Fragmentation in store-and-forward message transfer

The advantages of store-and-forward (S/F) message transfer at the application layer and problems with existing systems are discussed. Current systems suffer from the limitation that if an intermediate message transfer agent (MTA), the entity responsible for storing and forwarding messages, cannot store a message in its entirety due to insufficient buffer space, then the transfer fails. A mechanism is introduced, called message fragmentation, to transfer messages too large to be completely stored on an intermediate MTA automatically and efficiently. In addition to letting a large message pass through the network, fragmentation improves performance in an S/F message-based system. Schemes developed for flow control, deadlock prevention, and buffer management in packet-switched networks are described, and their suitability for use in the message-handling environment is discussed. Several novel schemes for buffer management in the message-handling environment are presented. The EAN X.400-based S/F message-handling system developed at the University of British Columbia is briefly cited as an example.<>