OSI/TS Configuration and Management Manual

Glossary
OSI/TS Configuration and Management Manual—424831-001
Glossary-9
PCI (protocol control information).
PCI (protocol control information). Information exchanged between peer entities to
coordinate their joint operation within a specific layer.
PDU (protocol data unit). Information delivered as a unit between peer entities that
contains data and/or control and address information. There are five types of PDUs used
by OSI/AS and OSI/TS:
PDV (presentation data value) list. The form in which the Presentation Layer transmits
data. It consists of a sequence of encoded data values.
Physical Layer. Layer 1 in the OSI Reference Model. This layer establishes the actual
physical connection between the network and the computer equipment. Protocols at the
Physical Layer include rules for the transmission of bits across the physical medium and
rules for connectors and wiring.
Port address. For X25AM lines, the logical port number used to specify the address of the
connection to the X.25 network. For TLAM (for D-series and pre-G06 releases, or PAM
subsystems for G06 and above releases) lines, the address used by TLAM (for D-series
and pre-G06 releases, or PAM subsystems for G06 and above releases) to specify the
address of the connection to a LAN controller. Preferred binary encoding method.
Presentation context. The combination of an abstract syntax (such as ASN.1) and
assignment of a transfer syntax to each on a Presentation Layer connection. For
OSI/AS, the local application provides a list of up to 16 presentation context definitions,
each consisting of a presentation context identifier, an abstract syntax name, and up to
three transfer syntax names. (Users of ACSE can provide up to 15 presentation context
definitions; the presentation context for ACSE is supplied by OSI/AS.) The remote
application decides which of the named transfer syntaxes is to be used for each
presentation context and specifies that transfer syntax in the presentation context
definition result list.
Presentation context definition list. For Compaq OSI/AS, a list containing up to sixteen
presentation context definitions. Each presentation context definition contains a
presentation context identifier (PCID), an abstract syntax name, and up to three transfer
syntax names
Presentation context definition result list. For Compaq OSI/AS, a list containing up to
sixteen elements, each indicating the called application’s acceptance or rejection of one
of the presentation context definitions proposed in the presentation context definition
list.
Presentation default context name. For Compaq OSI/AS, a structure that contains the
default abstract syntax and transfer syntax to be used if the presentation context
definition list is not present
Presentation default context result. For Compaq OSI/AS, a parameter that indicates the
called application’s acceptance or rejection of the presentation default context name.
Presentation Layer. Layer 6 in the OSI Reference Model. This layer resolves the
differences of varying data formats between systems of different vendors. It transfers