Videoconferencing systems, which traditionally used dedicated ISDN lines, require six data channels (or B channels) at 64 Kbps. That translates to 384 Kbps, though this requirement can vary. Talking heads can get by with 128 Kbps, but a high-quality call can require 500 to 768 Kbps.
Streaming-media technologies serve on-demand and live video for corporate communications, promotion, sales and training. How tightly the video codecs compress video data for transmission dictates the streaming bandwidth requirements. Codecs with tight compression algorithms, such as RealNetworks' RealMedia, use as little as 20 Kbps of bandwidth. But high-quality video and other corporate LAN communications generally use MPEG standards for MPEG-1 and MPEG-2. This quality ranges from 30 frames per second for full-motion video to 60 interlaced fields per second to accommodate broadcast video.
MPEG-1 can take up to 1.5 Mbps per stream. MPEG-2 generally requires 2 Mbps to 6 Mbps but can need as much as 40 Mbps. MPEG-4 calls for less than its predecessors and targets the low bandwidth requirements on the Internet along with Apple Computer, Microsoft and RealNetworks. It needs 64 Kbps to 4 Mbps.
Traffic Prioritization
Bandwidth alone won't ensure the smooth delivery of real-time voice and video packets, especially considering IP's best-effort nature over Ethernet. You'll likely need additional guarantees under heavy loads, so consider upgrading to Layer 3 switches and traffic prioritization strategies such as RSVP (Resource Reservation Protocol), DiffServ (Differentiated Services) and MPLS (Multiprotocol Label Switching).
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