Introduction to Tandem X.25 Capabilities

X25AM
Tandem X.25 Features and Capabilities
2–2 065307 Tandem Computers Incorporated
X25AM line — The X25AM line is a physical entity attached to a Tandem
controller, which is capable of supporting X.25 communications. The X25AM line
is configured as a device by the system generation program (SYSGEN). While
configuring a line, you can specify basic line characteristics (subscription
parameters): timers, retries, frame size, default window size, default packet size,
default throughput class, and extended packet sequencing capability. Additional
information about configuring X25AM lines is provided in the System Generation
Manual for X25AM.
X25AM subdevice — The X25AM subdevice is a logical entity related to an
X25AM line. The logical subdevice can represent a physical object (a terminal or
computer), or it can represent some other software (an application or other
process) residing in a computer system. Each application or physical object
communicating over an X25AM line must have a subdevice defined for it.
X25AM subdevices must be added to the X25AM line(s) and their characteristics
must be defined by using the Subsystem Control Facility (SCF). The maximum
number of subdevices that can be added to a line is determined by the maximum
number of circuits (CIRCUITS modifier) specified for the line with SYSGEN. The
maximum number of circuits allowable depends upon your network subscription.
Note For C-series systems, X25AM subdevices can also be added or configured by using the Configuration
Management Interface (CMI). However, it is recommended that you use SCF, because not all features of
X25AM are available through CMI. For example, the capability to specify and retrieve the CUD is a new
feature provided with X25AM; you can specify and retrieve the CUD for a subdevice using SCF.
However, you cannot access this feature through CMI.
For D-series systems, X25AM no longer supports CMI. Information on adapting CMI Obey files to SCF
Obey files is provided in the C30.08/D10 version of the SCF Reference Manual for X25AM.
In C30 and prior releases, each X25AM line can be configured for up to 254 circuits
(254 subdevices). In D-series systems, X25AM lines can be configured for up to
511 circuits (511 subdevices). Subdevices must be configured for the following
characteristics:
Each subdevice must be configured for an X25AM protocol, indicating the
desired type of connectivity. (See “X25AM Connectivity” later in this section
for a list of X25AM protocols and specific connectivity information.)
Each subdevice must be configured as either a permanent virtual circuit (PVC)
or a switched virtual circuit (SVC).
For each PVC subdevice, a logical channel must be specified.
For each SVC subdevice, optional user facilities may be specified.
Detailed information on how to use SCF for X25AM is provided in the SCF Reference
Manual for X25AM.