TCPD(8)                              BSD                               TCPD(8)



NAME
     tcpd - TCP/IP protocol server

SYNOPSIS
     /etc/tcpd [ -a ] [ -d<mask> ] [ -p<time> ] [ -t<ipttl> ] [ -w<window> ]

DESCRIPTION
     Invoking tcpd, the TCP/IP protocol server or daemon, enables a node's
     TCP/IP socket-call interface and initializes several internal tables
     required for operation of the protocols. The tcpd daemon must be run on
     every node that uses TCP/IP.  Normally, tcpd is invoked by the node's
     startup file, /etc/rc.

     Options available with this command allow you to define certain
     parameters of the protocols.

OPTIONS
     -a          Suppress delayed packet acknowledgements (ACKs), the default
                 condition.  Delayed ACKs is a performance optimization
                 feature for TCP which allows a receiver to delay until 33% of
                 the maximum window size offered can be uncovered (but in no
                 case to wait longer than 0.25 seconds) before it acknowledges
                 received packets.

     -p<time>    Set gateway ping interval in seconds. The value must be
                 expressed in hexadecimal and can range from 0 to A.  Default
                 value is 4 seconds.  Setting the interval to 0 inhibits
                 pinging.  TCP issues an ICMP Echo Request (ping) to local
                 hosts and gateways at the specified interval to verify their
                 continued operation. Any gateway that fails to respond after
                 three tries is moved to the end of the node's routing table.

     -t<ipttl>   Set the IP parameter, packet maximum time to live.  The value
                 must be expressed in hexadecimal and can range from 1 to FF.
                 Default value is 1E.

     -w<window>  Set the receive window size (a TCP flow control parameter) in
                 octets. The value must be expressed in HEX and can range from
                 1 to 239C.  Default value is 239C.

     -d<mask>    Display debugging information as defined by the 16-bit mask.
                 See the table below for a description of the debug
                 information that can be requested.  Add bit values to request
                 several types of information.

          {_Bit Value_}          {_Debug Information_}

          0001 (default)         General information
          0002                   IP level information
          0004                   ARP information
          0008                   TCP information
          0010                   Data in TCP packets
          0020                   UDP information
          0200                   Broadcasts
          1000                   TCP finite state machine information
          2000                   Device level information
          4000                   Additional detail at any level
          foff                   All available debug information
                                  except broadcasts

SEE ALSO

     netstat(1), ping(8);
     Configuring and Managing TCP/IP.