OSI/FTAM Programming Reference Manual

Glossary
HP NonStop OSI/FTAM Programming Reference Manual—528611-001
Glossary-29
Transport Layer.
Transport Layer. Layer 4 in the OSI Reference Model. This layer provides reliable data
transfer.
transport selector. See TSEL (transport selector).
transport service access point. See TSAP (transport service access point).
transport service provider. See TSP (transport service provider) process.
traversal. An ordering of the nodes in a tree such that each node occurs only once, and
which is determined by an algorithm applicable to all possible trees.
tree. A connected hierarchical file structure in which each node is linked to other nodes by
directed arcs in such a way that one node has no inbound arcs, and all other nodes
have exactly one inbound arc. See also subtree.
TSAP (transport service access point). A network-unique address in the Transport Layer
through which connections are established and maintained. Also called transport
address.
TSEL (transport selector). A logical address in the Transport Layer through which
transport services are made available.
TSP (transport service provider) process. A process in the NonStop 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. See also NSP (network service provider) process. and TAPS
(Tandem application, presentation, and session) process..
UA (unstructured all data units). An access context for which data is transferred as
file-contents data elements; that is, only the data contents of the file are transferred.
See access-context parameter.; contrast with FA (flat all data units).
unconfirmed service. A subsystem service in which the initiating application sends a
request to a responding application without a response being returned to the initiating
application. Contrast with confirmed service.
unconstrained class. An ISO FTAM service class consisting of the kernel functional unit
and (optionally) any other functional unit.
universal-class number. (1) The ASN.1-specified tag for the character-string type used on
a data transfer. (2) A parameter of contents-type that specifies a code for this tag. See
also relaxation. and contents-type parameter.
unstructured file. The structure of FTAM-1 and FTAM-3 files, in which the complete file is
treated as one FADU.