X.25 Nua And Svc Considerations - HP Spooler FASTP Manual

Installation and Configuration Considerations for
FASTPX25

X.25 NUA and SVC Considerations

Before you begin to configure FASTPX25, you should have a basic understanding of
how FASTPX25 handles the network user address (NUA) and switched virtual circuits
(SVCs).
When FASTPX25 prints a job on an X.25-connected printer, it attempts to establish a
virtual circuit by sending an X.25 call request packet containing a network user address
(NUA). This call, once established, is maintained until FASTPX25 is notified to CLOSE
the device by the Spooler supervisor. The CLOSE is typically issued when no more
jobs are queued for printing on the device. Keeping the call established while more
jobs are queued for printing avoids the call-setup time, which can be lengthy on some
X.25 networks.
In a typical X.25 network, the network cost is related to the maximum number of SVCs
that can be in use at any one time. In the ideal case, the number of SVCs selected
would match the maximum number of printers that must print concurrently. However, it
is often not economical to dedicate an SVC to each printer. To obtain proper utilization
of the available SVCs, using the same SVC for several Spooler devices does not work
because a long job printing on one device would block the SVC for other Spooler
devices that share it. These blocked devices might be waiting to print even though
other SVCs might be free.
To allow a smaller number of SVCs to be effectively shared between a larger number
of printers, FASTPX25 allows you to configure a pool of SVCs to be shared by several
Spooler devices. The same pool can be specified for many devices and FASTPX25
uses whichever SVC is free when a job needs to be printed. For more information
about SVC sharing, see the following subsection,
page 6-7.
The network user address (NUA) in the call request packet sent by FASTPX25 can be
configured in one of two ways.

One NUA can be configured as the default NUA for an SVC by using the X25AM
SCF interface to configure the DESTADDR attribute for the subdevice (SU) object.
The X25AM SU object is used to configure an SVC, and the DESTADDR attribute
assigns an NUA to the SVC. When an NUA is configured using the X25AM
subdevice, the same number is always called (that is, no SVC sharing is
performed).
For example:
SCF
ASSUME SU $X25A.#P2
ABORT
ALTER, DESTADDR "456172698"
START
Spooler FASTP Network Print Processes Manual — 427528-006
X.25 NUA and SVC Considerations
SVC Sharing Considerations
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