Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
NATM(4)		       FreeBSD Kernel Interfaces Manual		       NATM(4)

NAME
     natm -- Native Mode ATM protocol layer

DESCRIPTION
     The BSD ATM software comes	with a native mode ATM protocol	layer which
     provides socket level access to AAL0 and AAL5 virtual circuits.  To
     enable this protocol layer, add
	   options NATM
     to	your kernel configuration file and re-make the kernel (do not forget
     to	do ``make clean'').

NATM API
     The NATM layer uses a struct sockaddr_natm	to specify a virtual circuit:

	   struct sockaddr_natm	{
	     u_int8_t	   snatm_len;		   /* length */
	     u_int8_t	   snatm_family;	   /* AF_NATM */
	     char	   snatm_if[IFNAMSIZ];	   /* interface	name */
	     u_int16_t	   snatm_vci;		   /* vci */
	     u_int8_t	   snatm_vpi;		   /* vpi */
	   };

     To	create an AAL5 connection to a virtual circuit with VPI	0, VCI 201 one
     would use the following:

	     struct sockaddr_natm snatm;
	     int s, r;
	     s = socket(AF_NATM, SOCK_STREAM, PROTO_NATMAAL5);
				  /* note: PROTO_NATMAAL0 is AAL0 */
	     if	(s < 0)	{ perror("socket"); exit(1); }
	     bzero(&snatm, sizeof(snatm));
	     snatm.snatm_len = sizeof(snatm);
	     snatm.snatm_family	= AF_NATM;
	     sprintf(snatm.snatm_if, "en0");
	     snatm.snatm_vci = 201;
	     snatm.snatm_vpi = 0;
	     r = connect(s, (struct sockaddr *)&snatm, sizeof(snatm));
	     if	(r < 0)	{ perror("connect"); exit(1); }
	     /*	s now connected	to ATM!	*/

     The socket() call simply creates an unconnected NATM socket.  The
     connect() call associates an unconnected NATM socket with a virtual cir-
     cuit and tells the	driver to enable that virtual circuit for receiving
     data.  After the connect()	call one can read() or write() to the socket
     to	perform	ATM I/O.

Internal NATM operation
     Internally, the NATM protocol layer keeps a list of all active virtual
     circuits on the system in natm_pcbs.  This	includes circuits currently
     being used	for IP to prevent NATM and IP from clashing over virtual cir-
     cuit usage.

     When a virtual circuit is enabled for receiving data, the NATM protocol
     layer passes the address of the protocol control block down to the	driver
     as	a receive ``handle''.  When inbound data arrives, the driver passes
     the data back with	the appropriate	receive	handle.	 The NATM layer	uses
     this to avoid the overhead	of a protocol control block lookup.  This
     allows us to take advantage of the	fact that ATM has already demulti-
     plexed the	data for us.

CAVEATS
     The NATM protocol support is subject to change as the ATM protocols
     develop.  Users should not	depend on details of the current implementa-
     tion, but rather the services exported.

SEE ALSO
     en(4), fatm(4), hatm(4), natmip(4), patm(4)

AUTHORS
     Chuck Cranor of Washington	University implemented the NATM	protocol layer
     along with	the EN ATM driver in 1996 for NetBSD.

FreeBSD	9.3		       December	29, 1997		   FreeBSD 9.3

NAME | DESCRIPTION | NATM API | Internal NATM operation | CAVEATS | SEE ALSO | AUTHORS

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=natm&sektion=4&manpath=FreeBSD+8.2-RELEASE>

home | help