throughput, and go through several rwins to see which suits you best. Good luck.
    --------------------

    um... yeah

    www.speedguide.net "Some of the best Broadband tweaks and Speed patches on the Net " www.microsyspro.com "Tweak your broadband connection for better speed" www.cablenut.com Two words: Cablenut Adjuster.. or maybe three..??
    Click here to download Cablenut Adjuster 4.0 - "The best tweaking utility, ever!" -EvilAjax
    TCP/IP Analyzer -"The best and most handy analyzer on the net" -EvilAjax
    Ice Cold 'Patches' Here
    MS Vtcp.386 fix for Windows 98 Install and reboot for changes to take effect.
    Here's an editorial about "Uncapping" Three words "Don't Even Bother"
    You never know what you're capable of until you try it.


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    Posts: 349 | From: New York City | Registered: Mar 2001 | IP: Logged

    atropal
    Member
    Member # 11467
    posted 04-25-2001 08:42 PM
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    sorry I had to close up this orning.
    I checked both ways:
    1) My IP adress was not the rght one.
    2) I do not seem to be on PPPE as there is only TCP/IP listings (3 of them)
    I downloaded some tweak this morning and the system is screwed-up (sorry for the language)
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    Posts: 5 | From: Montreal, Canada | Registered: Apr 2001 | IP: Logged

    blebs99
    Advanced Member
    Member # 7113
    posted 04-25-2001 09:42 PM
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    I don't understand DSL enough when routers are in the picture to help you on this one. You can either stay here and wait for someone to pick up where we left off, or you can repost the questions in the tweaks forum and someone should be able to help you down there. I'm Sorry, but I think I'd mess you up more then help. Someone should be along shortly or like I said, repost in tweaks forum. Have a good evening!

  2. #2
    TCP/IP Dude rmrucker's Avatar
    Join Date
    Sep 2000
    Location
    Long Beach, CA, USA
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    896

    Post

    This is standard operating procedure for the NetGear router on PPPoE. Here is a temporary work around:

    Telnet to the Router by doing this:

    Go to Start/Run... then type "telnet 192.168.0.1" (no quotes) and press OK. Now enter your password... (the original is 1234). You will get a menu.

    In the menu, find 24.8. At command prompt type:

    "ip adj wanif0 1452" (no quotes). Enter.

    This will increase the current MSS limit to 1452, hence the MTU will be 1492. The catch is that every time your PPPoE disconnects and re-connects it will revert back to MSS limit of 1400 (MTU of 1440) and needs to be entered after PPPoE connects again. This command does not work before PPPoE connects.

  3. #3
    atropal
    Guest

    Post

    thank you so much, this is marvelous
    atropal

  4. #4
    Registered User Mr White's Avatar
    Join Date
    Mar 2001
    Posts
    303

    Post

    I have the same dsl in ontario.You have to do this to keep your mtu 1492.disregard what you have just done,do this.I had the same problem..If your on PPPoE connection then the MaxMTU value has to be set at 1492,not 1500.
    Go into your registry (run,regedit)
    find this key: HKLM/system/current control set/services/class/net/0002
    should be in 0002 but check the others,look for MaxFrameSize,change this value to 1492 then restart.Should be fixed

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