Abstract: An early return indication is used to notify a first communications interface, prior to a response being received from any of a plurality of sources coupled to a second communications interface, that the return data can be used by the first communications interface when it is received thereby from a source of the return data if the source has an exclusive copy of the return data. By doing so, the first communications interface can often prepare for forwarding the return data over its associated communication link such that the data can be forwarded with little or no latency once the data is retrieved from its source, and may be able to initiate the return of data over the communication link prior to all responses being received from the other sources.

Abstract: In a shared memory architecture, early coherency indication is used to notify a communications interface, prior to the data for a memory request is returned, and prior to updating a coherency directory in response to the memory request, that the return data can be used by the communications interface when it is received thereby from a source of the return data. By doing so, the communications interface can often begin forwarding the return data over its associated communication link with little or no latency once the data is retrieved from its source. In addition, the communications interface is often no longer required to wait for updating of the coherency directory to complete prior to forwarding the return data over the communication link. As such, the overall latency for handling the memory request is typically reduced.

Abstract: A method and apparatus are provided for switching among different network paths while suppressing ghost packets. A single path through the network for a destination endpoint is established for accepting packets from each source endpoint. Control packets are provided for changing to an alternate path through the network. Before using an alternate path, all buffered packets with a matching source and destination pair in the alternate path are deleted.

Abstract: A method and system for communication in a system area network (SAN) data processing system are described. The SAN includes a plurality of interconnected nodes that each have at least one port for communication. To avoid communication-induced errors that may arise, for example, if multiple nodes share the same node ID, the port of a node in the SAN is marked as “fenced” to prevent transmission of packets of a first traffic type while permitting transmission of packets of a second traffic type. The marking of the port may be recorded, for example, in a configuration register of the port. While the port is fenced, only packets of other than the first traffic type are routed via the port. In one preferred embodiment, the second traffic type represents SAN configuration traffic, and the first traffic type represents non-configuration traffic.

Abstract: A method and system for communication in a system area network (SAN) data processing system are described. The SAN includes a plurality of interconnected nodes that each have at least one port for communication. To avoid communication-induced errors that may arise, for example, if multiple nodes share the same node ID, the port of a node in the SAN is marked as “fenced” to prevent transmission of packets of a first traffic type while permitting transmission of packets of a second traffic type. The marking of the port may be recorded, for example, in a configuration register of the port. While the port is fenced, only packets of other than the first traffic type are routed via the port. In one preferred embodiment, the second traffic type represents SAN configuration traffic, and the first traffic type represents non-configuration traffic.