Abstract:
A system for emulating a distributed network includes a localized network operable to emulate a distributed network. A network device is coupled to the localized network and operable to be accessed over the localized network. A test site is operable to couple a test device to the localized network and to test the ability of the test device to access the network device over the localized network.

Description:
RELATED APPLICATIONS 
     This application is related to copending U.S. patent application Ser. No. 09/129,199 entitled “METHOD AND SYSTEM FOR AUTOMATIC LINE PROTECTION SWITCHING OF EMBEDDED CHANNELS,” filed Aug. 4, 1998 by inventor, Javid (nmi) Jabbarnezhad and U.S. patent application Ser. No. 09/129,585 entitled “METHOD AND SYSTEM FOR REMOTE MANAGEMENT OF EQUIPMENT HAVING DUPLICATE NETWORK ADDRESSES,” filed Aug. 4, 1998, by inventor Javid (nmi) Jabbarnezhad. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates generally to the field of data communication networks, and more particularly to a system and method for emulating a distributed network. 
     BACKGROUND OF THE INVENTION 
     With the move toward decentralized processing, users have interconnected workstations, computers and other types of local equipment through local area networks (LANs). More recently, as users move toward global communications that allow equipment to appear as if it were attached to the local network, local area networks have been interconnected through wide area networks (WANs) such as the Internet. 
     A consequence of wide area networks is that network equipment needs to be able to communicate and provide services over the multiple interconnections of the wide area networks. Testing of network equipment for such operability is generally expensive due to the distributed nature of the wide area network and ineffective due to the inability to sufficiently control conditions on the wide area network. As a result, equipment is typically not fully tested or demonstrated prior to deployment. Instead, vendors engage customers in highly technical discussions to explain how equipment or services will operate. Such discussions are time consuming and expensive for vendors to staff conduct. In addition, without full testing, customers cannot be assured that the equipment will operate as promised or that services will provide a promised benefit. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a system and method for testing. equipment in a network environment are provided that substantially eliminate or reduce disadvantages or problems associated with previously developed systems and methods. In particular, the present invention provides a system and method for emulating a distributed network to allow full testing and demonstration of equipment in a network environment prior to deployment. 
     In one embodiment of the present invention, a system for emulating a distributed network includes a localized network operable to emulate a distributed network. A network device is coupled to the localized network and operable to be accessed over the localized network. A test site is operable to couple a test device to the localized network and to test the ability of the test device to access the network device over the localized network. 
     More specifically, in accordance with a particular embodiment of the present invention, the localized network includes a plurality of routers interconnected to each other to form disparate multiple-router transmission paths between the test site and the network device. The localized network may also include a telephony switch. In this embodiment, the test site is operable to couple the test device to the telephony switch and operable to test the ability of the test device to access the network device through the telephony switch. The network may be a frame relay network and the telephony switch a private branch exchange (PBX). 
     Technical advantages of the present invention include providing an improved system and method for testing equipment for a network environment. In particular, a localized network emulates a distributed network to allow functions and features of equipment to be fully tested and demonstrated. In addition, because a network is localized, the testing may be efficiently conducted in a production laboratory or other highly controlled environment. 
     Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts, in which: 
     FIG. 1 is a schematic block diagram illustrating a production laboratory having a localized network for testing equipment in accordance with one embodiment of the present invention; 
     FIG. 2 is a schematic block diagram illustrating primary and secondary embedded channels for transmission links of the localized network of FIG. 1; and 
     FIG. 3 is a flow diagram illustrating a method of automatic line protection switching between the primary and secondary embedded channels of the transmission links of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a production laboratory  10  for testing equipment for a distributed network environment. Referring to FIG. 1, the production laboratory  10  includes a localized network  12 , a plurality of device sites  14 , a plurality of test sites  16 , and a management site  18  each coupled to the localized network  12 . 
     The network  12  is localized in that it is not geographically distributed. Preferably, the localized network  12  is contained at least substantially within a single complex, structure, facility, or space. This allows all equipment used in the testing process to be located at that single location and testing to be fully completed at that location. As a result, testing need not be coordinated between multiple locations which is both time consuming and costly. 
     The localized network  12  is preferably dedicated carrying test traffic and thus need not accommodate other nontest traffic. This allows conditions on the localized network  12  to be completely controlled and optimized for equipment testing. 
     The localized network  12  emulates a distributed network, such as a wide area network interconnecting geographically distributed local area networks. For the embodiment of FIG. 1, the localized network  12  is a frame relay network. The frame relay network uses a packet-switching protocol for connections between remote locations. The packets are in the form of frames which are variable in length. An advantage to the frame relay for a distributed network is that data packets of various sizes associated with virtually any native data protocol can be accommodated. As a result, the frame relay network is protocol independent because it does not undertake a lengthy protocol conversion process and offers fast and less expensive switching and/or routing. 
     The frame relay network includes a plurality of routers  20 , a plurality of transmission links  22  interconnecting the routers  20 , and a telephony switch  24 . The routers  20  forward traffic according to network-level addresses, using information that the routers  20  exchange among themselves to find the best transmission path between network segments. In one embodiment, as described in more detail below, each transmission link  22  includes primary and secondary embedded channels defined in a network trunk. In this embodiment, the routers  20  provide automatic line protection switching between the primary and embedded channels. The network trunk may be a T 1  line and the embedded channels may be private virtual channels (PVC). 
     The transmission links  22  interconnect the routers  20  to form a plurality of multiple-router transmission paths. The multiple-router transmission paths each route traffic through two or more routers  20  to provide multiple routes of a distributed network in the localized network  12 . Provision of the plurality of such multiple-router transmission paths provide alternative paths of a distributed network in the localized network  12 . 
     For the embodiment of FIG. 1, a first router  30  is connected to a second router  32  by a transmission link  34  and to a third router  36  by a transmission link  38 . The second and third routers  32  and  36  are connected to a fourth router  40  by transmission links  42  and  44 , respectively. A fifth router  46  is connected to the fourth router  40  by a transmission link  48 . In this embodiment, for example, traffic may be routed from router  30  to router  40  via router  32  on transmission links  34  and  42  or may alternatively be routed via router  36  on transmission links  38  and  44 . 
     The telephony switch  24  is connected to the routers  20  and select test sites  16  through telephony links  50 . For the embodiment of FIG. 1, the telephony switch  24  is a private branch exchange (PBX) and the telephony links  50  are twisted pair lines. Inclusion of the PBX or other telephone switch  24  allows the localized network  12  to test equipment for applications in which the equipment is connected to a distributed network through a telephony switch, a distributed network utilizes a telephony switch for back-up communications, and telephony traffic is switched to a wide area network for reduced transmission costs. 
     The device sites  14  each include a local area network  60  and one or more network devices  62 . The local area network connects the network devices  62  to a router  20  of the localized network  12 . The local area network  60  may be an Ethernet or other suitable type of local network. 
     The network devices  62  are used in the production lab  10  to test the ability of test devices installed at the test sites  16  to access equipment over the localized network  12 . The network devices  62  are customer premise equipment (CPE) or other types of equipment capable of being accessed over the localized network  12 . The network devices  62  each include a network address  64  with which the device  62  can be accessed. In one embodiment, the network address  64  is an Internet Protocol (IP) address. The Internet Protocol address is a 32-bit address that includes a network portion and a host portion for efficient routing. 
     For the embodiment of FIG. 1, a first device site  70  is connected to the first router  30 , a second device site  72  is connected to the second router  32 , a third device site  74  is connected to the third router  36 , a fourth device site  76  is connected to the fourth router  40  and a fifth device site  78  is connected to the fifth router  46 . This multiplicity of device sites  14  allows equipment to be tested for operability with disparate types of network devices  62  at disparate points of the localized network  12 . 
     The test sites  16  each include a test device  80 , a local area network  82 , and a traffic generator  84 . The test device  80  is a device being tested for deployment in a distributed network. The test device  80  may be a router, a communications service unit, a data service unit, or other type of device designed for deployment in a network environment. 
     The local area network may be an Ethernet or other suitable type of local network. The traffic generator  84  provides traffic addressed to the network devices  62  to the test devices  80  in order to test the ability of the test devices  80  to access the network devices  62  over the localized network  12 . As previously discussed, the network devices  62  include a network address  64  with which the network devices  62  can be accessed by test devices  80 . 
     The test devices  80  include a network address  86  to allow the test devices  80  to be accessed and configured by the management station  18 . The network addresses  86  also allow the network devices  62  to respond to the test devices  80 . In one embodiment, the network address  86  is an Internet Protocol (IP) address. The Internet Protocol address is a 32-bit address that includes a network portion and a host portion for efficient routing. 
     For the embodiment of FIG. 1, a first test site  90  connects a first test device  92  to the first router  30 , a second test site  94  connects a second test device  96  to the first router  30 , and a third test site  98  connects a third test device  100  to the first router  30 . In this embodiment, the first test device  92  is a frame relay with router (FRAD) device, the second test device is another frame relay with router (FRAD) device and the third device is a communications service unit (CSU) or a data service unit (DSU). Accordingly, a plurality of disparate test devices  80  may be connected to the localized network  12  and simultaneously tested in connection with disparate types of network devices  62  using the production laboratory  10 . 
     The management site  18  includes a local area network  110  and a management station  112 . The local area network  110  connects the management station  112  to the localized network  12 . The local area network  110  may be an Ethernet or other suitable local network. 
     The management station  112  is a workstation or other suitable device operable to configure the network devices  62  and the test devices  80  and to monitor the testing of features and functions of the test devices  80 . Accordingly, the test devices  80  are connected, configured, tested and monitored at a single location. Moreover, the testing includes testing the ability of the test devices  80  to access the various types of network devices  62  through multiple route and alternate paths of the localized network  12  and through the telephony switch  24  initially or as a backup transmission path. Accordingly, the features and functions of the test devices  80  may be fully demonstrated and problems identified. 
     FIG. 2 illustrates details of the transmission links  22 . The transmission links  22  are configured to match or simulate those of a distributed network. For the embodiment of FIG. 2, the transmission links  22  each include a pair of network trunks  120 . A primary embedded channel  122  and a secondary embedded channel  124  are defined in each pair of network trunks  120 . The network trunks  120  may be T 1  lines and the embedded channels  122  and  124  may be private virtual channels (PVC). The private virtual channels  122  and  124  provide what appears to be dedicated lines without the cost associated with such lines. In accordance with private virtual channel standards, data is transmitted in accordance with backward and forward congestion protocols. 
     The primary private virtual channels  122  carry traffic between the test sites  16  and the device sites  14  in normal operation. The secondary private virtual channels  124  carry the traffic in the event of a fault condition on the primary embedded channels  122 . Thus, in accordance with operations of a distributed network, communications are maintained in the localized network  12  even in the presence of a fault on a transmission link  22 . 
     FIG. 3 illustrates a method of automatic line protection switching between the primary and secondary private virtual channels  122  and  124  of the localized network  12 . The automatic line protection switching preferably matches or simulates that of a distributed network. For the localized network  12 , the method is independently conducted by the routers  20  at each end of the primary and secondary private virtual channels  122  and  124 . As a result, the routers  20  independently switch between the primary and secondary private virtual channels  122  and  124  in unison and without the communication of private virtual channel fault messages. 
     Referring to FIG. 3, in a normal state  130  traffic is transmitted and received between transmit and receive routers  20  via the primary private virtual channel  122 . In the normal state  130 , each router  20  independently monitors a check sum value (CRC) of the primary private virtual channel  122 . When a check sum value for the primary private virtual channel  122  is received, state  130  leads to step  132 . At step  132 , the router  20  determines a bit error rate (BER) for the primary private virtual channel  122  based on the check sum value for the channel  122 . Next, at decisional step  134 , the router  20  determines if the bit error rate is below 10 −6 . If the bit error rate is not below 10 −6 , then the NO branch of decisional step  134  returns to normal state  130 . If the bit error rate is below 10 −6 , then a fault condition exists on the primary private virtual channel  122  and the YES branch of decisional step  134  leads to step  136 . At step  136 , the router  20  switches from the primary private virtual channel  122  to the secondary private virtual channel  124 . Step  136  leads to fault state  138  in which traffic is transmitted and received via the secondary private virtual channel  124 . 
     Returning to normal state  130 , each router  20  also independently monitors the bit error rate of the network trunk  120 . The bit error rate may be independently determined by each router  20  based on a check sum value or may be provided in accordance with trunk transmission protocol. In response to receiving the bit error rate of the network trunk  120 , state  130  leads to decisional step  140 . At decisional step  140 , the router  20  determines if the bit error rate for the network trunk  120  is below 10 −6 . If the bit error rate is not below 10 −6 , the NO branch of decisional step  140  returns to normal state  130 . If the bit error rate of the network trunk  120  is below 10 −6 , a fault condition exists on the network trunk  120  and the YES branch of decisional step  140  leads to step  136 . At step  136 , as previously described, the router  20  switches from the primary private virtual channel  122  to the secondary private virtual channel  124 . Next, at the fault state  138 , traffic is transmitted and received via the secondary private virtual channel  124 . 
     In the default state  138 , each router  20  continues to monitor the network trunk  120  and the primary private virtual channel  122  for a non fault condition. In response to receiving a bit error rate for the network trunk  120  carrying the primary private virtual channel  122 , fault state  136  leads to decisional step  142 . At decisional step  142 , the router  20  determines if the bit error rate for the network trunk  120  is above 10 −4 . If the bit error rate is not above 10 −4 , then a fault condition continues to exist within the network trunk  120  and the NO branch of decisional step  142  returns to fault state  138 . If the bit error rate of the network trunk  120  is above 10 −4 , then a non fault condition exits in the network trunk  120  and the YES branch of decisional branch  142  leads to step  144 . 
     At step  144 , the router  20  receives a check sum value for the primary private virtual channel  122 . Proceeding to step  146 , the router  20  determines the bit error rate for the primary private virtual channel  122  based on the check sum value. Next, at step  148 , the router  20  determines if the bit error rate for the primary private virtual channel  122  is above 10 −4 . If the bit error rate for the primary private virtual channel  122  is not above 10 −4 , then a fault condition continues to exist in the primary private virtual channel  122  and the NO branch of decisional step  148  returns to the fault state  138 . If the bit error rate of the primary private virtual channel  122  is above 10 −4 , then a non fault condition exists in the primary private virtual channel  122  and the YES branch of decisional step  148  leads to step  150 . At step  150 , the router  20  switches from the secondary primary private virtual channel  124  to the primary private virtual channel  122 . Step  150  leads to normal state  130  in which traffic is transmitted and received on the primary private virtual channel  122 . 
     Thus, each router independently and in unison switches between the primary and secondary private virtual channels  122  and  124  in response to the same fault and non fault conditions. The fault and non fault conditions may be any suitable condition of the network trunk and/or private virtual or other embedded channel that can be obtained or determined by the nodes. In this way, automatic line protection switching of a distributed network is provided for the localized network  12 . 
     Although the present invention has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.