HP ProLiant 1600 Video Streaming Technology - Page 17

ECG068/0798 WHITE PAPER (cont.) 1...7 Broadcasting, on the other hand, is a special case of multicasting that delivers a single stream simultaneously to all network clients. This is the method used for example, for live broadcasts of executive presentations or new product announcements to all corporate employees worldwide. All users on the network can view the broadcast at the appointed time. On the Internet, multicasting is referred to as "IP Multicasting". Since its use has the potential to significantly reduce congestion on the net there is a lot of activity underway to support it. Originally intended for corporate Intranets, the Internet will support it soon as part of the new IPv6 standard. It will require multicast-ready routers, of which there are many already on the market. LANs/Intranets Many of today's Enterprise networks were not designed with video transmission in mind. The following is a discussion of various network types and their suitability for video streaming. Shared Non-Switched Ethernet Video streaming can be problematic in a shared network environment such as a 10BaseT shared Ethernet LAN which typically handles intermittent bursty data traffic. This is partly due to two characteristics of Ethernet. First, Ethernet works as a contention-based, or collision-avoidance, system. Each node on the shared section of the network wanting to transmit data listens for collisions with other nodes sending data. If a data collision occurs, all contending nodes back off and re-transmit after a random delay. This enables shared Ethernet to support a large amount of bursty data traffic corresponding to multiple shared applications and devices such as: modem communications, sending and receiving faxes, printing, accessing corporate databases such as phone directories and group calendars, internal and external e-mail, file transfers, and last, but certainly not least, Internet access. However, this coexistence with other network traffic can be disruptive to the smooth playing of real-time video. Non-video-data traffic peaks, for example, could result in lost frames or even stoppage of the video. In order to handle the demands of video, existing LAN infrastructure may need some modification. Ideally, this can be done without significant cost impact to the customer's investment in existing LAN infrastructure. Some possibilities discussed below include the use of switched Ethernet hubs to provide dedicated bandwidth to a few video stations, Fibre Channel local area digital network, or the use of high-bandwidth ATM for network backbone or long-haul transmission. Switched Ethernet A switched Ethernet hub can provide dedicated bandwidth for real-time video to individual desktops or subnets that need it. Generally the switch has a high-speed-e.g., 100Mbps-link to the video server, and multiple lower speed-e.g., 10Mbps-output ports. The switch may also support an optional high-speed link-e.g., Fast Ethernet, ATM, and FDDI-to the corporate backbone. Video Server 100Mbps Switched Ethernet Hub Backbone Dedicated 10 Mbps Video Stations