Methods on a proxy are overloaded with a trailing parameter representing a request context. The Slice definition of this parameter is as follows:
module Ice {
dictionary<string, string> Context;
};
As you can see, a context is a dictionary that maps strings to strings or, conceptually, a context is a collection of name-value pairs. The contents of this dictionary (if any) are implicitly marshaled with every request to the server, that is, if the client populates a context with a number of name-value pairs and uses that context for an invocation, the name-value pairs that are sent by the client are available to the server.
On the server side, the operation implementation can access the received Context via the ctx member of the Ice::Current parameter and extract the name-value pairs that were sent by the client.
Context names beginning with an underscore are reserved for use by Ice.