Patent ID: 7142507

Claim:
A datagram transfer system, for receiving datagrams sent from individual users' terminals in a datagram transmission node and forwarding said datagrams to a destination address specified on a header of said datagrams, wherein an impact of said datagrams on network operation is evaluated by a traffic monitoring equipment according to traffic information on said datagrams, evaluation results are quantified, and quantified results are converted and are inserted in said header as a preference value, and wherein said datagram transmission node includes a back plane switch section for transferring a datagram from an incoming interface section to an outgoing interface section without causing internal blocking, and a buffer enqueue control section for obtaining the preference value from the datagram received in said outgoing interface section, selecting priority datagrams to be transmitted successively in an ascending order of preference values from a low preference value to a high preference value so as to avoid traffic congestion and entering said priority datagrams in a buffer memory; wherein said traffic monitoring equipment uses a length field of said datagrams provided in the header of a datagram for inserting the preference value.