No more than 10 concurrent connections to a remote computer

26 October 2005 by Snakefoot | Comment » | Trackback Off
Microsoft have created several limitations in the Workstation, Professional and Home edition of Windows, so they are crippled compared to the server-edition. This is to encourage users to buy the more expensive server license.

When sharing a file/printer, then there is a limit for how many users that can access the shared resource from the Local Area Network (LAN) simultaneously. The actual inbound SMB connection limit (Prof=10)/(Home=5) can be seen by running this command:

net config server

If a user tries to access a network share on a computer where the limit is reached, then it will give this error:
No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept.
If having problems with users reaching the limit and getting the above message, then one can consider the following solutions:
  • Upgrade to a Windows Server license. If having upgraded from a Windows NT4 Workstation to a Windows NT4 Server, then update this registry key:

    [HKEY_LOCAL_MACHINE \System \CurrentControlSet \Services \LanManServer \Parameters]
    Users = 0xffffff

    More Info MS KB Q122925
    More Info MS KB Q179483

  • Use Linux with Samba (Some external hard disk storage devices include a small linux distribution with Samba installed).
  • Use several computers to share the files/printers
  • Decrease the timeout period for user connections, to close unused connections faster (Default 15 minutes):

    net config server /autodisconnect:1

    More Info MS KB Q122920
    More Info MS KB Q138365
    More Info MS KB Q314882

  • Restrict anonymous access to file and printer shares (To avoid wasting sessions on anonymous access). More info MS KB Q328459
  • Increase the limit of concurrent incoming SMB commands (different from concurrent SMB sessions), so long-term SMB commands (Like the Change Notification request) will not block for new SMB commands without having reached the max number of inbound SMB sessions.

    Update the following DWORD registry settings to optimize the network performance of Windows XP:

    [HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \Lanmanserver \Parameters]
    MaxMpxCt = 50 (Default = 10 commands)
    MaxWorkItems = 256 (Default = 64)
    Size = 2 (Default = 1)

    More Info MS KB926646 (Hotfix required for these settings)

  • Don't use persistent connections like mapped network drives to the remote computer.
  • Use a different protocol than Microsoft Network, to share your files (FTP/WebDAV/P2P)
Related Increase the max limit for concurrent TCP connections

Updated: 23 September 2007

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