Abstract:
An apparatus comprising a node that uses a set of determined virtual local area network (VLAN) identifier (VIDs) to provide a hop limit for a packet forwarded by the node in a network. Also disclosed is a network component comprising a receiver that receives a packet comprising a VID that belongs to a determined set of ordered VIDs, a processor that substitutes the VID in the packet from the set of ordered VIDs and maps the VID to a next hop or instead drops the VID if the VID is a last ordered VID of the ordered VIDs, and a transmitter that forwards the packet comprising the substituted VID to the mapped next hop.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND 
       [0004]    Modern communications and data networks are comprised of nodes that transport data through the network. The nodes may include routers, switches, bridges, or combinations thereof that transport the individual data packets or frames through the network. Some networks may offer data services that forward data frames or packets from one node to another node across the network without using pre-configured routes on intermediate nodes. Other networks may forward the data frames or packets from one node to another node across the network along pre-configured or pre-established paths. The packets forwarded in the network may be unicast packets that are transmitted to a plurality of nodes via a plurality of corresponding point-to-point (P2P) links. Alternatively, the packets forwarded in the network may be multicast packets that are transmitted to a plurality of nodes via a point-to-multipoint (P2MP) link or a tree. 
       SUMMARY 
       [0005]    In one embodiment, the disclosure includes an apparatus comprising one or more nodes that uses a set of determined virtual local area network (VLAN) identifier (VIDs) to provide a hop limit for a packet forwarded by the node in a network. 
         [0006]    In another embodiment, the disclosure includes a network component comprising a receiver that receives a packet comprising a VID that belongs to a determined set of ordered VIDs, a component or sub-component that substitutes the VID in the packet from the set of ordered VIDs and maps the packet comprising the VID to a next hop or instead drops the VID if the VID is a last ordered VID of the ordered VIDs, and a transmitter that forwards the packet comprising the substituted VID to the mapped next hop. 
         [0007]    In a yet another embodiment, the disclosure includes a computer program product in a computer readable media comprising first instructions executable by a processor for receiving using a receiver a packet comprising a VID, second instructions executable by a processor for matching the VID in the received packet to a forwarding instance identifier (FID) that determines, with other elements of the packet, a next hop for forwarding the packet, third instructions executable by a processor for substituting the VID with a next ordered VID in the determined set of ordered VIDs, fourth instructions executable by a processor for forwarding the packet comprising the next ordered VID to the next hop, and fifth instructions executable by a processor for dropping the packet if the VID corresponds to a last ordered VID in a determined set of ordered VIDs. 
         [0008]    These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
           [0010]      FIG. 1  is a schematic diagram of an embodiment of a VID mapping scenario. 
           [0011]      FIG. 2  is a schematic diagram of an embodiment of a VID substitution scenario. 
           [0012]      FIG. 3  is a schematic diagram of an embodiment of a VID forwarding scenario. 
           [0013]      FIG. 4  is a flowchart of an embodiment of a loop control forwarding method. 
           [0014]      FIG. 5  is a schematic diagram of an embodiment of a network unit. 
           [0015]      FIG. 6  is a schematic diagram of an embodiment of a general-purpose computer system. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
         [0017]    Some packet forwarding schemes, e.g., unicast and multicast schemes, may cause forwarding loops, which may reduce networking efficiencies and waste resources. Previous and current methods to prevent forwarding loops include Spanning Tree Protocols (STPs) that use relatively complex control plane logic to avoid creating data paths that loop, and the Institute of Electrical and Electronics Engineers (IEEE) 802.1aq standard and the Internet Engineering Task Force (IETF) Transparent Interconnect of Lots of Links (TRILL) protocols, which use reverse path forwarding to suppress multicast loops. The methods also include Internet Protocol (IP) and TRILL/Multiprotocol Label Switching (MPLS), which use a bit field time to live (TTL) that is hop-wise decremented (by one) and stops looping packets when it reaches zero. Another current method is the IEEE 802.1Qbp standard protocol that introduces a new tag with a TTL for loop prevention to Media Access Control (MAC)-in-MAC frames. Such schemes may be relatively complex, require adding new fields, and/or require new hardware. 
         [0018]    Disclosed herein is a system and method for preventing packet forwarding loops using VID substitution as a means of implementing a TTL mechanisms in a packet based network. The VID substitution scheme may be used in networks, where VID encapsulation may be implemented as part of a tunneling mechanism. The VID may be substituted or swapped at each next hop in the network and hence the packet may be dropped after a selected number of hops to prevent an infinite unicast or multicast loop. Using VID substitution may not require adding a new field to the packet and may be implemented using relatively simple control plane logic and current or available network equipment/hardware. 
         [0019]    The system and method may use a set of VIDs (VID values) that may be ordered in a determined sequence, e.g., from largest to smallest value. The order or sequence of VIDs may be known to the network or the forwarding nodes (hops) in the network. When a packet is initially encapsulated, the first VID in the set (e.g., the largest VID) may be used. When the packet is forwarded by forwarding nodes, the VID may be swapped at each hop with the next VID in the order (e.g., the next smaller value). When the VID reaches the last ordered value in the set (e.g., the smallest value) at a hop before reaching the packet&#39;s destination, then the packet may be dropped. The forwarding logic may treat all the VIDs (except the last ordered VID) in the ordered set similarly by mapping the VIDs to the same FID at each hop. The FID may be used in combination with other fields in the packet to determine on which port or link to forward the packet (after properly swapping the VID). 
         [0020]      FIG. 1  illustrates an embodiment of a VID mapping scenario  100 , which may be used for the VID substitution scheme (as a TTL mechanism) to prevent loops. The scheme may be implemented in a network that comprises a plurality of nodes  110 . The nodes  110  may be any nodes, devices, or components configured to receive, transmit, and/or forward packets associated with the network. The nodes  110  may be coupled to each other via a plurality of links, which may include wired (fixed) and/or wireless links. The packets may be Ethernet packets, e.g., forwarded at the data link layer or layer 2 (L2) of the Open Systems Interconnection (OSI) model, and/or any other type of packets, e.g., MAC frames, IP packets, etc. The network may be an Ethernet network or any other network that transfer data in the form of packets, frames, or other encapsulated or tunneled data. The network may also be any network that does not support using a TTL field for preventing loops, such as some optical based networks. The nodes  110  may be located in a backbone of the network. The backbone portion may extend from an ingress or source node  110  (node S) to an egress or destination node  110  (node D). The source node  110  may be coupled to a plurality of sources (labeled s 1  to sn), which may be nodes or other components that transmit packets, e.g., into the network or the backbone portion of the network. The destination node  110  may be coupled to a plurality of destinations (labeled d 1  to dn), which may be nodes or other components that receive the packets, e.g., from the network or the backbone portion of the network. 
         [0021]    In the VID mapping scenario  100 , a set of VIDs, such as Backbone VIDs (B-VIDs), may be reserved in the network, e.g., where the size of the set may greater than an expected diameter of the network. The size of the set may be determined by the number of the reserved VIDs in the set. The number of the reserved VIDs may determine the maximum number of hops (nodes) permitted to forward the same packet. The packet may be dropped when the maximum number of hops is reached before delivering the packet to its destination. The VIDs (or B-VIDs) in the set may be ordered according to a determined sequence and may be swapped at each next hop according to that sequence until reaching the maximum number of hops with the last ordered VID in the sequence. For instance, the VIDs may be ordered from a largest value to a smallest value. The largest value may be initially used in the forwarded packet and then swapped by the next smaller value in the set at each next hop (node  110 ) until the smallest value is reached. If the smallest value is reached before delivering the packet to its destination, then the packet may be discarded and dropped. In another implementation, the VIDs may be ordered from a smallest value to a largest value, where the current value in the packet may be swapped with next larger value in the set at each next hop until the largest value is reached. In other embodiments, any other selected sequence of values may be used, e.g., according to an order or sequence list that may be used for reference. 
         [0022]    To support the VID substitution scheme, the nodes  110  may use a plurality of tables (or other data structures) for processing the VIDs properly, including a VID-to-FID mapping table  120  and a L2 forwarding table  130 , e.g., a forwarding information base (FIB). Each node  110  may comprise a corresponding group of such tables. The VID-to-FID mapping table  120  may map all the reserved VIDs (of the determined ordered set) to the same FID, which may be used (instead of the VIDs), with other fields in the packet, to determine the next hop for the packet. The L2 forwarding table  130  may be used to map the FID (associated with all the reserved VIDs) with other fields in the packet to the next hop, and hence the corresponding port/link. 
         [0023]    The VID mapping scenario  100  shows a node  110  (node A) comprising the VID-to-FID table  120  and the L2 forwarding table  130 . The VID-to-FID table  120  may map the reserved VIDs (e.g., that have values V0 to V8) to the same FID (e.g., that has a value F1). The L2 forwarding table  130  may map that same FID value (e.g., F1), with other fields in the packet, to two ports associated with two corresponding nodes  110  (nodes D and C). Node C may be a next hop of node A, and node D may be an egress node of the backbone portion of the network. The egress node may be the destination of the packet or may be coupled to the destination of the packet, e.g., one of the destinations d 1  to dn. Specifically, the node  110  (e.g., node A) may receive a packet and detect the VID in the packet. The node  110  may then map that VID to the FID using the VID-to-FID mapping table  120 . The node  110  may then use the L2 forwarding table  130 , with other fields in the packet, to determine the next hop (e.g., node C) that is associated with that FID, and hence properly forward the packet (e.g., at the L2 level) to the next hop. 
         [0024]      FIG. 2  illustrates an embodiment of a VID substitution scenario  200 , which may be used with the VID mapping scenario  100  to prevent loops in the network. In the VID substitution scenario  200 , the nodes  110  may use an egress logic component or process to swap the VID in the packet according to the pre-determined order of the set of VIDs, before forwarding the packet. For instance, the node  110  may comprise an egress mapping table  240  that may be used to map each VID value in the set to a next ordered VID value in the sequence. The VID substitution scenario  200  shows the node A comprising the egress mapping table  240  (with the VID-to-FID table  120  and the L2 forwarding table  130 ). The egress mapping table  240  may indicate the substitution mapping between the reserved VIDs. For example, the largest value V8 is mapped to the next largest value V7, and similarly V7 is mapped to V6 . . . and V1 to V0. Since V0 may be the smallest value, V0 may not be mapped in the egress mapping table  240  and instead the packet comprising V0 may be dropped. This VID (or B-VID) mapping may be represented as VIDn→ 4 VIDn−1 (or B-VIDn  4 →B-VIDn−1). 
         [0025]      FIG. 3  illustrates an embodiment of a VID forwarding scenario  300 , which may be used with the VID mapping scenario  100  and the VID substitution scenario  200  to prevent (unicast and multicast) loops in the network. In the VID forwarding scenario  300 , the nodes  110  may use the VID-to-FID table  120 , the L2 forwarding table  130 , and the egress logic (the egress mapping table  240 ) to determine the next hop for forwarding the packet, substitute or drop the VID in the packet, and forward the substituted packet accordingly. The VID forwarding scenario  300  shows the processing and handling of the packet and VIDs at the node A. Specifically, the node A may receive on a first port or interface (e.g., interface  3  (if/ 3 )) an incoming packet  352 , which may comprise a destination address (D), a source address (S), and one of the VIDs (e.g., V7). The node A may then find a match for the VID in the VID-to-FID table  120  to obtain a FID for forwarding the packet. The node A may then use the obtained FID to find a match in the L2 forwarding table  130 , with the packet&#39;s destination address (D), that indicates a next hop (e.g., node C) for forwarding the packet. 
         [0026]    Before attempting to forward the packet, the node A may check if the VID corresponds to the last ordered VID (V0) in the set of VIDs. If this is true, then the node A may drop the packet and may not forward the packet. However, in the scenario  300 , the received VID corresponds to V7 and not V0. Thus, the node A may instead use the received VID (V7) to find a match (e.g., V6) in the egress mapping table  240  for substituting the VID. The node A may then forward an outgoing packet  354  corresponding to the incoming packet  252  and comprising the matched VID (V6) to the next hop (node C), as indicated in the L2 forwarding table  130 . The packet may be forwarded at L2. The node A may check if the VID is the last ordered VID before or after mapping the FID in the L2 forwarding table  130  and before or after attempting to substitute the VID using the egress mapping table  240 . 
         [0027]      FIG. 4  illustrates an embodiment of a loop control forwarding method  400  that may be implemented in the packet forwarding scenarios above, e.g., by any of the nodes  110 . The node  110  may implement the method  400  using hardware, software, or both. The loop control forwarding method  400  may begin at block  410 , where a packet comprising a VID (or a B-VID) may be received. The VID (e.g., a B-VID) in the packet may be one of a plurality of reserved VIDs in a set of ordered VIDs, e.g., from the largest to the lowest value. At block  420 , the VID in the received packet may be matched to a FID that, with other fields in the packet, determines a next hop for forwarding the packet. For instance, the VID may be matched to the FID using the VID-to-FID mapping table  120  or a comparable data structure. The next hop may then be determined using the FID, the packets destination field, and the table L2 forwarding table  130  or a comparable data structure, as described above. 
         [0028]    At block  430 , the method  400  may determine whether the VID is the last ordered VID in the set of ordered VIDs. If the condition of block  440  is true, then the method may proceed to block  440 . Otherwise, the method  400  may proceed to block  450 . At block  440 , the packet may be dropped. The method  400  may then end. At block  450 , the VID in the packet may be substituted with the next ordered VID. The VID may be substituted by mapping the VID to a next ordered VID using a mapping table or list. Alternatively, the VID value may be changed according to a mapping logic or equation, such as by decreasing (or increasing) the VID value by some determine amount, such as one (as described in the scenario  300 ). At block  460 , the packet comprising the next ordered VID may be forwarded to the next hop. The method  400  may then end. In another embodiment, the block  430  may be implemented before the block  420 , where the method may determine whether the received VID is the last ordered VID in the set before matching the VID in the received packet to a FID. The method  400  may limit the number of hops that forward a packet and thus prevent loops, for instance in a network that uses tunnel encapsulation and forwarding of unicast and/or multicast packets. Further, the number of hops may be limited without using reserved TTL bits and without adding a TTL logic to hardware, such as a Broadcom (BCM) chip. 
         [0029]      FIG. 5  illustrates an embodiment of a network unit  500 , which may be any device that transports packets through a network. For instance, the network unit  500  may correspond to any of the nodes  110  in the scenarios above. The network unit  500  may comprise one or more ingress ports  510  coupled to a receiver  512  (Rx), which may be configured for receiving packets or frames, objects, options, and/or Type Length Values (TLVs) from other network components. The network unit  500  may comprise a logic unit or processor  520  coupled to the receiver  512  and configured to process the packets or otherwise determine to which network components to send the packets. The logic unit or processor  520  may be implemented using hardware, software, or both. The network unit  500  may also comprise one or more egress ports  530  coupled to a transmitter  532  (Tx), which may be configured for transmitting packets or frames, objects, options, and/or TLVs to other network components. The logic unit or processor  520 , the receiver  512 , and the transmitter  532  may also be configured to implement or support any of the schemes and methods described above (the method  400 ). 
         [0030]    The network components and/or methods described above may be implemented on any general-purpose network component, such as a computer or network component with sufficient processing power, memory resources, and network throughput capability to handle the necessary workload placed upon it.  FIG. 6  illustrates a typical, general-purpose network component  600  suitable for implementing one or more embodiments of the components disclosed herein. The network component  600  includes a processor  602  (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage  604 , read only memory (ROM)  606 , random access memory (RAM)  608 , input/output (I/O) devices  610 , and network connectivity devices  612 . The processor  602  may be implemented as one or more CPU chips, or may be part of one or more application specific integrated circuits (ASICs) and/or digital signal processors (DSPs). 
         [0031]    The secondary storage  604  is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM  608  is not large enough to hold all working data. Secondary storage  604  may be used to store programs that are loaded into RAM  608  when such programs are selected for execution. The ROM  606  is used to store instructions and perhaps data that are read during program execution. ROM  606  is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of secondary storage  604 . The RAM  608  is used to store volatile data and perhaps to store instructions. Access to both ROM  606  and RAM  608  is typically faster than to second storage  604 . 
         [0032]    The second storage  604  is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM  608  is not large enough to hold all working data. Second storage  604  may be used to store programs that are loaded into RAM  608  when such programs are selected for execution. The ROM  606  is used to store instructions and perhaps data that are read during program execution. ROM  606  is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of second storage  604 . The RAM  608  is used to store volatile data and perhaps to store instructions. Access to both ROM  606  and RAM  608  is typically faster than to second storage  604 . 
         [0033]    At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, R 1 , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R 1 +k*(R u −R 1 ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 7 percent, . . . , 70 percent, 71 percent, 72 percent, . . . , 97 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. 
         [0034]    Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. The discussion of a reference in the disclosure is not an admission that it is prior art, especially any reference that has a publication date after the priority date of this application. The disclosure of all patents, patent applications, and publications cited in the disclosure are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to the disclosure. 
         [0035]    While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. 
         [0036]    In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.