Reference Section

The reference section provides the path(s) to an .asf file(s). NetShow Player reads the .asx file and attempts to find the first .asf file listed in the reference section. If it cannot find the .asf file, or some problem prevents the .asf file from playing correctly, NetShow Player looks for the next URL, called a rollover URL. NetShow continues looking for URLs in the .asx file to play until it succesfully starts one. Rollover URLs can be a path to the same .asf file hosted on a different server, or the URL can be the path to a different .asf file. The processing order of the URLs in the reference section is from the top downward. If the first URL fails, the next URL is tried until one that works is found.

When defining the URLs in the reference section, you can specify either the MMS or HTTP protocols. When listing multiple URLs, give each one a different reference number. The reference section of a sample .asx file would look like this:


[reference]
Ref1 = mms://NSserve/publpt/example.asf
Ref2 = mms://Nsserve2/publpt/example.asf
Ref3 = http://HTTPsrv/virtdir/file.asf
BaseURL = http://HTTPSRV2/dir

Each URL in an .asx file should specify:

A protocol (you can specify MMS, MMSU, MMST, or HTTP)
The name of the server
The publishing point or virtual directory (if necessary)
The .asf file

Optionally you can set the BaseURL property.

When specifying a protocol, you can use MMS, MMST (for TCP), MMSU (for UDP), or HTTP (for HTTP). The protocol you specify is what NetShow Player will request NetShow Server to use when streaming the file. Specify MMST to request TCP streaming, specify MMSU to request UDP streaming, or specify HTTP to request HTTP streaming. When you specify MMS, you will receive whatever protocol is enabled on the NetShow Player Advanced Properties page (which by default is TCP and HTTP). The protocol you specify affects how the server will stream the file. TCP is a reliable protocol which will ensure that you won't lose information when watching an .asf file. However, the drawback to ensuring reliability is that at times network traffic may force NetShow Player to wait for ASF information to be delivered. UDP provides connectionless service for unacknowledged delivery, that is, a server using UDP transmits information to the client and doesn't wait to hear if the client received the information. UDP doesn't make NetShow Player wait for information, but UDP streaming is susceptible to losing packets in high network traffic. HTTP streaming is reliable, but also forces NetShow Player to wait. You will need to use HTTP streaming to stream information through firewalls that don't allow other types of streaming.

NetShow Server, which is what you intend to use when you specify MMS, uses User Datagram Protocol (UDP). An HTTP server uses Transport Control Protocol (TCP) to stream information. TCP is reliable, but because of this, an HTTP server's streaming performance suffers when placed under heavy duress (especially on the Internet). UDP, although not reliable, does a better job of getting the streaming information to the client in a timely manner. The user experiences a better, smoother, and more likely uninterrupted playback.

After creating .asx files for the .asf files, place the .asx files in a directory on an HTTP server. It is a good idea to create a virtual directory for the .asx files so that it is easy to create, remember, and possibly edit the path to these files. If you want to use Web pages to play .asf files, use the .asx files as HREF links for buttons, icons, or jumps. You can also send the .asx files in e-mail. Provided that the server that the .asx file points to is on the network, when the viewer executes the .asx file, NetShow Player will start and begin playing the .asf file.