Touted as "the next big thing" for several years, IP Telephony is gaining momentum despite a period of reduced IT spending. Most companies are deploying IP/PBXs, integrated communications platforms (ICPs), unified messaging (UM), and toll-bypass gateways and other VoIP technologies at a steady rate. These expenditures are often made without a thorough analysis of the cost and benefits of VoIP Architecture.



Not all VoIP architecture's are created equal. In order to develop a business case for VoIP, an VoIP architecture for the proposed deployment has to be developed. The VoIP architecture is a high-level design that identifies the business requirements that are being addressed, the major technical and operational components to address these requirements, and the vendors that can provide the products and services. It is recommended that you consider the following issues when developing a VoIP architecture.

?Will the VoIP deployments be 'green-field'?

?Will there be shared resources such as unified messaging, music-on-hold, attendant operators, and PSTN trunks?

?What will be the impact on the WAN of centralizing vs. de-centralizing shared resources?

?How important is fault-tolerance?

?What kind of user interfaces will be supported: legacy analog/digital phones, IP phones, soft-phones?

?How will the VoIP system be administered and managed in tandem with the legacy PBX systems?

?What vendors provide the network elements that best meet our needs?

Each business enterprise is different and has unique needs that cannot be met by every vendor. Developing a complete VoIP architecture is necessary to guide your interaction with the vendors to determine what products best fit your situation.

What are the considerations that need to be addressed while developing a business plan for VoIP Architecture?

?Enterprises need to determine when and how to transition their voice communications infrastructures to the next generation technology and VoIP Architecture. A starting point for migration planning is a solid understanding of the VoIP architectural options.

?Identify your business requirements for VoIP.

?Develop an VoIP architecture document.

?Develop a spreadsheet to model the VoIP architecture.

Include the following elements.

?Demand forecast ? quantities of users and locations; types of technology to be deployed for each user and location.

?Cost of each network element to be deployed.

?Increased or decreased recurring costs of operating and managing the network.

?Increased network bandwidth costs.

?Model the costs of alternatives to the VoIP architecture.

?Identify non-financial costs and benefits for each architecture/alternative modeled.

?Develop a presentation that compares the financial and non-financial measures.

Quality is very important in implementing VoIP architecture. The main challenge with VoIP Architecture is implementing the appropriate Quality of Service (QoS) to ensure that voice packets arrive at their destinations in an acceptable time frame (within 150 msec) and with minimum jitter (variation in inter-packet delay), so that users hear a continuous flow of speech.

To accommodate these requirements, most enterprises use high-speed (10/100 Mbps) Ethernet switches to connect endpoints on their LANs. They also configure Virtual LANs (VLANs) to segment voice endpoints from data endpoints, thereby minimizing the potential for data packets to adversely impact voice packet delivery. In addition, the IEEE standard 802.1p/Q allows packet prioritization, giving voice frames higher priority than data frames.

The basic building blocks of VoIP Architecture based PBXs and ACDs are gateway devices that convert calls from TDM to IP, call control processors, IP phones, and the associated data communications infrastructure (routers, Ethernet switches, and cabling). This basic architecture comes in two flavors: IP-enabled and IP-centric.

The two are primarily differentiated by:

1) Where the TDM to IP conversion takes place

2) Where supporting call center functions, such as queuing, queue slots, prompting, music on hold, and announcements, take place.

3) The CPU/common control and call control software may reside in the TDM switching matrix, or on an external server.