request (OSI) (REQ)
- Request (REQ) is one of four service primitives defined by the Open Systems Interconnection ( OSI) in the service model between the service user and the service provider. With the service primitive Request, the service user, for example a client, asks the service provider, a provider, for a specific service. The requested service provider responds with a response, which the requesting subscriber receives as an acknowledgement from the service provider. Such a query scenario is called a polling service.
- The HTTP protocol illustrates the implementation of the service model. In the request-response method used, after the connection is established, the Web browser directs an HTTP request to the Web server, i.e., a request for an HTML document. The server transmits the requested document to the web client in its HTTPresponse. The connection is then terminated again.
- In theSNA architecture, a request is a message unit that signals the completion of a particular action or protocol. For example, "Initiate Self" is a request for the activation of an LU-LU session, a session between two Logical Units (LU).
