VoIP Telephony and Infrastructure II

Endpoints (User Agents)
In a phone system, an endpoint on the network was known as a terminal, reflecting the fact that it was a slave to the switch or call-control server. But today’s endpoints may possess much more intelligence, thus in the SIP world the term User Agent is preferred. This could be a hardware IP telephone, a softphone, or any other device or service capable of originating or terminating a communication session directly or as a proxy for the end user.

Softphones
With the advent of VoIP technology, users are able to break free of classical physical restrictions of communication, namely the special-purpose telephone terminal. A softphone is a piece of software that handles voice traffic through a computer using a standard computer speaker and microphone (or improved audio equipment that is connected through an audio or multimedia card). Softphones can emulate the look and feel of a traditional phone, using the familiar key layout of a traditional phone and often even emulating the DTMF sounds you hear when you dial a call. Or it may look more like an instant messaging (IM) client, and act like audio chat added to IM.

In fact, a softphone doesn’t even need a computer microphone or speaker: my favorite doesn’t need to send media through the computer at all in telecommuter mode - it just uses H.323 signaling to tell my media server which PSTN number (or extension) to dial for sending and receiving the audio. This lets me turn any phone into a fully featured clone of my work extension without regard to QoS available to me on my Internet connection.

Because a soft phone resides on a PC, the principle of logically separating voice and data networks is defeated as the PC must reside in both domains. You will need to consider this trade-off as you design appropriate security policy for your VoIP  network, although the long-term trends favor voice-data integration, so at best maintaining physical separation can be only a temporary strategy.
Consumer softphones have exploded over the past few years and nothing is hotter than Skype in that space. Skype is the brainchild of the people who brought us the Kazaa file sharing framework. Utilizing peer-to-peer technology and an encrypted signaling and media channel, Skype has proven to be both easy to set up and use securely by end users, while simultaneously being a thorn in the side of network administrators. Because it aggressively jumps past firewalls to create call traffic, it is considered to be a threat by many enterprise security groups.
One of Skype’s major enhancements over instant-messaging-based voice is its superb codec, which is actually better than that used within traditional telephone infrastructure. This provides superior call quality when contacting other Skype users. Another major benefit of Skype is the ability to reach any phone in the PSTN by way of SkypeOut gateways. With its PSTN gateway, Skype has become an attractive alternative for small overseas call centers and other Internet businesses.

IM Clients
Instant messaging is perhaps the dominant means of real-time communication on the Internet today. IM?s roots can be traced back to the Internet Relay Chat (IRC) networks, which introduced the chat room concept but did not track online presence and never reached the popularity of IM. Just as IM is the next logical step from IRC, voice chat is the next leap from text-based chat. Most of today’s most popular IM clients have included voice functionality, including AOL’s Instant Messenger, Yahoo! Messenger, and MSN Messenger. Skype took the opposite approach and created a chat client that focuses on voice as the star and text chat as an afterthought. Even Google jumped aboard the IM bandwagon, releasing Google Talk. Let’s take a look at these clients to see what makes them similar, and what makes them different.

AIM, AOL’s IM service, surely wasn’t the first on the scene, but it has the largest base of users. Initially AIM was limited to users of the AOL Internet service, but eventually it was opened up to the Internet as a whole. With the addition of a proprietary voice capability in late 1999,AOL was a VoIP pioneer of sorts. (although voice chat was first available through Mirablis?s ICQ). Yahoo! Chat jumped aboard the voice bandwagon soon after, and Google’s more recent client has included voice from the beginning. In 2005,Yahoo announced interoperability with Google and MSN (who also has a voice chat plug-in for messenger that is also used with its Live Communication Server product). In addition, Microsoft?s popular Outlook e-mail client (and entire Office suite in the case of LCS) can be linked to Microsoft Messenger. Also worth mentioning is the Lotus Domino IM client that competes with Microsoft LCS in the enterprise instant messaging (and presence) space, as well as Jabber, which can be used to tie together both public and private IM services using the XMPP protocol.

Google Talk is the newest comer to the IM game. Though Google Talk is still in its infancy, it stands to succeed due largely to a philosophical stand point, embracing open standards over proprietary voice chat. Google Talk aims to connect many different voice networks over a series of peering arrangements, allowing users to minimize their need to run several IM clients. Like Skype, Google seeks to bridge traditional phone calls with Internet telephony, promising to federate with SIP networks that provide access to an ordinary telephone dial tone. Google recently released a library called libjingle to programmers, allowing them to hack new functionality into Google Talk. It will be interesting to see where Google takes Google Talk in the future.

Video Clients
Most of us can probably think back and recall seeing episodes of The Jetsons when we were younger. Or pictures of the AT& T PicturePhone from the 1964 World’s Fair. Movies have all but promised these devices to be a staple of every day life in the future. And for decades, the video conference has been pushed by enterprises seeking to save money on travel (though investments in video conferencing equipment tend to sit around gathering dust). Live video on the Internet has its adherents, and today we see yet another wave of marketing aimed at the business use of video. So, will video finally take off around VoIP just like audio, or is there something different going on here?

The video phone has been tomorrow’s next big technology for 50 years but the issue has been more sociological than technological. Certainly, popular instant messaging clients have included video chat capabilities for some time now, although each client typically supports only video between other users of the same client or messaging network. And although it always gives me a kick to see someone else announcing that they’ve solved the gap with technology, the point is well taken that video is here to stay in VoIP systems - even if it doesn’t get as much use as VoIP.

The latest on the video bandwagon is the Skype 2.0 release. At only 15 frames per second and 40 to 75 kbps upload and download, Skype Video works well on a standard home DSL line or better. Other popular IM clients with video include Microsoft’s Messenger and Yahoo Instant Messenger. AIM now offers video as well.

H.323based IP videoconferencing systems have been available in hardware and software from many sources for almost a decade at this point, so there’s no shortage of vendors in this space. And SIP video phones are available from many of these same vendors and from startup companies in the SIP space.

Wireless VoIP Clients
Over the past few years, an explosion of wireless VoIP solutions has hit the marketplace. Most of these solutions are immature and if broadly deployed can completely overrun the available bandwidth on 802.11b (or g) networks that were not engineered for high-density voice, even with QoS prioritization. And although 802.11a networks can handle higher wireless VoIP densities, they present other backward-compatibility issues of their own. And we haven?t even gotten to the security issues yet! Still, the promise of WiFi VoIP is tantalizing, and most enterprises that have deployed VoIP solutions seem to have experimented with it. The idea of a combined cellphone/ WiFi phone (and maybe PDA too) seems just too compelling to ignore, even if power consumption issues sideline keep the concept sidelined in the short term.

This entry was posted on Sunday, August 31st, 2008 at 4:58 pm and is filed under IT. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.