External Session Identifier 

The External Session Identifier is not generated by the backend server where the Web Dispatcher requests are dispatched to. Instead, it is generated externally, by the SAP portal. The External Session Identifier does not contain a server name.

External Session ID in URL

The external Session Identifier is included as a standard semicolon-separated URI parameter (see RFC 2396: Section 3.3 “Path Component”). The name of the URI-parameter is “sap-ext-sid”.

<uri-path-segment> ;sap-ext-sid=<external session identifier> 

/sap/;sap-ext-sid=<external session identifier> /foo/bar