Configuring and Managing Host-Based X.25 Links - Edition 6 (36939-90057)

Introduction
Host-Based Network Connections
Chapter 1
18
CAUTION The DTC MUST be defined as being managed by one and only one management
platform. If a configuration for a DTC with the same LAN Station address is configured
on more than one management platform, it is a race condition as to which platform will
actually respond and download the DTC when the DTC is powered on. Usage of the
management features such as reset on the other platform may have unpredictable
affects on the DTC’s operations.
The procedures for defining a DTC as a managed or non-managed DTC are provided in
Chapter 3, “Configuring DTCs Step-by-Step,” of this manual.
X.25 System-to-System Connections
Host-based X.25 system-to-system connections are supported through the DTC/X.25 iX
Network Link. This NS 3000/iX link makes it possible for you to connect a HP 3000
Series 900 system to a public or private X.25 packet switched network (PSN).
The DTC/X.25 iX Network Link requires that you have at least one DTC/X.25 Network
Access card installed in a DTC. You must also purchase and install the X.25 iX System
Access software on the system.
Device Connections Via PAD
PAD support makes it possible for asynchronous serial devices, such as terminals and
serial printers, to be connected to the system through an X.25 network. Serial devices
are connected to a PAD, or Packet Assembler/Disassembler. A PAD converts
asynchronous character streams into packets that can be transmitted over a packet
switched network. PAD packets follow the CCITT X.25 protocol recommendations.
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.