ITS Architecture 

The Internet Transaction Server (ITS) extends the client/server architecture of the SAP system to the Internet.

The ITS is a gateway between one or more Web servers and one or more SAP application servers. Typically, the Web server is an HTTP server, but other protocols such as FTP or Gopher may also be supported.

All requests and responses that pass between a Web browser client and an SAP server are managed by the ITS, which consists of 2 main gateway components:

·        Web server gateway (WGate)

·        Application server gateway (AGate)

WGate

WGate links the ITS to the Web server.

WGate receives requests from the Web browser via the Web server and forwards them to AGate via a TCP/IP connection.

WGate always resides on the same machine as the Web server.

WGate is a Web server extension that shields AGate from differences in the various Web server APIs used. WGate supports the following Web servers:

·        Microsoft Internet Information Server (IIS) through the Information Server API (ISAPI)

·        Netscape Enterprise Server (NES) through the Network Server API (NSAPI)

·        Apache Web Server through the Apache Web Server API

WGate connects a ‘stateless’ Web server, which communicates with Web browsers via single request/response cycles, to a ‘stateful’ SAP system where business transactions depend on internal status.

When an Internet or intranet user starts an application from a Web browser and triggers an SAP transaction, function module or report via the ITS, a server process must be running throughout the user session (possibly longer) in order to maintain the user’s context in SAP system. Although communication between the Web browser and the Web server is based on single request/response cycles, WGate must be able to transfer the browser request to a permanently running server process. This is the role of the AGate component.

AGate

AGate links the ITS to the SAP application server.

AGate is the core processing component of the ITS.

AGate receives Web browser requests from WGate and communicates with the SAP application server via the DIAG protocol or the RFC protocol.

AGate is effectively responsible for managing all sessions, services and users, as well as for generating the HTML documents that are sent back to the Web browser client.

When a connection has been established, AGate processes the requests and sends all relevant details (including logon information) to the SAP system, which either starts the first dialog step of a new transaction or submits further data for the next dialog step of a transaction already started. When a dialog step has finished, AGate retrieves the results from SAP system, processes them and sends the response back to WGate.