WO2018051172A1

WO2018051172A1 - Service function classifier bypass in software defined networking (sdn) networks

Info

Publication number: WO2018051172A1
Application number: PCT/IB2016/055587
Authority: WO
Inventors: Faseela K; Ashutosh Bisht
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-09-19
Filing date: 2016-09-19
Publication date: 2018-03-22

Abstract

A method is implemented by a controller in a Software Defined Networking (SDN) network to configure a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier. The method includes obtaining a translation rule for the flow, where the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow, transmitting bypass instructions to the switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation, and transmitting an indication to the service function classifier that the flow is to bypass the service function classifier.

Description

SERVICE FUNCTION CLASSIFIER BYPASS IN SOFTWARE DEFINED

NETWORKING (SDN) NETWORKS

TECHNICAL FIELD

[0001] Embodiments of the invention relate to the field of computer networks, and more specifically, to bypassing a service function classifier in a Software Defined Networking (SDN) network.

BACKGROUND

[0002] Software Defined Networking (SDN) is an approach to computer networking that employs a split architecture network in which the forwarding (data) plane is decoupled from the control plane. The use of a split architecture network simplifies the network devices (e.g., switches) implementing the forwarding plane by shifting the intelligence of the network into one or more controllers that oversee the switches. SDN facilitates rapid and open innovation at the network layer by providing a programmable network infrastructure.

[0003] A Service Function Chain (SFC) defines an ordered set of abstract service functions. A service function is a function that is responsible for specific treatment of received packets. A service function can act at various layers of a protocol stack (e.g., at the network layer or other Open Systems Interconnection (OSI) layers). A non-exhaustive list of abstract service functions includes firewalls, Deep Packet Inspection (DPI), Lawful Intercept (LI), server load balancing, and Network Address Translation (NAT).

[0004] In traditional non-SDN networks, building SFCs requires several manual steps such as configuring routing/switching policies and Access Control Lists (ACLs). Building and configuring SFCs is greatly simplified with SDN capabilities. In an SDN environment, the switches (e.g., OpenFlow switches) typically act as Service Function Forwarders (SFFs). An SFF is connected to one or more service functions (e.g., firewall, NAT) and is responsible for forwarding traffic to one or more of those service functions, as well as handling traffic coming back from those service functions.

[0005] In a typical SFC scenario, when a packet arrives at an SFF, the SFF classifies the packet based on SFC policy (e.g., which may classify the packet based on the contents of the header fields of the packet). Based on the results of the classification, the packet is assigned to an SFC and forwarded to the first service function of the SFC (which may be locally attached to the current SFF or attached to another SFF). After the first service function finishes processing the packet, the first service function forwards the packet back to the SFF to which the first service function is attached. A similar process is repeated until the packet traverses all the required service functions of the SFC.

[0006] The use of a Network Service Header (NSH) is becoming a popular solution to realize SFCs. This solution introduces a new header, called NSH, that is added onto packets. At ingress to an SFC-enabled domain, a classifier function (e.g., a service function classifier) classifies the packet and adds an NSH onto the packet based on the results of the classification. The NSH includes an indication of a Service Function Path (SFP) that is assigned to the packet. The SFP specifies a particular path in the network that the packet is to traverse. Once the NSH is added onto the packet, subsequent forwarding of the packet is based on the contents of the NSH. The use of an NSH eliminates the need to reclassify the packet at every SFF. An NSH thus provides the flexibility to classify packets independently from the controller that manages the SFCs. The coordination required between the SDN domain and the SFC domain is the common understanding of the SFPs.

[0007] The granularity of classification is determined by the capabilities of the classifier and the requirements of the SFC policy. For example, classification can be relatively coarse (e.g., all packets from a particular port are subject to a first SFC policy and directed into a first SFP) or can be relatively granular (e.g., all packets matching a particular 5-tuple are subject to a second SFC policy and directed into a second SFP). At ingress to the SFC-enabled domain, all packets belonging to a flow are forwarded to the classifier. When the classifier receives a packet, it adds an NSH onto the packet (e.g., based on the results of the classification) and forwards the packet based on the contents of the NSH.

SUMMARY

[0008] A method is implemented by a controller in a Software Defined Networking (SDN) network to configure a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier. The method includes obtaining a translation rule for the flow, where the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow, transmitting service function classifier bypass instructions to the switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation, and transmitting an indication to the service function classifier that the flow is to bypass the service function classifier. [0009] A network device configured to function as a controller in a Software Defined Networking (SDN) network to configure a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier. The network device includes a set of one or more processors and a non-transitory machine- readable storage medium having stored therein a service function classifier bypass component. The service function classifier bypass component, when executed by the set of one or more processors, causes the network device to obtain a translation rule for the flow, where the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow, transmit service function classifier bypass instructions to the switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation, and transmit an indication to the service function classifier that the flow is to bypass the service function classifier.

[0010] A non-transitory machine-readable medium has computer code stored therein, which when executed by a set of one or more processors of a network device functioning as a controller in a Software Defined Networking (SDN) network, causes the network device to perform operations for configuring a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier. The operations include obtaining a translation rule for the flow, where the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow, transmitting service function classifier bypass instructions to the switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation, and transmitting an indication to the service function classifier that the flow is to bypass the service function classifier.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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:

[0012] Fig. 1 is a diagram illustrating traffic flow in a network that implements service function chaining, according to some embodiments. [0013] Fig. 2 is a diagram illustrating translation services provided by a service function classifier, according to some embodiments.

[0014] Fig. 3 is a diagram illustrating packet processing operations in a network before service function classifier bypass for a flow is configured, according to some embodiments.

[0015] Fig. 4 is a diagram illustrating operations for configuring service function classifier bypass for a flow in a network, according to some embodiments.

[0016] Fig. 5 is a diagram illustrating packet processing operations in a network after service function classifier bypass for a flow has been configured, according to some embodiments.

[0017] Fig. 6 is a diagram illustrating operations for handling termination of a flow, according to some embodiments.

[0018] Fig. 7 is a flow diagram of a process for configuring a switch in an SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, according to some embodiments.

[0019] Fig. 8 is a flow diagram of a process for causing a flow in an SDN network to bypass a service function classifier, according to some embodiments.

[0020] Fig. 9 is a flow diagram of a process for processing a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, according to some embodiments.

[0021] Fig. 10A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some embodiments.

[0022] Fig. 10B illustrates an exemplary way to implement a special-purpose network device, according to some embodiments.

[0023] Fig. IOC illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled, according to some embodiments.

[0024] Fig. 10D 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.

[0025] Fig. 10E 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.

[0026] Fig. 10F 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.

[0027] Fig. 11 illustrates a general purpose control plane device with centralized control plane (CCP) software, according to some embodiments.

DETAILED DESCRIPTION

[0028] The following description describes methods and apparatus for bypassing a service function classifier in a Software Defined Networking (SDN) network. 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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).

[0034] Service function chaining enables the creation of composite (network) services that include an ordered set of service functions that must be applied to packets/frames/flows selected as a result of classification. At a high level, a Service Function Chain (SFC) is an abstracted view of a service that specifies the set of required service functions as well as the order in which they must be executed.

[0035] Fig. 1 is a diagram illustrating traffic flow in a network that implements service function chaining, according to some embodiments. The network supports the use of SFC encapsulations to realize service function chains and thus can be considered to be an SFC- enabled domain. An SFC encapsulation, as used herein, refers to an encapsulation that includes information regarding a Service Function Path (SFP) and/or an SFC. An SFP is a constrained specification of the path that a packet must traverse in order to realize an SFC. There may be multiple SFPs associated with a given SFC and these SFPs can have different levels of granularity. For example, there can be two SFPs associated with a given SFC, where the first SFP specifies the exact order of SFFs and service functions that the packet is to traverse, while the second SFP is less specific and defers to the SFFs as to the exact sequence that the packet is to traverse to realize the SFC. The SFC encapsulation may also include metadata (e.g., with data plane context information). In one embodiment, the SFC encapsulation is a Network Service Header (NSH).

[0036] As shown in the diagram, the network includes a service function classifier 120, Service Function Forwarders (SFFs) 130 (e.g., SFF 130A and SFF 130B), and service functions (SFs) 140 (e.g., SF 140A, SF 140B, and HOC). SF 140A and SF 140B are connected to SFF 130A, while SF 140B is connected to SFF 130B. It should be understood that the various entities in the network can be implemented by a dedicated physical network device or may be virtualized (e.g., using Network Function Virtualization (NFV)).

[0037] Service function classifier 120 is responsible for classifying packets based on SFC policies and for adding the appropriate SFC encapsulation onto packets based on the results of the classification. The SFC encapsulation added onto a packet may include an indication of an SFP assigned to the packet.

[0038] Each service function 140 is a function that is responsible for specific treatment of packets. Each service function 140 can act at various layers of a protocol stack (e.g., at the network layer or other Open Systems Interconnection (OSI) layers). Examples of service functions 140 include, but are not limited to, firewalls, Deep Packet Inspection (DPI), Lawful Intercept (LI), server load balancing, and Network Address Translation (NAT). A service function 140 can be realized as a virtualized element or a non-virtualized element. One or more service functions 140 can be embedded in the same network device and multiple occurrences of a particular service function 140 can exist in the same administrative domain. Each SFF 130 is responsible for forwarding packets to one or more service functions 140 connected thereto based on the contents of the SFC encapsulation, as well as handling packets coming back from the service functions 140.

[0039] An exemplary traffic flow in the network is shown in the diagram with a dashed line. As shown in the diagram, traffic enters the SFC-enabled domain through the service function classifier 120. The service function classifier 120 classifies the traffic (e.g., based on SFC policies) and adds an SFC encapsulation onto the traffic (more specifically, onto individual packets of the traffic) based on the results of the classification. The SFC encapsulation may include an indication of an SFP. Subsequent forwarding of the traffic within the SFC-enabled domain is based on the contents of the SFC encapsulation. In this example, the results of the classification indicate that the traffic is to be directed into an SFP that includes SF 140A, SF 140B, and SF 140C. The service function classifier 120 thus forwards the traffic to SFF 130A so that the traffic can be processed by SF 140A and SF 140B. SFF 130A forwards the traffic to SF 140A to be processed by SF 140A. Once SF 140A finishes processing the traffic, SF 140A forwards the traffic back to SFF 130A. SFF 130A then forwards the traffic to SF 140B to be processed by SF 140B. Once SF 140B finishes processing the traffic, SF 140B forwards the traffic back to SFF 130A. SFF 130A then forwards the traffic to SFF 130B so that the traffic can be processed by SF 140C. SFF 130B forward the traffic to SF 140C to be processed by SF 140C. Once SF 140C finishes processing the traffic, SF 140C forwards the traffic back to SFF 130B. SFF 130B then continues forwarding the traffic towards its destination.

[0040] Fig. 2 is a diagram illustrating translation services provided by a service function classifier, according to some embodiments. The service function classifier 120 accepts a packet as an incoming request (e.g., at ingress to the SFC-enabled domain or during reclassification). The service function classifier 120 classifies the packet to assign an SFP to the packet. The service function classifier 120 may classify the packet based on SFC policies configured by a network administrator or other criteria. For example, the SFC policies may dictate that packets having a particular 5-tuple (e.g., particular source IP address, destination IP address, protocol, source port, and destination port) are to be assigned to a particular SFP. Based on the results of the classification, the service function classifier 120 adds an SFC encapsulation onto the packet. The SFC encapsulation may include an indication of the particular SFP that is assigned to the packet. In one embodiment, the SFC encapsulation is an NSH. The NSH may include an indication of a service path identifier (ID) and an indication of a service index, where the service path ID identifies a particular SFP and the service index identifies the current location within the particular SFP. The service function classifier 120 then forwards the packet with the SFC encapsulation to the SFF 130 connected to the first service function 140 of the SFP. Subsequent forwarding of the packet within the SFC-enabled domain is based on the contents of the SFC encapsulation.

[0041] It is observed that once the service function classifier 120 determines the appropriate SFC encapsulation to add onto a packet, the same SFC encapsulation typically applies to any subsequent packets belonging to the same flow as the initial packet. In other words, the translation rule applied by a service function classifier 120 is typically fixed for packets belonging to the same flow.

[0042] In conventional SFC architectures, all packets that enter an SFC-enabled domain are initially forwarded to the service function classifier 120 so that an appropriate SFC

encapsulation can be added onto the respective packets. Packets that have been processed by the service function classifier 120 are then forwarded to the appropriate SFF 130 based on the contents of their respective SFC encapsulations. Having to initially forward every packet that enters the SFC-enabled domain to the service function classifier 120 adds additional latency and consumes additional bandwidth.

[0043] Embodiments described herein overcome the disadvantages of conventional techniques by allowing packets to bypass the service function classifier 120. Embodiments described herein make use of the observation that the translation rule applied by a service function classifier 120 (e.g., adding an SFC encapsulation onto packets) is typically fixed for packets belonging to the same flow. As such, once the service function classifier 120 determines the translation rule for a flow, the translation rule for the flow can be applied by other entities in the network (e.g., data plane switches) without having to involve the service function classifier 120, which allows packets belonging to the flow to bypass the service function classifier 120).

According to some embodiments, once the service function classifier 120 determines a translation rule for a flow (e.g., based on pre-configured SFC policy), the service function classifier 120 provides the translation rule for the flow to a controller. The translation rule for the flow may include an indication of a particular SFC encapsulation that is to be added onto packets belonging to the flow. The controller may then transmit service function classifier bypass instructions to a switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier 120, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to the contents of the SFC encapsulation. In this way, the switch is configured to process packets belonging to the flow (e.g., by adding an SFC encapsulation onto the packets) without involving the service function classifier 120. As a result, there is no longer a need for packets belonging to the flow (except the initial packet) to be processed by the service function classifier 120, and thus these packets can bypass the service function classifier 120. This reduces the latency for the packets belonging to the flow (except the initial packet) and reduces bandwidth consumption. Other embodiments are further described herein with reference to the accompanying drawings.

[0044] Fig. 3 is a diagram illustrating packet processing operations in a network before service function classifier bypass for a flow is configured, according to some embodiments. The network includes a controller 320 (e.g., SDN controller), a switch 330 (e.g., SDN switch) that is managed by the controller 320, and a service function classifier 120. In one embodiment, the controller 320 manages the switch 330 over a southbound interface using OpenFlow or other type of southbound communications protocol. The switch 330 is communicatively coupled to service function classifier 120.

[0045] Packet processing operations in the network before service function classifier bypass for the flow is configured will now be described with reference to the diagram. The switch 330 is initially configured to forward packets belonging to the flow to the service function classifier 120. The controller 320 may have previously transmitted traffic steering instructions 350 to the switch 330 that instruct the switch 330 to forward packets belonging to the flow to the service function classifier 120. At operation 1, the switch 330 receives a packet belonging to the flow. At operation 2, the switch 330 forwards the packet to the service function classifier 120 (e.g., according to traffic steering instructions 350).

[0046] In one embodiment, the service function classifier 120 maintains a translation table that includes translation rules for one or more flows. A translation rule for a particular flow includes an indication of the SFC encapsulation that is to be added onto packets belonging to that particular flow. When the service function classifier 120 receives an initial packet belonging to a new flow, the service function classifier 120 determines the appropriate SFC encapsulation that is to be added onto packets belonging to the flow (e.g., based on SFC policies). The service function classifier 120 may then add a translation rule for the flow to its translation table. For example, in response to receiving the packet (e.g., at operation 2), the service function classifier 120 may add a translation rule for the flow to which the packet belongs in its translation table, as shown below in Table I.

[0047] As shown, the translation table includes columns for flow identification, service path identifier, service index, and NSH operation. The flow identification column indicates one or more attributes that identify a flow. The service path identifier column indicates a service path identifier that identifies an SFP. The service index column indicates a service index that identifies the current location within the SFP. The NSH operation column indicates the NSH- related action to apply to packets. For purposes of illustration, the translation table is shown as using NSH as the SFC encapsulation. It should be understood, however, that the translation table can be adapted to be used with other types of SFC encapsulations.

[0048] The exemplary translation table shown in Table I includes a translation rule for a flow having source IP address of 10.1.1.1, destination IP address of 17.1.1.1, protocol of

Transmission Control Protocol (TCP), source port of 5123, and destination port of 80 (as indicated in the flow identification column). According to the translation rule for the flow, if the service function classifier 120 receives a packet belonging to the flow, the service function classifier 120 adds an NSH having service path identifier of 10 and service index of 10 onto that packet. For purposes of simplicity and clarity, a translation rule for a single flow is shown in Table I. It should be understood, however, that the translation table can include additional translation rules for other flows.

[0049] Once the service function classifier 120 adds the appropriate SFC encapsulation onto the packet (e.g., according to the translation rule), at operation 3, the service function classifier 120 forwards the packet with the SFC encapsulation back to the switch 330. At operation 4, the switch 330 forwards the packet with the SFC encapsulation along the appropriate SFP (e.g., the SFP indicated in the NSH).

[0050] Fig. 4 is a diagram illustrating operations for configuring service function classifier bypass for a flow in a network, according to some embodiments. At operation 1, once the service function classifier 120 determines the translation rule for the flow (e.g., the translation rule described with reference to Table I), the service function classifier 120 provides the translation rule for the flow to the controller 320. The translation rule includes an indication of an SFC encapsulation that is to be added onto packets belonging to the flow. At operation 2, the controller 320 transmits instructions to the switch 330 that instruct the switch 330 to stop forwarding packets belonging to the flow to the service function classifier 120, add the SFC encapsulation onto packets belonging to the flow, and forward packets belonging to the flow according to the contents of the SFC encapsulation (e.g., into the SFP indicated in the SFC encapsulation) (designated as "service function classifier bypass instructions"). The switch 330 may then be configured to implement the service function classifier bypass instructions (e.g., by generating flow entries that implement the service function classifier bypass instructions). At operation 3, the switch 330 transmits an indication to the controller 320 that service function classifier bypass for the flow has been configured (designated as "service function classifier bypass confirmation"). At operation 4, the controller 320 transmits an indication to the service function classifier 120 that service function classifier bypass for the flow has been configured (e.g., packets belonging to the flow are to bypass the service function classifier 120) (designated as "translation rule installed"). At operation 5, the service function classifier 120 removes the translation rule for the flow from its translation table.

[0051] In one embodiment, service function classifier bypass can be selectively configured for certain flows. For example, service function classifier bypass may be configured for a flow if the flow is an elephant flow (or is expected to be an elephant flow). Elephant flows are large flows with long durations (what is considered a large flow and a long duration can be defined by a network operator or other entity). In one embodiment, the service function classifier 120 transmits an indication of the approximate size and duration of the flow to the controller 320 (e.g., together with the translation rule for the flow). For example, the service function classifier 120 may transmit an indication to the controller 320 of whether the flow is an elephant flow or not. Based on this indication, the controller 320 can determine whether the flow should bypass the service function classifier 120 or not. Similarly, in one embodiment, service function classifier bypass may be configured for a flow if the flow has a high priority level (what is considered a high priority level can be defined by a network operator or other entity). In one embodiment, high priority flows are flows that require low latency (e.g., flows that carry voice data) or flows that belong to premium customers. In one embodiment, the service function classifier 120 transmits an indication of the priority level of the flow to the controller 320 (e.g., together with the translation rule for the flow). Based on this indication, the controller 320 can determine whether the flow should bypass the service function classifier 120 or not.

[0052] Fig. 5 is a diagram illustrating packet processing operations in a network after service function classifier bypass for a flow has been configured, according to some embodiments. The switch 330 may have been previously configured to stop forwarding packets belonging to the flow to the service function classifier 120, add an SFC encapsulation onto packets belonging to the flow, and forward packets belonging to the flow according to the contents of the SFC encapsulation (e.g., based on receiving service function classifier bypass instructions 550). At operation 1, the switch 330 receives a packet belonging to the flow. At operation 2, the switch 330 adds an SFC encapsulation onto the packet. At operation 3, the switch 330 forwards the packet with the SFC encapsulation according to the contents of the SFC encapsulation (e.g., into the SFP indicated in the SFC encapsulation). As a result, the packet bypasses the service function classifier 120, thereby avoiding the latency/bandwidth that is introduced by conventional techniques that require every packet to be processed by the service function classifier 120.

[0053] Fig. 6 is a diagram illustrating operations for handling termination of a flow, according to some embodiments. At operation 1, the switch 330 transmits an indication to the controller 320 that the flow is inactive. The switch 330 may have determined that the flow is inactive based on a determination that the flow entry for the flow has timed out (e.g., due to no packet matching the flow entry for a period of time). In response, at operation 2, the controller 320 transmits instructions to the switch 330 that instruct the switch 330 to remove or undo configurations related to service function classifier bypass for the flow (designated as "remove service function classifier bypass"). At operation 3, the controller 320 transmits an indication to the service function classifier 120 that service function classifier bypass for the flow has been removed (designated as "service function classifier bypass removed").

[0054] Fig. 7 is a flow diagram of a process for configuring a switch in an SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, according to some embodiments. In one embodiment, the process is performed by a controller 320 in the SDN network (e.g., a network device functioning as a controller 320 in the SDN network), where the controller 320 manages the switch 330 in the SDN network. In one embodiment, the controller 320 and the switch 330 communicate using OpenFlow or other type of southbound communications protocol. The operations in this and other 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.

[0055] In one embodiment, the process is initiated when the controller 320 obtains a translation rule for the flow, where the translation rule includes an indication of an SFC encapsulation that is to be added onto packets belonging to the flow (block 710). In one embodiment, the translation rule for the flow is obtained from the service function classifier 120. In one embodiment, the controller 320 obtains an indication of an approximate size and duration of the flow (e.g., whether the flow is an elephant flow) from the service function classifier 120 or other entity. The controller 320 may use this information to determine whether the flow is to bypass the service function classifier 120 or not. For example, the controller 320 may decide that only flows that have an approximate size and/or duration that exceed a predetermined threshold should bypass the service function classifier 120. The controller 320 may perform the remaining operations of the flow diagram for such flows so that those flows bypass the service function classifier 120. In one embodiment, the controller 320 obtains an indication of a priority level of the flow from the service function classifier 120 or other entity. The controller 320 may use this information to determine whether the flow is to bypass the service function classifier 120 or not. For example, the controller 320 may decide that only flows that have a priority level higher than a predetermined threshold (e.g., "premium" flows) should bypass the service function classifier 120. The controller 320 may perform the remaining operations of the flow diagram for such flows so that those flows bypass the service function classifier 120. In one embodiment, the translation rule for the flow includes an indication of one or more attributes that identify the flow (e.g., 5-tuple of source IP address, destination IP address, protocol, source port, and destination port). In one embodiment, the SFC encapsulation is a Network Service Header (NSH) that includes a service path identifier (ID) and a service index. In one embodiment, the NSH also includes metadata (e.g., with data plane context information).

[0056] In response to obtaining the translation rule for the flow, the controller 320 transmits service function classifier bypass instructions to the switch 330 that instruct the switch 330 to stop forwarding packets belonging to the flow to the service function classifier 120, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation (e.g., into the SFP indicated in the SFC encapsulation) (block 720). In one embodiment, the service function classifier bypass instructions include instructions for the switch 330 to generate one or more flow entries (or remove one or more flow entries) that cause the switch 330 to perform the service function classifier bypass for the flow.

[0057] The controller 320 then transmits an indication to the service function classifier 120 that the flow is to bypass the service function classifier 120 (block 730). This allows the service function classifier 120 to remove the translation rule for the flow from its translation table.

[0058] Fig. 8 is a flow diagram of a process for causing a flow in an SDN network to bypass a service function classifier, according to some embodiments. In one embodiment, the process is performed by the service function classifier 120 (e.g., a network device functioning as a service function classifier 120), where the service function classifier 120 is communicatively coupled to a controller 320 in the SDN network.

[0059] In one embodiment, the process is initiated when the service function classifier 120 determines a translation rule for the flow based on pre-configured SFC policy (block 805). The SFC policy may have been pre-configured by a network operator or other entity. The service function classifier 120 then provides the translation rule for the flow to the controller 320 (block 810). The translation rule may include an indication of one or more attributes that identify the flow and an SFC encapsulation that is to be added onto packets belonging to the flow. In one embodiment, the service function classifier 120 provides the translation rule for the flow to the controller 320 by transmitting the translation rule for the flow directly to the controller 320. In another embodiment, the service function classifier 120 provides the translation rule for the flow to the controller 320 by storing/publishing the translation rule for the flow at a location that the controller 320 can access. The controller 320 may then retrieve/pull the translation rule for the flow from that location (e.g., the location could be at the service function classifier 120 itself or at a separate database/server). The service function classifier 120 may subsequently receive an indication from the controller 320 that the flow is to bypass the service function classifier 120 (e.g., if the controller 320 confirms that service function classifier bypass for the flow is successfully configured in the SDN network) (block 820). In response, the service function classifier 120 removes the translation rule for the flow at the service function classifier 120 (e.g., from the translation table maintained at the service function classifier 120) (block 830).

[0060] Fig. 9 is a flow diagram of a process for processing a flow in an SDN network on behalf of a service function classifier so that the flow can bypass the service function classifier, according to some embodiments. In one embodiment, the process is performed by a switch 330 in the SDN network (e.g., a network device functioning as a switch 330 in the SDN network). The switch 330 may be managed by a controller 320 in the SDN network. In one embodiment, the controller 320 and the switch 330 communicate using OpenFlow or other type of southbound communications protocol.

[0061] In one embodiment, the process is initiated when the switch 330 obtains service function classifier bypass instructions for a flow (e.g., from the controller 320) (block 910). The service function classifier bypass instructions may instruct the switch 330 to stop forwarding packets belonging to the flow to the service function classifier 120, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation. The switch 330 may then be configured according to the service function classifier bypass instructions. For example, the switch 330 may remove a flow entry that instructs the switch 330 to forward packets belonging to the flow to the service function classifier 120, add a flow entry that instructs the switch 330 to add the SFC

encapsulation onto packets belonging to the flow, and add a flow entry that instructs the switch 330 to forward packets belonging to the flow to the appropriate next-hop (e.g., the next-hop of the SFP indicated in the SFC encapsulation).

[0062] When the switch 330 receives a packet belonging to the flow (block 920), the switch 330 adds the SFC encapsulation onto the packet (block 930) and forwards the packet according to contents of the SFC encapsulation (e.g., into the SFP indicated in the SFC encapsulation) (block 940).

[0063] Embodiments described herein thus allow a flow to bypass a service function classifier 120. An advantage provided by the embodiments described herein is that the latency of packets is reduced since the packets (except the initial packet) do not need to be forwarded to and from a service function classifier 120. Yet another advantage of embodiments described herein is that east-west communication in a network is reduced since packets do not need to be forwarded to and from a service function classifier 120. These advantages are even more pronounced when service function classifier bypass is provided for elephant flows (e.g., large flows with long durations). Other advantages will be readily apparent based on the descriptions provided herein.

[0064] Fig. 10A 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. Fig. 10A shows NDs 1000A-H, and their connectivity by way of lines between 1000A-1000B, lOOOB-lOOOC, lOOOC-lOOOD, 1000D-1000E, 1000E-1000F, 1000F-1000G, and 1000A-1000G, as well as between 1000H and each of 1000A, lOOOC, 1000D, and 1000G. 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 1000A, 1000E, and 1000F 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).

[0065] Two of the exemplary ND implementations in Fig. 10A are: 1) a special-purpose network device 1002 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 1004 that uses common off-the-shelf (COTS) processors and a standard OS.

[0066] The special-purpose network device 1002 includes networking hardware 1010 comprising compute resource(s) 1012 (which typically include a set of one or more processors), forwarding resource(s) 1014 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 1016 (sometimes called physical ports), as well as non-transitory machine readable storage media 1018 having stored therein networking software 1020. 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 1000A-H. During operation, the networking software 1020 may be executed by the networking hardware 1010 to instantiate a set of one or more networking software instance(s) 1022. Each of the networking software instance(s) 1022, and that part of the networking hardware 1010 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) 1022), form a separate virtual network element 1030A-R. Each of the virtual network element(s) (VNEs) 1030A-R includes a control communication and configuration module 1032A-R (sometimes referred to as a local control module or control communication module) and forwarding table(s) 1034A-R, such that a given virtual network element (e.g., 1030A) includes the control communication and configuration module (e.g., 1032A), a set of one or more forwarding table(s) (e.g., 1034A), and that portion of the networking hardware 1010 that executes the virtual network element (e.g., 1030A).

[0067] Software 1020 can include code such as service function (SF) classifier bypass component 1025, which when executed by networking hardware 1010, causes the special- purpose network device 1002 to perform operations of one or more embodiments of the present invention as part networking software instances 1022.

[0068] The special-purpose network device 1002 is often physically and/or logically considered to include: 1) a ND control plane 1024 (sometimes referred to as a control plane) comprising the compute resource(s) 1012 that execute the control communication and configuration module(s) 1032A-R; and 2) a ND forwarding plane 1026 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 1014 that utilize the forwarding table(s) 1034A-R and the physical NIs 1016. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 1024 (the compute resource(s) 1012 executing the control communication and configuration module(s) 1032A-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) 1034A-R, and the ND forwarding plane 1026 is responsible for receiving that data on the physical NIs 1016 and forwarding that data out the appropriate ones of the physical NIs 1016 based on the forwarding table(s) 1034A-R.

[0069] Fig. 10B illustrates an exemplary way to implement the special-purpose network device 1002 according to some embodiments of the invention. Fig. 10B shows a special- purpose network device including cards 1038 (typically hot pluggable). While in some embodiments the cards 1038 are of two types (one or more that operate as the ND forwarding plane 1026 (sometimes called line cards), and one or more that operate to implement the ND control plane 1024 (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 1036 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[0070] Returning to Fig. 10A, the general purpose network device 1004 includes hardware 1040 comprising a set of one or more processor(s) 1042 (which are often COTS processors) and network interface controller(s) 1044 (NICs; also known as network interface cards) (which include physical NIs 1046), as well as non-transitory machine readable storage media 1048 having stored therein software 1050. During operation, the processor(s) 1042 execute the software 1050 to instantiate one or more sets of one or more applications 1064A-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 1054 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 1062A-R called software containers that may each be used to execute one (or more) of the sets of applications 1064A-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 1054 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 1064A-R is run on top of a guest operating system within an instance 1062A-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 1ibfari.es (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 1040, 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 1054, unikernels running within software containers represented by instances 1062A-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).

[0071] The instantiation of the one or more sets of one or more applications 1064A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 1052. Each set of applications 1064A-R, corresponding virtualization construct (e.g., instance 1062A-R) if implemented, and that part of the hardware 1040 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) 1060A-R.

[0072] The virtual network element(s) 1060A-R perform similar functionality to the virtual network element(s) 1030A-R - e.g., similar to the control communication and configuration module(s) 1032A and forwarding table(s) 1034A (this virtualization of the hardware 1040 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 1062A-R corresponding to one VNE 1060A-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 1062A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used.

[0073] In certain embodiments, the virtualization layer 1054 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 1062A-R and the NIC(s) 1044, as well as optionally between the instances 1062A-R; in addition, this virtual switch may enforce network isolation between the VNEs 1060A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).

[0074] Software 1050 can include code such as service function (SF) classifier bypass component 1063, which when executed by processor(s) 1042, cause the general purpose network device 1004 to perform operations of one or more embodiments of the present invention as part software instances 1062A-R.

[0075] The third exemplary ND implementation in Fig. 10A is a hybrid network device 1006, 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 1002) could provide for para-virtualization to the networking hardware present in the hybrid network device 1006.

[0076] 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) 1030A-R, VNEs 1060A- R, and those in the hybrid network device 1006) receives data on the physical NIs (e.g., 1016, 1046) and forwards that data out the appropriate ones of the physical NIs (e.g., 1016, 1046). 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.

[0077] Fig. IOC illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention. Fig. IOC shows VNEs 1070A.1-1070A.P (and optionally VNEs 1070A.Q-1070A.R) implemented in ND 1000A and VNE 1070H.1 in ND 1000H. In Fig. IOC, VNEs 1070A.1-P are separate from each other in the sense that they can receive packets from outside ND 1000 A and forward packets outside of ND 1000 A; VNE 1070A.1 is coupled with VNE 1070H.1, and thus they communicate packets between their respective NDs; VNE 1070A.2-1070A.3 may optionally forward packets between themselves without forwarding them outside of the ND 1000A; and VNE 1070A.P may optionally be the first in a chain of VNEs that includes VNE 1070A.Q followed by VNE 1070A.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 Fig. IOC 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).

[0078] The NDs of Fig. 10A, 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 Fig. 10A may also host one or more such servers (e.g., in the case of the general purpose network device 1004, one or more of the software instances 1062A-R may operate as servers; the same would be true for the hybrid network device 1006; in the case of the special-purpose network device 1002, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 1012); in which case the servers are said to be co-located with the VNEs of that ND.

[0079] A virtual network is a logical abstraction of a physical network (such as that in Fig. 10A) 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).

[0080] 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).

[0081] 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).

[0082] Fig. 10D illustrates a network with a single network element on each of the NDs of Fig. 10A, 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, Fig. 10D illustrates network elements (NEs) 1070A-H with the same connectivity as the NDs 1000A-H of Fig. 10A.

[0083] Fig. 10D illustrates that the distributed approach 1072 distributes responsibility for generating the reachability and forwarding information across the NEs 1070A-H; in other words, the process of neighbor discovery and topology discovery is distributed.

[0084] For example, where the special-purpose network device 1002 is used, the control communication and configuration module(s) 1032A-R of the ND control plane 1024 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 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 1070A-H (e.g., the compute resource(s) 1012 executing the control communication and configuration module(s) 1032A-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 1024. The ND control plane 1024 programs the ND forwarding plane 1026 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 1024 programs the adjacency and route information into one or more forwarding table(s) 1034A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 1026. 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 1002, the same distributed approach 1072 can be implemented on the general purpose network device 1004 and the hybrid network device 1006.

[0085] Fig. 10D illustrates that a centralized approach 1074 (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 1074 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 1076 (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 1076 has a south bound interface 1082 with a data plane 1080 (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 1070A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 1076 includes a network controller 1078, which includes a centralized reachability and forwarding information module 1079 that determines the reachability within the network and distributes the forwarding information to the NEs 1070A-H of the data plane 1080 over the south bound interface 1082 (which may use the OpenFlow protocol). Thus, the network intelligence is centralized in the centralized control plane 1076 executing on electronic devices that are typically separate from the NDs. In one embodiment, the network controller 1078 may include a service function (SF) classifier bypass component 1081 that when executed by the network controller 1078, causes the network controller 1078 to perform operations of one or more embodiments described herein above.

[0086] For example, where the special-purpose network device 1002 is used in the data plane 1080, each of the control communication and configuration module(s) 1032A-R of the ND control plane 1024 typically include a control agent that provides the VNE side of the south bound interface 1082. In this case, the ND control plane 1024 (the compute resource(s) 1012 executing the control communication and configuration module(s) 1032A-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 1076 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 1079 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 1032A-R, in addition to communicating with the centralized control plane 1076, 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 1074, but may also be considered a hybrid approach).

[0087] While the above example uses the special-purpose network device 1002, the same centralized approach 1074 can be implemented with the general purpose network device 1004 (e.g., each of the VNE 1060A-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 1076 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 1079; it should be understood that in some embodiments of the invention, the VNEs 1060A-R, in addition to communicating with the centralized control plane 1076, 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 1006. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 1004 or hybrid network device 1006 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.

[0088] Fig. 10D also shows that the centralized control plane 1076 has a north bound interface 1084 to an application layer 1086, in which resides application(s) 1088. The centralized control plane 1076 has the ability to form virtual networks 1092 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 1070A-H of the data plane 1080 being the underlay network)) for the application(s) 1088. Thus, the centralized control plane 1076 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).

[0089] While Fig. 10D shows the distributed approach 1072 separate from the centralized approach 1074, 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) 1074, 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 1074, but may also be considered a hybrid approach.

[0090] While Fig. 10D illustrates the simple case where each of the NDs 1000A-H implements a single NE 1070A-H, it should be understood that the network control approaches described with reference to Fig. 10D also work for networks where one or more of the NDs 1000A-H implement multiple VNEs (e.g., VNEs 1030A-R, VNEs 1060A-R, those in the hybrid network device 1006). Alternatively or in addition, the network controller 1078 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 1078 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 1092 (all in the same one of the virtual network(s) 1092, each in different ones of the virtual network(s) 1092, or some combination). For example, the network controller 1078 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 1076 to present different VNEs in the virtual network(s) 1092 (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).

[0091] On the other hand, Figs. 10E and 10F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 1078 may present as part of different ones of the virtual networks 1092. Fig. 10E illustrates the simple case of where each of the NDs 1000A-H implements a single NE 1070A-H (see Fig. 10D), but the centralized control plane 1076 has abstracted multiple of the NEs in different NDs (the NEs 1070A-C and G-H) into (to represent) a single NE 10701 in one of the virtual network(s) 1092 of Fig. 10D, according to some embodiments of the invention. Fig. 10E shows that in this virtual network, the NE 10701 is coupled to NE 1070D and 1070F, which are both still coupled to NE 1070E.

[0092] Fig. 10F illustrates a case where multiple VNEs (VNE 1070A.1 and VNE 1070H.1) are implemented on different NDs (ND 1000A and ND 1000H) and are coupled to each other, and where the centralized control plane 1076 has abstracted these multiple VNEs such that they appear as a single VNE 1070T within one of the virtual networks 1092 of Fig. 10D, according to some embodiments of the invention. Thus, the abstraction of a NE or VNE can span multiple NDs.

[0093] While some embodiments of the invention implement the centralized control plane 1076 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).

[0094] Similar to the network device implementations, the electronic device(s) running the centralized control plane 1076, and thus the network controller 1078 including the centralized reachability and forwarding information module 1079, 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, Fig. 11 illustrates, a general purpose control plane device 1104 including hardware 1140 comprising a set of one or more processor(s) 1142 (which are often COTS processors) and network interface controller(s) 1144 (NICs; also known as network interface cards) (which include physical NIs 1146), as well as non-transitory machine readable storage media 1148 having stored therein centralized control plane (CCP) software 1150 and a service function (SF) classifier bypass component 1151.

[0095] In embodiments that use compute virtualization, the processor(s) 1142 typically execute software to instantiate a virtualization layer 1154 (e.g., in one 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 (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 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 an application is run on top of a guest operating system within an instance 1162A-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 dr vers/librar es of OS services) that provide the particular OS services needed by the application, and the unikernel can run directly on hardware 1140, directly on a hypervisor represented by virtualization layer 1154 (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 1162A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 1150 (illustrated as CCP instance 1176 A) is executed (e.g., within the instance 1162A) on the virtualization layer 1154. In embodiments where compute virtualization is not used, the CCP instance 1176A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 1104. The instantiation of the CCP instance 1176 A, as well as the virtualization layer 1154 and instances 1162A-R if implemented, are collectively referred to as software instance(s) 1152.

[0096] In some embodiments, the CCP instance 1176A includes a network controller instance 1178. The network controller instance 1178 includes a centralized reachability and forwarding information module instance 1179 (which is a middleware layer providing the context of the network controller 1078 to the operating system and communicating with the various NEs), and an CCP application layer 1180 (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 1180 within the centralized control plane 1076 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.

[0097] The service function (SF) classifier bypass component 1151 can be executed by hardware 1140 to perform operations of one or more embodiments of the present invention as part of software instances 1152.

[0098] The centralized control plane 1076 transmits relevant messages to the data plane 1080 based on CCP application layer 1180 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 1080 may receive different messages, and thus different forwarding information. The data plane 1080 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.

[0099] 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).

[00100] 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.

[00101] 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.

[00102] However, when an unknown packet (for example, a "missed packet" or a "match- miss" as used in OpenFlow parlance) arrives at the data plane 1080, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 1076. The centralized control plane 1076 will then program forwarding table entries into the data plane 1080 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 1080 by the centralized control plane 1076, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

[00103] 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.

[00104] Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of transactions on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of transactions leading to a desired result. The transactions are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[00105] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. [00106] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method transactions. The required structure for a variety of these systems will appear from the description above. In addition, embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of embodiments of the invention as described herein.

[00107] An embodiment of the invention may be an article of manufacture in which a non- transitory machine -readable medium (such as microelectronic memory) has stored thereon instructions which program one or more data processing components (generically referred to here as a "processor") to perform the operations described above. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e.g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components.

[00108] In the foregoing specification, embodiments of the invention have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

[00109] Throughout the description, embodiments of the present invention have been presented through flow diagrams. It will be appreciated that the order of transactions and transactions described in these flow diagrams are only intended for illustrative purposes and not intended as a limitation of the present invention. One having ordinary skill in the art would recognize that variations can be made to the flow diagrams without departing from the broader spirit and scope of the invention as set forth in the following claims.

Claims

CLAIMS What is claimed is:

1. A method implemented by a controller in a Software Defined Networking (SDN) network to configure a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, the method comprising: obtaining (710) a translation rule for the flow, wherein the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow;

transmitting (720) service function classifier bypass instructions to the switch that

instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation; and

transmitting (730) an indication to the service function classifier that the flow is to

bypass the service function classifier.

2. The method of claim 1 , wherein the translation rule for the flow is obtained from the service function classifier.

3. The method of claim 1, wherein the SFC encapsulation is a Network Service Header that includes a service path identifier (ID) and a service index.

4. The method of claim 1 , wherein the translation rule for the flow includes an indication of one or more attributes that identify the flow.

5. The method of claim 1, further comprising:

obtaining an indication of an approximate size and duration of the flow, wherein the indication of the approximate size and duration of the flow is used by the controller to determine whether the flow is to bypass the service function classifier.

6. The method of claim 1, further comprising: obtaining an indication of a priority level of the flow, wherein the indication of the priority level of the flow is used by the controller to determine whether the flow is to bypass the service function classifier.

7. The method of claim 1, wherein the controller and the switch communicate using OpenFlow.

8. A network device (1104) configured to function as a controller in a Software Defined

Networking (SDN) network to configure a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, the network device comprising:

a set of one or more processors (1142); and

a non-transitory machine-readable storage medium (1148) having stored therein a service function classifier bypass component (1151), which when executed by the set of one or more processors, causes the network device to obtain a translation rule for the flow, wherein the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow, transmit service function classifier bypass instructions to the switch that instruct the switch to stop forwarding packets belonging to the flow to the service function classifier, add the SFC encapsulation onto packets belonging to the flow, and forward the packets belonging to the flow according to contents of the SFC encapsulation, and transmit an indication to the service function classifier that the flow is to bypass the service function classifier.

9. The network device of claim 8, wherein the translation rule for the flow is obtained from the service function classifier.

10. The network device of claim 8, wherein the SFC encapsulation is a Network Service Header that includes a service path identifier (ID) and a service index.

11. The network device of claim 8, wherein the translation rule for the flow includes an

indication of one or more attributes that identify the flow.

12. The network device of claim 8, wherein the service function classifier bypass component, when executed by the set of one or more processors, further causes the network device to obtain an indication of an approximate size and duration of the flow, wherein the indication of the approximate size and duration of the flow is used by the controller to determine whether the flow is to bypass the service function classifier.

13. The network device of claim 8, wherein the service function classifier bypass component, when executed by the set of one or more processors, further causes the network device to obtain an indication of a priority level of the flow, wherein the indication of the priority level of the flow is used by the controller to determine whether the flow is to bypass the service function classifier.

14. A non-transitory machine-readable medium having computer code stored therein, which when executed by a set of one or more processors of a network device functioning as a controller in a Software Defined Networking (SDN) network, causes the network device to perform operations for configuring a switch in the SDN network to process a flow on behalf of a service function classifier so that the flow can bypass the service function classifier, the operations comprising:

obtaining (710) a translation rule for the flow, wherein the translation rule for the flow includes an indication of a Service Function Chaining (SFC) encapsulation that is to be added onto packets belonging to the flow;

bypass the service function classifier.

15. The non-transitory machine-readable medium of claim 14, wherein the translation rule for the flow is obtained from the service function classifier.

16. The non-transitory machine-readable medium of claim 14, wherein the SFC encapsulation is a Network Service Header that includes a service path identifier (ID) and a service index.

17. The non-transitory machine-readable medium of claim 14, wherein the translation rule for the flow includes an indication of one or more attributes that identify the flow.

18. The non-transitory machine-readable medium of claim 14, wherein the computer code, when executed by the set of one or more processors of the network device, causes the network device to perform further operations comprising:

19. The non-transitory machine-readable medium of claim 14, wherein the computer code, when executed by the set of one or more processors of the network device, causes the network device to perform further operations comprising:

obtaining an indication of a priority level of the flow, wherein the indication of the priority level of the flow is used by the controller to determine whether the flow is to bypass the service function classifier.

20. The non-transitory machine-readable medium of claim 14, wherein the controller and the switch communicate using OpenFlow.