This section provides a number of tips and techniques you can use to improve RealServer's performance with other system components.
Layer-4 switches currently do not recognize the UDP conversation sent from the client, if there is a re-send request due to lost packets. This happens because UDP data coming from the server to the client is sent to the client's IP address, bypassing the Virtual IP (VIP). The client still believes the server's IP address is the VIP, so it returns its UDP traffic to the VIP. The Layer-4 switch (acting on the VIP port) does not recognize the UDP data, and drops the packet. Therefore, UDP data from the server to client works, but UDP traffic from the client to the server does not. This affects the quality-of-service for all clients accessing content through a switch.
RealServer now supports the RTSP transport parameter of the "source address" (as discussed in RFC 2326) . This feature enables the source RealServer to specify to the client what IP address it should use in sending back its UDP data. To enable this workaround, the RTSPSourceAddress configuration variable must be added to the server's configuration file:
<Var RTSPSourceAddress="*"/>
If "*" is specified, then the server will insert the IP Address of the network interface that the client address came in on.
Equally acceptable is designating a specific IP address:
<Var RTSPSourceAddress="170.137.192.0"/>
Note that this edit will require that you restart your server.
The Network File System (NFS) is a distributed file system that enables UNIX- or Solaris-based computers to access files and directories located on remote computers and to treat those files as if they were local. Often, deployments will include computers that are specifically designated to serve only streaming media.
If possible, avoid using NFS as either a client or a server. It adds overhead and latency to the network, resulting in poorer performance. If you choose to use NFS and its caching functionality to manage your files—especially with content that needs to be updated frequently—be careful not to hard mount your paths, as this will result in the files being overwritten, with no mechanism available for controlling which file versions are the ones intended for distribution.
Be sure to set parameters for access and error log files; otherwise, they will accumulate data indefinitely and consume system resources needlessly. Limit the log files either by time period or by size. You can set these restrictions in the Logging section in System Administrator, at http://yourserver:youradminport#/admin/config_logging.html.
You can set restrictions on streaming media bandwidth consumption in the Connection Control section of RealSystem Administrator (at http://yourserver:youradminport#/admin/config_allow.nc.html), where you can:
You can also distribute the stream capacity established in a valid license file to other RealServers (subscriber RealServers) that you operate. To do this, see the License Group section in RealSystem Administrator, at http://yourserver:youradminport#/admin/config_license.html.
Round-robin is a clustering technique that makes load sharing possible among multiple RealServers. All of the main RealServer platforms—Linux, Windows NT, and Solaris—support DNS and BIND. (DNS stands for Domain Name System, a hierarchical system that translates host names, or domain names, into Internet addresses.)
This technique enables you to duplicate address records for a specific RealServer host, with different IP addresses. The domain name server then rotates addresses for any name that has multiple address records, thus handing off the load to an available RealServer as client requests are received.
When installing RealPlayer® on a local area network (LAN) that has an ISDN router to the outside world, always be sure to disable RealPlayer's Auto-Update functionality within the StartCenter feature. Otherwise, this feature may trigger the dial-on-demand feature in the router, resulting in continual, unnecessary dial-ups that could cost money and consume precious bandwidth.
There are two methods for finding out which version of RealServer you are running. The following procedures explain these methods.
At the command prompt, navigate to the Bin directory, and then type the following:
rmserver -v
The version number appears, using the following syntax: 8.x.x.xxx.
In RealSystem Administrator, click About under Help in the table of contents area on the left.
A new browser window appears, with information about your RealServer. The version number can vary, depending on the operating system you are using.
Use RealServer's error messages to pinpoint problem areas.
The "High Capacity mode" error message is a definite flag for performance problems, as it means that your computer is currently using more than 75 percent of your system's capacity.
The RealServer error log is the first place you should go to review sluggish RealServer performance, especially if you are testing file performance. The error log's default location in Windows NT is as follows:
C:\Program Files\Real\RealServer\Logs\rmerror.log
For UNIX-based systems, there is no automatic default path, and the log file name is ...../rmerror.log.
The following is a sample error message:
***20-Oct-00 18:21:30.539 logplin(1571): The server has entered High Capacity mode, this may result in lowered quality of service for some players. The current load is xxx Mbps total output to xxx players (0% PNA, 100% RTSP, 0% HTTP, 0% TCP/Cloaked, 100% UDP, 0% MCast).
For a comprehensive list of all of the error messages you might encounter when using RealServer, plus instructions for resolving them, see the following publication:
http://service.real.com/help/library/guides/g270/srvrmsgs/srvrmsgs.htm
The RealServer Administration Guide offers a wide range of troubleshooting tips in Chapter 21. You will find this guide at http://service.real.com/help/library/guides/server8/realsrvr.htm.
Whenever RealServer-specific security concerns arise, RealNetworks moves quickly to address them. The most recent security alerts are posted at http://service.real.com/help/faq/security/index.html.