Cisco Brings HD Video To WLAN Clients With VideoStream Technology
January 21, 2010
Cisco Systems is showcasing its new VideoStream technology as a method to push high-definition video to mobile users across its enterprise WLAN architectures. By pulling together several components in both the wireless controller and deployed access points, Cisco is promising video over WLAN without the overhead currently associated with multi-cast video streams. Cisco's VideoStream technology will be included as a no-charge option in the upcoming 7.0 release for Cisco's wireless controllers and access points. Release 7.0 is currently in beta testing with a planned availability in May 2010.
In a wired network, multicast makes sense: a single copy of the video stream is delivered from the media source to the multi-cast router nearest the video client. Clients request the video stream from the multi-cast router. Multi-cast reduces the number of video streams across the core and distribution infrastucture, reducing bandwidth requirements and congestion. The result is less packet loss and delay. Multicast video streams in Cisco AP/Controller architecture present a unique problem. On the wired network, APs can subscribe to a multi-cast group, but the multi-cast traffic is then broadcast over the air to all devices associated with the AP. This broadcast not only consumes a significant portion of the over-the-air bandwidth, but it also does not take into account the types of the connected devices, as well as not allowing the error correction features that make up the core of the 802.11 standards.
As we learned with the increasing capacity of Ethernet from 10 Mbps to 10Gbps, adding more bandwidth to the network doens't always solve performance issues. 802.11n, which can achieve 100 Mb/s or more, has more bandwidth than 802.11 a/b/g. Throughput is only one factor in pushing applications on to WiFi. As more mobile users make wireless the primary form of access to enterprise networks and video use increases, look for more compelling solutions like Cisco's VideoStream from other infrastructure and video distribution vendors to be rolled out in response.
Cisco's VideoStream technology uses a combination of solutions to deliver manageable video to wireless clients. By utilizing the Reliable Multicast protocol, stream prioritization and resource reservation control, Cisco believes that it has solved the Video over WLAN problem. When enabled, the wireless controller passes the stream to access points that have subscribed to the multi-cast stream. The access points then convert the multi-cast streams to unicast and send the video to the specific wireless clients that subscribe to the video. Stream prioritization places video before other applications; RSVP reserves bandwidth for the video. Both ensure that the video will have the capacity and performance characteristics required to deliver decent video. Of course, streaming video is bandwidth intensive, so admission control is applied at the AP, ensuring a given access point is not overwhelmed with more wireless clients than it can support.
Based on third-party testing cited by Cisco, enabling the VideoStream option significantly improved the WLAN's Media Delivery Index (MDI), a metric that combines delay factor and media loss rate to determine video streaming quality. Cisco also notes that while it recommends only using 802.11n for HD video, its technology will work with older 802.11a/b/g access points, albeit with lower quality video streams.