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58 Chapter 3
m Windows can cause lighting problems. For more control, you should be able to draw the
blinds and supplement room lights with a portable lighting kit that can be quickly set up
for a live session.
Step 2: Prepare the Network
Check that there is an Ethernet connection to the classroom or lecture hall where the live
broadcast is to take place. Install, repair, or replace cables and connectors as needed, using
high-quality materials.
Bear in mind that streaming—especially live streaming—can make heavy demands on
network resources, especially available bandwidth. To ensure that the network can handle
the extra load, it may be necessary to do some or all of the following:
m Determine the capacity of the existing network and calculate the anticipated additional
traffic generated by live and on-demand streaming.
m Draw a map of bandwidth segments on your network, listing the capacity between all
points.
m Determine which applications are used in your network, their use patterns, where they
are hosted, and the bandwidth they normally use during peak and off-peak times.
m Based on the configuration and capacities of your network, select the appropriate place to
install your streaming server, avoiding potential bottlenecks.
m If necessary, add capacity to the network (additional T1 lines, routers, switches, and so
on) to handle the anticipated maximum number of concurrent viewers of live broadcasts
in addition to other peak network traffic.
Keep in mind that a typical local network provides bandwidth internally of 10–100 Mbps.
In contrast, a T1 line, frequently used to connect to the Internet, provides only about 1.5
Mbps of bandwidth.
T1 lines work fine for HTTP and FTP, where the requests are either short lived or are not
time sensitive, but streaming is much more demanding. With streaming you can’t slow
things down. The data has to be transferred at least as fast as the original content data rate
in order to deliver streams.
For this example, we will assume a maximum of 10 concurrent viewers, half on the local
network and half on the Internet and a bit rate for each unicast stream of approximately
256 kilobits per second (Kbps). The peak extra bandwidth needed is then about 3.2–3.3
megabits per second (Mbps). This estimate includes an extra margin of 25–30 percent for
unplanned network congestion and peaks in the transmitted streams that can occur for
various reasons.
LL0329.book Page 58 Wednesday, November 20, 2002 2:09 PM