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Understanding SIP

Initiation is SIP's middle name ? it's also what AV pros can expect to go through over the next few years.

For example, SIP AV equipment can work with infrastructure such as Microsoft's Office Live Communications Server 2005, which registers endpoints and enables features such as presence. (Tandberg's MXP video endpoint is one example of a SIP-based AV product that works with Microsoft's server.) So during a conference, an attendee could open a document and highlight the author's name to pull up her presence information, such as whether she's on the network.

If she is, the attendee then could click on her name to establish a connection with her. How that connection is established depends on, for example, whether she logged on that morning and indicated that she's available for videoconferences or just phone calls. The upshot is that the conference attendee doesn't have to wonder whether she's around or wasting time figuring out the best way to contact her. Instead, the network makes those decisions automatically, behind the scenes.

“It puts the recipient in charge of the types of communications they get,” says Ditech's Hawrylyshen. “I could say, ‘I don't want videoconferences with Bob because we don't get along very well or because he's too far down the org chart.'”

Those features were a large part of SIP's appeal for MaRS. “Our Holy Grail in all of this was SIP,” Smith says. “Our primary focus was to build an infrastructure that was about understanding who's on the network and how to connect to those people easily.”

SIP also can simplify things for both users and integrators. For example, suppose that there's a videoconference involving multiple displays in each room. “In H.323, it's nearly impossible to get that all set up right,” says Cisco's Jennings. “With SIP, it's a lot easier. SIP is set up to deal with things such as lots of screens across a single connection.”

SIP also can accommodate different user capabilities. “If you're calling a room that has only one screen, the SIP system could negotiate and use only the center screen,” Jennings says. “The user wouldn't configure that manually.”

Another reason why it's important to understand the myriad of ways that SIP-based AV equipment can tie into telecom and IT infrastructure: It's an opportunity to provide additional features and services, which in turn add value in the client's eyes.

“They can say: ‘You want to do these five different things. I can make them all work together,'” says Tandberg's Lessman.

One aspect that doesn't require much additional knowledge is the network. That's because SIP doesn't require a particular network technology, such as asynchronous transfer mode (ATM) or frame relay. So network issues such as bandwidth, latency, and jitter depend on the needs of the AV application rather than on SIP.

However, SIP does impact the network in one key way: It's more efficient than many legacy protocols, which is a plus because bandwidth isn't free. “An H.323 call can have up to 20 percent overhead,” says Polycom's Smith.

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