Streaming media connection statistics can be more difficult to decipher than HTTP statistics. Unlike HTTP connections, streaming media connections often require more than one connection to the streaming server. For the most part, these multiple connections consist of data, control, and feedback connections. However, other connections can be initiated for a variety of reasons during streaming. This section describes the types of connections you might see and explains when these connections are initiated during streaming.
You can get streaming media statistics by accessing the following areas of the Appliance Manager.
The following pages enable you to view streaming logging information:
To access these pages in the Appliance Manager, select Data tab > Log Files.
The following pages enable you to view streaming-related statistics:
To access these pages in the Appliance Manager, select Data tab > Streaming.
NetCache supports UDP transmission of streaming data from the streaming media cache to the client. Many streaming media administrators prefer to use UDP transport because it is more efficient. Whether UDP is used, however, depends on whether the client media player is configured to use UDP and whether the firewall is configured to allow UDP ports.
Clients can request TCP, UDP, or HTTP data transport from NetCache. Whenever possible, NetCache uses TCP to connect to streaming servers. Using TCP to connect to streaming servers guarantees that packet loss will not interfere with the quality of streaming content.
Media players attempt to connect to streaming servers using the following transports and ports, in order of precedence.
Even when NetCache serves content by splitting a stream or serving it from the cache, NetCache might open new connections to the streaming server to
When a user requests a stream that is in the cache but has expired, that is, it has exceeded its Time-To-Live (TTL), NetCache verifies the freshness of the stream with the originating streaming server. See How NetCache handles streaming objects for more information.
When NetCache is configured to send client logging information to the streaming server, NetCache opens a connection to the streaming server to provide information to the streaming server, for example, how many clients viewed the content, how many bytes were sent to the client on behalf of the streaming server, and the amount of the time that the client played the content.
NetCache must initiate a connection to the streaming server if such a connection is required to honor a vendor's licensing requirements. These connections are persistent throughout client playtime.
If the streaming server requires end-user authentication, NetCache opens a connection to the streaming server to provide client authentication credentials.
These server connections are very low bandwidth and are usually initiated only during connection initiation and termination.
When the appliance is under high memory load, it terminates the following types of connections to conserve memory:
The appliance tries to avoid terminating connections that are serving data directly from the cache and connections that are just being proxied (these connections use less memory).
If you continually see the following entry in the Streaming details log, you might need to upgrade to an appliance with more capacity:
SERVER_DATA_PRIVATE_LOW_MEMORY
In scalable multicast streaming, NetCache cannot rely on client close-connection requests to terminate a unicast connection to the origin server. Instead, NetCache monitors traffic on each multicast channel. If, after a fixed amount of time, NetCache does not detect any Internet Group Management Protocol (IGMP) traffic for a particular multicast channel, NetCache tears down its connection to the origin server and terminates the current streaming session.
How NetCache forwards client logging information depends on whether the stream has been proxied, cached, or split.
When NetCache proxies streams, it simply forwards any logging information sent by the client.
When NetCache streams data from the cache, NetCache opens a control connection to the streaming server and forwards any logging information sent by the client.
When NetCache delivers a split stream to a client, NetCache forwards the client logging information over the shared origin server connection. The association between individual client and server connections is not maintained.
Note
Some logging information might be blocked by going through the appliance, for example, the client IP address. To support client IP logging and access control at the server, you must implement IP spoofing. For more information, see the transparency information in the Administration Guide.
Because of the highly variable nature of available network bandwidth, the media player might need to increase or decrease the bit rate of the stream to achieve optimum playback. Because streams are differentiated by bit rate, NetCache must provide the client with a new stream every time the client requests a different bit rate. This stream switching can occur several times as the user plays streaming content.
Each time the media player requests a new bit rate during playback, NetCache delivers the new stream using one of the following methods:
NetCache can dynamically switch streams and not affect client playback.
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Part No. 210-00369
File: stream24.htm
Last updated: 11/12/02 12:13:46