Apparatus and method for a buffer reservation system

• Main Authors: HAMMOND, JR.; WILLIAM A, JOHNSON; ROSS E, NATION; GEORGE W
• Format: Patent
• Language: English
• Published: 18.03.1997
• Edition: 6
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

An apparatus and method in a data processing system for sending a data packet from a source node to a destination node. The data processing system includes a multi-segment network having at least two segments, wherein the source node and the destination node are located within different segments. Communication of a data packet from one segment to another segment is provided by an agent node. When a receiving node, which may be either an agent or a destination node, cannot accept a packet, it places a reservation tag of "A" or "B" in an echo packet. The retried packet then uses this reservation tag to gain priority for any available buffers in the agent or destination node. The receiving node toggles between accepting all the outstanding "A" packets (when the receiving node is in the "receiving A" state) and accepting all the outstanding "B" packets (when the receiving node is in the "receiving B" state) assuming that the receiving node has a free, unoccupied buffer for accepting the packet. The receiving node counts the number of outstanding "A" reservations and the number of outstanding "B" reservations. Any time the number of available buffers is greater than the number of outstanding "A" packets (when the receiving node is in the receiving "A" state) any "new" packets or "B" packets will be accepted. Analogously, any time the number of available buffers is greater than the number of outstanding "B" packets (when the receiving node is in the receiving "B" state) any "new" packets or "A" packets will be accepted.