Abstract: In one embodiment, an intermediate node includes one or more active forwarding planes and one or more redundant forwarding planes. The intermediate node may also include one or more active control planes and one or more redundant control planes. A test packet is generated, in some cases by a redundant control plane, and transferred to a redundant forwarding plane. The operational state of the redundant forwarding plane is verified, at least in part, by using operational software and hardware contained in the redundant forwarding plane to forward the test packet from the redundant forwarding plane to a target line card. The target line card loops the test packet back to the redundant forwarding plane as part of the verification process. In some cases, the redundant control plane processes the looped-back test packet.

Abstract: A method for preventing information losses due to network node failure is disclosed. The method comprises the steps of operatively connecting at least one backup node to a primary node, followed by synchronizing the at least one backup node and the primary node. Next, the method comprises receiving, from a first endpoint, ingress traffic in the primary node and replicating the ingress traffic to the at least one backup node. Next, the method outputs, from the primary mode, primary egress traffic and outputs, from the at least one backup node, backup egress traffic. The method then determines if the primary node has failed. Then, the method transmits, to a second endpoint, the primary egress traffic if it is determined that the primary node has not failed, and transmits, to the second endpoint, the backup egress traffic from a selected one of the at least one backup nodes if it is determined that the primary node has failed.

Abstract: A media gateway system and a method of substituting one unit for another in the system. The system uses cross point switches that are controlled by a main control unit. When a voice processing unit or a circuit interface unit or a packet interface unit malfunctions and another unit takes over the function of the malfunctioning unit, only the cross point switch setups need to be modified and not the settings in the TDM switch or the packet switch.

Abstract: A routing system provides for transparent routing system failover by checkpointing route prefixes during normal operation by maintaining a route prefix table. After failure of a primary routing processor, routing with peer routing systems is synchronized through the use of this prefix table. The prefix table is managed by the primary routing processor and is accessible by a backup routing processor at least after failure of the primary routing processor. Upon the detection of a failure, a backup routing processor solicits routes from peer routing systems in response to the failure and generates a backup routing database from the routes received from peer routing systems. The backup routing processor also compares prefixes of routes in the backup routing database with prefixes in the prefix table, and sends route withdraw messages to the peer routing systems for routes having prefixes listed in the prefix table and not identified in the backup routing database.

Abstract: A data communication network includes a plurality of primary virtual bridges, interconnected by primary virtual connections so as to transmit and receive data packets over the network to and from edge devices connected thereto. One or more backup virtual bridges, each associated with at least one of the primary virtual bridges, are connected by at least one secondary virtual connection to at least another one of the primary virtual bridges, so that upon a failure of one of the primary virtual bridges with which it is associated, the backup virtual bridge transmits and receives the data packets over the network via the at least one secondary virtual connection in place of the at least one of the primary virtual bridges.

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 parallel router comprising: 1) a plurality of routing nodes, each of the plurality of routing nodes capable of receiving message packets from and transmitting message packets to external devices, wherein the each of the plurality of routing nodes maintains a routing table suitable for routing message packets from transmitting ones of the plurality of routing nodes to receiving ones of the plurality of routing nodes; and 2) a switch fabric capable of transmitting the messages packets between the transmitting nodes and the receiving nodes, wherein a designated one of the plurality of routing nodes is operable to transmit to at least one non-designated one of the plurality of routing nodes a hello request message operable to cause the non-designated routing node to transmit back a hello acknowledgment message, wherein the designated routing node monitors a time duration between transmission of the hello request message and receipt of the hello acknowledgment message to determine if the non-designated routing n

Abstract: The HA IS-IS system provides a redundant backup IS-IS protocol instance that can seamlessly assume the function of the active IS-IS instance in the event of active MCP failure. Once the backup is online, the active synchronizes its global, interface, adjacency, neighbor, and LSP system state information. In the ongoing synchronization phase, the active and the backup maintain synchronization using a combination of explicit message updates from active to backup together with message flow-through. In the recovery phase, the operating system detects the failure of the active and notifies the backup, which assumes the active function as a standalone system without reconfiguring or interrupting traffic among peer network routers, and starts computing forwarding tables and updating routing tables.

Abstract: Transparent redundancy may be achieved at a MPLS-MPLS hierarchical boundary or a BMA-MPLS hierarchical boundary by utilizing local repair mechanisms extant in each domain to select automatically the same boundary network devices as the primary and secondary boundary network devices. In the MPLS domain, two LERs advertise the ability to forward traffic to a phantom LER and map all traffic originated into that domain as having been on a path originating at the phantom LER. This will cause the LERs to appear as being one hop away from the phantom LER, causing MPLS to assume the real LERs are part of a LSP terminating at the phantom LER. MPLS local repair will thus establish one of the LERs as the primary LER and the other LER as the secondary LER. In an Ethernet domain, each boundary network device is treated analogously to a router in the VRRP scheme for routers.

Abstract: A method for resolving primary section mismatch at a local node coupled to a remote node with two working sections is disclosed. A first working section is initially identified as the primary section and a second working section is initially identified as the secondary section. The primary section supports network traffic and the secondary section operates as a backup for the primary section. The method includes receiving a status indication change of the working section identified as the primary section at the local node and switching the primary section to the second working section at the local node. A timer is started upon switching the primary section to the second working section at the local node and the primary section is switched back to the first working section at the local node after the timer expires if the other node has not switched its primary section.

Abstract: A parallel router comprising: 1) a plurality of routing nodes, each of the plurality of routing nodes capable of receiving message packets from and transmitting message packets to external devices, wherein each of the routing nodes maintains a routing table suitable for routing message packets from transmitting ones of the plurality of routing nodes to receiving ones of the plurality of routing nodes; and 2) a switch fabric capable of transmitting the messages packets between the transmitting nodes and the receiving nodes, wherein a designated one of the plurality of routing nodes is operable to receive from non-designated ones of the plurality of routing nodes link state advertisement (LSA) message packets containing link state information, wherein the designated routing node aggregates the LSA message packets to thereby form a link-state database.

Abstract: A method and system for providing protection of data communications in packet-based networks is provided, using a combination of unicast to multicast conversion and providing formation of virtual output queues (VOQs) which are separate for each pair of the target port and protection ports on the target network device. As a result, the system requires less bandwidth resources and reduces or eliminates network performance problems associated with other existing solutions.

Abstract: A method for selecting an active router in a communication device includes providing multiple routers in the device, coupling the routers to a single physical link, monitoring a status for each of the routers, and selecting one of the routers as an active router by positioning its corresponding relay.

Abstract: A hanging protocol simulator system and method permit the design and storage of hanging protocol without requiring the actual hardware utilized in the design. The creation and/or modification of hanging protocols can be made either: a) automatically, by sending images to the simulator and receiving the configuration based on these images, or b) manually, in which case the user utilizes a hanging protocol editor to define the preferred screen layout. The user can define a preferred screen layout and then test it, without need of available real hardware, and can check the performance of the configuration long before investing in the ultimately required hardware. A database is provided for storing hanging protocols which can be accessed, and/or user-provided input can further be provided to define or refine hanging protocols.

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: High availability BGP4 is based on redundant hardware as well as redundant software that replicates the RUN state of BGP4. There are two copies, respectively active and backup, of BGP4 running on two separate redundant hardware platforms. All BGP4 internal implementations apply various methods to replicate the running state of BGP4 independently of peer network routers. When this hardware or software fails on one redundant hardware platform, peer routers are unaware of the failure. Internally, based on duplicative states, the local router recovers from the failure and keeps the protocol running. During the recovery period, the local router can bring up a backup again. In the HA architecture, these activities are not detected by peer routers, such that there is no instability to the Internet backbone caused by BGP4 failure.

Abstract: Disclosed are methods and apparatus for providing redundant data forwarding or routing capabilities. In one embodiment, a network device includes a designated router and a non-designated router. The designated router generally provides layer 3 switching or routing for data received into the network device. Although the non-designated router is active, it generally does not provide forwarding capabilities until the designated router fails. The non-designated router's logical interfaces are disabled, while the designated router's logical interfaces are enabled. The non-designated router becomes the new designated router when the first designated router fails. In general terms, the routers of the network device provide redundancy with the network being aware of only a single router within network device. That is, the network is only aware of a single router. This is accomplished by having the routers share the same IP and MAC address on each logical interface.

Abstract: Systems and methods are described for providing network route redundancy through Layer 2 devices, such as a loop free Layer 2 network having a plurality of switching devices. A virtual switch is coupled to the loop free Layer 2 network, the virtual switch having two or more switches configured to transition between master and backup modes to provide redundant support for the loop free Layer 2 network, the switches communicating their status through use of a plurality of redundancy control packets. The system also includes means for allowing the redundancy control packets to be flooded through the Layer 2 network. The means may include time-to-live data attached to the redundancy control packet which is decremented only when the packets are transferred through devices which are configured to recognize the protocol used in redundancy control packets.

Abstract: A method, system, apparatus, and signal-bearing media for determining connectivity information for routers running on servers that are attached to a device. A router is resigned in favor of a corresponding router at another server when the corresponding router has better connectivity to the device, where partial connectivity is better than no connectivity, and full connectivity is better than partial connectivity.

Abstract: A router includes at least two router modules, one of which is in an active state at any given time, the others being in a standby state, and a changeover capability making it possible to cause one of the other router modules to go from a standby state to an active state when the router module in the active state stops, each of the router modules having connections with one or more networks, and having at least one state machine, each state machine managing the interface associated with one of the connections. In the router, each of the router modules has data storage capability which, in the active state, enables it to store data relating to the state of the at least one state machine, when the machine is in a stable state, and data retrieval capability for retrieving the data when a changeover takes place.

Abstract: Packets of different priorities are efficiently distributed to a plurality of links of different qualities. When transmitting a low priority packet, the load on a higher quality link is examined, and if the load is not greater than a predetermined value, the low priority packet is transmitted on the higher quality link. If the load on the higher quality link is greater than the predetermined value, the low priority packet is transmitted on the low quality link.

Abstract: A router made up firstly of at least two router modules, only one of which is in an active state at any given time, and secondly of a changeover device making it possible to cause one of the other router modules to go from a standby state to an active state when the router module in the active state stops, and the router modules having state machines associated with each of the neighbor routers, wherein each of the router modules has a data storage device which, in the active state, enables it to store data relating to the states of the state machines, when the machines are in stable states, and a data retrieval device for retrieving the data when the router module changes over to the active state.

Abstract: Supportably mounted by each chassis of a multi-chassis broadcast router are primary router matrix cards, redundant router matrix cards and clock-demanding input and output cards. A first master clock resides on the primary router matrix card of a first chassis while a second master clock resides on the redundant router matrix card of a second chassis. Each master clock is configured to provide a respective common clock signal to all of the input and output cards of the first and second chassis. Control logic determines whether the first master clock or the second master clock issues the common clock signal.

Abstract: The invention provides a route updating method which reduces the flow rate of updating notifications, which are circulated in a network, to improve the scalability. A micromobility network includes routers connected in a tree connection and radio base stations connected to the routers in the lowest layer such that an updating notification of a route from a mobile terminal is repeated in order from a radio base station to successive higher order routers to update the route and a packet is distributed along the updated route. In the mobility network, directly lower order routers to each router are numbered to the numbers 1 to n with reference to the direct lower order router accommodation number n, and a route from the radio base station to the router in the highest layer represented by a route number composed of the numbers of the thus numbered routers is applied to the radio base station.

Abstract: A cell switch module having a unit cell switching function and placeable in either an active state or a standby state. The module comprises a plurality of input ports for inputting cells thereto, a plurality of output ports for outputting cells therefrom, and a cell switching controller to execute such control that, in response to an active/standby switching instruction, a decision is made as to whether the input cell is a specific first cell or not, and if the input cell is detected to be the first cell in the active state, any subsequent cell inputted thereafter is not switched, but if the input cell is detected to be the first cell in the standby state, any subsequent cell inputted thereafter is switched.

Abstract: Various media stream processing systems and methods are provided. In one exemplary embodiment, a media stream processing method is provided that includes the brokering of a number of communications channels between a communications network and a packet switched network with a number of media stream processors. Each of the communications channels is specified by a profile having a number of channel parameters. The method also includes storing each of the profiles in a standby media stream processor when each of the media stream processors is operational. Finally, the method includes brokering respective ones of the communications channels originally brokered by one of the media stream processors with the standby media stream processor upon a failure of the one of the media stream processors.

Abstract: Disclosed are methods and apparatus for facilitating recovery of a data connection that was established between an active router and a host. The data connection is a type of connection that tracks the sequence of data sent between the router and the host. This recovery may occur after a standby router takes over for the active router. For example, a Transmission Control Protocol (TCP) connection between the active router and a host may be recovered after a router switchover (e.g., when the standby router takes over for the active router in a hot standby router protocol system). To accomplish this, at least one sequence number that is associated with data sent from the active router (to the host) is sent to the standby router, and at least one sequence number from data sent from the host is also sent to the standby router. For example, the sequence numbers correspond to the initial SYN packet sent by the active router and the SYN packet sent by the host in response to the active router's SYN packet.

Abstract: A distributed digital cross-connect system (10) is provided. The system includes two or more network interface islands (12) that connect to the telecommunications network. The system (10) also includes one or more distributed services nodes (18). Each distributed services node (18) connects to two or more of the network interface islands (12). The network interface islands (12) can transmit data to each other through the distributed services node (18). An administration system (14) is also connected to each distributed services node (18) and each network interface island (12). The administration system (14) transmits matrix configuration and telecommunications channel routing data to the network interface islands (12) and the distributed services nodes (18).

Abstract: A system and method of controlling a bi-directional switching operation for a synchronous transfer mode (STM-1) signal transmission line of an asynchronous transfer mode (ATM) switch is disclosed. The system and method provide a rapid bi-directional switching operation through a 1+1 structure, being compatible with a 1+N structure, using MSP (Multiplex Section Protection) protocol. The process includes determining whether a signal fail has occurred, determining whether a priority of the signal fail is higher than that of a current signal fail determining whether a target station uses the same protocol as a source station if the priority of the signal fail is higher and performing a switching operation and transmitting a switching notification signal to the target station if the same protocol is used by the target station.

Abstract: An apparatus having n-number of working cross-connects for cross-connecting an n-bit input signals arriving from a plurality of input paths on a per-bit basis; n-number of first logic circuits for calculating the exclusive-ORs of each said n-bit and applying outputs to a standby cross-connect for providing outputs; n-number of second logic circuits for calculating the exclusive-ORs of said output signals from each of said working cross-connects and from the single standby cross-connect; and third logic circuits for selecting output signals of said working cross-connects and outputs of the second logic circuits. The apparatus detects the occurrence of an abnormality in working cross-connects by monitoring the outputs of the second logic circuits, identifies the faulty cross-connect by successively turning off one of the n-inputs to the first and second logic circuits, and select outputs from the second logic circuits instead of from the faulty cross-connect by using the third logic circuits.

Abstract: A communication network includes first and second terminals, nodes, and links. The first node is coupled to the first terminal through the first link, and coupled to the second terminal through the second link and the second node. The first node preferably includes communication paths, each coupled to one corresponding first link and to the second link, through a multiplexing device, and routing signals between the links. The first node also preferably includes an alternate communication path coupled through the multiplexing device to the second link, a switch coupled to the alternate path, and a detector detecting failure of a communication path. A controller is responsive to the detector detecting a failure in a communication path and controls the switch to couple the alternate path to a corresponding first link, thereby enabling a signal to be routed between that first and second links through the alternate path.

Abstract: A fabric access device having a plurality of system interfaces is disclosed. The fabric access device includes a fabric interface configured to receive data from and send data to a switch fabric and a routing circuit configured to send data received on one of the plurality of system interfaces to the switch fabric via the fabric interface. The inclusion of a plurality of system interfaces facilitates a variety of configurations that provide different levels of redundancy and optimize use of available bandwidth.

Abstract: The present invention relates to a method and system for implementing protocol redundancy in a router. In particular, the invention relates to providing redundancy of multi protocol label switching (MPLS). In one aspect, the present invention provides MPLS redundancy wherein all protocol states are mirrored. An active processor provides MPLS operations. In the present invention, a standby processor is coupled to the active processor. During the initial synchronization, all protocol information from the active processor is forwarded to the standby processor. The protocol information can include event information and state information. Thereafter, any updates of protocol information are immediately forwarded to the standby processor in an orderly and controlled manner. Upon failure of the active processor, the standby processor takes over as the active processor. All MPLS protocol operations are performed on the new active processor.

Abstract: The present invention relates to a message transmission system, and more particularly, to a control apparatus and method for relay node duplexing. In the invention, when the exchange of the active node relaying a message by buffering is requested, the duplexing control unit of the active node controls such that the active node performs only the message transmission function, and the duplexing control unit of the standby node controls such that the standby node performs only the message receiving function. When the messages already inputted to the active node before the exchange request are all transmitted, the completion of the exchange is controlled, and when the exchange is completed, the standby node obtains the active right, thereby preventing the loss of a message during the exchange operaiton.

Abstract: A system and methods are shown for providing packet data serving node (PDSN) redundancy. One exemplary method includes providing an access node with a plurality of packet data serving nodes and at least one system manager, establishing an N to 1 redundancy of active to standby PDSNs. Upon establishing a communications session with a mobile node, each active PDSN provides state updates to the standby PDSN including only non-recoverable data. Upon failure of any active PDSN, the standby PDSN reassigned as an active PDSN replacing the failed unit and assuming the communications session with the mobile node. The remaining active PDSNs are notified of the reassignment and transmission of updated state data is discontinued.

Abstract: A cross point switch is configured to select from one of a first stream of ATM cells and a second stream of ATM cells, the first stream and the second stream being identical, and is further configured to select and substitute the second stream for the first stream upon detection of an error condition in the working circuitry operation on the first stream. The working circuitry, which is located on an interface module, is configured to receive and operate on the first stream of ATM cells. The protection circuitry, which is located on a redundant interface module, is configured to receive and operate on the second stream of cells. The protection circuitry and the working circuitry are functionally identical and synchronized to each other so that switching occurs from one stream to the other without interruption of network service.

Abstract: An apparatus and technique configures an intermediate network node, such as an aggregation router, to implement automatic protection switching (APS) redundancy among its line cards in the event of a failure to one of those cards. The APS line card redundancy provides redundancy among a pair of line cards connected to a performance routing engine of the router. Internal APS data paths are implemented in the router through the provision of an alias logic circuit that selects packet data from one of an adjacent pair of line cards and sends identical copies of data to that adjacent pair of line cards.

Abstract: A redundant remultiplexer includes two media control modules, wherein, if the primary module operates in an input mode, the backup module performs the same processing of packets as the primary module but only transmits processed packets to a switch if the primary module fails, and wherein, if the primary module is operating in an output mode, the backup module performs the same processing as the primary output module on the same sequence of packets received from the switch, but the backup module only outputs the processed packets if the primary module fails.

Abstract: A method and apparatus allows for continued operation of one or more applications running at a network device with reduced delay despite crashes or failures at that device. The network device includes two or more supervisor cards for running the applications and a plurality of line cards. According to the invention, one supervisor card is designated the active supervisor card and one supervisor card is designated the standby supervisor card. As changes in state and other operating conditions take place on the active supervisor events are generating for passing at least some of this information to the standby supervisor where it is stored. Following a crash or failure of the active supervisor card, the standby becomes the newly active supervisor card. The standby supervisor performs a consistency check with the line cards and resets those that fail the check.

Abstract: A header conversion device allowing reduced amount of hardware and memory and high-speed line switching is disclosed. In an ATM switching device having redundant incoming line systems, a header conversion table stores a set of header conversion information for one of the redundant incoming line systems. A header converter converts the header of an ATM cell received from each of the redundant incoming line systems by referring the same set of header conversion information.

Abstract: A method and apparatus for effecting 1:1 or N:1 equipment protection switching in the line units of a voice-and-data access and transport network includes three sets of switches associated with the line units that can be selectively provisioned by the system operator into protect groups. In one embodiment, the switches are arranged and controlled within the protect groups by one or more dedicated microprocessors such that, upon the failure of a protected one of the line units in a protect group, the stream of traffic to an associated, protect one of the line units in the protect group is dropped, and the traffic stream to the failed line unit is switched over to the protect line unit for continued processing.

Abstract: A change of switch plane operation is performed in a multi-plane cell switching node (20) which has a first switch plane (22); a second switch plane (24); and plural switch port interface units (26). In response to detection of a fault in the active switch plane, the passive switch plane sends a plane change cell to the plural switch port interface units, and stops egress traffic flow from the second switch plane. Upon receiving the plane change cell, each switch port interface unit redirects traffic cells sent from the active plane to the passive switch plane. Each switch port interface unit then determines when traffic cells destined thereto have been flushed from the first switch plane, and changes its active switch plane designation (so that the formerly passive switch plane becomes the active switch plane) so that egress traffic flow can begin from the formerly passive (now active) plane to the respective switch port interface units.

Abstract: An ATM switching system 10 includes an EMA 20 and CPUs 30 and 40 as currently acting and subsidiary systems, respectively. The CPUs 30 and 40 are connected via connecting lines 50a and 50b to a network 60. Each CPU 30 (or 40) includes a system controller 32 (or 42), a MAC/IP address controller 33 (or 43) and a MAC/IP address setter 34 (or 44). Each MAC/IP address controller 33 (or 43) has a MAC/IP address management table 35 (or 45) for managing MAC, IP and other kinds of addresses, and outputs a MAC/IP address retrieval result according to the MAC/IP address retrieval caused by it.

Abstract: A method and apparatus for providing an active standby control system comprising the steps of providing a first programmable logic controller and a second programmable logic controller, each controller having an operating state. A sub-network is formed by operably connecting the programmable logic controllers to an IO module with a fiber optic cable and a network connector. Data is transmitted over the sub-network at a rate of at least 100 Mb/s. A network identifier, i.e., Internet Protocol or Media Access Control address, is associated with each programmable logic controller. The network identifier of each controller is determined in response to the operating state of the respective programmable logic controller. The network connector can be a switch or a hub to assist in avoiding signal collisions and maintaining determinism on the sub-network.

Abstract: 18A method and system for controlling the switching and control operation of at least one of an Softswitch system, an Signal Transfer Points (STP) and a gateway (GW) (e.g., in a SS7 signaling environment). By providing support for redundancy, a second switch system can take over the routing and control operations of a first switch system when the first switch system experiences difficulty. Difficulty may be any one of several forms (e.g., switch crash, congestion, hardware failure).

Abstract: Methods and apparatus for providing a device for forwarding packets in a network are disclosed. A first router and a second router having a shared set of interfaces are provided, enabling the first router and the second router to share forwarding data for forwarding packets on the shared set of interfaces.

Abstract: A data transmission system and method for transmitting packetized data from an Internet Protocol (IP) host, having at least an IP layer and a network layer, to a plurality of workstations by the intermediary of an IP network, wherein the IP host is connected to the IP network via a layer 2 network interfacing the IP network with a set of routers. The IP host further includes a Multiple Address Resolution Protocol (MARP) layer between the IP layer and the network layer for selecting one of the set of routers in response to the next hop IP addresses provided by the IP layer to the MARP layer when a packet of data is be transmitted from the IP host to one of the workstations.

Abstract: The invention relates to an apparatus for the transmission and the reception of data comprising: a plurality of inputs and a plurality of corresponding outputs for the respective coupling to the incoming part and outgoing part of a plurality of links, wherein, to each input and to each output, is associated a respective switching device (141, 142, 143, 144), for each couple of input and output, an active terminating board (121) for coupling this input and this output and for further transmitting data, at least one spare terminating board (122) which is able to replace a defective active terminating board, each terminating board comprising means (201) adapted to test the quality of the link (W) to which it is associated and to compare said quality to a predetermined criterium and to generate a control signal to first control means (261, 281) of said each terminating board, the first control means being adapted to replace the defective link by another link, if this quality does not comply with the predetermi

Abstract: A method for extending the switching matrix of a communication system without interruption which is effected by reserving space for the routing addresses of the largest extension stage both in the header translation table of the interface devices and in the cell header of each ATM cell, and by providing a system split which is used to replace the old switching matrix assemblies with new switching matrix assemblies in steps, the paths via the new switching matrix assemblies, insofar as they lead to the same output-side interface devices as via the old switching matrix assemblies, being addressable using the same routing addresses.

Abstract: A crossbar switch system with redundancy has N+1 cross-bar switches. A first cross-bar switch has first outputs of each of a plurality of nodes applied to N input terminals thereof, an (N+1)th cross-bar switch has Nth outputs of each of the nodes applied to N input terminals thereof, and second to Nth (Ith) cross-bar switches each have first to Nth selection circuits, which are provided at respective input terminals thereof, to each of which are input mutually adjacent (I?1)th and Ith outputs among outputs of each of the nodes. Each (Jth) node has N selection switches, which are provided at input terminals thereof, to each of which are input Jth outputs of two mutually adjacent cross-bar switches among the first to (N+1)th cross-bar switches. In response to a selection control signal output from a failure processing circuit that executes crossbar switch failure processing, each of the selection circuits selects and outputs one of its two inputs.