SAP Web Dispatcher
The SAP Web dispatcher lies between the Internet and your SAP system. It is the entry point for HTTP(s) requests into your system, which consists of one or more NetWeaver application servers. As a "software web switch", the SAP Web dispatcher can reject or accept connections. When it accepts a connection, it balances the load to ensure an even distribution across the servers. The SAP Web Dispatcher therefore contributes to security and also balances the load in your SAP system.
You can use the SAP Web Dispatcher in ABAP/Java systems and in pure Java systems, as well as in pure ABAP systems.
It is also useful to use the SAP Web Dispatcher if you only want to cover one aspect (security functions or load balancing). We also recommend that you use the SAP Web dispatcher if you do not need security functions (entry point in the DMZ, SSL, URL filtering), but you simply want to balance the load between several SAP NW AS instances.
The SAP Web dispatcher is recommended when you use an SAP system with several SAP NW AS instances for Web applications.
The SAP Web dispatcher is a program that you can run on the machine that is connected directly to the Internet. It requires minimal configuration - you just have to enter the following data in the profile file:
Port, on which the HTTP(s) requests are to be received (parameter icm/server_port_<xx>)
Host and HTTP port of the SAP Message Server (parameter rdisp/mshost and parameter ms/http_port)
If you should be able to call the Web application externally, for example using the URL www.shop.acme.com, this host name must be mapped internally to the SAP Web dispatcher. This then forwards the HTTP(S) request to a suitable application servers.End of the example.
The SAP Web Dispatcher can also be used with older releases of SAP systems.
Operating system prerequisites can vary between releases.
For more information, see the Product Availability Matrix on SAP Service Marketplace at http://service.sap.com/pam.
The SAP Web dispatcher performs the following tasks:
Selection of appropriate application server (persistence with stateful applications, load balancing, ABAP or Java server).
For more information, see: Server Selection and Load Balancing Using the SAP Web Dispatcher
URL filtering - You can define URLs that you want to be rejected, and by doing so restrict access to your system.
For more information, see: SAP Web Dispatcher as a URL Filter
Web caching – you can use the SAP Web Dispatcher as a Web Cache to improve the response times and to conserver the application server cache.
For more information, see: SAP Web Dispatcher as a Web Cache
Depending on the SSL configuration you can forward, terminate, and (re)encrypt requests.
For more information, see: SAP Web Dispatcher and SSL
The SAP Web dispatcher is only useful in the Web environment. In the classic SAP system, load is balanced by the message server.
The SAP Web dispatcher forwards incoming HTTP(S) requests to the application servers and returns the responses from the back end to the client.
Outgoing requests (such as requests to a different SAP Web Application Server) are not sent via the SAP Web dispatcher. They are sent via the proxy server for the appropriate intranet.
The documentation is split up into the following sections:
Architecture of the SAP Web Dispatcher describes the structure and how the dispatcher works.
Management of the SAP Web Dispatcher describes how to configure, manage, and monitor the SAP Web Dispatcher.
In the appendix you can find the specification for retrieving and interpreting the list of available application servers. This is available in English only: SAP Application Server List Retrieval Specification.
You can find details of the change history of the SAP Web Dispatcher in collective note SAP Web Dispatcher (SAP note 538405).