WO2018033772A1

WO2018033772A1 - Advanced forwarding using multi-level fixed stage overlay

Info

Publication number: WO2018033772A1
Application number: PCT/IB2016/054911
Authority: WO
Inventors: Pramodh D’SOUZA; Márton KUN-SZABÓ; Atul Chowdhry
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-08-16
Filing date: 2016-08-16
Publication date: 2018-02-22

Abstract

A method and a network device generate an intermediate representation of platform independent routing information for a network. The intermediate representation is utilized to support multi- level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging. The method includes selecting a next hop in the routing information, checking whether all vias of the selected nexthop have completed intermediate representation, and combining an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

Description

ADVANCED FORWARDING USING MULTI-LEVEL FIXED STAGE OVERLAY

TECHNICAL FIELD

[0001] Embodiments of the invention relate to the field of network traffic routing and backup paths; and more specifically, to improving the handling of multi-level fast-rerouting in particular for network devices having fixed forwarding blocks and highly programmable processors.

BACKGROUND

[0002] Network devices compute a set of paths and next hops to reach other network devices within a domain. These network devices also compute backup paths to reach these destinations in the event of a failure of a link or node on the path to a given network device. Fast reroute (FRR) is a process that provides a fast recovery in the case of such network failures, referred to as network events. The backup paths, in particular for Internet Protocol domains, may be loop free alternative (LFA) paths.

[0003] Fast rerouting may be implemented in network devices where the network processors (i.e., network processor units (NPUs)) are highly programmable in a way that each primary path and backup path (i.e., a fast rerouting entity) is represented by its own individual 'unflattened' FRR nexthop (also referred to as a double-barrel nexthop or FRR nexthop). Thus, the fast rerouting entity includes one unflattened FRR nexthop consisting of a first indirection to a primary path to the destination and another indirection to a backup path to the destination, where the 'indirection' is an identifier for a next hop or intermediate node along a path to the destination network device. In some cases, instead of an identifier for the next hop, the unflattened FRR nexthop can refer to another unflattened FRR nexthop, which is referred to as a multi-level FRR, where each level is switched independently in response to a network event such as a forwarding fault detection. For example, if there is a network error that is reported to an implementing network device where the network error effects a later level of the FRR then only that level is switched to the backup path.

[0004] The forwarding of data traffic along a path toward a destination can be achieved by encapsulating the data traffic with a set of labels, addresses or similar identifiers for each of the intermediate and end destinations along the path. Encapsulation can be applied on any individual path, that is on either the primary path or the backup paths. This encapsulation defines a specific path with each part of the path correlating with additional encapsulation. The set of

encapsulations can be referred to as a forwarding chain. These forwarding chains can get fairly lengthy, thus operations affecting these forwarding chains or that operate over these forwarding chains can have significant computational requirements for the network device and its processors and related resources.

[0005] On network devices where the processors (e.g., NPUs) have fixed forwarding blocks, which are computational restrictions on the computation and processing of a forwarding chain, a 'flattened' path set is determined. A flattened path set determines the number and type of paths that the network device processor (e.g., an NPU) is able to handle. On some systems, the processor needs assistance to handle multi-level fast reroute, because the multi-level forwarding chains are not supported. Fast rerouting requires reaction to network failures. In cases where the processor of a network device (i.e., an NPU) cannot implement FRR directly to perform the failover necessary for FRR, the processor (i.e., an NPU) may work in combination with another processor (e.g., a central processing unit (CPU) or similar processor may be configured to assist. If the network processor (i.e., NPU) can support the FRR program, then a dedicated or platform specific code would be desired.

SUMMARY

[0006] In one embodiment, a method is executed by a network device. The method is for generating an intermediate representation of platform independent routing information for a network. The intermediate representation is to be utilized to support multi-level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a

dynamically established staging. The method selecting a next hop in the routing information, checking whether all vias of the selected nexthop have completed intermediate representation, and combining an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

[0007] In another embodiment, the network device generates the intermediate representation of platform independent routing information for the network, the intermediate representation to be utilized to support multi-level FRR in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging. The network device includes a non- transitory machine-readable medium having stored therein a representation transformer, and a processor coupled to the non-transitory machine-readable medium. The processor executes the representation transformer. The representation transformer selects a next hop in the routing information, checks whether all vias of the selected nexthop have completed intermediate representation, and combines an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

[0008] In a further embodiment, a control plane device is configured to implement at least one centralized control plane for a software defined networking (SDN) network. The centralized control plane is configured to execute the method for generating an intermediate representation of platform independent routing information for a network. The intermediate representation is to be utilized to support multi-level FRR in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging. The control plane device includes a non- transitory machine-readable medium having stored therein a representation transformer, and a processor coupled to the non-transitory machine-readable medium. The processor executes the representation transformer. The representation transformer selects a next hop in the routing information, checks whether all vias of the selected nexthop have completed intermediate representation, and combines an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

[0009] In one embodiment, a computing device implements a plurality of virtual machines for implementing network function virtualization (NFV), wherein a virtual machine from the plurality of virtual machines is configured to execute a method for generating an intermediate representation of platform independent routing information for a network. The intermediate representation is utilized to support multi-level FRR in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging. The computing device includes a non-transitory machine-readable medium having stored therein a representation transformer; and a processor coupled to the non-transitory machine-readable medium. The processor executes the representation transformer. The representation transformer selects a next hop in the routing information, checks whether all vias of the selected nexthop have completed intermediate representation, and combines an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings: [0011] Figure 1 is a diagram of one embodiment of a network device implementing assisted multi-level forwarding.

[0012] Figure 2 is a flowchart of one embodiment of a process to generate an intermediate form and a platform dependent form of platform independent routing information.

[0013] Figures 3A and 3B are flowcharts of one example embodiment of a merge operation to combine the intermediate representation of the routing information to generate a protocol dependent representation.

[0014] Figure 4A is a diagram of one embodiment of a transformation of a fast reroute (FRR) forwarding chain for single stage hardware platform with no hardware FRR support.

[0015] Figure 4B is a diagram of one embodiment of a transformation of an equal cost multipath over FRR forwarding chain for single stage hardware platform with no hardware FRR support.

[0016] Figure 4C is a diagram of one embodiment of a transformation of an FRR forwarding chain for a multi-stage hardware platform with hardware FRR support.

[0017] Figure 5 is a diagram of one embodiment of a process for a protection table refresh process.

[0018] Figure 6A is a flowchart of one embodiment of a configuration of a fast failure notification (FFN) program.

[0019] Figure 6B is a flowchart of one embodiment of an operation of a FFN program.

[0020] Figure 7A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some

embodiments of the invention.

[0021] Figure 7B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.

[0022] Figure 7C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.

[0023] Figure 7D illustrates a network with a single network element (NE) on each of the NDs, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention.

[0024] Figure 7E illustrates the simple case of where each of the NDs implements a single NE, but a centralized control plane has abstracted multiple of the NEs in different NDs into (to represent) a single NE in one of the virtual network(s), according to some embodiments of the invention. [0025] Figure 7F illustrates a case where multiple VNEs are implemented on different NDs and are coupled to each other, and where a centralized control plane has abstracted these multiple VNEs such that they appear as a single VNE within one of the virtual networks, according to some embodiments of the invention.

[0026] Figure 8 illustrates a general purpose control plane device with centralized control plane (CCP) software 850), according to some embodiments of the invention.

DETAILED DESCRIPTION

[0027] The following description describes methods and apparatus for improving the handling of multi-level fast-rerouting in particular for network devices having fixed forwarding blocks and highly programmable processors. The embodiments transform a platform independent representation of routing information in the form of unflattened next-hop chains into forwarding chains that are compatible with specific network device hardware. In particular, the process facilitates the generating of forwarding chains for network devices that have a fixed forwarding block architecture. In addition, the embodiments support multiple levels of fast reroute (FRR) where there is no hardware support in the network device or the support for multi-level FRR is limited. The process uses an intermediate representation to facilitate the generation and support for the multi-level FRR at the network device. In some embodiments, the intermediate representation is in the form of a set of protection tables.

[0028] In some embodiments, a fast failure notification (FFN) program operates at the network device to support the multi-level FRR implementation. The intermediate representation, for example, protection tables, are provided to the FFN program, along with the flattened nexthop chains. In embodiments where the intermediate representation can be implemented by the network device without assistance the FFN program is not utilized. For example, where protection Tables with one entry (i.e., unprotected Path Set chains) do not need to be handled by the FFN program.

[0029] In embodiments using the FFN, the protection table or similar representation with more than one flattened next-hop chain is linked to a protected entity state descriptor in the FFN program. This descriptor maintains the state of the protected entity. When a network failure event occurs related to a protected entity, all protection tables associated with it are visited and a flattened nexthop chain corresponding to the current state of all descriptors it is associated with is activated. The embodiments are suitable for handling any combinations of multipath (e.g.: equal cost multipath (ECMP)) and FRRs and handling different encapsulations.

[0030] The embodiment also provides an extension of the method to apply to more than one fixed forwarding block that is chained, and such an emulation to optimize forwarding, convergence and scale even on advanced network processor that are highly programmable and do not have fixed forwarding block limitations.

[0031] In the following description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.

[0032] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0033] Bracketed text and blocks with dashed borders (e.g., large dashes, small dashes, dot- dash, and dots) may be used herein to illustrate optional operations that add additional features to embodiments of the invention. However, such notation should not be taken to mean that these are the only options or optional operations, and/or that blocks with solid borders are not optional in certain embodiments of the invention.

[0034] Terms

[0035] In the following description and claims, the terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. "Coupled" is used to indicate that two or more elements, which may or may not be in direct physical or electrical contact with each other, co-operate or interact with each other. "Connected" is used to indicate the establishment of communication between two or more elements that are coupled with each other.

[0036] An electronic device stores and transmits (internally and/or with other electronic devices over a network) code (which is composed of software instructions and which is sometimes referred to as computer program code or a computer program) and/or data using machine-readable media (also called computer-readable media), such as machine-readable storage media (e.g., magnetic disks, optical disks, read only memory (ROM), flash memory devices, phase change memory) and machine-readable transmission media (also called a carrier) (e.g., electrical, optical, radio, acoustical or other form of propagated signals - such as carrier waves, infrared signals). Thus, an electronic device (e.g., a computer) includes hardware and software, such as a set of one or more processors coupled to one or more machine-readable storage media to store code for execution on the set of processors and/or to store data. For instance, an electronic device may include non- volatile memory containing the code since the non-volatile memory can persist code/data even when the electronic device is turned off (when power is removed), and while the electronic device is turned on that part of the code that is to be executed by the processor(s) of that electronic device is typically copied from the slower nonvolatile memory into volatile memory (e.g., dynamic random access memory (DRAM), static random access memory (SRAM)) of that electronic device. Typical electronic devices also include a set or one or more physical network interface(s) to establish network connections (to transmit and/or receive code and/or data using propagating signals) with other electronic devices. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0037] A network device (ND) is an electronic device that communicatively interconnects other electronic devices on the network (e.g., other network devices, end-user devices). Some network devices are "multiple services network devices" that provide support for multiple networking functions (e.g., routing, bridging, switching, Layer 2 aggregation, session border control, Quality of Service, and/or subscriber management), and/or provide support for multiple application services (e.g., data, voice, and video).

[0038] A path is a forwarding information such as forwarding encapsulation (i.e., header information associated to attached to a data packet) and/or information that links to another path where the forwarding information is used to forward a data packet toward a destination in the network, for example a next-hop Internet Protocol (IP) address. Each path has a protection Path Attribute.

[0039] A protection path attribute is a value or field of a path that indicates whether the path is protected or unprotected. A path is protected where an alternate path exists to reach a destination associated with the path. In some embodiments, a protected path has a protected entity which is a property of the path such as a protected address (e.g. an IP address, the IP address may be referred to herein as an IP for simplicity and conciseness). The protected address can be any type of address or similar identifier such as an IP address, physical port, application to be protected, a resource to be protected or similar entity. An IP address is provided herein below by way of example and not limitation. [0040] In one example two paths are present:

[0041] Path (1) circuitl, nexthop IP 10.1.1.2(connected), Protected (protected IP 10.1.1.2)

[0042] Path (2) Label LI, nexthop IP 2.2.2.2 (not connected), Unprotected

[0043] In path (1) encapsulation 'circuitl' is defined and then the remainder is the protection path attribute with protected entity nexthop IP 10.1.1.2 and the value protected. Path (2) has encapsulation LI and path attribute with protected entity nexthop IP 2.2.2.2 and value unprotected.

[0044] A protection path collection is an ordered set of paths with each path followed by the path that protects it, and where the last path in the collection will be unprotected. The set of paths can include a primary path, secondary path, ternary path and so on based on their order. For example, a ternary path can be said to protect the primary path and the secondary path, as well as all paths preceding it.

[0045] A path set is a finite ordered set of paths that can contain unprotected paths, and/or protection path collections.

[0046] An unflattened path set is a path set that can contain unprotected paths, and/or protection path collections. This is a set of paths that a Protocol specifies when adding a route. The path set is 'unflattened' in that it is platform independent, thus, it must be transformed to a flattened path set to be utilized by a network processor.

[0047] An unflattened nexthop or unflattened nexthop chain is a product of a function that creates a hierarchical representation of an unflattened path set having a platform independent format. Each member of this chain is called a nexthop, and the chain is called an unflattened nexthop Chain. These nexthops can contain unprotected paths or protection path collections, but not both. Nexthops can reference or resolve on routes in the routing table, as a result unflattened nexthop chains are linked to other unflattened nexthop chains, forming larger chains. There may be platform independent limits on the number of unflattened nexthops in a chain.

[0048] A nexthop via or simply a via is a nexthop' s path's link to the next nexthop in the nexthop chain. For example, when an unflattened path set with four protection path collections (e.g., pairs of primary and secondary paths) with equal weight and connected, is transformed into a chain - it would result in an equal cost multipath (ECMP) nexthop with four unprotected paths, each with a via pointing to an FRR nexthop and where each FRR nexthop in turn will have a protection pair with via's pointing to connected next-hops and where each connected next hop (CNH) has one unprotected path with no via. Each path in these Next-hops may have encapsulation information. Examples of these data structures are described herein below with reference to Figure 4A-C. [0049] A stage an identifier for a fixed forwarding block, which corresponds with a fixed number of indirections in a nexthop chain. For example, a fixed forwarding block, e.g. a one- stage fixed forwarding block supporting ECMP -> FRR -> CNH or desired logical forwarding block (i.e., where it is not limited by hardware but a desire to limit for performance or optimization reasons). Stages can be chained. For example, a network processor may be able to support 2 stages or more stages.

[0050] A terminus or a terminus unflattened nexthop is an unflattened nexthop that corresponds to the outermost encapsulation and in the hierarchical representation is a leaf in the tree structure.

[0051] A flattened path set is a path set that is formed as part of a transformation or 'merge' operation on an unflattened nexthop chain and/or an intermediate representation. These flattened path sets may contain unprotected paths, and/or protection path collections.

However, the representation of the unprotected paths and/or protection path collection is constrained to be what can be supported by a given stage in hardware of the network processor or what is configured for optimization purposes in terms of the fixed forwarding block. Each path contains an encapsulation stack. In some embodiments, the limit on the number of paths in an unflattened path set may be different from that of a flattened path set, the latter being higher.

[0052] A protection table is an intermediate representation of the platform independent representation or the unflattened path set. The protection table is a table consisting of a) flattened Path Set(s), each having a primary path/backup path relationship to 0 or more other flattened path sets in the protection table; and b) the primary IP's (IP address) defining the aforementioned relationship and its possible states (up/down). A flattened path set A is said to have a primary path/backup path relationship with a flattened path set B when for a given protection table entry with the tuple [IP-a.b.c.d], while the IP is Up set A is used, while if the IP is down, set B is used. The [IP, a.b.c.d] is the IP of a protected path pair that could not be supported in hardware by the target network device. A flattened path set exists for each combination of all primary path set states. Each flattened path set represents encapsulation and reachability for each combination.

[0053] For n primary IP's, the protection table would contain 2^An flattened path sets. A protection table with one flattened path set would contain a flattened path set that is not protected by another flattened path set (2^A0 =1), will have no primary IP and hence no state values. The protection table also contains the current stage of the nexthop. The protection table initially points to the flattened path set which corresponds to all the primary IP's in the Up state. [0054] In one embodiment, a protection table may have a bit position for primary IP of a protected pair that cannot be supported by the hardware of the network processor. When the bit is set to 0, it indicates that the particular IP is reachable and the entries corresponding to that would be the Flattened Path Set to be used. If the bit is 1 (i.e., the primary IP is not reachable), each entry would also have the flattened Path set that is to be used. In some further embodiments, there can be multiple bits, one for each such primary IP.

[0055] Merge operation or transformation process is an operation that converts each path of an unflattened nexthop and its via's to form an intermediate representation, for example a protection table, associated with the unflattened nexthop. In some embodiments, for simplicity, protection tables need not be created for the stage terminus unflattened nexthops or for the unflattened nexthops preceding them in the forwarding chain that fit into the stage.

[0056] A flattened nexthop or flattened nexthop chain is created by the transformation process using the flattened path sets in the protection table. The function is similar to the one used by protocols to create unflattened nexthop chains. These nexthop chains will be linked over each other to form larger chains supported by the hardware (e.g., multi-stage) as part of the flattening process. Each flattened nexthop can be directly mapped to one or more hardware resource associated with the target network device and network processor.

[0057] A highly programmable NPU is a networking processor that is able to handle arbitrary level of chained paths.

[0058] A forwarding fault detection is any means of detecting link failure on networking processors or via the networking processors (e.g.: bidirectional forwarding detection or similar processes).

[0059] A forwarding or data plane is the packet forwarding function within a network device, whereas the control plane is the function for a network device that determines routing and configuration.

[0060] The fast failure notification (FFN) program is a program that performs functions to switch among entries in the protection table by monitoring the state of the primary IPs (i.e., the links and network devices associated therewith and whether they are functioning). This program only deals with failure detection. Thus, the FFN program may identify IPs that have switched from Up to Down, but the control plane convergence is required to reinstate IPs in an UP state in protection tables.

[0061] A protected entity state descriptor is a data structure accessible for the FFN program that refers to a primary IP, holds its current protection state (primary or backup) and a sequence number (version). [0062] The embodiments overcome the disadvantage of the prior art. The prior art does not provide any solution for handling multi-level fast-rerouting for network processors with fixed forwarding blocks or optimized solutions for highly programmable NPU's. The embodiments overcome these limitations of the prior art. As set forth above, the proposed solution transforms unflattened nexthop chains into chains that are compatible with specific network device hardware that has a fixed forwarding block architecture. The embodiments have the ability to support multiple levels of fast reroute (FRR) where there is no hardware support for it or support is limited, the method describes the use of an intermediate form of a platform independent representation of routing information. In some embodiments, the intermediate for is a set of protection tables.

[0063] The embodiments provide a transform process that converts a platform independent representation, such as the unflattened nexthop chains into a platform dependent

representation, and to provide an additional intermediate representation (e.g. protection tables) to the FFN program to assist in rerouting for multi-level FRR. The transformation process or 'flattening' process operates by 'walking' or traversing the nexthops in a selected path with any 'walk' or traversal function, and flattening each one such that a nexthop is flattened when its vias have all been flattened. In one example based on the pseudocode provided herein below for each nexthop a call to the main function is made with the current unflattened nexthop as the input parameter. In case of re-resolution or path modification (unflattened path add/ unflattened path delete), the protection table associated with the nexthops resolving on it is deleted and recomputed after convergence.

[0064] Overview

[0065] Figure 1 is a diagram of one embodiment of a network device implementing the multi-level FRR process. The network device 101 includes a control plane 103 and a forwarding or data plane 105. The control plane 103 can include platform independent routing information 107 and a representation transformer 109. The forwarding plane 105 includes the FFN program 113 and the operations of the network processor 115 to process ingress traffic from the network and forward the network traffic as egress traffic. The control plane 103 configures the routing information of the forwarding plane 105 in the form of the platform dependent routing information 111 and the intermediate representation. The intermediate representation may be utilized by the FFN program 113 to facilitate rerouting in the event of a network failure. The FFN program 113 is notified of such network events as forwarding fault notifications from the network processor 115. The FFN program 113 uses the intermediate representation to effect any reroutes consistent with intermediate representation of back up paths. [0066] The operations in the flow diagrams will be described with reference to the exemplary embodiments of the other figures. However, it should be understood that the operations of the flow diagrams can be performed by embodiments of the invention other than those discussed with reference to the other figures, and the embodiments of the invention discussed with reference to these other figures can perform operations different than those discussed with reference to the flow diagrams.

[0067] Transformation Process

[0068] Figure 2 is a flowchart of one embodiment of a process to generate an intermediate form and a platform dependent form of platform independent routing information. In one embodiment the transformation process can be triggered in response to any update or convergence process for a network in which the implementing network device is situated (Block 201). The input into the transformation process is the platform independent

representation of the routing information for a network. In one embodiment, this input platform independent representation includes an unflattened path set. A check is made whether all nexthops in the unflattened path set have been processed (Block 203). If all of the nexthops have been processed, then the transformation process completes.

[0069] If all of the nexthops have not been processed, then the next nexthop to be processed is selected (Block 205). Any selection algorithm can be utilized to select the next nexthop. The merge operation of the overall transformation process effects the flattening of the unflattened nexthop chain where a check is first made whether an intermediate representation and/or a flattened nexthop chain has been created for the selected nexthop (Block 207). If an intermediate representation has already been completed, then the process continues to check another nexthop (Block 203) until all have been exhausted.

[0070] Where there is not an intermediate representation already, then the process checks whether the selected nexthop has at least one via (Bloc 209). If there are no vias for the nexthop, then the nexthop must be a terminus for the routing information. An intermediate representation is generated from the flattened path set for the selected nexthop. (Block 211). Where there is a via, then a check is made whether all vias of the selected next hop have completed intermediate representations (Block 213). Where all of the vias have selected next hop have not been processed into the intermediate representation, then the next nexthop selection commenced. However, where there is a completion of the intermediate representation for all vias of the selected next hop, then the process combines the intermediate representation of each via of the selected next hop to form the intermediate representation of the selected nexthop restricted by the platform support of the target network device or by optimization parameters specified by the administrator (Block 215). Platform support can be tied to hardware, virtualized hardware, execution environment or similar limitations on the program that require platform specific implementations. The process then checks whether all the next hops have an intermediate representation completed (Block 203).

[0071] Figure 3 is a flowchart of one example embodiment of a merge operation to combine the intermediate representation of the routing information to generate a protocol dependent representation. The process may begin with a request to generate an intermediate representation (e.g., a set of protection tables) for a given nexthop (Block 301). A check may be made whether the protection table has been completed for the given next hop (Block 303). If a set of protection tables already exists for the given nexthop then the process may end. Where there is not an existing set of protection tables, the process may check whether any via of the nexthop does not have a protection table (Block 305). If no vias of the nexthop do not have a protection table, then the process completes.

[0072] If any via of the nexthop does not have a protection table, then a determination of a stage of the nexthop is made based on whether the nexthop is a terminus, platform (e.g., hardware) limitations or optimization parameters (Block 307). The protection table to be output for the nexthop is generated and initialized (Block 309).

[0073] A check is made whether a nexthop is a terminus, where the nexthop is a terminus, then a flattened path set is inserted into the protection table (Block 313). Then flattened next hop chains can be created for each flattened path set in the protection table (Block 329). The head of the flattened nexthop chain is saved along with each flattened path set (Block 331). Where the nexthop is not a terminus, then the process selects a next path from the unflattened path set of the next hop (Block 315). A stage is assigned to the protection table for the next hop

(Block 317). A check is made whether the stage is the same as the via protection table stage (Block 219).

[0074] If the stage is the same, then the process inserts a flattened next hop for each via (Block 321). Then flattened next hop chains can be created for each flattened path set in the protection table (Block 329). The head of the flattened nexthop chain is saved along with each flattened path set (Block 331). If the stage is not the same, then the process inserts column for each IP of each via of the next hop (Block 323). IP states are inserted into the IP columns from via protection tables (Block 325). For each row of the protection table of the next hop, a flattened path set is inserted for the IP state (Block 327). Then flattened next hop chains can be created for each flattened path set in the protection table (Block 329). The head of the flattened nexthop chain is saved along with each flattened path set (Block 331).

[0075] One example implementation of the process for transforming the unflattened nexthop path set is set forth in pseudocode herein below: [0076] Method of transformation, start pseudocode section:

Support Function: build_flatten_path_set (input: curr flatten path set, current un- flattened next-hop's path info, via flattened path set, output: new flattened path-set)

Create new flattened path set using paths in curr flattened path set

Append the encapsulation of the un-flattened Path to each Path in the via Flattened Path Set Append these paths to the new flattened path set

// pruning and weight computation may be done at this point, weights are assigned per path Entity This is another IVD we may submit at a later time.

End

Support function: build_protection_table (input: current un-flattened next-hop, via next- hop info, output: current next-hop's updated protection table)

Get via's Next-Hop protection table (Referred to as viaProtTable).

Create a new protection table (Referred to as newProtTable) and insert columns

corresponding to all viaProtTable 's

Primary IP's in it.

Assign the un-flattened next-hop's protection table's (Referred to as currProtTable) stage to newProtTable.

Insert Primary IP's columns of currProtTable to the right of the NewProtTable existing primary IPs columns.

FOR EACH row in the viaProtTable (Referred to as viaProtTableRow)

FOR EACH row in the currProtTable (Referred to as currProtTableRow)

Insert a new row in the newProtTable (Referred to as newProtTableRow)

Copy the IP states of the viaProtTableRow and currProtTableRow in to

newProtTableRow

IF (for the given via - State of "protected IP" "if applicable" is UP AND state of "list of all

IP's" "if applicable" being protected - ALL DOWN ) // No Protecting IP's or Protected IP's would also go here..

IF stage of the currProtTable == stage of the viaProtTable // unflattened nhop in same stage as via

build_Flattened_Path_Set //viaProtTableRow' s path set

Copy Flattened Path Set into the current row of the newProtTable ELSE // Unflatenned nhop in higher stage than via

Copy the current unflattened nh's path set into the newProtTableRow

Copy viaProtTableRow's flattened nh head reference into newProtTableRow path set.

ELSE

Copy currProtTableRow's path set into the newProtTable // skip merging // Advance to next row

// Advance to next row

Replace currProtTable with NewProtTable

End

Init_protection_table (inout: unflattened next-hop, Stage)

Create protection table and assign stage

IF unFlattened Nexthop has a protection path collection

IF (path collection CANNOT be supported in Hardware)

Insert column's with protected IP's

For each combination of protected IP states, insert row with states and a NULL flattened path set; (could use a recursive fn)

ELSE // protection collection can be supported in hardware

Insert row with NULL flattened path set //unprotected path set

ELSE // unprotected paths

Insert row with NULL flattened path set // This case also handles Terminus NH case

Determine_stage(input: next-hop , output: stage, stage_terminus)

If nexthop is Terminus // note for unflattened Next-hops it's a connected next-hop stage = 0

Else

stage is determined by implementation ( limited by hardware or desired optimization) - See Embodiment for a Broadcom example

// Note the implementation may choose to use a very generic method to determine the stage. Main Function: (input: unflattened next-hop, output: protection table)

If protection table already built

done

If at least one via doesn't have a flattened protection table

skip and process later stage = Determine_stage(); // determine stage of the current unflattened next- hop

Init_protection_table(stage)

IF nexthop doesn't have via-NH // Terminus ( a.k.a connected)

Build a Flattened Path Set using Terminus path information

Insert Flattened path Set into the protection table (protection table with 1 path Set. i.e, protection table with unprotected flattened path set.)

ELSE

FOR EACH path in the Un-Flattened Path Set: build_protection_table

Create flattened NH chains for each flattened path set in the protection table // Call

nh_info_proc_flat

Save head of the flattened nexthop chain along with each flattened path set

//End psuedocode section

[0077] Figure 4A is a diagram of one embodiment of a transformation of a fast reroute (FRR) forwarding chain for single stage hardware platform with no hardware FRR support. In this example the transformation process 'walks' the unflattened path set illustrated in the hierarchical format. Each node in this hierarchical format is an unflattened nexthop. The triangles represent the address or prefix associated with the unflattened next hop. The hierarchy represents relationships between the unflattened nexthops such that the address or reference to a leaf of the hierarchical representation involves the walking from the root of the hierarchical representation to the leaf to determine each level of encapsulation and indirection necessary to reach the network device corresponding to that leaf node and its associated address. [0078] The transformation process as described above can be applied to this platform independent representation of routing information. The transformation process in this example generates a set of protection tables for each of the nodes in the hierarchy in a set of steps 1-11. These protection tables can be utilized by an FFN for FRR and to configured the network processor. In this example steps 1-4 can be performed in any order, including in parallel. In each of steps 1-4 the transformation process handles each of the leaves and flattens them. The process may traverse other nodes, but they will be skipped due to not having vias with completed protection tables (i.e., intermediate representations). Each of these nexthops are terminus next hops. Also, they are unprotected. Thus they can each be flattened as a path set and stage number (i.e., stage 0).

[0079] The process can flatten the FRR nodes IP2 and IP3 after steps 1-4 complete. Steps 5 and 6 can be completed in parallel or in any order relative to each other, that is 5 and 6 can be performed after or before 7 and 8. Generating protection tables for IP2 and IP3 takes multiple steps with steps 5 and 7 initializing the protection tables with the IP and empty path sets. Then the path sets are populated based on the vias corresponding to the IP FRR states (i.e., Up or Down) in steps 6 and 8, respectively. A similar process occurs in steps 9-11. In step 9 the protection table for ΓΡ1 is generated and IP1 is added as a column with empty path sets for the UP and DOWN IP FRR states. In step 10, the primary IP next hope IP2 is added as a column and the path sets are flattened for each combination state of IP1 and IP2. Similarly, in step 11, IP3 is added as a column and the path sets are flattened or each IP1 and IP3 state combination thereby completing the protection table. In this embodiment, the hardware is constrained to having a single stage fixed forwarding block. Thus, the protection tables cannot reference other protection tables and must have completely flattened path sets.

[0080] Figure 4B is a diagram of one embodiment of a transformation of an equal cost multipath over FRR forwarding chain for single stage hardware platform with no hardware FRR support. The transformation process in this example generates a set of protection tables for each of the nodes in the hierarchy in a set of steps 1-11. These protection tables can be utilized by an FFN for FRR and to configured the network processor. As in the previous example, steps 1-4 can be performed in any order, including in parallel. In each of steps 1-4 the transformation process handles each of the leaves and flattens them. The process may traverse other nodes, but they will be skipped due to not having vias with completed protection tables (i.e., intermediate representations). Each of these nexthops are terminus next hops. Also, they are unprotected. Thus they can each be flattened as a path set and stage number (i.e., stage 0).

[0081] The process can flatten the FRR nodes IP2 and IP3 after steps 1-4 complete. Steps 5 and 6 can be completed in parallel or in any order relative to each other, that is 5 and 6 can be performed after or before 7 and 8. Generating protection tables for IP1 and IP2 takes multiple steps with steps 5 and 7 initializing the protection tables with the IP and empty path sets. Then the path sets are populated based on the vias corresponding to the IP FRR states (i.e., Up or Down) in steps 6 and 8, respectively. A similar process occurs in steps 9-11. However, ECMP occurs at the root node instead of FRR as in the prior example. In step 9 the protection table for ECMP is generated with an empty path set and stage 0. In step 10, the primary path nexthop IP1 is added as a column and the path sets are flattened for IP1. Similarly, in step 11, IP2 is added as a column and the path sets are flattened for each IP1 and IP3 state combination thereby completing the protection table. In this embodiment, the hardware is constrained to having a single stage fixed forwarding block. Thus, the protection tables cannot reference other protection tables and must have completely flattened path sets.

[0082] Figure 4C is a diagram of one embodiment of a transformation of an FRR forwarding chain for a multi-stage hardware platform with hardware FRR support. The transformation process in this example generates a set of protection tables for each of the nodes in the hierarchy in a set of steps 1-10. These protection tables can be utilized by an FFN for FRR and to configured the network processor. As in the previous example, steps 1-4 can be performed in any order, including in parallel. In each of steps 1-4 the transformation process handles each of the leaves and flattens them. The process may traverse other nodes, but they will be skipped due to not having vias with completed protection tables (i.e., intermediate representations). Each of these nexthops are terminus next hops. Also, they are unprotected. Thus they can each be flattened as a path set and stage number (i.e., stage 0).

[0083] The process can flatten the FRR nodes IP2 and IP3 after steps 1-4 complete. Steps 5 and 6 can be completed in parallel or in any order relative to each other, that is 5 and 6 can be performed after or before 7 and 8. Generating protection tables for IP2 and IP3 takes multiple steps with steps 5 and 7 initializing the protection tables with the IP and empty path sets. Then the path sets are populated based on the vias since the hardware supports FRR the pathsets of the vias are combined into an ordered path set in steps 6 and 8. The hardware also supports multiple stages, in this case two stages, such that the root of the hierarch can reference the first stage in the protection table and does not need to merge the lower stage in steps 9 and 10. FRR occurs at the root node. In step 9 the protection table for FRR is generated with an empty path set and stage 1. In step 10, the encapsulation of IP1 is added with pointers to the protection tables of IP2 and IP3 thereby completing the protection table. In this embodiment, the hardware is constrained to having a two stage fixed forwarding block. Thus, the protection tables can reference other groups of two protection tables and do not have completely flattened path sets. [0084] Network or Failure Event Handling

[0085] The FFN program is responsible for handling network events or failure events, and selecting the flattened nexthop chains from the protection table and provide this new information to the network processor as part of the fastpath or similar update to effect the reroute. In the FFN program, a set of protected entity state descriptors maintain the state of the protected entity (e.g., each nexthop). The Protected entity state descriptor holds a list of references to each protection table that has to be triggered upon a network event. When a network event or failure event occurs, the FFN program visits the protection tables that are referred to by the corresponding protected entity state descriptor, constructs the new forwarding information chain and programs the fastpath for the forwarding plane. The FFN program may mark the nexthop state (i.e., protection entity state) as Down in response to the failure.

[0086] When primary path becomes available (after having been down), the control plane software downloads the new state of the primary IP after network convergence with a different sequence number or version number. The FFN program compares this sequence number to the one stored in the protected entity state descriptor, and resets the path to primary, reprograms the fastpath to the primary path and updates the sequence number in the protected entity state descriptor in case new sequence number has been received.

[0087] Figure 5 is a diagram of one embodiment of a process for a protection table refresh process. Once the protection table has been formed, it needs to be refreshed only when the version of a corresponding IP address in the protection table has changed. In the case where additional encapsulation is present (e.g. label-non-connected nexthop), the routes that refer to the path with- and without encapsulation cannot point to the same protection table. In this case new sets of paths have to be created, in order to be able to carry the encapsulation information separately, and also a new protection table has to be created that incorporates the paths with additional encapsulation. The new paths and protection tables are the exact copy of the ones without encapsulation, plus the additional encapsulation information.

[0088] As shown in Figure 5 a series of primary path set states are received with each having a sequence number. These update the respective protection tables, with each version number indicating that it should replace the prior version number. The states are cleared to be UP when a new path set is installed. The diagram illustrates the interrelationship between the protected entities and the protection tables with the protected entities on the left and the protection tables on the right. Where a failure associated with a protected entity occurs a lookup in the protection tables associated with the address (e.g., IP1) cause a lookup into the protection table for the path update and in turn a reverse lookup of other addresses to determine state is made. For example, where a failure occurs with relation to IP1 both protection tables are affected and perform reverse look ups for the state of IP2 and IP3. With the state of IP1 being down and the states of IP2 and IP3 determined the path set can be determined in the protection table and an update performed.

[0089] Fast Failure Notification

[0090] Figure 6A is a flowchart of one embodiment of a configuration of a fast failure notification (FFN) program. The control plane configures the FFN program to enable it to update a network processor configuration in response to network evens thereby enacting a reroute process. The FFN program downloads a set of protection tables or similar intermediate representation from the control plane (Block 601). The control plane generates the platform independent representation of the network topology based on the forwarding protocols and policies implemented therein. The control plane also generates the intermediate representation that can be downloaded or sent to the FFN program.

[0091] The FFN program tracks a set of protected entities from the received intermediate representations. The protected entities are included in the received intermediate representation and each have a serial or version number to differentiate them from previous versions such that updates to the protected entities can be determined. Upon receiving the intermediate

representation including the protected entity a check is made whether the protected entities that have been received have a new version or serial number (Block 603). If a given protected entity does not have a new serial number or version, then the process repro grams the forwarding plane of the network device with a new path set for the protected entities (Block 607). An entry in the protection table corresponding to the protected entity is thus programmed. For example, if there are three protected IP addresses then the state of each should be used to select and update the forwarding plane.

[0092] If any of the received protection tables includes a protected entity with a new version number then the protection table associated with that protected entity is to be updated. The FFN program may mark the protected entity state as 'Up' in the descriptor or similar field or tracking structure of the protected entity (Block 605) In some embodiments, the protected entity is updated only if the version number or serial number is higher or later than the existing version number or serial number. Timestamps could also be used for this purpose. The network processor or the forwarding plane can then be updated with the new path set associated with the protection table and the updated protected entity (Block 607).

[0093] Figure 6B is a flowchart of one embodiment of an operation of a FFN program. The FFN program utilizes the protection tables or similar intermediate representation to update the network processor and the forwarding plane configuration in response to network events or failure events such as a failed link or node. The process is triggered in response to receiving a network event or a FFN event from the network processor or some component of the forwarding plane (Block 651). A check may be made whether the received event is a failure event indicating that a node or link in the network has failed thereby affecting the network topology and the forwarding of data traffic by the forwarding plane and the network processor such that a switch in routes may enable the continued forwarding of the traffic on a protected route

(Block 653). The backup or secondary path can be utilized until network convergence reestablishes the primary path. If the received event is not a failure event, then the process completes.

[0094] If a failure event has occurred, then the process marks the protected entities affected by the failure event as 'Down,' by altering the descriptor of the protected entity. Where there is a backup path associated with the protected entity (i.e., where there is a secondary or more path in the path set and FRR is not supported in the network processor) then the FFN program updates the network processor and the forwarding plane to use the backup path using the information from the protection table to identify the associated backup path (Block 657). The network processor and forwarding plane will continue to utilize the backup path until the primary path is reestablished by the control plane.

[0095] The embodiments provide advantages over the prior art. The embodiments, enable sub- 50ms rerouting on network processors that do not have hardware FRR support, or that have support limited by forwarding blocks (e.g.: protecting border gateway protocol (BGP) virtual private network (VPN) traffic, which needs to cater to multiple points of failure - local transport, local autonomous system border router (ASBR), egress premise equipment (PE)). The embodiments further have the ability to handle multi-level fast-rerouting using fixed forwarding blocks. The embodiments are not limited to IP Protection, but also supports a mix of different protection entities. The embodiments provide a unique protection table that generalizes protection of forwarding paths. The embodiments significantly increase forwarding throughput by collapsing multiple indirections, thus reducing the necessary number of lookups. The embodiments also handle all encapsulations, and any combinations of Multipath (e.g.: ECMP) and FRRs. The embodiments, support advanced multi-stage support, balancing the need for throughput performance, convergence and scale and the use of the methods on highly programmable network processors (i.e., NPUs).

[0096] Architecture

[0097] Figure 7A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some

embodiments of the invention. Figure 7A shows NDs 700A-H, and their connectivity by way of lines between 700A-700B, 700B-700C, 700C-700D, 700D-700E, 700E-700F, 700F-700G, and 700A-700G, as well as between 700H and each of 700A, 700C, 700D, and 700G. These NDs are physical devices, and the connectivity between these NDs can be wireless or wired (often referred to as a link). An additional line extending from NDs 700A, 700E, and 700F illustrates that these NDs act as ingress and egress points for the network (and thus, these NDs are sometimes referred to as edge NDs; while the other NDs may be called core NDs).

[0098] Two of the exemplary ND implementations in Figure 7 A are: 1) a special-purpose network device 702 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 704 that uses common off-the-shelf (COTS) processors and a standard OS.

[0099] The special-purpose network device 702 includes networking hardware 710 comprising compute resource(s) 712 (which typically include a set of one or more processors), forwarding resource(s) 714 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 716 (sometimes called physical ports), as well as non- transitory machine readable storage media 718 having stored therein networking software 720. A physical NI is hardware in a ND through which a network connection (e.g., wirelessly through a wireless network interface controller (WNIC) or through plugging in a cable to a physical port connected to a network interface controller (NIC)) is made, such as those shown by the connectivity between NDs 700A-H. During operation, the networking software 720 may be executed by the networking hardware 710 to instantiate a set of one or more networking software instance(s) 722. Each of the networking software instance(s) 722, and that part of the networking hardware 710 that executes that network software instance (be it hardware dedicated to that networking software instance and/or time slices of hardware temporally shared by that networking software instance with others of the networking software instance(s) 722), form a separate virtual network element 730A-R. Each of the virtual network element(s)

(VNEs) 730A-R includes a control communication and configuration module 732A-R

(sometimes referred to as a local control module or control communication module) and forwarding table(s) 734A-R, such that a given virtual network element (e.g., 730A) includes the control communication and configuration module (e.g., 732A), a set of one or more forwarding table(s) (e.g., 734A), and that portion of the networking hardware 710 that executes the virtual network element (e.g., 730A). In some embodiments, the networking software 720 may include representation transformer 791 and/or FFN program 793 that implement the functions described herein above in regard to Figures 2-6 where the representation transformer 791 generates an intermediate representation or platform dependent representation. The FFN program 793 performs the FFN process as described in regard to Figure 6B and is configured as described in regard to Figure 6 A. [00100] The special-purpose network device 702 is often physically and/or logically considered to include: 1) a ND control plane 724 (sometimes referred to as a control plane) comprising the compute resource(s) 712 that execute the control communication and

configuration module(s) 732A-R; and 2) a ND forwarding plane 726 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 714 that utilize the forwarding table(s) 734A-R and the physical NIs 716. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 724 (the compute resource(s) 712 executing the control communication and configuration

module(s) 732A-R) is typically responsible for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) and storing that routing information in the forwarding table(s) 734A-R, and the ND forwarding plane 726 is responsible for receiving that data on the physical NIs 716 and forwarding that data out the appropriate ones of the physical NIs 716 based on the forwarding table(s) 734A-R.

[00101] Figure 7B illustrates an exemplary way to implement the special-purpose network device 702 according to some embodiments of the invention. Figure 7B shows a special- purpose network device including cards 738 (typically hot pluggable). While in some embodiments the cards 738 are of two types (one or more that operate as the ND forwarding plane 726 (sometimes called line cards), and one or more that operate to implement the ND control plane 724 (sometimes called control cards)), alternative embodiments may combine functionality onto a single card and/or include additional card types (e.g., one additional type of card is called a service card, resource card, or multi-application card). A service card can provide specialized processing (e.g., Layer 4 to Layer 7 services (e.g., firewall, Internet Protocol Security (IPsec), Secure Sockets Layer (SSL) / Transport Layer Security (TLS), Intrusion Detection System (IDS), peer-to-peer (P2P), Voice over IP (VoIP) Session Border Controller, Mobile Wireless Gateways (Gateway General Packet Radio Service (GPRS) Support Node (GGSN), Evolved Packet Core (EPC) Gateway)). By way of example, a service card may be used to terminate IPsec tunnels and execute the attendant authentication and encryption algorithms. These cards are coupled together through one or more interconnect mechanisms illustrated as backplane 736 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[00102] Returning to Figure 7A, the general purpose network device 704 includes

hardware 740 comprising a set of one or more processor(s) 742 (which are often COTS processors) and network interface controller(s) 744 (NICs; also known as network interface cards) (which include physical NIs 746), as well as non-transitory machine readable storage media 748 having stored therein software 750. During operation, the processor(s) 742 execute the software 750 to instantiate one or more sets of one or more applications 764A-R. In some embodiments, the software 750 may include representation transformer 791 and/or FFN program 793 that implement the functions described herein above in regard to Figures 2-6 where the representation transformer 791 generates an intermediate representation or platform dependent representation. The FFN program 793 performs the FFN process as described in regard to Figure 6B and is configured as described in regard to Figure 6A. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization. For example, in one such alternative embodiment the virtualization layer 754 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 762A-R called software containers that may each be used to execute one (or more) of the sets of applications 764A-R; where the multiple software containers (also called virtualization engines, virtual private servers, or jails) are user spaces (typically a virtual memory space) that are separate from each other and separate from the kernel space in which the operating system is run: and where the set of applications running in a given user space, unless explicitly allowed, cannot access the memory of the other processes. In another such alternative embodiment the virtualization layer 754 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and each of the sets of applications 764A-R is run on top of a guest operating system within an instance 762A-R called a virtual machine (which may in some cases be considered a tightly isolated form of software container) that is run on top of the hypervisor - the guest operating system and application may not know they are running on a virtual machine as opposed to running on a "bare metal" host electronic device, or through para- virtualization the operating system and/or application may be aware of the presence of virtualization for optimization purposes. In yet other alternative embodiments, one, some or all of the applications are implemented as unikernel(s), which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application. As a unikernel can be implemented to run directly on hardware 740, directly on a hypervisor (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container, embodiments can be implemented fully with unikernels running directly on a hypervisor represented by virtualization layer 754, unikernels running within software containers represented by instances 762A-R, or as a combination of unikernels and the above-described techniques (e.g., unikernels and virtual machines both run directly on a hypervisor, unikernels and sets of applications that are run in different software containers).

[00103] The instantiation of the one or more sets of one or more applications 764A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 752. Each set of applications 764 A-R, corresponding virtualization construct (e.g., instance 762A-R) if implemented, and that part of the hardware 740 that executes them (be it hardware dedicated to that execution and/or time slices of hardware temporally shared), forms a separate virtual network element(s) 760A-R.

[00104] The virtual network element(s) 760A-R perform similar functionality to the virtual network element(s) 730A-R - e.g., similar to the control communication and configuration module(s) 732A and forwarding table(s) 734A (this virtualization of the hardware 740 is sometimes referred to as network function virtualization (NFV)). Thus, NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which could be located in Data centers, NDs, and customer premise equipment (CPE). While embodiments of the invention are illustrated with each instance 762A-R corresponding to one VNE 760A-R, alternative embodiments may implement this correspondence at a finer level granularity (e.g., line card virtual machines virtualize line cards, control card virtual machine virtualize control cards, etc.); it should be understood that the techniques described herein with reference to a correspondence of instances 762A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used.

[00105] In certain embodiments, the virtualization layer 754 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 762A-R and the NIC(s) 744, as well as optionally between the instances 762A-R; in addition, this virtual switch may enforce network isolation between the VNEs 760A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).

[00106] The third exemplary ND implementation in Figure 7A is a hybrid network device 706, which includes both custom ASICs/special-purpose OS and COTS processors/standard OS in a single ND or a single card within an ND. In certain embodiments of such a hybrid network device, a platform VM (i.e., a VM that that implements the functionality of the special-purpose network device 702) could provide for para-virtualization to the networking hardware present in the hybrid network device 706.

[00107] Regardless of the above exemplary implementations of an ND, when a single one of multiple VNEs implemented by an ND is being considered (e.g., only one of the VNEs is part of a given virtual network) or where only a single VNE is currently being implemented by an ND, the shortened term network element (NE) is sometimes used to refer to that VNE. Also in all of the above exemplary implementations, each of the VNEs (e.g., VNE(s) 730A-R, VNEs 760A-R, and those in the hybrid network device 706) receives data on the physical NIs (e.g., 716, 746) and forwards that data out the appropriate ones of the physical NIs (e.g., 716, 746). For example, a VNE implementing IP router functionality forwards IP packets on the basis of some of the IP header information in the IP packet; where IP header information includes source IP address, destination IP address, source port, destination port (where "source port" and

"destination port" refer herein to protocol ports, as opposed to physical ports of a ND), transport protocol (e.g., user datagram protocol (UDP), Transmission Control Protocol (TCP), and differentiated services code point (DSCP) values.

[00108] Figure 7C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention. Figure 7C shows VNEs 770A.1-770A.P (and optionally VNEs 770A.Q-770A.R) implemented in ND 700A and VNE 770H.1 in ND 700H. In Figure 7C, VNEs 770A.1-P are separate from each other in the sense that they can receive packets from outside ND 700A and forward packets outside of ND 700A; VNE 770A.1 is coupled with VNE 770H.1, and thus they communicate packets between their respective NDs; VNE 770A.2-770A.3 may optionally forward packets between themselves without forwarding them outside of the ND 700A; and VNE 770A.P may optionally be the first in a chain of VNEs that includes VNE 770A.Q followed by VNE 770A.R (this is sometimes referred to as dynamic service chaining, where each of the VNEs in the series of VNEs provides a different service - e.g., one or more layer 4-7 network services). While Figure 7C illustrates various exemplary relationships between the VNEs, alternative embodiments may support other relationships (e.g., more/fewer VNEs, more/fewer dynamic service chains, multiple different dynamic service chains with some common VNEs and some different VNEs).

[00109] The NDs of Figure 7A, for example, may form part of the Internet or a private network; and other electronic devices (not shown; such as end user devices including

workstations, laptops, netbooks, tablets, palm tops, mobile phones, smartphones, phablets, multimedia phones, Voice Over Internet Protocol (VOIP) phones, terminals, portable media players, GPS units, wearable devices, gaming systems, set-top boxes, Internet enabled household appliances) may be coupled to the network (directly or through other networks such as access networks) to communicate over the network (e.g., the Internet or virtual private networks (VPNs) overlaid on (e.g., tunneled through) the Internet) with each other (directly or through servers) and/or access content and/or services. Such content and/or services are typically provided by one or more servers (not shown) belonging to a service/content provider or one or more end user devices (not shown) participating in a peer-to-peer (P2P) service, and may include, for example, public webpages (e.g., free content, store fronts, search services), private webpages (e.g., username/password accessed webpages providing email services), and/or corporate networks over VPNs. For instance, end user devices may be coupled (e.g., through customer premise equipment coupled to an access network (wired or wirelessly)) to edge NDs, which are coupled (e.g., through one or more core NDs) to other edge NDs, which are coupled to electronic devices acting as servers. However, through compute and storage virtualization, one or more of the electronic devices operating as the NDs in Figure 7A may also host one or more such servers (e.g., in the case of the general purpose network device 704, one or more of the software instances 762A-R may operate as servers; the same would be true for the hybrid network device 706; in the case of the special-purpose network device 702, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 712); in which case the servers are said to be co-located with the VNEs of that ND.

[00110] A virtual network is a logical abstraction of a physical network (such as that in Figure 7A) that provides network services (e.g., L2 and/or L3 services). A virtual network can be implemented as an overlay network (sometimes referred to as a network virtualization overlay) that provides network services (e.g., layer 2 (L2, data link layer) and/or layer 3 (L3, network layer) services) over an underlay network (e.g., an L3 network, such as an Internet Protocol (IP) network that uses tunnels (e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol (L2TP), IPSec) to create the overlay network).

[00111] A network virtualization edge (NVE) sits at the edge of the underlay network and participates in implementing the network virtualization; the network-facing side of the NVE uses the underlay network to tunnel frames to and from other NVEs; the outward-facing side of the NVE sends and receives data to and from systems outside the network. A virtual network instance (VNI) is a specific instance of a virtual network on a NVE (e.g., a NE/VNE on an ND, a part of a NE/VNE on a ND where that NE/VNE is divided into multiple VNEs through emulation); one or more VNIs can be instantiated on an NVE (e.g., as different VNEs on an ND). A virtual access point (VAP) is a logical connection point on the NVE for connecting external systems to a virtual network; a VAP can be physical or virtual ports identified through logical interface identifiers (e.g., a VLAN ID).

[00112] Examples of network services include: 1) an Ethernet LAN emulation service (an Ethernet-based multipoint service similar to an Internet Engineering Task Force (IETF) Multiprotocol Label Switching (MPLS) or Ethernet VPN (EVPN) service) in which external systems are interconnected across the network by a LAN environment over the underlay network (e.g., an NVE provides separate L2 VNIs (virtual switching instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network); and 2) a virtualized IP forwarding service (similar to IETF IP VPN (e.g., Border Gateway Protocol (BGP)/MPLS IP VPN) from a service definition perspective) in which external systems are interconnected across the network by an L3 environment over the underlay network (e.g., an NVE provides separate L3 VNIs (forwarding and routing instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network)). Network services may also include quality of service capabilities (e.g., traffic classification marking, traffic conditioning and scheduling), security capabilities (e.g., filters to protect customer premises from network - originated attacks, to avoid malformed route announcements), and management capabilities (e.g., full detection and processing).

[00113] Fig. 7D illustrates a network with a single network element on each of the NDs of Figure 7A, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention. Specifically, Figure 7D illustrates network elements (NEs) 770A-H with the same connectivity as the NDs 700A-H of Figure 7A.

[00114] Figure 7D illustrates that the distributed approach 772 distributes responsibility for generating the reachability and forwarding information across the NEs 770A-H; in other words, the process of neighbor discovery and topology discovery is distributed.

[00115] For example, where the special-purpose network device 702 is used, the control communication and configuration module(s) 732A-R of the ND control plane 724 typically include a reachability and forwarding information module to implement one or more routing protocols (e.g., an exterior gateway protocol such as Border Gateway Protocol (BGP), Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS-IS), Routing Information Protocol (RIP), Label Distribution Protocol (LDP), Resource Reservation Protocol (RSVP) (including RS VP-Traffic Engineering (TE): Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol Label Switching

(GMPLS) Signaling RSVP-TE)) that communicate with other NEs to exchange routes, and then selects those routes based on one or more routing metrics. Thus, the NEs 770A-H (e.g., the compute resource(s) 712 executing the control communication and configuration

module(s) 732A-R) perform their responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by distributively determining the reachability within the network and calculating their respective forwarding information. Routes and adjacencies are stored in one or more routing structures (e.g., Routing Information Base (RIB), Label Information Base (LIB), one or more adjacency structures) on the ND control plane 724. The ND control plane 724 programs the ND forwarding plane 726 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 724 programs the adjacency and route information into one or more forwarding table(s) 734A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 726. For layer 2 forwarding, the ND can store one or more bridging tables that are used to forward data based on the layer 2 information in that data. While the above example uses the special-purpose network device 702, the same distributed approach 772 can be implemented on the general purpose network device 704 and the hybrid network device 706.

[00116] Figure 7D illustrates that a centralized approach 774 (also known as software defined networking (SDN)) that decouples the system that makes decisions about where traffic is sent from the underlying systems that forwards traffic to the selected destination. The illustrated centralized approach 774 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 776 (sometimes referred to as a SDN control module, controller, network controller, OpenFlow controller, SDN controller, control plane node, network virtualization authority, or management control entity), and thus the process of neighbor discovery and topology discovery is centralized. The centralized control plane 776 has a south bound interface 782 with a data plane 780 (sometime referred to the infrastructure layer, network forwarding plane, or forwarding plane (which should not be confused with a ND forwarding plane)) that includes the NEs 770A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 776 includes a network controller 778, which includes a centralized reachability and forwarding information module 779 that determines the reachability within the network and distributes the forwarding information to the NEs 770A-H of the data plane 780 over the south bound interface 782 (which may use the OpenFlow protocol). Thus, the network intelligence is centralized in the centralized control plane 776 executing on electronic devices that are typically separate from the NDs.

[00117] For example, where the special-purpose network device 702 is used in the data plane 780, each of the control communication and configuration module(s) 732A-R of the ND control plane 724 typically include a control agent that provides the VNE side of the south bound interface 782. In this case, the ND control plane 724 (the compute resource(s) 712 executing the control communication and configuration module(s) 732A-R) performs its responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) through the control agent communicating with the centralized control plane 776 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 779 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 732A-R, in addition to communicating with the centralized control plane 776, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach; such embodiments are generally considered to fall under the centralized approach 774, but may also be considered a hybrid approach).

[00118] While the above example uses the special-purpose network device 702, the same centralized approach 774 can be implemented with the general purpose network device 704 (e.g., each of the VNE 760A-R performs its responsibility for controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by communicating with the centralized control plane 776 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 779; it should be understood that in some embodiments of the invention, the VNEs 760A-R, in addition to communicating with the centralized control plane 776, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach) and the hybrid network device 706. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 704 or hybrid network device 706 implementations as NFV is able to support SDN by providing an infrastructure upon which the SDN software can be run, and NFV and SDN both aim to make use of commodity server hardware and physical switches.

[00119] Figure 7D also shows that the centralized control plane 776 has a north bound interface 784 to an application layer 786, in which resides application(s) 788. The centralized control plane 776 has the ability to form virtual networks 792 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 770A-H of the data plane 780 being the underlay network)) for the application(s) 788. Thus, the centralized control plane 776 maintains a global view of all NDs and configured NEs/VNEs, and it maps the virtual networks to the underlying NDs efficiently (including maintaining these mappings as the physical network changes either through hardware (ND, link, or ND component) failure, addition, or removal).

[00120] While Figure 7D shows the distributed approach 772 separate from the centralized approach 774, the effort of network control may be distributed differently or the two combined in certain embodiments of the invention. For example: 1) embodiments may generally use the centralized approach (SDN) 774, but have certain functions delegated to the NEs (e.g., the distributed approach may be used to implement one or more of fault monitoring, performance monitoring, protection switching, and primitives for neighbor and/or topology discovery); or 2) embodiments of the invention may perform neighbor discovery and topology discovery via both the centralized control plane and the distributed protocols, and the results compared to raise exceptions where they do not agree. Such embodiments are generally considered to fall under the centralized approach 774, but may also be considered a hybrid approach.

[00121] While Figure 7D illustrates the simple case where each of the NDs 700A-H implements a single NE 770A-H, it should be understood that the network control approaches described with reference to Figure 7D also work for networks where one or more of the

NDs 700A-H implement multiple VNEs (e.g., VNEs 730A-R, VNEs 760A-R, those in the hybrid network device 706). Alternatively or in addition, the network controller 778 may also emulate the implementation of multiple VNEs in a single ND. Specifically, instead of (or in addition to) implementing multiple VNEs in a single ND, the network controller 778 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 792 (all in the same one of the virtual network(s) 792, each in different ones of the virtual network(s) 792, or some combination). For example, the network controller 778 may cause an ND to implement a single VNE (a NE) in the underlay network, and then logically divide up the resources of that NE within the centralized control plane 776 to present different VNEs in the virtual network(s) 792 (where these different VNEs in the overlay networks are sharing the resources of the single VNE/NE implementation on the ND in the underlay network).

[00122] On the other hand, Figures 7E and 7F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 778 may present as part of different ones of the virtual networks 792. Figure 7E illustrates the simple case of where each of the NDs 700A-H implements a single NE 770A-H (see Figure 7D), but the centralized control plane 776 has abstracted multiple of the NEs in different NDs (the NEs 770A-C and G-H) into (to represent) a single NE 7701 in one of the virtual network(s) 792 of Figure 7D, according to some

embodiments of the invention. Figure 7E shows that in this virtual network, the NE 7701 is coupled to NE 770D and 770F, which are both still coupled to NE 770E.

[00123] Figure 7F illustrates a case where multiple VNEs (VNE 770A.1 and VNE 770H.1) are implemented on different NDs (ND 700A and ND 700H) and are coupled to each other, and where the centralized control plane 776 has abstracted these multiple VNEs such that they appear as a single VNE 770T within one of the virtual networks 792 of Figure 7D, according to some embodiments of the invention. Thus, the abstraction of a NE or VNE can span multiple NDs. [00124] While some embodiments of the invention implement the centralized control plane 776 as a single entity (e.g., a single instance of software running on a single electronic device), alternative embodiments may spread the functionality across multiple entities for redundancy and/or scalability purposes (e.g., multiple instances of software running on different electronic devices).

[00125] Similar to the network device implementations, the electronic device(s) running the centralized control plane 776, and thus the network controller 778 including the centralized reachability and forwarding information module 779, may be implemented a variety of ways (e.g., a special purpose device, a general-purpose (e.g., COTS) device, or hybrid device). These electronic device(s) would similarly include compute resource(s), a set or one or more physical NICs, and a non-transitory machine-readable storage medium having stored thereon the centralized control plane software. For instance, Figure 8 illustrates, a general purpose control plane device 804 including hardware 840 comprising a set of one or more processor(s) 842 (which are often COTS processors) and network interface controller(s) 844 (NICs; also known as network interface cards) (which include physical NIs 846), as well as non-transitory machine readable storage media 848 having stored therein centralized control plane (CCP) software 850. In some embodiments, the storage media 848 may include representation transformer 891 and/or FFN program 893 that implement the functions described herein above in regard to Figures 2-6 where the representation transformer 891 generates an intermediate representation or platform dependent representation. The FFN program 893 performs the FFN process as described in regard to Figure 6B and is configured as described in regard to Figure 6A.

[00126] In embodiments that use compute virtualization, the processor(s) 842 typically execute software to instantiate a virtualization layer 854 (e.g., in one embodiment the virtualization layer 854 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 862A-R called software containers (representing separate user spaces and also called virtualization engines, virtual private servers, or jails) that may each be used to execute a set of one or more applications; in another embodiment the virtualization layer 854 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and an application is run on top of a guest operating system within an instance 862A-R called a virtual machine (which in some cases may be considered a tightly isolated form of software container) that is run by the hypervisor ; in another embodiment, an application is implemented as a unikernel, which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application, and the unikernel can run directly on hardware 840, directly on a hypervisor represented by virtualization layer 854 (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container represented by one of instances 862A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 850 (illustrated as CCP instance 876A) is executed (e.g., within the instance 862A) on the virtualization layer 854. In embodiments where compute virtualization is not used, the CCP instance 876A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 804. The instantiation of the CCP instance 876A, as well as the virtualization layer 854 and

instances 862A-R if implemented, are collectively referred to as software instance(s) 852.

[00127] In some embodiments, the CCP instance 876A includes a network controller instance 878. The network controller instance 878 includes a centralized reachability and forwarding information module instance 879 (which is a middleware layer providing the context of the network controller 778 to the operating system and communicating with the various NEs), and an CCP application layer 880 (sometimes referred to as an application layer) over the middleware layer (providing the intelligence required for various network operations such as protocols, network situational awareness, and user - interfaces). At a more abstract level, this CCP application layer 880 within the centralized control plane 776 works with virtual network view(s) (logical view(s) of the network) and the middleware layer provides the conversion from the virtual networks to the physical view. In some embodiments, the non-transitory machine readable storage medium 848 may include representation transformer 791 and/or FFN program 793 that implement the functions described herein above in regard to Figures 2-6 where the representation transformer 791 generates an intermediate representation or platform dependent representation. The FFN program 793 performs the FFN process as described in regard to Figure 6B and is configured as described in regard to Figure 6A.

[00128] The centralized control plane 776 transmits relevant messages to the data plane 780 based on CCP application layer 880 calculations and middleware layer mapping for each flow. A flow may be defined as a set of packets whose headers match a given pattern of bits; in this sense, traditional IP forwarding is also flow-based forwarding where the flows are defined by the destination IP address for example; however, in other implementations, the given pattern of bits used for a flow definition may include more fields (e.g., 10 or more) in the packet headers. Different NDs/NEs/VNEs of the data plane 780 may receive different messages, and thus different forwarding information. The data plane 780 processes these messages and programs the appropriate flow information and corresponding actions in the forwarding tables (sometime referred to as flow tables) of the appropriate NE/VNEs, and then the NEs/VNEs map incoming packets to flows represented in the forwarding tables and forward packets based on the matches in the forwarding tables.

[00129] Standards such as OpenFlow define the protocols used for the messages, as well as a model for processing the packets. The model for processing packets includes header parsing, packet classification, and making forwarding decisions. Header parsing describes how to interpret a packet based upon a well-known set of protocols. Some protocol fields are used to build a match structure (or key) that will be used in packet classification (e.g., a first key field could be a source media access control (MAC) address, and a second key field could be a destination MAC address).

[00130] Packet classification involves executing a lookup in memory to classify the packet by determining which entry (also referred to as a forwarding table entry or flow entry) in the forwarding tables best matches the packet based upon the match structure, or key, of the forwarding table entries. It is possible that many flows represented in the forwarding table entries can correspond/match to a packet; in this case the system is typically configured to determine one forwarding table entry from the many according to a defined scheme (e.g., selecting a first forwarding table entry that is matched). Forwarding table entries include both a specific set of match criteria (a set of values or wildcards, or an indication of what portions of a packet should be compared to a particular value/values/wildcards, as defined by the matching capabilities - for specific fields in the packet header, or for some other packet content), and a set of one or more actions for the data plane to take on receiving a matching packet. For example, an action may be to push a header onto the packet, for the packet using a particular port, flood the packet, or simply drop the packet. Thus, a forwarding table entry for IPv4/IPv6 packets with a particular transmission control protocol (TCP) destination port could contain an action specifying that these packets should be dropped.

[00131] Making forwarding decisions and performing actions occurs, based upon the forwarding table entry identified during packet classification, by executing the set of actions identified in the matched forwarding table entry on the packet.

[00132] However, when an unknown packet (for example, a "missed packet" or a "match- miss" as used in OpenFlow parlance) arrives at the data plane 780, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 776. The centralized control plane 776 will then program forwarding table entries into the data plane 780 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 780 by the centralized control plane 776, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry. [00133] A network interface (NI) may be physical or virtual; and in the context of IP, an interface address is an IP address assigned to a NI, be it a physical NI or virtual NI. A virtual NI may be associated with a physical NI, with another virtual interface, or stand on its own (e.g., a loopback interface, a point-to-point protocol interface). A NI (physical or virtual) may be numbered (a NI with an IP address) or unnumbered (a NI without an IP address). A loopback interface (and its loopback address) is a specific type of virtual NI (and IP address) of a

NE/VNE (physical or virtual) often used for management purposes; where such an IP address is referred to as the nodal loopback address. The IP address(es) assigned to the NI(s) of a ND are referred to as IP addresses of that ND; at a more granular level, the IP address(es) assigned to NI(s) assigned to a NE/VNE implemented on a ND can be referred to as IP addresses of that NE/VNE.

[00134] Next hop selection by the routing system for a given destination may resolve to one path (that is, a routing protocol may generate one next hop on a shortest path); but if the routing system determines there are multiple viable next hops (that is, the routing protocol generated forwarding solution offers more than one next hop on a shortest path - multiple equal cost next hops), some additional criteria is used - for instance, in a connectionless network, Equal Cost Multi Path (ECMP) (also known as Equal Cost Multi Pathing, multipath forwarding and IP multipath) may be used (e.g., typical implementations use as the criteria particular header fields to ensure that the packets of a particular packet flow are always forwarded on the same next hop to preserve packet flow ordering). For purposes of multipath forwarding, a packet flow is defined as a set of packets that share an ordering constraint. As an example, the set of packets in a particular TCP transfer sequence need to arrive in order, else the TCP logic will interpret the out of order delivery as congestion and slow the TCP transfer rate down.

[00135] While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.

Claims

CLAIMS What is claimed is:

1. A method executed by a network device, the method for generating an intermediate representation of platform independent routing information for a network, the intermediate representation to be utilized to support multi-level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging, the method comprising:

selecting (205) a next hop in the routing information;

checking (213) whether all vias of the selected nexthop have completed intermediate representation; and

combining (215) an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

2. The method of claim 1, further comprising:

checking (209) whether the selected next hop has vias; and

generating an intermediate representation for the selected nexthop from flattened path set.

3. The method of claim 1, further comprising:

determining (307) a stage of the selected nexthop base on whether the nexthop is a terminus, platform limitations or optimization parameter.

4. The method of claim 1, wherein the intermediate representation is at least one protection table.

5. The method of claim 1, further comprising:

creating a flattened next hop chain for each flattened path set in the protection table.

6. A network device for generating an intermediate representation of platform independent routing information for a network, the intermediate representation to be utilized to support multi-level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging, the network device comprising: a non-transitory machine-readable medium (718) having stored therein a representation transformer (791); and

a processor (712) coupled to the non-transitory machine-readable medium, the processor to execute the representation transformer, the representation transformer to select a next hop in the routing information, to check whether all vias of the selected nexthop have completed intermediate representation, and to combine an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

7. The network device of claim 6, wherein the representation transformer is further configured to check whether the selected next hop has vias, and to generate an intermediate representation for the selected nexthop from flattened path set.

8. The network device of claim 6, wherein the representation transformer is further configured to determine a stage of the selected nexthop base on whether the nexthop is a terminus, platform limitations or optimization parameter.

9. The network device of claim 6, wherein the intermediate representation is at least one protection table.

10. The network device of claim 6, wherein the representation transformer is further configured to create a flattened next hop chain for each flattened path set in the protection table.

11. A control plane device configured to implement at least one centralized control plane for a software defined networking (SDN) network, the centralized control plane configured to execute a method for generating an intermediate representation of platform independent routing information for a network, the intermediate representation to be utilized to support multi-level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging, the control plane device comprising:

a non-transitory machine-readable medium (848) having stored therein a representation transformer (791); and

a processor (842) coupled to the non-transitory machine-readable medium, the processor to execute the representation transformer, the representation transformer to select a next hop in the routing information, to check whether all vias of the selected nexthop have completed intermediate representation, and to combine an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

12. The control plane device of claim 11, wherein the representation transformer is further configured to check whether the selected next hop has vias, and to generate an intermediate representation for the selected nexthop from flattened path set.

13. The control plane device of claim 11, wherein the representation transformer is further configured to determine a stage of the selected nexthop base on whether the nexthop is a terminus, platform limitations or optimization parameter.

14. The control plane device of claim 11, wherein the intermediate representation is at least one protection table.

15. The control plane device of claim 11, wherein the representation transformer is further configured to create a flattened next hop chain for each flattened path set in the protection table.

16. A computing device implementing a plurality of virtual machines for implementing network function virtualization (NFV), wherein a virtual machine from the plurality of virtual machines is configured to execute a method for generating an intermediate representation of platform independent routing information for a network, the intermediate representation to be utilized to support multi-level fast reroute (FRR) in the network device where the network device has a fixed forwarding block that does not support FRR or where the forwarding in the network device is optimized to use a dynamically established staging, the computing device comprising:

a non-transitory machine-readable medium (748) having stored therein a representation transformer (791); and

a processor (742) coupled to the non-transitory machine-readable medium, the processor to execute the representation transformer, the representation transformer to select a next hop in the routing information, to check whether all vias of the selected nexthop have completed intermediate representation, and to combine an intermediate representation of each via of the selected nexthop to form an intermediate representation of the selected nexthop that is restricted by a platform of the network device or an optimization parameter for the network device.

17. The computing device of claim 16, wherein the representation transformer is further configured to check whether the selected next hop has vias, and to generate an intermediate representation for the selected nexthop from flattened path set.

18. The computing plane device of claim 16, wherein the representation transformer is further configured to determine a stage of the selected nexthop base on whether the nexthop is a terminus, platform limitations or optimization parameter.

19. The computing device of claim 16, wherein the intermediate representation is at least one protection table.

20. The computing device of claim 16, wherein the representation transformer is further configured to create a flattened next hop chain for each flattened path set in the protection table.