Configuration of network elements for automated policy-based routing

In one embodiment a forwarding policy from a first network node coupled to a network element is received. The forwarding policy specifies an address of a second network node coupled to the network element. A plurality of ports of the network element are identified, wherein the second network node is accessible from the network element through each of the plurality of ports. The forwarding policy is applied to the plurality of ports of the network element. Network traffic received at a port of the plurality of ports from the second network node is forwarded to the first network node.

RELATED APPLICATION

TECHNICAL FIELD

This disclosure relates in general to the field of communications and, more particularly, to configuration of network elements for automated policy-based routing.

BACKGROUND

Data centers are increasingly used by enterprises for effective collaboration, data storage, and resource management. A typical data center network contains myriad network elements including servers, load balancers, routers, switches, etc. The network connecting the network elements provides secure user access to data center services and an infrastructure for deployment, interconnection, and aggregation of shared resources. Improving operational efficiency and optimizing utilization of resources in data centers are some of the challenges facing data center managers. Data center managers seek a resilient infrastructure that consistently supports diverse applications and services. A properly planned data center network provides application and data integrity and, further, optimizes application availability and performance.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

In one embodiment a forwarding policy from a first network node coupled to a network element is received. The forwarding policy specifies an address of a second network node coupled to the network element. A plurality of ports of the network element are identified, wherein the second network node is accessible from the network element through each of the plurality of ports. The forwarding policy is applied to the plurality of ports of the network element. Network traffic received at a port of the plurality of ports from the second network node is forwarded to the first network node.

Example Embodiments

FIG. 1illustrates a block diagram of a system100comprising a service appliance104and a network element108having multiple paths112to one or more destination servers116in accordance with certain embodiments. System100also includes a plurality of client devices120coupled to the network element108through network124. The destination servers116may be part of a server farm128or other grouping of devices operable to respond to requests from clients120. The destination servers116are coupled to the network element108through networks132aand132b.

Network services are often inserted into a network such as system100. The network services may include, by way of nonlimiting example, load balancing or application delivery services. The network services may be performed by one or more service appliances104, which may be server blades or line cards integrated into network elements108(e.g., switches, routers, etc.) or may be external appliances. The provision of network services typically necessitates manual configuration of network elements108and other network nodes (e.g., servers).

For example, when providing load balancing or application delivery services, a client device120sends a request (e.g., one or more packets) that is intercepted by a service application running on one or more of the service appliances104. For example, the one or more packets of the request may have a source address of the client device and a destination address of the service appliance (e.g., a virtual Internet Protocol (IP) address that may be associated with one or more services that may be provided by each of servers116of server farm128). Upon receiving the request from the client, the service application of service appliance104is configured to select a server (e.g., destination server116) among a group of servers (e.g., server farm128) to fulfill the request. The service application may then change the destination address of the one or more packets to an address of the selected destination server and forward the packets having the source address of the client device and the destination address of the selected server to the selected server.

To ensure that return packets (e.g., packets flowing from the selected server to the client device) are transmitted via the service application (so as to appear to the client device to have originated from the address of the service appliance104), routing/redirection policies may be set up on various network nodes (e.g., network elements108) in between the service appliance104and the destination server116. The process of manually configuring policies on each network node to handle traffic redirection (so that return traffic from the destination server to the client is sent to the service appliance104) and manually updating configuration policies based on the availability of the destination servers is tedious, time consuming, and error-prone.

In various embodiments of the present disclosure, methods and apparatuses for automating the configuration of return traffic redirection to a service appliance104by injecting forwarding policies into network elements108are disclosed herein. Various embodiments may include establishing a communication channel between a service appliance and a network element; receiving, at the network element from the service appliance, a forwarding policy that requests the network element to forward predetermined packets (e.g., packets received from one or more destination servers) to the service appliance; identify which ports of the network element are included in routes to the one or more destination servers, implementing the forwarding policy on the identified ports of the network element, and sending the forwarding policy to other network elements that are located between the network element and the one or more destination servers. The other network elements may perform a similar process to ensure that return traffic is directed back to the service appliance104before delivery to the client120.

When a return packet having a source address of a destination server and a destination address of a client device is received, a network element108may determine whether to forward the return packet towards the service appliance104based on the forwarding policy and will transmit the return packet towards the service appliance104in the event of an affirmative determination (if the network element108is adjacent the service appliance it will deliver the return packet to the service appliance). In at least some embodiments, network element108may set the “next hop” IP address of return traffic reaching the network element to the IP address of the service appliance104without modifying packets of the return traffic. The network element108then forwards the return traffic to the service appliance, which then directs the return traffic to the client with a source address of the service appliance104and a destination address of the client device120(e.g., the service appliance104may modify the source address of the packets to the IP address of the service appliance).

Client devices120may be any suitable computing devices operable to send and receive network traffic (e.g., data packets). In various embodiments, a “computing device” may be or comprise, by way of non-limiting example, a computer, workstation, server, mainframe, embedded computer, embedded controller, embedded sensor, personal digital assistant, laptop computer, cellular telephone, IP telephone, smart phone, tablet computer, convertible tablet computer, computing appliance, network appliance, receiver, wearable computer, handheld calculator, virtual machine, virtual appliance, or any other electronic, microelectronic, or microelectromechanical device for processing and communicating data. A client device may include an appropriate operating system, such as Microsoft Windows, Linux, Android, Mac OSX, Apple iOS, Unix, or similar operating system. Client devices120may be communicatively coupled to one another and to other network resources via network124.

Network element108may be any device or system operable to process and/or forward traffic in conjunction with forwarding policies. For example, network elements may comprise network switches, routers, servers (physical servers or servers virtually implemented on physical hardware), machines (physical machine or machines virtually implemented on physical hardware), end user devices, access points, cable boxes, gateways, bridges, load balancers, firewalls, inline service nodes, proxies, processors, modules; other suitable devices, components, elements, proprietary appliances, or objects operable to exchange, receive, and transmit information in a network environment; or a combination of two or more of these. A network element may include any suitable hardware, software, components, modules, interfaces, or objects that facilitate operations associated with processing and/or forwarding network traffic. This may be inclusive of appropriate algorithms and communication protocols that allow for the effective exchange of data or information. Network element108may be deployed in a data center, as an aggregation node (to aggregate traffic from a plurality of access domains), within a core network, or in other suitable configuration.

In some embodiments, network element108includes a multi-port network bridge that processes and routes data at a data link layer (Layer 2). In another example, network element108may process and/or route data at other various layers such as a Layer 3 network layer, Layer 4 (with network address translation and load distribution), Layer 7 (load distribution based on application specific transactions), or at multiple layers (e.g., Layer 2 and Layer 3). In certain embodiments, functionalities of a switch may be integrated into other network elements such as gateways, routers, or servers. In various embodiments, network element108is a managed switch (e.g., managed using a command line interface (CLI), a web interface, etc.). In one particular embodiments, network element is a Cisco® N7K switch.

A network element108may connect to service appliance104over a communication channel136(e.g., over a port-channel). As used herein, a “communication channel” encompasses a physical transmission medium (e.g., a wire), or a logical connection (e.g., a radio channel, a network connection) used to convey information signals (e.g., data packets, control packets, etc.) from one or more senders (e.g., network element108) to one or more receivers (e.g., service appliance104). A communication channel, as used herein, can include one or more communication links, which may be physical (e.g., wire) or logical (e.g., data link, wireless link, etc.). Termination points of communication channels can include interfaces such as Ethernet ports, serial ports, etc. In embodiments of system100, communication channel136may be a single channel deployed for both control messages (i.e., messages that include control packets) and data messages (i.e., messages that include data packets).

In some embodiments, service appliance104may be a discrete (and generally separate) hardware device or virtual machine with integrated software (e.g., firmware), designed to provide one or more network services including load balancing, firewall, intrusion prevention, virtual private network (VPN), proxy, or other network services.

In some embodiments, service appliance104is assigned an IP address (which in some embodiments may be a virtual IP address) or other address to which clients may address network traffic. Clients may request a service from server farm128(or other group of servers) by sending a request to the address of the service appliance104. The traffic is delivered to the service appliance104by the network element108based on the destination address (matching the address of the service appliance) of the traffic. In some embodiments, the service appliance104is operable to load balance the traffic received from clients120among a plurality of servers116, based on any suitable criteria, such as the source IP address, source media access control (MAC) address, source port, protocol (e.g., one or more L3 protocols such as IPv4 or IPv6 or one or more L4 protocols such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP)), one or more QoS parameters, one or more virtual local area network (VLAN) identifiers, and/or other suitable information associated with (e.g., specified by) the header or body of one or more packets of the network traffic.

Upon selection of a destination server116from a plurality of available servers, the service appliance may then send the network traffic to the destination server. For example, the service appliance may modify the destination address of the packet to be the address (e.g., IP address) of the destination server116and then send the packet through the network element108towards the destination server.

In some cases, network element108may be configured with an intelligent service card manager module (ISCM), and service appliance104may be configured with a corresponding intelligent service card client module (ISCC). The ISCM and ISCC can form part of an infrastructure for configuring service appliance104on the network element108, e.g., as a virtual line card in network element108. The ISCM and ISCC may comprise any suitable logic, including hardware, software, or a combination thereof. In some embodiments, the ISCM or ISCC may comprise software executed by a processor.

In some cases, the ISCC and ISCM may be configured to allow service appliance104to appear as a virtual line card, or some other virtual network node/entity. The terms “line card” and “service module” are interchangeably used herein to refer to modular electronic circuits interfacing with telecommunication lines (such as copper wires or optical fibers) and that offer a pathway to the rest of a telecommunications network. Service appliance may be referred to simply as “appliance” or “module” herein. Hence, a virtual line card is interchangeable (in certain instances) with an ISCM. A virtual service module (or a virtual line card) is a logical instance (of a service module) providing the same functionalities (as the service module). Service modules may perform various functions including providing network services (e.g., similar to service appliances). One difference between a service module and a service appliance is that the service module is physically located within a network element, for example, on an appropriate physical slot. Virtual service modules are similarly configurable within a network element.

In an example, a (external) service appliance104may connect to a network element108(e.g., switch) and behave like a service module within the network element without having to take up a physical slot in the network element. Such configurations may consolidate the provisioning of appliances and enable the appliances to have the benefits of being a service module within the network element. The task for provisioning and configuring of these service appliances is performed mostly by the infrastructure provided on the network element, making it easy for network administrators to add/remove service appliances in the network.

According to embodiments of the present disclosure, an appliance user can enjoy the benefit of a service module's simple configuration and operation using the infrastructure of network element108. For example, setting up service appliance104for network configurations may be unnecessary. Substantially all such configurations may be made via network element108, instead of service appliance104. Service appliance104may offload (i.e., transfer) any network (e.g., L2/L3 network) specific control plane and data plane operations to network element108. Data path acceleration that leverages an application specific integrated circuit (ASIC) (potentially embedded in network element108) may also be possible in various embodiments. Network element108may communicate control messages to service appliance104over communication channel136. Thus, configuration and provisioning of services within service appliance104may be implemented via network element108.

A service appliance104or a network element108may include one or more portions of one or more computer systems. In particular embodiments, one or more of these computer systems may perform one or more steps of one or more methods described or illustrated herein. In particular embodiments, one or more computer systems may provide functionality described or illustrated herein. In some embodiments, encoded software running on one or more computer systems may perform one or more steps of one or more methods described or illustrated herein and/or provide functionality described or illustrated herein. The components of the one or more computer systems may comprise any suitable physical form, configuration, number, type, and/or layout. Where appropriate, one or more computer systems may be unitary or distributed, span multiple locations, span multiple machines, or reside in a cloud, which may include one or more cloud components in one or more networks.

Service appliance104may load balance among servers116belonging to one or more server farms128coupled to network element108. A server farm128comprises one or more servers116operable to communicate with clients120. In some embodiments, various servers116within server farm128may each be operable to provide one or more services to clients120. For example, servers116may be redundant with each other such that any server of at least a subset of servers of the server farm may provide the same service(s) to clients120. In some embodiments, client120may send a server116a request, server116may perform processing based on the request, and may respond to the client with the requested data. In particular embodiments, individual servers in server farm128may communicate with other servers in the same server farm128via one or more network elements (e.g., switches). Servers in server farm128may communicate with servers in another server farm via one or more network elements108in various implementations.

Although various figures herein illustrate server farms128, it should be appreciated that other groupings of servers may be used. As used herein, a server may refer to any device configured to communicate network traffic with clients120via one or more networks. Thus the term “server” may encompass computers, virtual machines, network appliances, application servers, routers, switches, gateways, bridges, load balancers, firewalls, processors, modules, or any other suitable device, component, proprietary element, or object operable to exchange information in a network environment. Moreover, the servers116may include any suitable hardware, software, components, modules, interfaces, or objects that facilitate the operations thereof. This may be inclusive of appropriate algorithms and communication protocols that allow for the effective exchange of data or information. In one example, server farm128may be replaced with a LAN connecting desktop computers in a small office. In another example, server farm128may be replaced with a network of wireless communication devices. In yet another example, server farm128may be replaced with one or more supercomputers. Various other configurations and devices are contemplated within the broad framework of the present disclosure.

The networks described herein (e.g., networks124,132a, and132b) may be any suitable network or combination of one or more networks operating on one or more suitable networking protocols. A network may represent a series of points, nodes, or network elements and interconnected communication paths for receiving and transmitting packets of information that propagate through a communication system. For example, a network may include one or more firewalls, routers, switches, security appliances, antivirus servers, or other useful network devices. A network offers a communicative interface between sources and/or hosts, and may comprise any local area network (LAN), wireless local area network (WLAN), metropolitan area network (MAN), Intranet, Extranet, Internet, wide area network (WAN), virtual private network (VPN), cellular network, or any other appropriate architecture or system that facilitates communications in a network environment depending on the network topology. A network can comprise any number of hardware or software elements coupled to (and in communication with) each other through a communications medium. As one example, a network may include one or more network elements108in the path from a source node coupled to the network and a destination node. In some embodiments, a network may simply comprise a connection such as a cable (e.g., an Ethernet cable), air, or other transmission medium.

Network element108may reach the destination server116via any number of different paths, such as network path112aor network path112b. A network path is comprised of the network segments and network nodes that data from a source passes through on its way to a destination. In the embodiment depicted, network path112amay include a first port of network element108while network path112bincludes a second port of network element108. In various embodiments, network paths may or may not share one or more segments or network nodes. In various embodiments, packets sent between network element108and destination server116may leave from the same port of network element108, but may still travel different paths to the destination server116. In some situations, a packet from client120ato destination server116may travel from a first port of network element108through path112ato destination server116while a packet from destination server116to client120amay travel through path112bto a second port of network element108on its way to client120a.

In a datacenter or other configuration, it may be common to have a network element108coupled to one or more server farms via multiple network paths112(utilizing a plurality of the ports of the network element108) as shown in system100. This means that one or more of the network paths112may be used at any point of time to send traffic between servers116and clients120. In some embodiments, each port of the switch has the same weight (i.e., traffic is equally likely to exit the switch at each port) and there may be no predetermined way to know which of the ports will be used to reach the server116or which of the ports will be used for return traffic from the server. Such a scenario may be referred to as an equal cost multi-path (ECMP) case. Accordingly, when a network element108determines that it should implement a forwarding policy to forward traffic received from a server116back to the service appliance104, the network element108may determine which of its ports may be used to reach the server116. In some embodiments, an ISCM registers with a unified/unicast routing information base (URIB) to determine the route and nexthop port through which network element108can reach the destination server116. In various embodiments, a URIB is a software module running on a control plane of network element108and may communicate with the ISCM via one or more APIs. A URIB may have information about which IP routes are set up for each port of the network element. The ISCM may communicate the IP address of the destination server and the URIB will return one or more nexthop IP addresses and/or one or more ports through which the nexthop IP addresses may be reached. If the URIB only returns one nexthop port at a time, the appropriate APIs can be called multiple times to obtain all the nexthop ports in the ECMP case. Subsequently, the forwarding policy will be applied on each of the identified ports. The network element108may store an indication of which ports the forwarding policy has been applied to, such that if the server116later becomes unreachable through one or more of the ports, the forwarding policy may be removed from each port from which the server116is unreachable.

FIG. 2illustrates a block diagram of a system200comprising a service appliance104and a network element108ahaving multiple virtual device contexts (VDCs)140each having at least one path to one or more destination servers116in accordance with certain embodiments. Network element108amay have any of the characteristics described herein with respect to network element108and vice versa.

VDCs140aand140ballow the network element108to be virtualized at the device level, presenting the physical network element as multiple logical devices. Each configured VDC140presents itself as a unique device to connected users within the framework of the physical network element. A VDC140may run as a separate logical entity within the network element, maintaining its own unique set of running software processes, having its own configuration, and being managed by a separate administrator in some situations. A VDC140may contain its own unique and independent set of VLANs and virtual route forwarding instances (VRFs). A VRF can be used to virtualize the Layer 3 forwarding and routing tables.

Each VDC140may have physical ports allocated to it, thus allowing for the hardware data plane to be virtualized as well. In at least some embodiments, the physical switch ports of network element108are resources that cannot be shared between VDC140s. Within each VDC140, a separate management domain can manage the VDC140itself, thus allowing the management plane itself to also be virtualized.

In some embodiments, a network element capable of being configured with VDCs has a default setting where all physical ports on the network element are assigned to a default VDC140(e.g. VDC140a). When a new VDC140bis created, an administrator may be required to assign a set of physical ports from the default VDC140ato the newly created VDC140b, providing the new VDC140bwith a means to communicate with other devices on the network. In at least some embodiments, once a physical port is assigned to a particular VDC140, it is bound exclusively to that VDC140, and no other VDC140has access to that port. In particular embodiments, inter-VDC communication is not facilitated from within the network element108, but a discrete external connection must be made between ports of different VDC140sto allow communication between them.

In various configurations, a client device120may communicate with the server116through any of multiple VDCs140of a network element108. For example, client device120amight send a request to the server via network path144ausing VDC140a, but receive a response from the server116through network path144busing VDC140b. For example, traffic may be sent from the client to the server using a first VLAN associated with VDC140awhile return traffic may be sent from the server to the client using a second VLAN associated with VDC140b.

Each VDC140may be associated with its own instance of an ISCM. However, each ISCM instance is local to its particular VDC and does not manage the operation of other VDCs or their physical ports. In various embodiments, a network element108may include or provide access to a global database that is accessible by each VDC (e.g., via its ISCM) of the network element108. One ISCM may create a forwarding policy, store the policy in the shared database, and notify the other ISCMs of the network element that a policy has been added to the shared database. Each other ISCM on the network element108may then access the new policy from the shared database and determine whether the VDC is able to reach the server116and the service appliance104. If so, the forwarding policy is applied to all of the physical ports of the VDC that are able to reach the server116. When a policy needs to be deleted, the global shared database is consulted to determine all the VDCs in which the policy is applied and delete requests are sent out accordingly.

FIG. 3illustrates a block diagram of a network element108ain accordance with certain embodiments. The network element108ais configured to include two VDCs140aand140b, though a network element108may be configured with any suitable number of VDCs including zero (in which case the components illustrated inside of a VDC140may be associated with the entire network element108rather than a VDC140of the network element). The network element108aalso includes processor148and storage152.

In the embodiment depicted, network element108aincludes a computer system to facilitate performance of its operations. In particular embodiments, a computer system may include a processor, storage, and one or more communication interfaces, among other components. As an example, network element108acomprises a computer system that includes one or more processors148, storage152, and one or more communication interfaces156that are virtualized through VDC140aand140b. These components may work together in order to provide functionality described herein.

A communication interface156may be used for the communication of signaling and/or data between network element108and one or more networks (e.g.,124,132a, or132b) and/or network nodes (e.g., servers116, service appliance104) coupled to a network or other communication channel. For example, communication interface156may be used to send and receive network traffic such as data packets. Each communication interface156may send and receive data and/or signals according to any suitable standard such as Asynchronous Transfer Mode (ATM), Frame Relay, or Gigabit Ethernet (or other IEEE 802.3 standard). In a particular embodiment, communication interface156comprises one or more physical ports160that may each function as an ingress and/or egress port. As one example, communication interface156may comprise a plurality of Ethernet ports.

Processor148may be a microprocessor, controller, or any other suitable computing device, resource, or combination of hardware, stored software and/or encoded logic operable to provide, either alone or in conjunction with other components of network element108, network element functionality. In some embodiments, network element108may utilize multiple processors to perform the functions described herein.

Storage152may comprise any form of volatile or non-volatile memory including, without limitation, magnetic media (e.g., one or more tape drives), optical media, random access memory (RAM), read-only memory (ROM), flash memory, removable media, or any other suitable local or remote memory component or components. Storage152may store any suitable data or information utilized by network element108, including software embedded in a computer readable medium, and/or encoded logic incorporated in hardware or otherwise stored (e.g., firmware). Storage152may also store the results and/or intermediate results of the various calculations and determinations performed by processor148. As an example, software to perform the functions of the ISCMs164when executed by a processor may be stored in storage152. In the embodiment depicted, storage152also includes global forwarding policies database168which may be accessible by all of the ISCMs164of the various VDCs140as described earlier.

In the embodiment depicted, each VDC140includes its own instance of an ISCM164, a communication interface156with one or more physical ports160, and forwarding logic172. The ISCM may be capable of communicating the forwarding policies received from a service appliance104, another ISCM164, (e.g., of the same or a different network element108), or a network administrator to other portions of network element108(e.g., to forwarding logic172).

According to various embodiments, ISCM164may also offer various functionalities such as handling (i.e., accommodating, managing, processing, etc.) messages between a network element108or a VDC140of a network element and one or more service appliances104. For example, functions in association with such messages may concern high availability activities, timer events, packet switch stream, American Standard Code for Information Interchange (ASCII) generation, logging, event handling, health monitoring, debugging, etc.

After ports (e.g., appliance ports and network element (e.g., switch) ports) have been configured, ISCM164and a corresponding ISCC of service appliance104may perform auto-discovery and bootstrap to establish an appropriate control channel. After the control channel is established, applications in service appliance104may send control messages (e.g., using the UDP socket interface) to the ISCC through an application control plane. The application control plane generally encompasses one or more software components for performing workflow management, self-management, and other application control layer processes. The ISCC may forward the control messages to an ISCM164of network element108aover communication channel136. In example embodiments, ISCM164and the ISCC may communicate via UDP packets; however, various other protocols and formats may be accommodated by the teachings of the present disclosure. ISCM164may use processor148and storage152to perform functions associated with the service appliance104in network element108. Similarly, service appliance104may be provisioned with (or have access to) a processor and similar storage, which the ISCC may use to perform functions described herein in service appliance104.

Forwarding logic172may be operable to apply forwarding policies indicated by APBR requests (e.g., policies that may be automatically distributed to and implemented by the necessary network elements in a network without manual configuration at each network element) or user-specified traffic forwarding policies to traffic received via communication interface156and send the traffic processed by the policies to communication interface156for forwarding out of the appropriate port160of network element108. In the embodiment depicted, forwarding logic172includes parsing logic176, key construction logic180, and port selection logic184. In various embodiments, any suitable portion of forwarding logic172may comprise programmable logic (e.g., software/computer instructions executed by a processor), fixed logic, programmable digital logic (e.g., an FPGA, an EPROM, an EEPROM, or other device), an ASIC that includes digital logic, software, code, electronic instructions, or any suitable combination thereof. In a particular embodiment, forwarding logic172comprises an ASIC or other device that is operable to perform customized traffic forwarding in hardware by utilizing logic (e.g., one or more memories such as TCAM188) that is reprogrammable by an entity (e.g., ISCM164) based on traffic customization information (e.g., APBR requests or traffic forwarding policies received from a network administrator). In such an embodiment, the functions of parsing logic176, key construction logic180, and port selection logic184are performed in hardware by such logic (in contrast to an implementation where such functions may be performed through software instructions executed by a network processor). Reconfiguration of the logic may be performed by storing different values in memory of the forwarding logic172such as TCAM188or other memory element while the rest of the forwarding logic172remains fixed. In various embodiments, the values stored in the memory may provide control inputs to forwarding logic172, but are not typical instructions that are part of an instruction set executed by a processor. By implementing this logic in hardware, the network element108may process incoming traffic (e.g., switch/bridge or route the traffic) at much higher speeds (e.g., at line rate) than a device that utilizes a network processor to process incoming network traffic. In other embodiments, any of the operations of the various forwarding logic elements may be performed in software (e.g., with the use of a processor148).

Parsing logic176may be operable to receive packets from a port160of network element108. The parsing logic176may be configured to parse information from a received packet. Parsing logic176may be configured to parse any suitable information, such as one or more protocols associated with (e.g., included within) the packet (such as an L3 or L4 protocol), a source address (e.g., IP address, MAC address, or other address) of the packet, a destination address (e.g., IP address, MAC address, or other address) of the packet, one or more ports (e.g., source or destination L4 port) associated with the packet, a VLAN identifier, a QoS value, or other suitable information from the header or body of a packet. In some embodiments, the information to be parsed by parsing logic176is based on the information included within various forwarding policies implemented by network element108or a VDC thereof (which could include forwarding policies associated with various different ports of network element108). In some embodiments, the parsing logic176is configured on a port-by-port basis, such that packets from each port may be parsed based on the forwarding policies associated with that port.

The information parsed by parsing logic176is passed to key construction logic180. Key construction logic constructs a key from the output of the parsing logic176. The key may contain all or a portion of the information parsed from a packet. The key is then passed to the port selection logic184.

Prior to receiving a key associated with a data packet, forwarding logic172may receive forwarding policies from ISCM164and configure itself to implement the forwarding policies. For example, forwarding logic172may store forwarding policies associated with a particular port160in a content addressable memory, such as a TCAM188. A TCAM is a species of memory that is addressed by memory contents rather than address, and which provides very fast searching. A TCAM is a species of CAM in which the search can include “don't care” values that require only part of a search tag to be matched.

When a packet is received on a port160, the key generated by key construction logic180(and any other suitable information associated with the packet) may be passed to the port selection logic184. The port selection logic184uses the key to perform a lookup in the TCAM188. Port selection logic184will then forward the traffic through the appropriate port160of network element108based on a forwarding policy that that matches the information in the key from the packet (and has the highest priority if multiple forwarding policies match the key).

In accordance with various embodiments described herein, a forwarding policy may indicate that an incoming packet should be forwarded to the service appliance104. For example, the forwarding policy may indicate that the next hop IP address for the packet should be an IP address of the service appliance104. A routing table associated with the network element108(or the appropriate VDC140) may be modified accordingly, such that the packet may be routed from the network element108to the IP address of the service appliance104via a port160facing the service appliance104. In some embodiments, the routing table is stored in a separate memory (e.g., static random access memory) from the forwarding policies (e.g., TCAM188).

In various embodiments, ISCM164receives forwarding policies (e.g., via APBR requests) and converts the forwarding policies into a format suitable for use by forwarding logic208before communicating these policies to forwarding logic208. For example, as explained in greater detail in connection withFIG. 6, the forwarding policies may be used to generate one or more Access Control Lists (ACLs) and routemaps.

FIG. 4illustrates a block diagram of a system400having multiple L3 network hops between a service appliance104and one or more destination servers116in accordance with certain embodiments. In the embodiment depicted, system400includes a network element108bcoupled to client120via network124and to service appliance104via communication channel136. Network element108bmay be coupled to server farm128through another network element108c. Network elements108band108cmay have any suitable characteristics described herein in connection with network elements108and108a. Each network element108may be an L3 hop in the path from the service appliance104to the server farm128.

In such embodiments, the forwarding policy to send return traffic from the servers116to the service appliance104should be implemented by each L3 hop (i.e., network element108) to redirect the return traffic to the port through which the appliance can be reached. For example, in the embodiment depicted, if the forwarding policy is not applied to network element108c, then return traffic from server116to client device120might be routed from network element108cto a network node in the network124, thus bypassing network element108band service appliance104.

When a network element108(e.g.,108b) receives a forwarding policy, a network operation such as ping or traceroute may be used to determine the route a packet will take from the network element to the server116. For example, multiple UDP, Internet Control Message Protocol Echo Request, or TCP SYN packets may be addressed to the server116. Time-to-live (TTL) values of the packets (also known as hop limits) are used in determining the intermediate routers being traversed towards the destination server. From this route, network element108bmay determine a port through which the destination server116may be reached (i.e., the port through which the next hop may be reached). The forwarding policy will be applied on this port. The policy will be entered in the global forwarding policies database168and will also be sent to the network element that is the next hop (e.g., network element108c) in the route to the destination server116. When the network element108cat the next hop receives the forwarding policy, it will look up the port on which it can reach the destination server116, apply the policy on that port (e.g., by setting the next hop for return traffic received at the port to the IP address of the network element108that it received the forwarding policy from), and store the policy in its own database168. This process may be repeated for each network element108in the route to the destination server116.

Return traffic reaching each network element108will trigger the forwarding policy and will be redirected out of the port through which the service appliance104can be reached. With network element108c, this port will be coupled to network element108b. The forwarding policy on network element108bwill result in the packet being redirected to the service appliance104.

FIG. 5illustrates a block diagram of a system500having multiple L2 nodes and/or L3 network hops between a service appliance104and one or more destination servers116in accordance with certain embodiments. In the embodiment depicted, any particular network element108(or VDC thereof) between client120and a destination server may function as a router (e.g., as an L3 network hop) and/or as a switch (e.g., as an L2 node).

In such network configurations, a discovery protocol may be run by the ISCM instances of the network elements108to facilitate application of forwarding policies on the appropriate network elements108(or VDCs thereof) in order to direct return traffic from a destination server116back to the service appliance104that sent the traffic. The discovery protocol may result in one of the ISCM instances being selected to host a communication server. All other ISCM instances may communicate with the communication server (e.g., the host ISCM) using a client/server model. Thus, ISCM instances do not communicate network configuration information (e.g., forwarding policies) to each other directly, but would communicate the configuration information to the communication server, which would then communicate the configuration information to the other ISCM instances.

In various embodiments, any suitable L2 or L3 multicast protocol may be used by the ISCM instances164to discover each other ISCM instance164in the network. The discovery procedure may be performed at any suitable time such as on startup, when a new IMSC comes online, or when a host IMSC goes offline. Any suitable parameters of the ISCM instances may be shared with the other ISCM instances to facilitate selection of the host ISCM instance. In particular embodiments each ISCM may multicast an identifier that is unique to the ISCM. As one example, each ISCM instance may multicast an ISCM identifier comprising a number unique to the network element108that is running the ISCM instance (e.g., a chassis serial number of the network element) concatenated with an identifier of a VDC associated with the ISCM instance (or a default value if no VDC instances are running on the network element108running the ISCM).

Each ISCM may be configured to determine whether it should host the communication server based on the parameters received from the other ISCM instances. Similarly, each ISCM may determine which ISCM is hosting the communication server based on the received parameters. In one example, the ISCM having the lowest valued ISCM identifier is selected as the host, though other suitable methods may be used to select the host ISCM (e.g., the highest valued ISCM identifier, etc.).

The ISCM acting as the host may send out parameters that the other ISCMs (acting as clients) may use to communicate with the communication server hosted by the host ISCM. Any suitable communication protocol may be used to communicate between the client ISCMs and the communication server. In a particular embodiment, the Extensible Messaging and Presence Protocol (XMPP) is used and the host ISCM will configure the communication server to be an XMPP server and send out parameters associated with the XMPP server to the other ISCMs. In other embodiments, an L2 multicast mechanism or an L3 multicast or broadcast mechanism may be used instead of XMPP. In particular embodiments, the parameters associated with the communication server may be sent out by each ISCM during the discovery phase. That is, each ISCM may send parameters that would be needed by the other ISCMs if that ISCM were to host the communication server. For example, the parameters sent by one or more of the ISCMs may include (in addition to the aforementioned ISCM ID), an IP address associated with the ISCM (i.e., the IP address of the VDC or network element108running the ISCM), a port to be used to communicate with the other network elements (e.g., an XMPP server port), and any other parameters needed to communicate from or with the communication server. In some embodiments, the IP addresses associated with the ISCMs are exchanged after the ISCMs are discovered.

All of the other ISCMs may connect to the communication server via the host ISCM. When an ISCM receives a forwarding policy from an ISCC of a connected service appliance104, the forwarding policy may be programmed on the appropriate ports of the network element108hosting the ISCM (e.g., via the methods described herein with respect toFIGS. 1 and 2). The ISCM may also send the forwarding policy to the other ISCMs via the communication server. In one example, the communication server may broadcast the forwarding policy to all the other ISCMs. In another example, the communication server may withhold the forwarding policy from one or more of the ISCMs in the network based on information that indicates that the policy should not be applied by the particular ISCM (e.g., the communication server might not send the forwarding policy to an ISCM of a network element that does not transport traffic for a VLAN associated with the forwarding policy).

The receiving ISCMs may apply this policy to one or more ports through which the destination server is reachable if the policy matches particular parameters (e.g., VLAN parameters, route parameters). If the parameters of the ISCM don't match the forwarding policy (e.g., if the destination server is not reachable from the network element associated with the ISCM or if the policy is associated with a VLAN not transported by the network element), the ISCM may store the policy in memory (e.g., database168) without programming any ports of the network element108. If the network configuration later changes such that the parameters do match, the policy may then be applied to the appropriate ports of the network element108.

The communication server may exchange heartbeat messages with the other ISCMs via the communication protocol in use (e.g., XMPP). If it is determined that the communication server has gone offline (e.g., if a heartbeat message is not received within a predetermined time span), a new host ISCM is selected based on the information shared during the discovery phase and the new host ISCM will configure a communication server and share the associated communication parameters with the other ISCMs.

In some embodiments, when a new network element comes online within the network, the ISCM(s) of the network element participates in the discovery protocol by sending the necessary information to the other ISCMs in the network. If the new ISCM has parameters that make it suitable to host the communication server, then it will configure itself accordingly and the other ISCMs will transition to communicate with the new communication server. If the new ISCM is not suitable to host the communication server, then at least one of the other ISCMs will notify the new ISCM of the necessary details of the communication server so that it can receive the existing forwarding policies from the communication server.

Although the above examples, focus on communication of forwarding policies between ISCMs, the communication scheme may be used to communicate any suitable configuration information (e.g., any suitable network policies) among ISCMs.

FIG. 6illustrates an example method600for configuring one or more network elements108for APBR in accordance with certain embodiments. At step604, an APBR request is received. For example, the APBR request may be received from service appliance104. The APBR request may include information indicating one or more forwarding policies to be applied at one or more network elements. In some embodiments, a control channel of network element108is used to automate the task of creating the forwarding policies. Service appliance104, as a function of its configuration, knows the IP address of the servers116in server farm128, and may send this information to network element108in an APBR request. In some embodiments, the APBR request may specify an IP address, port, and protocol of the destination server.

At step608, it is determined whether the APBR request conflicts with any other APBR requests applied by the network element (or VDC thereof). For example, if an APBR request specifies the same destination server IP address, port, and protocol as an applied APBR request, then it may be considered to conflict with that APBR request. If there are no conflicting APBR requests, then the method moves to step616. If there is a conflicting APBR request, then it is determined at step612whether the received APBR request takes precedence over the applied APBR request. Any suitable method may be used to determine which APBR request should take precedence. In one example, an APBR request received at a network element from a service appliance that is attached to that network element takes precedence over an APBR request received from another network element. If the received APBR request takes precedence, the method moves to step616, otherwise the method will move to step624.

At step616, the ports through which the destination server116is reachable are determined. In particular embodiments, an ISCM of each VDC of a network element108may determine which of its ports may reach the destination server116.

At step620, a forwarding policy based on the APBR request is applied to each of the ports identified at step616. In some embodiments, this may involve creating an Access Control List (ACL) and an associated routemap. The ACL may have matching criteria comprising the protocol used by the server116to send packets, the IP address of the server116, and the port of the server116. The ACL will permit all traffic matching the criteria (such that it is not blocked by network element108). The specified protocol in the ACL may include, by way of nonlimiting example, any L4 protocol such as TCP, UDP, or both TCP and UDP.

A routemap may be associated with the ACL so as to set the nexthop IP for traffic matching the ACL criteria. This association may be stored in any suitable location, such as database168. In the case of a first ISCM that is closest to (e.g., connected to) the service appliance104, the next hop IP address is set to the IP address of the service appliance104. In the case of a second ISCM that is in a network path between the first ISCM and the destination server, the next hop IP address may be set to the IP address of an ISCM upstream from the second ISCM (e.g., the IP address of the first ISCM or a different ISCM between the first ISCM and the second ISCM). The routemap is then applied to all the ports of the network element108that are identified as being able to reach the destination server116. Thus, in the case of a single APBR request applicable to multiple nexthop interfaces (i.e., ports) to the real server, the routemap is applied on each of the nexthop interfaces. When the nexthop interface already has a route map assigned to it, a sequence to an existing routemap may be appended.

At step624, the APBR request is forwarded to one or more other network elements108on the possible network paths to the destination server116. These network elements may perform steps similar to those described above.

At step628, data packets from the server116to client120are forwarded by the network element108at which the APBR request was implemented to the service appliance104, which modifies the source address of the packets to match the address of the service appliance104and then sends the packets back through the network element108to the client120.

At step632, forwarding policies based on the APBR requests are deleted. In some embodiments, various events may trigger an automatic purge of forwarding policies. For example, forwarding policies may be purged in response to a server116becoming unavailable or in response to events associated with the service appliance, such as health monitoring failure, service appliance reboot, forced CLI or user-triggered shutdown of the service, or other suitable events. In various embodiments, if one of these events occurs, the routemap may be removed from the ports and the routemap and the ACL are deleted. The network element108may also instruct downstream network elements108to delete their forwarding policies associated with the service appliance and/or server116.

Some of the steps illustrated inFIG. 6may be repeated, combined, modified or deleted where appropriate, and additional steps may also be included. Additionally, steps may be performed in any suitable order without departing from the scope of particular embodiments.

FIG. 7illustrates an example method700for configuring a communication server for a network in accordance with certain embodiments. At step704, ISCM instance identifiers are multicast among the ISCM instances of the network. At step708, a host ISCM instance is selected to host a communication server. At step712, the host ISCM share the configuration parameters of the communication server with the other ISCM instances. In alternative embodiments, this information may be shared during step704along with the ISCM instance identifiers.

At step712, network configuration data may be communicated amongst the ISCMs via the communication server. For example, APBR requests may be communicated from an ISCM coupled to a service appliance104to one or more of the other ISCMs in the network. Concurrently, heartbeat messages may be exchanged by the communication server at step720. Based on these messages it may be determined at step724whether the communication server is still online. If the communication server is still online, the ISCMs may continue to communicate through the communication server to other ISCMs. If the communication server has gone offline, a different ISCM is selected to the host the communications server at step708. Communications may then resume at step716through the new communications server.

Some of the steps illustrated inFIG. 7may be repeated, combined, modified or deleted where appropriate, and additional steps may also be included. Additionally, steps may be performed in any suitable order without departing from the scope of particular embodiments.

It is also important to note that the steps inFIGS. 6-7illustrate only some of the possible scenarios that may be executed by, or within, the network elements described herein. Some of these steps may be deleted or removed where appropriate, or these steps may be modified or changed considerably without departing from the scope of the present disclosure. In addition, a number of these operations may have been described as being executed concurrently with, or in parallel to, one or more additional operations. However, the timing of these operations may be altered considerably. The preceding operational flows have been offered for purposes of example and discussion. Substantial flexibility is provided by the network elements108in that any suitable arrangements, chronologies, configurations, and timing mechanisms may be provided without departing from the teachings of the present disclosure.