Subject: RE: Service Definitions: Top Down Vs Bottom Up.....

From: "Karen Goettler" <[email-masked]>
Date: Tue, 1 Dec 1998 07:46:25 -0700

Just some comments on some previous email.  I applaud you guys for making
the effort to define VOIP service processing and standards.  Please,
however, keep an open mind to what the ITU has already defined for IN and
TINA services.

> I've never quite understood why we need "call models" per se for
> the CPL, as I seem to be able to design fairly plausible-looking
> service descriptions without having specified one.
The call model is important because it defines set, standardized points in
the call processing logic, where control of the phone call can be passed to
another network element. A complex call model (i.e. the more trigger
detection points and call states defined in your call model) supports more
complex and distributed services.

> It seems to me that describing services in terms of what
> proxies/gatekeepers actually *do* with signaling information is
> more directly understandable than a high-level abstract
> description of calls which ignores the distributed nature of the
> system.

It is possible to define services via a bottom up approach, which is
defining services by defining what the services do beginning at the physical
level.  The approach the ITU took for defining IN services, however, is the
top down approach where the service is defined, broken down into functions,
and then the functions are distributed among the network elements.  A top
down approach for service definition allows the most reuse of the service
functions, provides for more efficient services, and creates a more complete
overall service architecture.  It also makes it easier to provide service
management and provisioning at the network level, as opposed to at an
individual service level.

> For those of us who are coming at this more from the Internet
> side, can you explain what "functional roles" actually means?

This is a simplified explanation  of why defining functional roles is
important.....In ITU's definition of the IN architecture, they first define
the services that the CS version will support.  Once the services to be
supported are defined, the services are broken down into what functions need
to be performed by the network to make these services happen and the
functions are assigned to specific network elements.  This allows the
services to be defined independent of the network elements and allows
flexibility on which network elements provide the required service
functions.  Functional roles are the service functions that a network
element provides to the call processing network.

-----------------------------------------------------
Karen Goettler
phone - 303 734-5015
fax   - 303 734-4244
[email-masked]

PEAK Software Solutions, Inc.
7851 S Elati Street, Suite 200 Littleton, CO  80120
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