RWIN + Slow Torrent Dload Speed!

By radicalgel
Mar 12, 2008
  1. Hey guys,

    I recently downloaded TCP optimizer and I must say its a great little tool. I have a 512kbps broadband PPPoE DSL internet connection. The problem I am facing is as follows. TCP analyzer advised me to increase the RWIN from the win XP default of 17424 to 63888. So I used TCP Optimizer to do this and after restarting my computer I noticed that my browsing was quicker, http downloads were quicker and youtube videos were streaming flawlessly with no buffering at all. Before I used TCP optimizer youtube video constantly buffered and this was really annoying. After seeing all these improvements I was really thrilled until I noticed that my torrent download speeds (In µTorrent) had greatly reduced. I normally get between 50 and 60 kBps with the window default RWIN but was now barely getting 40 kBps. I then reverted back to the windows XP default settings and torrent dload speeds were back up to normal. Can someone please help me out here as this is a real catch 22 situation. Thanks!!!

    TCP Analyzer Results:
    « TCP Analyzer Results »
    Tested on: 03.12.2008 06:04
    IP address:

    TCP options string: 020405ac
    MSS: 1452
    MTU: 1492
    TCP Window: 17424 (multiple of MSS)
    RWIN Scaling: 0
    Unscaled RWIN : 17424
    Reccomended RWINs: 63888, 127776, 255552, 511104
    BDP limit (200ms): 697kbps (87KBytes/s)
    BDP limit (500ms): 279kbps (35KBytes/s)
    MTU Discovery: ON
    TTL: 111
    Timestamps: OFF
    SACKs: OFF
    IP ToS: 00000000 (0)
  2. jobeard

    jobeard TS Ambassador Posts: 9,158   +599

    increasing the window size will reduce the number of concurrent connections that can be made.
    this impacts torrent streams as you have seen :wave:

    I would suggest reverting RWIN, set SackOpts on, and enable RWIN Scaling
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