+defeats this algorithm.
+.It Dv TCP_MAXSEG
+By default, a sender- and
+.No receiver- Ns Tn TCP
+will negotiate among themselves to determine the maximum segment size
+to be used for each connection.
+The
+.Dv TCP_MAXSEG
+option allows the user to determine the result of this negotiation,
+and to reduce it if desired.
+.It Dv TCP_NOOPT
+.Tn TCP
+usually sends a number of options in each packet, corresponding to
+various
+.Tn TCP
+extensions which are provided in this implementation.
+The boolean option
+.Dv TCP_NOOPT
+is provided to disable
+.Tn TCP
+option use on a per-connection basis.
+.It Dv TCP_NOPUSH
+By convention, the
+.No sender- Ns Tn TCP
+will set the
+.Dq push
+bit, and begin transmission immediately (if permitted) at the end of
+every user call to
+.Xr write 2
+or
+.Xr writev 2 .
+When this option is set to a non-zero value,
+.Tn TCP
+will delay sending any data at all until either the socket is closed,
+or the internal send buffer is filled.
+.It Dv TCP_KEEPALIVE
+.Tn The
+.Dv TCP_KEEPALIVE
+options enable to specify the amount of time, in seconds, that the
+connection must be idle before keepalive probes (if enabled) are sent.
+The default value is specified by the
+.Tn MIB
+variable
+.Va net.inet.tcp.keepidle .
+.It Dv TCP_CONNECTIONTIMEOUT
+.Tn The
+.Dv TCP_CONNECTIONTIMEOUT
+option allows to specify the timeout, in seconds, for new, non established
+.Tn TCP
+connections. This option can be useful for both active and passive
+.Tn TCP
+connections. The default value is specified by the
+.Tn MIB
+variable
+.Va net.inet.tcp.keepinit .
+.It Dv TCP_KEEPINTVL
+When keepalive probes are enabled, this option will set the amount of time in seconds between successive keepalives sent to probe an unresponsive peer.
+.It Dv TCP_KEEPCNT
+.Tn When keepalive probes are enabled, this option will set the number of times a keepalive probe should be repeated if the peer is not responding. After this many probes, the connection will be closed.
+.It Dv TCP_SENDMOREACKS
+When a stream of
+.Tn TCP
+data packets are received, OS X uses an algorithm to reduce the number of acknowlegements by generating a
+.Tn TCP
+acknowlegement for 8 data packets instead of acknowledging every other data packet. When this socket option is enabled, the connection will always send a
+.Tn TCP
+acknowledgement for every other data packet.
+.It Dv TCP_ENABLE_ECN
+Using Explicit Congestion Notification (ECN) on
+.Tn TCP
+allows bi-directional end-to-end notification of congestion without dropping packets. Conventionally TCP/IP networks signal congestion by dropping packets. When ECN is successfully negotiated, an ECN-aware router may set a mark in the IP header instead of dropping a packet in order to signal impending congestion. The
+.Tn TCP
+receiver of the packet echoes congestion indication to the
+.Tn TCP
+sender, which reduces it's transmission rate as if it detected a dropped packet. This will avoid unnecessary retransmissions and will improve latency by saving the time required for recovering a lost packet.
+.It Dv TCP_NOTSENT_LOWAT
+The send socket buffer of a
+.Tn TCP sender has unsent and unacknowledged data. This option allows a
+.Tn TCP sender to control the amount of unsent data kept in the send socket buffer. The value of the option should be the maximum amount of unsent data in bytes. Kevent, poll and select will generate a write notification when the unsent data falls below the amount given by this option. This will allow an application to generate just-in-time fresh updates for real-time communication.
+.It Dv TCP_FASTOPEN
+The TCP listener can set this option to use TCP Fast Open feature. After
+setting this option, an
+.Xr accept 2
+may return a socket that is in SYN_RECEIVED state but is readable and writable.
+.It Dv TCP_CONNECTION_INFO
+This socket option can be used to obtain TCP connection level statistics. The
+"struct tcp_connection_info" defined in <netinet/tcp_var.h> is copied to the
+user buffer.
+.El
+.Pp
projects / apple / xnu.git / blobdiff