Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-7
Network Control Process ($NCP)
Network Control Process ($NCP)
The network control process, $NCP, is a process in each node of an Expand network.
$NCP uses services provided by the network utility process, $ZNUP. $ZNUP is part of
the NonStop Kernel operating system.
Network Control Process Functions
The network control process, $NCP, is responsible for the following functions:
•
Initiating and terminating node-to-node connections.
•
Maintaining the network-related system tables, including routing information.
•
Calculating the most efficient way to transmit data to other nodes in the network.
•
Monitoring and logging changes in the status of the network and its nodes.
•
Informing the network control processes at neighbor nodes of changes in line or
Expand line-handler process status (for example, lines UP or DOWN). Neighbor
nodes are two nodes that have a path configured between them.
•
Informing Expand line-handler processes when all paths are DOWN. Expand line-
handler processes respond by aborting pending requests.
•
Grouping Expand line-handler processes in a multi-CPU path to a particular
neighbor node.
The network control process runs as logical device number 1.
Network Utility Process Functions
The network utility process, $ZNUP, answers requests that must wait for system
information. It also responds to requests for the time at remote systems, the process
information of remote processes, device-information requests, and traffic statistics.
The network utility process runs as logical device number 4.
Expand Manager Process ($ZEXP)
The Expand manager process, $ZEXP, provides the interface between the Expand
subsystem and the Subsystem Control Point (SCP). The Expand manager process
must be started and named $ZEXP. SCP is the managing process for the Subsystem
Control Facility (SCF). The Expand manager process directs SCF commands to the
appropriate Expand line-handler process and forwards responses from Expand line-
handler processes to the appropriate user.
Note. For more detailed information about the Expand-to-ATM interface, refer to Expand-to-
ATM Interface on page 18-59.