Patent Publication Number: US-7586941-B2

Title: Method and apparatus for translating SDH/SONET frames to ethernet frames

Description:
RELATED APPLICATIONS 
   This application claims priority to U.S. Provisional Application Ser. No. 60/314,801, filed on Aug. 24, 2001, the contents of which are incorporated herein in their entirety by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a network switching architecture, and more particularly to mapping or translating of SDH/SONET framing to Ethernet Framing and vice versa. 
   BACKGROUND OF THE INVENTION 
   A number of Metropolitan Area Networks (MAN) and Wide Area Networks (WAN) utilize a Time Division Multiplexing (TDM) Synchronous Optical Network (SONET) network architecture, or a Synchronous Digital Hierarchy (SDH) network architecture. In contrast, a number of Local Area Networks (LANs) utilize an Ethernet network architecture. 
   The SDH/SONET standards evolved originally for use in a voice network. SDH is a European version of a standard that is substantially the same as the SONET standard developed in North America. SDH/SONET contains connection oriented synchronous TDM circuit switching technology. An SDH/SONET configured network runs at the same clock domain (e.g., every section of the network can be traced to a primary clock reference). The network allocates fixed bandwidth time slots for each circuit. The SDH/SONET architectures are connection based protocols in that there is a physical circuit arrangement between ports in a switch to establish an end to end path. The digital transmissions in signals traveling through an SDH/SONET network occur at the same rate, however there may be a phase difference between the transmissions of any two signals caused by time delays or jitter in the transmission system. 
   Ethernet evolved primarily as a data network. In contrast to SDH/SONET, Ethernet is a connectionless asynchronous Collision Sense, Multiple Access with Collision Detection (CSMA/CD) packet switching technology. The Ethernet architecture does not rely on a single clock domain like the SDH/SONET architecture. The Ethernet architecture sends a series of packets across the network containing data. Whenever a packet needs to be sent, the transmitter will try to transmit the packet. The Ethernet architecture is also connectionless in that the packets travel from node to node within the network without establishing a physical or logical circuit. The end to end path is discovered through a process called “Bridging”. Ethernet is fundamentally a Local Area Network (LAN) technology. 
   SDH/SONET networks provide reliable, guaranteed available bandwidth, low jitter connections. These characteristics are required for voice quality networks. SDH/SONET, however, is bandwidth inefficient and has a higher overhead than many other network architectures. Ethernet networks, in contrast, provide lower reliability best effort delivery, and low cost bandwidth connections. These characteristics are suitable for data quality networks. Ethernet has non-guaranteed transmission and low overhead, and supports fewer operational functions than SDH/SONET. In SDH/SONET, once the circuit is established, bandwidth is allocated for an application and cannot be used by any other application, even if the original application is not using the bandwidth. In Ethernet, applications only use bandwidth when they need the bandwidth to transmit packets. 
   A known approach of transforming Ethernet data traffic into SDH/SONET is to encapsulate or tunnel the data into SDH/SONET data traffic. Encapsulation entails taking data provided by a higher-layer entity as the payload for a lower-layer entity, and applying a header and a trailer as dictated by the protocol. The encapsulation process places the data payload into a frame for transmission. 
   A tunnel is a mechanism for encapsulating one protocol within another. A tunnel is used to transport information between devices using one form of communication across an infrastructure that only supports a different form, without translating from the first protocol to the second. Several standards are known for tunneling, such as RFC 2651, PPP over SONET/SDH, ITU-T Recommendation X.85/Y.1321, IP over SDH using LAPS, ITU-T Pre-published Recommendation X.86, Ethernet Over LAPS and IEEE Draft P802.3ae. There are also several proposals for Virtual Concatenation Extensions to SDH/SONET Standards, however no single standard has been established. 
   In encapsulation methods, a complete original frame is packed into an encapsulating frame. When this is done, overhead bytes of both frames are transmitted. This means that encapsulation is less efficient with regard to the use of overhead bandwidth. Current methods of encapsulation are also restricted to support only concatenated SDH/SONET frames. They provide only one single “pipe” to connect to LAN networks. 
   Current methods of encapsulation focus on converting Ethernet over SONET. Thus, the methods have the same bandwidth inefficiency problem that SDH/SONET networks have, in that bandwidth is allocated even if there is no traffic being transmitted over the SDH/SONET port. 
   Further, in encapsulation, both ends of the circuit have to be of the same port type. In addition, when encapsulating, the encapsulating protocol must support data field length larger than that of the protocol being encapsulated. 
   SUMMARY OF THE INVENTION 
   There is a need in the art for a translation engine for more efficiently translating Ethernet frames to SDH/SONET frames and vice versa. The present invention is directed toward further solutions to address this need. 
   In accordance with one embodiment of the present invention, a translation system for translation between SDH/SONET frames and Ethernet frames is provided. The system includes a buffer for holding SDH/SONET frames. An Ethernet Media Access Control (MAC) address for a corresponding SDH/SONET TDM slot is further provided. A translation engine for translating SDH/SONET frames into Ethernet frames is in communication with an output interface. 
   In accordance with example embodiments of the present invention, the translation system further includes an add/drop mechanism in communication with the SDH/SONET frames for adding or dropping frame overhead bytes. The add/drop mechanism can be in the form of an ASIC, a Field Programmable Gate Array (FPGA), or a Network Processor. 
   In accordance with example embodiments of the present invention, the translation engine can include an ASIC, FPGA, and/or a Network Processor in communication with an SDH/SONET Framer, Ethernet MAC hardware, Ethernet physical hardware, and buffer logic to move the SDH/SONET frames and the Ethernet frames to and from the SDH/SONET Framer and the Ethernet MAC hardware. 
   In accordance with further aspects of the present invention, the Ethernet MAC hardware is modified to allow for multiple unique Ethernet MAC addresses. The Ethernet MAC hardware allows frames to travel therethrough without changing Source MAC Address or Destination MAC Address fields. Further, the payload data can include SDH/SONET traffic that is channelized and/or concatenated. 
   In accordance with another embodiment of the present invention, a translation system for translation between Ethernet frames and SDH/SONET frames includes a buffer for holding Ethernet frames. An Ethernet MAC address is provided for a corresponding SDH/SONET TDM slot. A translation engine for translating Ethernet frames into SDH/SONET frames also communicates with an output interface. 
   In accordance with still another embodiment of the present invention, a method of translating payload data from SDH/SONET frames to Ethernet frames is provided. The method includes providing an SDH/SONET payload. The SDH/SONET payload is sent through a translation engine to translate the SDH/SONET payload into an Ethernet payload. 
   In accordance with one aspect of the present invention, the SDH/SONET payload passes through a buffer. 
   In accordance with yet another embodiment of the present invention, a method of translating payload data Ethernet frames to SDH/SONET frames is provided. The method includes providing an Ethernet payload. The Ethernet payload is sent through a translation engine to translate the Ethernet payload into an SDH/SONET payload. 
   In accordance with further aspects of the present invention, the translation engine includes an ASIC, FPGA, and/or a Network Processor in communication with an SDH/SONET Framer, Ethernet MAC hardware, Ethernet physical hardware, and buffer logic to move the payload data to and from the SDH/SONET Framer and the Ethernet MAC hardware. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and aspects of the present invention will become better understood with regard to the following description and accompanying drawings, wherein: 
       FIG. 1  illustrates the translation of a SDH/SONET frame into an Ethernet Frame, in the illustrative embodiments of the present invention; 
       FIG. 2  is a diagrammatic illustration of a hardware architecture for translation of a SDH/SONET frame with channelized payloads to Ethernet frames using one Ethernet framer, according to a first illustrative embodiment of the present invention; 
       FIG. 3  is a diagrammatic illustration of a hardware architecture for translation of a SDH/SONET frame with concatenated payloads to Ethernet frames using one Ethernet framer, according to a second illustrative embodiment of the present invention; and 
       FIG. 4  is a diagrammatic illustration of a hardware architecture for translation of a SDH/SONET frame with channelized payloads to Ethernet frames using “N” Ethernet framers, according to a third illustrative embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   An illustrative embodiment of the present invention relates to the conversion of SDH/SONET frames to Ethernet frames, and vice versa. It is desirable to enable voice networks to transmit data and data networks to transmit voice signals. Ethernet is a known network technology for the transmission of data signals, while SDH/SONET is a known network technology for voice transmission. As technology evolves, there are increasing demands for sending voice over Ethernet architectures, and data over SDH/SONET architectures. Hence, there is a need to provide translation between SDH/SONET and Ethernet. 
   As utilized herein, translation is a process of mapping of Ethernet MAC addresses to corresponding SDH/SONET TDM slots, and the conversion of the SDH/SONET frames to and from Ethernet frames. The translation can include support for SDH/SONET payload and overhead. 
   The teachings of the present invention provide a mechanism to map SDH/SONET TDM slots to Ethernet source and destination MAC addresses. The present invention provides the infrastructure to support translation of channelized or concatenated SDH/SONET TDM circuits, SDH/SONET Asynchronous Transfer Mode (ATM) circuits and Packet Over SONET (POS) circuits. The teachings of the present invention enable SDH/SONET TDM emulation services on Ethernet networks. 
   In order to appreciate operation of the illustrative embodiments described herein, it is helpful to understand the Open Systems Interconnect (OSI) network hierarchy, which views a network as being composed of several hierarchical layers. In the hierarchy, Layer 1 is the physical layer containing elements that perform the transmission of signals within the network. Layer 2 is the data link layer, which provides services that allow direct communication between devices across the underlying physical channel of Layer 1. Layer 3 is the network layer, which is responsible for station-to-station data delivery over multiple data links. The network layer is responsible for the routing of packets across the network. Layer 4 is the transport layer, which provides an error-free, sequenced, guaranteed delivery, message service that allows process to process communication between stations on a network. Layer 5 is the session layer, which deals with the establishment of communications between applications. This layer is useful for security applications. Layer 6 is the presentation layer, which enables the sharing of data between networked systems using different methods of local data representation. Finally, Layer 7 is the application layer. This layer provides generic application functions, such as email, file transfer capability, and the like. 
   The present invention also supports SDH/SONET grooming of channelized payload (i.e., consolidating or segregating traffic to make the data flow more efficient) or concatenated payload (i.e., service signals linked together) functionality. SDH/SONET, being a multiplexing technology, allows for several streams of bits and/or bytes to be multiplexed into a bigger stream, with Overhead (i.e., bits in a digital stream utilized to carry information other than traffic signals) and Payload (i.e., the portion of the signal available for carrying service signals) included. Each stream or channel in SONET is called Synchronous Transport Signal-1, (STS-1), and in SDH, each stream is called Synchronous Transport Module-1 (STM-1). STS-1 stream is 51.84 Mbps bandwidth and STM-1 stream is 155.52 Mbps bandwidth. 
   The teachings of the present invention can be implemented with discrete components using different chips integrated at a board level. Alternatively, the teachings of the present invention can be implemented using ASIC cores of various components in an ASIC level. Various options are available wherein the ASIC implementation can include an SDH/SONET Framer, Ethernet Media Access Control (MAC) hardware, Ethernet Physical (PHY) hardware, and/or the buffer logic to move data to and from the SDH/SONET Framer to the Ethernet MAC. 
     FIGS. 1 through 4 , wherein like parts are designated by like reference numerals throughout, illustrate example embodiments of a method and apparatus for translating a SONET frame to an Ethernet frame, and vice versa, according to the teachings of the present invention. Although the present invention will be described with reference to the example embodiments illustrated in the figures, it should be understood that many alternative forms can embody the present invention. One of ordinary skill in the art will additionally appreciate different ways to alter the parameters of the embodiments disclosed, such as the size, shape, or type of elements or materials, in a manner still in keeping with the spirit and scope of the present invention. 
   The method of the present invention is depicted utilizing a diagrammatic representation of the various elements forming the SDH/SONET and Ethernet networks.  FIG. 1  illustrates a schematic representation of the flow of data in an SDH/SONET to Ethernet translation. An SDH/SONET (SDH STM-N or SONET STS-N) frame  101  includes payload data  101 A, which represents the data being serviced by the translation method of the present invention. There is additionally a section overhead  101 D, representing nine bytes of overhead accessed, generated, and processed by section terminating equipment. The section overhead  101 D organizes the framing of the signal, as well as monitors performance. Line overhead  101 C represents eighteen bytes of overhead accessed, generated, and processed by line terminating equipment. The line overhead  101 C manages functions such as locating the synchronous payload envelope (a SONET structure that carries the payload) in the frame  101 , multiplexing or concatenating signals, performance monitoring, automatic protection switching, and line maintenance. Path overhead  101 B represents overhead that is accessed, generated, and processed by path terminating equipment. Path overhead  101 B includes nine bytes of STS Path Overhead and, if the frame is VT structured, five bytes of VT Path Overhead. An add/drop mechanism  102  can work in conjunction with the SONET frame  101  to add/drop overhead bytes as required by the method of the present invention. 
   A buffer  103  used to temporarily store data during processing, includes a plurality of STM-1/STS-1 TDM streams, each stream disposed in an STM-1/STS-1 TDM slot  103 E through  103 F. A plurality of streams is located between slots  103 E and  103 F, the exact quantity of which is determined by the amount of payload data being serviced. 
   Each STM-1/STS-1 TDM stream in each STM-1/STS-1 TDM slot  103 E through  103 F includes a payload data section  103 A through  103 B. The payload data section  103 A serves to temporarily store the data being serviced as it translates from the SDH/SONET frame  101  to an Ethernet frame  105 . 
   Each STM-1/STS-1 TDM slot  103 E through  103 F has a source MAC address  103 G to  103 H associated therewith. The source MAC addresses  103 G to  103 H can be pre-configured in hardware, or configured via an external means. There is also a destination MAC address  103 C through  103 D associated with each STM-1/STS-1 TDM slot  103 E through  103 F. The destination MAC addresses  103 C through  103 D can be configured via an external means. The destination MAC addresses  103 C through  103 D can be pre-configured, or can be determined at runtime when a packet arrives. The source and destination addresses provide a uni-directional path for the payload data to travel once it arrives at the buffer  103 . The source MAC addresses are stored in the Ethernet frame  105  source field  105 D during construction of the Ethernet frame  105 . The destination MAC addresses are stored in the Ethernet frame  105  destination field  105 B during construction of the Ethernet frame  105 . 
   The Ethernet frame  105  also includes a preamble and start of frame delimiter  105 C, which is a frame field used to allow a receiver to properly synchronize on the frame before decoding a remainder of the frame. The remainder of the frame being in the form of a data link Ethernet encapsulation. A source field  105 D maintains source information of the payload data signal. Payload data  105 A represents the data transmitted from the payload data  101 A of the SONET frame  101 . A frame check sequence  105 E is a polynomial code used to detect errors in the Ethernet frame  105 . 
   The SDH/SONET frame  101  can include several STM-1/STS-1 streams multiplexed together into a larger STM-N/STS-N frame, where “N” indicates the number of STM-1/STS-1 streams that are byte interleaved. In the case of SDH, each STM-1 operates at 155.52 Mb/s. In the case of SONET, each STS-1 operates at 51.84 Mb/s. 
   The data flow between the SDH/SONET frame  101  and the Ethernet frame  105  in accordance with the present invention is illustrated in  FIG. 1 . To translate the SDH/SONET frame  101  into the Ethernet frame  105 , one embodiment of the method of the present invention places the payload data  101 A, which excludes Path Overhead (POH) bytes  101 B, into the payload data section  105 A of the Ethernet frame  105 . POH bytes relate to overhead that is accessed, generated, and processed by path terminating equipment. The buffer  103  can buffer the data, if desired. The buffer  103  can also be segregated such that there is one data section  103 A through  103 B of the buffer  103  per STM-1/STS-1 TDM slot  103 E through  103 F. 
   The Ethernet payload data section  105 A continues to fill with the payload data from the SDH/SONET frame  101  to the Ethernet frame  105 . While the SDH/SONET frame  101  is received, the Ethernet payload data section  105 A continues to fill until a maximum data length (e.g., 1500 bytes) is attained. When the Ethernet payload  105 A is filled to maximum data length it is transmitted. Incoming SDH/SONET payload  101 A is then filled into the Ethernet payload data section  105 A of the next Ethernet frame  105  to be generated. If the Ethernet frame&#39;s  105  payload data section  105 A partially fills, and there is an idle pattern in the SDH/SONET frames  101 , the Ethernet frame  105  is transmitted with the frame length. The maximum data length is based on the Ethernet maximum transmission unit configured in the Ethernet hardware. 
   To translate the Ethernet frame  105  into the SDH/SONET frame  101 , the process reverses. The Ethernet payload data section  105 A travels to the SDH/SONET payload data section  101 A of the SDH/SONET frame  101 , as shown in  FIG. 1 . The buffer  103  can buffer the data. Again, the buffer  103  can be segregated, such that there is one payload data section  103 A through  103 B of the buffer  103  for each STM-1/STS-1 stream in each STM-1/STS-1 slot  103 E through  103 F. 
   When translating the payload data from the Ethernet frame  105  to the SDH/SONET frame  101 , the method of the present invention continuously inserts the bits and/or bytes into the SDH/SONET data payload section  101 A. The bits/bytes are then transmitted in the next outgoing SDH/SONET frame  101 . 
   SDH/SONET Path Overhead  101 B transparency can be achieved by adding or dropping overhead bytes from the SDH/SONET frame  101  using an add/drop mechanism  102  in communication with the SDH/SONET frame  101 . 
   The SDH/SONET path overhead  101 B, line overhead  101 C (multiplex for SDH), and section overhead  101 D (regenerator for SDH), can be dropped off from an incoming SDH/SONET TDM STM-1/STS-1 stream and saved by add/drop mechanism  102 , which can be in the form of an ASIC, to be used to support Path, line/multiplex, and section/regenerator transparency. Similarly for the outgoing SDH/SONET TDM frame the corresponding overhead bytes from the path overhead  101 B, line overhead  101 C (multiplex), and section overhead  101 D (regenerator) can be added into the outgoing SDH/SONET frame&#39;s  101  overhead bytes by the add/drop mechanism  102 . The overhead bytes are managed through some external means, such as being taken from an ingress SDH/SONET port and used by an egress SDH/SONET port via some additional hardware. 
   Path, multiplex/line and regenerator/section transparency can also be implemented by sending those overhead bytes from the path overhead  101 B, line overhead  101 C, and section overhead  101 D via Ethernet packets to the destination from the source. Once at the destination, the bytes can be reinserted into the SDH/SONET framing by using Framers (not shown) that allow for such capability. 
   One of ordinary skill in the art will appreciate that the source and destination ports can be any combination of SDH/SONET or Ethernet ports. 
   There are several possible implementations of the method in accordance with the teachings of the present invention. One example embodiment details how grooming can be supported with one Ethernet Framer (MAC and PHY), as shown in  FIG. 2 . A second embodiment, shown in  FIG. 3 , illustrates how concatenation can be supported with a single Ethernet framer. A third embodiment, shown in  FIG. 4 , illustrates an apparatus in accordance with the teachings of the present invention that supports the translation of channelized signals with multiple Ethernet framers. 
   Grooming is the consolidation or segregation of traffic to improve efficiency of traffic flow. The data is therefore modified in some manner to consolidate or segregate the data into a more efficient structure for transport. In order to translate a channelized SDH/SONET STM-N/STS-N Frame  101  to an Ethernet Frame  105 , each individual STM-1/STS-1 frame within the SDH/SONET STM-N/STS-N frame  101  is translated to its corresponding Ethernet Frame  105 . 
     FIG. 2  illustrates a board  200  for translating SDH/SONET to Ethernet as one embodiment of a translation engine. The board  200  includes an SDH/SONET framer  201 , and an Ethernet framer  203 . The SDH/SONET framer  201  takes transmitted or received data and encapsulates it into one or more frames (frames  101  from  FIG. 1 ). The Ethernet framer  203  takes transmitted or received data and encapsulates it into frames (frames  105  from  FIG. 1 ). The board  200  further includes an ASIC  202  that maintains transmit buffers  202 C through  202 D and receive buffers  202 E through  202 F, which store payload data from the framers  201  and  203 . Each SDH/SONET TDM slot  202 A through  202 B has a transmit buffer  202 C through  202 D which can store the SDH/SONET frame  101  information and can be used to generate the translated Ethernet frame  105 . Each SDH/SONET TDM slot  202 A through  202 B has a receive buffer  202 E through  202 F, which can store the Ethernet frame  105  information and can be used to generate the translated SDH/SONET frame  101 . An Ethernet MAC chip  203 A supports a multiple of MAC addresses required to support mapping of each STS-1/STM-1 TDM slot, while an Ethernet PHY forms the physical interface to the Ethernet for the flow of data. 
   One SDH/SONET Framer  201  can be used in accordance with one embodiment of the present invention. As in the previous illustration, a plurality of STM-1/STS-1 TDM slots exist between the STM-1/STS-1 TDM slot  202 A and the STM-1/STS-1 TDM slot  202 B. Each STM-1/STS-1 TDM slot  202 A through  202 B requires one transmit buffer  202 C through  202 D and one receive buffer  202 E through  202 F to store payload data in bytes from each frame (frame  101  or frame  105 ). The single Ethernet framer  203  with the MAC  203 A and PHY  203 B hardware devices of the same or higher speed as the SDH/SONET framer  203  can be used in conjunction with the ASIC  202 . A microprocessor interface  204  to configure, control, and monitor aspects of the hardware. 
   In accordance with the embodiment illustrated in  FIG. 2 , in order to support channelized grooming, a form of mapping is required between each individual STM-1/STS-1 TDM slot  202 A through  202 B, each of multiple Ethernet destination MAC addresses (DMA)  202 G through  202 H, and each of multiple source MAC addresses (SMA)  202 I through  202 J on the Ethernet MAC chip  202 A. 
   In the SDH/SONET to Ethernet direction, the DMA  202 G through  202 H of the corresponding STM-1/STS-1 TDM slot  202 A through  202 B is used with the SMA  202 I through  202 J of the corresponding STM-1/STS-1 TDM slot  202 A through  202 B. In the Ethernet to SDH/SONET direction the source MAC address  105 D of the incoming Ethernet packet  105  can be used to match the SMA  202 I through  202 J to demultiplex to the corresponding STM-1/STS-1 TDM slot  202 A through  202 B. The received source MAC address  105 D of the incoming Ethernet packet  105  can be used for verification or security, such that if desired, the data can be discarded if the source MAC address  105 D of the incoming Ethernet packet  105  does not match the DMA  202 G through  202 H configured locally. 
   In accordance with one embodiment of the present invention, the Ethernet MAC hardware  203 A is modified to allow for multiple unique Ethernet MAC addresses per MAC device  203 A. This allows the single MAC chip to receive frames for multiple specific MAC addresses which have been correspondingly mapped to appropriate STM-1/STS-1 TDM slots  202 A through  202 B. If not already capable, the MAC hardware  203 A also allows for frames created by the ASIC  202  to be transmitted straight through without changing the SMA  202 I through  202 J and DMA  202 G through  202 H fields. These modifications allow the system of the present invention to transmit and receive several MAC address frames with one set of MAC and PHY hardware devices  203 A and  203 B. 
   In order to translate a concatenated SDH/SONET frame (indicated as STM-Nc/STS-Nc) to an Ethernet frame, the complete concatenated payload is translated to corresponding Ethernet frames. The concatenated STM-Nc/STS-Nc TDM slot  302 A requires one transmit buffer  302 B and one receive buffer  302 C to store the concatenated SDH/SONET payload data in bytes from its concatenated SDH/SONET frame (frame  101 ) and Ethernet frame (frame  105 ) and one set of Ethernet MAC  303 A and PHY  303 B hardware interfaces.  FIG. 3  illustrates another embodiment of a translation engine in the form of a board  300  suitable for translating concatenated frames in accordance with one embodiment of the present invention. The board includes an ASIC  302  that maintains transmit buffers  302 B and receive buffers  302 C, which store payload data from framers  301  and  303 . A MAC chip  303 A and a PHY hardware interface  303 B can be part of the Ethernet framer  303 . 
   The implementation is similar to the translation of the channelized groomed data described above. In the SDH/SONET to Ethernet direction, a destination MAC address (DMA)  302 D of a corresponding STM-1/STS-1 TDM slot  302 A is used with a source MAC address (SMA)  302 E of the corresponding STM-1/STS-1 TDM slot  302 A. In the Ethernet to SDH/SONET direction the source MAC address  105 D of the incoming Ethernet packet  105  can be used to match the SMA  302 E is used for the corresponding STM-1/STS-1 TDM slot  302 A. The received source MAC address  105 D of the incoming Ethernet packet  105  can be used for verification or security, such that if desired, the data can be discarded if the source MAC address  105 D of the incoming Ethernet packet  105  in the particular packet does not match the DMA  302 D configured locally. 
   It should be noted that logically this is a special or base (number of TDM slots=1) case of the previously described embodiment of  FIG. 2 . Only one TDM slot DMA  302 D and SMA  302 E is used, and the entire buffer (transmit buffer  302 B and receive buffer  302 C) is utilized. A microprocessor interface  304  can be used to configure, control, and monitor various aspects of the hardware. The SMA  302 E can be the same as the MAC chip&#39;s  303 A MAC address. 
   In the above embodiments, the same hardware architecture and implementation can be used with a configurable option in the ASICS  202  and  302  to indicate the implementation of the grooming channelized mode or the concatenated mode. 
   The implementation of the present invention can be executed by creating a translation engine using standard SDH/SONET Framer hardware, buffer hardware, and Ethernet MAC and PHY hardware. The translation engine can include various forms of these components as separate modules or incorporated into a single module. The translation engine can be implemented using ASIC, Field Programmable Gate Array (FPGA) and/or Network Processor technology. The translation engine can provide support for translating to and from any protocol standards that are used to tunnel or encapsulate Ethernet over SONET (EoS). Such standard protocols include Packet Over SONET (POS), Asynchronous Transfer Mode (ATM), and the like. The translation engine can be configured such that it can provide internetworking between SDH/SONET TDM, SDH/SONET ATM or POS and Ethernet interfaces. 
   One requirement for practicing the present invention in the SDH/SONET and Ethernet realm is that the technology allow for the implementation of the SDH/SONET framer at certain speeds, such that the Ethernet MAC and PHY chipsets are available at the same, or higher, speeds. Otherwise, the overall translation speed of the resulting device is limited by the speed restriction of one or the other of the framers and the MAC and PHY hardware. Buffering can be used to support differences in speeds between the SDH/SONET and Ethernet hardware. From a hardware perspective, it is likely that the speeds of the various components will keep pace with one another based on the fact that SDH/SONET Framers place more requirements on hardware than Ethernet Framers for the same speed. From a standards perspective, SDH/SONET framers have been specified at multiples of 4 times the previous speed, and Ethernet framers have been specified at multiples of 10 times the previous speed. 
   The teachings of the present invention can also be utilized with other Ethernet hardware or other technology hardware having similar translation issues. In addition, the present invention can be implemented with the Ethernet chips being configured in half or full duplex mode to function. 
   In order to translate a groomed channelized STM-N/STS-N frame to Ethernet frames, each individual STM-1/STS-1 frame is translated to corresponding Ethernet frames. An additional translation engine embodiment is illustrated in  FIG. 4 , wherein a single SDH/SONET Framer  401  is utilized. Each STM-1/STS-1 TDM slot  402 A through  402 B requires one transmit buffer  402 C through  402 D and one receive buffer  402 E through  402 F to store the payload in the form of bytes from a corresponding frame. Each STM-1/STS-1 TDM slot  402 A through  402 B requires one set of Ethernet MAC hardware  403 A through  403 B and one set of Ethernet PHY  403 C interface hardware through  403 D of the same, or higher, speed as the SDH/SONET STM-1/STS-1 TDM stream  402 A through  402 B. The SMA  302 E can be the same as the MAC chip&#39;s  303 A MAC address. A microprocessor interface  404  configures, controls, and monitors various aspects of the hardware. 
   In accordance with the teachings of this embodiment, channelized grooming is supported in that a MAC address is associated with each STM-1/STS-1 TDM slot  402 A through  402 B. An ingress SDH/SONET port STM-1/STS-1 TDM slot can be set up to connect with an egress SDH/SONET port STM-1/STS-1 TDM slot, or another egress Ethernet port. Likewise, an ingress Ethernet port can be set up to connect with an egress SDH/SONET port STM-1/STS-1 TDM slot, or another egress Ethernet port. 
   Each STM-1 TDM stream operates at 155.52 Mb/s. If possible, by over clocking 10/100 Mb/s Ethernet MAC hardware  403 A through  403 B and PHY interface hardware  403 C through  403 D to operate at 155.52 Mb/s, standard Ethernet components can be utilized to implement this embodiment. Because 10/100 Mb/s chipset and cores are available, and relatively inexpensive, they can be utilized to implement the teachings of the present invention. The arrangement of components used to translate SDH can also be used for SONET, because each STS-1 TDM stream operates at 51.84 Mb/s. 
   A requirement for implementation of this embodiment is that technologies exist to implement the packaging aspects of an ASIC implementation. As the STM-N/STS-N signal levels increase, the number of STM-1/STS-1 streams supported by the signals also increases, which in turn requires a larger number of pins to support the incoming/outgoing STM-1/STS-1 streams and incoming/outgoing Ethernet streams. The ASIC utilized with the present invention must therefore support the larger number of pins. 
   Several vendors make SDH/SONET Framers and MAC and PHY hardware components that can be utilized in accordance with the teachings of the present invention. Venders such as Applied Micro Circuits Corporation (AMCC) of San Diego, Calif., PMC-Sierra, Inc. of Burnaby, British Columbia, Agere Systems of Allentown, Pa., Vitesse Semiconductor Corporation of Camarillo, Calif., and Intel Corporation of Santa Clara, Calif. make SDH/SONET Framer and/or Ethernet device products. SDH/SONET framer products from AMCC include 4802 Missouri Chip, 19202 Ganges Chip, and 4801 Amazon Chip. Intel products include the SONET/SDH Framer IXF6048/6012 and Ethernet MAC IXF440/IXF1002. There is an Intel Ethernet PHY LTX family of products. Vitesse provides an additional SONET/SDH Framer VSC91xx Product Family. 
   An example implementation of the embodiment depicted in  FIG. 2  can be executed as follows. The AMCC 4801 Missouri Chip can be used for the SDH/SONET framer  201 . The Intel IXF1002 MAC Chip can form the MAC chip  203 A and the LTX1000 PHY chip can form the PHY  203 B hardware. The ASIC  202  is then custom designed in accordance with the layout depicted in  FIG. 2 . 
   Because the present invention utilizes a method of translation, the present invention utilizes bandwidth more efficiently by sending only the payload bytes of the protocol. The present invention is also useful in that it supports translation of channelized groomed SDH/SONET frames. The present invention allows for SONET over Ethernet translation, which takes advantage of Ethernet&#39;s bandwidth efficiency. The method of the present invention supports the translation of a circuit having a first port of one type (e.g., SDH/SONET) to a second port of a different type (e.g., Ethernet). Thus, SDH/SONET and Ethernet devices can coexist in a single managed network, and do so through use of an efficient process for translating payload from one port to the other. 
   Numerous modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure may vary substantially without departing from the spirit of the invention, and exclusive use of all modifications that come within the scope of the appended claims is reserved. It is intended that the present invention be limited only to the extent required by the applicable rules of law.