Patent Publication Number: US-7715409-B2

Title: Method and system for data link layer address classification

Description:
FIELD OF INVENTION 
     The present invention relates to the field of network devices. Specifically, the present invention relates to a method and system for data link layer address classification. 
     BACKGROUND OF THE INVENTION 
     Until recently, all hosts coupled to a network device over a local area network (LAN) on the same Ethernet were assigned to the same routing domain. For example, in a network device supporting Internet protocol version 4 (IPv4), the network device only had to maintain a single routing information base (RIB), also referred to as a routing table, and a single Address Resolution Protocol (ARP) lookup table. 
     Recent technological advances in the field of data routing has provided applications where hosts coupled to a network device over a LAN on the same Ethernet can be partitioned into different domains. In other words, the LAN can be logically partitioned into a number of domains based on the IP address. The domains may also be referred to as virtual private network (VPN) routing/forwarding (VRFs). In order to support the proper routing of packets in this configuration, the network device maintains a separate routing table for each domain. 
     In order for devices coupled to a LAN to communicate with the network device, a mapping between the LAN (e.g., data link layer) and the network device (e.g., the network layer) is required. An ARP lookup table provides this mapping. However, where the LAN is logically partitioned into multiple domains, ARP packets are currently assigned to a default domain of the network device. The default domain may not accurately reflect which domain the ARP information should belong to. Accordingly, a need exists for a method and/or system for assigning the ARP information to the proper domain in a LAN logically partitioned into multiple domains. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention: 
         FIG. 1  is a block diagram of an exemplary computer system platform upon which embodiments of the present invention may be practiced. 
         FIG. 2  is a block diagram of one embodiment of a local area network (LAN) upon which embodiments of the present invention may be practiced. 
         FIG. 3  is a block diagram illustrating an exemplary routing data structure of a network device, in accordance with one embodiment of the present invention. 
         FIG. 4  is a flow chart illustrating a method for data link layer address classification, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and the scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, structures and devices have not been described in detail so as to avoid unnecessarily obscuring aspects of the present invention. 
     Various embodiments of the present invention, a method and system for data link layer address classification, are described herein. Embodiments of the present invention provide for receiving data link layer address information from a device over a local area network (LAN), wherein the LAN is partitioned into a plurality of domains. In one embodiment, the data link layer address information is Address Resolution Protocol (ARP) information. The data link layer address information is classified as being associated with a domain of the plurality of domains based on a source address of the device. In one embodiment, the source address is an Internet protocol (IP) address. The data link layer address information is assigned to the domain. 
     Some portions of the detailed descriptions which follow are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here and generally conceived to be a self-consistent sequence of steps of instructions leading to a desired result. The steps are those requiring physical manipulations of data representing physical quantities to achieve tangible and useful results. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “receiving”, “classifying”, “assigning”, “storing”, “determining”, “transmitting”, “executing”, or the like, refer to the actions and processes of a computer system or similar electronic computing device (e.g., a network device). The computer system or similar electronic device manipulates and transforms data represented as electronic quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices. 
     Refer now to  FIG. 1  that illustrates an exemplary computer system  100  upon which embodiments of the present invention may be practiced. In one embodiment, computer system  100  is a network device (e.g., network device  230  of  FIG. 2 ), such as a router. In general, computer system  100  comprises bus  110  for communicating information, processor  101  coupled with bus  110  for processing information and instructions, random access (volatile) memory (RAM)  102  coupled with bus  110  for storing information and instructions for processor  101 , read-only (non-volatile) memory (ROM)  103  coupled with bus  110  for storing static information and instructions for processor  101 , data storage device  104  such as a magnetic or optical disk and disk drive coupled with bus  110  for storing information and instructions. 
     In one embodiment, computer system  100  comprises an optional user output device such as display device  105  coupled to bus  110  for displaying information to the computer user, an optional user input device such as alphanumeric input device  106  including alphanumeric and function keys coupled to bus  110  for communicating information and command selections to processor  101 , and an optional user input device such as cursor control device  107  coupled to bus  110  for communicating user input information and command selections to processor  101 . Furthermore, an optional input/output (I/O) device  108  is used to couple computer system  100  onto, for example, a network. 
     Display device  105  utilized with computer system  100  may be a liquid crystal device, cathode ray tube, or other display device suitable for creating graphic images and alphanumeric characters recognizable to the user. Cursor control device  107  allows the computer user to dynamically signal the two-dimensional movement of a visible symbol (pointer) on a display screen of display device  105 . Many implementations of the cursor control device are known in the art including a trackball, mouse, joystick or special keys on alphanumeric input device  106  capable of signaling movement of a given direction or manner of displacement. It is to be appreciated that the cursor control  107  also may be directed and/or activated via input from the keyboard using special keys and key sequence commands. Alternatively, the cursor may be directed and/or activated via input from a number of specially adapted cursor directing devices. 
       FIG. 2  is a block diagram of one embodiment of a local area network (LAN)  200  upon which embodiments of the present invention may be practiced. LAN  200  includes network device  230  communicatively coupled to a plurality of hosts  212   a ,  212   b ,  212   n ,  222   a ,  222   b  and  222   n  over interface  225 . In one embodiment, network device  230  is a router. It should be appreciated that the hosts may include any type of computing device, including but not limited to: desktop computer systems, laptop computer systems, personal digital assistants, cellular telephones, and the like. 
     Network device  230  is operable to be logically partitioned into a plurality of domains. The domains may also be referred to as virtual private network (VPN) routing/forwarding (VRFs) herein. As shown, network device  230  is partitioned into two domains  210  and  220 . Domain  210  includes hosts  212   a ,  212   b  and  212   n . Domain  220  includes hosts  222   a ,  222   b  and  222   n . It should be appreciated that network device  230  may be partitioned into any number of domains and that a domain may include any number of hosts, and that the present invention is not limited to the shown embodiment. In one embodiment, each domain of the plurality of domains is associated with a different IP subnet of the LAN. 
     Referring still to  FIG. 2 , LAN  200  includes well-known network technologies. For example, LAN  200  can be implemented using Ethernet, Fiber Distributed Data Interface (FDDI), or other wired or wireless network technologies. Network device  230  is coupled to distributed computer network  240  over at least one communication link  235 . It should be appreciated that network device  230  may be coupled to distributed computer network  240  over any number of communication links (e.g., communication links  235   a ,  235   b  and  235   c ). Communications links  235   a ,  235   b  and  235   c  may be implemented using, for example, a telephone circuit, communications cable, optical cable, wireless link, or the like. It should be appreciated that distributed computer network  240  may be any type of network, including but not limited to: an intranet, the Internet, or the like. 
     As described above, LAN  200  is partitioned into a plurality of domains (VRFs)  210  and  220 . Since incoming packets received over interface  225  may not be assigned to the default domain associated with interface  225 , it is necessary to provide a mechanism for classifying data link layer information, according to a domain of the plurality of domains. It should be appreciated that the data link layer refers to layer  2  of the OSI protocol stack. In one embodiment, the data link layer information is a media access control (MAC) address. The following embodiments of the present invention are described according to the IP version 4 (IPv4) standard, where the data link layer information is Address Resolution Protocol (ARP) information transmitted in an ARP packet. However, it should be appreciated that embodiments of the present invention may be implemented using other standards where the data link layer information provides a mapping between the data link layer and the network layer. For example, other standards upon which embodiments of the present invention may be implemented include, but are not limited to: IPv6, as well as proprietary routing protocols. 
     Connected routes of interface  225  can be associated with an alternative domain which is different to the domain of interface  225 . When this association is made, it triggers the building of a lookup table for ARP information for the domain. In this lookup table, each entry provides the mapping from the source information of the packet into a domain. During a database search, either an IPv4 network/subnet or an IPv4 address in place of the IPv4 prefix are received. When an ARP packet is received on interface  225 , the source (e.g., a host), which is identified by an IPv4 address, is used together with the ingress for a search of the lookup table. If the search is successful, it yields a domain, and the ARP address is assigned to the domain. The ARP information learned from this packet is hence assigned to that domain, and stored in the ARP lookup table for that domain. Alternatively, if the search fails, the ARP information is stored in the ARP lookup table of the default domain associated with the interface. 
       FIG. 3  is a block diagram illustrating an exemplary routing data structure  300  of a network device (e.g., network device  230  of  FIG. 2 ), in accordance with one embodiment of the present invention. As described above, the network device of the present invention is operable to be logically partitioned into a plurality of domains. These domains are shown in  FIG. 3  as domains  310  and  320 . Each domain has an associated routing information base (RIB), e.g., RIB  312  and RIB  322 , that includes the information for routing packets. Moreover, each domain also has an associated ARP lookup table, e.g., ARP lookup table  314  and ARP lookup table  324 . 
     An ARP lookup table provides a mapping between the addressable devices of a LAN and the network layer, such that packets for transmission to a particular device are received at the intended device. Since the network device of the present invention may be logically partitioned into different domains, it is necessary to maintain separate ARP lookup tables for each domain. It should be appreciated that the ARP lookup tables of the described invention may be maintained with one physical table. However, in order to provide efficient and easily manageable ARP classification, the ARP lookup tables are logically separate according to domain. By logically separating the ARP lookup tables according to domain, the present invention avoids the duplication of data and is easier to dynamically update. 
       FIG. 4  is a flow chart illustrating a method  400  for data link layer address classification, in accordance with one embodiment of the present invention. In one embodiment, process  400  is carried out by processors and electrical components under the control of computer readable and computer executable instructions. The computer readable and computer executable instructions reside, for example, in data storage features such as computer usable volatile and non-volatile memory (e.g., volatile memory  102  and non-volatile memory  103  of  FIG. 1 ). However, the computer readable and computer executable instructions may reside in any type of computer readable medium. Although specific steps are disclosed in process  400 , such steps are exemplary. That is, the embodiments of the present invention are well suited to performing various other steps or variations of the steps recited in  FIG. 4 . In one embodiment, process  400  is performed by network device  230  of  FIG. 2 . 
     At step  410  of method  400 , a data link layer address information request is transmitted to a device (e.g., a host) over a LAN. The LAN is logically partitioned into a plurality of domains. In one embodiment, the request is transmitted to learn the data link address of the device. In another embodiment, the request is transmitted periodically to refresh the ARP information. In one embodiment, a link layer address information request is an ARP information request transmitted in an ARP packet. It should be appreciated that step  410  is optional. 
     At step  420 , data link layer address information is received from the device over the LAN and includes a source address of the device. In one embodiment, the data link layer address information is comprised within an ARP packet. In one embodiment, the ARP packet is sent in response to the request as described at step  410 . In another embodiment, the ARP packet is sent gratuitously. In one embodiment, each domain of the plurality of domains is associated with a different IP subnet of the LAN. 
     At step  430 , it is determined whether the source address is associated with a domain of the plurality of domains. If the source address is associated with a particular domain of the plurality of domains, as shown at step  440 , the data link layer address information is classified as being associated with the particular domain. Alternatively, if the source address is not associated with a domain of the plurality of domains, as shown at step  450 , the data link layer address information is classified as being associated with a default domain of the plurality of domains. 
     At step  460 , the data link layer address information is assigned to the appropriate domain. In one embodiment, the data link layer address information is stored in a data link layer address lookup table associated with the domain (e.g., ARP lookup table  314  of  FIG. 3 ). 
     The described embodiments of the present invention provide a system and method for data link layer address classification (e.g., ARP classification). By assigning the data link layer address information to the correct domain, the described embodiments provide for efficient data link layer address lookup. Moreover, since the data link layer address information is stored according to domain, there is no need to duplicate information across all domains. The described embodiments describe a method and system for classifying data link layer information according to domains in a network device supporting multiple domains on a single LAN. 
     Various embodiments of the present invention, a system and method for data link layer address classification, are thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.