Abstract: A method and apparatus for managing a loop network, the loop network (200) including at least one loop (206, 208), a plurality of devices (210) connected to the at least one loop (206, 208) via ports (211, 212), wherein at least two of the devices are initiators (207, 209). The method includes each initiator (207, 209) sending a frame to all other initiators (207, 209) in the loop network (200) identifying any ports (211, 212) which should not be used. Each initiator (207, 209) merges the information from all other initiators (207, 209) with its own information identifying any ports (211, 212) which should not be used resulting in all the initiators (207, 209) generating a single list of ports (211, 212) to be used which is consistent across all the initiators (207, 209). Each initiator (207, 209) applies an algorithm (300) to determine a common set of ports (211, 212) to be used by all the initiators (207, 209) and to balance port accesses across the loop network (200).

Abstract: An inserting and copying processing method for implementing an L2/L3 compatible RPR network is provided. The inserting processing method includes: encapsulating an Ethernet data frame with local mode or remote mode according to whether the source and destination MAC addresses of the Ethernet data frame may be found in the ring station MAC address table or in the correspondence table of host MAC address and RPR station, and whether the destination address of the Ethernet data frame is a unicast address or a non-unicast address. The copying processing method includes: recombining the RPR data frame into an Ethernet data frame according to the forwarding mode of the RPR data frame, and learning the correspondence relationship between source host address and RPR station address according to the Flooding flag and the forwarding mode of the RPR data frame. This invention also provides a data forwarding method and a network apparatus.

Abstract: In a communications network, a node receives a transit packet. The priority assigned to the transit packet is determined and when it has a low priority then the transit packet is removed and a higher priority packet is inserted in the resulting vacancy.

Abstract: In a transmission network including multiplex transmission units A, F, G, D and E, when the line breakage has occurred on the OC-12 transmission path of the direction from unit A to unit F, the unit F detects the signal coming in from the OC-12 path indicative of the line breakage. The unit F inserts the APS bytes which comes in from the unit A into the undefined area of the OC-192 transport overhead which is reserved for the through-transport of APS bytes, and transports it to the unit G. On receiving the through-transport APS bytes, the unit G inserts it intact into the defined area for the APS bytes in the OC-12 transport overhead, and sends it to the unit D. In this manner, protection switching between the units A and D is carried out.

Abstract: In a communications network where first and second nodes are interconnected by communication links, a source node transmits a path setup message for requesting a traffic path to a destination node. Each of the first and second nodes includes routing control means for establishing first and second transport paths on a first fault recovery layer between the first and second nodes. The first node further includes a database for storing identities of the first and second paths as a single virtual link as viewed from the source node. The first node responds to the path setup message from the source node for establishing the traffic path on a second fault recovery layer through the first transport path. The first and second nodes accommodate the traffic path through the second transport path when the first transport path is not working properly.

Abstract: An Ethernet passive optical network (EPON) ring for providing protection against fiber failures. The optical network unit (ONU) is coupled to the ring fiber by a three-port passive optical splitting module that has three two-way optical passages. By the three two-way optical passages, the OUN receives/transmits data from/to the two ends of the optical line termination (OLT) to provide protection while the fiber failure. Moreover, it provides better authorization of users and simpler collision detection by the two-way transmission of the three-port passive optical splitting module to prevent hackers from invading and to reduce collisions.

Abstract: A node in a first ring stores therein connection information about connecting nodes between a second ring and a third ring. Upon receiving a route of a working path by a signaling, the node determines any one of nodes composing the second ring as a branch node. If the working path is not terminated on an end node that the working path ends in the second ring thereon, and also if no node composing the second ring stores therein connection information between the end node and any one of the connecting nodes in the third ring that is connected to the second ring, the node compares each condition of selectable routes of a backup path between the end node and the branch node, and selects any one of the selectable routes as the backup path based on a result of comparison.

Abstract: A destination station in a wireless communication system for a multi-hop connection selects a transmission path having a minimum total of required transmission power values of respective stations on the transmission path among candidates of the transmission path from a source station to the destination station and transmits a pilot signal to the source station and a relay station, the pilot signal including identification information about the respective stations on the selected transmission path and required transmission power values thereof. Thus, the source station and the relay station, which have received this pilot signal, can determine the transmission path having the minimum total of the required transmission power values by use of the identification information included in the received pilot signal.

Abstract: The present invention relates in general to a method, apparatus, and article of manufacture for providing high-speed digital communications through a communications channel. In one aspect, the present invention employs a variable rate back channel, incorporated within an existing communication that does not increase or adversely impact the transmission rate of data on the communication channel.

Abstract: A plurality of bridges are interconnected between respective ports thereof in a ring shape to configure a network containing a redundant route. When a bridge has a blocking port, the bridge transmits to the network a blocking advertisement containing information indicating that it has a blocking port and its address. When a bridge does not have a blocking port, the bridge transmits a line failure notification to other bridges having a blocking port when a line failure is sensed. When a bridge has a blocking port and the line failure notification has been received from other bridges, the bridge transmits to the network a blocking release advertisement indicating that the blocking port has been transited to a forwarding state and the blocking state has been released. When a bridge receives a blocking release advertisement packet, the bridge erases a forwarding database thereof.

Abstract: Multiple memory channels of a multi-channel memory architecture are effectively bridged together to enable data traffic associated with various nodes in daisy chain arrangement to be communicated over both memory channels. For example, a daisy chain arrangement of nodes, such as FB-DIMM memory modules disposed in a first memory channel may be coupled to a second memory channel, with support for communicating data associated with one of the nodes over either or both of the first and second memory channels.

Abstract: A method for controlling switching in a bidirectional line-switched ring network configured by a plurality of optical fibers and a plurality of nodes, (i) having a first node receive as input an LP-S (or having the first node detect an SF-P) and having a second node adjacent to the first node across a span receive the LP-S (or receive the SF-P), and (ii) having the second node send an SF-R switch request to another node when the second node further detects an SF-R on said span under the above state (i), whereby a method for controlling switching in a bidirectional line-switched ring under conditions where ring switch and LP-S cannot co-exist, but ring switch and SF-P can, is realized, as a whole, in the ring network.

Abstract: A novel and useful mechanism for optical ring networks providing concentrator redundancy in the event of a failure of a concentrator. The nodes in a network are connected to dual concentrators to form bi-directional dual counter-rotating optical rings. The failure of one of the concentrators is detected and the internal connections of the surviving concentrator are reconfigured to form a single ring that provides an alternate communication path thus preventing the collapse of the ring. Reliability of optical rings is improved by enabling the ring to continue to function in the event of a concentrator failure.

Abstract: A ring network having a plurality of nodes connected by a working channel and a protection channel. When no failure exists, the working channel and the protection channel are link-aggregated into one virtual channel, and the transmission of the working traffic is carried out using both channels. When failure occurred to a line of the network, the link aggregation is suspended and a protection function in conjunction with the link aggregation is activated, in which a path avoiding the failure point is established by means of layer 1 protection process and thereafter data transmission is carried out by use of the path established by the layer 1 protection function. Therefore, data transmission in the no failure stated can be conduced using a bandwidth of twice as large as that of convention ring networks.

Abstract: A disk array apparatus is provided, which has dual FC-Als to each of which an enclosure service unit connects, and is capable of performing loop diagnoses including detachment and reconnection of devices even when abnormalities occur in all loops. The enclosure service units can communicate each other through an interface. Heartbeat monitors, when detecting that heartbeat commands transmitted through the FC-Als have ceased in both loops, detach all disks connecting to the FC-Als to thereby resolve the loop abnormalities. Then, loop diagnostic units cooperatively perform loop diagnoses including reconnection of disks to the FC-Als, identify faulty disks, detach the faulty disks, so as to continue the operation of the system.

Abstract: A method for communication includes representing a layer 2 ring network, which includes two or more ring nodes interconnected by two unidirectional ringlets, as a plurality of unidirectional point-to-point links connecting respective pairs of the ring nodes and having respective traffic engineering (TE) related attributes. The TE-related attributes of the point-to-point links are distributed to routers of a communication network that includes the ring network. The distributed TE-related attributes are processed to determine an optimal routing path traversing the ring network from a source node to a destination node in the communication network.

Abstract: The invention realizes defect indication on a multipoint logical path and switching of the logical path when the multipoint logical path is configured using a transfer protocol of configuring a logical path, typified by MPLS etc., in a ring network. Two routes of the multipoint logical paths, a working path and a backup path, are set up. Each of them not only transmits a frame transmitted from a transmitting end node to multicast receiving end nodes but also forwards the frame to the transmitting end node and terminates it also at the transmitting end node after making it go around the ring. Any node that detects a defect transmits a forward defect indication frame to a multipoint logical path in which the defect occurs. The transmitting end node having received the forward defect indication frame halts the use of the notified multipoint logical path, and transmits a frame in another path in which the forward defect indication frame is not received within a fixed time period.

Abstract: An optical network includes a plurality of subnets. The subnets each include a plurality of add/drop nodes coupled to the optical ring and operable to passively add and drop traffic to and from the optical ring. The network further includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets and to provide protection switching.

Abstract: An optical network includes an optical ring and at least three subnets. Each subnet includes a plurality of add/drop nodes coupled to the optical ring. The add/drop nodes are operable to passively add a first traffic stream in a first direction on the optical ring and a second traffic stream in a second direction on the optical ring. The first traffic stream comprises different content than the second traffic stream, and the first traffic stream and the second traffic stream are transmitted on the same wavelength. The network also includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and are operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets.

Abstract: Multiple working paths are established on each working rings and multiple protection paths are established on each of multiple protection rings. A working path on a first working ring spans across first and second nodes for signal transmission in a first direction of the ring, and a working path on a second working ring spans across the first and second nodes for signal transmission in a second, opposite direction of the ring. A protection path on a first protection ring spans across the first and second nodes for signal transmission in said second direction, and a protection path on a second protection ring spans across the first and second nodes for signal transmission in said first direction. The first and second nodes normally use the working paths, respectively. When one of the working paths fails, the first and second nodes use a corresponding protection path.

Abstract: Protection switching between primary and secondary paths in a packet-based network involves table entries that are pre-programmed with a primary path, a secondary path, and a value that identifies the primary path, referred to as a primary path identifier (PPI). When table entries are accessed to make forwarding decisions, the PPI is compared to a field that identifies that a particular path is down, referred to as a down path identifier (DPI). If the two fields match, (i.e., PPI=DPI), then the secondary path is selected instead of the primary path as the path on which the traffic should be forwarded.

Abstract: A digital information distribution system having a plurality of nodes that are connected to one another by counter-rotating data paths. Each node comprises a ring terminal that selects data packets from the data paths for use by the node and passes the remaining data packets to neighboring nodes. The data paths communicate data using asynchronous serial interface packets that transport video data or IP data.

Abstract: A failure protection between interconnected adjacent Resilient Packet Rings (RPRs) in a multiple RPR network is provided. Two paths, a regular message path and a protection path, are provided between two adjacent RPRs. The regular path is used for routing inter-ring messages when no failure has occurred on the path. Messages are rerouted through the protection path when a failure occurs on the regular path. Each of these paths has two RPR interface nodes (one for each RPR) that are connected to an interconnection device (a layer 2 bridge or a layer-3 router) through interconnection links. Procedures for detecting failures and generating notifications for message rerouting and fault reports are executed at the interconnection devices. The procedures use periodic keep alive messages for diagnosing network segment and interconnection device failures. The fault detection and message rerouting are accomplished in less than 50 ms.

Abstract: A method and apparatus for managing a loop network, the loop network (200) including at least one loop (206, 208), a plurality of devices (210) connected to the at least one loop (206, 208) via ports (211, 212), wherein at least two of the devices are initiators (207, 209). The method includes each initiator (207, 209) sending a frame to all other initiators (207, 209) in the loop network (200) identifying any ports (211, 212) which should not be used. Each initiator (207, 209) merges the information from all other initiators (207, 209) with its own information identifying any ports (211, 212) which should not be used resulting in all the initiators (207, 209) generating a single list of ports (211, 212) to be used which is consistent across all the initiators (207, 209). Each initiator (207, 209) applies an algorithm (300) to determine a common set of ports (211, 212) to be used by all the initiators (207, 209) and to balance port accesses across the loop network (200).

Abstract: A modular reconfigurable multi-server system with hybrid optical and electrical switching fabrics for high-speed networking within a wavelength-division-multiplexed based photonic burst-switched (PBS) network with variable time slot provisioning. An optical high-speed I/O module within the multi-server system includes an optical switch with the control interface unit. A server module of the multi-server system statistically multiplexes IP packets and/or Ethernet frames to be transmitted over the PBS network, generate control and data bursts and schedule their transmission. Then, the server E-O converts the bursts, and then transmits the optical bursts to the optical I/O module. The optical I/O module then optically transmits the bursts to the next hop in the optical path after processing the optical control burst to configure the optical switch, which then optically switches the optical data burst without performing an O-E-O conversion.

Abstract: A network component (3d) for an optical network (1) is described, including a coupling device (2; 4, 5) for optical coupling of the network component (3d) to the optical network (1), the coupling device (2; 4, 5) having a receiving module (4) and a transmitting module (5); a first data processing device (8, 9) which is unidirectionally connected to the receiving module (4); a second data processing device (10, 11) which is unidirectionally connected to the transmitting module (5); the first data processing device (8, 9) being unidirectionally connected to the second data processing device (10, 11) for transmitting data to the second data processing device; a detection device (4) for detecting the network status; and a two-way switch (23) for switching of the input of the first data processing device (8, 9) between the receiving module (4) and the output (19) of the second data processing device (10, 11) as a function of the network status detected.

Abstract: A network is protected against interruption of service while one or more faulty switches or optical fiber transmission lines are repaired or replaced, by an interconnecting configuration of small N×N optical input/output switches, where N is 2 or greater than 2. The switches are configured among protection and working transmission lines. The small number of fibers for each switch improves repair and installation connection reliability and permits configurations that flexibly meet differing requirements. Also the fault is monitored with a fault check signal.

Abstract: A method for enabling recovery of data stored in a computer network, the computer network comprises a plurality of computer nodes, the method comprising the steps of generating a set of redundancy data based on a predetermined relationship between a first set of data and a second set of data, injecting the first set of data, the second set of data and the set of redundancy data into separate looping paths of the computer network, wherein a looping path is a path along a plurality of computer nodes in which data is transported, and the looping paths are defined in separate communication channels between the computer nodes and pass through at least one common node of the computer network, such that the redundancy data and the second set of data can be used to reconstruct the first set of data based on the predetermined relationship between the first and second set of data when the first set of data is lost, thereby enabling the recovery of data stored in the computer network.

Abstract: A storage system having multiple I/O interface ports is configured to detect a failed communication condition at a port. The storage system is configured to then attempt communication using a port configuration of another port that also exhibits a failed communication condition. If communication is established, the port is reconfigured using the configuration of the other port.

Abstract: A frame relay (FR) protection method generates an OAM frame to other nodes upon detecting a defect on a SONET ring. The protection frame comprises a type of failure and a location of failure. A node that detected the defect transmits the protection frame to other nodes about the location of the failure and the type failure. Protection tables are provided for switching a working fiber link to a protection fiber link. A protection switching provides a method re-establish FR traffic in spite of a detected failure on a SONET ring.

Abstract: An optical network includes an optical ring and a plurality of add/drop nodes coupled to the optical ring. Each of the add/drop nodes is operable to passively add and drop one or more traffic streams to and from the optical ring, and each traffic stream comprises a channel. A hub node also coupled to the optical ring is operable to selectively pass and terminate individual traffic streams.

Abstract: A method for a communications network with a protect channel transmitting protect channel data and working channel transmitting working channel data includes transmitting the working channel data via the protect channel upon a disruption in the working channel, and restoring the transmitting of protect channel data, wherein the restoring includes applying a mesh restoration protocol to the communications network to restore the transmittal of the protect channel data. The restoring includes finding one or more alternate channels to transmit the protect channel data, the one or more alternate channels including connected working and protect channels.

Abstract: In a ring having first and second adjacent nodes, and two fibers carrying information between the first and second nodes, the first fiber carries information in one direction, while the second fiber carries information in another direction. Each fiber includes wavelength capacity allocated to working and protection traffic. The working and protection wavelength capacities in the first fiber are respectively assigned to first and second disjoint sets of wavelengths, while the working and protection wavelength capacities in the second fiber are respectively assigned to the second and first disjoint sets of wavelengths.

Abstract: A SONET/SDH architecture is disclosed that enables the multiplexing of STS-1's from different SONET/SDH rings into a single STS-N for transmission via a single optical fiber, but while maintaining the association of each of the STS-1's with its respective SONET/SDH ring. For example, when an STS-48 carries 12 STS-1's from a first SONET/SDH ring and 12 STS-1's from a second SONET/SDH ring, the STS-48 carries: the automatic protection switching channel for the 12 STS-1's from the first SONET/SDH ring (with addresses specified in the address space of the first SONET/SDH ring); and the automatic protection switching channel for the 12 STS-1's from the second SONET/SDH ring (with addresses specified in the address space of the second SONET/SDH ring).

Abstract: A redundant link management switch for use in a stack of switches forming a closed-loop link topology, including a stacking module, a processor and a management module. The stacking module has an uplink port for connecting a next-higher switch in the stack and a downlink port for connecting a next-lower switch in the stack. The processor instructs the stacking module to disable a downlink control bus within the downlink port when receiving a disconnect command, and instructs the stacking module to enable the downlink control bus when receiving a reconnect command. The management module asserts the disconnect command if a link status, received from the processor, indicates that the redundant link management switch and the stack of switches are stacked into the closed-loop link topology. Additionally, the management module asserts the reconnect command to recover a redundant link if the management module detects that the closed-loop link topology is changed.

Abstract: Methods, systems and computer program products provide for recovering from the failure of a primary distribution processor which provides secure communications over a network in a distributed workload environment having target hosts which are accessed through the primary distribution processor by a common network address. Information sufficient to restart communications through the primary distribution processor utilizing network security is provided to a backup distribution processor. Failure of the primary distribution processor is detected and the communications utilizing network security restarted at the backup distribution processor utilizing the provided information. Both inbound and outbound communications with target hosts utilizing the common network address and which are associated with a secure network communication are then routed through the backup distribution processor.

Abstract: In one embodiment, a network element is to be coupled to a first and second span of a number of spans that interconnect a set of network elements to form a ring network. In addition, each of the spans has two sub-spans on which traffic travels in opposite directions on a number of channels that circumvent the ring. Additionally, the channels on each sub-span include working channels and protecting channels. Furthermore, the network element includes a traffic handler to reprogram, responsive to protection switches and un-switches, the connection configuration on the protecting channels of the sub-spans of the first and second spans that provide traffic to the network element.

Abstract: An apparatus and method for a communications network including at least one interface circuit reads frame data received from the communications network and writes frame data to be transmitted over the communications network, the frame data including a plurality of transport overhead fields. The apparatus includes signature logic coupled to the interface circuit, the signature logic identifying signature data and writing the signature data into transport overhead fields in an outgoing frame. Reflector logic coupled to the interface circuit copies data from one of the received transport overhead fields, the copied data being placed into a transport overhead field in the outgoing frame, the copied data including the received signature data. The interface circuit compares the copied data to earlier received frame data from the communications network, the determination of a mismatch identifying a transition requiring an update of at least one routing table.

Abstract: The invention relates to a method for determining the used bandwidth (CCR) on a connection (18) on which information-carrying units are transported. The duration (ET) of an arrival period, during which a predetermined number (M) of the cells arrives at a certain point of the connection (18), is measured and stored. The bandwidth (CCR) at an arbitrary point of time (GT) is set to the predetermined number (M) per the stored duration (ET), if the point of time (TS) when the duration (ET) was stored is not longer ago than a predetermined threshold time interval (THR) at the arbitrary point of time (GT).

Abstract: Units of traffic are routed between nodes in a network on corresponding sets of trunks, such that the traffic is balanced between disjoint paths. A restoration process for the traffic is implemented using service layer or transport layer switching. In a first embodiment, first and second nodes are connected by first and second sets of trunks, with each of the trunks in a given set of trunks supporting a designated portion of a given one of the units of traffic. The units of traffic are then routed such that a first half of a given one of the units of traffic is routed on a first one of the trunks in a given one of the sets of trunks, and a second half of the given unit is routed on a second one of the trunks in the given set of trunks. In other embodiments, the first and second nodes are connected by first and second sets of trunks so as to form a four-trunk ring, with each of the first and second sets of trunks including a primary trunk and a backup trunk.

Abstract: A node apparatus for a ring network arranged in a multi-ring formation includes a routing table that defines relationships between a receiving physical line identifier with port number and a sending physical line identifier with port number for virtual ring bypass routes, the relationships being individually provided for respective transmission lines connected to the node apparatus. A detection unit detects, at a time of detection of a failure, each of the relationships from the routing table to determine a transmission line to which a switching request is sent. The detection unit detects, at a time of relaying, each of the relationships from the routing table to determine a transmission line to which one of a switching request and a switching response is sent. The detection unit detects, at a time of receiving of a switching request, each of the relationships from the routing table to determine a transmission line to which a switching response is sent.

Abstract: Systems and methods for link discovery and verification technique that minimize the need for line termination resources that generate and interpret packets. Of two nodes verifying a link to one another, only one node need have any line termination capability. The node lacking line termination capability simply loops back packets generated by the other node thus verifying the link. Thus, an optical cross-connect can verify links to a wide variety of node types by employing a single line termination unit capable of terminating any suitable packet type. Alternatively, a router can verify connectivity to an optical cross-connect even when the optical cross-connect lacks any line termination capability at all. This saves greatly on implementation costs for optical networks.

Abstract: A communication device for interconnection of first and second networks, of which at least the first network is a bidirectional ring network, includes first and second interconnect modules, each such module adapted to receive outgoing data traffic on the first network at a data rate not substantially greater than a predetermined maximum rate for one of the ring directions, and to convey the outgoing data traffic to the second network. When a fault occurs in one of the first and second modules, the other module is reconfigured to receive substantially all of the outgoing data traffic and to convey the outgoing data traffic to the second network regardless of whether the outgoing data traffic is transmitted on the first network in the clockwise or in the counterclockwise direction.

Abstract: A transmitting apparatus for cross connecting and transmitting main signals which enter via ring-configured transmission lines to which working and protection channels have been assigned in first and second directions, and rescuing a main signal by looping back the main signal in the opposite direction using the protection channel when a transmission line fails. Storing non-rescue information which indicates whether each channel that is the object of rescue by loop-back is a non-rescue channel. Determining whether a failure for which rescue is impossible has occurred in each channel, which is the object of rescue, other than a non-rescue channel. On the basis of main-signal cross-connect information, interchanging a result of discrimination of each channel and inserting the interchanged result of discrimination in the main signal of the corresponding channel after cross connect.

Abstract: The present invention is directed toward a distributed intelligence fiber-optic communication network in which node control processors (NCPs) associated with each network element periodically transmit identification and status information to the other NCPs in the network. Various faults in the network can thus be readily identified, and appropriate tasks for modifying the network in response to the fault (such as rerouting around a defective network element) can be carried out. Further, information continues to be distributed among the NCPs even if a break occurs in a segment of fiber in the network.

Abstract: A data storage system includes controller nodes and a storage component. The controller nodes couple the storage component to a host. The storage component includes a controller and sleds with disk drives. The host and the storage component form an arbitrated loop. When the arbitrated loop is down, the controller removes the storage component from the arbitrated loop so the controller, the sleds, and the disk drives form an internal loop. When the internal loop is also down, the controller tests each of the sleds individually and marks those that are not responding properly. If a sled is responding properly the controller tests each of the drives in that sled individually and marks those that are not responding properly. The controller adds back into the internal loop the sleds and the drives that are not marked as bad, and then the storage component back into the arbitrated loop.

Abstract: A system and a method of operating the system for non-disruptively inserting a node into the operations of an ATM ring uses the ring operations to update topology information and routing tables at the existing nodes to include therein the new node and one or more virtual paths associated with the new node. Basically, the node to be inserted establishes communications with a ring hub node over an established intra-ring management channel. The node and the ring hub node then exchange information over the management channel and the node performs its initializing routines in order that the node may operate to pass through traffic on the existing virtual paths. The new node next requests from the hub node the assignment of one or more virtual paths for directing traffic between that node and other nodes on the network. In response to the request, the hub node assigns one or more virtual paths to the requesting node and establishes a signaling channel to the node over one of the virtual paths.

Abstract: A method of operating a data transmission network (10) is described comprising at least two outer rings (11, 13) and a middle ring (12) which are coupled to one another via nodes (14, 15, 16). One of the nodes (14) represents a central node for all three rings (11, 12, 13). Switching devices (23, 24, 25, 26) for the establishment of connections are contained in each of the nodes (14, 15, 16). It is recognized that a connection is to be established from the one outer ring (11, 13) to the other outer ring (13, 11) via the middle ring (12). Then the connection is established taking into account all three rings (11, 12, 13).

Abstract: A network element receives frames from multiple ring networks. Each ring network linked to the network element is supported by a designated support program. The received frames are monitored for conditions indicative of a failure in one of the ring networks. Upon detection of a failure condition, the designated support program for the failing ring network is determined and notified. The designated support program then addresses the failure condition by, for example, switching to a backup link. In one example, the multiple ring networks are SONET BLSR networks.

Abstract: An optical communication switch operative in a communication network which is adapted to enable protection of a segment, or a number of segments, along an optical path in the communication network.