OSI/TS Management Programming Manual

Glossary
Glossary-24 056786 Tandem Computers Incorporated
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.
Transport selector. See TSEL.
Transport service access point. See TSAP.
Transport service data unit. See TSDU.
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.
TSDU (transport service data unit). A unit of data used by transport peer entities to
transfer data.
TSEL (transport selector). A logical address in the Transport Layer through which
transport services are made available. A single TSEL can service one or more
connections simultaneously.
TSP (transport service provider) process. A process in the OSI end system that performs
service and protocol functions for the Transport Layer and for the internet protocol
(IP) of the Network Layer. TSP processes are provided by the underlying OSI/TS
subsystem.
Typed data. Data sent over a Session Layer connection regardless of the location of the
data token. Under some circumstances, protocol data units from the Session Layer
and the Application Layer may need to be sent as typed data. The typed data
functional unit must have been negotiated for the connection.
Unconditional token. A token that is always present in a particular event message.
Compare conditional token or Tandem internal token.
Viewpoint console application. An extensible interactive application for operators,
provided as part of DSM. Viewpoint allows a system or a network to be controlled
from a single terminal. It includes several block-mode display screens for event
messages, a block-mode display for system or network status, a conversational TACL
screen, and a facility called Define Process to maintain sessions with multiple
subsystems at the same time.
Wait mode. In Guardian 90, the mode in which the called procedure waits for the
completion of an I/O operation and then returns a condition code to the caller.
Compare nowait mode.