HP X.25/9000 Programmer's Guide

126 AppendixA
X.25 Packet Formats
INTERRUPT CONFIRMATION Packet
INTERRUPT CONFIRMATION Packet
This packet is transmitted automatically by the X.25/800 subsystem
when an INTERRUPT packet is received. The X.25/800 subsystem
transmits this packet when the application process reads the interrupt
data (issues a recv(MSG_OOB) system call).
Figure A-6 INTERRUPT CONFIRMATION packet
Access to the fields in the INTERRUPT CONFIRMATION packet is
described below:
General Format
Identifier
Indicates the packet sequence count (modulo 8 or modulo 128). This field
cannot be read or written by an X.25 application.
Logical Channel
Identifier
Contains the logical channel identifier. This field is controlled by the
subsystem and can be read with an ioctl(X25_RD_LCI) call after the
connection has been established.
Packet Type
Identifier
Indicates the kind of packet. X.25/800 automatically transmits this
packet in response to an INTERRUPT packet. Transmission cannot be
controlled by the application.
To read this field on an incoming packet:
In blocking mode, the send(MSG_OOB) system call blocks until
confirmation is received. In nonblocking mode, recv(MSG_OOB) returns a
buffer the second byte of which ( buf[1] ) indicates that an INTERRUPT
CONFIRMATION packet has arrived ( OOB_VC_INTERRUPT_CONF ).
To write this field on an outgoing packet:
The X.25/800 subsystem transmits an INTERRUPT CONFIRMATION
packet when the corresponding INTERRUPT packet's interrupt user
Logical Channel Identifier
87654321
1
2
3
Bits
Packet Type Identifier
General Format Identifier
Octets
36960-90061.bk Page 126 Friday, November 10, 2000 3:42 PM