Abstract:
A communication system comprising: a first device; a second device; and communication cabling comprising four twisted wire pairs arranged to enable communication between the first device and the second device; the first and the second devices being operable to perform auto-negotiation on a communication path comprising a first two of the four twisted wire pairs, and to perform auto-negotiation on a communication path comprising a second two of the four twisted wire pairs, the second two twisted wire pairs being distinct from the first two twisted wire pairs, the first and second devices being operable to enable communication on the communication path comprising the second two twisted wire pairs in the event of a failure of the auto-negotiation on said communication path comprising said first two twisted wire pairs.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to the field of communication systems and more specifically to auto-negotiation in a communication system.  
         [0002]     The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. In a typical office environment each station or device is connected in a star configuration by a data cable comprising four twisted wire pairs to a central location. A switch or data hub located at the central location provides data switching services within the office environment as well as providing a gateway to the outside world.  
         [0003]     Ethernet technology is embodied in the IEEE 802.3 standard whose entire contents are incorporated by reference. The standard defines a number of layers and configurations, including a choice of physical transmission mediums. In particular physical layer specifications 10BASE-T, 100BASE-T and 1000BASE-T are defined for use with twisted wire pairs as the physical transmission medium.  
         [0004]     An auto-negotiation function is defined that allows a device to advertise enhanced modes of operation it possesses to a device at the remote end of a link segment and to detect corresponding enhanced operational modes that the other device may be advertising. Auto-negotiation is performed using a modified 10BASE-T link integrity test pulse sequence; however it does not test the link segment characteristics.  
         [0005]      FIG. 1  illustrates a high level block diagram of a system  10  operating according to 10BASE-T or alternatively 100BASE-T known to the prior art. System  10  comprises: a first device  20  comprising a transmitting physical layer entity (PHY)  30  and a receiving PHY  40 ; a second device  50  comprising a receiving PHY  40  and a transmitting PHY  30 ; and a physical transmission medium  60 , illustrated as an unshielded twisted pair cable comprising four twisted wire pairs  70 . For clarity, a first twisted wire pair  70  is labeled pair A, and a second twisted wire pair  70  is labeled B.  
         [0006]     Transmitting PHY  30  of first device  20  is connected via twisted wire pair  70 -A to receiving PHY  40  of second device  50 . Transmitting PHY  30  of second device  50  is connected via twisted wire pair  70 -B to receiving PHY  40  of first device  20 . Thus, a bidirectional communication link is formed between first device  20  and second device  50  comprising twisted wire pairs  70 -A, B. The other two twisted wire pairs  70  of unshielded twisted wire pair cable  60  are unused. In an exemplary embodiment as described in the above standard, and as depicted in  FIG. 1 , a first end of twisted wire pair  70 -A is connected to contacts  1  and  2  of the medium dependent interface (MDI) of first device  20  and a second end of twisted wire pair  70 -A is connected to contacts  3  and  6  of the MDI of second device  50 ; and a first end of twisted wire pair  70 -B is connected to contacts  1  and  2  of the MDI of second device  50  and a second end of twisted wire pair  70 -B is connected to contacts  3  and  6  of the MDI of first device  20 .  
         [0007]      FIG. 2  illustrates a high level block diagram of a system  100  operating according to 1000BASE-T known to the prior art. System  100  comprises: a first device  110  comprising four bidirectional PHYs  120 ; a second device  130  comprising four bidirectional PHYs  120 ; and a physical transmission medium  60 , illustrated as an unshielded twisted pair cable comprising four twisted wire pairs  70 . For clarity, a first twisted wire pair  70  is labeled pair A, second twisted wire pair  70  is labeled pair B, a third twisted wire pair  70  is labeled pair C and a fourth twisted wire pair  70  is labeled pair D.  
         [0008]     A first bidirectional PHY  120  of first device  110  is connected via twisted wire pair  70 -A to first bidirectional PHY  120  of second device  130 . A second bidirectional PHY  120  of first device  110  is connected via twisted wire pair  70 -B to second bidirectional PHY  120  of second device  130 . A third bidirectional PHY  120  of first device  110  is connected via twisted wire pair  70 -C to third bidirectional PHY  120  of second device  130 . A fourth bidirectional PHY  120  of first device  110  is connected via twisted wire pair  70 -D to fourth bidirectional PHY  120  of second device  130 . Thus, four bidirectional communication links are formed between first device  110  and second device  130  comprising twisted wire pairs  70 -A, B,C and D.  
         [0009]     In an exemplary embodiment as described in the above standard, and as depicted in  FIG. 2 , a first end of twisted wire pair  70 -A is connected to contacts  1  and  2  of the medium dependent interface (MDI) of first device  110  and a second end of twisted wire pair  70 -A is respectively connected to contacts  3  and  6  of the MDI of second device  130 . A first end of twisted wire pair  70 -B is connected to contacts  1  and  2  of the MDI of second device  130  and a second end of twisted wire pair  70 -B is respectively connected to contacts  3  and  6  of the MDI of first device  110 . A first end of twisted wire pair  70 -C is connected to contacts  4  and  5  of the MDI of first device  110  and a second end of twisted wire pair  70 -C is respectively connected to contacts  7  and  8  of the MDI of first device  110 . A first end of twisted wire pair  70 -D is connected to contacts  4  and  5  of the MDI of second device  130  and a second end of twisted wire pair  70 -D is respectively connected to contacts  7  and  8  of the MDI of first device  110 .  
         [0010]     Clauses  28  and  40  of the above mentioned standard require that auto-negotiation be accomplished on pairs  70 -A and  70 -B, emulating the arrangement of system  10  of  FIG. 1 . Thus, for auto-negotiation purposes, as shown in system  100 , pairs  70 -C and  70 -D are not utilized. In the event that a fault occurs in either twisted wire pair  70 -C or  70 -D, auto-negotiation will proceed unaffected on twisted wire pairs  70 -A, B.  
         [0011]      FIG. 3  illustrates a high level block diagram of a system  200  which is all respects identical with that of system  100  of  FIG. 2 , with the exception that twisted wire pair  70 -A has been broken. Thus, although twisted wire pairs  70 -B, C and D remain functional, system  200  is unable to accomplish auto-negotiation and communication is not enabled.  
         [0012]     What is therefore needed, and not known in the prior art, is a method and apparatus for auto-negotiation in a communication system in which a failure of the communication path comprising twisted wire pairs A and B occurs. Such a failure may occur due to a cable tear, connector failure or other hardware failure.  
       SUMMARY OF THE INVENTION  
       [0013]     Accordingly, it is a principal object of the present invention to overcome the disadvantages of prior art. This is provided in the present invention by enabling auto-negotiation on the communication path comprising pairs A and B, and in the event of a failure of auto-negotiation on the communication path comprising pairs A and B, auto-negotiation on the communication path comprising pairs C and D. In the event that auto-negotiation is successful on the communication path comprising pairs C and D and not successful on the communication path comprising pairs A and B, communication at 100 Mb/s or alternatively at 10 Mb/s is enabled on the communication path comprising pairs C and D.  
         [0014]     The invention provides for a communication system comprising: a first device; a second device; and communication cabling comprising four twisted wire pairs arranged to enable communication between the first device and the second device; the first and the second devices being operable to perform auto-negotiation on a communication path comprising a first two of the four twisted wire pairs, and to perform auto-negotiation on a communication path comprising a second two of the four twisted wire pairs, the second two twisted wire pairs being distinct from the first two twisted wire pairs, the first and second devices being operable to enable communication on the communication path comprising the second two twisted wire pairs in the event of a failure of the auto-negotiation on the communication path comprising the first two twisted wire pairs.  
         [0015]     In one embodiment the first and second devices are operable to perform the auto-negotiation on the communication path comprising the second two twisted wire pairs only in the event of a failure of the auto-negotiation on the communication path comprising the first two twisted wire pairs. In another embodiment the enabled communication on the second two twisted wire pairs is in accordance with the auto-negotiation on the communication path comprising the second two twisted wire pairs.  
         [0016]     In one embodiment the enabled communication on the second two twisted wire pairs is at one of 100 Mb/s and 10 Mb/s. In another embodiment the four twisted wire pairs are comprised within a single unshielded twisted pair cable.  
         [0017]     In one embodiment the first two twisted wire pairs are associated with contacts  1 ,  2 ,  3  and  6  of a medium dependant interface connector of one of the first device and the second device. In another embodiment the first two twisted wire pairs are associated with contacts  1 ,  2 ,  3  and  6  of respective medium dependant interface connectors of each of the first device and the second device.  
         [0018]     In one embodiment the second two twisted wire pairs are associated with contacts  4 ,  5 ,  7  and  8  of a medium dependant interface connector of one of the first device and the second device. In another embodiment the second two twisted wire pairs are associated with contacts  4 ,  5 ,  7  and  8  of respective medium dependant interface connectors of each of the first device and the second device.  
         [0019]     In one embodiment the auto-negotiation on the first two twisted pairs is in accordance with IEEE standard 802.3. In another embodiment the auto-negotiation on the second two twisted wire pairs is in accordance with the auto-negotiation on the first two twisted wire pairs.  
         [0020]     The invention independently provides for a method of performing auto-negotiation in a communication system comprising a first communication path and a second communication path, each of the first and the communication paths comprising a unique two twisted wire pairs, the method comprising: performing auto-negotiation over the first communication path; performing auto-negotiation over the second communication path; and in the event the performed auto-negotiation over the first communication path is not successful; enabling communication over the second communication path.  
         [0021]     In one embodiment the performing auto-negotiation over the second communication path is only in the event of a failure of the performed auto-negotiation over the first communication path. In another embodiment the enabled communication is in accordance with the performed auto-negotiation over the second communication path.  
         [0022]     In one embodiment the enabled communication over the second communication path is at one of 100 Mb/s and 10 Mb/s. In another embodiment the first communication path and the second communication path are comprised within a single unshielded twisted pair cable.  
         [0023]     In one embodiment the performed auto-negotiation over the first communication path is in accordance with IEEE standard 802.3. In another embodiment the performed auto-negotiation over the second communication path is in accordance with the performed auto-negotiation over the first communication path.  
         [0024]     The invention independently provides for a communication system comprising: a first device; a second device; and communication cabling comprising four twisted wire pairs, the four twisted wire pairs comprising a first two twisted wire pairs associated with data communication at 10 Mb/s and a second two twisted wire pairs not associated with data communication at 10 Mb/s; the first and the second devices being operable to perform auto-negotiation via the first two twisted wire pairs, and in the event of a failure of the auto-negotiation, to perform auto-negotiation via the second two twisted wire pairs.  
         [0025]     In one embodiment the first and second devices are further operable to communicate over the second two twisted wire pairs at one of 10 Mb/s and 100 Mb/s.  
         [0026]     Additional features and advantages of the invention will become apparent from the following drawings and description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout.  
         [0028]     With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the accompanying drawings:  
         [0029]      FIG. 1  illustrates a high level block diagram of a system operating according to 10BASE-T or alternatively 100BASE-T known to the prior art;  
         [0030]      FIG. 2  illustrates a high level block diagram of a system operating according to 1000BASE-T known to the prior art; and  
         [0031]      FIG. 3  illustrates a high level block diagram of a system which is all respects identical with that of  FIG. 2 , with the exception that a twisted wire pair normally used for auto-negotiation has failed;  
         [0032]      FIG. 4  illustrates a high level block diagram of a system operating in accordance with principle of the current invention;  
         [0033]      FIG. 5  illustrates a high level flow chart of the method of operation according to a first embodiment of the principle of the current invention; and  
         [0034]      FIG. 6  illustrates a high level flow chart of the method of operation according to a second embodiment of the principle of the current invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0035]     The present embodiments enable auto-negotiation on the communication path comprising pairs A and B, and in the event of a failure of auto-negotiation on the communication path comprising pairs A and B, auto-negotiation on the communication path comprising pairs C and D. In the event that auto-negotiation is successful on the communication path comprising pairs C and D and not successful on the communication path comprising pairs A and B, communication at 100 Mb/s or alternatively at 10 Mb/s is enabled on the communication path comprising pairs C and D.  
         [0036]     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.  
         [0037]      FIG. 4  illustrates a high level block diagram of a system  300  operating in accordance with principle of the current invention comprising: a first device  310  comprising four bidirectional PHYs  320 ; a second device  330  comprising four bidirectional PHYs  320 ; and a physical transmission medium  60 , illustrated as an unshielded twisted pair cable comprising four twisted wire pairs  70 . For clarity, a first twisted wire pair  70  is labeled pair A, second twisted wire pair  70  is labeled pair B, a third twisted wire pair  70  is labeled pair C and a fourth twisted wire pair  70  is labeled pair D.  
         [0038]     A first bidirectional PHY  320  of first device  310  is connected via twisted wire pair  70 -A to first bidirectional PHY  320  of second device  330 . A second bidirectional PHY  320  of first device  310  is connected via twisted wire pair  70 -B to second bidirectional PHY  320  of second device  330 . A third bidirectional PHY  320  of first device  310  is connected via twisted wire pair  70 -C to third bidirectional PHY  320  of second device  330 . A fourth bidirectional PHY  320  of first device  310  is connected via twisted wire pair  70 -D to fourth bidirectional PHY  320  of second device  330 . Thus, four bidirectional communication links are formed between first device  310  and second device  330  comprising respective twisted wire pairs  70 -A, B,C and D.  
         [0039]     In an exemplary embodiment as described in the above standard, a first end of twisted wire pair  70 -A is connected to contacts  1  and  2  of the medium dependent interface (MDI) of first device  310  and a second end of twisted wire pair  70 -A is respectively connected to contacts  3  and  6  of the MDI of second device  330 . A first end of twisted wire pair  70 -B is connected to contacts  1  and  2  of the MDI of second device  330  and a second end of twisted wire pair  70 -B is respectively connected to contacts  3  and  6  of the MDI of first device  310 . A first end of twisted wire pair  70 -C is connected to contacts  4  and  5  of the MDI of first device  310  and a second end of twisted wire pair  70 -C is respectively connected to contacts  7  and  8  of the MDI of first device  310 . A first end of twisted wire pair  70 -D is connected to contacts  4  and  5  of the MDI of second device  330  and a second end of twisted wire pair  70 -D is respectively connected to contacts  7  and  8  of the MDI of first device  310 .  
         [0040]     In operation, system  300  first attempts auto-negotiation on the auto-negotiation communication path comprising twisted wire pairs  70  A, B. In the event that auto-negotiation is successful, communication is enabled in accordance with advertised enhance modes of operation. In a preferred embodiment known to the prior art, in the event that gigabit Ethernet is advertised by both first device  310  and second device  330  the communication path comprising twisted wire pairs  70  C, D are tested to confirm that operation according to gigabit Ethernet is possible. In the event that the communication path comprising twisted wire pairs  70  C, D does not provide communication, operation according to 100 Mb/s or alternatively 10 Mb/s is enabled along the communication path comprising twisted wire pairs  70  A, B.  
         [0041]     In the event that auto-negotiation on twisted wire pairs  70  A, B fails, auto-negotiation is attempted in accordance with the principle of the current invention on twisted wire pairs  70  C, D. In another embodiment in accordance with the principle of the current invention auto-negotiation is attempted on both twisted wire pairs  70  A, B and twisted wire pairs  70  C, D. Such a second, or parallel, auto-negotiation is advantageous in that capabilities are recognized at a single auto-negotiation phase. Additionally, any problems or errors on twisted wire pairs  70  C, D are detected in this manner. In the event that auto-negotiation on twisted wire pairs  70  C, D is successful and auto-negotiation on twisted wire pairs  70  A, B is not successful, operation according to 100 Mb/s or alternatively 10 Mb/s is enabled along the communication path comprising twisted wire pairs  70  C, D. It is to be understood that operation according to 100 Mb/s or alternatively 10 Mb/s is enabled according to protocols supported by both first and second devices  310 ,  330 .  
         [0042]     It is a feature of the current invention that communication at 100 Mb/s or alternatively 10 Mb/s is enabled along the communication path comprising twisted wire pairs  70  C, D due to the existence of bidirectional PHY  320  connected thereto. Thus, in contrast to system  100  of  FIG. 1 , auto-negotiation and communication at 10 Mb/s or alternatively 100 Mb/s is enabled along the communication path comprising twisted wire pairs  70  C, D.  
         [0043]      FIG. 5  illustrates a high level flow chart of the method of operation according to a first embodiment of the principle of the current invention. In stage  1000  auto-negotiation is attempted on the communication path comprising twisted wire pairs  70  A, B. In stage  1010  the auto-negotiation of stage  1000  is examined to see if it was successful at 1000 Mb/s. In the event that in stage  1010  the auto-negotiation of stage  1000  was determined to be successful at 1000 Mb/s, in stage  1020  communication at 1000 Mb/s utilizing twisted wire pairs  70  A, B, C, D is enabled.  
         [0044]     In the event that in stage  1010  the auto-negotiation of stage  1000  was determined not to be successful at 1000 Mb/s, in stage  1030  the auto-negotiation of stage  1000  is examined to determine if communication at 100 Mb/s or alternatively at 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  A, B. In the event that in stage  1030  the auto-negotiation of stage  1000  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  A, B, in stage  1040  communication at 100 Mb/s or alternatively 10 Mb/s is enabled on the communication path comprising twisted wire pairs  70  A, B.  
         [0045]     In the event that in stage  1030  the auto-negotiation of stage  1000  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is not possible on the communication path comprising twisted wire pairs  70  A, B, in stage  1050  auto-negotiation on the communication path comprising twisted wire pairs  70  C, D is attempted at 100 Mb/s or alternatively 10 Mb/s. In stage  1060  the auto-negotiation of stage  1050  is examined to determine if communication at 100 Mb/s or alternatively at 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  C, D. In the event that in stage  1060  the auto-negotiation of stage  1050  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  C, D, in stage  1070  communication at 100 Mb/s or alternatively 10 Mb/s is enabled on the communication path comprising twisted wire pairs  70  C, D. In the event that in stage  1060  the auto-negotiation of stage  1050  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is not possible on the communication path comprising twisted wire pairs  70  C, D, in stage  1080  a failure of communication is flagged.  
         [0046]      FIG. 6  illustrates a high level flow chart of the method of operation according to a second embodiment of the principle of the current invention. In stage  2000  auto-negotiation is attempted on the communication path comprising twisted wire pairs  70  A, B. In stage  2010  auto-negotiation is attempted on the communication path comprising twisted wire pairs  70  C, D. In stage  2020  the auto-negotiation of stage  2000  is examined to see if it was successful at 1000 Mb/s. In the event that in stage  2020  the auto-negotiation of stage  2000  was determined to be successful at 1000 Mb/s, in stage  2030  communication at 1000 Mb/s utilizing twisted wire pairs  70  A, B, C, D is enabled.  
         [0047]     In the event that in stage  2020  the auto-negotiation of stage  2000  was determined not to be successful at 1000 Mb/s, in stage  2040  the auto-negotiation of stage  2000  is examined to determine if communication at 100 Mb/s or alternatively at 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  A, B. In the event that in stage  2040  the auto-negotiation of stage  2000  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  A, B, in stage  2050  communication at 100 Mb/s or alternatively 10 Mb/s is enabled on the communication path comprising twisted wire pairs  70  A, B.  
         [0048]     In the event that in stage  2040  the auto-negotiation of stage  2000  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is not possible on the communication path comprising twisted wire pairs  70  A, B, in stage  2060  the auto-negotiation of stage  2010  on the communication path comprising twisted wire pairs  70  C, D is examined to determine if communication at 100 Mb/s or alternatively at 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  C, D. In the event that in stage  2060  the auto-negotiation of stage  2010  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is possible on the communication path comprising twisted wire pairs  70  C, D, in stage  2070  communication at 100 Mb/s or alternatively 10 Mb/s is enabled on the communication path comprising twisted wire pairs  70  C, D. In the event that in stage  2060  the auto-negotiation of stage  2010  is determined to indicate that communication at 100 Mb/s or alternatively 10 Mb/s is not possible on the communication path comprising twisted wire pairs  70  C, D, in stage  2080  a failure of communication is flagged.  
         [0049]     In the event of a failure of ongoing communication at 1000 Mb/s, preferably auto-negotiation in accordance with either the method of  FIG. 5  or  FIG. 6  is attempted to reestablish communication.  
         [0050]     The present embodiments thus enable auto-negotiation on the communication path comprising pairs A and B, and in the event of a failure of auto-negotiation on the communication path comprising pairs A and B, auto-negotiation on the communication path comprising pairs C and D. In the event that auto-negotiation is successful on the communication path comprising pairs C and D and not successful on the communication path comprising pairs A and B, communication at 100 Mb/s or alternatively at 10 Mb/s is enabled on the communication path comprising pairs C and D.  
         [0051]     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.  
         [0052]     Unless otherwise defined, all technical and scientific terms used herein have the same meanings as are commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods are described herein.  
         [0053]     All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the patent specification, including definitions, will prevail. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.  
         [0054]     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.