Patent Application
20170070416
Embodiments of the invention relate to the field of networking; and more specifically, to modifying forwarding table entries of the network device in a Software Defined Network (SDN).
Software Defined Networking (SDN) is an approach to computer networking that allows network administrators to manage network services through abstraction of lower-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane). In such a system, a network controller, which is typically deployed as a cluster of server nodes, has the role of the control plane and is coupled to one or more network elements that have the role of the data plane. Each network elements being implemented on one or multiple network devices. The control connection between the network controller and network elements is generally a TCP/UDP based communication. The network controller communicates with the network elements using an SDN protocol (e.g., OpenFlow, I2RS, etc.).
For implementing SDN, the Open Networking Foundation (ONF), an industrial consortium focusing on commercializing SDN and its underlying technologies, has defined a set of open commands, functions, and protocols. The defined protocol suites are known as the OpenFlow (OF) protocol. The network controller, acting as the control plane, may then program the data plane on the network elements by causing packet handling rules to be installed on the forwarding network elements using OF commands and messages. These packet handling rules may have criteria to match various packet types as well as actions that may be performed on those packets. For example, the network controller may program the network elements to forward packets with a specific destination address a certain way in the network. The network controller programs the forwarding states on the data-plane (which includes multiple network elements) using flow modification requests. In a large scale deployment, where millions of such equivalent flow commands are being sent, the bandwidth requirement on the control-network can be enormous.
Embodiments of the invention relate to a method, in a network controller coupled to a network device of a software defined network (SDN), of modifying forwarding table entries of the network device. The method includes constructing a first message including a flow profile associated with a plurality of flows and an install profile command, where the flow profile includes a flow profile identifier, and a set of default parameter values that are common for the plurality of flows. The method continues with causing the network device to install the flow profile associated with the plurality of flows.
Embodiments of the invention relate to a network controller to be coupled to a network device in a software defined network (SDN). The network controller including: a processor and a memory, said memory containing instructions executable by the processor where the network controller is operative to construct a first message including a flow profile associated with a plurality of flows and an install profile command, where the flow profile includes a flow profile identifier, and a set of default parameter values that are common for the plurality of flows. The network controller is further operative to cause the network device to install the flow profile associated with the plurality of flows.
Embodiments of the invention relate to a method in a network device coupled with a network controller of a software defined network (SDN), the method including: receiving a first message from the network controller, where the first message includes a flow profile associated with a plurality of flows and an install profile command, where the flow profile includes a flow profile identifier, and a set of default parameter values that are common for the plurality of flows; and storing in response to the receiving of the first message, a flow profile entry including the flow profile identifier and the set of default parameter values.
Embodiments of the invention relate to a network device to be coupled to a network controller in a software defined network (SDN). The network device includes a processor and a memory, said memory containing instructions executable by the processor. The network device is operative to receive a first message from the network controller, where the first message includes a flow profile associated with a plurality of flows and an install profile command, where the flow profile includes a flow profile identifier, and a set of default parameter values that are common for the plurality of flows; and to store, in response to the receiving of the first message, a flow profile entry including the flow profile identifier and the set of default parameter values.
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:
The following description describes methods and apparatus for modifying forwarding table entries of the network device. 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.
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.
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.
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.
Software Defined Networking (SDN) is an approach to computer networking that allows network administrators to manage network services through abstraction of lower-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane). In such a system, a network controller, which is typically deployed as a cluster of server nodes, has the role of the control plane and is coupled to one or more network elements that have the role of the data plane. Each network elements being implemented on one or multiple network devices. The control connection between the network controller and network elements is generally a TCP/UDP based communication. The network controller communicates with the network elements using an SDN protocol (e.g., OpenFlow, I2RS, etc.).
Using OpenFlow, the network controller, acting as the control plane, programs the data plane on the network elements by causing packet handling rules to be installed on the forwarding network elements using OF commands and messages. These packet handling rules may have criteria to match various packet types as well as actions that may be performed on those packets. For example, the network controller may program the network elements to forward packets with a specific destination address a certain way in the network. To install packet handling rules on the forwarding network elements, the network controller transmits flow modification requests causing the modification of forwarding table entries of forwarding tables of a network element. In OpenFlow based SDN, the forwarding states are installed on the forwarding elements using OpenFlow flow modification messages (“flow mod” messages). The flow modification messages have a set of fields consisting of match criteria, instruction and other administrative fields that needs to be populated by the network controller in full for every single flow being installed on the network element.
In an exemplary scenario, when an application of an application layer located north bound of the network controller requires the installation of multiple flows, a request to install each flow (i.e., a flow modification request for the respective flow) is sent to a network device (on which at least part of a network element is implemented). In such a deployment scenario, the control network providing connectivity between the network controller and the forwarding elements of an SDN will be used continuously where the protocol messages will be exchanged between the control and data-plane and vice versa. However, in many scenarios, the flow modification requests may be of similar pattern for multiple flows with only certain fields in the message (i.e., flow modification request) being different. In a large scale deployment, where millions of such equivalent flow modification requests are sent, the bandwidth requirement on the network controller-network device connection (or as may be referred herein below as the “control network”) is enormous. With increase in scale, i.e., when there are thousands (if not millions) of flows (i.e., forwarding elements), the amount of control messages (e.g., flow modification requests, etc.) exchanged between the control plane and the data-plane can increase significantly. In case of disruptions in the control network (i.e., the network controller-network element connection), the resynchronization of the state of the network also requires all the forwarding states to be re-sent to the network elements further increasing the bandwidth used in the control network. Accordingly, additional methods and apparatuses for enabling an efficient forwarding states modification present clear advantages.
The embodiments of the present invention present methods and apparatuses for using flow profiles for programming the forwarding flows (i.e., forwarding states) on a network element such that the network controller acting as the control plane can send only a delta of fields (parameter values) needed to modify a specific forwarding flow while the remaining information (e.g., additional parameters common to multiple flows) can be retrieved from the flow profiles that are already installed on the network element. Thus use of the flow profiles reduces the amount of data being sent in the flow modification messages.
Methods and apparatuses for modifying forwarding states of a network element are hereby disclosed. In one embodiment, a message including a flow profile associated with a plurality of flows and an install profile command is constructed and transmitted to be installed on the network element. The flow profile includes a flow profile identifier and a set of default parameter values which are common to the multiple flows associated with this flow profile. In these embodiments, the installation and/or modification of the flow profile does not affect the forwarding plane of the network element (i.e., the forwarding table entries) and does not disturb the processing of the packets at the network element. At a later stage, another message is constructed to include the flow profile identifier, a set of parameter values associated with a particular flow, as well as a modify-flow command. This latter message is transmitted to be installed on the network element, resulting in the modification of the forwarding states (i.e., the actual forwarding table entries) associated with the particular flow.
The operations in the flow diagrams will be described with reference to the exemplary embodiments of the other figures. However, it should be understood that the operations of the flow diagrams can be performed by embodiments of the invention other than those discussed with reference to the other figures, and the embodiments of the invention discussed with reference to these other figures can perform operations different than those discussed with reference to the flow diagrams.
System 100 includes a software-defined network (SDN) represented by network controller (NC) 110 and network device (ND) 120 (which may also be referred herein as a forwarding network device). Although the SDN may include additional NDs controlled by NC 110, they are not shown here for ease of understanding. Thus when the description below refers to ND 120, one can assume that the description may also be referring to additional NDs in the SDN that are controlled by NC 110. In some embodiments, the network device 120 is a physical device implementing a logical network element or a portion of the network element. In some embodiments, a network element can be implemented on multiple network devices. For ease of understanding the embodiments described below refer to the connection and communication established between the network controller and the network device, however one would understand that this may represent a communication between the network controller and the network element including the networking functionality (e.g., router, bridge, or switch).
In the illustrated embodiment, the network controller 110 acts as the control plane and the NDs, including ND 120, act as the data plane. The control plane in the SDN communicates with the network devices implementing the data plane using an SDN communications protocol (e.g., OpenFlow; defined by the Open Networking Foundation). The network controller may be implemented on one or more network devices, and each of the NEs may be implemented on one or more network devices. The structure of the SDN is described in further details in reference to
An SDN provides a network administrator with a centrally managed control plane (e.g., the network controller 110) and may simplify management and reduce costs. Unlike a traditional network device where the control plane and data plane reside on one device, separating the control plane and data plane means that control plane and data plane devices are now communicatively coupled using a link, such as link 150. This may introduce additional latencies, bandwidth limitations, and disconnection/connection limitations. In typical scenarios thousands (if not millions) of forwarding states (flows) need to be installed or updated (i.e., modified) on the data plane. The embodiments described with reference to the operations of the circles 1-8 enable the modification of forwarding states of the network device 120 while significantly reducing the amount of data exchanged between the control and the data plane.
At circle 1, the network controller 110 identifies (112) a flow profile associated with the plurality of flows. Multiple flows are identified as having a similar set of parameter values enabling them to be associated with the same profile. For example, multiple flows may need to be installed on the forwarding device with identical actions, and/or matching criteria. In a non-limiting exemplary scenario, multiple flows may need to be installed when learning subscriber device Media Access Control addresses (MAC addresses) on a given port. In this scenario, multiple subscriber devices (each one having a given MAC address) may be connected to the same port in the SDN. When installing classification flows for the subscriber devices, all fields (i.e., parameters) except the Ethernet source address (i.e., the MAC address of the subscriber device) “Ethernet_src” match field have the same values. In another non-limiting exemplary scenario, multiple flows with common parameter values may need to be installed when performing subscriber classification based on subscribers' device Internet Protocol (IP) addresses. In this scenario, for all subscribers using the same set of services (for e.g., Internet service), when installing the flows (forwarding states), all fields have the same values except the source IP address (in the uplink direction) and destination IP Address (in the downlink direction).
At circle 2, the network controller 110 constructs (114) a message including the flow profile associated with the plurality of flows and an install profile command. The flow profile included in the message includes a flow profile identifier, and a set of default parameter values that are common for the plurality of flows. The set of default parameter values are initial or default values set for parameters that are used to install a flow in a forwarding table entry of the network device. In some embodiments, the message transmitted is an OpenFlow message. In an exemplary embodiment, the message is constructed according to a structure as described in detail with reference to
At circle 3, the constructed message 141 including the flow profile and the profile install command is transmitted through the communication link 150 to the network device. At circle 4, the network controller 110 causes (116) the network device 120 to install the flow profile associated with the plurality of flows.
Referring back to
Following the installation of a flow profile, this profile may be used by the network controller 110 to modify a flow (or a forwarding state) on the network device 120. Referring back to
At block 306, the network controller 110 identifies the flow profile associated with the flow to be installed. In some embodiments, the identification of the flow profile may be performed by identifying, at block 308, a first set of parameter values associated with the flow, and determining, at block 310 which flow profile is associated with this particular flow based on this first set of parameter values. In one exemplary embodiment, the first set of parameter values represent a subset of the default parameter values with which the flow profile was installed. In other embodiments, the identification of the flow profile may be performed based on other criteria.
At block 312, the network controller 110, constructs a second message including the flow profile identifier, a set of parameter values associated with the flow and a modify flow command. The set of parameter values transmitted in this second message are parameter values specific to the flow being installed. In some embodiments, this second set of parameter values will be used to override a portion of the default parameters installed with the flow profile associated with this flow. Describe how the message is constructed.
The flow of operations then moves to block 118, at which the network controller 110 causes the network device to modify a forwarding table entry in one or more forwarding tables for the flow, based on the flow profile identifier, the set of default parameters, and the set of parameters associated with the flow. In some embodiments, the network controller sends (314) the second message (e.g., message 142 in circle 7 of
Referring back to
Thus the embodiments presented above enable a network controller to install a plurality of flows based on an installation of a flow profile while reducing the amount of data exchanged at the control network. The network controller first install the flow profile with a set of default parameter values (fields) and identified with a flow profile identifier, and then enabled the installation of a flow by constructing and transmitting a message which includes only the parameter values (fields) which are specific to this particular flow, as well as the identifier of the flow profile associated with the flow.
The a_msg_flow_profile message is used by the network controller 110 to install a profile, a flow, or both on the network device 120. This message may be used to add a flow (e.g., install a new flow according to the OpenFlow command “OFPFC_ADD”), modify an existing flow (according to the OpenFlow command “OFPFC_MODIFY” or “OFPFC_MODIFY_STRICT”). In some embodiments, the same structure 600 is used to construct the first and the second message for respectively installing a flow profile and a flow at the network device. Although only one exemplary structure is presented for constructing the first and the second message, one would understand that the invention is not so limited and that in some embodiments, a first structure may be used to construct the first message and a different structure may be used to construct the second message.
Referring back to
In some embodiments, the set of default parameters are defined as illustrated in
In some embodiments, the command types may further include a “a_fpct_remove_profile” (707) command, which can be used to delete a previously installed profile. In other embodiments, the command types does not include the “a_fpct_remove_profile.” In these embodiments, a reboot of the network device 120 may remove previously installed profiles.
At 612, 614 and 616 the length fields are defined in the message structure: “admin_len”, “match_len” and “instruction_len” respectively. These fields indicate the size (length) of the admin_fields (618), the match field (620) and the instruction field (622) respectively, which are specified as part of this message 700.
Referring back to
The embodiments presented herein, relate to a method and apparatuses for modifying forwarding states (flows) of a network device based on flow profiles. These embodiments, present clear advantages with respect to the prior approaches by enabling the reduction of the amount of data exchanged between the control plane (e.g., network controller 110) and the data-plane (e.g., network device 120) when installing forwarding flows (forwarding states) by sending only the values of the parameters (fields) specific to a particular flow to be installed on the network device. In some embodiments, there is 50% to 70% reduction respectively in the amount of data exchanged when the method described with respect to
In addition, the embodiments described herein can be used interchangeably with existing flow modification methods of OpenFlow (e.g., installation of flow with “flow mod” messages as per the OpenFlow specification). Thus, these embodiments can be implemented without any change to the OpenFlow specification.
In some embodiments, the methods and apparatuses described with reference to
Table 1, below, illustrates the improvement resulting from the use of the installation of forwarding states based on flow profile, in the particular example of MAC learning and installation of associated flows on a given port when compared with a conventional method (i.e., installing each flow with a flow modification message from the OpenFlow specification):
In another example, the methods and apparatuses described with reference to
Table 2, below, illustrates the improvement resulting from the use of the installation of flows (forwarding states) based on a flow profile, in the particular example of subscriber classifier flow and installation of associated flows when compared with conventional methods:
According to this example, it can be seen that there is an improvement (reduction in the size of the messages transmitted to the network device from the network controller) of more than 65% with the proposed method.
Architecture
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 non-volatile memory into volatile memory (e.g., dynamic random access memory (DRAM), static random access memory (SRAM)) of that electronic device. Typical electronic devices also include a set or one or more physical network interface(s) 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.
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).
Two of the exemplary ND implementations in
The special-purpose network device 802 includes networking hardware 810 comprising compute resource(s) 812 (which typically include a set of one or more processors), forwarding resource(s) 814 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 816 (sometimes called physical ports), as well as non-transitory machine readable storage media 818 having stored therein networking software 820. The networking software includes a profile installation module (PIM) 821 operative to perform the operations described with reference to
The special-purpose network device 802 is often physically and/or logically considered to include: 1) a ND control plane 824 (sometimes referred to as a control plane) comprising the compute resource(s) 812 that execute the control communication and configuration module(s) 832A-R; and 2) a ND forwarding plane 826 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 814 that utilize the forwarding table(s) 834A-R and the physical NIs 816. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 824 (the compute resource(s) 812 executing the control communication and configuration module(s) 832A-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) 834A-R, and the ND forwarding plane 826 is responsible for receiving that data on the physical NIs 816 and forwarding that data out the appropriate ones of the physical NIs 816 based on the forwarding table(s) 834A-R.
Returning to
The instantiation of the one or more sets of one or more applications 864A-R, as well as the virtualization layer 854 and software containers 862A-R if implemented, are collectively referred to as software instance(s) 852. Each set of applications 864A-R, corresponding software container 862A-R if implemented, and that part of the hardware 840 that executes them (be it hardware dedicated to that execution and/or time slices of hardware temporally shared by software containers 862A-R), forms a separate virtual network element(s) 860A-R.
The virtual network element(s) 860A-R perform similar functionality to the virtual network element(s) 830A-R—e.g., similar to the control communication and configuration module(s) 832A and forwarding table(s) 834A (this virtualization of the hardware 840 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). However, different embodiments of the invention may implement one or more of the software container(s) 862A-R differently. For example, while embodiments of the invention are illustrated with each software container 862A-R corresponding to one VNE 860A-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 software containers 862A-R to VNEs also apply to embodiments where such a finer level of granularity is used.
In certain embodiments, the virtualization layer 854 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between software containers 862A-R and the NIC(s) 844, as well as optionally between the software containers 862A-R; in addition, this virtual switch may enforce network isolation between the VNEs 860A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).
The third exemplary ND implementation in
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) 830A-R, VNEs 860A-R, and those in the hybrid network device 806) receives data on the physical NIs (e.g., 816, 846) and forwards that data out the appropriate ones of the physical NIs (e.g., 816, 846). 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) (RFC 768, 2460, 2675, 4113, and 5405), Transmission Control Protocol (TCP) (RFC 793 and 1180), and differentiated services (DSCP) values (RFC 2474, 2475, 2597, 2983, 3086, 3140, 3246, 3247, 3260, 4594, 5865, 3289, 3290, and 3317).
The NDs of
A virtual network is a logical abstraction of a physical network (such as that in
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).
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 IPVPN RFC 4364) 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).
For example, where the special-purpose network device 802 is used, the control communication and configuration module(s) 832A-R of the ND control plane 824 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) (RFC 4271), Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First (OSPF) (RFC 2328 and 5340), Intermediate System to Intermediate System (IS-IS) (RFC 1142), Routing Information Protocol (RIP) (version 1 RFC 1058, version 2 RFC 2453, and next generation RFC 2080)), Label Distribution Protocol (LDP) (RFC 5036), Resource Reservation Protocol (RSVP) (RFC 2205, 2210, 2211, 2212, as well as RSVP-Traffic Engineering (TE): Extensions to RSVP for LSP Tunnels RFC 3209, Generalized Multi-Protocol Label Switching (GMPLS) Signaling RSVP-TE RFC 3473, RFC 3936, 4495, and 4558)) that communicate with other NEs to exchange routes, and then selects those routes based on one or more routing metrics. Thus, the NEs 870A-H (e.g., the compute resource(s) 812 executing the control communication and configuration module(s) 832A-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 824. The ND control plane 824 programs the ND forwarding plane 826 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 824 programs the adjacency and route information into one or more forwarding table(s) 834A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 826. 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 802, the same distributed approach 872 can be implemented on the general purpose network device 804 and the hybrid network device 806.
For example, where the special-purpose network device 802 is used in the data plane 880, each of the control communication and configuration module(s) 832A-R of the ND control plane 824 typically include a control agent that provides the VNE side of the south bound interface 882. In this case, the ND control plane 824 (the compute resource(s) 812 executing the control communication and configuration module(s) 832A-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 876 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 879 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 832A-R, in addition to communicating with the centralized control plane 876, 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 874, but may also be considered a hybrid approach).
While the above example uses the special-purpose network device 802, the same centralized approach 874 can be implemented with the general purpose network device 804 (e.g., each of the VNE 860A-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 876 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 879; it should be understood that in some embodiments of the invention, the VNEs 860A-R, in addition to communicating with the centralized control plane 876, 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 806. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 804 or hybrid network device 806 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.
While
While
On the other hand,
While some embodiments of the invention implement the centralized control plane 876 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).
Similar to the network device implementations, the electronic device(s) running the centralized control plane 876, and thus the network controller 878 including the centralized reachability and forwarding information module 879, 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,
In embodiments that use compute virtualization, the processor(s) 942 typically execute software to instantiate a virtualization layer 954 and software container(s) 962A-R (e.g., with operating system-level virtualization, the virtualization layer 954 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple software containers 962A-R (representing separate user space instances and also called virtualization engines, virtual private servers, or jails) that may each be used to execute a set of one or more applications; with full virtualization, the virtualization layer 954 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and the software containers 962A-R each represent a tightly isolated form of software container called a virtual machine that is run by the hypervisor and may include a guest operating system; with para-virtualization, an operating system or application running with a virtual machine may be aware of the presence of virtualization for optimization purposes). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 950 (illustrated as CCP instance 976A) is executed within the software container 962A on the virtualization layer 954. In embodiments where compute virtualization is not used, the CCP instance 976A on top of a host operating system is executed on the “bare metal” general purpose control plane device 904. The instantiation of the CCP instance 976A, as well as the virtualization layer 954 and software containers 962A-R if implemented, are collectively referred to as software instance(s) 952.
In some embodiments, the CCP instance 976A includes a network controller instance 978. The network controller instance 978 includes a centralized reachability and forwarding information module instance 979 (which is a middleware layer providing the context of the network controller 878 to the operating system and communicating with the various NEs), and an CCP application layer 980 (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 980 within the centralized control plane 876 works with virtual network view(s) (logical view(s) of the network) and the middleware layer provides the conversion from the virtual networks to the physical view. The network controller instance 978 further includes a control profile module instance 981 operative to perform the operations described with reference to
The centralized control plane 876 transmits relevant messages to the data plane 880 based on CCP application layer 980 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 880 may receive different messages, and thus different forwarding information. The data plane 880 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.
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).
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.
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.
However, when an unknown packet (for example, a “missed packet” or a “match-miss” as used in OpenFlow parlance) arrives at the data plane 880, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 876. The centralized control plane 876 will then program forwarding table entries into the data plane 880 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 880 by the centralized control plane 876, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.
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.
Next hop selection by the routing system for a given destination may resolve to one path (that is, a routing protocol may generate one next hop on a shortest path); but if the routing system determines there are multiple viable next hops (that is, the routing protocol generated forwarding solution offers more than one next hop on a shortest path—multiple equal cost next hops), some additional criteria is used—for instance, in a connectionless network, Equal Cost Multi Path (ECMP) (also known as Equal Cost Multi Pathing, multipath forwarding and IP multipath) (RFC 2991 and 2992) may be used (e.g., typical implementations use as the criteria particular header fields to ensure that the packets of a particular packet flow are always forwarded on the same next hop to preserve packet flow ordering). For purposes of multipath forwarding, a packet flow is defined as a set of packets that share an ordering constraint. As an example, the set of packets in a particular TCP transfer sequence need to arrive in order, else the TCP logic will interpret the out of order delivery as congestion and slow the TCP transfer rate down.
A Layer 3 (L3) Link Aggregation (LAG) link is a link directly connecting two NDs with multiple IP-addressed link paths (each link path is assigned a different IP address), and a load distribution decision across these different link paths is performed at the ND forwarding plane; in which case, a load distribution decision is made between the link paths.
Some NDs include functionality for authentication, authorization, and accounting (AAA) protocols (e.g., RADIUS (Remote Authentication Dial-In User Service), Diameter, and/or TACACS+ (Terminal Access Controller Access Control System Plus). AAA can be provided through a client/server model, where the AAA client is implemented on a ND and the AAA server can be implemented either locally on the ND or on a remote electronic device coupled with the ND. Authentication is the process of identifying and verifying a subscriber. For instance, a subscriber might be identified by a combination of a username and a password or through a unique key. Authorization determines what a subscriber can do after being authenticated, such as gaining access to certain electronic device information resources (e.g., through the use of access control policies). Accounting is recording user activity. By way of a summary example, end user devices may be coupled (e.g., through an access network) through an edge ND (supporting AAA processing) coupled to core NDs coupled to electronic devices implementing servers of service/content providers. AAA processing is performed to identify for a subscriber the subscriber record stored in the AAA server for that subscriber. A subscriber record includes a set of attributes (e.g., subscriber name, password, authentication information, access control information, rate-limiting information, policing information) used during processing of that subscriber's traffic.
Certain NDs (e.g., certain edge NDs) internally represent end user devices (or sometimes customer premise equipment (CPE) such as a residential gateway (e.g., a router, modem)) using subscriber circuits. A subscriber circuit uniquely identifies within the ND a subscriber session and typically exists for the lifetime of the session. Thus, a ND typically allocates a subscriber circuit when the subscriber connects to that ND, and correspondingly de-allocates that subscriber circuit when that subscriber disconnects. Each subscriber session represents a distinguishable flow of packets communicated between the ND and an end user device (or sometimes CPE such as a residential gateway or modem) using a protocol, such as the point-to-point protocol over another protocol (PPPoX) (e.g., where X is Ethernet or Asynchronous Transfer Mode (ATM)), Ethernet, 802.1 Q Virtual LAN (VLAN), Internet Protocol, or ATM). A subscriber session can be initiated using a variety of mechanisms (e.g., manual provisioning a dynamic host configuration protocol (DHCP), DHCP/client-less internet protocol service (CLIPS) or Media Access Control (MAC) address tracking). For example, the point-to-point protocol (PPP) is commonly used for digital subscriber line (DSL) services and requires installation of a PPP client that enables the subscriber to enter a username and a password, which in turn may be used to select a subscriber record. When DHCP is used (e.g., for cable modem services), a username typically is not provided; but in such situations other information (e.g., information that includes the MAC address of the hardware in the end user device (or CPE)) is provided. The use of DHCP and CLIPS on the ND captures the MAC addresses and uses these addresses to distinguish subscribers and access their subscriber records.
A virtual circuit (VC), synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication. Virtual circuit communication resembles circuit switching, since both are connection oriented, meaning that in both cases data is delivered in correct order, and signaling overhead is required during a connection establishment phase. Virtual circuits may exist at different layers. For example, at layer 4, a connection oriented transport layer datalink protocol such as Transmission Control Protocol (TCP) (RFC 793 and 1180) may rely on a connectionless packet switching network layer protocol such as IP, where different packets may be routed over different paths, and thus be delivered out of order. Where a reliable virtual circuit is established with TCP on top of the underlying unreliable and connectionless IP protocol, the virtual circuit is identified by the source and destination network socket address pair, i.e. the sender and receiver IP address and port number. However, a virtual circuit (RFC 1180, 955, and 1644) is possible since TCP includes segment numbering and reordering on the receiver side to prevent out-of-order delivery. Virtual circuits are also possible at Layer 3 (network layer) and Layer 2 (datalink layer); such virtual circuit protocols are based on connection oriented packet switching, meaning that data is always delivered along the same network path, i.e. through the same NEs/VNEs. In such protocols, the packets are not routed individually and complete addressing information is not provided in the header of each data packet; only a small virtual channel identifier (VCI) is required in each packet; and routing information is transferred to the NEs/VNEs during the connection establishment phase; switching only involves looking up the virtual channel identifier in a table rather than analyzing a complete address. Examples of network layer and datalink layer virtual circuit protocols, where data always is delivered over the same path: X.25, where the VC is identified by a virtual channel identifier (VCI); Frame relay, where the VC is identified by a VCI; Asynchronous Transfer Mode (ATM), where the circuit is identified by a virtual path identifier (VPI) and virtual channel identifier (VCI) pair; General Packet Radio Service (GPRS); and Multiprotocol label switching (MPLS) (RFC 3031), which can be used for IP over virtual circuits (Each circuit is identified by a label).
Certain NDs (e.g., certain edge NDs) use a hierarchy of circuits. The leaf nodes of the hierarchy of circuits are subscriber circuits. The subscriber circuits have parent circuits in the hierarchy that typically represent aggregations of multiple subscriber circuits, and thus the network segments and elements used to provide access network connectivity of those end user devices to the ND. These parent circuits may represent physical or logical aggregations of subscriber circuits (e.g., a virtual local area network (VLAN), a permanent virtual circuit (PVC) (e.g., for Asynchronous Transfer Mode (ATM)), a circuit-group, a channel, a pseudo-wire, a physical NI of the ND, and a link aggregation group). A circuit-group is a virtual construct that allows various sets of circuits to be grouped together for configuration purposes, for example aggregate rate control. A pseudo-wire is an emulation of a layer 2 point-to-point connection-oriented service. A link aggregation group is a virtual construct that merges multiple physical NIs for purposes of bandwidth aggregation and redundancy. Thus, the parent circuits physically or logically encapsulate the subscriber circuits.
Each VNE (e.g., a virtual router, a virtual bridge (which may act as a virtual switch instance in a Virtual Private LAN Service (VPLS) (RFC 4761 and 4762) is typically independently administrable. For example, in the case of multiple virtual routers, each of the virtual routers may share system resources but is separate from the other virtual routers regarding its management domain, AAA (authentication, authorization, and accounting) name space, IP address, and routing database(s). Multiple VNEs may be employed in an edge ND to provide direct network access and/or different classes of services for subscribers of service and/or content providers.
Within certain NDs, “interfaces” that are independent of physical NIs may be configured as part of the VNEs to provide higher-layer protocol and service information (e.g., Layer 3 addressing). The subscriber records in the AAA server identify, in addition to the other subscriber configuration requirements, to which context (e.g., which of the VNEs/NEs) the corresponding subscribers should be bound within the ND. As used herein, a binding forms an association between a physical entity (e.g., physical NI, channel) or a logical entity (e.g., circuit such as a subscriber circuit or logical circuit (a set of one or more subscriber circuits)) and a context's interface over which network protocols (e.g., routing protocols, bridging protocols) are configured for that context. Subscriber data flows on the physical entity when some higher-layer protocol interface is configured and associated with that physical entity.
Some NDs provide support for implementing VPNs (Virtual Private Networks) (e.g., Layer 2 VPNs and/or Layer 3 VPNs). For example, the ND where a provider's network and a customer's network are coupled are respectively referred to as PEs (Provider Edge) and CEs (Customer Edge). In a Layer 2 VPN, forwarding typically is performed on the CE(s) on either end of the VPN and traffic is sent across the network (e.g., through one or more PEs coupled by other NDs). Layer 2 circuits are configured between the CEs and PEs (e.g., an Ethernet port, an ATM permanent virtual circuit (PVC), a Frame Relay PVC). In a Layer 3 VPN, routing typically is performed by the PEs. By way of example, an edge ND that supports multiple VNEs may be deployed as a PE; and a VNE may be configured with a VPN protocol, and thus that VNE is referred as a VPN VNE.
Some NDs provide support for VPLS (Virtual Private LAN Service) (RFC 4761 and 4762). For example, in a VPLS network, end user devices access content/services provided through the VPLS network by coupling to CEs, which are coupled through PEs coupled by other NDs. VPLS networks can be used for implementing triple play network applications (e.g., data applications (e.g., high-speed Internet access), video applications (e.g., television service such as IPTV (Internet Protocol Television), VoD (Video-on-Demand) service), and voice applications (e.g., VoIP (Voice over Internet Protocol) service)), VPN services, etc. VPLS is a type of layer 2 VPN that can be used for multi-point connectivity. VPLS networks also allow end use devices that are coupled with CEs at separate geographical locations to communicate with each other across a Wide Area Network (WAN) as if they were directly attached to each other in a Local Area Network (LAN) (referred to as an emulated LAN).
In VPLS networks, each CE typically attaches, possibly through an access network (wired and/or wireless), to a bridge module of a PE via an attachment circuit (e.g., a virtual link or connection between the CE and the PE). The bridge module of the PE attaches to an emulated LAN through an emulated LAN interface. Each bridge module acts as a “Virtual Switch Instance” (VSI) by maintaining a forwarding table that maps MAC addresses to pseudowires and attachment circuits. PEs forward frames (received from CEs) to destinations (e.g., other CEs, other PEs) based on the MAC destination address field included in those frames.
For example, while the flow diagrams in the figures show a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).
While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.
