.\"	$OpenBSD: ns.4,v 1.9 2000/12/21 21:01:17 aaron Exp $
.\"	$NetBSD: ns.4,v 1.3 1994/11/30 16:22:26 jtc Exp $
.\"
.\" Copyright (c) 1985, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
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.\"    must display the following acknowledgement:
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.\"     @(#)ns.4	8.2 (Berkeley) 11/30/93
.\"
.Dd November 30, 1993
.Dt NS 4
.Os
.Sh NAME
.Nm ns
.Nd Xerox Network Systems(tm) protocol family
.Sh SYNOPSIS
.Nm option NS
.Nm option NSIP
.Nm pseudo-device ns
.Sh DESCRIPTION
The
.Tn NS
protocol family is a collection of protocols
layered atop the
.Em Internet  Datagram  Protocol
.Pq Tn IDP
transport layer, and using the Xerox
.Tn NS
address formats.
The
.Tn NS
family provides protocol support for the
.Dv SOCK_STREAM ,
.Dv SOCK_DGRAM ,
.Dv SOCK_SEQPACKET ,
and
.Dv SOCK_RAW
socket types; the
.Dv SOCK_RAW
interface is a debugging tool, allowing you to trace all packets
entering, (or with toggling kernel variable, additionally leaving) the local
host.
.Sh ADDRESSING
.Tn NS
addresses are 12 byte quantities, consisting of a
4 byte Network number, a 6 byte Host number and a 2 byte port number,
all stored in network standard format.
(on the
.Tn VAX
these are word and byte reversed; on the
.Tn SUN
they are not
reversed).  The include file
.Aq Pa netns/ns.h
defines the
.Tn NS
address as a structure containing unions (for quicker
comparisons).
.Pp
Sockets in the Internet protocol family use the following
addressing structure:
.Bd -literal -offset indent
struct sockaddr_ns {
	u_char		sns_len;
	u_char		sns_family;
	struct ns_addr	sns_addr;
	char		sns_zero[2];
};
.Ed
.Pp
where an
.Ar ns_addr
is composed as follows:
.Bd -literal -offset indent
union ns_host {
	u_char		c_host[6];
	u_short		s_host[3];
};

union ns_net {
	u_char		c_net[4];
	u_short		s_net[2];
};

struct ns_addr {
	union ns_net	x_net;
	union ns_host	x_host;
	u_short	x_port;
};
.Ed
.Pp
Sockets may be created with an address of all zeroes to effect
.Dq wildcard
matching on incoming messages.
The local port address specified in a
.Xr bind 2
call is restricted to be greater than
.Dv NSPORT_RESERVED
(=3000, in
.Aq Pa netns/ns.h )
unless the creating process is running
as the superuser, providing a space of protected port numbers.
.Sh PROTOCOLS
The
.Tn NS
protocol family supported by the operating system
is comprised of
the Internet Datagram Protocol
.Pq Tn IDP
.Xr idp 4 ,
Error Protocol (available through
.Tn IDP ) ,
and
Sequenced Packet Protocol
.Pq Tn SPP
.Xr spp 4 .
.Pp
.Tn SPP
is used to support the
.Dv SOCK_STREAM
and
.Dv SOCK_SEQPACKET
abstraction,
while
.Tn IDP
is used to support the
.Dv SOCK_DGRAM
abstraction.
The Error protocol is responded to by the kernel
to handle and report errors in protocol processing;
it is, however,
only accessible to user programs through heroic actions.
.Sh SEE ALSO
.Xr byteorder 3 ,
.Xr gethostbyname 3 ,
.Xr getnetent 3 ,
.Xr getprotoent 3 ,
.Xr getservent 3 ,
.Xr intro 3 ,
.Xr ns 3 ,
.Xr idp 4 ,
.Xr netintro 4 ,
.Xr nsip 4 ,
.Xr spp 4
.Rs
.%T "Internet Transport Protocols"
.%R Xerox Corporation document XSIS
.%N 028112
.Re
.Rs
.%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"
.Re
.Sh HISTORY
The
.Nm
protocol family
appeared in
.Bx 4.3 .