Wiring closet redundancy

Systems and method for providing redundancy of communications and/or inline power to a powered Ethernet device are disclosed. A redundancy device is configured to receive in-line data and/or power from a plurality of Ethernet relay uplinks and to monitor communications between the relay uplinks. One of the relay uplinks is established as an active state uplink and passes data and/or power to the power device. Responsive to a switchover communication from a redundant uplink, the redundancy device establishes the redundant uplink as the active uplink, thereby passing data and/or power from the redundant uplink to the power device. The relay uplinks may use packet-based communication to sense when there is a failure in a link, and replace a failed device with a redundant device.

FIELD OF THE INVENTION

The present invention relates generally to networking equipment which is powered by and/or powers other networking equipment over wired data telecommunications network connections.

BACKGROUND OF THE INVENTION

Inline Power (also known as Power over Ethernet and PoE) is a technology for providing electrical power over a wired telecommunications network from power source equipment (PSE) to a powered device (PD) over a link section. The power may be injected by an endpoint PSE at one end of the link section or by a midspan PSE along a midspan of a link section that is distinctly separate from and between the medium dependent interfaces (MDIs) to which the ends of the link section are electrically and physically coupled.

PoE is defined in the IEEE (The Institute of Electrical and Electronics Engineers, Inc.) Standard Std 802.3af-2003 published Jun. 18, 2003 and entitled “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements: Part 3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications: Amendment: Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI)” (herein referred to as the “IEEE 802.3af standard”). The IEEE 802.3af standard is a globally applicable standard for combining the transmission of Ethernet packets with the transmission of DC-based power over the same set of wires in a single Ethernet cable. It is contemplated that Inline Power will power such PDs as Internet Protocol (IP) telephones, surveillance cameras, switching and hub equipment for the telecommunications network, biomedical sensor equipment used for identification purposes, other biomedical equipment, radio frequency identification (RFID) card and tag readers, security card readers, various types of sensors and data acquisition equipment, fire and life-safety equipment in buildings, and the like. The power is direct current, 48 Volt power available at a range of power levels from roughly 0.5 watt to about 15.4 watts in accordance with the standard. There are mechanisms within the IEEE 802.3af standard to allocate a requested amount of power. Other proprietary schemes also exist to provide a finer and more sophisticated allocation of power than that provided by the IEEE 802.3af standard while still providing basic compliance with the standard. As the standard evolves, additional power may also become available. Conventional 8-conductor type RG-45 connectors (male or female, as appropriate) are typically used on both ends of all Ethernet connections. They are wired as defined in the IEEE 802.3af standard.

FIGS. 1A,1B and1C are electrical schematic diagrams of three different variants of PoE as contemplated by the IEEE 802.3af standard. InFIG. 1Aa data telecommunications network10acomprises a switch or hub12awith integral power sourcing equipment (PSE)14a. Power from the PSE14ais injected on the two data carrying Ethernet twisted pairs16aaand16abvia center-tapped transformers18aaand18ab. Non-data carrying Ethernet twisted pairs16acand16adare unused in this variant. The power from data carrying Ethernet twisted pairs16aaand16abis conducted from center-tapped transformers20aaand20abto powered device (PD)22afor use thereby as shown. InFIG. 1Ba data telecommunications network10bcomprises a switch or hub12bwith integral power sourcing equipment (PSE)14b. Power from the PSE14bis injected on the two non-data carrying Ethernet twisted pairs16bcand16bd. Data carrying Ethernet twisted pairs16baand16bbare unused in this variant for power transfer. The power from non-data carrying Ethernet twisted pairs16bcand16bdis conducted to powered device (PD)22bfor use thereby as shown. InFIG. 1Ca data telecommunications network10ccomprises a switch or hub12cwithout integral power sourcing equipment (PSE). Midspan power insertion equipment24simply passes the data signals on the two data carrying Ethernet twisted pairs16ca-1and16cb-1to corresponding data carrying Ethernet twisted pairs16ca-2and16cb-2. Power from the PSE14clocated in the midspan power insertion equipment24is injected on the two non-data carrying Ethernet twisted pairs16cc-2and16cd-2as shown. The power from non-data carrying Ethernet twisted pairs16cc-2and16cd-2is conducted to powered device (PD)22cfor use thereby as shown. Note that powered end stations26a,26band26care all the same so that they can achieve compatibility with each of the variants described above.

Turning now toFIGS. 1D and 1E, electrical schematic diagrams illustrate variants of the IEEE 802.3af standard in which 1000 BaseT communication is enabled over a four pair Ethernet cable. Inline Power may be supplied over two pair or four pair. InFIG. 1Dthe PD accepts power from a pair of diode bridge circuits such as full wave diode bridge rectifier type circuits well known to those of ordinary skill in the art. Power may come from either one or both of the diode bridge circuits, depending upon whether Inline Power is delivered over Pair 1-2, Pair 3-4 or Pair 1-2+Pair 3-4. In the circuit shown inFIG. 1Ea PD associated with Pair 1-2 is powered by Inline Power over Pair 1-2 and a PD associated with Pair 3-4 is similarly powered. The approach used will depend upon the PD to be powered.

Inline Power is also available through techniques that are non-IEEE 802.3 standard compliant as is well known to those of ordinary skill in the art.

In order to provide regular Inline Power to a PD from a PSE it is a general requirement that two processes first be accomplished. First, a “discovery” process must be accomplished to verify that the candidate PD is, in fact, adapted to receive Inline Power. Second, a “classification” process must be accomplished to determine an amount of Inline Power to allocate to the PD, the PSE having a finite amount of Inline Power resources available for allocation to coupled PDs.

The discovery process looks for an “identity network” at the PD. The identity network is one or more electrical components which respond in certain predetermined ways when probed by a signal from the PSE. One of the simplest identity networks is a resistor coupled across the two pairs of common mode power/data conductors. The IEEE 802.3af standard calls for a 25,000 ohm resistor to be presented for discovery by the PD. The resistor may be present at all times or it may be switched into the circuit during the discovery process in response to discovery signals from the PSE.

The PSE applies some Inline Power (not “regular” Inline Power, i.e., reduced voltage and limited current) as the discovery signal to measure resistance across the two pairs of conductors to determine if the 25,000 ohm resistance is present. This is typically implemented as a first voltage for a first period of time and a second voltage for a second period of time, both voltages exceeding a maximum idle voltage (0-5 VDC in accordance with the IEEE 802.3af standard) which may be present on the pair of conductors during an “idle” time while regular Inline Power is not provided. The discovery signals do not enter a classification voltage range (typically about 15-20V in accordance with the IEEE 802.3af standard) but have a voltage between that range and the idle voltage range. The return currents responsive to application of the discovery signals are measured and a resistance across the two pairs of conductors is calculated. If that resistance is the identity network resistance, then the classification process may commence, otherwise the system returns to an idle condition.

In accordance with the IEEE 802.3af standard, the classification process involves applying a voltage in a classification range to the PD. The PD may use a current source to send a predetermined classification current signal back to the PSE. This classification current signal corresponds to the “class” of the PD. In the IEEE 802.3af standard as presently constituted, the classes are as set forth in Table I:

TABLE IPSE ClassificationCorrespondingClassCurrent Range (mA)Inline Power Level (W)00–515.418–134.0216–217.0325–3115.4435–4515.4

The discovery process is therefore used in order to avoid providing Inline Power (at full voltage of −48 VDC) to so-called “legacy” devices which are not particularly adapted to receive or utilize Inline Power.

The classification process is therefore used in order to manage Inline Power resources so that available power resources can be efficiently allocated and utilized.

In many cases where PDs are used, it may be desirable to provide some redundancy in terms of data and/or power delivery for cases in which equipment (hubs, switches, cable and the like) providing the power and/or data fails to continue to do so.

DETAILED DESCRIPTION

Embodiments of the present invention described in the following detailed description are directed at power and data redundancy in a single wiring closet. Those of ordinary skill in the art will realize that the detailed description is illustrative only and is not intended to restrict the scope of the claimed inventions in any way. Other embodiments of the present invention, beyond those embodiments described in the detailed description, will readily suggest themselves to those of ordinary skill in the art having the benefit of this disclosure. Reference will now be made in detail to implementations of the present invention as illustrated in the accompanying drawings. Where appropriate, the same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or similar parts.

Turning now toFIG. 2a typical 2-pair Ethernet (10 Base T, 100 Base T and 1000BT if 4-pairs were used) connection is illustrated. Box100encompasses the Ethernet port as it might exist in a network device such as a switch, hub, router or like device. Within port100is a PHY or physical layer device102which includes transmit circuitry104and receive circuitry106. The transmit circuitry104interfaces to a connector such as an RJ-45 connector (not shown here) and through the connector to a cable108which includes at least two pairs of conductors, the Pair 1-2 (110) and the Pair 3-6 (112). The interface between the transmit circuitry104and the cable108includes a center-tapped magnetic device such as transformer T1. T1has a PHY-side including pins1and2and center tap6, and a wire side including pins3and5and center tap4. The PHY side is also referred to as the primary side; the wire side is also referred to as the secondary side of the magnetic device T1. Termination circuitry114provides a Vdd bias (here illustrated as +3.3 VDC) to the primary of T1. The secondary of T1is coupled to cable pair112which is, in turn, coupled in operation to a network device118which may be another hub, switch or router or a PD such as a Voice Over Internet Protocol (VOIP) telephone or other network device.

The interface between the receive circuitry106and the cable108includes a center-tapped magnetic device such as transformer T2. T2has a PHY-side including pins1and2and center tap6, and a wire side including pins3and5and center tap4. The PHY side is also referred to as the primary side; the wire side is also referred to as the secondary side of the magnetic device Tb2. Termination circuitry116provides a ground bias to the primary of T2. The secondary of T2is coupled to cable pair110which is, in turn, coupled in operation to a network device118. If the pairs of conductors shown belonged to a 1000 Base T wired data telecommunications network segment then each pair would transmit and receive at the same time and all four pairs in the cable would be used.

Center tap pins4of T1and T2are coupled to inline power circuitry including a 48 VDC power supply120for providing Inline Power over cable108, control circuitry122and switch circuitry124.

FIG. 3is a block diagram of a system300in which redundancy of data and/or power is provided to a PD. In the system300it is desired to provide the protected device340with redundancy in both power and/or data from a pair of devices labeled Device1(310) and Device2(320) which serve as relay uplink sources of data and/or power for the protected device340. As used herein, the protected device may be referred to also as a powered device (PD) as defined in IEEE 802.3af. Because the PD is being redundantly protected with either or both of power and/or data, the device being hosted by the disclosed system will be referred to herein as a protected device.

It is contemplated that the relay uplinks may comprise an Ethernet switch such as a line card or other wiring closet switch device configured in accordance with the teachings of this disclosure. It is to be understood that devices1and2may comprise any device from which Ethernet data and/or power may be obtained. The devices are coupled to a redundancy device330through respective Ethernet cable links313and323. To execute various embodiments of this disclosure, the switches310and320may include a microprocessor311and321, and associated memory312and322, respectively. While two such devices are shown inFIG. 3, it is to be understood that any number of switches may be employed in the present disclosure.

FIG. 3also includes a protected device330representing a host device to which it is desired to provide power and/or data. It is contemplated that the protected device may comprise any device that will accept power and/or data over the physical Ethernet link333, such as a VoIP telephone or Ethernet switch.

FIG. 3includes a redundancy device330provided to couple the protected device340to the relay uplink devices310and320through an Ethernet link333. As will be more fully described below, the redundancy device330is configured to accept one of the devices as the active device, and pass data and/or power from the active device to the protected device. Other relay uplinks are held in an inactive state. The relay uplink devices are configured to communicate with each other through the redundancy device and monitor each other's status, and detect when there is a failure. When a failure is detected, the inactive device will send a switchover command to the redundancy device, thereby becoming the active device and transparently provide a redundant source for data and/or power to the protected device.

The redundancy device thereby functions as a three-port relay configured to provide a fail-safe backup source by accepting power and/or data from at least two relay uplinks through Ethernet physical cables, and seamlessly switch between the two uplinks when a failure is detected. The redundancy device of this disclosure is also configured to enable the relay uplinks of the disclosure to communicate with each other and establish a redundant system. Methods for providing redundancy will now be disclosed.

FIG. 4Ais a flow diagram of a method for providing redundancy of power and/or data to a protected device in accordance with the teachings of this disclosure. In act410, the redundancy device then establishes one of the uplinks as the active state uplink, and passes data and/or power from active uplink to the protected device. The balance of the relay uplinks may be maintained in a redundant inactive state.

In a preferred embodiment, relay uplinks may be provided in redundant pairs, with a particular port of the redundancy device port pairs designated as the default active uplink, and the other port of the pair as the redundant port. It is to be understood that any number of relay uplinks may be employed.

In query420, the active relay uplink is monitored to detect a failure in either power and/or data. If a failure is detected, then in act430a switchover process is activated whereby the failed active relay uplink is taken off-line, and a redundant relay uplink is replaced as the active relay uplink, thereby supplying the PD with a redundant source of power and/or data.

As will be appreciated, a potential dual source of power exists from each of310and320and may be delivered to a PD at all times over each set of pairs in the twisted pair cable creating two sources of input power at340each from a different devices/sources relieving the need to worry about dual sources of power or power redundancy.

FIG. 4Bis a flow diagram of a further method for providing redundancy of power and/or data to a protected device in accordance with the teachings of this disclosure. InFIG. 4B, the process begins in act510, where one of the uplink relays is established as the active uplink, and data and/or power is provided to a PD through the redundancy device.

In query520, the inactive redundant device determines whether its' link to the redundancy device is up and functioning. If it is determined that its link is down, the process ends.

If it is determined that its link is up, then the process moves to query530, where it is determined whether the link associated with the active uplink relay is up and functional. If a failure is found in the active uplink, the process moves to act540, where a switchover command is issued to the redundancy device, and power and/or data is supplied from the device that issued the switchover command.

While the process inFIG. 4Bis shown as being sequential, it is to be understood that the actions performed in queries520and530may be performed in a parallel fashion as will be explained below.

As will be more fully described below, the relay uplinks that are maintained in an inactive state are configured to detect a failure of the active relay uplink, and indicate to the redundancy device that a switchover is needed. The redundancy device monitors communications from the inactive device to detect a switchover command. Responsive to a switchover communication from a redundant uplink, the redundancy device will establish the redundant uplink from which the switchover command was received as the new active uplink, and begin passing data and/or power from newly established active uplink to the protected device.

FIG. 5is a conceptual block diagram of a redundancy device500configured in accordance with the teachings of this disclosure.

The redundancy device500includes a data switch505configured as will be more fully disclosed below. Data and/or power is received from uplink relays via Ethernet connectors515and520. The received signals on connector515are coupled to switch505through twisted pairs506and507and may be interfaced through termination circuitry modules516and517that may include conventional circuitry as discussed above. Likewise, signals received on connector520are coupled to switch505through twisted pairs508and509which may be interfaced through circuitry521and522. Inline power may also be provided to through power sources519and524.

In operation, connector515is coupled to a first source of data and/or power, and connector520is connected to a second such source. Typically, the sources are upstream uplink relays as described above. The data switch505includes switching circuitry511coupled to twisted pairs506and508, and is configured to direct the data and/or power on either twisted pairs506and508onto twisted pair541. Likewise, switching circuitry512is coupled to twisted pairs507and509, and is configured to present the power and/or data on twisted pairs507and509onto twisted pair542. It is contemplated that switching circuitry511and512may be under the control of control circuitry513. The data switch and associated control circuitry may be embodied as system of relays, as an integrated circuit such as an ASIC as is known in the art, or as a microprocessor-based system.

Differential pairs541and542are in turn coupled to connector540through termination circuitry518and523, respectively. Inline power is supplied to differential pairs541and542through power source543. Connector540is coupled to the protected device via an external twisted pair cable such as CAT 3, CAT 5 and the like; connectors515,520and540may be RJ45 connectors or similar.

It is contemplated that the redundancy device and uplink relays may be configured to communicate with each other to effect the redundancy functionality of this disclosure. In one embodiment, packet-based communication is utilized to effect the data and/or power redundancy in accordance with the teachings of this disclosure. The packets may be generated by the relay uplinks and are decoded by the redundancy device. Packets are provided that are configured to indicate to the relay which relay uplink is the active uplink, and when to switchover to a redundant source.

In one preferred embodiment, the various components of the redundant system may be configured to communicate using a protocol known as Bi-Directional Forwarding Direction, referred to herein as BFD.

BFD is a simple hello protocol that in many respects is similar to the detection components of well-known routing protocols in the art. A pair of systems, such as the redundant pair of uplinks of this disclosure, transmit BFD packets periodically over each path between the two systems, and if a system stops receiving BFD packets for long enough, some component in that particular bidirectional path to the neighboring system is assumed to have failed. Though the following embodiment utilizes the BFD protocol, it is to be understood that any similar hello protocol may be utilized in the present invention.

For example, the present disclosure may also utilize y.17oam that is currently being defined by the ITU-T. Also, IEEE 802.1ag (also being defined) may be utilized. Both of these are Ethernet OAM standards currently in progress, and may be employed as hello protocols herein.

A path is only declared to be operational when two-way communication has been established between systems. A separate BFD session is created for each communications path and data protocol in use between two systems. Each system estimates how quickly it can send and receive BFD packets in order to come to an agreement with its neighbor about how rapidly detection of failure will take place. These estimates can be modified in real time in order to adapt to unusual situations. This design also allows for fast systems on a shared medium with a slow system to be able to more rapidly detect failures between the fast systems while allowing the slow system to participate to the best of its ability.

BFD Control packets are sent in an encapsulation appropriate to the environment, such as within the Ethernet environment of this disclosure. BFD has two operating modes which may be selected, as well as an additional function that can be used in combination with the two modes. The primary mode is known as Asynchronous mode. In this mode, the systems periodically send BFD Control packets to one another, and if a number of those packets in a row are not received by the other system, the session is declared to be down.

The second mode is known as Demand mode. In this mode, it is assumed that each system has an independent way of verifying that it has connectivity to the other system, so once a BFD session is established, the systems stop sending BFD Control packets, except when either system feels the need to verify connectivity explicitly, in which case a short sequence of BFD Control packets is sent, and then the protocol quiesces.

An adjunct to both modes is the Echo function. When the Echo function is active, a stream of BFD Echo packets is transmitted in such a way as to have the other system loop them back through its forwarding path. If a number of packets in a row of the echoed data stream are not received, the session is declared to be down. The Echo function may be used with either Asynchronous or Demand modes.

The payload of a BFD Echo packet is considered to be a local matter, since only the sending system ever processes the content. The only requirement is that sufficient information is included to demultiplex the received packet to the correct BFD session after it is looped back to the sender.

In addition to the BFD protocol, it is contemplated that the connectivity check packets may include information enabling the redundancy device to operate in accordance with this disclosure. In one embodiment, the packets are modified by the sending device to indicate three operations to the redundancy device.

To accomplish this special packet communication, it is contemplated that the packets may be modified by the relay uplinks by replacing the destination MAC address with one of three special MAC addresses. As is known by those of ordinary skill in the art, typically certain address ranges are reserved, such as multicast addresses.

These addresses may be hardcoded in a lookup table in the redundancy device. It is contemplated that the table may contain instructions regarding a specified operation to be performed corresponding to an address contained in the destination address of a received packets. The switching and control circuitry of the redundancy device may be configured to perform a lookup operation and execute a fetched operation corresponding with a decoded address in the table. Thus, responsive to the received MAC address, the redundancy device may route packets between devices, or switch data and/or traffic flow between the active device and redundancy device in the event of a failure.

In one preferred embodiment, three special addresses are provided corresponding to three desired operations. A first address indicates to the redundancy device that the packet is a loopback packet. This packet indicates to the redundancy device that this packet should be echoed back out the uplink on which it was received. This packet may be utilized by the uplink to check the integrity of its' link to the redundancy device.

A second address represents a connectivity check packet that indicates to the redundancy device to re-transmit the packet out to a different uplink, i.e., out an uplink on which the packet didn't arrive such as to the redundant pair device.

The BFD protocol described above may be employed to determine if there is a failure on the link. Hence, a failure to receive a certain amount of connectivity check packets in a given time may indicate to the sender that the device path associated with the redundant pair device has failed.

If a failure has been detected, then the relay uplink may send a packet having a third address embedded therein as a switchover packet to the redundancy device. The switchover packet indicates to the redundancy device to switch over passing data and/or power to the uplink on which the switchover packet was received to the PD. After performing a switchover, the switchover packet may be retransmitted out the uplink on which was received to indicate to the sender that the switchover packet was received and processed.

The speed of the switchover process is dependent on the speed of the loopback and switchover packet transmission process. As mentioned above, system using BFD may estimate roundtrip path times to establish how quickly failures will be declared. Hence, it is contemplated that by employing redundancy devices near wiring closets, the failure detection and switchover process of this disclosure may be accomplished in a manner fast enough so as to be transparent to the protected device.

FIGS. 6A-6Gare block diagrams of a redundancy system operating in accordance with the teachings of this disclosure, illustrating the packet-based failure detection and switchover process.FIGS. 6A-6Gshow two devices, labeled devices1and2, coupled to a redundancy device. A protected device is coupled to the redundancy device.FIGS. 6A-6Gshow the simplest implementation whereby a redundant pair of devices is provided to effect the redundancy benefits of this disclosure.

FIG. 6Ashows the system at startup. As mentioned above, it is contemplated that at startup, a port may be designated to corresponding to the default active device.

Alternatively, it is contemplated that a discovery protocol may be employed to establish an active device. For example, at startup, each device may advertise their redundant capabilities through a discovery protocol such as the Cisco Discovery Protocol (CDP) provided by the assignee of the present disclosure, though any similar protocol may be employed.

FIG. 6Ashows an active path605and a redundant path610being established as a result of the startup process, andFIG. 6Bshows data and/or power615flowing between the active Device1and the protected device.

FIG. 6Cshows Device2sending a loopback packet620to the redundancy device. As mentioned above, this packet may have an indication embedded therein that indicates to the redundancy device to send the packet back out the uplink on which it was received.FIG. 6Ctherefore shows the redundancy device as returning the packet as loopback packet625to Device2.

FIG. 6Dshows Device2sending a connectivity check packet630to the redundancy device. As mentioned above, this packet may have an indication embedded therein that indicates to the redundancy device to send the packet back out the other uplink, i.e., the uplink other than from which it was received. In a system where a pair of redundancy devices are provided as illustrated inFIGS. 6A-6G, the connectivity check packet indicates to the redundancy device to transmit the packet to the redundant device partner, i.e., to the other device pair. Accordingly,FIG. 6Dshows the redundancy device sending connectivity check packet635being forwarded to Device1.

FIG. 6Eshows a connectivity check packet being generated by Device1as packet640in accordance with the BFD process described above. The redundancy device then forwards the packet on to Device2as packet645.

As mentioned above, the disclosed connectivity check packets may be generated in a periodic fashion as determined by the BFD protocol. Hence, in a typical steady state scenario, each of the redundant pair of devices will periodically send out both loopback packets and connectivity check packets, wherein the loopback packets contain an indication for the redundancy device to echo the packet back to the sender, and wherein the connectivity check packet contains an indication for the redundancy device to transmit the packet to the other device of the redundant pair.

In accordance with the BFD protocol, each of the devices expects to receive a certain number of connectivity check packets from the other device in a pre-defined time period, in addition to receiving its own loopback packets. Using these packets, the inactive device may detect a failure in the active device.

A failure requiring a switchover may be detected by 1) first verifying that its own link to the redundancy device is operative, and then 2) determining that the other device or device's link has failed.

To determine the first condition, the device need only receive its own loopback packets back from the redundancy device to verify that its link is operational. To establish the second condition, the device may detect a failure of the other paired device by failing to receive a certain number of connectivity check packets in a row.

In operation as a redundant pair, it is contemplated that the switchover condition may be detected when the inactive switch (Device2) can verify that its link to the redundancy device is operational, and it fails to receive a prescribed number of connectivity check packets from the active relay switch (Device1) in a given time.

Moving toFIG. 6F, if a failure is detected by Device2, then a switchover packet650may be sent by Device2to the redundancy device as shown inFIG. 6F. The redundancy device may then route power and/or data655from Device2to the protected device that is shown inFIG. 6G.

As can now be seen, the redundancy device of this disclosure provides a simple, inexpensive, and reliable device that allows the relay uplinks to retain control while still providing an intelligent failure detection and healing process. Furthermore, the redundancy device is inline-powered, and does not require the end user to install any extra cabling.

Referring now toFIGS. 7A and 7B, diagrams are presented that show the redundancy device, noted as a “Y” switch inFIGS. 7A and 7B, may disposed in locations other than those shown above. For example,FIG. 7Ashows the Y device being disposed within the PD itself. Hence, a PD may have a redundancy device installed as standard or optional equipment.

Alternatively,FIG. 7Bshows the redundancy device being disposed in a relay uplink. In this case, the redundant relay uplink (Device2) may be coupled to the relay uplink that includes the redundancy device (Device1). In this configuration, only one cable is required between a protected device and the wiring closet were the relay uplinks may be installed.

FIG. 8is a conceptual block diagram of a redundant system800further configured to provided multiple redundancy paths. The system800includes the structure ofFIG. 5, with the addition of a pair of redundant data switches505, and a redundant pair of power sources544. By providing a pair of data switches and power sources, it will be appreciated that no single point of failure exists in the system ofFIG. 8.

The data switches505ofFIG. 8may comprise dual integrated circuits that are powered by a power supply that generates local power from two redundant inline power sources coming from the cables connecting the upstream relay uplinks. To power the Y-selector devices, the circuitry for power generation (power sources544) is in itself redundant as to allow the data switch and all the local power needs to be met if either cable1or cable2is unplugged or any power failure were to occur within the Y-selector module. It is contemplated that a possible 3rd source of power may be provided, such as a local auxiliary main power. Also a wireless transceiver, such as an 802.11 wireless transceiver (not shown), may exist on the data switch providing a 3rdmeans of communication with both310and320and may comprise a part of the data switch.

The redundant data switches505ofFIG. 8may comprise a wide variety of switching circuitry known in the art, such as signal FETs, i.e., NMOS or PMOS devices, or may comprise diodes and current sources. Alternatively, the data switches may comprise low capacitance mechanical relays configured as is known in the art to route signals from each chip to the passive magnetics in accordance with the teachings of this disclosure.

To switch between the individual data switches and the differential pairs, relay control circuitry530may be included and coupled to the data switches505through communication paths531. In the event of a failure of one of the data switches, it is contemplated that the failed transmit circuitry may be shut down, thereby placing the failed unit in a state of high impedance and preventing any undesirable loading. It should be noted that as the relay circuitry typically comprises high impedance devices, serious loading should not be a problem if any of the relay circuitry faults. It is also contemplated that the relay control circuitry may be configured to remove power from the active data switch as a last resort, thereby keeping the device operational should a hard failure occur, allowing the second redundant data switch to take over

FIG. 9is conceptual block diagram of a 4-pair redundant system900in accordance with the teachings of this disclosure. The system900includes two redundant systems901and902. It is contemplated that each of the systems901and902may be configured in accordance withFIG. 8as disclosed above. However, the diagrams ofFIG. 9have been simplified for the sake of discussion.

FIG. 9shows system901as including a pair of differential pairs coupled between connector910and a first data switch, and a pair of differential pairs coupled between connector915and a second data switch. Relay circuitry is provided to interface with the data switches and select one of the sources to couple to a powered device through connector920. Likewise, system902includes a pair of differential pairs coupled between connector925and a first data switch, and a pair of differential (FYI TIM, twisted pairs are in cables these would be traces on the board) pairs coupled between connector930and a second data switch. Relay circuitry interfaces one of the sources to a powered device through connector935.

It will be appreciated that the 4-pair configuration ofFIG. 9may be used in 10/100/1000 Ethernet, and for 10/100 configurations this results in 4-pairs for each device. It is contemplated that 4 data switches may be employed, thereby providing double-redundancy for the powered device. In the case of 1000BaseT,920and935would be a single RJ45 that is connected to the protected device via a cable.910,915and925,930would also be single RJ45 connector since 1000BaseT requires four-pairs to communicate.

FIG. 10is conceptual block diagram of another embodiment of a 4-pair redundant system1000in accordance with the teachings of this disclosure. System1000include a redundant system901as disclosed above, and also includes a passive system903. Again,901and903may comprise a single RJ45.

To provide additional passive redundancy in an 10/100 Ethernet system, one of the unused pairs presented on connector930may be coupled directly to the PD through connector935in system903. It is contemplated that the twisted pairs may be coupled electrically in parallel with the twisted pairs coupled through system901and switched in using switching circuitry known in the art. Alternatively, the passive pairs may be made available to the PD through a different port.

As will be appreciated, only one of the relay uplinks (coupled on either pins1,2,3,6; or4,5,7,8) may be passively coupled to the PD. However, such a direct connection provides a passive failsafe path to at least one of the relay uplinks in the event of a total failure of the redundancy device.

FIG. 11is a conceptual block diagram of another embodiment of a 4-pair redundant system1100in accordance with the teachings of this disclosure. In this embodiment, the system904provides for the passive switching of one of the twisted pairs presented on connectors930and940to connector935using control means945. Methods and apparatus for accomplishing such switching may be found in co-pending application Ser. No. 11/022,288, filed Dec. 23, 2004 and assigned to assignor of this application, and is incorporated herein as though set forth fully. Using passive techniques, a selected one of the twisted pairs from a relay uplink may be directly coupled to the PD, thereby providing yet another redundant source of power and/or data to the PD.

As can now be seen, the redundancy device of this disclosure provides a simple, inexpensive, and reliable device that allows the relay uplinks to retain control while still providing an intelligent failure detection and healing process. Furthermore, the redundancy device is inline-powered, and does not require the end user to install and extra cabling.

While embodiments and applications of this invention have been shown and described, it will now be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts disclosed herein. Therefore, the appended claims are intended to encompass within their scope all such modifications as are within the true spirit and scope of this invention.