Introduction to Tandem X.25 Capabilities

Glossary
065307 Tandem Computers Incorporated Glossary–9
RNR. Receiver not ready. Link-level frame or packet-level packet. As a packet, it
acknowledges the receipt of data and requests that packet transmission be halted.
RPOA. Registered private operating agency. The RPOA is a packet network,
value-added carrier, which acts as a transmit network within one country or between
countries.
RR. Receiver ready. Link-level frame or packet-level packet. As a packet, it
acknowledges the receipt of data and requests that packet transmission continue.
RS-232-C. An industry standard defining the physical characteristics of the cable and
25-pin connectors used for connecting a DTE and a DCE.
RS-449. An industry standard defining the physical characteristics of the cable and the
37-pin and 9-pin connectors used for connecting a DTE and a DCE.
SABM. Set Asynchronous Balanced Mode. The unnumbered command frame sent by
one station to establish a data link with the other station.
SCF. Subsystem Control Facility. A subsystem used for issuing configuration and
information requests between the user and some communications subsystems.
secondary station. In an SDLC or ADCCP-NRM configuration, the station that is
contacted by the primary station and is controlled by the primary message in a
message exchange. The secondary station cannot initiate a communication. This type
of configuration is not used for X.25 connections. However, the combined station used
for X.25 connections is logically divided into a primary substation and a secondary
substation. See also primary station.
SIT. System-image tape. Contains an operating system ready to be loaded onto a
Tandem system.
SNA. Systems Network Architecture. An IBM-proprietary model of data
communications.
SNAX/CM. SNAX Connection Manager. A Tandem product that enables a Tandem
system to call out to remote SNA devices through a PSDN.
SNAX/XF. Tandem product used to communicate with SNA networks. SNAX/XF can
run over an X25AM line.
SU. Name of an object used by SCF to refer to a subdevice.
subaddress. A portion of the X.121 address, which can be used to directs calls to
specific devices or application. Also referred to as a port number.
subdevice. Logical component of X25AM, providing access to a circuit.
Subsystem Control Facility. See SCF.
Subsystem Control Point (SCP). A process through which management applications,
including the SCF utility, control communications subsystems. SCP is a management
process, as defined by DSM.