HP X.25/9000 Programmer's Guide

Chapter 6 89

Extended Features

Using Facilities

X.25 permits the negotiation of facilities that can be implemented when

calls are connected or cleared.

Facilities are speciﬁed in the following packet types:

• CALL REQUEST/CALL INDICATION,

• CALL ACCEPTED/CALL CONNECTED,

• CLEAR REQUEST/CLEAR INDICATION,

• CLEAR CONFIRMATION.

X.25 includes the default facilities settings speciﬁed at conﬁguration

time for CALL REQUEST packets. The packet’s facilities ﬁeld is read

and written with the ioctl(X25_RD_FACILITIES) and

ioctl(X25_WR_FACILITIES) calls, respectively.

Consult your system administrator for X.25 conﬁguration constraints.

Consult the documentation supplied by your network provider for more

information about the facilities permitted on the network.

The ioctl(X25_RD_FACILITIES) Call

The ioctl(X25_RD_FACILITIES) call returns the contents of the

facilities ﬁeld contained in the last inbound packet containing a facilities

ﬁeld. New inbound facilities data overwrites preceding data. Inbound

facilities data can only be read once, and storage resources are freed

after the data is read. If the process tries to read inbound facilities data

that has already been read, or if no facilities data is available, the

ioctl() call returns a data length of 0.

The ioctl(X25_RD_FACILITIES) call only reads facilities data from

inbound packets. It can, however, read facilities data from a CLEAR

INDICATION packet (useful with fast select described below).

A process cannot use the ioctl(X25_RD_FACILITIES) call to read

facilities data that it has just written with the

ioctl(X25_WR_FACILITIES) call.

facilities may be added, deleted, rearranged or modiﬁed by the X.25

subsystem, the packet switching equipment, or the network provider.

36960-90061.bk Page 89 Friday, November 10, 2000 3:42 PM