OSI/TS Configuration and Management Manual

Glossary
OSI/TS Configuration and Management Manual—424831-001
Glossary-11
Service primitive.
these operations are implemented. A service relates to an interface between two layers,
with the lower layer being the service provider and the upper layer being the service
user.
Service primitive. An abstract, implementation-independent interaction between a service
user and a service provider. Service primitives describe the sequences of events
between adjacent layers that occur through the service access point (SAP). There are
four types of service primitives: Confirm primitive.
, Indication primitive., Request
primitive., or Response primitive.
Session. (1) In the context of OSI data transmission, the period during which two entities
can exchange data.
(2) In the context of a management application, the period during which an application
can issue commands to a subsystem.
Session Layer. Layer 5 in the OSI Reference Model. It allows the setup and termination of
and controls communication sessions between nodes on the network.
Session selector. See SSEL (session selector).
Simple token. In DSM programmatic interfaces, a token consisting of a token code and a
value that is either a single elementary field, such as an integer or a character string, or a
fixed (nonextensible) structure.
SNDCF (subnetwork dependent convergence function). A function in the Network Layer
that allows the OSI internet protocol (which usually operates over LANs) to operate
over other protocols, such as X.25.
SNPA (subnetwork point of attachment). A real, physical address, identifying the point of
attachment to a subnetwork. An OSI end system can be connected to one subnetwork or
to a number of different subnetworks:
SPI (Subsystem Programmatic Interface). In DSM, a set of procedures and associated
definition files used to define common message-based programmatic interfaces for
communication between requesters and servers—for instance, in a management
application. SPI includes procedures to build and decode specially formatted messages;
definition files in Pascal, TAL, C, COBOL85, and TACL for inclusion in programs,
macros, and routines using the SPI procedures; and definition files in DDL for
programmers writing their own subsystems.
SSAP (session service access point). A network-unique address in the Session Layer
through which connections are established and maintained.
SSEL (session selector). A logical address in the Session Layer through which session
services are made available. A single SSEL can service one or more connections
simultaneously.
SSID. See Subsystem ID (SSID).