Expand Configuration and Management Manual (H06.21+, J06.10+)

Glossary
Expand Configuration and Management Manual — 529522-013
Glossary - 5
Layer 3
corresponds to the LINE object referred to by the Expand Subsystem Control Facility
(SCF) interface.
Layer 3. A term that is used to refer to the Network Layer of the Open Systems
Interconnection (OSI) Reference Model. Layer 3 governs the switching and routing of
information between systems in the network and is responsible for error checking and
recovery. The Expand line-handler process’s Network Layer, or path functions,
corresponds to the PATH object referred to by the Expand Subsystem Control Facility
(SCF) interface.
Layer 4. A term that is used to refer to the Transport Layer of the Open Systems
Interconnection (OSI) Reference Model. Layer 4 accepts data from the OSI Session
Layer (Layer 5) and passes it to the OSI Network Layer (Layer 3). Layer 4 provides
end-to-end data integrity between processes and checks that messages received are
correct. The Expand line-handler process’s Layer 4, or path functions, corresponds to
the PATH object referred to by the Expand Subsystem Control Facility (SCF) interface.
Layer 4 send window. A data structure that determines how many Expand packets are
sent before an acknowledgment is required on a single end-to-end (Layer 4)
connection.
line. A single physical connection between two systems. See also route and path.
line buffer. A portion of the Expand line-handler process data space used to buffer
incoming and outgoing messages after they have been formatted into packets by the
Expand line-handler process.
line function. One of the two functions of an Expand line-handler process. A single-line
Expand line-handler process performs both line and path functions with a single logical
device. A multi-line path requires a logical device to manage the path function and a
separate logical device for each line in the path.
line handler. See Expand line-handler process.
line logical device. A logical device that manages a line in a multi-line path. One line
logical device is required for each line in a multi-line path.
LNP. See logical network partitioning.
load. (1) To transfer the operating system image or an application from a disk into a
computer’s memory so that the operating system or application can run. (2) To insert a
tape into a tape drive, which prepares it for a tape operation (read or write).
load balancing. A term used to refer to the balancing of traffic on multi-CPU paths. $NCP
periodically runs a rebalancing algorithm that reconsiders the pairings of Expand line-
handler processes on each multi-CPU path. If the load is unbalanced, $NCP changes
some Expand line-handler process pairs. You can initiate an immediate rebalance
using the SCF RESET PROCESS command or specify when rebalancing should occur