Envoy ACP/XF Application Programming Manual

Glossary
EnvoyACP/XF Application Programming Manual–132179
Glossary-5
ServerNet WAN concentrator
ServerNet WAN concentrator. A six-port communications line concentrator for the
Himalaya S-Series. It replaces all of the earlier WAN controllers, such as the 3604,
3605, 3650, and the 6100 communications controllers.
SCF. Subsystem Control Facility. A Tandem product that is used to configure, control, and
collect information about Tandem data communications subsystems. SCF can be used to
dynamically configure and manage the EnvoyACP/XF subsystems as well as to
configure the WAN subsystem.
S-frame. See supervisory frame.
SNRM. Set Normal Response Mode. In ADCCP-NRM and SDLC, the unnumbered frame
sent by the primary station to the secondary station to establish the data link.
strapped. A wire or clip that creates a short between two pins.
supervisor. The controlling station in a centralized multipoint data link.
supervisory frame. A frame format used to convey READY or BUSY status or to request
retransmission when an error is detected.
SUT. Site update tape. Distribution tape for updated versions of Tandem-supplied software.
switched line. A line configuration for circuit-switched networks such as a public telephone
network.
synchronous. Describes a general class of data communications that includes ADCCP,
SDLC, and HDLC protocols. It is the opposite of asynchronous communications.
“Synchronous” means that there is a clock signal, separate from the data signal, that is
used to synchronize the receive circuits.
Tandem NonStop Kernel. The operating system for Tandem NonStop systems. The
operating system does not include any application program interfaces.
tributary. One of multiple stations controlled by a single, centralized supervisor station in a
multipoint data link.
U-frame. See unnumbered frame.
unnumbered frame. A frame format used to pass data-link management commands and
responses between the primary and the secondary stations.
V.25 bis. CCITT recommendation for setting up a data connection on the general switched
telephone network, using a serial modem with automatic calling capability.
window. The window size indicates the maximum number of I-frames that can be sent
without acknowledgment. The window size may be less than or equal to the modulo
size, but may never exceed the modulo.