Network Management Strategies for the CIO
"Speed is not really the big problem to solve. It used to be speed. Going back even further, it was security," said Paul DeBeasi, senior analyst at Burton Group. "Well, [wireless networks] are pretty secure now, and they're pretty fast now…. It's all about robustness and making it more like a wired network experience, so that's why you're seeing things like this VideoStream technology."
The ratification of
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802.11n solved one of the first challenges of delivering video over wireless LAN -- speed. But now the inherent challenge of video over WLAN lies in the way packets are delivered over the wired and wireless networks, DeBeasi said.
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As enterprises that have tried delivering video over wireless LAN via multicast have learned, the protocol ruins the experience for everyone -- even for users with fast-performing clients receiving strong wireless signals, according to DeBeasi.
"The rule and the standard [for multicast] is you have to transmit [packets] at the lowest common rate so that you know everyone is going to get it," he said. "It means everyone will receive that multicast really, really slowly [with poor quality]."
Cisco pushes unicast onto APs for video over wireless LAN
Vendors have been racing to find a way for unicast -- a protocol that sends packets directly to each client at optimal speed -- to work wirelessly, DeBeasi said. Smaller vendors such as Ruckus Wireless and Aruba Networks have released unicast solutions with their own differentiators.
Cisco is the latest to join the party, offering a solution that converts the one-to-many style of multicast into more video-friendly unicast in the 7.0 release of its Unified Wireless Network software. But what Cisco has done differently is push that conversion to the very edge of the network, according to David Stiff, the company's product marketing manager.
Although automated unicast solves one problem, converting unicast to multicast can put a burden on wireless LAN controllers, Stiff said, taking a thinly veiled shot at Aruba's strategy of automated unicast at the controller. In December, Ruckus patented its algorithm for intelligent multicast to unicast conversions -- metering out multicast where quality wouldn't suffer so that there is less strain on the network with fewer streams.
"If you're on the network side and try to take the video stream and send it directly to each client on the network, you get into a situation where every client wants to add more bandwidth," Stiff said. "If you have a huge network, you could have 10,000 individual streams trying to be sent out of one box."
Instead, Cisco's new Multicast Direct feature, part of VideoStream software, divvies up the work and puts the burden of video over WLAN unicast conversion and distribution onto access points (APs). Instead of one controller handling 10,000 streams, for example, 100 APs would handle about 100 streams each.
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"It's distributed across a lot of different access points, so many hands make easy work," DeBeasi said. "The advantage of pushing it out to the very edge of the network is you reduce the amount of traffic that flows over the [wired] network."
Because unicast requires acknowledgment of receipt from each client, Multicast Direct conversely makes intelligent decisions about where video shouldn't go -- that is, to access points that get no requests -- to conserve bandwidth.
Meanwhile, the software update also integrates other new features to enhance quality of experience for streaming video over wireless LAN, delivering a more "holistic" solution than competitors do, DeBeasi said.
Stream Prioritization allows administrators to designate additional levels of quality of service, while Resource Reservation Control monitors APs' capacity and denies new video requests if they are overloaded.
Older and more familiar Cisco features also make a comeback, including ClientLink, which boosts 802.11 b/g clients' performance, and Band Select, which will automatically put video on the channel that has available bandwidth.
Video over wireless LAN may require buying more APs
At the Rochester Institute of Technology (RIT), IT staff deployed a Cisco 802.11n wireless LAN in August but realized that if they were to run video over WLAN, they needed to change their design, according to Greg Gardner, manager of network communications.
Once large-scale video over wireless LAN became a goal, RIT recognized that it would need to install more APs with greater density in high-usage areas, such as classrooms and student centers, Gardner said. Instead of having one AP per 5,000 square feet or more, each access point now covers an average area of 1,400 square feet -- or less in extremely dense areas.
"We needed to provide pervasive high-bandwidth wireless that would meet not only the current needs but would also be something that would meet the needs as they developed in our very high-tech and bandwidth-hungry population," he said.
Although not every enterprise will need to buy more APs to execute video over wireless LAN, DeBeasi said, it will be a requirement for those that choose to design their networks "aggressively," deploying as few APs as possible for an ancillary wireless network.
Despite Cisco's hammering on Aruba's solution, unicast conversion at the controller isn't necessarily a death knell for video over wireless LAN, DeBeasi said, particularly if the wired network supports a relatively low amount of traffic and only a little video over WLAN is planned.
"[Video] is a more stringent requirement on your network," he said. "If you did a good job designing [your wireless LAN] densely with great coverage … you're probably going to be fine."
Let us know what you think about the story; email: Jessica Scarpati, News Writer
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