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November 2007 | Volume 10/ Number 11
Tech Score

Can IP Telephony Applications Live in a “Virtual World”

All things old truly do become new again. In 1967, IBM introduced their System/360 model 67. This model utilized virtual memory along with an operating system called CP-67 which ultimately evolved into a virtual machine (VM) operating system. Today, virtual software has become a hot topic again as data centers and large enterprises face an ever increasing shortage of power, cooling, and space. In short, “server sprawl” has reached critical mass and technologists are looking at virtualization as a key to solving the problem.

The gap between CPU processing available versus what is actually utilized continues to grow (see Figure 1). Despite the increasing costs of adding more and more processing capacity, typical server processor utilization reaches a meager 10-15%. Virtual software can take advantage of this widening gap and allow significant cost savings by reducing overall server count (in some cases by a factor of 20).

Does virtualization offer similar opportunities to IP telephony services without compromising security, reliability and performance?

First let’s deal with the security issue. In a physical machine network, the machines are separated and cannot directly interfere with each other except over the network. In a virtual machine network, partitions can be used in much the same way to create a logical separation and isolate any intruding Mal-ware. This hardware/software abstraction is a great benefit to telephony service providers as it prevents potential service interruptions to mission critical functions of the application.

Next is the robustness of virtualization and its ability to deliver a five 9’s fault tolerant environment. At the surface, virtual software does not appear to increase or decrease the system reliability. Any application or driver faults that might normally cause a failure on the physical hardware will still fail in the virtual machine. However, the ability to isolate VMs can provide redundancy in the event of an actual hardware failure and increase system reliability.

Finally we must address the overall performance impact of virtualization. Introducing an abstraction layer between the physical machine and the operating system will inherently reduce system performance. While such advancements as Intel’s hardware based Virtualization Technology (VT) help to improve performance, the application is still likely to suffer some performance impact.

One company that is making real headway in the area of IP Telephony and virtualization is Aculab ( Aculab offers VoIP Service Providers and Telecom Equipment Manufacturers industry leading solutions. Their virtualization-ready Prosody-S product is one of the most comprehensive Service Deployment Platforms (SDPs) currently available on the market. According to Herman Abel, Aculab Product Manager; “For contemporary VoIP telephony, high service continuity is the paramount objective and virtualization provides high resilience for system component failures. Two special conditions shall apply in this case: presence of redundant elements, which means that there is a need to introduce alternative hardware units to allow protection switching, and spare media processing capacity to handle all active calls in case of a hardware element failure. Finally, virtualization brings the best performance for the buck. As the entire telephony industry experiences ever-decreasing price per call minute and eroding ARPU, services providers are in a constant attempt to improve their cost efficiency. Based on Service-Oriented Architecture (SOA), Prosody-S offers the most comprehensive set of media processing and call control functionality that delivers all the benefits discussed above when deployed in a virtualization-based environment.”

Probing a bit further, I wondered how Prosody-S might better leverage virtual technology in the future. “The next release of Prosody S will support ‘distributed architecture’, which allows linear scalability, resilience, remote OAM&P and improved performance,” added Herman. “The product will have a special license management scheme to allow operation in a virtualization -based environment.”

Final Score

While many end users readily admit that installing a mission-critical IP telephony application on a virtual server seems risky today, the consolidation demands will make this a requirement in the future. The advancements in processor power, I/O bandwidth, and storage capacity will eliminate the perceived risks associated with IP telephony applications living in the “Virtual World”. IT

Jeff Hudgins is VP of Engineering at Alliance Systems.

For more information, visit the company online at

» Internet Telephony Magazine Table of Contents

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