IP telephony implementation planning

Expert advice breaks down a successful IP telephony implementation into two distinct and easy to understand steps.

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There are two distinct steps needed before you can begin an IP telephony implementation. One is analyze business goals and future expectations. The other is to analyze the current network infrastructure. This article from Informit examines both of these steps with the help of a fictional company, XYZ.


Getting Started
The first step in the planning phase is to understand the high-level business and technical expectations and requirements for the future IPT network, which include the following:

  • Company vision, goals, and forecasted growth
  • The plan for voice and data networks over the next 3 to 5 years
  • Solution expectations
  • Deployment and timing
  • Financial expectations

To simplify the discussion for this case study, assume that XYZ expects its workforce to grow 5 to 10 percent every year. XYZ requires that the new IPT system must emulate the functionality of the current PBX, voice-mail, and application systems, be scalable, and provide additional services and features that improve employee productivity. The new technology update project at XYZ received approval from the company's financial board to support the funding for the IPT project, and there are no major budget constraints.

After you understand the high-level business and technical expectations of the company, the next step is to conduct meetings with the engineers and architects in the LAN, WAN, IT, legacy PBX, legacy voice-mail, and applications network groups. During these meetings with the various groups, you should make sure that any high-level requirements are accurate. Most importantly, make sure that you understand how the existing network infrastructure is built so that you can identify the gaps in the infra-structure that need to be filled to support the converged traffic.

Network Infrastructure Analysis
Another term commonly used for this analysis is IP Telephony Readiness Assessment. The purpose of this assessment is to check whether the company's network infrastructure is ready to carry the converged traffic. The assessment covers basic LAN switching design, IP routing including power and environmental analysis, and so forth. As a network engineer, you are required to identify the gaps in the infrastructure and make appropriate recommendations before you move forward with the IPT deployment.

The network infrastructure analysis of XYZ is divided into eight logical subsections:

  • Campus network infrastructure
  • QoS in campus network infrastructure
  • Inline power for IP phones
  • Wireless IP phone infrastructure
  • WAN infrastructure
  • QoS in WAN infrastructure
  • Network services such as Domain Name Service (DNS) and Dynamic Host Configuration Protocol (DHCP)
  • Power and environmental infrastructure

After reviewing the preceding list, you might be wondering why planning for the IPT network includes analyzing campus infrastructure (Layers 1, 2, and 3), WAN infrastructure, LAN and WAN QoS, and network services. The analysis of the aforementioned network infrastructure components is required during the planning phase of the IPT network deployment to identify the gaps in the current infrastructure to support the additional voice traffic on top of existing data traffic. After identifying the gaps, you need to make the appropriate changes in the network, such as implementing QoS in LAN/WAN, upgrading the closet switches to support QoS, and supporting the in-line power.

Legacy voice and data networks are migrating to new-generation multiservice networks. Multiservice networks require a set of technologies, features, and best practices to design a scalable and optimized infrastructure, which caries in parallel over the same IP infrastructure both real-time, delay-sensitive voice and video traffic and nonreal-time, delay-tolerable data traffic (i.e. FTP, e-mail, and so forth).

When you introduce real-time, delay-sensitive voice and video traffic into ensuring that your infrastructure is hierarchical, redundant, and QoS enabled, it becomes even more important to provide a scalable and redundant network infrastructure with fast convergence. Large network infrastructures use the access, distribution, and core layers at Layer 2 and Layer 3 for isolation, with redundant links and switches at these layers to provide the highest level of redundancy. This isolation helps you to summarize the IP addresses and traffic flows at different layers and troubleshoot the issues in a hierarchical manner when they occur.


For more details on the above network requirements as well as potential telecom issues read more of this article at Informit.


This was first published in June 2005

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