OSI/TS Management Programming Manual

Glossary
056786 Tandem Computers Incorporated Glossary-23
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. See also CSMA/CD.
Token code. In DSM programmatic interfaces, a 32-bit value that identifies a token. A
token code consists of a token type (16 bits) and a token number (16 bits). In Pascal,
TAL, C, TACL, and COBOL85, names are used to represent token codes (ZSPI-TKN-
SSID, for example). See also token map.
Token map. In DSM programmatic interfaces, a structure that contains decoding
information for a DSM extensible structured token. Also, a variable name used to
reference an extensible structured token. The token map includes a token code and a
description of the token value: its fields, the null values of those fields, and the
versions of the fields. A token map defines a structure that might change in some later
code version (by the addition of new fields at the end), and the information in the map
allows SPI to provide compatibility between different structure versions.
Token number. In DSM programmatic interfaces, the number used by a subsystem to
identify each DSM token that it defines. The token type and the token number
together form the token code.
Token type. In DSM programmatic interfaces, the part of a DSM token code that
identifies the data type and length of the token value. The token type and the token
number together form the token code.
Token value. In DSM programmatic interfaces, the value assigned to a DSM token.
TPDU (transport protocol data unit). See PDU.
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 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. The classes are:
Transport Class Function
Transport Class 0 Provides simple service.
Transport Class 1 Provides basic error recovery.
Transport Class 2 Provides multiplexing.
Transport Class 3 Provides error recovery and multiplexing.
Transport Class 4 Provides error detection, recovery, and multiplexing.
Transport entity. A process in the Transport Layer that sends or receives a given TPDU.