Configuring and Managing Host-Based X.25 Links - Edition 5 (36939-90054)

Chapter 1 17
Introduction
X.25 Network Connections
The PAD support provided on MPE/iX systems conforms to the 1984
version of CCITT recommendations X.3 and X.29. Support is also
provided for the 1980 recommendation. Packet sizes of 128, 256, and
512 bytes are supported. Access is provided for users of asynchronous
serial devices connected to both public and private PADs.
A public PAD is a service provided by a Public Data Network
(PDN), such as TELENET or TRANSPAC. Public PADs can be used
with either a dial-up or a leased line.
A private PAD is one that is connected to a PDN as a host node having
its own X.25 network address, but behaves as a PAD when connected to
another node. Private PADs require leased lines to the network.
Hewlett-Packard provides several cluster controllers for use as private
PADs.
All devices connected via PAD must support XON/XOFF protocol and
must be configured to match the speed of the PAD and modem.
Only character mode and VPLUS applications are supported on
PAD-connected devices. There are also some aspects of the way
transmission occurs over PAD connections that cause differences in the
way certain device control operations take place. See the Asynchronous
Serial Communications Programmer’s Reference Manual for a
summary of these differences.
Figure 1-1 shows both PAD and X.25 system-to-system connections for
HP 3000 Series 900 systems employing host-based network
management.
Figure 1-1 X.25 Network Connections