Question 15/II - Traffic models and measurements required for traffic
offered to the network and grade of service
(amended Question 29/II of 1985-1988 study period)

Considering

(a) that traffic offered to circuit groups, to exchanges and on a
pointto-
point basis, is used in forecasting and network design, using both
traditional and advanced engineering concepts (for example, service
protection and advanced routing methods);

(b) that traffic offered cannot be observed directly and must be
estimated from measurements;

(c) that in an ISDN new models for traffic offered and grade of service
may be required, and different estimation models may be required for
different services;

(d) that automatic repeat attempt facilities in digital telephone
networks and/or the ISDN are unavoidable and attractive to hurried
users who are only interested in the total call demand set up time;

(e) that the intervals between successive attempts of a given call
demand can be very short due to the rapidity of Signalling System No. 7,
digital switching and computerized call processing in the terminal
equipment;

(f) that in circuit switching networks, this rapidity leads to strong
statistical correlations between the results of the successive attempts
of a given call demand;

(g) that these correlations can affect the choice of grade of service
parameters, dimensioning rules, traffic and Quality of Service
observation methods,

1. How can procedures for the estimation of traffic offered, in
particular
pointto-point traffic matrices, and the calculation of grade of service
in
stationary traffic conditions be more clearly defined?

2. What measurements are required to collect the data necessary for
these procedures?

3. What end-to-end grade of service parameter (or parameters)
associated with the call demand should be defined to represent the
digital telephone and/or the ISDN user's point of view and what would
be the consequences for ISDN grade of service standards,
dimensioning methods and Quality of Service observation practices?

4. What new Recommendations may be needed taking repeated
attempts into account?