Abstract: Method and apparatus for making limited internal-node communication facilities externally visible in a packet switching network. Internal-node communication facilities are called intranode links, can include any cable, channel, bus, etc. over which data passes, and are used to connect the multiple subnodes within a given node. Each subnode contains a switching mechanism and routes packets to other nodes, subnodes, or user applications. Each node provides network control functions such as topology, directory, path selection, and bandwidth management which can manage intranode links in the same manner that internode links are currently managed.

Abstract: A method is disclosed for determining whether to use a preempt/resume protocol or an alternate protocol in transmitting data packets from a local system to a remote system. Each system informs the other whether it supports preempt/resume and provides the sizes of the largest low priority data packets it can send and receive. The local system always elects the alternate protocol unless both support preempt/resume. The local system then selects the lesser of (a) the largest low-priority data packet it can send and (b) the largest low-priority data packet the remote system can receive. Use of prompt/resume is initiated by the local system only where a packet of the selected size would be delayed in reaching the remote system by more than a predetermined interval.

Abstract: A packet communications system provides for point-to-point packet routing and multicast packet routing to limited subsets of nodes in the network, using a routing field in the packet header which is processed according to two different protocols. A third protocol is provided in which a packet can be multicast to the limited subset even when launched from a node which is not a member of the subset. The routing field includes a first portion which contains the route labels necessary to deliver the packet to the multicast subset. A second portion of the routing field contains the multicast subset identifier which can then be used to deliver the packet to all of the members of the multicast subset. Provision is made to backtrack deliver the packet to the last node identified before the multicast subset if that last node is itself a member of the subset.