Abstract:
A method and apparatus enables Ethernet data transport over a serial digital interface network. An Embedder/DeEmbedder for embedding Ethernet derived data and for de-embedding Ethernet derived data supports selective use of the active video region of the SDI frame and the unused HANC space for transporting Ethernet media independent interface data.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the electrical arts and to the transport of Ethernet data. More particularly, this invention relates to methods and apparatus for enabling transport of Ethernet data over a serial digital interface transport service. 
   2. Description of Related Art 
   Networks for transporting Ethernet data are known in office and business environments for communicating digital data. Such networks are termed local area networks (LAN) because Ethernet data may transmitted only over short distances, typically less than one kilometer. Data transport over longer distances and in particular between LAN&#39;s is accomplished using long distance communications means such as a link to a wide area network (WAN). 
   The exchange of video content among distant parties prompted the creation of a means to transport digitized video over considerable distances using a network with a Serial Digital Interface (SDI). Digital video signals are therefore typically transmitted over the SDI transport according to one or more SDI standards. 
   SDI signals are self-synchronizing, typically using 8 bit or 10 bit data words and a data rate of 270 Mbit/sec. Blocks of data words transmitted according to the SDI standard are referred to as frames. An SDI frame includes an active video region and inactive ancillary spaces including a horizontal (HANC) space. 
   Some offices have both an Ethernet LAN and a link to an SDI network. These offices would benefit from a method and means for transmitting Ethernet data over the SDI link. However, traditional SDI links will not transport Ethernet data signals. 
   SUMMARY OF THE INVENTION 
   The present invention satisfies a long felt need to enhance the utilization of SDI video transport services by enabling the transport of Ethernet and other data services including video data transport over SDI networks. 
   A preferred embodiment of the present invention includes an Embedder/De-Embedder that enables the transfer of Ethernet data over the SDI network. In particular, an Embedder function of the preferred embodiment uses a physical level Ethernet device (PHY) to convert the raw Ethernet data traffic into Media Independent Interface (MII) Data. 
   A Field-Programmable Gate Array (FPGA), a type of logic chip that can be programmable, is specifically programmed to place the MII data into the active video region of the SDI frame. The SDI frame with its embedded Ethernet data is then transported over standard SDI equipment and routed to another Embedder/De-Embedder apparatus. 
   When the embedded data reaches its destination, a second Embedder/De-Embedder and in particular the De-Embedder then extracts the Ethernet MII data and passes it to another PHY device. The PHY device then transmits the physical level Ethernet data. 
   To the Ethernet signal and all protocols that ride on it, the apparatus of the present invention appears to be a standard cable. But, the transport means is an SDI network and what is transported is media independent interface data derived from the Ethernet data or Ethernet MII data. In other words the present invention does not interact at either the OSI Data Link or Transport layer or at any higher layers in the OSI Reference Model. 
   In another embodiment of the invention, the Embedder/Deembedder apparatus is similar, but here the FPGA is also programmed to place the Ethernet MII data into the unused Horizontal Ancillary (HANC) data space of the SDI frame. This allows the use of one or both of the active video region and the HANC space to transport Ethernet MII data. Consequently, in this embodiment the SDI transport is capable of carrying both video and Ethernet data simultaneously. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The novel features of this invention will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar characters refer to similar parts and in which: 
       FIG. 1  is a block diagram of the data transport apparatus of the present invention. 
       FIG. 2  is a block diagram of the Embedder/DeEmbedder of the data transport apparatus of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a block diagram of a network system  10 . Ethernet data is transferred between two host computers  12  via an SDI video transport network  20 . When Ethernet data  13  is sent from one computer  12  and routed via a router  14 , it encounters the Embedder/De-Embedder apparatus  16  of the present invention. 
   The Ethernet data  13  is typically carried at speeds of 10M and 100M. In an embodiment, 1G and 10G Ethernet may also be transported over the SDI network but throughput would be limited because of the lower data rate (270 Mbits/sec) of the SDI network. It should be noted that when both video and Ethernet are carried simultaneously, maximum Ethernet throughput is reduced since the Ethernet and video data share the available SDI bandwidth. 
     FIG. 2  shows a block diagram of the Embedder/De-Embedder apparatus  16 . The Embedder/De-Embedder apparatus  16  includes a data converter or PHY  18 , an Ethernet/SDI Embedder  19 , and an Ethernet/SDI De-Embedder  21 . 
   In an embodiment, the data converter, the Ethernet/SDI Embedder, and the Ethernet/SDI De-Embedder are contained in a common enclosure  30  and in some embodiments, all of these devices are implemented on a single circuit board. 
   Upon receipt of the Ethernet data  13  through the router  14 , the data converter  18  of the Embedder/De-Embedder apparatus  16  converts the raw Ethernet data  13  into Ethernet MII data  23 . The Ethernet MII data  23  is then embedded by the Ethernet/SDI Embedder  19 . In an embodiment, one or more field programmable gate arrays are associated with the Embedder/DeEmbedder and it is an FPGA that places this data into the active video region of the SDI frame. Here, the FGPA is programmed to perform the operation of placing the data into the active video region. 
   The data converter  18  has logic levels that are compatible with a selected FPGA. Any appropriate data converter interface may be used such as Intel&#39;s model LXT972A. In addition, FPGA devices are known in the industry, and any FPGA having sufficient size and speed may be used such as the Altera Cyclone FPGA. 
   The SDI frame with the embedded Ethernet MII data is transported over standard SDI cables  22  through the Video Transport Network  20  and routed via second router  14  to another Embedder/De-Embedder apparatus  16 . As the SDI frame  23  enters the Embedder/De-Embedder apparatus  16 , the Ethernet/SDI De-Embedder  21  extracts the incoming Ethernet MII data  23  and passes it to another data converter  18 . The data converter  18  transmits the physical level Ethernet data  13  to the second host computer  12 . 
   In another embodiment of the present invention, the FPGA is programmed to selectively place video or Ethernet MII data into the active video region of the SDI frame and Ethernet MII data into the unused HANC space of the SDI frame. In this embodiment, the SDI transport can carry one or both of video and Ethernet MII data. In particular, video and Ethernet MII data may be carried simultaneously. 
   In an embodiment where Ethernet MII data is carried only in the HANC space of the SDI frame, the throughput is about 4.1 Mbytes/sec. Therefore, 10M Ethernet may be transported in this embodiment without flow control while 100M Ethernet would require the use of flow control. 
   While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be understood by those skilled in the art that various changes in form and details can be made therein without departing form the spirit and scope of the invention as defined in the appended claims. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.