X25AM Programming Manual

Introduction
X25AM Programming Manual—527201-001
1-16
Per Call Facilities
Nonstandard Default Window Sizes
X25AM can be configured for a default window size of 1 to 7 for modulo 8 or of 1 to 15
for modulo 128. X25AM subdevices can be configured to negotiate window size on a
per call basis. Refer to Per Call Facilities on page 1-16.
Per Call Facilities
Facilities are optional network features that are part of the network subscription. This
subsection describes the facilities supported by X25AM. X25AM includes the facilities
in a Call Request packet that is sent in response to a CONTROL 17 issued by the
application. To use any of these facilities the network subscription must allow their use.
While these parameters usually are set during system configuration using SCF
commands, you may want to know about the various parameters and possible settings
if you write or support an X25AM application program. Many of them can also be
altered by an application program.
The remainder of this section summarizes each parameter and notes recommended
settings, where applicable.
Closed User Group (CUG) Facility
X25AM ignores the facility in an Incoming Call packet.
In a Call Request packet, the CUG ID and CUG type can be specified as a line and/or
subdevice attribute. If both the line and the subdevice attribute are specified, the
subdevice attribute is used. A dynamic value can be specified using SETPARAM 7 for
CUG and SETPARAM 33 for CUGTYPE.
Reverse Charging
X25AM accepts an Incoming Call packet with reverse charging requested and assigns
it to a subdevice that is configured to accept reverse charges. If there is no such
subdevice, the call is cleared and diagnostic code 129 is returned.
X25AM requests reverse charging in an outgoing Call Request packet when the
subdevice that issues the call is configured to request reverse charging.
Packet-Size Negotiation
X25AM always accepts an Incoming Call packet that indicates packet-size negotiation
as long as the requested packet size is less than or equal to the system generation
program packet size modifier (PACKETSIZE).
If the Incoming Call is less than PACKETSIZE, the call can be assigned only to
subdevices that are configured to negotiate packet size. If there is no such subdevice,
the call is cleared. If it is equal to PACKETSIZE, the call can be assigned to any free
subdevice. If it is greater than PACKETSIZE, the call is cleared.