ISO(4) MachTen Programmer’s Manual ISO(4)

NAME
iso - ISO protocol family

SYNOPSIS
#include <sys/types.h>
#include <netiso/iso.h>

DESCRIPTION
The ISO protocol family is a collection of protocols that uses the ISO
address format. The ISO family provides protocol support for the
SOCK_SEQPACKET abstraction through the TP protocol (ISO 8073), for the
SOCK_DGRAM abstraction through the connectionless transport protocol (ISO
8602), and for the SOCK_RAW abstraction by providing direct access (for
debugging) to the CLNP (ISO 8473) network layer protocol.

ADDRESSING
ISO addresses are based upon ISO 8348/AD2, Addendum to the Network
Service Definition Covering Network Layer Addressing.

Sockets bound to the OSI protocol family use the following address struc-
ture:

struct iso_addr {
u_char isoa_len; /* length, not including this byte */
char isoa_genaddr[20]; /* general opaque address */
};

struct sockaddr_iso {
u_char siso_len; /* size of this sockaddr */
u_char siso_family; /* addressing domain, AF_ISO */
u_char siso_plen; /* presentation selector length */
u_char siso_slen; /* session selector length */
u_char siso_tlen; /* transport selector length */
struct iso_addr siso_addr; /* network address */
u_char siso_pad[6]; /* space for gosip v2 SELs */
};
#define siso_nlen siso_addr.isoa_len
#define siso_data siso_addr.isoa_genaddr

The fields of this structure are:

siso_len:
Length of the entire address structure, in bytes, which may grow
to be longer than the 32 bytes shown above.

siso_family:
Identifies the domain: AF_ISO.

siso_tlen:
Length of the transport selector.

siso_slen:
Length of the session selector. This is not currently supported
by the kernel and is provided as a convenience for user level
programs.

siso_plen:
Length of the presentation selector. This is not currently sup-
ported by the kernel and is provided as a convenience for user
level programs.

siso_addr:
The network part of the address, described below.

TRANSPORT ADDRESSING
An ISO transport address is similar to an Internet address in that it
contains a network-address portion and a portion that the transport layer
uses to multiplex its services among clients. In the Internet domain,
this portion of the address is called a port. In the ISO domain, this is
called a transport selector (also known at one time as a transport
suffix). While ports are always 16 bits, transport selectors may be of
(almost) arbitrary size.

Since the C language does not provide convenient variable length struc-
tures, we have separated the selector lengths from the data themselves.
The network address and various selectors are stored contiguously, with
the network address first, then the transport selector, and so on. Thus,
if you had a nework address of less then 20 bytes, the transport selector
would encroach on space normally reserved for the network address.

NETWORK ADDRESSING.
ISO network addresses are limited to 20 bytes in length. ISO network ad-
dresses can take any format.

PROTOCOLS
The ARGO 1.0 implementation of the ISO protocol family comprises the Con-
nectionless-Mode Network Protocol (CLNP), and the Transport Protocol
(TP), classes 4 and 0, and X.25. TP is used to support the SOCK_SEQPACKET
abstraction. A raw interface to CLNP is available by creating an ISO
socket of type SOCK_RAW. This is used for CLNP debugging only.