Home Half-open limit fix is a program designed to change the maximum number of concurrent half-open outbound TCP connections (connection attempts) in the Windows system tcpip.sys file. Microsoft first introduced this limit in Windows XP SP2 and it is present in later versions, which purpose is to try to slow the spread of virus and malware from system to system, and also to reduce the impact of infected systems participating in DoS (Denial of Service) attacks.

Microsoft's limiter makes it impossible for Windows systems to have more than 10 concurrent half-open outbound connections; after 10, new connection attempts are put in a queue and forced to wait. Thus, the speed of connection to other PCs is limited.Therefore, the speed of connection to other computers is actually limited. This happens regardless of whether you're using DSL, ethernet or a cable broadband internet service provider.

P2P (peer-to-peer) software like µTorrent, BitComet, eMule, P2P TV, etc., are generally the programs mostly affected. Since bittorrent apps tend to use up all 10 of the half-open connections, other Internet activity—especially the loading of web pages—can become extremely slow. The delay before opening a new page can take over ten seconds: this delay occurs regardless of your Internet connection speed. Remedies this problem by increasing the maximum limit of half-open connections. For most Internet users, changing the limit to 100 will be more than sufficient.

Help remove the connection limit of TCP/IP. By morland 15 replies. Anyway I've applied that patch to XP SP3, Server 2003, Vista SP2, Server 2008 Enterprise. Windows XP only allows 10 simultaneous connections. Users can't use proxy checker or bit torrent on it. Here is a patch to break the limit. How can the answer be improved? Windows XP only allows 10 simultaneous connections. Users can't use proxy checker or bit torrent on it. Here is a patch to break the limit.