Abstract:
In one aspect a system and method for providing communication between Ethernet and frame relay routers includes generating a unique media access control (MAC) address for a frame relay router in communication with an Ethernet router, associating the MAC address with the frame relay router, and storing the MAC address in an interworking function device (IWF). The method also includes receiving at the IWF device an address resolution protocol (ARP) request from the Ethernet router and sending from the IWF device to the Ethernet router a response to the ARP request based on the stored MAC addresses.

Description:
BACKGROUND  
       [0001]     Ethernet and frame relay networks operate using different standards and protocols. Ethernet is a local area technology, in which devices attach to a common medium that provides a path along which the signals will travel. Frame relay networks are based on packet-switching technology. In order for an Ethernet network to communicate with a frame relay network an intermediate device (e.g., a device to encapsulate a package) is needed. Encapsulation is the inclusion of one data structure within another structure so that the first data structure is hidden and the network views the encapsulated packet to forward in the system. For example, an Ethernet formatted data packet can be encapsulated within asynchronous transfer mode (ATM) cells to allow packets to be forwarded from an Ethernet network to an ATM network.  
       SUMMARY  
       [0002]     In one aspect a system and method provides communication between Ethernet and a second router having another protocol. The system and method includes generating a unique media access control (MAC) address for the second router in communication with an Ethernet router, associating the MAC address with the second router, and storing the MAC address. The system and method also includes receiving an address resolution protocol (ARP) request from the Ethernet router; and sending to the Ethernet router a response to the ARP request based on the stored MAC addresses.  
         [0003]     Embodiments can include one or more of the following. The second router is a frame relay router or an ATM router. The method can include forwarding a packet to the frame relay router from the Ethernet router based on the response from the IWF device.  
         [0004]     The method can include sending an inverse address resolution protocol request upon an addition of a new frame relay router. The interworking function device can provide a transparent proxy between the Ethernet router and the frame relay router. The method can include having a virtual socket interface connected to the Ethernet router. The virtual socket interface can be included in the interworking function device and can read the virtual MAC addresses of the frame relay routers.  
         [0005]     In another aspect, a system includes a connection to one or more frame relay routers and a connection to an Ethernet router. The system also includes a memory that includes a virtual MAC address for the one or more frame relay routers in communication with the Ethernet router, the device configured to enable the Ethernet router to send data to the frame relay router based on the virtual MAC address.  
         [0006]     Embodiments can include one or more of the following. The system can be configured to receive ARP requests from the Ethernet router. The system can be configured to respond to APR requests based on the virtual MAC addresses.  
         [0007]     In another aspect, a method includes sending an ARP request from an Ethernet router and receiving a response to the request from an interworking function device. The response is based on a MAC address for a frame relay router stored in the interworking function device. The method also includes forwarding the packet to the frame relay router based on the response.  
         [0008]     Embodiments can include one or more of the following. The method can also include generating a unique media access control (MAC) address for the frame relay router connected to the Ethernet router and associating the MAC address with the frame relay router. The method can also include sending an inverse address resolution protocol request upon the addition of a new frame relay router. The interworking function device can provide a transparent proxy between the Ethernet router and the frame relay router.  
         [0009]     In another aspect a computer program product, is tangibly embodied in an information carrier, for executing instructions on a processor. The computer program product is operable to cause a machine to generate a unique media access control (MAC) address for a frame relay router connected to an Ethernet router, associate the MAC address with the frame relay router, and store the MAC address in an interworking function device (IWF). The product is also configured to receive at the IWF device an address resolution protocol (ARP) request from the Ethernet router and send from the IWF device to the Ethernet router a response to the ARP request based on the stored MAC addresses.  
         [0010]     Embodiments can include one or more of the following. The method can include forwarding a packet to a frame relay router from the Ethernet router based on the response from the interworking function device. The method can include sending an inverse address resolution protocol request upon the addition of a new frame relay router. The interworking function device can provide a transparent proxy between the Ethernet router and the frame relay router.  
         [0011]     In one aspect, the interworking function (IWF) device allows transparent communication between an Ethernet network and a frame relay network. The IWF device stores a list of media access control addresses for each frame relay connection and responds to ARP requests of the Ethernet network. This allows the Ethernet network to send packets to systems on the frame relay network without first encapsulating the packets.  
         [0012]     In another aspect, the assignment of “Virtual” MAC address per ATM/FR virtual connection means that just one Ethernet identifier (VLAN or Ethernet MPLS Pseudo-wire) is required towards the Ethernet “Headquarter” for a set of ATM/FR virtual connections. This translates can provide one or more of the advantages that follow. This method can allow optimized migration to Ethernet for certain types of existing ATM/FR VPNs, for example, where the enterprise customer point router based in the Hub site employs Group Mode/Point to Multipoint configurations. This also can allow lower operational expenses for a both service provider and enterprise customers subscribing to this service. The system can include increased scalability and stability in the Ethernet portion of the network. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0013]      FIG. 1  is a diagram of a system including Ethernet and frame relay networks.  
         [0014]      FIG. 2  is a diagram of an interworking device and connections to Ethernet and frame relay networks.  
         [0015]      FIG. 3  is a diagram of address resolution protocol requests.  
         [0016]      FIG. 4  is a flow chart of a process to send a packet to a system in the frame relay network.  
         [0017]      FIG. 5  is a flow chart of processing after addition of a new frame relay connection. 
     
    
     DESCRIPTION  
       [0018]     Referring to  FIG. 1 , a network  10  includes an Ethernet based network  20  and a frame relay based network  30  connected by an interworking function (IWF) device  24 . The Ethernet based network  20  includes, for example, a headquarter site  22  having one or more Ethernet capable routers that communicate with multiple frame relay based or asynchronous transfer mode (ATM) based customer end (CE) routers. The CE routers could be located at various customer end locations  32 ,  34 , and  36  and included in the frame relay network  30 .  
         [0019]     The Ethernet routers, for example, the multiple routers included in the headquarter site  22 , communicate using the specified IEEE 802.3 standard. Ethernet is a local area technology with networks traditionally operating within a close proximity. In an Ethernet network, devices attach to a common medium that provides a path along which the signals will travel. This medium can be been coaxial copper cable, a twisted pair, fiber optic cabling, and the like. Devices that attach to the common medium are referred to as stations or nodes. The stations or nodes communicate using short messages called frames, which are variably sized chunks of information. The Ethernet protocol specifies a set of rules for constructing frames. There are explicit minimum and maximum lengths for frames, and a set of required information that appears in the frame. Each frame includes, for example, both a destination address and a source address, which identify the recipient and the sender of the message. The address uniquely identifies the node and no two Ethernet devices should have the same address.  
         [0020]     The example below is discussed in terms of a Frame Relay network but the IWF principles also apply for an ATM network.  
         [0021]     The frame relay network  30  in system  10  is a type of point-to-point network based on packet-switching technology. In a High-level Data Link Control (HDLC) frame relay network, data is sent in HDLC packets, referred to as “frames”. In a frame relay network, all circuits (e.g., link between user end points) are permanently assigned and referred to as “permanent virtual circuits”. The circuits are known as virtual because they are not electrical circuits where there is a direct electrical connection from end to end. Rather, there is a “logical” connection, or virtual connection, where the data moves from end-to-end, but without a direct electrical circuit. In practice, data from a particular host arrives at the frame relay switch, from the customer equipment, with a particular destination address. The frame relay switch, using its internal lookup table, finds the data a physical port associated with the address and delivers the data to the correct location.  
         [0022]     As described above, the Ethernet Router on customer premises (building  22 ) is directly connected to the IWF. Similarly, the Routers on the frame relay side are directly connected to the IWF. However, in both cases, in between the device containing the IWF and the customer locations (either on the Ethernet or FR/ATM side) one may use different transport services/method to carry to carry the Ethernet or FR/ATM packets/cells. An example of such a transport service could be Multi-Protocol Label Switching (MPLS) services: i.e. “Martini/PWE3” pseudowires.  
         [0023]     Referring to  FIG. 2 , an example of a system  10  including an Ethernet network  20  and a frame relay network  30  with an IWF device  24  functioning as an interface between the Ethernet network  20  and frame relay network  30  is shown. The Ethernet network includes a network  40  connected to a port  42 . The IWF device  24  connects port  42  to multiple frame relay ports  56 ,  58 , and  60  for frame relay networks  62 ,  64 , and  66 .  
         [0024]     Interfaces from the customer end devices in the frame relay network  30  terminate into the IWF device  24 . Each port (e.g., ports  56 ,  58 , and  60 ) is assigned a virtual media access control (MAC) address. MAC addresses are used by Ethernet networks to route packets from one location to another. The virtual MAC addresses for each device are stored in a cache  46  in the IWF device  24 . For example, network  62  (connected to port  56 ) is assigned a MAC address  50  of “A3”. Networks  64  and  66  are assigned MAC addresses  52  and  54  of “A1” and “A5” respectively. Inverse ARP requests towards the FR CPE are used (as described in  FIG. 6 .) to learn the IP addresses from the related CPE Routers which are subsequently mapped to the corresponding MAC addresses assigned by the system (A1 to A5).  
         [0025]     Referring to  FIG. 3 , the system uses address resolution protocol (ARP) requests to map Internet Protocol address (IP address) to a physical machine address that is recognized in the network. The physical machine address is also known as a Media Access Control or MAC address. A table, usually called the ARP cache  46 , maintains a mapping between each MAC address and its corresponding IP address. ARP provides the protocol rules for making the mapping and providing address conversion in both directions.  
         [0026]     Referring to  FIG. 4 , when the Ethernet network  20  desires to send a packet to a system in the frame relay network  30 , an ARP request  80  is generated  102  and sent  104  to the IWF device  24 . The IWF device  24  finds  106  a physical host or MAC address that matches the IP address by looking up the physical host or MAC address in the ARP cache  46 . The MAC addresses are associated with the frame relay devices and are stored in cache  46 . The IWF  24  device searches the cache  46  and if an matching entry is found returns  108  the entry. This entry is based on the virtual MAC addresses available to the IWF device  24  in cache  46 . Since the IWF device  24  responds to the ARP request  80  in the same manner as a port on the Ethernet would respond, the Ethernet network  20  communicates with the IWF device  24  and is not aware that the packets are being sent to a frame relay network  30 .  
         [0027]     Referring to  FIG. 5 , upon addition of a new frame relay connection  88 , an inverse ARP request  86  is sent  122  from the IWF device  24  to the new frame relay device. This inverse ARP request  86  identifies  124  the IP address of the remote end (e.g., frame relay connection  88 ). Upon the addition of the new frame relay connection  88 , the IWF device  24  updates  126  cache  46  to include the assigned MAC address for the new port.  
         [0028]     The device described herein can be implemented in digital electronic circuitry, in computer hardware, firmware, software, or in combinations of them. The device described herein can be implemented as a computer program product, e.g., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, data processing apparatus, e.g., a processing device, a computer, or multiple computers. A computer program can be written in any form of programming language, including compiled, assembled, or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.  
         [0029]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.