WO2020100150A1

WO2020100150A1 - Routing protocol blobs for efficient route computations and route downloads

Info

Publication number: WO2020100150A1
Application number: PCT/IN2018/050737
Authority: WO
Inventors: Anupkumar T
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2018-11-13
Filing date: 2018-11-13
Publication date: 2020-05-22
Anticipated expiration: 2021-05-13

Abstract

A method and system for reducing compute and bandwidth usage for routing information base configuration using a blob structure to track common network paths. The method includes receiving a route advertisement indicating a destination is reachable by a router via a path with a set of attributes, searching a blob database to identify a blob structure associated with the path with the set of attributes, and linking the destination to a matching blob structure with the path with the set of attributes.

Description

ROUTING PROTOCOL BLOBS FOR EFFICIENT ROUTE COMPUTATIONS AND

ROUTE DOWNLOADS

TECHNICAL FIELD

[0001] Embodiments of the invention relate to the field of routing table management; and more specifically, to the efficient grouping of routing information to minimize route computations in a network.

BACKGROUND ART

[0002] Devices in a network exchange routing information to enable the computation of routes to other destinations in the network. Generally, a network device, such as a router implementing the border gateway protocol (BGP), will compute a route to each possible destination in the network. The route computation results for all destinations will then be stored in the form of a routing table. For example, a BGP router R1 can learn a route to a destination D1 from its BGP peer router RX. The learnt route consists of the destination Dl, the peer address (e.g., an Internet Protocol (IP) address) for RX who is advertising the route to destination Dl, and the attributes A1 of the path from peer router RX to destination DL Attributes A1 can include path characteristics or metrics such as bandwidth, latency, administrative policies (e.g., applicable traffic management policies) and similar characteristics. In this example, if another destination D2 is also learnt from the same peer router RX, and if the path from RX to D2 has the same attributes Al, then the router R1 is said to have learnt two destinations from the same peer RX, with the same path attributes Al being common to both destinations. The router R1 would compute best paths to Dl and D2 and store them as two separate entries in the local routing table. Both destinations Dl and D2 are known by router R1 to be reachable over paths having the same attributes (Al), however, R1 would still do separate best path computations for destinations Dl and D2.

[0003] Best path computation algorithms will reach the same result for two destinations when the known paths to each destination have the same attributes. For example, in BGP’s best path computation the attributes influence decision making, and the same attributes give the same results. Thus, the router R1 makes the same best path computation for Dl and D2 with the same result in the given example. The general efficiency of this path computation process in a network like the Internet is 1:1 with a number of destinations and the number of best path computations. Similarly, the number of entries in the routing table is equal to the number of destinations. As a result, the bandwidth usage and compute required to do best path computations increases as the number of destinations increases. Many networks have a large number of destinations and therefore incur significant.

SUMMARY

[0004] In one embodiment, a method is provided for reducing compute and bandwidth usage for routing information base configuration using a blob structure to track common network paths. The method includes receiving a route advertisement indicating a destination is reachable by a router via a path with a set of attributes, searching a blob database to identify a blob structure associated with the path with the set of attributes, and linking the destination to a matching blob structure with the path with the set of attributes.

[0005] In another embodiment, a network device executes the method for reducing compute and bandwidth usage for routing information base configuration using a blob structure to track common network routes. The network device includes a non-transitory computer-readable medium having stored therein a routing protocol manager, and a processor coupled to the non-transitory computer-readable medium. The processor executes the routing protocol manager. The routing protocol manager receives a route advertisement indicating a destination is reachable by a router via a path with a set of attributes, searches a blob database to identify a blob structure associated with the path with the set of attributes, and links the destination to a matching blob structure with the path with the set of attributes.

[0006] In a further embodiment, a non-transitory computer-readable medium has stored therein a set of instruction, which when executed by a computing system cause the computing system to perform a set of operations to implement a method for reducing compute and bandwidth usage for routing information base configuration using a blob structure to track common network routes. The set of operations includes receiving a route advertisement indicating a destination is reachable by a router via a path with a set of attributes, searching a blob database to identify a blob structure associated with the path with the set of attributes, and linking the destination to a matching blob structure with the path with the set of attributes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] 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: [0008] Figure 1 is a diagram of one embodiment of an example network in which the embodiments can operate.

[0009] Figure 2 is a diagram of one embodiment of a representation of the routing information for the example network.

[0010] Figure 3 is a diagram of routing information entries that are downloaded by the routing protocol to the routing information base (RIB) of the router.

[0011] Figure 4 is a diagram of one embodiment of a blob structure representing routing information.

[0012] Figure 5 is a diagram of an example network topology along with a comparison of a basic routing table and a blob structured routing table.

[0013] Figure 6 is a flowchart of an update process for a blob structured routing table.

[0014] Figure 7 is a diagram of an add to a blob structure

[0015] Figure 8 is a flowchart of a deletion process for a blob structured routing table.

[0016] Figure 9 is a diagram of a deletion applied to a blob structure.

[0017] Figure 10 is a diagram of a blob structure supporting a multipath routing information.

[0018] Figure 11A 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.

[0019] Figure 11B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.

[0020] Figure 11C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.

[0021] Figure 1 ID 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.

[0022] Figure 11E 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.

[0023] Figure 11F 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.

[0024] Figure 12 illustrates a general-purpose control plane device with centralized control plane (CCP) software 1250), according to some embodiments of the invention.

DETAILED DESCRIPTION

[0025] The following description describes methods and apparatus for improving the efficiency of routing information computation and storage. 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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, solid state drives, 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 (e.g., wherein a processor is a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, other electronic circuitry, a combination of one or more of the preceding) 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 non-volatile 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) (NI(s)) to establish network connections (to transmit and/or receive code and/or data using propagating signals) with other electronic devices. For example, the set of physical NIs (or the set of physical NI(s) in combination with the set of processors executing code) may perform any formatting, coding, or translating to allow the electronic device to send and receive data whether over a wired and/or a wireless connection. In some embodiments, a physical NI may comprise radio circuitry capable of receiving data from other electronic devices over a wireless connection and/or sending data out to other devices via a wireless connection. This radio circuitry may include transmitter(s), receiver(s), and/or transceiver(s) suitable for radiofrequency communication. The radio circuitry may convert digital data into a radio signal having the appropriate parameters (e.g., frequency, timing, channel, bandwidth, etc.). The radio signal may then be transmitted via antennas to the appropriate recipient(s). In some embodiments, the set of physical NI(s) may comprise network interface controller(s) (NICs), also known as a network interface card, network adapter, or local area network (LAN) adapter. The NIC(s) may facilitate in connecting the electronic device to other electronic devices allowing them to communicate via wire through plugging in a cable to a physical port connected to a NIC. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0030] 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). A network element, as used herein, is a component or function that is executed by a network device or similar computing device to forward data traffic across a network.

[0031] In a complex and highly shared network topology, such as the Internet, the number of destinations that a given network element can potentially reach is extremely large compared to the number of unique paths (i.e. paths with differing sets of attributes), through which the destinations can be reached. For example, in a border gateway protocol-based topology, BGP route advertisements are received at BGP routers indicating the possible set of destinations that can be reached through the advertising BGP routers. Attributes as used herein, refer to any path characteristics or metrics such as bandwidth, latency, administrative policies (e.g., applicable traffic management policies) and similar characteristics. The number of routes with differing attributes to reach the advertising BGP routers however is significantly less than the number of advertised destinations. The number of unique paths to reach the possible destinations in a network depends mainly on the number of interconnections between the network element computing a route and the advertising network element as well as the applicable set of attributes for the routes. For example, in the case of BGP, the number of unique paths would be based on the number of autonomous systems (AS’es) and the number of policies configured in the BGP network. In the Internet, the number of path computations should‘not’ be a function of the number of destinations. Instead it should be a function of the number of path attributes in the Internet. The embodiments provide a process and system for reducing the number of path computations for a routing protocol and the number of paths download messages from the routing protocol to the local RIB of the router, each being a function of the number of path attributes rather than the number of destinations. The embodiments are described in relation to Internet Protocol (IP) based networks by way of example, but are applicable to any network where the number of destinations is very large relative to the number of paths in the network.

[0032] The embodiments, identify the common set of attributes in the arriving path advertisements, group the destinations mentioned in the path advertisements by their common set of peers and attributes, using a blob structure, run best path computations on each of the blob structures, and configure forwarding tables using the best paths grouped according to their blob structures. The blob structure is a data structure used to manage groupings of destinations with identical routing information such as identical sets of paths, path attributes, and advertising network elements. The blob structure can be a radix tree, a hash table or any other data structure that can support associating multiple destinations to a shared set of paths, attributes, and or advertising routers. Thus, the embodiments can provide an exponential reduction in the number of path computations, leading to better compute resource utilization. The embodiments also provide an exponential reduction in number of forwarding table configuration messages (e.g., inter-process communication (IPC) messages). These have a profound impact on the convergence of a routing information base (RIB), which impacts overall routing/forwarding efficiency of a network element.

[0033] For a destination whose reachability messages have arrived on a set of P paths, P- 1 comparisons are required to choose the best path. In the embodiments, for N such destinations that have arrived on the same set of P paths, the (P-1) comparisons are not be done N times. Thus, with the embodiments, only P-1 computations are executed in comparison to N*(P-1) where the optimizations of the embodiments are not implemented. The problem of repeated N*P-1 computations arises from the fact that the N destinations that are learnt over the same set of P paths, are being represented internally as if there are P different paths for each destination N. The embodiments identify that there are P common paths, that are shared by all N destinations. The embodiments recognize the commonality of the network topology to address this redundant computation problem.

[0034] In the case of routing in the Internet, for example using BGP, the Internet is organized as a set of autonomous systems (AS). The number of paths and attribute-sets depends mainly on the number of interconnections between AS’es and the number of administrative policies applied by AS administrators that modify the attributes of the BGP advertisements. The number of destinations is extremely large compared to the number of paths and attribute- sets through which the BGP advertisements of those destinations arrive at BGP routers. Thus, 1 million destinations in the Internet will not have 1 million unique AS paths, or 1 million unique policies. Hence, 1 million destinations will not have 1 million unique attribute- sets. Therefore, 1 million destinations do not need 1 million computations. For example, there were approximately 20,000 unique AS paths in the Internet core that are shared by 600,000 IPv4 (Internet Protocol version 4) BGP prefixes in early 2018. Thus, 600,000 IPv4 destinations can be reached via 20,000 unique paths. The embodiments avoid executing the best path computations 600,000 times, when it can be reduced to 20,000 computations.

[0035] Figure 1 is a diagram of one embodiment of an example network in which the embodiments can operate. In this simplified network topology, which is provided for sake of illustration and not by way of limitation. A network element, e.g., a router Rl, is in communication with two other network elements, e.g., routers RX and RY. Routers RX and RY are in communication with destinations D1 and D2, which can be any type of address or address prefix. Routers RX and RY are in communication with the destinations D1 and D2 via two paths having differing sets of attributes labeled A1 and A2. The peer routers RX and RY will each separately advertise the reachability of the same destinations D1 and D2 with different attributes. RX will advertise D1 and D2 being reachable with a path having attributes Al. RY will advertise D1 and D2 being reachable with a path having attributes A2. In this case, router Rl has two paths to reach each of destinations D1 and D2. The first path is via RX, and the second path is via RY, with corresponding path attributes Al & A2, as illustrated.

[0036] Figure 2 is a diagram of one embodiment of a representation of the routing information for the example network. The diagram illustrates that the destination D1 is associated with routers RX and RY indicating that D1 is reachable via these routers. Similarly, destination D2 is associated with both routers RX and RY. The attributes for reaching each destination are associated with the router that advertised the path. Thus, a path with attributes Al are associated with router RX and a path with attributes A2 are associated with router RY. The illustration of this set of relationships makes it clear that destination D1 and destination D2 have the same routing information. The embodiments recognize this redundancy and avoid storing the routing information more than once or using it more than once to make a path computation.

[0037] Without the embodiments, the router Rl performs a best path computation, Rl walks or traverses the above routing information, e.g., in a routing database, and for each destination, R1 performs independent computations to choose the best among the two paths. For destination Dl, R1 may choose RX as the best path if the attributes A1 are preferred over the attributes A2 associated with RY. As a result, R1 would download a nexthop of RX into its routing information base (RIB). For destination D2, which has the path options with the same attributes, router R1 will again perform the same computations as it did for destination Dl to choose the best among the two path options. R1 will again choose RX as the best path, and then download the nexthop RX, and attributes A1 to RIB for destination D2. In this process of best path computations, the second computation for destination D2 is run on exactly the same data as the first computation that happened for destination Dl. In both cases, the data-set (attributes) that is being processed for the available paths is the same.

[0038] The embodiments optimize this process by recognizing that destinations (e.g., Dl and D2) that share the same attributes, should be subjected to only one best path computation. In other words, a single best path computation is performed for a group of destination with a shared set of available paths and attributes. Similarly, the download of each of the selected paths for the respective destination into the local RIB of the network element contains exactly the same attribute and nexthop information. The embodiments recognize this redundancy and optimize the process such that destinations (e.g., Dl and D2) that share the same attributes, should be downloaded to the local RIB without repeating the attributes with each destination . Figure 3 is an example of two IPC messages downloaded to a local RIB of router R1 for the example network topology. As can be seen, the content of these messages is the same except for the difference in the destination field.

[0039] The embodiments eliminate the redundant path computations and redundant downloads to the RIB, when multiple destinations have a shared set of available paths with the same set of attributes. The embodiments provide a new routing database architecture that takes commonality of data into consideration to eliminate these inefficiencies. The embodiments employ a data structure referred to as a‘blob structure’ to manage groupings of destinations with identical routing information such as identical sets of paths, path attributes, and advertising network elements.

[0040] Figure 4 is a diagram of a blob structure representing routing information. The illustrated blob structure shows a representation of the routing information for destinations Dl and D2 in the example network topology of Figure 1. In this example, the routing protocol (e.g., BGP) can avoid the use and storage of redundant route computations, by grouping the shared routing information for a set of destinations. In this example, destinations D1 and D2 can share the composite routing information that represents the router peers RX and RY advertising the destinations Dl and D2, along with their respective path attributes A1 & A2. The blob structure is composed of this composite information. A blob structure is a group of peers or paths and attribute -sets for these paths that can be shared by many destinations/prefixes. A collection of blob structures can be stored as a blob structured based routing table in the form of a radix tree, a hash table or any other data structure that can support associating multiple destinations to a shared set of paths, attributes, and or advertising routers. As can be seen in the example illustration, both destinations in the example network topology can be represented in the form a traditional routing table where in each node, representing a destination IP address, contains a pointer to a single blob structure that represents the advertising routers RX and RY, which advertised paths with attributes A1 and A2, respectively, for destinations D1 and D2.

[0041] The destinations, blob structures and paths/attributes can be stored in any type of data structures either together or independently. In the illustrated example, the destinations are stored in a radix tree. The blob structures are stored in a separate searchable blob database. The paths and attributes are stored in a separate searchable database. This data management scenario is provided by way of example and not limitation. One skilled in the art would understand that other similar data storage schemes can be utilized.

[0042] Figure 5 is a diagram of an example network topology and a set of entries in a basic routing table and a blob structured routing table. The example network 501 in Figure 5 is a complex example with a router R that has peers RZ, RY, and RX. Routers RZ, RY, and RX are able to reach a set of destinations D1-D8 via a network. Each of the peer routers RX, RY, and RZ is in communication with different combinations of the destinations via multiple paths with differing attributes. Router RZ is able to reach destination D4 via a path with attribute si and destination D8 via a path with attribute s2. Router RY is able to reach destinations D1-D3 via a path with attributes si and destinations D5-D7 via a path with attributes s2. Router RX is able to reach destinations D1-D8 via a path with attributes si.

[0043] A conventional routing table 503 records the advertised routing information that is received from each of the peer routers RZ, RY, and RX. The router R also associates each of the reachable destinations with the advertising peer router, and the attributes of the path to the corresponding peer router. As shown in the routing table, an entry exists for each of the destinations D1 to D8. Destinations D1 to D8 are all reachable via peer router RX where the path to RX has attribute set si. Destinations D4 and D8 are also reachable via peer router RZ where the path to RZ has an attribute set s3. The Destinations D2-D3, D5, and D6 are reachable via the peer router RY via a path with attributes s2. While each of the destinations in this example are reachable by two peer routers, the embodiments are applicable to any network topology where a destination can be reachable via any number of different peer routers or similar network elements.

[0044] A blob structured routing table 505 groups the destinations into blob structures based on common routing information. Thus, in this example destinations D1 -D3 and D5- D7 have a common set of paths and attributes, specifically each of these destinations is reachable via peer router RX with path attributes si and via peer router RY with path attributes s2. Similarly, destinations 4 and 8 have common routing information. Each of these destinations are reachable via peer router RX with path attributes si and via peer RZ with path attributes s3. This illustrates the reduction in redundant routing information. When best path computations are performed, a single computation can be performed per group. For example, for blob structure 1 a best path computation compares a path via RX having attributes si with a path via RY having attributes s2. The same path is selected for all of the associated destinations D1-D3 and D5-D7. A similar best path computation is made for blob structure 2 to select from a path via RX with attribute s i and a path via RY with attribute s2 for destinations D4 and D8.

[0045] 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.

[0046] Figure 6 is a flowchart of an add process for a blob structured routing table. The add process is initiated in response to a routing protocol receiving an advertisement of the reachability of a destination (Block 601). The advertisement can include routing information including an advertising router and attributes of the path to the advertising router and/or destination. For example, a new BGP route advertisement can be received in which a destination Dl l is reachable via peer router RX with path attribute- set si. The addition process then checks whether an entry in the routing table exists with matching routing information. A search of the routing table is conducted to find the destination (Block 603). If no match is found (Block 605), it means that the router has learnt about the destination for the first time. A new node is created in the routing table for the destination (Block 609). Then a search of the blob database is conducted to find a blob having matching advertising router and path attribute information (Block 611). If a match is found, then the process completes (Block 623). If no match is found, then this indicates that the router has learnt about the path attribute set from the advertising peer router for the first time. A new blob structure is created in the blob database, with the advertised peer router information and path attribute set as its elements (Block 613). The destination node in the routing table is linked to the blob structure, thereby completing the process of addition of the first path for a destination node (Block 615).

[0047] If a match is found in the routing table for an advertised destination (Block 605), then the router has previously learnt about this destination. Thus, a blob structure should exist that contains the peer routers from which the destination was previously learnt. Blob structures linked to the destination are searched for matching peer router and path attributes (Block 607). If a match is found (Block 617), then the router has previously learnt the advertising router and path attributes and the process completes (Block 625). If no match is found (Block 617), then it means that the router has learnt about the destination from the advertising peer router with this advertisement. So, the destination node is unlinked from the existing blob structure (Block 619). Then, the router looks for a blob structure that contains all the previous routing information (i.e., advertising peers and path attributes) and the new peer with its path attribute set (621). If no match is found, then a new blob structure is created in the blob database (Block 613), and then, the destination node is linked to the new blob structure (Block 615). If a destination is already linked to a blob structure with matching routing information, then the process completes (Block 621).

[0048] Figure 7 is a diagram of an add to a blob structure. In the illustrated example, the existing blob structure relates a destination D10 with a peer router RX that is associated with path attributes S 1. In the case of an addition of a destination Dl l that is reachable via peer router RX with path attributes SI, the blob structure can be updated to reference destination Dl l.

[0049] Figure 8 is a flowchart of a deletion process for a blob structured routing table. The deletion process is initiated in response to a routing protocol receiving an advertisement of a destination that is no longer reachable (Block 801). The advertisement can include routing information including an advertising router and attributes of the path to the advertising router and/or destination. For example, a new BGP route advertisement can be received in which a destination D3 is unreachable via peer router RX with path attribute-set si. The deletion process then checks whether an entry in the routing table exists with matching routing information (Block 803). For example, a search of the routing table can be conducted to find destination D3. If no match is found (Block 805), then the advertisement can be discarded (Block 807). If a match is found (Block 805), then its corresponding blob structure is examined (Block 809). If the advertising router is the only peer in the blob structure (Block 811), then it means that the last known path for destination is being withdrawn. So, the destination is removed from the routing table (Block 813). If the destination was the last destination that was using the blob structure (Block 817), then the blob structure is also removed from the blob database (Block 831), thereby completing the process of deletion. If the blob structure has other peers, then it means that only one of the known paths for the destination is being withdrawn. So, the link from destination to the blob structure is removed (Block 815).

[0050] A new blob structure that has the other peers (excluding the deleted advertising router) and their attribute- sets is searched in the blob database (Block 819). If a match is found (Block821), then the destination in the routing table is now linked to this blob structure (Block823), thereby completing the process of deletion of the destination. If a match is not found (Block 821), then a new blob structure is created that has the other peers (excluding the deleted peer) and their attribute-sets, and the destination in the routing table is linked to this blob structure (Block 825).

[0051] Similarly, advertisement of a destination from a peer router with new/changed path attributes will be handled in the same manner. This change in routing information leads to movement of the destination to a different or new blob structure. The deletion process functions to find the blob structure with the complete match in routing information and associates the destination with it.

[0052] Figure 9 is a diagram of a deletion applied to a blob structure. In the illustrated example, a BGP route withdrawal is received. The BGP route withdrawal indicates that destination D3 is deleted, i.e., unreachable, by peer router RX. In this case, the destination D3 gets removed from a blob structure with the routing information associating peer Router RX with path attribute S 1. This removal of destination D3 does not affect other destinations in the blob structure. In this example, destination D3 is still advertised by RY with path attribute SI. The deletion process searches for an existing blob structure that contains the routing information of peer router RY and path attribute 1 only. Since the routing table in this example does not include such a blob structure, a new blob structure containing peer router RY with path attribute S 1 can be created, and destination D3 is mapped to the new blob strueturel l. [0053] Figure 10 is a diagram of a blob structure supporting a multipath routing information. In some routing protocols, it is possible for a peer router to advertise more than one path for reaching a destination. For example, the base BGP rule allows a BGP router to advertise only one path to a BGP peer. BGP Addpaths, RFC 7911, allows a BGP router to advertise multiple paths to a BGP peer. Each path advertisement from the BGP router will carry a unique Path-id that differentiates it from other paths advertised from that router. In such cases, the blob structures will enable the association of multiple paths with an advertising peer router. For example, a blob structure can support the BGP Addpaths RFC and use path-id so that multiple paths from a peer can be included in the blob structure.

[0054] In the illustrated example, if three destination Dl, D2, D3 are received from two peer routers RX and RY such that each peer advertises two paths, then the blob structure can reference four different paths and associated path attributes. The two paths from RX will have unique path -ids. The two paths from RY will have unique path-ids. Route computation is still done only once on the blob structure, and it will select the best path in the blob structure, i.e., one of the four available paths.

[0055] Figure 11A 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 11A shows NDs l lOOA-H, and their connectivity by way of lines between 1100A-1100B, l lOOB-l lOOC, 1100C-1100D, 1100D- 1100E, 1100E-1100F, 1100F-1100G, and 1100A-1100G, as well as between 1100H and each of 1100A, 1100C, 1100D, and 1100G. 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 1100A, 1100E, and 1100F 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).

[0056] Two of the exemplary ND implementations in Figure 11A are: 1) a special-purpose network device 1102 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general-purpose network device 1104 that uses common off-the-shelf (COTS) processors and a standard OS.

[0057] The special-purpose network device 1102 includes networking hardware 1110 comprising a set of one or more processor(s) 1112, forwarding resource(s) 1114 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 1116 (through which network connections are made, such as those shown by the connectivity between NDs 1100A-H), as well as non-transitory machine readable storage media 1118 having stored therein networking software 1120. During operation, the networking software 1120 may be executed by the networking hardware 1110 to instantiate a set of one or more networking software instance(s) 1122. Each of the networking software instance(s) 1122, and that part of the networking hardware 1110 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) 1122), form a separate virtual network element 1130A-R. Each of the virtual network element(s) (VNEs) 1130A-R includes a control communication and configuration module 1132A-R (sometimes referred to as a local control module or control communication module) and forwarding table(s) 1134A-R, such that a given virtual network element (e.g., 1130A) includes the control communication and configuration module (e.g., 1132A), a set of one or more forwarding table(s) (e.g., 1134A), and that portion of the networking hardware 1110 that executes the virtual network element (e.g., 1130A).

[0058] The special-purpose network device 1102 is often physically and/or logically considered to include: 1) a ND control plane 1124 (sometimes referred to as a control plane) comprising the processor(s) 1112 that execute the control communication and configuration module(s) 1132A-R; and 2) a ND forwarding plane 1126 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 1114 that utilize the forwarding table(s) 1134A-R and the physical NIs 1116. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 1124 (the processor(s) 1112 executing the control communication and configuration module(s) 1132A-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) 1134A-R, and the ND forwarding plane 1126 is responsible for receiving that data on the physical NIs 1116 and forwarding that data out the appropriate ones of the physical NIs 1116 based on the forwarding table(s) 1134A-R.

[0059] Figure 1 IB illustrates an exemplary way to implement the special-purpose network device 1102 according to some embodiments of the invention. Figure 11B shows a special- purpose network device including cards 1138 (typically hot pluggable). While in some embodiments the cards 1138 are of two types (one or more that operate as the ND forwarding plane 1126 (sometimes called line cards), and one or more that operate to implement the ND control plane 1124 (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 multiapplication 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 1136 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[0060] Returning to Figure 11 A, the general-purpose network device 1104 includes hardware 1140 comprising a set of one or more processor(s) 1142 (which are often COTS processors) and physical NIs 1146, as well as non-transitory machine-readable storage media 1148 having stored therein software 1150. During operation, the processor(s) 1142 execute the software 1150 to instantiate one or more sets of one or more applications 1164A-R. 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 1154 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 1162A-R called software containers that may each be used to execute one (or more) of the sets of applications 1164A-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 1154 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 1164A-R is run on top of a guest operating system within an instance 1162A-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 unikemel(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 unikemel can be implemented to run directly on hardware 1140, directly on a hypervisor (in which case the unikemel is sometimes described as running within a LibOS virtual machine), or in a software container, embodiments can be implemented fully with unikemels running directly on a hypervisor represented by virtualization layer 1154, unikemels running within software containers represented by instances 1162A-R, or as a combination of unikemels and the above- described techniques (e.g., unikemels and virtual machines both run directly on a hypervisor, unikemels and sets of applications that are run in different software containers).

[0061] The instantiation of the one or more sets of one or more applications 1164A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 1152. Each set of applications 1164A-R, corresponding virtualization constmct (e.g., instance 1162A-R) if implemented, and that part of the hardware 1140 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) 1160A-R. The set of applications can include the routing protocol manager 1165, which implements the processes for managing a blob structure-based routing table as described herein above.

[0062] The virtual network element(s) 1160A-R perform similar functionality to the virtual network element(s) 1130A-R - e.g., similar to the control communication and configuration module(s) 1132A and forwarding table(s) 1134A (this virtualization of the hardware 1140 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 1162A-R corresponding to one VNE 1160A-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 1162A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikemels are used. [0063] In certain embodiments, the virtualization layer 1154 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 1162A-R and the physical NI(s) 1146, as well as optionally between the instances 1162A-R; in addition, this virtual switch may enforce network isolation between the VNEs 1160A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).

[0064] The third exemplary ND implementation in Figure 11A is a hybrid network device 1106, 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 1102) could provide for para-virtualization to the networking hardware present in the hybrid network device 1106.

[0065] 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) 1130A-R, VNEs 1160A-R, and those in the hybrid network device 1106) receives data on the physical NIs (e.g., 1116, 1146) and forwards that data out the appropriate ones of the physical NIs (e.g., 1116, 1146). 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.

[0066] Figure 11C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention. Figure 11C shows VNEs 1170A.1- 1170A.P (and optionally VNEs 1170A.Q-1170A.R) implemented in ND 1100A and VNE 1170H.1 in ND 1100H. In Figure 11C, VNEs 1170A.1-P are separate from each other in the sense that they can receive packets from outside ND 1100A and forward packets outside of ND 1100A; VNE 1170A.1 is coupled with VNE 1170H.1, and thus they communicate packets between their respective NDs; VNE 1170A.2-1170A.3 may optionally forward packets between themselves without forwarding them outside of the ND 1100A; and VNE 1170A.P may optionally be the first in a chain of VNEs that includes VNE 1170A.Q followed by VNE 1170A.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 11C 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).

[0067] The NDs of Figure 11 A, 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 11A may also host one or more such servers (e.g., in the case of the general purpose network device 1104, one or more of the software instances 1162A-R may operate as servers; the same would be true for the hybrid network device 1106; in the case of the special-purpose network device 1102, one or more such servers could also be run on a virtualization layer executed by the processor(s) 1112); in which case the servers are said to be co -located with the VNEs of that ND.

[0068] A virtual network is a logical abstraction of a physical network (such as that in Figure 11 A) 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).

[0069] 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 an 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).

[0070] 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).

[0071] Fig. 1 ID illustrates a network with a single network element on each of the NDs of Figure 11 A, 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 11D illustrates network elements (NEs) 1170A-H with the same connectivity as the NDs 1 100A-H of Figure 11 A.

[0072] Figure 11D illustrates that the distributed approach 1172 distributes responsibility for generating the reachability and forwarding information across the NEs 1170A-H; in other words, the process of neighbor discovery and topology discovery is distributed.

[0073] For example, where the special-purpose network device 1102 is used, the control communication and configuration module(s) 1132A-R of the ND control plane 1124 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), Fabel Distribution Protocol (FDP), Resource Reservation Protocol (RSVP) (including RSVP-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 1170A-H (e.g., the processor(s) 1112 executing the control communication and configuration module(s) 1132A-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 1124. The ND control plane 1124 programs the ND forwarding plane 1126 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 1124 programs the adjacency and route information into one or more forwarding table(s) 1134A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 1126. 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 1102, the same distributed approach 1172 can be implemented on the general-purpose network device 1104 and the hybrid network device 1106. [0074] Figure 11D illustrates that a centralized approach 1174 (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 1174 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 1176 (sometimes referred to as an 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 1176 has a south bound interface 1182 with a data plane 1180 (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 1170A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 1176 includes a network controller 1178, which includes a centralized reachability and forwarding information module 1179 that determines the reachability within the network and distributes the forwarding information to the NEs 1170A-H of the data plane 1180 over the south bound interface 1182 (which may use the OpenFlow protocol). Thus, the network intelligence is centralized in the centralized control plane 1176 executing on electronic devices that are typically separate from the NDs.

[0075] For example, where the special-purpose network device 1102 is used in the data plane 1180, each of the control communication and configuration module(s) 1132A-R of the ND control plane 1124 typically include a control agent that provides the VNE side of the south bound interface 1182. In this case, the ND control plane 1124 (the processor(s) 1112 executing the control communication and configuration module(s) 1132A-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 1176 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 1179 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 1132A-R, in addition to communicating with the centralized control plane 1176, 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 1174, but may also be considered a hybrid approach). [0076] While the above example uses the special-purpose network device 1102, the same centralized approach 1174 can be implemented with the general purpose network device 1104 (e.g., each of the VNE 1160A-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 1176 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 1179; it should be understood that in some embodiments of the invention, the VNEs 1160A-R, in addition to communicating with the centralized control plane 1176, 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 1106. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general-purpose network device 1104 or hybrid network device 1106 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.

[0077] Figure 11D also shows that the centralized control plane 1176 has a north bound interface 1184 to an application layer 1186, in which resides application(s) 1188. The centralized control plane 1176 has the ability to form virtual networks 1192 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 1170A-H of the data plane 1180 being the underlay network)) for the application(s) 1188. Thus, the centralized control plane 1176 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). The set of applications 1188 can include the routing protocol manager 1165, which implements the processes for managing a blob structure based routing table as described herein above.

[0078] While Figure 11D shows the distributed approach 1172 separate from the centralized approach 1174, 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) 1174, 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 1174 but may also be considered a hybrid approach.

[0079] While Figure 11D illustrates the simple case where each of the NDs 1100A-H implements a single NE 1170A-H, it should be understood that the network control approaches described with reference to Figure 11D also work for networks where one or more of the NDs 1100A-H implement multiple VNEs (e.g., VNEs 1130A-R, VNEs 1160A- R, those in the hybrid network device 1106). Alternatively, or in addition, the network controller 1178 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 1178 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 1192 (all in the same one of the virtual network(s) 1192, each in different ones of the virtual network(s) 1192, or some combination). For example, the network controller 1178 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 1176 to present different VNEs in the virtual network(s) 1192 (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).

[0080] On the other hand, Figures 11E and 11F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 1178 may present as part of different ones of the virtual networks 1192. Figure 11E illustrates the simple case of where each of the NDs 1100A-H implements a single NE 1 170A-H (see Figure 11D), but the centralized control plane 1176 has abstracted multiple of the NEs in different NDs (the NEs 1170A-C and G-H) into (to represent) a single NE 11701 in one of the virtual network(s) 1192 of Figure 11D, according to some embodiments of the invention. Figure HE shows that in this virtual network, the NE 11701 is coupled to NE 1170D and 1170F, which are both still coupled to NE 1170E.

[0081] Figure 11F illustrates a case where multiple VNEs (VNE 1170A.1 and VNE 1170H.1) are implemented on different NDs (ND 1100 A and ND 1100H) and are coupled to each other, and where the centralized control plane 1176 has abstracted these multiple VNEs such that they appear as a single VNE 1170T within one of the virtual networks 1192 of Figure 11D, according to some embodiments of the invention. Thus, the abstraction of a NE or VNE can span multiple NDs. [0082] While some embodiments of the invention implement the centralized control plane 1176 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).

[0083] Similar to the network device implementations, the electronic device(s) running the centralized control plane 1176, and thus the network controller 1178 including the centralized reachability and forwarding information module 1179, 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 processor(s), a set or one or more physical NIs, and a non-transitory machine-readable storage medium having stored thereon the centralized control plane software. For instance, Figure 12 illustrates, a general- purpose control plane device 1204 including hardware 1240 comprising a set of one or more processor(s) 1242 (which are often COTS processors) and physical NIs 1246, as well as non-transitory machine-readable storage media 1248 having stored therein centralized control plane (CCP) software 1250.

[0084] In embodiments that use compute virtualization, the processor(s) 1242 typically execute software to instantiate a virtualization layer 1254 (e.g., in one embodiment the virtualization layer 1254 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 1262A-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 1254 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 1262A-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 unikemel can run directly on hardware 1240, directly on a hypervisor represented by virtualization layer 1254 (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 1262A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 1250 (illustrated as CCP instance 1276A) is executed (e.g., within the instance 1262A) on the virtualization layer 1254. In embodiments where compute virtualization is not used, the CCP instance 1276A is executed, as a unikernel or on top of a host operating system, on the“bare metal” general purpose control plane device 1204. The instantiation of the CCP instance 1276A, as well as the virtualization layer 1254 and instances 1262A-R if implemented, are collectively referred to as software instance(s) 1252.

[0085] In some embodiments, the CCP instance 1276 A includes a network controller instance 1278. The network controller instance 1278 includes a centralized reachability and forwarding information module instance 1279 (which is a middleware layer providing the context of the network controller 1178 to the operating system and communicating with the various NEs), and an CCP application layer 1280 (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 1280 within the centralized control plane 1176 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. The set of application layer 1288 can support the routing protocol manager 1265, which implements the processes for managing a blob structure based routing table as described herein above.

[0086] The centralized control plane 1176 transmits relevant messages to the data plane 1180 based on CCP application layer 1280 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 1180 may receive different messages, and thus different forwarding information. The data plane 1180 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.

[0087] 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).

[0088] 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.

[0089] 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.

[0090] However, when an unknown packet (for example, a“missed packet” or a“match- miss” as used in OpenFlow parlance) arrives at the data plane 1180, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 1176. The centralized control plane 1176 will then program forwarding table entries into the data plane 1180 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 1180 by the centralized control plane 1176, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

[0091] 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.

[0092] 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.

[0093] 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:

1. A method to track common network paths, the method comprising:

receiving a route advertisement indicating a destination is reachable by a router via a path with a set of attributes;

searching a blob database to identify a blob structure associated with the path with the set of attributes; and

linking the destination to a matching blob structure with the path with the set of attributes.

2. The method of claim 1, further comprising:

creating a new blob structure in the blob database, in response to finding no matching path.

3. The method of claim 1, wherein the blob structure correlates the path with the set of attributes with a plurality of destinations in a routing table where the plurality of destinations are reachable by the path with the set of attributes.

4. The method of claim 1, wherein the blob structure defines a relationship between paths in the network, and destinations reachable through the paths.

5. The method of claim 1, further comprising:

receiving another advertisement indicating a second destination is no longer reachable by a second router via a second path with a second set of attributes; searching the blob database for a second blob structure linked with the second destination reachable by the second router via a second node with the second set of attributes; and

removing the second destination from the second blob structure, in response to finding a match for the second destination and second path with the second set of attributes.

6. The method of claim 5, further comprising:

determining whether the second destination is reachable by additional routers via additional paths; and creating a third blob structure for the second destination including each of the additional routers and additional paths to the second destination.

7. The method of claim 1, wherein the advertisement is a border gateway protocol route update.

8. A network device to execute a method to track common network routes, the network device comprising:

a non-transitory computer-readable medium having stored therein a routing protocol manager; and

a processor coupled to the non-transitory computer-readable medium, the processor to execute the routing protocol manager, the routing protocol manager to receive a route advertisement indicating a destination is reachable by a router via a path with a set of attributes, to search a blob database to identify a blob structure associated with the path with the set of attributes, and to link the destination to a matching blob structure with the path with the set of attributes.

9. The network device of claim 8, wherein the routing protocol manager is further to create a new blob structure in the blob database, in response to finding no matching path.

10. The network device of claim 8, wherein the blob structure correlates the path with the set of attributes with a plurality of destinations in a routing table where the plurality of destinations are reachable by the path with the set of attributes.

11. The network device of claim 8, wherein the blob structure defines a relationship between paths in the network, and destinations reachable through the paths.

12. The network device of claim 8, wherein the routing protocol manager is further to receive another advertisement indicating a second destination is no longer reachable by a second router via a second path with a second set of attributes, to search the blob database for a second blob structure linked with the second destination reachable by the second router via a second node with the second set of attributes, and to remove the second destination from the second blob structure, in response to finding a match for the second destination and second path with the second set of attributes.

13. The network device of claim 12, wherein the routing protocol manager is further to determine whether the second destination is reachable by additional routers via additional paths, and to create a third blob structure for the second destination including each of the additional routers and additional paths to the second destination.

14. The network device of claim 8, wherein the advertisement is a border gateway protocol route update.

15. A non-transitory computer-readable medium having stored therein a set of instruction, which when executed by a computing system cause the computing system to perform a set of operations to implement a method to track common network routes, the set of operations comprising:

16. The non-transitory computer-readable medium of claim 15, having further instructions stored therein comprising:

17. The non-transitory computer-readable medium of claim 15, wherein the blob structure correlates the path with the set of attributes with a plurality of destinations in a routing table where the plurality of destinations are reachable by the path with the set of attributes.

18. The non-transitory computer-readable medium of claim 15, wherein the blob structure defines a relationship between paths in the network, and destinations reachable through the paths.

19. The non-transitory computer-readable medium of claim 15, having further instructions stored therein comprising: receiving another advertisement indicating a second destination is no longer reachable by a second router via a second path with a second set of attributes; searching the blob database for a second blob structure linked with the second destination reachable by the second router via a second node with the second set of attributes; and

20. The non-transitory computer-readable medium of claim 19, having further instructions stored therein comprising:

determining whether the second destination is reachable by additional routers via additional paths; and

creating a third blob structure for the second destination including each of the additional routers and additional paths to the second destination.