The telecommunications landscape is being transformed by the convergence of
voice and data networks with next-generation switching technology. At the
heart of the evolving packet network is the media gateway controller (MGC)
or softswitch, which provides intelligence and call control to the network
by directing sessions between endpoints across ATM, IP, and circuit
networks. The softswitch enables the transition from circuit-switched to
packet-switched networks, interfacing to the PSTN through Signaling System 7
(SS7).
The softswitch offers many advantages to service providers, beginning
with the fact that the combined MGC and media gateway (MG) are typically at
least 50 percent less expensive than the comparable circuit switch they
replace. Softswitches and MGs are built on general computing hardware, and
so, realize price/performance improvements that double roughly every 18
months, in keeping with Moore's Law. The softswitch frees providers to
create networks built on best-in-breed products, rather than being tied to a
single vendor's end-to-end, proprietary solution.
While cost savings can be a compelling argument for the new architecture,
the greatest advantage of the softswitch is its role in service delivery and
creation. The MGC, an open service platform, allows providers to leverage
existing Class 4/5 services via the SS7 network and -- with the benefit of
application program interfaces (APIs) -- create innovative, customer-driven
services that are not possible in proprietary environment.
THE HISTORY OF AIN
The concept of creating an open network where new services can be
deployed faster and less expensively is not new. It has its roots in the
advanced intelligent network (AIN) movement of the 1980s. Before the advent
of the AIN, service providers were forced to rely on their switch vendors
for service creation. That dependency resulted in long and expensive service
development cycles. If a carrier had switches from multiple vendors deployed
in the network, provisioning was a nightmare.
Prior to AIN, there was no way to interject intelligence into the network
or alter the call flow. The AIN model decouples the service logic from the
transport logic, allowing the network to change call routing moment by
moment. There is virtually no limit to the number of actions the network can
take on a call.
However, the AIN's vision of creating a device-independent network in
which services are separated from the network switch has never been fully
realized. Implementation presented a number of problems -- many of the
advanced AIN features simply could not be deployed on legacy customer
premise equipment. This was compounded by the fact that vendors created
different AIN implementations, many of which proved to be incompatible.
THE FOUNDATION FOR A NEW NETWORK
Although AIN did not achieve ubiquitous deployment, the architectural
model did lay the foundation for next-generation, IP- and ATM-based
networks. These networks may fulfill the AIN's promise of putting service
creation in the hands of the carriers and providers.
Fundamental to this new model is an open, nonproprietary architecture
that unbundles the functions of the legacy central office. As in the AIN
model, call control logic is separated from switching and service logic.
This decoupling allows all types of media traffic to be carried on a common,
core data network under the control of the softswitch. Flattening the
network simplifies administration and maintenance and reduces network
infrastructure costs. Carriers are able to implement
"best-in-class" network elements and are freed from the expense
and long development cycles previously associated with enhanced service
delivery in the PSTN.
There is still debate as to where the services will actually reside -- on
service control points (SCPs) in the SS7 network, onboard the MGC, or on
SIP-enabled application servers with open application programming interfaces
(APIs). It is likely that a hybrid, or combination of these approaches, will
evolve. Rather than recreate existing services such as toll free and local
number portability, providers will most likely deploy them from SCPs.
Resource-intensive tasks and session state control will reside on the
softswitch platform to maximize performance, while third-party feature
development for new services will be handled through application or feature
servers.
THE MEASURE OF SUCCESS
The softswitch's success and ultimately that of the new network model
will hinge on a number of factors. The creation of an open architecture
built on standardized protocols such as MGCP, SIP, and MEGACO is essential
to enabling multivendor product interoperability. The softswitch itself will
be required to communicate with multiple switching platforms via multiple
standards to enable interdomain exchanges. Since the softswitch handles many
of the functions of the central office switch, MGCs must scale to support
large carrier networks and match the PSTN's benchmark of "five
nines" reliability.
If the softswitch is to usher in a new network model, it will have to do
more than simply replicate Class 4 and 5 features in a packet format. It
must also to add value to the network by delivering a rich set of new and
innovative features. These new feature sets will ensure the revenue stream
for next-generation service providers.
Richard (Dick) Hayter is the assistant vice-president, marketing for
the Network Systems Division of Tekelec.
Tekelec, a leading supplier of signaling and control systems, develops
innovative network switching and diagnostic solutions enabling the
convergence of traditional and converged wireline, wireless, and IP voice
and data communications networks. The company also provides products and
solutions for call centers and other telecommunications markets.
[ Return
To The January 2001 Table Of Contents ]
|