OSI/TS Configuration and Management Manual

Glossary
OSI/TS Configuration and Management Manual—424831-001
Glossary-14
Token bus.
local application. There are four session tokens; each is associated with a functional
unit:
The availability of each token depends on which functional units are used on the
connection.
(2) In DSM terms, a distinguishable unit in an SPI message. Programs place tokens in
an SPI buffer using the SSPUT or SSINIT procedures and retrieve them from the buffer
with the SSGET procedure. A token has two parts: an identifying code, or token code,
and a token value. In command and response messages, a token normally represents a
parameter to a command, an item of information in a response, or control information
for the subsystem. In event messages, a token normally represents an item of
information about an event or about the event message itself.
Token bus. The IEEE 802.4 standard for the both Data Link Layer (media access control
sublayer only) and Physical Layer of the OSI Reference Model, which defines a token-
passing bus access method for connections over LAN networks.
Transfer syntax. In the Presentation Layer, the definition of the exact bit patterns to be used
to convey specified kinds of information in a communication. Compare abstract syntax.
Transport address. See TSAP (transport service access point).
Transport classes. The ISO standard for transport protocol defines five different classes of
transport protocols to meet varying user needs for operation over different types of
networks.
Transport entity. A process in the Transport Layer that sends or receives a given TPDU.
Transport Layer. Layer 4 in the OSI Reference Model. This layer provides reliable,
transparent transfer of data between end systems and ensures that the data arrives at the
correct destination. It provides reliable data transfer independent of the underlying
Network Layer, but does, however in the CONS case, depend on the Network Layer to
provide the network connection.
Transport protocol data unit. See PDU (protocol data unit).
Transport selector. See TSEL (transport selector).
Transport service access point. See TSAP (transport service access point).
Transport service data unit. See TSDU (transport service data unit).
Transport service user. An abstract representation of all entities within a single system that
make use of the transport service.
TSAP (transport service access point). A network-unique address in the Transport Layer
through which connections are established and maintained. Also called transport
address.