OSI/AS Programming Manual

Glossary
Glossary-14 056783 Tandem Computers Incorporated
Object-name template. In DSM, a name that stands for more than one object. Such a
name includes one or more wild-card characters, such as * and ?. See also wild-card
character.
Octet. Eight bits or one byte.
Open system. Any computer system that adheres to the OSI standards.
OSI (Open Systems Interconnection). A set of standards used for the interconnection of
heterogeneous computer systems, thus providing universal connectivity.
OSI address. The address of an object on the network, which includes the network
service access point (NSAP). transport selector (TSEL), session selector (SSEL), and
presentation selector (PSEL).
OSI manager process. A process in the OSI/AS subsystem that performs subsystem
management functions, including management of the Management Information Base
(MIB). There is one OSI manager process per OSI/AS subsystem.
OSI Reference Model. A communications architecture, adopted by the ISO in 1984, that
includes seven layers that define the functions involved in communications between
two systems, the services required to perform these functions, and the protocols
associated with these services. See also layer.
OSI Subsystem. One OSI manager process controls one or more TAPS and TSP
processes. The OSI manager processes communicates with NSP processes but do not
control them. The OSI manger, TAPS, TSP, NSP processes can be on the same or
different nodes within the same Expand network.
Packet switch node. Another name for an intermediate system. See intermediate
system.
Packet switching. A technique in which messages are broken into smaller units, called
packets, that can be individually addressed and routed through the network. The
receiving-end node ascertains that all the packets are received and in the proper
sequence before forwarding the complete message to the addressee.
Passive multiplexing. A feature of Tandem OSI/TS that can help conserve X25AM
resources by allocating one single X25AM SU per local network address (X.25 port and
local NSAP address) regardless of the number of concurring transport attach requests.
Compare connection multiplexing and address sharing.
PCI (protocol control information). Information exchanged between peer entities to
coordinate their joint operation within a specific layer.