Question 2/XI - Signalling and OAM Protocol Architecture

Considering

(a) that interworking requirements and the need for convergence between
the various signalling and related protocols has given rise to the need
for a common protocol architecture;

(b) that the OSI reference model, studied by Study Group VII, provides a
good framework, but may not necessarily meet all the needs of ISDN
signalling protocols;

(c) that Study Group XVIII has developed Recommendations I.324 on ISDN
network architecture and I.320 on ISDN protocol reference model and that
close cooperation will be maintained with Study Group XVIII;

(d) that Study Group XVIII has developed Recommendation I.320 on the
ISDN Protocol Reference Model;

(e) that in relation to ISDN overall signalling architecture, there is a
trend towards the "intelligent network" in which the intelligence
required to support new and enhanced features for services and OAM
functions is separated from that required to support basic circuit
switching;

(f) that allocation of functions to functional entities and application
specific procedures to implement specific supplementary services and
remote OAM functions will be studied under Questions CXI and DXI;

(g) that in relation to mixed publicprivate network signalling
architecture:

i) hybrid privatepublic networks, virtual private networks, centrex and
mobile networks will play an increasingly important role in the coming
information age especially in the business sector,

ii) CCITT ISDN Recommendations are intended to be applicable nationally
and internationally not only to public ISDNs but also to private ISDNs;

(h) that there is a need to let the existing protocols interwork with
each other in a logical manner;

(i) that there is a need to maximize commonality and uniformity in the
new selection and definition of higher and lower layer protocols for new
applications for economizing protocol selection and definition efforts
and associated software development costs;

(j) that there is a need to provide a bridge and guidelines for various
protocol selection and definition activities in the Study Group;

(k) that there is a need to work in close cooperation with
Study Group VII and, in particular, to feed back the study results to
Study Group VII in charge of OSI reference model;

(l) that there is a need to provide a basis for consistency in approach
between studies of Question EXI on supplementary services and studies of
Question FXI on OAM functions;

(m) that there is a need to apply the same set of protocols to public
and private ISDNs, thus eliminating the proliferation of signalling
protocols;

(n) that there is a desire to have a common architecture between fixed
and mobile networks;

(o) that there is a need to manage and maintain a set of generic
operation and ASEs in a central register available for use by different
applications and users;

(p) that Recommendation 940 has been developed giving a general
guideline on the architecture concerning OAM at the ISDN usernetwork
interface,

What additional Recommendations andor enhancements to existing
Recommendations are needed for:

Study point a): ISDN call control and OAM protocol architecture

With objectives:

- to define an architectural framework within which the roles and
relationships of existing and new signalling (e.g. DSS 1 and
Signalling System No. 7) and OSI protocols is clarified and to provide
guidelines for selecting and applying protocols,

-to identify requirements and study methods which may be used as a basis
reference model to satisfy needs arising from its application to the
protocol selection and definition work in the Study Group, so that new
protocol selection and definition works for new applications can take a
maximum common and unified approach encompassing both supplementary
services and OAM functions to facilitate evolution toward centralized
control of services ("intelligent network").

Study point b): ISDN overall signalling architecture for supplementary
services and OAM functions

With an objective:

-to produce an overall view of signalling architecture within an ISDN
based on the results of studies on Stage 2 network function
architecture, which encompasses both supplementary services and OAM
functions to facilitate evolution toward centralized control of services
("intelligent network").

Study point c): Clarification of the signalling and OAM protocol
requirements for hybrid privatepublic and virtual private networks
With objectives:

-to provide a basis for determining impacts on specific protocols;

-to give the outputs to the Questions related to overall network
architecture.

The outputs of study points a), b), and c) will provide assistance and
requirements to those studying protocol selection (Questions 5XI and
6XI).