Telserv Manual

Glossary
Telserv Manual—427174-009
Glossary-5
protocol
protocol. A formal description of message formats and the rules two or more machines
must follow to exchange those messages. Protocols can describe low level details of
machine-to-machine interfaces (for example, the order in which the bits from a byte are
sent across a wire), or high-level exchanges between application programs (for
example, the way in which two programs transfer a file across the Internet). Most
protocols include both intuitive descriptions of the expected interactions as well as
more formal specifications using finite state-machine models.
Public Data Network (PDN). A network with data communications services available to any
subscriber.
Request for Comments (RFC). The name of a series of notes that contain surveys,
measurements, ideas, techniques, and observations, as well as proposed and
accepted Internet protocol standards. RFCs are edited but not referenced. They are
available across the Internet.
sensitive command. In DSM, a command that can be issued only by a restricted set of
Guardian users, such as the owner of a subsystem process. For NonStop data
communications subsystems, the sensitive commands are those that can change the
state or configuration of objects, start or stop tracing, or change the values of statistics
counters.
service. A set of primitives (operations) that a layer provides to the layer above it. The
service defines what operations the layer can perform on behalf of its users, but not
how these operations are implemented. A service relates to an interface between two
layers: the lower layer is the service provider, and the upper layer is the service user.
session. For a management application, the period during which an application can issue
commands to a subsystem.
subnet address. An extension of the Internet addressing scheme that allows a site to use a
single Internet address for multiple physical networks. Outside of the site using subnet
addressing, routing continues as usual by dividing the destination address into an
Internet portion and local portion. Gateways and hosts inside a site using subnet
addressing interpret the local portion of the address by dividing it into a physical
network portion and host portion.
subnetwork. One or more intermediate systems that provide relaying and through which
end open systems may establish network connections.
Subsystem Control Facility(SCF). A part of DSM, used to provide a common, interactive
management interface for configuring, controlling, and collecting information from
NonStop data communications products.
Subsystem Control Point (SCP). In DSM, the management process for all NonStop data
communications subsystems. There can be several instances of this process.
Applications using SPI send all commands for dat
a communications subsystems to an
instance of this process, which in turn sends the commands on to the manager
processes of the target subsystems. SCP also processes a few commands itself. It