Question 3/XI - Switching functions and signalling information flows for
implementation of basic and supplementary services

Considering

(a) that a general Recommendation exists on a method for characterizing
services and supplementary services (I.130), and that
Recommendation Q.65 describes Stage 2 of the method in detail;

(b) that the introduction of new types of switching and signalling
systems provide an increasing potential for basic and supplementary
services;

(c) that the need to allow supplementary services to operate throughout
the network rather than being restricted to a single model and that they
operate consistently also in a hybrid privatepublic, virtual private
network and centrex network environment and with mobile networks;

(d) that the ISDN access signalling and CCITT Signalling System No. 7
will allow a greater range of information transfer between the network
and the user, and within the network;

(e) that there is a need to ensure compatibility and consistency
between:

-the information-flow descriptions and the user-network signalling,

-the information-flow descriptions and the inter-network-nodes
signalling,

-the user-network signalling and the inter network-nodes signalling,

-the signalling systems and the switching capabilities;

(f) that service centres will become increasingly used in the future;

(g) that Stage 1 Recommendations (including packet mode services) are
becoming increasingly available;

(h) that network architecture studies will continue in the CCITT which
could affect the studies on network functions and information flows, and
that there will be a need for Stage 2 studies to interact with these
architectural studies,

further considering

(i) that the CCITT has developed SDL for the ambiguous specification and
description of the behaviour of telecommunications systems;

(j) that CCITT and ISO are specifying further tools, such as abstract
syntex notation (X.208) which may be useful in Stage 2 service
specifications.

1. What enhancements to Recommendation Q.65 and what possible new
Recommendations are necessary to specify the Stage 2 method? including:

a) the overall signalling information flow for basic and supplementary
services;

b) the procedures within networks for the establishment and control of
these services;

c) a method of classifying basic and supplementary services for a
systematic approach to the definition of Stage 2 and Stage 3
descriptions.

2. What new Recommendations and what enhancements to existing
Recommendations are necessary in applying the methodology?

a) to achieve compatibility and consistency between the switching
functions, other network functions, and signalling systems required to
implement these services;

b) to optimize the balance between switching functions, other network
functions and signalling systems required to achieve these services;

c) to specify the logic procedures within the exchanges for services and
supplementary services which require standardization and when necessary
the possible location(s) of functions within the network (e.g.,
exchanges, terminal or auxiliary devices).

Note 1 - This Question requires close cooperation with the present
Study Groups I, II, III, VII, VIII, and XVIII.

Note 2 - Analysis of services, especially supplementary services, will
concentrate on those requiring procedures distributed throughout the
network, rather than those capable of being implemented at a single
terminal or exchange. This former group of services will include:

- services to be operated internationally;

- services requiring a unique solution for the purposes of the ISDN.

ANNEXES 1 through 7

(to Question 3/XI)

(See Contribution COM X7.)