Datagrams transferred as message trains in local area networks

A method is proposed of reliably transferring datagrams consisting of sets of data structures, which are of arbitrary sizes and non-contiguously resident in memory, over local area networks without concern for the restrictions on packet format imposed by the characteristics of the actual network interface.

The transfer is performed as one atomic operation with minimal overhead; on the basis of a set of premises respected by many local area networks, it is possible to send a datagram as a sequence of packets without specific headers. The integrity of the transmission is verified by counting the received packets. Both the sender and the receiver must know the structure of the datagram. One acknowledgment packet is sent for the entire datagram.

Similar techniques of packet counting for local area networks have previously been used in specialized protocols for remote operations at Stanford and for file transfer at Cambridge. In the present paper, the techniques are used to provide a flexible and reliable datagram transfer mechanism while reducing copying and processing overhead in the communicating hosts.

With the proposed protocol, data items of any size are copied directly between the various different memory areas belonging to the user and protocol layers and the network driver.