X25AM Programming Manual

Glossary
X25AM Programming Manual—527201-001
Glossary-8
SCF.
SCF. Subsystem Control Facility. A subsystem used for issuing configuration and
information requests between the user and some communications subsystems.
SIT. System-image tape. Contains an operating system ready to be loaded onto an
NonStop system.
SU. Name of an object used by SCF to refer to a subdevice.
subdevice. Logical component of X25AM, providing access to a circuit.
subscriber access link. Communications link between the local device or system and the
network.
Subsystem Control Facility. See SCF.
switched line. Line configuration for circuit-switched networks such as a public telephone
network. The physical configuration may vary for each usage as a message is routed
through switching stations.
switched virtual circuit (SVC). Association between two entities for packet exchange. Set
up by a call it is terminated after each call. A call requires set up before data transfer
and clearing after data transfer.
SVC. See switched virtual circuit (SVC).
SYSGEN. Program that generates a system-image file. The SYSGEN program is usually
invoked by INSTALL.
TERMPROCESS. A NonStop Kernel-specific process used to connect to remote terminals,
also denotes a communications subsystem. ATP6100, which has increased
functionality, is the process HP recommends over TERMPROCESS.
timeout. Time interval during which a specified action must occur.
throughput. Amount of data traffic going through the network within a given time period.
Expressed in bits per second (bps).
transit delay selection or indication. Optional network facility for requesting the
maximum acceptable delay in the network in the call request packet. The network
responds in a call connected packet with the value or a lower acceptable value.
UA. Unnumbered acknowledge. Link-level frame used for call connection.
User data. Data field contained in data packets. See also call user data (CUD).
virtual circuit. Facilities provided by a packet-switching network that give the appearance
to the user of an actual connection.
window size. Maximum number of packets or frames that can be transmitted without being
acknowledged.