ATM partial cut-through

DETAILED DESCRIPTION In accordance with one aspect of the present invention there is provided a method of transmitting across a network a connectionless datagram in a packet structure having the form of a series of packets, the header including the routing information of the connectionless datagram being mapped into the payload of the first packet structure, and wherein at an intermediate node of the network a connectionless routing function is carried out on said first packet.
In accordance with a second aspect there is provided a switching node for a data network, the switching node comprising: an ATM switch; means for accepting a connectionless datagram and converting the datagram into a plurality of ATM cells in which header information in the connectionless datagram is inserted into the payload of the first cell of the ATM cell structure; and means for detecting the length of the header fields of the connectionless datagram and if the length of these fields is too great to be contained in the payload of the first cell of the ATM cell structure generating a partial header checksum and inserting this checksum into the payload of the first ATM cell together with only the header fields of the connectionless datagram up to and including the destination address.
In accordance with a third aspect there is provided a switching node for a data network, the switching node comprising: an ATM switch; means for accepting a connectionless datagram and converting the datagram into a plurality of ATM cells in which header information in the connectionless datagram is inserted into the payload of the first cell of the ATM cell structure; and means for detecting the length of the header fields of the connectionless datagram and if the length of these fields is too great to be contained in the payload of the first cell of the ATM cell structure generating a partial header checksum and inserting this checksum into the payload of the first ATM cell together with only the header fields of the connectionless datagram up to and including the destination address