Abstract: A technique efficiently transports token ring (TR) frames over trunks interconnecting switches of a distributed TR bridge. The TR bridge is characterized by a logical switch fabric that is distributed among the interconnected switches by the trunks, which are preferably interswitch link (ISL) trunks. Each switch includes a Bridge Relay Function (BRF) coupled to a plurality of Concentrator Relay Functions (CRFs) having a plurality of ports for receiving TR frames over TR segments. The BRF and CRF of the distributed TR bridge operate according to a 2-tier switching model wherein each CRF and BRF is assigned an individual virtual local area network identifier. The technique encapsulates the TR frames in a TR-ISL protocol format that accomodates differences in formats of various TR frames and that comports with the 2-tier switching model of the distributed TR bridge.

Abstract: A Distributed Ring Protocol (DRiP) arrangement includes a database and protocol for maintaining and distributing information within a distributed token ring (TR) bridge having a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links, such as Inters witch Link (ISL) trunks. The DRiP information is used by switches within the ISL switched fabric to determine the status (configured and/or activated) and association (within a switch) of ports of the distributed bridge.

Abstract: A backup CRF VLAN arrangement provides an alternate, redundant path for traffic between undistributed Concentrator Relay Functions (CRFs) located on separate switches interconnected by trunk links of a distributed token ring bridge. The backup CRF virtual local area network (VLAN) arrangement defines a backup network path which may be utilized if a primary active path is not a valid path to a backup network. Notably, the backup network comprises a special type of CRF that is distributed among the switches, but that has only one port active at any given time.

Abstract: A distributed token ring (TR) bridge has a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links. The distributed TR bridge includes a plurality of TR switches, each having a Bridge Relay Function (BRF) logically coupled to at least one Concentrator Relay Function (CRF). Distribution of the switch fabric essentially comprises logically distributing the BRF function among the network of switches.

Abstract: An improved spanning tree protocol for use by token ring intermediate devices having one or more Concentrator Relay Function (CRF) entities and associated Bridge Relay Function (BRF) entities. Each CRF and BRF entity preferably includes a spanning tree engine and corresponding database for individually executing an instance of the spanning tree algorithm and is configured to select a different Bridge Protocol Data Unit (BPDU) message type for use in executing its respective spanning tree algorithm. The selection of BPDU message type by the CRF and BRF spanning tree engines preferably depends on the routing configuration of the associated CRF. The selection of BPDU message type by the CRF entities assures that they are dropped by legacy intermediate devices and only acted upon by the originating CRF or another CRF coupled thereto.