WINDOWS AFD SOCKET BUFFER SIZE WINDOWS 7
Windows 7 (one of the hosts is Windows 7 Professional, Version 6.
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The problem observed in the following OS versions: (which is what we are looking for - we want the buffer size that we specify to be used and seen on the TCP-SYN.) According to this document, if we set an SO_RCVBUF for our socket then receive window auto-tuning will be disabled: (VS.85).aspx Note that in my application the SIO_SET_COMPATABILITY_MODE is not used / specified. Setting each of GlobalMaxTcpWindowSize, TcpWindowSize and the AFD buffer sizes With respect to 3., I have tried the following without success: Some Winsock IOCTLs require more explanation than this. EXE Due to Incorrect Buffer Size Q154094 Using Iomega ATAPI Zip Drives with Windows NT Q154162 Memory Leak in Perfmon.exe Occurs Monitoring WINS Counters. DefaultReceiveWindow - The number of receive bytes that AFD buffers on a connection before imposing flow control.
WINDOWS AFD SOCKET BUFFER SIZE DRIVER
AFD Registry Parameters Afd.sys is the kernel-mode driver that is used to support Windows Sockets applications. Use the WSAIoctl or WSPIoctl function to issue a Winsock IOCTL to control the mode of a socket, the transport protocol, or the communications subsystem. The AFD key is not in your registry by default, it must be added manually or with Cablenut. Is there a fix (or is it my mis-understanding of something?)ģ. This section describes Winsock Socket input/output controls (IOCTLs) for various editions of Windows operating systems.
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Is this a known behaviour with the new TCP/IP stack from Vista?Ģ. OnĪ broken host, what we see is as follows, the point being that the TCP windows scale seen on the TCP-SYN packet is stuck on 2:ġ. To be clear, these hosts initially behave as expected (as described above), but then somehow reach a broken state and are stuck there. The per-interface TcpWindowSize registry value. This option specifies the total per-socket buffer space reserved for receive operations. However, it appears that it is somehow possible to get a Win7 or Vista host into a state where this behaviour breaks. The default receive window size that TCP advertises in Windows Server 2003 depends on the following, in order of precedence: The value for the SORCVBUF Windows Sockets option for the connection.
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Requested buf sz | TCP-RWIN | TCP-WINDOW SCALE Here is the kind of behaviour that I expect to see: That corresponds well with the that was set. Setsockopt(, SOL_SOCKET, SO_RCVBUF,, )įor a variety of values for, when I do a packet capture and look at the TCP SYN (or TCP SYN_ACK) packet that is produced on the wire when the socket is connected, I nearly always see a value for the advertised TCP receive window size In my application, the Winsock setsockopt function is used to set the receive buffer size for the TCP socket as follows: I have a problem with Winsock's ability to set send and receive buffer sizes on Windows 7 and Vista.