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Circuit To Packet Migration -- Tools You'll
Need
BY BRIAN SILVER
Historically, carriers that provided both voice and data service built
two networks to carry digital information: One network carried the data, and
the other carried voice. The economics of the carrier have changed in the
past few years, and it is no longer feasible to maintain two networks for
digital information. Price reductions in per-minute charges for voice
service have dropped much faster than minutes-of-use have risen, leaving
little revenue for voice carriers to expand the network. Further,
bit-per-second use of data networks has increased substantially faster than
the prices for access have decreased. This coupled with the annual price
reduction in IP networking equipment (not seen in the monopolistic voice
equipment market) has allowed data carriers to maintain the earnings
necessary to build high-bandwidth networks.
As carriers leverage this investment in data networks for voice and other
services, they will need a rich set of tools. By building an IP network
based on wire speed, complete Quality of Service (QoS)-enabled interfaces
with PSTN mediation, and voice service applications, carriers can begin
building a low-cost, flexible infrastructure capable of supporting rapid
deployment of next-generation voice, data, and multimedia services.
Wire-Speed IP Routing -- MPLS And QoS
To meet their customers' expectations for voice services on a packet
infrastructure, carriers must provide voice quality that is as good if not
better than what subscribers expect today. Increases in network bandwidth
alone do not deliver the guaranteed quality of service and high reliability
demanded by voice applications. Carriers using IP infrastructure to provide
voice service require a new class of IP routers that can provide wire-speed
performance, maintain the high reliability and enable sophisticated traffic
engineering.
MPLS
Multiprotocol Label Switching (MPLS) is the latest technology to be defined
as part of the evolution of IP forwarding. MPLS seamlessly combines IP
routing technology with ATM quality of service to enable a
traffic-engineering paradigm across an IP-based network. The goals when
traffic engineering a network are to gain better network utilization and
create a more manageable network. Segmenting different traffic types allows
the device to provide an appropriate quality of service by allocating
network resources in response to traffic requirements. Of course, these are
not mutually exclusive and the combination of goals is necessary to ensure
toll-quality voice service over a large network. The ideal solution provides
the ability to map traffic to specific routes and dedicate resources to
handle the expected traffic load. A pure IP network can be traffic
engineered via MPLS to provide the benefits of differentiated services and
deterministic network control. The ability to align network resources with
traffic requirements, create a network with relatively low cost, as well as
the ability to offer quality-sensitive voice service, are the motivational
forces behind the desire to traffic engineer packet networks.
QoS
The ability to maintain wire-rate performance while delivering QoS service
is critical to enforce the desired traffic engineering, and maximize the use
of the investment in the infrastructure. If the router cannot use the full
capacity of the link, congestion at the receiving interface will eventually
cause packets to be dropped before they can be classified for QoS. It does
not take many dropped packets to affect voice quality. In order to maintain
wire rate forwarding and still perform the extra processing required to
implement QoS features, hardware support is required. Router hardware that
supports policing, shaping, scheduling and fine grain statistics is vital to
the network design to ensure service quality is maintained.
PSTN Mediation -- Leveraging Existing Investment
The huge investments in existing PSTN infrastructure are still being
depreciated, so it is critical while migrating from a circuit-based
infrastructure to a packet infrastructure to maintain compatibility with
installed equipment. As the two network infrastructures converge, there is a
need to preserve the existing investment in capital and to leverage new
services by combining the best of the two network architectures.
This environment creates an opportunity for new Central Office Equipment
(COE) architectures that provide the capacity required to support data
traffic at a price point that reflects the realities of a carrier's business
needs. Approaches to traffic translation (TDM to IP, for example) must allow
a data infrastructure to coexist with mature voice infrastructure through a
convergence platform that can accelerate the delivery of new services. The
quality of the voice service is also enforced at these gateways, mandating
that the routing and voice gateway products be properly matched and
engineered. These platforms direct signaling, management, and transport
functions to enable services to seamlessly span multiple networks and
technologies. Additionally, signaling integration, support for multiple
legacy and emerging transport technologies, and a set of rules to manage
access to telecommunications and data communications application and
services databases will lay the foundation for enhanced services in the
evolving network.
Value-Added Services -- The Catalyst For Success
New services help attract and maintain subscribers. When offered
quickly, services promise a means of differentiating a provider from the
rest of the pack. Voice services traditionally have generated revenue for
the carrier because they charge for the services beyond the charge for
access to the network transport. "Caller ID" and "Call
Waiting" services are charged separately from the monthly line charge
on a residential telephone bill. Carriers must find services and packaging
that will add value and appeal to a vast subscriber audience in order to
succeed.
Recognizing that carriers are turning to new service offerings as a means
to subscriber retention, forward-looking vendors are providing a technology
framework that enables carriers to create and deliver next-generation voice
and data services over any infrastructure. New service-centric architectures
are built on platforms that form an open network, deliver complete service
creation, and offer a provisioning environment.
From a subscriber perspective, the market for enhanced services is
already here. Using enhanced services as a competitive edge allows the
carrier that has built a multiservice packet network to leverage these
services for greater revenue generation. Carriers must have the
infrastructure in place to provide on-the-fly service creation while meeting
stringent QoS requirements. These new enhanced services are not enough,
though. Customers today have a set of expectations for their voice services.
Transferring a call and forwarding calls are commonplace, and without these
features, no offering would be acceptable. As the carrier migrates from a
circuit environment to a packet environment, it is paramount that services
such as do-not-disturb, voice mail, and call waiting be available for the
first deployment of packet voice service.
Conclusion
Success of the transition from a circuit environment to a packet-based
infrastructure for voice services will be measured by a carriers' ability to
build, deploy, and manage a full range of diverse enhanced services over the
network. The advantage will go to those carriers who can accelerate service
creation and deployment, and further ensure the quality of the network as
perceived by their customers. It is incumbent on the vendor community to
provide carriers with the proper set of tools to build and manage these
networks, and to adhere to industry-wide standards for all aspects of system
interworking. The carrier community should leverage vendors that focus on
building networks, and offer multiple disciplines of both voice networking
and data networking, during the migration to multi-service networking.
Brian Silver is vice president of Voice Strategy Unisphere
Networks, Inc. Unisphere assesses, develops, and markets advanced
technology by providing the technical, business, and financing resources
that transform prototype stage innovations into products that compete
successfully in the global marketplace.
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