Abstract: The Spanning Tree Protocol converges to a new configuration after the loss of a link. A new frame, known as a root link query request BPDU is transmitted to the root bridge in the spanning tree when a bridge detects an indirect link failure through the reception of an inferior BPDU on a blocked port. Each bridge forwards this root link query until the root link query reaches the last reachable upstream bridge or a bridge which has a different Tx_Root_Id than the one identified in the RLQ-REQ-BPDU. If the last reachable bridge is the root bridge identified in the RLQ-REQ-BPDU, then a second new frame known as an RLQ-ACK-BPDU is sent, and the bridge port receiving this acknowledgment BPDU is changed from a blocked port to a designated port. If the RLQ-REQ-BPDU reaches a bridge with a different Tx_Root_Id than the one in RLQ-REQ-BPDU, a third new frame known as RLQ-NAK-BPDU is sent.

Abstract: A shared spanning tree protocol (SSTP) creates a plurality of spanning trees (i.e., loop-free paths) which are shared among one or more virtual local area network (VLAN) designations for data transmission within a computer network. Each shared spanning tree includes and is defined by a primary VLAN and may be associated with one or more secondary VLANs. In order to associate VLAN designation(s) with a single shared spanning tree, network devices exchange novel shared spanning tree protocol data units (SST-PDUs). Each SST-PDU corresponds to a given primary VLAN and preferably includes one or more fields which list the secondary VLAN designations associated with the given primary VLAN. The association of VLAN designations to shared spanning trees, moreover, preferably depends on which path traffic is to follow as well as the anticipated load characteristics of the various VLANs. The association of VLAN designations to shared spanning trees thus provides a degree of load balancing within the network.

Abstract: A computer network having multiple, dissimilar network devices includes a system for implementing high-level, network policies. The high-level policies, which are generally device-independent, are translated by one or more policy servers into a set of rules that can be put into effect by specific network devices. Preferably, a network administrator selects an overall traffic template for a given domain and may assign various applications and/or users to the corresponding traffic types of the template. Location-specific policies may also be established by the network administrator. The policy server translates the high-level policies inherent in the selected traffic template and location-specific policies into a set of rules, which may include one or more access control lists, and may combine several related rules into a single transaction.

Abstract: A system in which a single VLAN architecture spans multiple VLAN transport protocols and technologies, including a method and system in which multiple different VLANs may be combined in a single enterprise network. Each LAN-switch in the sytem identifies each frame with an identifier, and associates that identifier with particular VLAN identifiers for each type of VLAN technology. When a frame is bridged or routed from a first type of VLAN to a second type of VLAN, the first VLAN encapsulation is removed and the second VLAN encapsulation is added, with appropriate change in the VLAN identifier for the frame or packet. The identifier may also be implicit for the frame, such as when a particular set of sender's MAC addresses are identified with a particular VLAN. Individual VLANs, of whatever architecture, may be added, configured or reconfigured, modified, or deleted, using control tools associated with the multiple VLAN architecture system.

Abstract: A method that rapidly reconfigures a computer network having a plurality of devices executing the spanning tree algorithm. First, one or more devices are configured and arranged so that one port, providing connectivity to the root, is in the forwarding state and the remaining ports, providing connectivity to the root, are in the blocked state. Next, one or more of the blocked ports are designated as back-up ports. Upon detection of a failure at the active forwarding port, one of the back-up ports immediately transitions from blocked to forwarding, thereby becoming the new active port for the device. Following the transition to a new active port, dummy multicast messages are transmitted, each containing the source address of an entity directly coupled to the affected device or downstream thereof. By examining the dummy multicast messages, other devices in the network learn to use to the new forwarding port of the affected device.