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Recommendation E.710
ISDN TRAFFIC REQUIREMENTS OVERVIEW
1 Introduction
This Recommendation outlines the general consideration in modelling
traffic flows in ISDNs. More detailed descriptions for specific services and
significant points1) in the network are given in Recommendations of the E.710
Series as follows:
E.711 - User Demand
E.712 - User Plane Traffic Models
E.713 - Control Plane Traffic Models
E.714 - Management Plane Traffic Models.
Additional Recommendations in this Series will be developed in the future
to reflect ISDN developments.
Note - Recommendations E.712 and E.714 are for further study.
2 Context
ISDN concepts, services and networks are described in the Series I
Recommendations. The E.710 Series of Recommendations have been developed
consistent with the approach. However, the grouping of material in the E.710
Series concentrates on the important aspects from a traffic point of view of ISDN
operations in the immediate future.
An important modelling technique used to represent ISDN capabilities is
the layered architecture described in Recommendations I.310 and I.320. The E.710
Series have been developed using this approach. At present the E.710 Series
concentrates on lower layer (1-3) traffic flows. Higher layer traffic flows are
for further study.
The user plane/control plane perspectives described in Recommendation
I.320 have been used to provide two separate traffic models in Recommendations
E.712 and E.713. Nevertheless, it should be kept in mind that many traffic
engineering procedures described in subsequent E.700 Recommendations require
incorporating traffic loads from both planes using the same resources. The
influence of the management plane is for further study.
The ISDN reference connections used in the E.710 Series are those given in
Recommendation E.701.
3 User demand
ISDN users have various needs for information transfer. The user and his
terminal equipment transform these needs into a series of call demands for
available ISDN services. These transformations involve many functions including
coding, and peer-to-peer and inter-layer protocols. The higher layer functions
are not analysed in the E.710 Series.
Recommendation E.711 starts from the expression by the user of a call
demand to use the ISDN services defined in Recommendations I.230 and I.240.
Corresponding traffic variables including the number of attempts per call demand
are derived for the relevant attributes of each service.
4 User plane
In the user plane the attributes of some ISDN services give rise to
additional traffic parameters beyond those used in telephony. Based on the user
models of Recommendation E.711, Recommendation E.712 will be developed in the
future to derive traffic models for each basic ISDN service using a common set of
parameters that applies to all services.
5 Control plane
Each attempt from a terminal will result in signalling messages in the
control plane. The number of messages and their length are highly dependent on:
- protocols (S.S. No. 7 and Q.931 digital access);
- call disposition (including user facilities);
- originating and terminating subscriber equipment configurations (e.g.
overlap sending).
Control plane traffic models given in Recommendation E.713.
6 Further developments
The preceding sections of this Recommendation and the Recommendations of
the E.710 Series concentrate on those services and facilities which will
predominate in the first ISDNs to be implemented.
However, the ISDN concepts include the inherent possibility of developing
completely new services and functions in response to changing user needs. This
1) significant points are points in the network where traffic flows and grades of service
should be evaluated.
Fascicle II.3 - Rec. E.710 PAGE1
will result in new traffic situations that will need to be covered in the E.710
Series. Some of the situations which can be anticipated are:
- the impact of supplementary services, such as call waiting, on control
plane traffic;
- new ISDN capabilities such as statistical switching and dynamic
allocation;
- connectionless communications;
- the impact of user-to-user signalling;
- the impact of multipresentation type calls, and simultaneous use of
different interactive and distribution services, involving multi-slot
and multipoint connections, and broadcast mode.
PAGE2 Fascicle II.3 - Rec. E.710