Nagle's algorithm: Difference between revisions

Revision as of 14:52, 18 December 2020

Revision as of 14:53, 18 December 2020

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=== Disabling either Nagle or delayed ACK ===

TCP implementations usually provide applications with an interface to disable the Nagle algorithm. This is typically called the <code>TCP_NODELAY</code> option. On Microsoft Windows the <code>TcpNoDelay</code> registry switch decides the default. <code>TCP_NODELAY</code> is present since the TCP/IP stack in 4.2BSD of 19931983, a stack with many descendents.<ref>{{man|4|tcp|FreeBSD}}</ref>

The interface for disabling delayed ACK is not consistent among systems. The {{code|TCP_QUICKACK}} flag is available on Linux since 2001 (2.4.4) and potentially on Windows, where the official interface is {{code|SIO_TCP_SET_ACK_FREQUENCY}}.<ref>{{cite web |title=sockets - C++ Disable Delayed Ack on Windows |url=https://stackoverflow.com/a/55035021 |website=Stack Overflow}}</ref> Setting <code>TcpAckFrequency</code> to 1 in the Windows registry turns of delayed ACK by default. A related undocumented value, <code>TcpAckFrequency</code>, controls the max time-to-delay for ACKs. It can be set to 1 to disable delayed ACKS as well.<ref>{{cite web |url=https://support.microsoft.com/en-us/help/328890/new-registry-entry-for-controlling-the-tcp-acknowledgment-ack-behavior |title=New registry entry for controlling the TCP Acknowledgment (ACK) behavior in Windows XP and in Windows Server 2003}}</ref>