10.4;tcpd (TCP daemon), revision 2.0, 91/10/16
tcpd - TCP/IP protocol server
usage:  tcpd [-a] [-b] [-d <mask>] [-f] [-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.local.

     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.

     -b          Enable directed broadcasts according to the Internet protocol
                 for gateway routers (RFC 1009). Invoke the TCP/IP server with
                 -b when you plan to run an application that relies on
                 directed broadcasts. Normally, the TCP/IP server broadcasts
                 messages sent by applications in its own locally connected
                 network.  With directed broadcasts, the TCP/IP server
                 delivers broadcasts to its network (or a subnet within its
                 network) that have been sent by applications in other
                 Internet networks.

     -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
          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

     -f   Disable the forwarding of IP packets whose destination address does
          not belong to this host. This functionality applies only to hosts
          that are connected to more than one IP network or subnet. By
          default, IP packet forwarding is enabled, allowing the host to
          function as a router.

     -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.

SEE ALSO
     netstat, ping;
     Configuring and Managing TCP/IP.