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Thread: About tp analyzer results.

  1. #1
    Junior Member
    Join Date
    Jan 2020

    About tp analyzer results.

    Greetings. No matter what I do as per instructions, my MSS stays stuck at 1460. I have done the ping isp test and have spectrum effective (meaning probably not) claimed 100mbps broadband and the highest packet I can send is 1472 with 1500 setting. The 1460 doesn't seem right as it states I'm limited to 2621/1049 when other people are much higher. I also can't set the top recommended rwin. Am I correct?
    Win7 sp1 64bit TCP Analyzer Results
    Tested on: 2020.01.29 17:25
    IP address:
    Client OS/browser: Windows 7 (Firefox 70.0)

    TCP options string: 020405b40103030801010402
    MSS: 1460
    MTU: 1500
    TCP Window: 65536 (not multiple of MSS)
    RWIN Scaling: 8 bits (2^8=256)
    Unscaled RWIN : 256
    Recommended RWINs: 64240, 128480, 256960, 513920, 1027840
    BDP limit (200ms): 2621kbps (328KBytes/s)
    BDP limit (500ms): 1049kbps (131KBytes/s)
    MTU Discovery: ON
    TTL: 112
    Timestamps: OFF
    SACKs: ON
    IP ToS: 00000000 (0)

    Also my Realtek RTL8168C(P)/8111C(P) Family PCI-E Gigabit Ethernet NIC (NDIS 6.20) limits me to 128 transmit buffer, but 512 receive buffer.
    Is there a registry tweak for this?

    Thank you for any input.

  2. #2
    Administrator Philip's Avatar
    Join Date
    May 1999
    Jacksonville, Florida
    Blog Entries
    The RWIN you set should work, just that Windows 7 and newer reports only the "current" RWIN value, not the "max" RWIN value, it varies with each packet.

    As to the MTU - the highest it can be on the internet is 1500. MSS is calculated by removing the headers from your MTU value, in this case 20 byte TCP header, and 20 byte IP headers, so typically 1500-40 = 1460. If you use ping to find your highest possible MTU/MSS, then you are using ICMP, not TCP/IP so the headers are only 28 bytes. That is why the highest non-fragmented ping you can send 1472 bytes --> 1500 byte MTU - 28 bytes of headers = 1472 MSS. For TCP/IP, this still translates to 1500 MTU - 40 bytes of headers = 1460 MSS

    I hope this helps.
    Linux is user friendly, it's just picky about its friends...
    Disclaimer: Please use caution when opening messages, my grasp on reality may have shaken loose during transmission (going on rusty memory circuits).

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