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Derivation
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CHAPTER 6
Page
#
DOCUMENT
III TECHNICAL
PROPOSAL
Apr. 29, 1982
6.10 N̲E̲T̲W̲O̲R̲K̲ ̲C̲O̲N̲T̲R̲O̲L̲ ̲S̲O̲F̲T̲W̲A̲R̲E̲ ̲P̲A̲C̲K̲A̲G̲E̲
This section describes the software implementation
of the network control and supervision functions described
in section 4.8.
The Network Control Software (NCS) realizes the Network
Services Environment (NSE). NCS executes on the NCC
processors. NCS of the active NCC has the global network
control responsibility, although certain control functions
may be originated elsewhere than at the NCC.
6.10.1 N̲C̲S̲ ̲S̲o̲f̲t̲w̲a̲r̲e̲ ̲A̲r̲c̲h̲i̲t̲e̲c̲t̲u̲r̲e̲
The NCS architecture is illustrated in figure 6.10.1.
Figure 6.10.1 NCS Architecture
6.10.1.1 N̲C̲S̲ ̲N̲e̲t̲w̲o̲r̲k̲ ̲C̲o̲m̲m̲u̲n̲i̲c̲a̲t̲i̲o̲n̲
The global ACDN network control responsibility resides
with the Network Control Software entities of the NCC
Network Services Environment (NSE).
To enable this global control and monitoring each major
functional entity of the NCS package communicates with
peer level entities in each ACDN nodal subsystem through
permanent transport connections established at system
initialization time.
6.10.1.2 N̲e̲t̲w̲o̲r̲k̲ ̲T̲a̲b̲l̲e̲s̲ ̲a̲n̲d̲ ̲F̲i̲l̲e̲s̲
The global definition of the ACDN network and its environment
is contained in the following NCC/NCS tables:
o Global Network Table
o User Profile Table
o Operator Profile Table
o Terminal Profile Table
Infrequently accessed data are kept on NCC disk storage
files:
o ACDN Network Definition File
o User Profiles File
o Operator Profiles File
o Terminal Profiles File
o Statistics Data File
The format and contents of the Global Network Table
are described in section 6.4.
6..10.1.3 R̲o̲u̲t̲i̲n̲g̲ ̲P̲r̲i̲n̲c̲i̲p̲l̲e̲s̲
This section presents the underlying scheme for implementing
an adaptive routing strategy.
An adaptive routing scheme with a centralized routing
calculation and a decentralized routing selection is
applied.
The routing scheme adapts to the current network topology
and the current load of the internodal trunks.
Routing calculation is performed centrally, and the
resulting routing tables are distributed to each node.
The routing table - which at the arrival at the node
represents the past - in conjunction with the nodes
instantaneous view of the load of the trunks, makes
up the basis for route selection.
6.10.2 M̲a̲j̲o̲r̲ ̲N̲C̲S̲ ̲C̲o̲m̲p̲o̲n̲e̲n̲t̲s̲
The NCS package consists of the following major software
components:
o Network Operator Services
o System Configuration Services
o Network Access Services
o Session Services
o User Services
o Alarm and Event Processor
o Network Test Services
o Statistics Support Services
o Network Recovery Services
The functions of these services and the various component
interfaces are described in the following sections.
6.10.2.1 N̲e̲t̲w̲o̲r̲k̲ ̲O̲p̲e̲r̲a̲t̲o̲r̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
The Network Operator Services (NOS) are responsible
for providing the operator man-machine interfacing
allowing the network operator to control and monitor
the overall ACDN activities.
NOS consist of two subcomponents:
o Command Interpreter
o Display Processor
These support operator input/output in all ACDN network
components.
6.10.2.1.1 C̲o̲m̲m̲a̲n̲d̲ ̲I̲n̲t̲e̲r̲p̲r̲e̲t̲e̲r̲ ̲(̲C̲M̲I̲)̲
The CMI will exist in one incarnation (task) per defined,
active operator position in the ACDN network components,
both NCC supervisory and engineering work positions.
Thus the CMI can receive input both from standard VDU
and colour display keyboards.
Further, the CMI may be configured for communicating
with remote operators, through a standard transport
connection. This feature is applied in the case of
netork supervisory control and monitoring exercised
from a nodal engineering position.
The CMI component performs non-semantic processing
of operator input/output including:
o command input processing
o parsing and classification
o routing of commands to appropriate handler
o response output processing
Command inputs are routed to the software module in
charge of the function related to the command input.
The scope of these commands is described in chapter
4 (see section 4.6).
Further, the CMI is involved in a number of secondary
functions related to the basic operating system. These
are:
o Management processes
o Management of local devices (disk, tape, etc.)
6.10.2.1.2 D̲i̲s̲p̲l̲a̲y̲ ̲P̲r̲o̲c̲e̲s̲s̲o̲r̲
This software entity performs functions which allow
an operator to display control and status related information.
The Display Processor is intended to interface applications
to different types of VDUs:
o Graphic status display VDU (Intercolor 8001) display
station. This is described in section 4.4.2.
o Standard VDUs presenting formatted input/output.
The display processor provides predetermined picture
definitions to applications requiring operator I/O.
6.10.2.2 S̲y̲s̲t̲e̲m̲ ̲C̲o̲n̲f̲i̲g̲u̲r̲a̲t̲i̲o̲n̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
The System Configuration Services (SCS) provide the
functions needed for establishment and maintenance
of a current composition of ACDN, including:
o internal resources (nodes, trunks, routing)
o external resources (lines, concentrators, devices,
hosts and applications)
The SCS program manages the Global Network Table (GNT).
Initially, the GNT is retrieved from the current Network
Definition File. Table operations on GNT, as will take
place when changes to the ACDN network occur, are performed
in memory. However, online configuration changes may
be performed on the Network Definition File also.
The GNT contains all information related to the internal
and external networks. SCS provides the GNT distribution
function for transfer of subparts of GNT to nodal points
needing knowledge only related to their local environment
(local trunks and external resources).
Configuration information is exchanged between SCS
and the local internal and external resource managers
of each participating node through permanent transport
connections setup at system initialization time. These
connections are used for overall distribution of subsections
of the GNT relevant to the scope of individual nodes.
The major functions performed by SCS include:
o Management of Network Definition File and Global
Network Table
o Local Network Table distribution
o Internal resource management (nodes and trunks)
o External resource management (lines, concentrators,
devices, hosts and applications)
o Routing calculation
Changes to configuration and resources occurring locally
at a node are automatically reported to SCS, which
updates the GNT and informs the Alarm and Event Service
process for presentation to the network supervisor.
6.10.2.3 N̲e̲t̲w̲o̲r̲k̲ ̲A̲c̲c̲e̲s̲s̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
The Network Access Services (NAS) are responsible for
validating logon requests to ACDN. Both network operators
and ACDN users are being validated by this software
entity. The logon validation is based on operator and
user profiles.
The logon procedure for network operators and users,
implemented by NAS, as well as general security aspects
are described in section 4.5.
6.10.2.4 S̲e̲s̲s̲i̲o̲n̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
Session Services (SS) processes requests for session
establishment and termination. During the life time
of a session it is managed by the SS software entity.
Session status is maintained in the GNT.
SS includes cross domain functions enabling it to communicate
with host access methods (VTAM, CMS1100) during session
establishment.
The major SS functions include:
Operator commands:
o Initiate/terminate/status of session
o Initiate/suspend/resume/terminate/status of connection
o Set session limits
Internal commands:
o Route session requests from User Services (US)
either to a Cross Domain Resource Manager (CDRM)
emulator or to a session manager depending on destination
end user type
o Switch messages between session managers intended
for address resolution purposes
o Receive accounting information at session initiation
and termination, and write an account record.
6.10.2.5 U̲s̲e̲r̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
The User Services (US) software entity communicates
with all ACDN user terminals on their network control
session.
The following functions are provided by the US software
entity:
o Logon support, validation of user and selection
of default parameters based on user profile, mainframe
application selection, output of logon news and
indication of waiting messages in an electronic
mailbox.
o Logoff support.
o Message switch to other user or to message switch
application.
o Operator notification from user.
o Message broadcasting from operator to group of
users or terminals.
6.10.2.6 A̲l̲a̲r̲m̲ ̲a̲n̲d̲ ̲E̲v̲e̲n̲t̲ ̲P̲r̲o̲c̲e̲s̲s̲o̲r̲
The Alarm and Event Processor (AEP) is the global receiver
of all event messages generated in ACDN. The alarm
system is described in section 4.8.6.
Any event which requires operator notification is routed
to AEP.
The AEP software entity is the manager of the event
log list (file). Entry of events into the log is based
on an event classification scheme.
The AEP module interfaces to the Network Operator Services
for presentation and control of alarms, alerts and
notice events contained in the event log. Through this
interface event notification is routed to the operator
position that has reserved that particular type of
event.
6.10.2.7 N̲e̲t̲w̲o̲r̲k̲ ̲T̲e̲s̲t̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
Network Test Services (NTS) consists of several subcomponents
organized as applications of the network services environment.
NTS includes the following software entities:
o Data Unit Trace
o Loop Test
6.10.2.7.1 D̲a̲t̲a̲ ̲U̲n̲i̲t̲ ̲T̲r̲a̲c̲e̲
Trace applications may be started to receive trace
of all data units passing a given point.
The following traces may be selected:
o Channel data
o Line, concentrator, cluster, or terminal
o Virtual circuit
o Connection
o Session
Trace applications may write the trace data to common
or separate files.
6.10.2.7.2 L̲o̲o̲p̲ ̲T̲e̲s̲t̲
Loop testing is concerned with testing the proper functioning
of different parts of a communication line:
o local loop at LTU
o looping at local modem
o looping at remote modem
The loop test application in the NCC may exercise the
outgoing NCC trunks - or it may request nodes to perform
loop tests on designated links. The positive or negative
test result is returned to the NCC loop test application.
6.10.2.8 S̲t̲a̲t̲i̲s̲t̲i̲c̲s̲ ̲S̲u̲p̲p̲o̲r̲t̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
Statistics Support Services (SSS) are responsible for
collecting statistical data, for making a first level
analysis of the collected data and for producing reports
of network performance characteristics. These functions
are provided by the SSS components:
o Statistics management and collection
o Statistics report generation
6.10.2.8.1 S̲t̲a̲t̲i̲s̲t̲i̲c̲s̲ ̲M̲a̲n̲a̲g̲e̲m̲e̲n̲t̲ ̲a̲n̲d̲ ̲C̲o̲l̲l̲e̲c̲t̲i̲o̲n̲
Statistical data are constantly collected by the nodes
for all resources which have been designated in a START-STATISTICS
command or which are part of the permanent statistics
recording. At regular intervals or when a threshold
is exceeded the statistics records are time stamped
and sent to the NCC where they are written to the designated
files.
The latest statistics record values for each resource
are averaged with the already stored values according
to the formula:
stored-val:= ((n-1) stored-val+new-val)/n
where n is specified at system generation.
The responsibilities of statistics collection are:
o switching on/off statistics collection in subcomponents
o receiving statistics data (on permanent transport
connections)
o performing a first level data compression
o safe storing statistics on disk files
o forwarding statistics to the NMH processor.
6.10.2.8.2 S̲t̲a̲t̲i̲s̲t̲i̲c̲s̲ ̲R̲e̲p̲o̲r̲t̲ ̲G̲e̲n̲e̲r̲a̲t̲i̲o̲n̲
The Report Generation (RG) application can print (display)
in readable form the entries of selected resources
from any statistical file. RG is activated on a regular
basis to produce timed reports and upon explicit operator
request.
6.10.2.9 N̲e̲t̲w̲o̲r̲k̲ ̲R̲e̲c̲o̲v̲e̲r̲y̲ ̲S̲e̲r̲v̲i̲c̲e̲s̲
Network Recovery Services (NRS) are responsible for
initiating the required actions in case of failure
in the ACDN. The ACDN Recovery and Redundancy functions
are described in section 4.14.
The NRS software entities implement:
o checkpointing (internally in subsystem and network
globally, i.e. NCC-NCC checkpointing), i.e. preparation
for recovery.
o failure validation
o management of switchover to redundant elements;
i.e. restart and recovery.
In more detail the responsibilities of Network Recovery
Services include:
Local management:
o PU-PU checkpointing
o PU switchover
o Suprabus switching
o Mirrored disk management
Global management:
o NCC-NCC checkpointing
o NCC switchover to backup NCC
The above recovery functions are described in detail
in section 4.14.
