Contents Telektronikk - Telenor

154
and CMR measurements was set to 80 %
of the synchronous digital hierarchy
(SDH) payload capacity. This results in
approximately 282,566 cells/second. It is
then simple to calculate that during a 12
hour period approximately 1,220,685
x1010 cells will pass through the switch
during this time. With a CLR of 10 –10
this means roughly that only one cell is
allowed to be lost during each test
period.
Because of this, each test had to be run a
number of times. At least 10 times is suggested
here. This will significantly increase
the reliability of the performance
measurements made.
5 Future testing
The tests performed on the Ericsson system
were mainly performed in order to
verify the performance of equipment
being delivered for integration into the
pan-European pilot project. As this was
an ATM network in its first stage of
deployment, the requirements and tests
were maintained at a simplest possible
level. Only a peak rate bandwidth allocation
scheme was implemented and semipermanent
connections were established.
These semi-permanent connections were
used to offer a Virtual Leased Line
(VLL) service.
During the second stage, equipment will
need to offer a much wider range of services.
Switched connections must be supported
and several different bandwidth
allocation schemes will be required. This
will necessitate complete compliance with
the ITU-T recommendations I.356, I.371
and I.610 (among others). For example,
compliance with these recommendations
will in the future enable us to perform inservice
performance monitoring.
In-service measurements should give us
much better information about the network
performance during real load conditions.
These measurements may also be
made without the need for external test
equipment. Measurements may be made
at any time, during any traffic loads and
over any duration of time.
Although these recommendations are not
yet finalised, much is done. Ongoing and
future tests will contribute information
required to complete these recommendations
within the standardisation organisations.
6 Concluding remarks
This paper has attempted to show that
simple measurements can be made in
order to verify the performance of an
ATM switch or network. Before the testing
was started certain requirements
regarding the CLR, CER, CMR, CTD,
and CDV were obtained from network
operators wishing to purchase the Ericsson
equipment.
Various methods of measuring the cell
performance are explained with both the
test set-up, the protocols used and the
parameters necessary to record are given.
The test results are presented and then
their validity has been discussed. When
discussing the validity, focus is placed
upon the fact that rare events are difficult
to measure accurately. Due to this difficulty
in measuring rare events, it was
stated that these tests should be performed
a number of times.
In conclusion, the test results indicated
that the switch under test did conform to
the requirements specified.
7 References
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