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                            AP IX-145-E

                             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;






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                              FIGURE A-1/I.350
                                      


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        3x3 matrix approach and determination of availability states

























































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