Abstract:
A method and system for providing component status of a local or receiving component to a distributed component in a communication network is provided. The design determines defect status for the local or receiving component and cross connects the defect status for the local component to at least one distributed component separate from the local or receiving component, typically using a unified cross connect design. The design also alters a connection matrix maintained within each distributed component to indicate defect status for a transmit channel between the local component and the remote component. Remote defect indications may be determined within the design and provided to the remote components.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to the field of high-speed data transfer, and more specifically to managing remote status indications within a data transfer architecture.  
         [0003]     2. Description of the Related Art  
         [0004]     Current high-speed high bandwidth data communication systems employ a variety of components to facilitate the receipt and transmission of data packets. Among the components used are network nodes, which may include functional components such as framers and cross-connects between components that allow data transport over at least one channel. A framer is a device that handles the overhead processing and statistics for the SONET/SDH connection and provides a method of distinguishing digital channels multiplexed together. The framer designates or marks channels within a bit stream, providing the basic time slot structure, management, and fault isolation for the network node. The cross connect allows portions of a digital bit stream to be rerouted or connected to different bit streams. Cross connects enable data traffic to be moved from one SONET ring to the next ring in its path to the destination node.  
         [0005]     Typically, these high-speed high bandwidth data communication systems are realized by interconnecting a large number of network nodes to receive and transmit ever-increasing amounts of data. The status of the various components in the network, including the network nodes, is typically maintained and may be provided to particular components under different circumstances. The network may provide remote status indicators to inform a remote component of a local component&#39;s status.  
         [0006]     The problem with providing remote status indication in a distributed system employing an asymmetric connection is that status is generally inefficiently transmitted from the local device to the remote device. Inefficiencies may include the need for added device interfaces or board traces to receive or transmit the status indicators, difficulty in synchronizing the cross connect from the receiving channel to the transmitting channel with the cross connect for the data at the transmitting device, and separation of cascaded connection matrices for multiple layers. In short, many ways exist for the remote status indication to fail to reach the remote device, or for the indication to reach the remote device in an imperfect form or manner.  
         [0007]     A design that provides for and efficiently transmits remote status indications may provide increased throughput and other advantageous qualities over previously known designs, including designs employing the SONET/SDH architecture.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which:  
         [0009]      FIG. 1A  is a conceptual illustration of a SONET/SDH communications switching system employing the design provided herein;  
         [0010]      FIG. 1B  shows a suitable system embodiment in accordance with an embodiment of the present invention;  
         [0011]      FIG. 2  illustrates the general traffic flow and forwarding mechanism configuration within a single component or device;  
         [0012]      FIG. 3  shows remote status forwarding operation in cascaded connection matrices in a SONET/SDH environment; and  
         [0013]      FIG. 4  illustrates remote status forwarding using a unified cascaded connection matrix.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Reference will now be made in detail to the preferred embodiments of the design, examples of which are illustrated in the accompanying drawings and tables. While the design will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the design to those embodiments. On the contrary, the design is intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the design as defined by the appended claims.  
         [0015]     The present design may offer an architecture and methodology for providing remote indicators to remote entities. The design may include determining the receive defect status, where the receive defect status is the status of the receiving or local device. The design may further transport this receive defect status to multiple elements in the distributed system, typically using a fabric, such as a unified high order (HO) and low order (LO) fabric. The design may further establish and employ a connection matrix within multiple network elements to move the defect status to the appropriate corresponding transmit channels. The connection matrix is a matrix containing a listing of all connections to components. If, for example, component X is connected to component Y, and X can transmit and Y can receive, the connection matrix at the intersection of “X transmit” and “Y receive” may include a “True” or “1” or other appropriate indication. Finally, the present design may generate and transmit remote status indicators using the arrangement so established.  
         [0016]     In a SONET/SDH architecture, several levels of multiplexing hierarchy use these remote indicators, including Multiplex Section (Line), High Order Path (STS Path), High Order Tandem Connection, Low Order Path (VT Path), and Low Order Tandem Connection. As discussed herein, the High Order Path remote status indicators HP-RDI and HP-REI carried on the G 1  High Order Path Overhead byte are discussed, while it is understood that other applicable remote indicators, including those not conforming to SONET/SDH, may be employed.  
         [0017]     Data transmission over fiber optics networks may conform to the SONET and/or SDH standards. SONET and SDH are a set of related standards for synchronous data transmission over fiber optic networks. SONET is short for Synchronous Optical NETwork and SDH is an acronym for Synchronous Digital Hierarchy. SONET is the United States version of the standard published by the American National Standards Institute (ANSI). SDH is the international version of the standard published by the International Telecommunications Union (ITU). As used herein, the SONET/SDH concepts are more fully detailed in various ANSI and ITU standards, including but not limited to the discussion of “health”, Bellcore GR-253, ANSI T1.105, ITU G.707, G.751, G.783, and G.804.  
         [0018]     System Design  
         [0019]     A typical SONET/SDH switching system  100  is shown in  FIG. 1A . In the SONET/SDH switching system  100 , a transmitter  110  is connected through a communication pathway  115  to a switching network  120 . Switching network  120  is connected through a communication pathway  125  to a destination  130 . The transmitter  110  sends data as a series of payloads/frames to the destination  130  through the switching network  120 . In the switching network  120 , packets typically pass through a series of hardware and/or software components, such as servers. As each payload arrives at a hardware and/or software component, the component may store the payload briefly before transmitting the payload to the next component. The payloads proceed individually through the network until they arrive at the destination  130 . The destination  130  may contain one or more processing chips  135  and/or one or more memory chips  140 .  
         [0020]      FIG. 1B  is a drawing of a typical SONET/SDH Add-Drop Multiplex (ADM)  150 . The ADM  150  manages SONET/SDH network topologies, the most typical topology being a ring. In a ring topology, the ADM  150  connects to the ring using two linecards: a first (ring) linecard  151  connected to the West Interface and a second (ADD/DROP) linecard  152  connected to the East Interface. Other linecards can be used as traffic sources and sinks (not shown), where a source may be involved in an ADD operation, and a sink may be involved in a DROP operation. An ADD operation inserts traffic from the source onto the ring, and a DROP operation removes traffic off the ring to the sink.  
         [0021]     Each ring linecard, such as first linecard  151 , may include a framer  155 , pointer processor  156 , and a timeslot interchange (TSI)  157 . The framer  155  can be used to locate the beginning of a SONET/SDH frame. The pointer processor  156  may locate the payload and align the payload for the TSI and fabric  160 . The TSI  157  may move or groom timeslots within an SONET/SDH frame to provide orderly traffic to the fabric card  161 .  
         [0022]     Different types of ADD/DROP linecards exist. Some ADD/DROP linecards may handle Ethernet packets, Plesiosynchronous digital hierarchy (PDH) traffic (T1, T3, E1, E3, etc), and/or transit traffic from other SONET/SDH rings. Other types of ADD/DROP linecards may include transit ADD/DROP linecards, similar to the RING linecards. A PDH linecard may contain a T1/E1 framer that searches for the beginning of T1/E1 frame, a performance monitoring function for tracking the status of the incoming frame, and a mapper to insert the PDH traffic into a SONET/SDH frame, thus making the PDH traffic understandable to the fabric  160 . PDH ADD/DROP linecard  175  includes PDH framer  176 , PDH Monitor  177 , and mapper  178 .  
         [0023]     Fabric management card  161  contains management host controller  162  and high order cross connect or TDM fabric  163 , and may interface with subtended fabric  164  containing low-order cross-connect  165 . The subtended fabric  164  may fit in one or more line card slots. Fabric backplane  171  may be TFI-5 or proprietary, for example. Control plane  172  may be PCI compatible or a simple microcontroller interface depending on the application. Other configurations may be employed for the backplane and control plane elements.  
         [0024]     The transmission path of the ADM  150  comprises a time division multiplexing (TDM) fabric or cross-connect  160  that moves traffic among all the linecards attached to the fabric  160 . A high-order cross-connect or fabric moves high-order SONET/SDH containers between linecards and amongst time-slots within a SONET/SDH framer. A full function ADM  150  can manipulate low-order as well as high-order SONET/SDH containers. The low-order manipulation can be performed in a subtended low-order cross-connect. Use of multiple fabrics may create issues that could be resolved by providing a single, unified fabric as is done in the current design.  
         [0025]     Remote Status Indicator Design  
         [0026]     A transport network node has multiple receive and transmit ports by which the transport network and access networks are connected. These nodes typically have large aggregate bandwidths, receiving and transmitting significant quantities of data per unit of time, and use multiple ports to transmit and receive this data. Nodes may be implemented using multiple framer processors, and such a system is considered “distributed” from the node&#39;s point of view. The connection between the receive and transmit ports and the remote system or device may require more than a single framer device. Use of such a multiple framer device to connect to a remote system is called an asymmetric connection. The need for asymmetric connections may arise from the desired implementation of the nodes and/or the type of protection switching employed, where protection switching may provide for switching to an alternate component or resource in the event of a failure.  
         [0027]     One aspect of an implementation of a remote status mechanism is illustrated in  FIGS. 2-4 . The design may include determining the receive defect status, transporting the receive defect status to multiple elements in the distributed system or, in some circumstances, to all elements of the distributed system, providing a connection matrix within each element to move the defect status to appropriate or applicable corresponding transmit channels, and generating and transmitting remote status indicators.  
         [0028]     In operation, the receiving device detects the receive defect condition. The receiving device inserts the receive defect condition into any unused data slots in the output data stream connected to each element of the distributed system. The transmitting device may extract the condition or status, and the condition or status may be provided by cross connect to appropriate transmitting channels. The status may be employed to generate remote status indicators for the far-end or remote system. Generation of the remote status indicator may be performed at the receiving device, before transporting across devices, or at the transmitting device after submission to the cross connect.  
         [0029]      FIG. 2  illustrates the general traffic flow and forwarding mechanism configuration within a single device. As may be appreciated, multiple devices may be interconnected to provide extended capabilities, with the ability to provide information between devices using a cross connect. The features of  FIG. 2  are included within a single framer device. The top path represents the receive data stream or traffic flow, while the bottom path represents the transmit data stream or traffic flow. In a SONET/SDH configuration, the data stream may include all overhead and pointer processing data. Element  201  is a G 1  generator, where G 1  represents a byte within overhead of the transmitted data in a SONET/SDH configuration. G 1  generator  201  receives the status extracted from the receive traffic flow, generates a G 1  value, and inserts the G 1  information into the unused overhead of the data stream. The data including the G 1  information then passes to cross connect  202 , which represents an interconnection of the data stream among all elements of the distributed system. In the transmit traffic flow path, G 1  information is extracted at the point shown, and the G 1  information provided to the G 1  cross connect  203 . Optional protection controller  204  may be included to monitor the availability of G 1  information, and if no G 1  information is present, the G 1  cross connect  203  may not operate to insert G 1  data into the transmit stream. Without optional protection controller  204 , the G 1  cross connect  203  will continuously extract and insert G 1  data in all circumstances.  
         [0030]      FIG. 3  illustrates G 1  remote status forwarding in cascaded connection matrices. The present design uses separate high order (HO) cross connect matrix  301  and low order (LO) cross connect matrix  302  to process and pass data. From  FIG. 3 , HO cross connect matrix  301  is connected to LO cross connect matrix  302  by a high order path termination and adaptation connections. Each triangle such as that shown as element  303  represents a termination point, which terminates the overhead and the container transmitted. The trapezoidal elements, such as element  304 , are adaptation elements that adapt and pass the payload portion of the message. Adaptation comprises pointer determination and/or pointer generation in this context. The combination element, such as element  305 , represents both the termination and the adaptation of the message received.  
         [0031]     From  FIG. 3 , data may flow from LO cross connect matrix  302  to HO cross connect matrix  301  through adaptation element  304  and termination element  303 . Data may alternately flow from HO cross connect matrix  301  to LO cross connect matrix  302  through termination element  306  and adaptation element  307 . Both of these paths represent the high order path termination and adaptation functionality.  
         [0032]     The LO cross connect matrix interfaces with adaptation element  304  using arrangement  308 , which includes path  308   a , path  308   b , termination element  308   c , and path  308   d . Path  308   b , termination element  308   c , and path  308   d  provide for low order path non-intrusive monitoring, enabling monitoring of the content of the low order path and the data provided from HO cross connect matrix  301  to LO cross connect matrix  302 . Such monitoring enables evaluating the data flowing to the LO cross connect matrix  302 , and if acceptable, forwarding the data to the LO cross connect matrix  302 . If the data is all LO and no monitoring is needed, path  308   a  passes the data to the LO cross connect matrix  302 .  
         [0033]     Termination elements  304  and  306  interface by termination element  304  picking out HP-RDI/HP-REI, the high order path remote data indicator/remote error indicator, where the remote error indicator provides a count of bit errors. In SONET/SDH, G 1  includes the high order protocol/layer remote defect indicator, where D 5  includes the low order protocol/layer remote defect indicator.  
         [0034]     Features  310  and  311  include elements  310   a  and  310   b  as well as  311   a  and  311   b , respectively. The two paths represent two different incoming streams from the Management System (MS). Element  310   a  is a combination termination/adaptation component that terminates and adapts the MS data received. Element  310   b  is a termination component in a high order path non-intrusive monitor. Each path contains a high order path non-intrusive monitor, and each operates to detect a defective or bad message received. If such a defective message is located, operation switches to the other data path from the MS to the HO cross connect matrix  301 . Monitoring may be bypassed if undesired or unnecessary, or in the event pointers or the high order payload are unavailable. The lines numbered  350  and  351  represent incoming data from outside or remote sources (lines  350 ) and data outgoing to outside or remote sources.  
         [0035]     By way of definition, in the scenario presented, a distributed cross connect arrangement indicates multiple components are interconnected to form a relatively large capacity non-blocking cross connect. For a network comprising four devices, where each device has a non-blocking cross connect bidirectional capacity of 20 Gbps, the entire network becomes a single non-blocking cross connect with 80 Gbps bidirectional capacity.  
         [0036]     Non-blocking in this context means that any timeslot can be cross connected to any one or other timeslot without being blocked by connections of another timeslot to yet other timeslots. Timeslot A can be cross connected to timeslot B without being blocked by timeslot C being connected to timeslot D. Bidirectional capacity is a term indicating that capacity is summed, such that 10 Gbps counts for both output and input capacity. 80 Gbps means 80 Gbps of input and 80 Gbps of output. Interconnecting elements to form an equivalent but larger capacity element is termed “stacking.” 
         [0037]     Unifying the cascaded cross connect tends to minimize the number of physical interconnections and bandwidth required to stack cross connection elements. In the case of separate high order and low order cross connections, elements generally may require, in a SONET implementation for example, 80 Gbps of bidirectional bandwidth for each of the low order and high order cross connects for a total of 160 Gbps bidirectional. In the unified case, transmission and reception only requires 80 Gbps bidirectional.  
         [0038]     The present design may include a unified HO/LO cross connect fabric  401  as shown in  FIG. 4 . Use of the design of  FIG. 4  in a SONET/SDH environment can include broadcasting the G 1  high order data to meet high order UPSR (unidirectional path) requirements with low order grooming in a unified matrix. The unified HO/LO cross connect fabric may include a HP-RDI/HP-REI (G 1 ) cross connect fabric  450 , referred to here as a remote data indicator cross connect fabric  450 . The G 1  value received at this remote data indicator cross connect fabric  450  may be extracted from the incoming data stream and interpreted.  
         [0039]     The unified cross connect fabric  401  connects all distributed elements and specifically both the high order and low order aspects of each in a single fabric rather than two separate fabrics. Such a design allows for a single matrix to perform the interconnect functions of the cross connect fabric. Fabrication of a unified cross connect fabric comprises simply combining all performance of the HO and LO cross connect fabrics  301  and  302  from  FIG. 3  into a single unified cross connect fabric, addressing both high order and low order functionality.  
         [0040]     From  FIG. 4 , two paths are available to address unified HO/LO cross connect fabric  401 , namely an upper path and a lower path. The upper path includes combined element  402 , termination element  403 , adaptation element  404 , as well as adaptation element  405 , termination element  406 , and low order path non-intrusive monitor  407 . As with the previous design of  FIG. 3 , the low order path non-intrusive monitor monitors the low order path for and may remove unacceptable data. This low order path non-intrusive monitor  407  may be bypassed. The lower path offers similar components, namely combined element  412 , termination element  413 , adaptation element  414 , as well as adaptation element  415 , termination element  416 , and low order path non-intrusive monitor  417 . As contrasted with the design of  FIG. 3 , a single interconnection is provided with a single fabric to and from external distributed elements, and rather than processing a high order matrix and its functionality in addition to a low order matrix and its associated functionality, a single fabric is operated. The design of  FIG. 4  provides for a cascaded connection matrix using interconnected elements and devices using a single point of connection. The single point of connection enables centralized control of all protection schemes at all protection levels. Centralization can be employed using a single controller, where the  FIG. 3  design required a plurality of controllers. All statuses from all layers may be available using the design of  FIG. 4 .  
         [0041]     Additional incoming and outgoing data paths are presented as incoming paths  451   a  and  451   b  and outgoing paths  452   a  and  452   b . As shown, these paths interface directly with remote data indicator cross connect fabric  450  and may pass through or employ unified HO/LO cross connect fabric  401 . These paths typically include the HP-RDI and/or HP-REI signal values.  
         [0042]     It will be appreciated to those of skill in the art that the present design may be applied to other systems that perform data processing, and is not restricted to the communications structures and processes described herein. Further, while specific hardware elements and related structures have been discussed herein, it is to be understood that more or less of each may be employed while still within the scope of the present invention. Accordingly, any and all modifications, variations, or equivalent arrangements, which may occur to those skilled in the art, should be considered to be within the scope of the present invention as defined in the appended claims.