Abstract:
A network component comprising at least one processor configured to implement a method comprising transparently snooping a path control message comprising a first path identifier, wherein the path control message is sent between a plurality of routers and is not intended for the network component, analyzing a plurality of frames each comprising a second path identifier, and diverting at least some of the frames away from at least one of the routers, wherein the second path identifier in the diverted frames matches the first path identifier. Included is a method comprising configuring a bypass path by snooping a control frame comprising a label switched path (LSP) identifier, and routing a plurality of data frames associated with the LSP identifier to the bypass path without routing any subsequent control frames associated with the LSP identifier to the bypass path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 61/048,396, filed Apr. 28, 2008 by Linda Dunbar et al., and entitled “Transparent By-Pass and the Mechanisms to Enable It,” which is incorporated herein by reference as if reproduced in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND 
     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 from one node to another node across the network without using pre-configured routes on intermediate nodes. Other networks may forward the data frames from one node to another node across the network along pre-configured or pre-established paths. 
     Bypasses, such as express bypasses, are sometimes used in packet networks to create a direct path between two nodes when the traffic volume between the two nodes exceeds certain capacity. For example, when traffic volume between two Provider Edge (PE) nodes is close to a capacity limit, an express bypass can be created between the two PE nodes to reduce switching burden on the intermediate (or transit) nodes in the middle of the network. Unfortunately, bypasses change the topology of the network and can lead to undesirable changes in routing behavior within the network. 
     SUMMARY 
     In one embodiment, the disclosure includes a network component comprising at least one processor configured to implement a method comprising transparently snooping a path control message comprising a first path identifier, wherein the path control message is sent between a plurality of routers and is not intended for the network component, analyzing a plurality of frames each comprising a second path identifier, and diverting at least some of the frames away from at least one of the routers, wherein the second path identifier in the diverted frames matches the first path identifier. 
     In another embodiment, the disclosure includes a system comprising a packet-aware transport box configured to establish and tear down a transparent bypass for a data path managed by a router by snooping on the data path&#39;s path control messages, snoop a plurality of frames associated with the data path and intended for the router, determine whether at least some of the frames should bypass the router, and forward any frames that should bypass the router to the transparent bypass, wherein the forwarding does not substantially impact the condition of the data path. 
     In a third embodiment, the disclosure includes a method comprising configuring a bypass path by snooping a control frame comprising a label switched path (LSP) identifier, and routing a plurality of data frames associated with the LSP identifier to the bypass path without routing any subsequent control frames associated with the LSP identifier to the bypass path. 
     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 
       For a more complete understanding of the present 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. 
         FIG. 1  is a schematic diagram of an embodiment of a core network implementing express bypass. 
         FIG. 2  is a schematic diagram of an embodiment of a core network implementing transparent bypass. 
         FIG. 3  is a schematic diagram of another embodiment of a network implementing transparent bypass. 
         FIG. 4  is a schematic diagram of an embodiment of a method for establishing transparent bypass. 
         FIG. 5  is a schematic diagram of an embodiment of a general-purpose network component. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Disclosed herein is a method for allowing routers to handle an increased volume of traffic without upgrading router&#39;s capacity. Specifically, a transparent bypass method is disclosed wherein packet-aware transport boxes associated with the routers snoop the control messages processed by the router to determine the paths that traverse the router. The packet-aware transport boxes build a table of associated paths and snoop the router&#39;s incoming data frames to determine whether any of the incoming data frames are associated with the paths in the table. Any data frames associated with the paths in the table are not sent to the router but are instead forwarded by the packet-aware transport boxes to another destination, such as the next node on the path. In contrast, the packet-aware transport box forwards all control frames to the router, regardless of whether they are associated with the paths in the table or not. By doing so, the routers are able to maintain the paths in a normal fashion, but experience a reduced volume of data frames. 
       FIG. 1  illustrates an embodiment of a network  100 . The network may comprise a plurality of provider edges (PEs)  102   a - 102   h  (collectively,  102 ), a plurality of core routers (CRs)  104   a - 104   d  (collectively,  104 ), and a plurality of transport boxes  106   a - 106   d  (collectively,  106 ). The PEs  102  may be coupled to the CRs  104  as shown by the single solid lines in  FIG. 1 , while the CRs  104  may be coupled to each other as shown by the double solid lines in  FIG. 1 . The communications paths between the PEs  102  and the CRs  104  (including those between the CRs  104 ) may be electrical or optical communications paths. Typically, the communications paths between the CRs  104  have more capacity than the communications paths between the PEs  102  and the CRs  104 . For example, the communications paths between the CRs  104  may be wavelength division multiplexed to create a capacity of about 200 gigabits per second (Gbps or G), while the communications paths between the PEs  102  and the CRs  104  may only be single wavelength channels having a capacity of about 10 Gbps. 
     The network  100  may be any communications system that may be used to transport data between PEs  102  and/or CRs  104 . For example, the network  100  may be a wireline network or an optical network, such as a backbone, a provider, and an access networks. Such networks typically implement Synchronous Optical Networking (SONET), Synchronous Digital Hierarchy (SDH), Ethernet, Internet Protocol (IP), Asynchronous Transfer Mode (ATM), Frame Relay, optical transport network (OTN) or other protocols. Alternatively, the network  100  may be a wireless network. The network  100  may transport traffic using multi-protocol label switching (MPLS) LSPs, Ethernet Switched Paths (ESPs), and/or virtual local area networks (VLANs). The traffic may comprise connectionless or switched traffic, also referred to as service instances or non-TE traffic. The traffic may also comprise connection-oriented, also referred to as traffic engineered (TE) traffic. Each of the standards described herein is incorporated herein by reference. 
     The PEs  102  may be any devices, components, or networks that exchange data with the CRs  104 . The PEs  102  may be routers, switches, or bridges, and may include provider core bridges (PCBs) and/or provider edge bridges (PEBs). The PEs  102  may implement one or more protocols, including MPLS, open shortest path first (OSPF), or border gateway protocol (BGP). The PEs  102  may establish MPLS LSPs with other devices, and as such may serve as the origin or termination point of a LSP. In embodiments, the PEs  102  may reside at the edge of or interface with devices that reside at the edge of a network provider&#39;s domain. Finally, the PEs  102  may comprise transport boxes similar to the transport boxes  106  described herein. 
     The CRs  104  may be any devices or components that exchange data with the PEs  102  and each other. For example, the CRs  104  may be routers, switches, or bridges, including backbone core bridges (BCBs) and/or backbone edge bridges (BEBs). In addition, the CRs  104  may implement one or more protocols, including MPLS, BGP, or OSPF. The CRs  104  may maintain MPLS LSPs, and as such may serve as an intermediate or transit node along a LSP. In embodiments, the CRs  104  may reside within the central region of a network provider&#39;s domain, e.g. not at the edge of the provider&#39;s domain. 
     Each CR  104  may be coupled to a transport box  106 . The transport box  106 , sometimes referred to as an optical transport box, may be a device that interfaces between a physical layer, such as an electrical or optical layer, and a higher layer, such as a media access control (MAC) layer, MPLS layer, or IP layer. Specifically, the transport box  106  may snoop the communications originated by and destined for the CR  104 , and implemented transparent bypass as described herein. 
     In some cases, a network operator may implement express bypass in the network  100 . For example, when traffic volume between two PEs  102 , e.g. PE  102   a  and PE  102   g , exceeds a threshold, a physical bypass  108  may be established between the PEs  102 . The physical bypass  108  may comprise a new path between PE  102   a  and PE  102   g . While the establishment of the physical bypass  108  is useful in reducing traffic flow through the CRs  104 , express bypass is not without limitations. For example, the physical bypass  108  can only be established when the PEs  102  reside within the same administrative domain. In addition, the physical bypass  108  creates adjacency between PE  102   a  and PE  102   g , which causes topology and route cost changes within the network. Such changes eventually lead to an unwanted increase in traffic on the express bypass  108  and other undesirable changes to traffic within the network  100 . 
       FIG. 2  illustrates an embodiment of a network  200  implementing transparent bypass. The network  200 , PEs  202 , and CRs  204  may be substantially the same as the network  100 , PEs  102 , and CRs  104  described above. However, the CRs  204  (and optionally the PEs  202 ) within the network  200  comprises packet-aware transport boxes  210   a - 210   d  (collectively,  210 ) instead of the transport boxes  106 . The packet-aware transport boxes  210  may be similar to the transport boxes  106 , but may comprise additional functionality, such as the ability to analyze and forward frames received from the PEs  202  and the CRs  204 , e.g. without passing those frames to the CR  204 . After analyzing the frames, the packet-aware transport boxes  210  may construct a forwarding table and decide whether to implement transparent bypass on any subsequently data frames. The packet-aware transport box may be configured to create the transparent bypass after snooping a complete set of path reservation and confirmation messages among the routers. The transparent bypass may occur at the layer one, which includes fiber, wavelength, SONET/SDH/OTN path, and may comprise a statistically multiplexed packet header. Alternatively, transparent bypass may occur at layer two, which includes ESPs in a VLAN and LSPs. Finally, transparent bypass may be implemented at any time, but is particularly useful when the traffic volume going through CRs  204  is approaching or about to exceed certain threshold or the CRs&#39;  204  link capacity. Finally, the packet-aware transport box may be configured to cease forwarding of the frames to the transparent bypass when a path maintenance message is not received within a predetermined time interval, when a path termination message is received, or when instructed to cease forwarding the frames to the transparent bypass by a network operator. 
     During transparent bypass, the packet-aware transport boxes  210  may analyze the frames received from the PEs  202  and the CRs  204  and determine whether the frames are control frames or data frames. If the frames are control frames, the packet-aware transport boxes  210  may forward the control frames to the CR  204  for routing and/or processing regardless of whether the control frames are associated with one the transparent bypass paths. Control frames may be used for establishing, maintaining, and removing paths, such as LSPs, in the network, and may comprise IP/MPLS control protocol data units (PDUs). Because the packet-aware transport boxes  210  have visibility into these frames, the packet-aware transport boxes  210  may maintain a forwarding database of paths associated with its CR  204 . As such, when the packet-aware transport boxes  210  receive a data frame, they may determine whether the data frame is associated with one of the paths, and if so, forward the data frame to their corresponding transparent bypass, e.g. without ever forwarding the data frame to the CR  204 . As such, the dashed line  212  may represent a data frame&#39;s path from PE  202   a  to PE  202   g , e.g. the bypass of CRs  204   a ,  204   c , and  204   d . In contrast, the dotted line  214  may represent how a control frame&#39;s path from PE  202   a  to PE  202   g  deviates from the dashed line  212 , e.g. the control frame&#39;s path goes through of CRs  204   a ,  204   c , and  204   d.    
       FIG. 3  illustrates an embodiment of a network  300  implementing transparent bypass. The network  300 , PEs  302 , CRs  304 , and packet-aware transport boxes  310  may be substantially the same as the network  200 , PEs  202 , CRs  204 , and packet-aware transport boxes  210  described above. However, the network  300  may be a logical full mesh core IP network, and as such may allow the packet-aware transport boxes  310  to establish a one-hop transport path between any two CRs  304 . For example, if the CRs  304  comprise Ethernet interfaces to the packet-aware transport boxes  310 , sometimes called packet-optical transport platforms (P-OTP) as is the case in Ethernet over SONET/SDH applications, then VLANs can be used as channels between the CRs  304 . Dashed lines  316  and  318  represent such one-hop transport paths between CRs  304 . When implementing the transparent bypass in a full mesh network, the packet-aware transport boxes  310  may utilize these one-hop transport paths, which further reduces the traffic volume at the intermediate CRs  304 , which act as intermediate label switched routers (LSRs) or transit routers. To the transit routers, the use of the one-hop transport paths is a double benefit because the transit routers see a traffic reduction on both their input ports and their output ports, e.g. when traffic is sent on path  318 , CR  304   c  sees a reduction in traffic associated with ports connected to CR  304   a  and CR  304   d . Note that while the benefit is realized for CR-CR ports, it does not affect the amount of traffic on PE ports. As such, the PEs  302  will eventually have to upgrade their port capacity to handle the increased data to/from the PEs  302 . Finally, most CR to P-OTP interfaces are 10 Gbps, which is usually required for any CR  304  interconnection. In order to show any significant advantage of logical mesh connections established by P-OTP, the CR to P-OTP interface may need to be as high as 40 Gbps or 100 Gbps, which is not currently commercially available in many networks. 
     There are many methods by which the packet-aware transport boxes can implement the transparent bypass. For example, if LSPs are calculated by a path computation element (PCE), then the PCE can send the transparent bypass information to the packet-aware transport box. In some instances, the PCE may comprise an upper layer PCE, such as a MPLS or IP layer PCE, and a lower layer PCE, such as a packet transport network (PTN), optical transport network (OTN), or a wavelength division multiplexed (WDM) layer PCE. In such cases, the upper layer PCE may consult the lower layer PCE for lower layer topology information. Alternatively, if there are pre-established LSPs, then the LSP forwarding table can be manually provisioned on the packet-aware transport boxes. However, it is expected that the transparent bypass will most often be implemented by allowing the packet-aware transport boxes to snoop the MPLS control protocol PDUs and establish LSP forwarding table accordingly. 
       FIG. 4  illustrates a method by which the packet-aware transport boxes snoop the MPLS control protocol PDUs and establish LSP forwarding table. Initially, a path control message  420  is sent from a first core router, e.g. CR  430 , to a second core router, e.g. CR  442 . The path control message  420  may be, for example, a resource reservation protocol—traffic engineering (RSVP-TE) message or label distribution protocol (LDP) message. The path control message  420  may contain a specific keyword key, perhaps a wildcard, that triggers the below-described actions when it is detected during the snooping. The key may be an ASCII string or substring, and may be inserted at CR  430  by a network administrator. When the packet-aware transport box  432  receives the path control message  420 , the packet-aware transport box  432  may ensure that the path control message  420  is requesting an appropriate object, such as a Record Route Object (RRO), and if so, forward the message to the CR  442 . 
     After the CR  442  processes the path control message  420 , the CR  442  may generate a path reserved (RESV) confirmation message  424  comprising the key, a RRO label (L 2 ), and a RESV destination. Upon receiving the RESV message  424 , the packet-aware transport box  440  programs its cross-connect fabric to map the L 2  label used on the hop it is snooping to its direct tunnel to the destination, which may be the packet-aware transport box  432 . This action effectively sets up the transparent bypass. As such, the packet-aware transport box  440  will subsequently strip the L 2  label off any data frames associated with the LSP and directs the data frames to a transport tunnel that terminates at the final snooping hop of the RSVP-TE path, namely the packet-aware transport box  432 . The RESV message  424  will progress, hop by hop, across the intermediate CR  436  and its transport boxes  434 , which may be packet-aware transport boxes. 
     When the packet-aware transport box  432  receives the final RESV message  424 , the packet-aware transport box  432  may look at the RRO, find the label L 2 , for example by looking at the first recorded hop/label in the RRO, and program its cross-connect to forward label L 2  from the tunnel to the packet-aware transport box  440  through its snooping interface. The packet-aware transport box  440  may also switch the label to the proper label (L 1 ) for this hop as seen in the Label object of the RESV message  422 . Thus, the RRO allows direct mapping of the first and last hops by the packet-aware transport boxes. As such, a multi-hop RSVP-TE path is turned into a three-hop path ( 442 - 440 - 432 - 430 ), the middle one of which is a direct detour bypassing all the inner hops. 
     When there are multiple optical links between two packet-aware transport boxes, there may be multiple options for mapping the LSPs to the transparent bypass path. For example, equal cost multi-path (ECMP) can be used to automatically map some LSPs to one of the transparent bypass paths. Alternatively, a network administrator may manually configure some LSPs to a fixed transparent bypass path. 
     Occasionally, faults may be detected along the bypass path. For example, a fault may be detected on a physical port associated with the transparent bypass by a packet-aware transport box. If a fault is detected, the packet-aware transport box may disable the transparent bypass function for the affected LSPs. As such, the data frames associated with the LSPs whose transparent bypass is disabled may be forwarded to CRs as if the transparent bypass never existed. When the fault is eventually detected by the router, the router may trigger fast re-route to get around the faulty link(s). The router that detects the fault may then notify the source of the LSP to establish a new LSP and switch all the data to the newly established LSPs. During the process of the new LSP being established, transparent bypass can be created by the packet aware transport boxes in the network. When the source router of the LSP switches data to the newly established data path, there may not be any control or data frames on the old LSP. As such, the packet-aware transport box may tear down transparent bypass accordingly after the timer for the path keep-alive message expires. 
     The packet-aware transport box may have many ports. For example, 20-40 ports are commonly used in transport boxes. When a failure occurs, only the data frames traversing through the faulty port may be sent to the CR. Even with the increase in traffic to the CR, the amount of frames sent to CR is still much less than the total amount of frames traversing all of the ports. 
     As described above, there are significant differences between express bypass and transparent bypass. Transparent bypass may generally be implemented for data frames on selected LSPs to reduce the data volume traversed through the CR&#39;s ports. As such, the traffic volume to and from the PEs can grow without increasing the port capacity on adjacent CRs. In addition, transparent bypass allows the PEs to continue peering with their original CRs. As such, there is no route or topology change to the routers, which means the transparent bypass does not affect the calculations for other routes. In other words, transparent bypass does not create any new adjacencies, and thus will not change the costs to other routes, cause any unexpected traffic switches to the newly established bypass, or cause other routers to change their forwarding tables. Finally, in transparent bypass all of the control data frames get sent to CRs, and as such when transparent bypass is disabled, all of the data flows are defined at the CRs, and the network acts as if the packet-aware transport boxes did not exist. 
     In some embodiments, the network may require special configuration to implement the transparent bypass. For example, the packet-aware transport box may need to be able to differentiate control frames, e.g. IP/MPLS control PDUs, from data frames, e.g. data PDUs. In addition, the packet-aware transport box may only transparently bypass data frames associated with paths that are implementing transparent bypass. In other words, data frames associated with paths not implementing transparent bypass, control frames, and other types of frames continue to be sent to the CR. Finally, the packet-aware transport box may have to manipulate the MPLS labels on the data frames as if the data frames went through the CR. 
     The network components 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. 5  illustrates a typical, general-purpose network component  500  suitable for implementing one or more embodiments of the components disclosed herein. The network component  500  includes a processor  502  (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage  504 , read only memory (ROM)  506 , random access memory (RAM)  508 , input/output (I/O) devices  510 , and network connectivity devices  512 . The processor  502  may be implemented as one or more CPU chips, or may be part of one or more application specific integrated circuits (ASICs). 
     The secondary storage  504  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  508  is not large enough to hold all working data. Secondary storage  504  may be used to store programs that are loaded into RAM  508  when such programs are selected for execution. The ROM  506  is used to store instructions and perhaps data that are read during program execution. ROM  506  is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of secondary storage  504 . The RAM  508  is used to store volatile data and perhaps to store instructions. Access to both ROM  506  and RAM  508  is typically faster than to secondary storage  504 . 
     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 l , 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 l +k*(R u −R l ), 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, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 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. 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. 
     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. 
     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.