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Special Focus
June 2003

Convergence Comes To Life

Integrating SIP Into Existing Networks


As businesses move toward the converged communications model, a common concern remains -- how to best leverage existing hardware and software. New technologies -- SIP in particular -- present opportunities for maintaining initial investments during the transition into a converged solution. Although SIP is a critical component in tomorrow�s IP architecture, it is not just for new installations or forklift transitions. Instead, SIP can immediately impact and enhance existing PBX systems, leveraging the benefits of today�s integrated applications.

The introduction of VoIP has allowed communications models to break free of limitations imposed by circuit-switched connectivity, allowing for �limitless� potential in the telephony industry that the data industry has enjoyed for over a decade. This is due primarily to the ability to treat communications as pure data from start to finish or end-to-end. This new flexibility is a fundamental contributor to the excitement behind VoIP and helps to justify the financial investments being made to further its development.

IP telephony fundamentally changes the communications model and in doing so, requires that certain mid- to-high-level protocols exist in order for software to truly leverage its benefits. SIP brings a necessary level of structure to IP telephony so applications can expand, multimedia communications can be blended more seamlessly, and interconnectivity can become the norm instead of the exception.

SIP is the connectivity protocol that creates, in essence, �tunnels� through which communications can occur, and brings with it a structure, or model, around which an entire communications solution can be built. The model of SIP is simple, modular, and extendable -- developers can focus less on how to connect everything together and more on what to do once it�s all connected.

In order for any business to decide how to transition into a SIP model, they must first understand how to evaluate the benefits that SIP offers. New features and capabilities (the �limitless� potential) offer functional benefits. Capital investment and cost of ownership define economic impact. Product options and vendor relationships provide unparalleled options when it comes to selection.

Function as a priority requires that SIP be added to the center of the communications platform -- the most significant area in which SIP can have a positive functional impact. At the center you have the software that provides most of the features that people use and need, from simple call handling features such as transfer/conference, to system features such as transparent networking, Automatic Call Distribution (ACD), and Record A Call. This software additionally comprises most or all of the integration between applications. Adding SIP to the center of the communications model gives the applications -- and most of the system intelligence -- the freedom to expand the way they communicate with each other and with edge devices (e.g., phones and gateways).

Economic benefits are realized when SIP either lowers the initial investment (short term) or lowers total cost of ownership (long term) or both -- resulting in a positive return on investment (ROI). While the short term benefits are easily understood through price comparisons, the long-term advantages are less tangible and require particular assertions. For example, a business that pays for an IP phone or IP gateway with SIP capabilities today, will discover investment protection down the road if they need to change out software at the center. SIP will allow that business to keep the phones they already own and simply change out the central components. The main assumption is that new components purchased later will match up with the current SIP phones to deliver a strong functional solution. Since a large majority of system features come from the core, SIP-enabled phones alone cannot protect or guarantee long-term functional benefits.

With the wide range of interoperability delivered with SIP connectivity, businesses can choose from a broad variety of products, allowing organizations the freedom to decide who they buy from, what they purchase and when they make changes. This freedom extends beyond brands, manufacturers, and integrators, putting decision-making back in the hands of the business, further improving functional and economic benefits.

As businesses migrate toward a SIP-centric model of communications, they should consider SIP as the conduit through which change can occur. Some of the areas SIP improves on, such as instant messaging and presence management, can be integrated with existing software and equipment as an intermediary step toward the future and deployment of full IP systems. When SIP is implemented properly, digital and analog phone users can access benefits without upgrading their phones. This allows businesses to maintain control over transitioning without incurring significant expenses -- key to operational performance. 

SIP has already proven to be an effective tool for merging tomorrow�s pure TCP/IP and SIP architecture together with today�s installed equipment. The following list illustrates some of the things that can be done with existing PBXs if SIP is introduced at the center of the model.

  • Including SIP phones and soft phones as normal extensions along with digital and analog phones.
  • Connecting PBXs together.
  • Delivery of instant messages on traditional display phones.
  • Allowing regular phones to be monitored on an instant messaging network for improved visibility into status (e.g., on call) and availability (e.g., away, at lunch, etc.).
  • Voice calling directly between instant messaging clients and traditional phones.
  • Inbound �trunk� calls from the Internet.
  • Multi-vendor interoperability.
  • Wireless PDA integration.
  • Blending voice, video, and chat calls using existing phones, PCs, and video equipment.
  • Using IP gateways as trunk interfaces to the phone company in satellite locations.

In the pure SIP model of the future, all components (call processing software, integrated applications, phones, etc.) know how to use SIP, and many new things are possible. In the real world of today, few businesses are in a position that allows them to set everything aside and start fresh. The economic impact alone requires that a planned transition occur. This requires business needs and technology to respond to each other.

When SIP is properly evaluated and added to the platform the business is using today, both short- and long-term benefits are observable. If SIP is added only to edge devices, businesses will have a difficult time realizing improvements in the short term. SIP-enabling the core software allows organizations to immediately begin leveraging new functional improvements, which translates to improved communications and more effective operations.

SIP is delivering new benefits in today�s communications environment, while helping organizations maintain control over how they introduce new technology. When implemented appropriately, SIP can be the critical link between the reality of today and the vision for tomorrow.

Aron Aicard is a product manager at Inter-Tel, Inc., an international provider of value-driven communications products and applications, as well as managed services that center on voice and data network design, traffic provisioning, custom application development, and financial solutions that respond to today�s business needs. For more information visit www.inter-tel.com.

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