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What Is VoIP

by Ted Wallingford
Voice over Internet Protocol (VoIP) is the family of technologies that allow IP networks to be used for voice applications, such as telephony, voice instant messaging, and teleconferencing. VoIP entails solutions at almost every layer of an IP network--from specialized voice applications (like Skype) all the way down to low-level quality measures that keep those applications running smoothly.

In this Article

  1. The VoIP Technology
  2. Why VoIP Now?
  3. VoIP in Action
  4. How IP Telephony Fits In
  5. VoIP-Based Services
  6. What's Next for VoIP?

Unless you've been sleeping under a very big rock for the last year, you've certainly heard the phrase "Voice over IP" uttered. Perhaps you've seen those hilarious Vonage commercials that feature painful and embarrassing accidents caught on tape, promising to let you dump your local phone company in order save big on your phone bill. You may also have seen the Cisco telephones that are curiously inserted in prime-time shows like 24.

What is all the hubbub about, anyway? Why, VoIP, of course! VoIP, the fabulous secret ingredient in Vonage, Skype, Cisco CallManager, and a host of other revolutionary technology products you may have already encountered on TV, in the news, or in person. But what makes these products so revolutionary? What is it about VoIP that is such a big deal?

The VoIP Technology

Voice over Internet Protocol is a family of technologies that enable voice communications using IP networks like the internet. Inventive developers and entrepreneurs have created an industry around VoIP technology in its many forms: desktop applications, telephone services, and corporate phone systems. VoIP is a core technology that drives everything from voice-chat software loaded on a desktop PC to Mac full-blown IP-based telecommunications networks in large corporations. To the Wall Street speculator, VoIP is a single technology investment with many revenue streams. To the enterprise network engineer, it's a way to simplify the corporate network and improve the telephony experience for users of the network. To the home user, it's a really cool way to save money on the old phone bill.

But how? What makes VoIP do all this awesome stuff? Read on.

Why VoIP Now?

The concept isn't actually that new: VoIP has been touted as a long-distance killer since the later 1990s, when goofy PC products like Internet Phone were starting to show up. But the promise of Voice over IP was lost in the shuffle of buggy applications and the slow-to-start broadband revolution. Without broadband connections, VoIP really isn't worthwhile. So early adopters of personal VoIP software like CUSeeMe and NetMeeting were sometimes frustrated by bad sound quality, and the first generation of VoIP products ultimately failed in the marketplace.

Fast forward to Fall 2005. Suddenly, everybody is talking about VoIP again. Why? There may be no greater reason than the sudden success of a freeware VoIP chat program called Skype.

Switching to VoIP

Related Reading

Switching to VoIP
By Ted Wallingford

VoIP in Action

Skype is an instant messaging program that happens to have a peer-to-peer (modeled after Kazaa) global voice network at its disposal, so you can use it to call people on your buddy list using your PC or Mac. All you need is broadband, a microphone, and a pair speakers or headphones. Voice calling alone doesn't set Skype apart from other IM applications like AIM or Windows Messenger--they also support voice. But Skype supports voice calling in a way that those applications can only dream of: Skype works in almost any broadband-connected network environment, even networks with firewalls that often break other voice-chatting apps. Plus, Skype's variable-bitrate sound codec makes it less prone to sound quality issues than its predecessors. In a nutshell, Skype just works. Perhaps that's why Skype's official slogan is "Internet Telephony that Just Works."

The world has noticed. 150 million downloads later, Skype now offers the ability for its users to call regular phone numbers from their PCs, a feature known as SkypeOut. Skype also offers a voicemail service and can route incoming calls to a certain phone number right to a user's desktop PC. There's even a Skype API that allows Windows and Mac programmers to integrate the Skype client with other applications. Videoconferencing add-ons, Outlook integration, and personal answering machines are just some of the cool software folks have developed using the Skype API.

How IP Telephony Fits In

But Skype can't take all of the credit for the recent growth of Voice over IP. A number of enterprise telephone system vendors have heavily promoted what they call "IP telephony"--the art of building corporate phone systems using Ethernet devices and host-based servers instead of old-fashioned PBX chassis and legacy technology. Cisco Systems and Avaya were two of the earliest players in the VoIP-phone-system arena, and their stubborn support of IP-based voice technology is beginning to pay off. More and more corporate customers are integrating IP phones and servers, and upgrading their IP networks to support voice applications, interested primarily in the productivity boost and long-term cost savings of running a single converged network instead of maintaining legacy voice equipment. This transition is a lot like the move from mainframes and minicomputers to personal computers a generation ago.

On two fronts--the corporate phone system and that of the home user--VoIP is transforming the global communications matrix. Instead of two separate notions of a global network (one for voice calling and one for Internet Protocol), a single converged network is arising, carrying both voice and data with the same networking protocol, IP. Steadily, corporations and domestic phone subscribers are migrating their voice services from the old voice plane to the new one, and next-generation, IP-based phone companies have rushed in to help them make the move.

Asterisk: The Future of Telephony

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Asterisk: The Future of Telephony
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VoIP-Based Services

By now you've probably seen ads for companies like Vonage and Packet8. These services promise ultra-cheap voice calling service via your broadband internet connection. Some offer calling packages as low as $9.95 per month. Their secret weapon is VoIP. Voice over IP service providers use the internet to carry voice signals from their networks to your home phone. Because VoIP telecommunication isn't regulated the way traditional phone line telecommunication is, VoIP providers like Vonage can offer drastically lower calling rates.

The catch? You've got to put up with the occasional hiccup in your voice service, caused by the one thing legacy telephone technology has built-in that VoIP doesn't: guaranteed quality. Because VoIP uses packets to transmit data like other services on the internet, it cannot provide the quality guarantees of old-fashioned, non-packet-based telephone lines. But this is changing, too. Efforts are underway on all fronts (service providers, Internet providers, and VoIP solution makers) to adapt quality-of-service techniques to VoIP services, so that one day, your VoIP calls may sound as good as (or better than) your regular land-line calls.

Today, if you want to build a fully quality-enabled private VoIP network, you can. Cisco, Foundry Networks, Nortel, and other network equipment makers all support common quality-of-service standards, meaning corporate networks are only an upgrade away from effective convergence of voice and data.

But it will be quite some time before the internet itself is quality-enabled. Indeed, the internet may never be fully quality-enabled. This hasn't stopped enterprising network gearheads like me from trying to connect calls over the internet, of course. Hey, if Skype works so well, why can't corporate phone calls? Enterprise phone administrators have found that it is actually very easy to equip mobile users with VoIP phones to place calls on the company phone system by connecting to it over the internet--from hotel rooms or home offices--but the quality of these calls is sort of hit or miss, like a cell phone when you drive through a "dead zone" in the cell network.

What's Next for VoIP?

A host of brand new, VoIP-enabled cell phones will soon be ready for action. Imagine driving to work, receiving a call on your cell phone from a client, and then continuing that call on the corporate Wi-Fi network as you walk into the front office. all without any interruption to your call-in-progress. The cell network will just "hand off" the call to your Wi-Fi network. This sort of technology exists today, and will be a commonplace feature of corporate phone systems in years to come.

Cost savings, uber-slick telephony features, network convergence--VoIP is the technology at the root of all these trends, and you should expect to see a lot more news about VoIP in the coming months and years. If you haven't used Voice over IP products yet, try out a broadband phone service like Broadvox Direct or Vonage, and download a copy of Skype or the Gizmo Project, two excellent VoIP PC calling applications.

To learn more, you can visit VoIPFan.com or browse O'Reilly's growing selection of books about IP telephony, including the book that's been dubbed the "Voice over IP of reason:" Switching to VoIP.

Ted Wallingford is lead consultant and co-founder of Best Technology Strategy LLC, and is the author of O'Reilly Media's Switching to VoIP and VoIP Hacks.

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