An .asf file is designed to be streamed from NetShow Server to NetShow Player. NetShow Server and NetShow Player can be on the Internet or an intranet, and they can be separated by a firewall. As a content creator, once you know what the .asf file will be, network bandwidth is your first concern.
Bandwidth and bit rate are the essentially the same thing in terms of streaming .asf files. Bandwidth is often used to describe the size of a network, and bit rate describes the rate at which an .asf file is delivered. An .asf file created to stream over a 28.8 bandwidth network will not stream at more than 28.8 kilobits per second (kbps). This means that no more than 28,800 bits of information are traveling across the network each second. The 28.8 bandwidth (just like the 14.4, 56, and 112 kbps bandwidths) is used as a standard because it is the most information that a particular user can accept per second.
When creating .asf files, you should always keep the target network bit rate in mind. Some tools, such as the ASF Editor, will allow you to enter the target network bit rate so that you don't have to worry about it; the tool will then limit the amount of information you use to create an .asf file. However, most tools do not monitor the target network bit rate. In these cases, it is up to you to make sure that the .asf file you are creating can stream to the target audience. If the .asf file bit rate is larger than the maximum bit rate of the viewer's modem, then that viewer won't be able to see the .asf file.
Because .asf files can travel from the Internet to an intranet or vice versa, you should create .asf files for the clients that have the smallest bandwidth. An .asf file intended for Internet clients will probably need to be smaller in bandwidth than one delivered over an intranet because most Internet users have 28.8 kbps modems. Another important thing to know about network bandwidths is that the entire bandwidth cannot be used to send your information. You must share the network bandwidth with other types of communications. The bandwidth or bit rate that your .asf file can have is considered its actual bandwidth or bit rate. If you are creating an .asf file with a NetShow tool that monitors the amount of bandwidth that you are using, when you set the target bandwidth to 28.8 kbps, the actual bandwidth that the tool allows you to use is around 22 kbps. The rest of the bandwidth is left for other types of network traffic. If you are using a tool that forces you to keep track of the bit rate of the .asf file, you will need to monitor the amount of information you are putting into the .asf file based on the actual bit rate. We'll discuss how to figure the actual bit rate in a later section.
Intranets can handle .asf files that stream at a much higher bit rate than on the Internet. In the intranet environment, your network administrator or the network bandwidth will enforce restrictions on an .asf file's bit rate. The network administrator can set NetShow Server to restrict the amount of information that it will stream. This restriction keeps the server, during high use, from streaming so much information that it bogs down the overall flow of information on the network. If the network administrator doesn't set a limit on the amount of information that NetShow Server can stream, then the network bandwidth will be the limiting factor for .asf files.
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