DCP Series Telcon Message Manual - Public Support Login - Unisys

Glossary
TPCDATA
The handler for PC or U Series systems running DCA TSTN over X.25 software. This
procedure is in X.25 PSCS element PDNNXA and provides an interface between the X.25
packet-level porotocl and TSTN.
Transmission Control Protocol (TCP)
A commonly used Internet protocol that provides end-to-end reliability control for
protocols residing in the process/application layer of the OSI Reference Model. TCP is a
connection-oriented (virtual circuit) data transport protocol. It verifies the integrity of
data received from the network before passing it to the process/application layer. It
interprets error messages returned by lower layer protocols or by the TCP entity on the
peer end system and executes appropriate error recovery procedures. TCP isolates
process/application layer protocols from the characteristics of lower layer protocols.
Transmission Control Protocol/Internet Protocol (TCP/IP)
A set of protocols developed to connect different kinds of networks and computers. The
most common implementation of TCP/IP is UNIX systems, which use TCP/IP protocols to
communicate over an IEEE LAN. TCP/IP protocols are based on a four-layer architecture
model, as opposed to the OSI seven-layer model. The four layers in the TCP/IP model are:
process/application (layer 4), host-to-host (layer 3), internet (layer 2), and network access
(layer 1). The main differences between the TCP/IP model and the OSI model are the
location of reliability control (error detection and recovery) within the protocol hierarchy
and the application system structure defined by each model. TCP/IP is required for the
Defense Data Network (DDN).
TSM
TSTN
TTYLPH
TTYVTR
U
UDLCRS
UDM
See terminal session manager.
See Termination System Transport Network.
See teletype line protocol handler.
See teletype virtualizer handler.
See universal data-link control handler for remote DCP load/dump services.
See undeliverable message.
Undeliverable Message (UDM)
An input or output message may cause a UDM notification if the endpoint of the session at
which the message was destined for became unavailable. This may cause the session to
remain in a UDM condition until the endpoint either becomes available or is completely
terminated.
Glossary–18 7436 0728–303