INET(7P)                                                 INET(7P)



     NAME
          inet - Internet protocol family

     SYNOPSIS
          #include <sys/types.h>
          #include <netinet/in.h>

     DESCRIPTION
          The Internet protocol family is a collection of protocols
          layered atop the Internet Protocol (IP) transport layer, and
          utilizing the Internet address format.  The Internet family
          provides protocol support for the SOCK_STREAM, SOCK_DGRAM,
          and SOCK_RAW socket types; the SOCK_RAW interface provides
          access to the IP protocol.

     ADDRESSING
          Internet addresses are four byte quantities, stored in
          network standard format.  The include file <netinet/in.h>
          defines this address as a discriminated union.

          Sockets bound to the Internet protocol family utilize the
          following addressing structure,

          struct sockaddr_in {
                 short     sin_family;
                 u_short   sin_port;
                 struct    in_addr sin_addr;
                 char      sin_zero[8];
          };

          Sockets may be created with the local address INADDR_ANY to
          effect "wildcard" matching on incoming messages. The address
          in a connect(2) call may be given as INADDR_ANY to mean
          ``this host.''  The distinguished address INADDR_BROADCAST
          is allowed as a shorthand for the broadcast address on the
          primary network if the first network configured supports
          broadcast.

     PROTOCOLS
          The Internet protocol family is comprised of the IP
          transport protocol, Internet Control Message Protocol
          (ICMP), Transmission Control Protocol (TCP), and User
          Datagram Protocol (UDP).  TCP is used to support the
          SOCK_STREAM abstraction while UDP is used to support the
          SOCK_DGRAM abstraction.  A raw interface to IP is available
          by creating an Internet socket of type SOCK_RAW.  The ICMP
          message protocol is accessible from a raw socket.

          The 32-bit Internet address contains both network and host
          parts.  It is frequency-encoded; the most-significant bit is
          clear in Class A addresses, in which the high-order 8 bits
          are the network number.



     Page 1                                        (last mod. 8/20/87)

     INET(7P)                                                 INET(7P)



          Class B addresses use the high-order 16 bits as the network
          field, and Class C addresses have a 24-bit network part.
          Sites with a cluster of local networks and a connection to
          the DARPA Internet may chose to use a single network number
          for the cluster; this is done by using subnet addressing.
          The local (host) portion of the address is further
          subdivided into subnet and host parts.  Within a subnet,
          each subnet appears to be an individual network; externally,
          the entire cluster appears to be a single, uniform network
          requiring only a single routing entry.  Subnet addressing is
          enabled and examined by the following ioctl(2) commands on a
          datagram socket in the Internet domain; they have the same
          form as the SIOCIFADDR command.

          SIOCSIFNETMASK      Set interface network mask.  The network
                              mask defines the network part of the
                              address; if it contains more of the
                              address than the address type would
                              indicate, then subnets are in use.

          SIOCGIFNETMASK      Get interface network mask.

     SEE ALSO
          ioctl(2), socket(2), tcp(7P), udp(7P), ip(7P)

          An Introductory 4.3BSD Interprocess Communication Tutorial
          (PS1:7).

          An Advanced 4.3BSD Interprocess Communication Tutorial
          (PS1:8).

     CAVEAT
          The Internet protocol support is subject to change as the
          Internet protocols develop.  Users should not depend on
          details of the current implementation, but rather the
          services exported.

     ORIGIN
          4.3 BSD
















     Page 2                                        (last mod. 8/20/87)