Department of Computing and
Electrical and Electronic Engineering
Imperial College
|
Department of Computing and Electrical and Electronic Engineering Imperial College |
|
| Name: Vince Avery | Date: 20th May 1997 |
| E-mail: vra@doc.ic.ac.uk | Supervisor: Dr. J.Barria |
Abstract
Every day, many people use the public switched telephone network (PSTN)
for one reason or another, whether it be for browsing the Internet, making a
telephone call or sending a fax. Due to increased user demand for more
advanced and sophisticated network services and for rapid delivery of these
services, new network architectures have evolved. One particular network
architecture that has evolved is the intelligent network (IN). This
provides a complete framework for the uniform creation, provision and management
of advanced communication services. This is essentially achieved by taking the
data required for a particular service and the service logic, outside the
telephone switching network, and putting it into intelligent nodes.
In order to establish specific standards and requirements for the development
of IN architectures, a reference model has been created, called the
IN conceptual model (INCM). This model must be carefully followed as
development of IN architectures continues into the future, to ensure
that world-wide development conforms to the specified standards.
Contents
1) Introduction
In the traditional plain old telephone service environment, the switching systems (typically called 'exchanges') perform the basic call processing, i.e. each switch contains a 'basic call process' which supports a particular telephony service. The switches are lengthy to implement in software, and therefore the introduction of new telecommunications services is a difficult and timely procedure, requiring the modification of the basic call process. Also, as the number of exchanges hosting a particular service increases, the introduction and maintenance of services becomes increasingly complex.
Intelligent networks (INs) were designed to overcome these problems, and to meet increased customer demand for advanced telecommunications services. The IN is an architecture designed to manage and control the services of a telecommunications network. It provides an open platform for the uniform creation, control and management of services, beyond the basic telephone services. The IN can be considered as an additional layer on top of any bearer network, such as the integrated services digital network (ISDN). Although most services could be achieved within existing network environments, the major advantage of implementing services using an IN, is the uniformity of service creation, provision and management, and the reduction in the 'time to market' for a particular service.
2) What is the INCM ?
In order to capture the whole engineering process of the IN, a reference model known as the IN conceptual model (INCM) has been developed. This specific modelling tool defines IN architectures based on the IN service capabilities to be supported. The model is the basis for the development of IN standards in the International Telecommunications Union (ITU) and the European Telecommunications Standardisation Institute (ETSI).
The INCM defines four specific planes (identified below). The lower two planes address the actual IN architecture, whereas the upper two planes focus on service creation and implementation, by means of generic service building blocks.
The four specific planes of the INCM are:
3) What is CS-1 ?
The development of the INCM was an essential stage in the evolution of IN architectures, but was still only a model. The governing bodies for the international standardisation of INs, namely ITU and ETSI, aimed to develop recommendations standards for a series of compatible IN capability sets (CSs). A capability set defines a specific standardised stage of IN evolution in terms of the services to be supported and the functional architecture supporting these services. In March 1992, the first capability set (CS-1) was approved, with a revised version, CS-1R being released in May 1995.
In order to show how the INCM can be used when defining a capability set, the concepts related to CS-1 services and architecture are shown below.
4) CS-1 Service Plane (SP)
This is the uppermost plane of the INCM which describes services from the perspective
of the user, independent of how the services are implemented. CS-1 is targeted to
support single-ended and single-point-of-control services, and does not
support services where several IN subscribers may be associated with a single call.
This is done purely to limit the operational complexity and functional implementation.
'Single ended' means that the service applies to one and only one party in a call,
and 'single-point-of-control' describes control relationships in which a call is
influenced by only one service logic program at any instance in time.
In CS-1, there are many services defined, some of which are listed below:
5) CS-1 Global Functional Plane (GFP)
This plane models the network from a global high-level perspective as a single entity, with specific units of service functionality being described in terms of service-independent building blocks (SIBs). It follows that specific SIBs are then combined into SIB chains, in order to implement IN services in the service plane. In order to customise a SIB for a particular service, data parameters are used. In the GFP, a high-level language interface exists in which the service designer can define service logic programs composed of SIBs, thus designing new services. Many SIBs exist in the GFP, a few of which are listed below:
6) CS-1 Distributed Functional Plane (DFP)
This plane defines the units of network functionality,
known as functional entities (FEs), which are the functions required
for the target architecture. The SIBs in the GFP are realised in the DFP by a sequence
of functional entity actions and the resulting information flows between them.
Typical function groups are basic call-handling functions, service execution functions
and service management functions. To summarise, each CS-1 SIB identified in the GFP,
must be decomposed into an interacting set of functional entities in the DFP, in order
to implement the required functionality.
7) CS-1 Physical Plane (PP)
This plane is the lowest plane of the INCM. It defines the 'real' physical IN
architecture and indicates possible mappings of the functional entities in the DFP
onto physical entities (PEs). The PP also defines the required interfaces between the
physical entities. A typical PE would be a service node, which controls IN services
and allows flexible information interactions with users.
Many physical elements exist in a physical IN-structured network. Aside from specific
call-related PEs, the other types of PEs include a service management point and a
service creation environment point.
To summarise, each of the IN functional entities in the distributed functional plane
need to mapped to physical entities in the physical plane, thus allowing a specific IN
architecture to be implemented.
8) Conclusion
If the services to date are any indication of the future, IN will continue to provide
customer-pleasing services well into the next century. As the IN continues to evolve
and additional modifications are made, new capability sets will need to be defined.
To date, CS-2 has already been produced, and CS-3 is under development.
A basic insight into the standardisation of IN architectures has been presented in this
short article. However, the INCM is obviously not as simplistic as portrayed here, and
each plane has been designed in considerably more detail. It should also be remembered
the INCM is only a model, and detailed implementation of each plane needs to be carried
out, in order to physically implement an IN. When an IN is implemented, obviously there
are some problems that arise, such as how to implement service interactions in the
service plane. Such problems have limited the use of INs world-wide, but these problems
are being overcome, and given time it is believed that INs will become a global
information networking architecture, interconnecting many national and regional IN
installations around the world.
9) References
BOOKS:
JOURNALS:
WWW SITES:
Our "Intelligent Network's" index page.