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Everything On The Network

Like it or not, AV and IT increasingly share the same network. For AV pros, that's both a problem and an opportunity.

“This allows you to see how much bandwidth is available to upload and download from your connection,” Pfleiderer says. “It's pretty handy to see how much bandwidth is actually on a connection. Speakeasy is one I like to use.”

Another variable to be aware of is that some networks, such as consumer-class cable and digital subscriber line (DSL), are asymmetrical: Their download speeds are much faster than their upload throughput. That's something to consider if the flow of AV traffic goes in both directions, or if some of the users are telecommuters on a cable or DSL connection.

Even on an enterprise-grade LAN or WAN, bandwidth-intensive AV traffic can quickly take its toll. The typical HD (MPEG-4) video stream requires 18 to 20 MB/sec throughput rates,” says ViewSonic's Ornstead. “While this seems low compared to the 100-MB rate of standard Ethernet, multiple data streams may cause the video transmission to be interrupted.”

The budget factor

A major reason for the increase in networkable pro AV gear is that it's usually cheaper to piggyback the audio and video traffic on the existing IT infrastructure than it is to install and maintain a separate network. Even so, there are additional costs to consider. An obvious one is extending the LAN so that there's a jack next to the projector, loudspeaker, or display.

If the AV traffic pushes the LAN or WAN to its limits, the network may need to be upgraded. If the network is leased from a third party, the upgrade could mean paying for a bigger chunk of bandwidth.

“For streaming a lot of video and audio, the costs could be higher if the campus meters bandwidth consumption,” Pfleiderer says. “Storage costs for storage area networks (SANs), or for video files stored on the server and delivered via downloads, could result in additional licenses or costs per download. This would depend on how much the campus has to recover costs for large downloads or live streaming. If you need to stream globally, then costs for commercially provided edge servers might become part of the costs for overall network use.”

According to one systems integrator, content distribution network space storage runs about $40/GB, and delivery ranges from $3 to $10/GB, depending on contract and volume.

Worlds apart

In some cases, it may make sense to maintain separate networks for AV and IT traffic, such as when there's no practical or cost-effective way to accommodate their bandwidth and latency needs within the same pipe. However, using separate networks doesn't necessarily mean two physically different sets of infrastructure. For example, one alternative is subnets, which are networks within networks, just as the Internet is a collection of multiple networks. The boundaries are maintained via separate IP addresses for different devices on the network.

Subnets also can be shared — as was the case at Cornell, where the AV department was on the same subnet as the help desk and some general computer users. At certain times of the day, there wasn't much elbow room. “We found that it was much more manageable to set up a smaller subnet and put all of the videoconferencing and streaming equipment on it,” Pfleiderer says. “We not only gained better control of the bandwidth, but it added stability to the video signals. I suppose that just having less competition for available bandwidth on the smaller net did the trick. Besides, the smaller subnet was easier to manage because we knew who or what was on the dedicated subnet, so if there are problems, it's much easier to troubleshoot and identify where the difficulties are.”

Indeed, ease of management is one reason why it may make sense for AV to carve out its own corner of the world. “We can provision the network switches for optimal delivery of video, which might not be easy in a larger, more dynamic subnet that's chiefly concerned with general computing and not video distribution,” Pfleiderer says.



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