OSI/MHS Orientation Guide

Glossary
OSI/MHS Orientation Guide—424829-001
Glossary-22
Port Access Method (PAM)
routing. The selection of the adjacent MTA to which a message, probe, or report is
transferred.
routing database. A database in the OSI/MHS registration database that contains records of
ROUTE objects and APPL objects.
routing tables. The internal databases that hold the information about the O/R names.
RS (remote operations service) class. The OSI/MHS CLASS object that identifies the set of
all RS groups in an OSI/MHS subsystem.
RS (remote operations service) process. The process in the RS group that implements the
ROSE protocol. The RS interfaces to the Compaq OSI/AS services, manages
associations from RUAs, encodes and decodes messages, and creates and deletes PDUs
in the MR or MS PDU stores as submit and retrieval operations are successfully
completed.
RS (remote operations service) group. The OSI/MHS group that implements the remote
operations service, giving remote user agents access to an X.400 network through a
message store. An RS group consists of a single RS process and a PDU store. There
can be zero, one, or more RS groups in a single OSI/MHS subsystem.
RTSE (reliable transfer service element). An Application Layer service definition and
protocol supporting the reliable exchange of application data, defining such services as
recovery from end-to-end failures and reporting delivery status to the sender. In
OSI/MHS, the RTS process implements the RTSE.
RTS (reliable transfer service) process. A process in the MR group that implements the
RTSE protocol and accesses the PDU store to read and write messages.
RUA (remote user agent). A user agent that submits and retrieves messages through a
message store and resides on a system or device other than the system that provides the
message store. See also LUA.
SAP (service access point). In OSI, a logical location between two layers, through which the
services of the lower layer are made available to local users, and those of the upper layer
are made available to remote systems. (The SAP is always named after the lower layer;
for instance, an SSAP is between the Session and Presentation Layers.) For the Network
Layer and below, local users and remote systems use the Network Service Access Point
(NSAP) address to establish and maintain connections. For the Transport Layer and
above, local users and remote systems do not use SAP addresses explicitly; rather, they
specify an address called the “(N)-address,” consisting of one or more selectors. See
also selector.
S-selector. See SSEL.
SC (store cleaner) process. A process that scans the MR group PDU store periodically and
removes messages that have been fully processed.
SCF (Subsystem Control Facility). A part of DSM, used to provide a common, interactive
management interface for configuring, controlling, and collecting information from
Compaq data communications products.
schema. The set of rules and constraints concerning the DIT structure, object class
definitions, attribute types, and syntaxes that characterize the DIB.