rmation and the receiver processing the request and sending a response. Request with acknowledgment: Here the sender expects an acknowledgment from the receiver on the status of data delivery. Request with encrypted: Here an encryption methodology is agreed between sender and receiver and this is followed in the message exchange where the payload, and in some cases the header also, will be encrypted. Single and multiple intermediaries: Here an intermediary is present between the sender and ultimately the receiver. Asynchronous messaging: Here the sender does not expect an immediate response from the receiver. The sender will tag the request with an identifier to correlate with the response when it arrives. Fundamentals of EMS, NMS and OSS/BSS 18.3 XML Protocol Message Envelope The XMLP message envelope is the data encapsulation component of XMLP protocol. The message envelope is a key component of the XMLP protocol that allows it to be extremely versatile and adaptable for use in carrying management information. The envelope is a syntactical construct that contains: XMLP header block: There is only one header block for multiple body blocks. The header block consists of: Routing information for the message envelope. - Data describing the content of the body blocks. - Authentication and transaction information. Flow control and other information that will help in message management. - XMP namespace field for grouping. It can also be used for versioning to ensure a transparent conversion of the message for different versions sup- ported by the various XMLP processors. XMLP body blocks: This is the actual payload of the message and there will be multiple body blocks in a single message envelope. The body blocks do not have any information about message transfer and is only processed at the final destination. 18.4 XML Protocol Binding The binding defines the mapping of an XMLP message, also called an XML info- set into a specific "on-the-wire" representation. This on-the-wire representation is specific to the transpor