Deploying Enhanced Services In Softswitch-Enabled
Networks
BY JACK KOZIK
[ Go Right To Services News
]
When softswitch technology first became available, it was seen as a way
to address the shortcomings of the circuit-switched world. Softswitches
promise to bring the speed and flexibility of the Internet to the
telecommunications industry. But to fully deliver on this promise,
carriers need to avoid duplicating some of the missteps of the circuit
world in packet networks.
One of the first steps is to adopt a "service separation"
strategy and distribute applications throughout the network. The next move
is to determine which interface (or interfaces) would make the network as
fast, flexible, and feature rich as possible.
While the value of softswitch technology in next-generation networks is
irrefutable, its existing architecture could recreate some of the same
problems found in circuit-switched networks. The softswitch provides new
tools and technologies to build services in a more productive,
Internet-based service creation environment. If carriers decide to move
all of their services off the circuit switch and onto a softswitch they
could be left with another monolithic, closed system that is difficult to
manage and upgrade.
A carrier could end up with more than 30 million lines of code on a
central softswitch if every service resides in the same place -- eerily
reminiscent of today's circuit switches. This is a key reason why today's
circuit offerings are slower than their packet counterparts. It is not
because circuit switches are inherently slow, but rather because all the
software is concentrated in one place.
ADOPTING A SERVICE SEPARATION STRATEGY
Carriers can avoid this problem by partitioning their services, rather
than loading them all on one softswitch. Some softswitches are especially
well suited for handling certain types of calls. Moving some services from
a central softswitch server onto "application specific"
softswitches is an excellent first step toward partitioning services. For
example, one softswitch may be used to provide only residential dial tone,
while others would handle tandem duties, business Centrex features, and so
on.
Because the key purpose of softswitches is to perform call processing
(set-up and tear-down of a call), the use of application-specific
softswitches is only the first part of a comprehensive service separation
strategy. To complete the strategy, carriers also need to deploy
applications servers.
For carriers, one of the big payoffs for putting softswitches in a
network is that it gives them a platform technology similar to that used
on the Internet. In addition to serving as the engines behind the
Internet, applications servers can readily talk to softswitches. Just as
the applications servers of the Internet are used to support e-commerce
services, carriers can use applications servers to help partition enhanced
telecommunications services.
CHOOSING THE RIGHT INTERFACE FOR THE JOB
Assuming a carrier deploys softswitches according to a separation
strategy, the next challenge is determining which interface protocol to
select. An IP interface seems like the obvious answer, but this may be too
simple a response given customers' growing expectations from their
telecommunications provider.
There's no question that carriers need standard interfaces that will
facilitate the interoperability between their softswitches and
applications servers. Just as it would be inappropriate to have a separate
Web browser for each Web site visited, global carriers do not want a
different version of an enhanced service for each softswitch on the
market. But the question remains: Which standards to choose?
Of the many technology options available, the industry has begun to
gravitate toward three enhanced service protocols that serve as useful
interfaces between softswitches and applications servers. They include
Session Initiation Protocol (SIP), Lightweight Directory Access Protocol (LDAP),
and Intelligent Network (IN) protocols. While some carriers would like to
narrow the choice to one, the truth is, each plays an important and
complementary role in an IP-based network.
Session Initiation Protocol
SIP has increasingly become the favored protocol between softswitches
and applications servers. For services where an applications server is
hosting the service logic, SIP is used to set up a temporary session (or
call) to the server so it can execute the necessary enhanced service
logic. The exciting part of interfacing to SIP is that carriers can also
interoperate softswitch-based voice services with other Internet services.
This enables them to create interesting feature combinations that they
would not be able to offer otherwise (e.g., linking the status of a mobile
phone with instant messaging, or linking caller ID to Web page content).
Because SIP resembles HyperText Transport Protocol (HTTP), it can run
through firewalls and routers to take advantage of all of the constructs
in an e-commerce environment. As such, carriers are free to interoperate
with, and build upon, the innovation curve that is rapidly taking place in
the Internet paradigm. By using SIP, carriers can link voice services with
revenue-generating enhanced services that are attractive to customers,
including instant messaging, chat, Web pages, pre-paid, Internet call
waiting, virtual private network, follow-me, e-mail, and more.
Lightweight Directory Access Protocol
LDAP is the standard directory server technology for the Internet. For
example, when a subscriber types a name on an e-mail system today,
typically the system retrieves the e-mail address from an LDAP server.
Because most softswitches and services are inherently a translation
between numbers and addresses, LDAP is an invaluable protocol for
supporting applications that are not well served by SIP. In fact, LDAP and
SIP should be thought of as peers in terms of their service richness
potential. Directory-oriented services best suited for an LDAP look-up
include unified messaging, free phone (800 number translation), calling
name service, and Internet phone number hosting.
Intelligent Network
Why use IN protocols to interface softswitches with applications
servers? First, IN standards are widely deployed across the globe and are
generating billions of dollars in service revenue today. Second, by
interoperating softswitches with IN, carriers who already have IN and
circuit switches have a ready-made vehicle for ensuring service
transparency as they migrate their networks from circuit to packet.
IN is already a proven revenue generator for carriers. Therefore, as these
carriers migrate their voice services from circuit to packet networks, why
should they be asked to shut off this revenue stream and replace it with
new equipment in a packet environment? Why not use use packet-enabled IN
to enhance their revenue stream with new technology?
Customer demand for voice services won't go away. New and established
carriers are going to want to provide IN services such as local number
portability, carrier selection, personal number, free phone, pre-paid,
call screening, call centers, and voice VPN to capture and/or maintain a
share of this lucrative market segment.
A WINNING COMBINATION
While carriers are enthusiastic about the new service creation
capabilities made possible by the softswitch layer, they are asking their
vendors to ensure that these new capabilities don't put services -- and
the industry -- back where they started. The challenge of delivering
services will only intensify as networks continue to get larger and more
complex. One need only look at any of the new super carriers recently
created through mergers to recognize the scope of the task. This makes
adopting a service separation strategy all the more important.
Additionally, given the sheer number of services that are becoming
available -- from Web hosting to content caching to instant messaging to
calendar maintenance -- it's clear that no single protocol will serve
every need. Softswitches are connection-oriented platforms, while
applications servers tend to be transaction-oriented, therefore more than
one approach is needed. That's why SIP, LDAP, and IN together are the
right combination of protocols to allow carriers to build a bridge between
today's services and tomorrow's packet networks.
Jack Kozik is Intelligent Network architecture evolution planning
director for Lucent Technologies' Intelligent Network and Messaging
Solutions Unit.
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