Abstract:
The present invention is an apparatus for multi-level loopback test in a community network system and method therefor, in which a loopback test device is installed between an Ethernet switch in a community and a central office so that the loopback test device can be utilized by network management system in central office to perform a three-level loopback test on the community network system to easily obtain the information of whether there is a fault between central office and loopback test device, whether the connection of Ethernet switch is good, and whether loopback test device operates normally.

Description:
FIELD OF THE INVENTION 
   The present invention relates to network and more particularly to an apparatus for multi-level loopback test in a community network system and method therefor. 
   BACKGROUND OF THE INVENTION 
   In recent years, Internet has been widely employed worldwide. In particular, the World Wide Web (WWW) of Internet can provide voice, graphics, and multimedia services in addition to e-mail transmission and receiving. Hence, people can access a variety of information from WWW. Further, many people take log-on the Internet as a daily work. For accommodating such trend, a variety of high speed network devices have been provided by network equipment manufacturers. Such devices comprise cable modem, asymmetric digital subscriber line (ADSL) modem, etc. Moreover, various associated network peripherals are provided by network equipment manufacturers for enhancing the functionality of network. Such peripherals comprise voice over IP device (VoIP), etc. User can employ VoIP to communicate with a remote user over the Internet so as to greatly reduce long distance or international telecommunication charge. 
   Conventionally, a UTP (Unshielded Twisted Pair) based network architecture is selected from a variety of existing network architectures and is widely employed in a community network system as shown in  FIG. 1 . Each Ethernet adapter  30  at user comprises an ADSL (Asynchronous Digital Subscriber Line) communication interface (not shown) and a router control circuit (not shown). Ethernet adapter  30  is electrically coupled to an Ethernet equipment (not shown) in central office (or network system communication provider)  34  through router control circuit, UTP based telephone line  31 , Ethernet switch  32  of central office  34  installed in a community, and optical fiber  33 . The Ethernet equipment is in turn coupled to the Internet  35  through optical fiber  33 . Hence, packets from Ethernet adapters  30  can be transmitted to the Internet  35 . Alternatively, packets from the Internet  35  can be received by Ethernet adapters  30 . In above network architecture, for example, packets originated from central office  34  are transmitted to each of a certain number of users in community through the high speed optical fiber  33 , Ethernet switch  32 , and an existing telephone line  31  of each user. As a result, the data transmission of each user is much improved in terms of speed. 
   In the above mentioned FTTH (Fiber To The Home) or ETTH (Ethernet To The Home) application, there is a long distance between Ethernet switch  32  and central office  34 . Hence, network is utilized to perform the same. Further, it is impossible to perform a real tim online maintenance and management on Ethernet switch  32  by central office  34  because a SNMP (Simple Network Management Protocel) being employed by most network management systems only has limited application. When the system fails, a loopback test is typically conducted to detect which component is malfunctioned. During the loopback test, network management system installed in central office  34  is responsible to issue at least one Ping instruction. Ethernet switch  32  then may reply to the Ping instruction as it receives the same. Hence, network management system can determine that Ethernet switch  32  fails if there is no reply of the Ping instruction from ethernet switch  32  within a predetermined period of time. In other words, the only technique employed by network management system is to issue a Ping instruction to Ethernet switch  32  for determining whether there is a malfunction from the presence of reply. As to the special problem such as line disconnection, or software in Ethernet switch  32  not normally running, or any other, there is no information about that. Moreover, after network management system has issued a Ping instruction, a good reply means that both hardware and associated software operate normally. Otherwise, it is impossible of obtaining a good reply as well as correctly determining the nature of the fail. For solving the problem, it is typical to assign employees to the site of Ethernet switch  32  to perform a manual maintenance and management. It is disadvantageous because maintenance and management is poor, cost is high, and communication quality is degraded. Thus, a need for improvement exists. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an apparatus for multi-level loopback test in a community network system and method therefor in which a loopback test device is installed between an Ethernet switch in a community and a central office so that the loopback test device can be utilized by network management system in central office to perform a three-level loopback test on the community network system. By utilizing this, it is possible to easily obtain the information of whether there is a fault between central office and loopback test device, whether the connection of Ethernet switch is good, and whether loopback test device operates normally. Hence, the invention has the advantages of no need to assign employees to the site of Ethernet switch to perform a manual maintenance and management, lower cost, and to improve communication quality. 
   The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  presents schematically the connection of components of network architecture implemented in a conventional UTP based network architecture; 
       FIG. 2  presents schematically the connection of components of community network system according to the invention; 
       FIG. 3  is a block diagram of Ethernet switch, loopback test device, and central office of  FIG. 2 ; 
       FIG. 4  depicts a format of a special BPDU (Bridge Protocol Data Unit) packet issued by network management system during a first level of loopback test according to the invention; 
       FIG. 5  depicts a format of a reply packet by loopback test device during a first level of loopback test according to the invention; 
       FIG. 6  depicts a format of a special BPDU (Bridge Protocol Data Unit) packet issued by network management system during a second level of loopback test according to the invention; and 
       FIG. 7  is a flow chart illustrating network management system in central office how to utilize loopback test device to perform a loopback test on community network system according to a preferred embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 2 , there is shown a typical UTP based network architecture. As shown, each user  40  is coupled to an Ethernet switch  42  through an existing telephone line  41 . Ethernet switch  42  is coupled to central office  44  and the Internet  45  sequentially through optical fiber  43 . Hence, packets from users  40  can be transmitted to the Internet  45 . Alternatively, packets from the Internet  35  can be received by users  40 . The invention installs a loopback test device  46  between Ethernet switch  42  in a community and central office  44 . Referring to  FIG. 3 , loopback test device  46  comprises an Ethernet control circuit  461 , a packet transmission and receiving control circuit  462 , and at least two I/O ports  463  and  464 . Ethernet control circuit  461  is implemented as an FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit). Ethernet control circuit  461  acts to perform loopback test, packet generation, and packet reply. Packet transmission and receiving control circuit  462  is coupled to Ethernet control circuit  461 . I/O port  463  is coupled between Ethernet switch  42  and Ethernet control circuit  461 , while I/O port  464  is coupled between central office  44  and Ethernet control circuit  461 . Therefore, it provides a mechanism needed for I/O ports  463  and  464  to be operated normally and for a variety of inter conversion or buffer to be operated in a full or half duplex mode. 
   In the invention, central office  44  utilizes loopback test device  46  to conduct a loopback test on community network system in which the loopback test comprises three levels. First level of loopback test acts to determine whether there is a hardware fail between network management system in central office  44  and loopback test device  46 , and between network management system in central office  44  and Ethernet switch  42 . In detail, network management system issues at least one special BPDU packet each having a format as shown in  FIG. 4 . When Ethernet control circuit  461  of loopback test device  46  receives at least one special BPDU packet, Ethernet control circuit  461  will operate to send the same to packet transmission and receiving control circuit  462 . In response, packet transmission and receiving control circuit  462  changes a source address of BPDU packet into a special source address which is in turn sent back to network management system in central office  44  via Ethernet control circuit  461 . The invention fills the reply packet with status information of I/O port  463  coupled to Ethernet switch  42 . The status information comprises speed of I/O port  463 , full or half duplex, and link status. Hence, network management system in central office  44  can determine whether the line is faulty or not after reply packet has been received. For example, the line is faulty if there is no reply after a predetermined period of time has lapsed. Further, network management system in central office  44  can determine whether I/O port  463  is normally coupled to Ethernet switch  42  in community. The complete format of reply packet is shown in  FIG. 5 . 
   Second level of loopback test of the invention acts to determine whether there is a fail between loopback test device  46  and Ethernet switch  42  in community. In detail, network management system issues at least one special BPDU packet each having a format as shown in  FIG. 6 . When Ethernet control circuit  461  of loopback test device  46  receives a special BPDU packet for enabling a loopback test mode, packet transmission and receiving control circuit  462  will command Ethernet control circuit  461  to enable I/O port  463  coupled to the Ethernet switch  42  in the community enter into the loopback test mode. Hence, all packets sent to I/O port  463  from network management system in central office  44  are sent back to network management system in central office  44  without having any change, resulting in a completion of loopback test. After the completion of loopback test, network management system in central office  44  will issue one (or more) special BPDU packet to finish the loopback test mode. When Ethernet control circuit  461  of loopback test device  46  receives the special BPDU packet, packet transmission and receiving control circuit  462  will command Ethernet control circuit  461  to enable I/O port  463  coupled to the Ethernet switch  42  in the community enter into a normal mode. 
   Third level of loopback test of the invention acts to utilize a well known Ping instruction to determine whether there is a hardware and/or software fail between network management system in central office  44  and Ethernet switch  42  in community. The test procedure is well known. Thus a detailed description thereof is omitted herein for the sake of brevity. 
   Referring to  FIG. 3 , there is shown a flow chart illustrating network management system in central office  44  how to utilize loopback test device  46  to perform a loopback test on community network system according to a preferred embodiment of the invention. There are three levels of loopback test involved in the community network system as detailed below. 
   In first level of loopback test (step  10 ), network management system issues at least one special BPDU packet. Then it is determined whether a reply packet has been received from loopback test device  46  within a predetermined period of time. If yes, then it is determined whether information contained in the reply packet shows that I/O port  463  is normally coupled to Ethernet switch  42  in community. If yes, it means that first level of loopback test is a success, process goes to step  13 . Otherwise, process goes to step  11 . 
   In step  11 , it is determined whether a reply packet has been received. If yes and process further determines that I/O port  463  is not normally coupled to Ethernet switch  42  in community, process goes to step  12 . Otherwise, if there is no reply packet from loopback test device  46  within a predetermined period of time, it means that there is a disconnection between network management system in central office  44  and loopback test device  46 . 
   In step  12 , second level of loopback test is performed in which network management system in central office  44  issues at least one special BPDU packet. Then it is determined whether all packets sent to I/O port  463  from network management system in central office  44  are sent back to network management system in central office  44  without having any change. If yes, it means that there is a disconnection between loopback test device  46  and Ethernet switch  42  in community or the Ethernet switch  42  in the community is faulty. Otherwise, if not all packets sent to I/O port  463  from network management system in central office  44  are sent back to network management system in central office  44 , it means that loopback test device  46  itself is faulty. 
   In step  13 , third level of loopback test is performed in which network management system in central office  44  issues at least one Ping instruction and then further determine whether there is a reply from Ethernet switch  42  in community (which has already received the Ping instruction) within a predetermined period of time. If yes, it means that community network system operates normally. Otherwise, it means that there is a software fail in Ethernet switch  42 . 
   In view of above, network management system of the invention can easily obtain the following information of whether there is a fault between central office and loopback test device, whether the connection of Ethernet switch in community is good, and whether loopback test device operates normally. Hence, the invention has the advantages of no need to assign employees to the site of Ethernet switch to perform a manual maintenance and management, lower cost, and to improve communication quality. 
   While the invention has been described by means of special embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.