ANNEX A

(to Recommendation I.350)

Method of identifying parameters

1.	The matrix approach

The matrix provides a systematic method of identifying and organizing candidate network performance parameters with the objective of defining a concise set of parameters and, where appropriate, their QOS counterparts. This tool should be used as the basis for collection and evaluation of network performance parameters for digital networks, including ISDNs.

2.	3x3 matrix approach for network performance

The 3x3 matrix approach for network performance is illustrated in Figure A-1/I.350. The main features are as follows:

1)	each row represents one of the three basic and distinct communication functions;

Note - The access function represents the connectionless as well as connection oriented services which are possible with ISDNs.

2)	each column represents one of the three mutually exclusive outcomes possible when a function is attempted;

3)	the 3x3 matrix parameters are defined on the basis of events at connection element boundaries and are termed "primary performance parameters". "Derived performance parameters" are defined on the basis of a functional relationship of primary performance parameters, outage thresholds and an observation interval;

4)	NP primary performance parameters should be defined so as to be measurable at the boundaries of the connection element(s) to which they apply. NP parameter definitions should not depend upon assumptions about impairment causes that are not detectable at the boundaries;

5)	availability is a derived performance parameter. Decisions on the appropriate primary performance parameters, outage threshold and algorithms for its definition require further detailed study.

Note 1 - The following terminology problems are pointed out. Appropriate terms should be selected after further study:

a)	the term "access" is used. However, the term "selection (of the connection type, the destination and facility)" has been proposed as an alternative;

FIGURE A-1/I.350

3x3 matrix approach and determination of availability states