June 2002

BY STEFAN KARAPETKOV

With quality of service and reliability consistently improving, more companies are replacing their circuit-switched PBX systems with more advanced and cost-effective IP telephony implementations.

Cahners In-Stat recently reported the three-year old Voice-over-IP (VoIP) handset market reached $1 billion in 2001 and estimates the market for IP voice equipment will quadruple by 2006.

Whether a company is moving to a new building and needs to cut operational costs or needs to increase connection efficiencies between smaller or remote offices, installing an IP phone brings many benefits.

In addition to creating just one communications infrastructure to maintain and administer, an upgradeable IP phone can be connected to a variety of voice communication systems and unplugged and connected to the LAN in another room, floor or building. For companies with teleworkers and/or remote offices that have VPNs to headquarters, an IP telephony solution is an especially attractive offering, as no additional teleworking hardware and software is necessary nor is a second analog line required for signaling.

However, with an influx of IP phones to choose from, how can companies be sure hard-to-come-by dollars are invested in the right phone device � a phone device that will help realize the full capabilities and benefits of an IP system?

There are a number of points to consider before implementing IP phones to ensure optimal voice quality and data transfer:

• A choice IP phone will have a second Ethernet port and a true LAN switch built in, ensuring that PC traffic does not interfere with voice traffic.
• Heavy data traffic through the switch can negatively affect voice quality. To avoid this, choose an IP phone with the ability to switch LAN traffic and support Virtual LANs and Quality of Service.
• A phone with a jitter buffer, powerful processor and short voice frames (20-30ms) also helps improve voice quality.
• Select an IP phone that has multiple protocol support (SIP, H.323, H.450, proprietary feature-rich protocols, etc.) and is easily upgradeable. This will protect the initial investment should future-developed protocols become a requirement.
• Consider an IP device that supports standards for management and operation (DHCP, SNMP, HTTP, and SNTP) and will integrate with existing management systems.
• For larger installations, it is important to evaluate an IP phone for Power over LAN (PoLAN) capabilities. PoLAN allows for power hub connections to Uninterrupted Power Supply (UPS), making the phones operational even when a power failure occurs.
• Choose a manufacturer with global availability and distribution capabilities. This eases international expansion and eliminates the need to search for another manufacturer abroad.
• A warranty is important. Be sure that the manufacturer offers an extended warranty. A 90-day warranty is common, but 1-year warranties are available as well.

There are many components involved in an IP telephony system. An IP phone that improves voice quality, has fast call setup and a single line to the desktop is just part of a successful IP PBX installation. But having the right phone in place means being one step closer to IP telephony triumph.

Stefan Karapetkov is group manager � Product Management � Telephones and Soft Clients at Siemens Enterprise Networks. Please visit their Web site at www.siemens.com.

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