An Introduction to the Ericsson Transport Network Architecture ...

Fig. 4
Control System Architecture
CP
UP
ICM
SNC
Central Processor
Unit Processor
Internal Communication Network
Switching Network Controller (only SDXC)
Each unit in the system has a powerful microprocessor,
and a central master computer
co-ordinates all the unit processors
and provides input/output.
Unit processors enable the unit itself to
perform a large amount of processing and
so reduce the load on the central processor.
All processors are connected to an Internal
Communication Network (ICN). Depending
on the size of the Network Elements,
different internal communication
network structures have been implemented,
Fig. 4.
The central processor houses the MIB, on
which the OS and the local operator perform
management operations. It will also
implement parts of the MCF functionality,
such as a network layer routing function
between the Q- interface and the ECC subnetworks.
The central processor can vary in size from
small and inexpensive one-board microprocessor-based
systems, to high-capacity
redundant computers.
Each of the different printed board assemblies
under the control of the Central Processor
contains its own Unit Processor.
The Unit Processor is a building block consisting
of a microprocessor, memories,
communication controllers and A/D and
D/A converters when required.
The Unit Processors perform routine tasks
on each printed board assembly, such as
alarm surveillance, collection of performance
parameters, and self-diagnostics.
The Unit Processors also control the lower
layers of the ECC protocol suite.
The control system software modularity is
ensured through the use of a layered structure
combined with object-oriented techniques.
Programs can be downloaded from an Operations
System all the way down to a Unit
Processor.
Control of Switching Network
Besides Unit Processors and the Central
Processor, the control circuitry of the
SDXC switch, SNC, is also connected to
the Internal Communication Network. This
means that all processors can set up and
release cross-connections in the SDXC.
This facility comes into use, for example,
when rapid switching has to be performed
due to a transport network fault discovered
by an access unit. In this case the Unit
Processor on the access unit immediately
reconfigures the switch according to a predefined
configuration previously communicated
to the Unit Processor by the Central
Processor. The Central Processor is
always informed of the resulting configuration.
Unit Processors
Unit Processors typically occupy part of a
board in the SDXC. A unit in the SDXC normally
consists of only one board. A Unit
Processor includes a microprocessor chip
and memory. Its current implementation is
a Motorola 68 302.
A Unit Processor continuously performs
tasks such as monitoring of hardware and
calculation of bit errors, but at the same
time it must react quickly to events such
as incoming alarms from the transport network.
The unit processor is therefore
equipped with a real-time operating system
kernel, OS 68, which gives response
times on a microsecond level.
SDXC CONTROL SYSTEM
ARCHITECTURE
General
The SDXC control system may be composed
of a central processor and up to a
couple of 100 Unit Processors. It uses a
packet-switched Internal Communication
Network (ICN) which is integrated with the
switch.
Purchased hardware and software is used;
the Central Processor being a UNIX computer,
for example.
Central processor
The Central Processor is the coordinator
and master of the complete control system.
It continuously monitors the Internal
Communication Network to find new Unit
Processors. Local operators have access
to the SDXC system via graphical workstations.
These are connected to the Central
Processor via an Ethernet Local Area
Network, Fig. 5. Both the Central Processor
and the operator workstations are
UNIX machines based on SPARC architecture,
the Central Processor being a
ERICSSON REVIEW No. 3, 1992