The Ultimate VoIP Solution

We asked top industry experts to design the perfect telephony system. Here's what they came up with.

June 1, 2005

8 Min Read
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Incredible Applications For Incredible Phones

What constitutes the ideal IP telephone? Mobility? Lots of buttons? Integration with enterprise applications? Everyone has their own opinion of what makes the perfect IP phone and VoIP implementation, but we've gone a step further. In this month's Convergence, we've enlisted the help of four experts to come up with the ideal IP phone and VoIP network architecture.

Together they've composed a list of requirements that should be on anyone's shortlist for desktop phones. They've also designed an elegant VoIP network that you can use as a template when planning your own VoIP deployment.

Not surprisingly, one of the features they flagged for the ideal IP phone was a large display. A decent screen makes it possible to view a corporate and personal phone directory that includes real-time presence information. A sizable screen also lets users run third-party applications. At a recent Cisco Systems partner conference, for example, I stumbled across one application that allowed users to control their conference room environment, giving them the ability to activate a projector, adjust the room temperature, or lower and raise the blinds at the touch of a button. Sure, you could run that sort of application on a PC, but not all conference rooms have a PC. They all have telephones, however.

INTO THE OFFICEIt's true that broader, mass-market applications could be created for those phones, but that won't happen anytime soon, in part because each manufacturer has its own development environment. This lack of interoperability narrows the market scope for applications and forces developers to recode software for each environment, which ultimately leads to higher prices and more limited choices. Third-party development kits from the likes of Millenigence or Citrix can be used to smooth over these differences, but not without adding cost and complexity to the IP telephony system.

As Art Wittmann points out in this month's Foundations (see page 8), the real difference between companies in the networking industry today isn't in their intellectual property, but in their execution of ideas that are already fairly widely understood. The same holds true for telephone-based applications. If all high-end phones from major telephony manufacturers can run hospitality and other vertical applications, then the real difference between those phones isn't really in the applications, but in the telephone's packaging and design.


If the industry is serious about making those silver-screened phones more than just eye candy, then it needs to work together to form a common development environment. Heresy? Hardly. The first steps toward common standards for IP phone applications have already been taken. The Wireless Markup Language (WML) used by the mobile industry for creating applications on mobile phones has been adopted by at least two IP telephony vendors: Avaya, in its new IP phones; and Siemens, in its OptiPoint phones.

But WML alone isn't enough. For one thing, Cisco still uses its own Cisco XML, not WML, on its phones, while Nortel Networks' applications require Citrix technology. What's more, as with the Session Initiation Protocol (SIP), vendors have written their own proprietary extensions to WML. Thus, while standardized core functionality is set, more advanced features such as enhanced scrolling are still specific to each environment. As long as those differences remain, display telephones may continue to gather a lot of foot traffic at trade shows, but they won't win much mindshare at the desktop.

By now it's become a mantra: The Session Initiation Protocol (SIP) is the future of VoIP. The vendors are saying it, and the network designers are building for it. Even Cisco Systems, the only major VoIP vendor not to offer native SIP client support, will add the capability to its next major release of Cisco Call Manager expected at the end of the year. All this begs the question, just what should network architects be considering when they evaluate an IP PBX?

To answer that question, we assembled a panel of leading VoIP architects and designers and asked them to compose a wish list of ideal telephony requirements (see "The Incredible Panel"). Together, the group mapped out exactly what the Incredible VoIP Architecture should look like. They defined the core of the SIP network--the call-stateful proxy--and prescribed the resiliency, scalability, and E-911 features that such a proxy should deliver. The panel also took into account the remote office, defining an integrated device that provides both remotely managed VoIP and the right mix of security functions. No VoIP solution would be complete without effective management, of course. The panel's ideal VoIP management solution not only integrates with the existing management infrastructure, but allows network architects to define global policies for the telecom network, as well as specify configurations for particular call servers.

As for the Incredible Telephone, our team eschewed the large color displays of high-end models where videoconferecing was concerned. "You don't get anything useful in interactive communications with a 4x7-inch display. You just get an expensive toy," says Brian Rosen, one of our panel experts. (Using the display for phone-based applications is another matter, however.) Our panel also wanted SIP phone sets that didn't use proprietary SIP extensions. Those phones should be able to fail over to a backup power supply or an alternative SIP proxy and offer better-than-PSTN voice quality.

In all, the Incredible VoIP Solution borrows elements from many of today's VoIP systems and mixes them with some features and functions not yet seen. The solution's fully distributed design can be seen on a smaller scale in ShoreTel's VoIP architecture, while the notion of a stateful SIP proxy capable of supporting tens of thousands of IP or analog endpoints is more reminiscent of Siemen's HiPath 7000 or Zultys Technologies' Enterprise Media Exchange server. In terms of diagnostic functions, many of these capabilities can be found in advanced management platforms such as that from Avaya. The emphasis on a single remote device at the remote office falls in line with Cisco's Integrated Services Router line, while Mitel Networks' 5230 IP Phone is probably the closest to the Incredible Telephone.Yet for all its similarities to the big VoIP systems on the market today, the Incredible VoIP Solution breaks new ground in many areas. Its fully distributed and open architecture is, if not unique, at least rarely offered in highly scaleable corporate IP telephony products. The extensive use of presence technology foreshadows the type of IP phones that will be possible in years ahead. Even minor details, such as improving reboot times by downloading configuration updates rather than the full configuration files, are something that many VoIP systems still lack today.

Executive Editor David Greenfield can be reached at [email protected].The Incredible VoIP Management System

The Incredible VoIP Management System should integrate with the general network management system, as well as provide the necessary tools to configure, manage, and troubleshoot a VoIP network. More specifically, the VoIP management system should use identities contained within the corporate LDAP database and the company's identity management solution (for example, Microsoft's Identity Integration Server). This simplifies the configuration of roles, access rights, and policies in the VoIP solution.

Telephony vendors tend to emphasize the benefits of treating the VoIP system as a single entity, but our panel favored a different approach. VoIP policies, such as those regarding dialing-plan information, should be expressed network-wide. However, configuration information is server-specific and requires the ability to alter port settings and configuration parameters individually for each server. Thus, as part of that configuration process, network managers should be able to place restrictions on what users can do. This includes limiting the use of voice, video, and data sharing or IM during a call; the number of users participating in a given call; and the number of simultaneous calls that a user can establish. The system should be able to determine the right codec to use on each call based on the available bandwidth and the type of user.The importance of the converged solution also means that management solutions should be able to detect a failing system and re-assign users before they notice. Problem detection requires that statistics be gathered directly at the end-client, particularly when it comes to detecting NAT problems. SNMP can be used for this task, but polling for SNMP traps across thousands of nodes won't scale well, notes panel expert Walt Magnussen. Better still would be to set thresholds at the devices using the RTP Control Protocol Extended Reports (RTCP XR) standard and alert the management station when those thresholds are crossed.

Finally, ensuring that the system will scale properly requires system capacity planning tools. In the TDM world, life was easy. "You had time slots or ports, and when you ran out you ran out," says Magnussen. Now with VoIP systems consisting of multiple servers, scaling has become more complex. It's simply not enough to add memory and processing to a user's proxy server. Depending on the VoIP configuration, those same variables may need to be tweaked elsewhere, such as at proxy servers responsible for routing traffic, location servers, conference servers, redirect servers, and registration severs. Layers two and three parameters such as QoS settings and bandwidth allocation may also need adjusting.

The Incredible VoIP Architecture   Also see the Online Extra, The Incredible SIP RFCs

The Incredible Panel

The Incredible Remote Office

The Incredible Telephone

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