Patent ID: 12224998

The features and advantages of the present solution will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements

DETAILED DESCRIPTION

For purposes of reading the description of the various embodiments below, the following descriptions of the sections of the specification and their respective contents may be helpful:Section A describes a network environment and computing environment which may be useful for practicing embodiments described herein;Section B describes embodiments of systems and methods for delivering a computing environment to a remote user;Section C describes embodiments of systems and methods for virtualizing an application delivery controller;Section D describes embodiments of systems and methods for providing a clustered appliance architecture environment; andSection E describes embodiments of systems and methods for selecting gateways for reconnection upon detection of reachability issues on backend resources.
A. Network and Computing Environment

Referring toFIG.1A, an illustrative network environment100is depicted. Network environment100may include one or more clients102(1)-102(n) (also generally referred to as local machine(s)102or client(s)102) in communication with one or more servers106(1)-106(n) (also generally referred to as remote machine(s)106or server(s)106) via one or more networks104(1)-104n(generally referred to as network(s)104). In some embodiments, a client102may communicate with a server106via one or more appliances200(1)-200n(generally referred to as appliance(s)200or gateway(s)200).

Although the embodiment shown inFIG.1Ashows one or more networks104between clients102and servers106, in other embodiments, clients102and servers106may be on the same network104. The various networks104may be the same type of network or different types of networks. For example, in some embodiments, network104(1) may be a private network such as a local area network (LAN) or a company Intranet, while network104(2) and/or network104(n) may be a public network, such as a wide area network (WAN) or the Internet. In other embodiments, both network104(1) and network104(n) may be private networks. Networks104may employ one or more types of physical networks and/or network topologies, such as wired and/or wireless networks, and may employ one or more communication transport protocols, such as transmission control protocol (TCP), internet protocol (IP), user datagram protocol (UDP) or other similar protocols.

As shown inFIG.1A, one or more appliances200may be located at various points or in various communication paths of network environment100. For example, appliance200may be deployed between two networks104(1) and104(2), and appliances200may communicate with one another to work in conjunction to, for example, accelerate network traffic between clients102and servers106. In other embodiments, the appliance200may be located on a network104. For example, appliance200may be implemented as part of one of clients102and/or servers106. In an embodiment, appliance200may be implemented as a network device such as NetScaler® products sold by Citrix Systems, Inc. of Fort Lauderdale, FL.

As shown inFIG.1A, one or more servers106may operate as a server farm38. Servers106of server farm38may be logically grouped, and may either be geographically co-located (e.g., on premises) or geographically dispersed (e.g., cloud based) from clients102and/or other servers106. In an embodiment, server farm38executes one or more applications on behalf of one or more of clients102(e.g., as an application server), although other uses are possible, such as a file server, gateway server, proxy server, or other similar server uses. Clients102may seek access to hosted applications on servers106.

As shown inFIG.1A, in some embodiments, appliances200may include, be replaced by, or be in communication with, one or more additional appliances, such as WAN optimization appliances205(1)-205(n), referred to generally as WAN optimization appliance(s)205. For example, WAN optimization appliance205may accelerate, cache, compress or otherwise optimize or improve performance, operation, flow control, or quality of service of network traffic, such as traffic to and/or from a WAN connection, such as optimizing Wide Area File Services (WAFS), accelerating Server Message Block (SMB) or Common Internet File System (CIFS). In some embodiments, appliance205may be a performance enhancing proxy or a WAN optimization controller. In one embodiment, appliance205may be implemented as CloudBridge® products sold by Citrix Systems, Inc. of Fort Lauderdale, FL.

Referring toFIG.1B, an example network environment100′ for delivering and/or operating a computing network environment on a client102is shown. As shown inFIG.1B, a server106may include an application delivery system190for delivering a computing environment, application, and/or data files to one or more clients102. Client102may include client agent120and computing environment15. Computing environment15may execute or operate an application,16, that accesses, processes or uses a data file17. Computing environment15, application16and/or data file17may be delivered to the client102via appliance200and/or the server106.

Appliance200may accelerate delivery of all or a portion of computing environment15to a client102, for example by the application delivery system190. For example, appliance200may accelerate delivery of a streaming application and data file processable by the application from a data center to a remote user location by accelerating transport layer traffic between a client102and a server106. Such acceleration may be provided by one or more techniques, such as: 1) transport layer connection pooling, 2) transport layer connection multiplexing, 3) transport control protocol buffering, 4) compression, 5) caching, or other techniques. Appliance200may also provide load balancing of servers106to process requests from clients102, act as a proxy or access server to provide access to the one or more servers106, provide security and/or act as a firewall between a client102and a server106, provide Domain Name Service (DNS) resolution, provide one or more virtual servers or virtual internet protocol servers, and/or provide a secure virtual private network (VPN) connection from a client102to a server106, such as a secure socket layer (SSL) VPN connection and/or provide encryption and decryption operations.

Application delivery management system190may deliver computing environment15to a user (e.g., client102), remote or otherwise, based on authentication and authorization policies applied by policy engine195. A remote user may obtain a computing environment and access to server stored applications and data files from any network-connected device (e.g., client102). For example, appliance200may request an application and data file from server106. In response to the request, application delivery system190and/or server106may deliver the application and data file to client102, for example via an application stream to operate in computing environment15on client102, or via a remote-display protocol or otherwise via remote-based or server-based computing. In an embodiment, application delivery system190may be implemented as any portion of the Citrix Workspace Suite™ by Citrix Systems, Inc., such as XenApp® or XenDesktop®.

Policy engine195may control and manage the access to, and execution and delivery of, applications. For example, policy engine195may determine the one or more applications a user or client102may access and/or how the application should be delivered to the user or client102, such as a server-based computing, streaming or delivering the application locally to the client50for local execution.

For example, in operation, a client102may request execution of an application (e.g., application16′) and application delivery system190of server106determines how to execute application16′, for example based upon credentials received from client102and a user policy applied by policy engine195associated with the credentials. For example, application delivery system190may enable client102to receive application-output data generated by execution of the application on a server106, may enable client102to execute the application locally after receiving the application from server106, or may stream the application via network104to client102. For example, in some embodiments, the application may be a server-based or a remote-based application executed on server106on behalf of client102. Server106may display output to client102using a thin-client or remote-display protocol, such as the Independent Computing Architecture (ICA) protocol by Citrix Systems, Inc. of Fort Lauderdale, FL. The application may be any application related to real-time data communications, such as applications for streaming graphics, streaming video and/or audio or other data, delivery of remote desktops or workspaces or hosted services or applications, for example infrastructure as a service (IaaS), workspace as a service (WaaS), software as a service (SaaS) or platform as a service (PaaS).

One or more of servers106may include a performance monitoring service or agent197. In some embodiments, a dedicated one or more servers106may be employed to perform performance monitoring. Performance monitoring may be performed using data collection, aggregation, analysis, management and reporting, for example by software, hardware or a combination thereof. Performance monitoring may include one or more agents for performing monitoring, measurement and data collection activities on clients102(e.g., client agent120), servers106(e.g., agent197) or an appliances200and/or205(agent not shown). In general, monitoring agents (e.g.,120and/or197) execute transparently (e.g., in the background) to any application and/or user of the device. In some embodiments, monitoring agent197includes any of the product embodiments referred to as EdgeSight by Citrix Systems, Inc. of Fort Lauderdale, FL.

The monitoring agents120and197may monitor, measure, collect, and/or analyze data on a predetermined frequency, based upon an occurrence of given event(s), or in real time during operation of network environment100. The monitoring agents may monitor resource consumption and/or performance of hardware, software, and/or communications resources of clients102, networks104, appliances200and/or205, and/or servers106. For example, network connections such as a transport layer connection, network latency, bandwidth utilization, end-user response times, application usage and performance, session connections to an application, cache usage, memory usage, processor usage, storage usage, database transactions, client and/or server utilization, active users, duration of user activity, application crashes, errors, or hangs, the time required to log-in to an application, a server, or the application delivery system, and/or other performance conditions and metrics may be monitored.

The monitoring agents120and197may provide application performance management for application delivery system190. For example, based upon one or more monitored performance conditions or metrics, application delivery system190may be dynamically adjusted, for example periodically or in real-time, to optimize application delivery by servers106to clients102based upon network environment performance and conditions.

In described embodiments, clients102, servers106, and appliances200and205may be deployed as and/or executed on any type and form of computing device, such as any desktop computer, laptop computer, or mobile device capable of communication over at least one network and performing the operations described herein. For example, clients102, servers106and/or appliances200and205may each correspond to one computer, a plurality of computers, or a network of distributed computers such as computer101shown inFIG.1C.

As shown inFIG.1C, computer101may include one or more processors103, volatile memory122(e.g., RAM), non-volatile memory128(e.g., one or more hard disk drives (HDDs) or other magnetic or optical storage media, one or more solid state drives (SSDs) such as a flash drive or other solid state storage media, one or more hybrid magnetic and solid state drives, and/or one or more virtual storage volumes, such as a cloud storage, or a combination of such physical storage volumes and virtual storage volumes or arrays thereof), user interface (UI)123, one or more communications interfaces118, and communication bus150. User interface123may include graphical user interface (GUI)124(e.g., a touchscreen, a display, etc.) and one or more input/output (I/O) devices126(e.g., a mouse, a keyboard, etc.). Non-volatile memory128stores operating system115, one or more applications116, and data117such that, for example, computer instructions of operating system115and/or applications116are executed by processor(s)103out of volatile memory122. Data may be entered using an input device of GUI124or received from I/O device(s)126. Various elements of computer101may communicate via communication bus150. Computer101as shown inFIG.1Cis shown merely as an example, as clients102, servers106and/or appliances200and205may be implemented by any computing or processing environment and with any type of machine or set of machines that may have suitable hardware and/or software capable of operating as described herein.

Processor(s)103may be implemented by one or more programmable processors executing one or more computer programs to perform the functions of the system. As used herein, the term “processor” describes an electronic circuit that performs a function, an operation, or a sequence of operations. The function, operation, or sequence of operations may be hard coded into the electronic circuit or soft coded by way of instructions held in a memory device. A “processor” may perform the function, operation, or sequence of operations using digital values or using analog signals. In some embodiments, the “processor” can be embodied in one or more application specific integrated circuits (ASICs), microprocessors, digital signal processors, microcontrollers, field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), multi-core processors, or general-purpose computers with associated memory. The “processor” may be analog, digital or mixed-signal. In some embodiments, the “processor” may be one or more physical processors or one or more “virtual” (e.g., remotely located or “cloud”) processors.

Communications interfaces118may include one or more interfaces to enable computer101to access a computer network such as a LAN, a WAN, or the Internet through a variety of wired and/or wireless or cellular connections.

In described embodiments, a first computing device101may execute an application on behalf of a user of a client computing device (e.g., a client102), may execute a virtual machine, which provides an execution session within which applications execute on behalf of a user or a client computing device (e.g., a client102), such as a hosted desktop session, may execute a terminal services session to provide a hosted desktop environment, or may provide access to a computing environment including one or more of: one or more applications, one or more desktop applications, and one or more desktop sessions in which one or more applications may execute.

B. Appliance Architecture

FIG.2shows an example embodiment of appliance200. As described herein, appliance200may be implemented as a server, gateway, router, switch, bridge or other type of computing or network device. As shown inFIG.2, an embodiment of appliance200may include a hardware layer206and a software layer205divided into a user space202and a kernel space204. Hardware layer206provides the hardware elements upon which programs and services within kernel space204and user space202are executed and allow programs and services within kernel space204and user space202to communicate data both internally and externally with respect to appliance200. As shown inFIG.2, hardware layer206may include one or more processing units262for executing software programs and services, memory264for storing software and data, network ports266for transmitting and receiving data over a network, and encryption processor260for encrypting and decrypting data such as in relation to Secure Socket Layer (SSL) or Transport Layer Security (TLS) processing of data transmitted and received over the network.

An operating system of appliance200allocates, manages, or otherwise segregates the available system memory into kernel space204and user space202. Kernel space204is reserved for running kernel230, including any device drivers, kernel extensions or other kernel related software. As known to those skilled in the art, kernel230is the core of the operating system, and provides access, control, and management of resources and hardware-related elements of application. Kernel space204may also include a number of network services or processes working in conjunction with cache manager232.

Appliance200may include one or more network stacks267, such as a TCP/IP based stack, for communicating with client(s)102, server(s)106, network(s)104, and/or other appliances200or205. For example, appliance200may establish and/or terminate one or more transport layer connections between clients102and servers106. Each network stack267may include a buffer for queuing one or more network packets for transmission by appliance200.

Kernel space204may include cache manager232, packet engine240, encryption engine234, policy engine236and compression engine238. In other words, one or more of processes232,240,234,236and238run in the core address space of the operating system of appliance200, which may reduce the number of data transactions to and from the memory and/or context switches between kernel mode and user mode, for example since data obtained in kernel mode may not need to be passed or copied to a user process, thread or user level data structure.

Cache manager232may duplicate original data stored elsewhere or data previously computed, generated or transmitted to reduce the access time of the data. In some embodiments, the cache manager232may be a data object in memory264of appliance200, or may be a physical memory having a faster access time than memory264.

Policy engine236may include a statistical engine or other configuration mechanism to allow a user to identify, specify, define or configure a caching policy and access, control and management of objects, data or content being cached by appliance200, and define or configure security, network traffic, network access, compression or other functions performed by appliance200.

Encryption engine234may process any security related protocol, such as SSL or TLS. For example, encryption engine234may encrypt and decrypt network packets, or any portion thereof, communicated via appliance200, may setup or establish SSL, TLS or other secure connections, for example between client102, server106, and/or other appliances200or205. In some embodiments, encryption engine234may use a tunneling protocol to provide a VPN between a client102and a server106. In some embodiments, encryption engine234is in communication with encryption processor260. Compression engine238compresses network packets bi-directionally between clients102and servers106and/or between one or more appliances200.

Packet engine240may manage kernel-level processing of packets received and transmitted by appliance200via network stacks267to send and receive network packets via network ports266. Packet engine240may operate in conjunction with encryption engine234, cache manager232, policy engine236and compression engine238, for example to perform encryption/decryption, traffic management such as request-level content switching and request-level cache redirection, and compression and decompression of data.

User space202is a memory area or portion of the operating system used by user mode applications or programs otherwise running in user mode. A user mode application may not access kernel space204directly and uses service calls in order to access kernel services. User space202may include graphical user interface (GUI)210, a command line interface (CLI)212, shell services214, health monitor216, and daemon services218. GUI210and CLI212enable a system administrator or other user to interact with and control the operation of appliance200, such as via the operating system of appliance200. Shell services214include programs, services, tasks, processes or executable instructions to support interaction with appliance200by a user via the GUI210and/or CLI212.

Health monitor216monitors, checks, reports and ensures that network systems are functioning properly and that users are receiving requested content over a network, for example by monitoring activity of appliance200. In some embodiments, health monitor216intercepts and inspects any network traffic passed via appliance200. For example, health monitor216may interface with one or more of encryption engine234, cache manager232, policy engine236, compression engine238, packet engine240, daemon services218, and shell services214to determine a state, status, operating condition, or health of any portion of the appliance200. Further, health monitor216may determine whether a program, process, service or task is active and currently running, check status, error or history logs provided by any program, process, service or task to determine any condition, status or error with any portion of appliance200. Additionally, health monitor216may measure and monitor the performance of any application, program, process, service, task or thread executing on appliance200.

Daemon services218are programs that run continuously or in the background and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests to other programs or processes, such as another daemon service218as appropriate.

As described herein, appliance200may relieve servers106of much of the processing load caused by repeatedly opening and closing transport layers connections to clients102by opening one or more transport layer connections with each server106and maintaining these connections to allow repeated data accesses by clients via the Internet (e.g., “connection pooling”). To perform connection pooling, appliance200may translate or multiplex communications by modifying sequence numbers and acknowledgment numbers at the transport layer protocol level (e.g., “connection multiplexing”). Appliance200may also provide switching or load balancing for communications between the client102and server106.

As described herein, each client102may include client agent120for establishing and exchanging communications with appliance200and/or server106via a network104. Client102may have installed and/or execute one or more applications that are in communication with network104. Client agent120may intercept network communications from a network stack used by the one or more applications. For example, client agent120may intercept a network communication at any point in a network stack and redirect the network communication to a destination desired, managed or controlled by client agent120, for example to intercept and redirect a transport layer connection to an IP address and port controlled or managed by client agent120. Thus, client agent120may transparently intercept any protocol layer below the transport layer, such as the network layer, and any protocol layer above the transport layer, such as the session, presentation or application layers. Client agent120can interface with the transport layer to secure, optimize, accelerate, route or load-balance any communications provided via any protocol carried by the transport layer.

In some embodiments, client agent120is implemented as an Independent Computing Architecture (ICA) client developed by Citrix Systems, Inc. of Fort Lauderdale, FL. Client agent120may perform acceleration, streaming, monitoring, and/or other operations. For example, client agent120may accelerate streaming an application from a server106to a client102. Client agent120may also perform end-point detection/scanning and collect end-point information about client102for appliance200and/or server106. Appliance200and/or server106may use the collected information to determine and provide access, authentication and authorization control of the client's connection to network104. For example, client agent120may identify and determine one or more client-side attributes, such as: the operating system and/or a version of an operating system, a service pack of the operating system, a running service, a running process, a file, presence or versions of various applications of the client, such as antivirus, firewall, security, and/or other software.

C. Systems and Methods for Providing Virtualized Application Delivery Controller

Referring now toFIG.3, a block diagram of a virtualized environment300is shown. As shown, a computing device302in virtualized environment300includes a virtualization layer303, a hypervisor layer304, and a hardware layer307. Hypervisor layer304includes one or more hypervisors (or virtualization managers)301that allocates and manages access to a number of physical resources in hardware layer307(e.g., physical processor(s)321and physical disk(s)328) by at least one virtual machine (VM) (e.g., one of VMs306) executing in virtualization layer303. Each VM306may include allocated virtual resources such as virtual processors332and/or virtual disks342, as well as virtual resources such as virtual memory and virtual network interfaces. In some embodiments, at least one of VMs306may include a control operating system (e.g.,305) in communication with hypervisor301and used to execute applications for managing and configuring other VMs (e.g., guest operating systems310) on device302.

In general, hypervisor(s)301may provide virtual resources to an operating system of VMs306in any manner that simulates the operating system having access to a physical device. Thus, hypervisor(s)301may be used to emulate virtual hardware, partition physical hardware, virtualize physical hardware, and execute virtual machines that provide access to computing environments. In an illustrative embodiment, hypervisor(s)301may be implemented as a XEN hypervisor, for example as provided by the open source Xen.org community. In an illustrative embodiment, device302executing a hypervisor that creates a virtual machine platform on which guest operating systems may execute is referred to as a host server. In such an embodiment, device302may be implemented as a XEN server as provided by Citrix Systems, Inc., of Fort Lauderdale, FL.

Hypervisor301may create one or more VMs306in which an operating system (e.g., control operating system305and/or guest operating system310) executes. For example, the hypervisor301loads a virtual machine image to create VMs306to execute an operating system. Hypervisor301may present VMs306with an abstraction of hardware layer307, and/or may control how physical capabilities of hardware layer307are presented to VMs306. For example, hypervisor(s)301may manage a pool of resources distributed across multiple physical computing devices.

In some embodiments, one of VMs306(e.g., the VM executing control operating system305) may manage and configure other of VMs306, for example by managing the execution and/or termination of a VM and/or managing allocation of virtual resources to a VM. In various embodiments, VMs may communicate with hypervisor(s)301and/or other VMs via, for example, one or more Application Programming Interfaces (APIs), shared memory, and/or other techniques.

In general, VMs306may provide a user of device302with access to resources within virtualized computing environment300, for example, one or more programs, applications, documents, files, desktop and/or computing environments, or other resources. In some embodiments, VMs306may be implemented as fully virtualized VMs that are not aware that they are virtual machines (e.g., a Hardware Virtual Machine or HVM). In other embodiments, the VM may be aware that it is a virtual machine, and/or the VM may be implemented as a paravirtualized (PV) VM.

Although shown inFIG.3as including a single virtualized device302, virtualized environment300may include a plurality of networked devices in a system in which at least one physical host executes a virtual machine. A device on which a VM executes may be referred to as a physical host and/or a host machine. For example, appliance200may be additionally or alternatively implemented in a virtualized environment300on any computing device, such as a client102, server106or appliance200. Virtual appliances may provide functionality for availability, performance, health monitoring, caching and compression, connection multiplexing and pooling and/or security processing (e.g., firewall, VPN, encryption/decryption, etc.), similarly as described in regard to appliance200.

In some embodiments, a server may execute multiple virtual machines306, for example on various cores of a multi-core processing system and/or various processors of a multiple processor device. For example, although generally shown herein as “processors” (e.g., inFIGS.1C,2and3), one or more of the processors may be implemented as either single- or multi-core processors to provide a multi-threaded, parallel architecture and/or multi-core architecture. Each processor and/or core may have or use memory that is allocated or assigned for private or local use that is only accessible by that processor/core, and/or may have or use memory that is public or shared and accessible by multiple processors/cores. Such architectures may allow work, task, load or network traffic distribution across one or more processors and/or one or more cores (e.g., by functional parallelism, data parallelism, flow-based data parallelism, etc.).

Further, instead of (or in addition to) the functionality of the cores being implemented in the form of a physical processor/core, such functionality may be implemented in a virtualized environment (e.g., 300) on a client102, server106or appliance200, such that the functionality may be implemented across multiple devices, such as a cluster of computing devices, a server farm or network of computing devices, etc. The various processors/cores may interface or communicate with each other using a variety of interface techniques, such as core to core messaging, shared memory, kernel APIs, etc.

In embodiments employing multiple processors and/or multiple processor cores, described embodiments may distribute data packets among cores or processors, for example to balance the flows across the cores. For example, packet distribution may be based upon determinations of functions performed by each core, source and destination addresses, and/or whether: a load on the associated core is above a predetermined threshold; the load on the associated core is below a predetermined threshold; the load on the associated core is less than the load on the other cores; or any other metric that can be used to determine where to forward data packets based in part on the amount of load on a processor.

For example, data packets may be distributed among cores or processes using receive-side scaling (RSS) in order to process packets using multiple processors/cores in a network. RSS generally allows packet processing to be balanced across multiple processors/cores while maintaining in-order delivery of the packets. In some embodiments, RSS may use a hashing scheme to determine a core or processor for processing a packet.

The RSS may generate hashes from any type and form of input, such as a sequence of values. This sequence of values can include any portion of the network packet, such as any header, field or payload of network packet, and include any tuples of information associated with a network packet or data flow, such as addresses and ports. The hash result or any portion thereof may be used to identify a processor, core, engine, etc., for distributing a network packet, for example via a hash table, indirection table, or other mapping technique.

D. Systems and Methods for Providing a Distributed Cluster Architecture

Although shown inFIGS.1A and1Bas being single appliances, appliances200may be implemented as one or more distributed or clustered appliances. Individual computing devices or appliances may be referred to as nodes of the cluster. A centralized management system may perform load balancing, distribution, configuration, or other tasks to allow the nodes to operate in conjunction as a single computing system. Such a cluster may be viewed as a single virtual appliance or computing device.FIG.4shows a block diagram of an illustrative computing device cluster or appliance cluster400. A plurality of appliances200or other computing devices (e.g., nodes) may be joined into a single cluster400. Cluster400may operate as an application server, network storage server, backup service, or any other type of computing device to perform many of the functions of appliances200and/or205.

In some embodiments, each appliance200of cluster400may be implemented as a multi-processor and/or multi-core appliance, as described herein. Such embodiments may employ a two-tier distribution system, with one appliance if the cluster distributing packets to nodes of the cluster, and each node distributing packets for processing to processors/cores of the node. In many embodiments, one or more of appliances200of cluster400may be physically grouped or geographically proximate to one another, such as a group of blade servers or rack mount devices in a given chassis, rack, and/or data center. In some embodiments, one or more of appliances200of cluster400may be geographically distributed, with appliances200not physically or geographically co-located. In such embodiments, geographically remote appliances may be joined by a dedicated network connection and/or VPN. In geographically distributed embodiments, load balancing may also account for communications latency between geographically remote appliances.

In some embodiments, cluster400may be considered a virtual appliance, grouped via common configuration, management, and purpose, rather than as a physical group. For example, an appliance cluster may comprise a plurality of virtual machines or processes executed by one or more servers.

As shown inFIG.4, appliance cluster400may be coupled to a client-side network104via client data plane402, for example to transfer data between clients102and appliance cluster400. Client data plane402may be implemented a switch, hub, router, or other similar network device internal or external to cluster400to distribute traffic across the nodes of cluster400. For example, traffic distribution may be performed based on equal-cost multi-path (ECMP) routing with next hops configured with appliances or nodes of the cluster, open-shortest path first (OSPF), stateless hash-based traffic distribution, link aggregation (LAG) protocols, or any other type and form of flow distribution, load balancing, and routing.

Appliance cluster400may be coupled to a second network104′ via server data plane404. Similarly to client data plane402, server data plane404may be implemented as a switch, hub, router, or other network device that may be internal or external to cluster400. In some embodiments, client data plane402and server data plane404may be merged or combined into a single device.

In some embodiments, each appliance200of cluster400may be connected via an internal communication network or backplane406. Backplane406may enable inter-node or inter-appliance control and configuration messages, for inter-node forwarding of traffic, and/or for communicating configuration and control traffic from an administrator or user to cluster400. In some embodiments, backplane406may be a physical network, a VPN or tunnel, or a combination thereof.

E. Systems and Methods for Selecting Gateways for Reconnection Upon Detection of Reachability Issues on Backend Resources

Referring now toFIG.5, depicted is a system500for selecting gateways for reconnection upon detection of reachability issues on backend resources. In overview, the system500may include one or more clients102A-N (hereinafter generally referred to as clients102), one or more servers106A-N (hereinafter generally referred to as servers106), one or more appliances200A-N (hereinafter generally referred to as appliances200and generally referred to as gateways, proxies, or intermediary devices) deployed between the clients102and the servers106, and at least one management agent535, among others. At least one of the clients102may execute, have, or include at least one network connectivity manager505. The network connectivity manager505may include at least one profile handler510, at least one gateway connector515, at least one resource monitor520, at least one failover handler525, and at least one storage530, among others. The client102may be configured or provided with the network connectivity manager505by a network administrator of the network104or104′. In some embodiments, the management agent535may reside on a device separate from the appliances200or may be a part of one or more of the appliances200.

The systems and methods of the present solution may be implemented in any type and form of device, including clients102, servers106, appliances200, and the management agent535. As referenced herein, a “server” may sometimes refer to any device in a client-server relationship, e.g., an appliance200in a handshake with a client device102. The present systems and methods may be implemented in any intermediary device or gateway, such as any embodiments of the appliance or devices200described herein. Some portion of the present systems and methods may be implemented as part of a packet processing engine and/or virtual server of an appliance, for instance. The systems and methods may be implemented in any type and form of environment, including multi-core appliances, virtualized environments and/or clustered environments described herein.

Referring now toFIG.6A, depicted is a block diagram of a process600for handling profiles in the system500for selecting gateways. The process600may correspond to prior to establishment of a connection between the client102and one of the appliances200. Under the process600, the profile handler510executing on the client102may retrieve, identify, or otherwise receive at least one configuration profile605(generally referred herein as a profile). In some embodiments, the profile handler510may receive the configuration profile605from a network administrator or another entity associated with the appliances200or servers106. The receipt from the network administrator may be prior to connection with any of the appliances200of the network104or104′. In some embodiments, the profile handler510may receive the configuration profile605upon establish a connection with at least one of the appliances200. The establishment of the connection will be detailed herein below in conjunction with the gateway connector515. Upon receipt, the profile handler510may parse the configuration profile605to extract or identify the contents therein.

The configuration profile605may specify, define, or otherwise identify at least one gateway list610. The gateway list610may include or identify a set of gateway identifiers615A-N (hereinafter generally referred to as gateway identifiers615). Each gateway identifier615may identify, reference, or correspond to a respective appliance200via which the client102is permitted to connect in accessing one of the servers106identified in the server list620. At least one of the gateway identifiers615(e.g., gateway identifier615A) may correspond to a primary appliance200(e.g., appliance200A) with which the client102is to first connect in accessing the server106. At least one of the gateway identifiers615(e.g., the gateway identifier615B) may correspond to an alternate appliance200(e.g., appliance200B) with which the client102can connect when one or more servers106are unreachable via the primary appliance200. In some embodiments, the gateway list610may define or specify a sequence for the gateway identifiers615corresponding to the appliances200to which the client102is to connect. The gateway identifier615may include, for example, a domain name (e.g., a full qualified domain name (FQDN) in the form of a uniform resource locator (URL)) or a network address (e.g., an Internet Protocol (IP) address or a media access control (MAC) address), among others corresponding to the respective appliance200.

In addition, the configuration profile605may specify, define, or otherwise identify at least one server list620. Furthermore, the server list620of the configuration profile605may include or identify one or more server identifiers625A-N (hereinafter generally referred to as server identifiers625A-N). Each server identifier625may identify, reference, or correspond to a respective server106that is to be accessed by the client102via one of the appliances200. The server identifier625may include, for example, a domain name (e.g., a full qualified domain name (FQDN) in the form of a uniform resource locator (URL)) or a network address (e.g., an Internet Protocol (IP) address or a media access control (MAC) address), among others corresponding to the respective server106.

The configuration profile605may specify, define, or otherwise identify one or more other specifications for the connection between the client102with the servers106identified in the server list620via one of the appliances200identified in the gateway list610. The specifications may define or identify a condition under which the client102is to initiate a failover procedure from the initially connected appliance200to an alternate appliance200. In some embodiments, the configuration profile605may specify or identify a minimum number of servers that are to be reachable from the client102via each of the appliances200identified in the gateway list610. The minimum number may delineate a value for the number of reachable servers106at which to trigger a failover procedure from one appliance200to another. In some embodiments, the configuration profile605may specify or identify a maximum number of servers that are unreachable from the client102. The maximum number may delineate a value for the number of reachable servers106at which to trigger a failover procedure from one appliance200to another. In some embodiments, the configuration profile605may specify or identify a maximum number of attempts to reach the servers106identified in the server list620via each of the appliance200identified in the gateway list610. The number of attempts may specify a value for the number of attempts at which to trigger the failover procedure from one appliance200to another.

From parsing the configuration profile605, the profile handler510may extract or identify the gateway list610. Using the gateway list610, the profile handler510may extract or identify the gateway identifiers615. The profile handler510may further identify the set of appliances200corresponding to the gateway identifiers615of the gateway list610. In addition, the profile handler510may extract or identify the server list620of the configuration profile605. Using the server list620, the profile handler510may extract or identify the server identifies625. The profile handler510may the set of servers106corresponding to the server identifiers625. In some embodiments, the profile handler510may identify the specifications defined by the configuration profile605, such as the minimum number of servers106to be accessed by the client102and the maximum number of attempts after which the client102is to initiate the failover procedure, among others.

Referring now toFIG.6B, depicted is a block diagram of a process630for initiating communications in the system500for selecting gateways. The process630may be performed in connection or subsequent to the process600with the identification of the configuration profile605. Under the process630, the gateway connector515executing on the client102may determine, select, or otherwise identify a primary appliance200A (sometimes referred herein as a primary gateway) to which the client102is to connect with. The gateway505may identify the primary appliance200A using the gateway list610of the configuration profile605. In some embodiments, the gateway connector515may identify the primary appliance200A corresponding to the gateway identifier615A defined as the primary gateway by the configuration profile605. The gateway list610of the configuration profile605may specify that the client102is to connect with the primary appliance200A corresponding to the gateway identifier615A, prior to connection with any of the other available appliances200. In some embodiments, the primary appliance200A may correspond to the appliance200that the client102first connects among the set of appliances200, when the client102lacks the configuration profile605. For example, the primary appliance200A may correspond to the one that the client102is to connect with by default as defined by the connectivity manager505when accessing the network104.

With the identification, the gateway connector515may initiate and establish a connection with the primary appliance200A using the gateway identifier615A identified from the gateway list610. The establishment of the connection with appliance200A may be to set up a secure communications between the client102and the primary appliance200A in accordance with a communications protocol used by the appliances200or the network104. For example, the network104and104′ may be a virtual private network (VPN) or a software defined wide area network (SD-WAN) established over a public network such as the internet. Pursuant to the communications protocol, the gateway connector515may establish a secure tunnel over the network104with the primary appliance200A, such as a VPN tunnel as a part the VPN network or an IP security association (IPsec) tunnel through the SD-WAN. The gateway connector515and the primary appliance200A may exchange one or more messages in accordance with the communications protocol to establish the secure communications. For instance, the messages between the gateway connector515and the server106may be in accordance with a handshake specified by the communications protocol.

Prior to or in conjunction with the connection with the primary appliance200A, the gateway connector515may present or provide a prompt for a user of the client102to enter authentication credentials635to login with the management agent535. The management agent535may handle authentication of the client102for establishing connections with any one of the appliances200. The provision of the prompt may be as part of an authentication procedure with the management agent535to access one or more of the appliances200including the primary appliance200A. In some embodiments, the management agent535may reside on the primary appliance200A, and the functionalities described herein may be performed by the primary appliance200A. In some embodiments, the management agent535may be on a device separate from the appliances200, and may perform the functionalities described herein out-of-band relative to communications between the client102and the appliances200. The authentication credentials635may include, for example, an account identifier corresponding to an identity of the user and a passcode such a set of alphanumeric characters to confirm an identity of the user or a biometric marker corresponding to the user, among others. The user of the client102may enter or input the authentication credentials635using one or more input/output (I/O) devices. Upon entry, the gateway connector515may send, transmit, or otherwise provide the authentication credentials635to the management agent535.

With the receipt, the management agent535may check the authentication credentials635provided by the client102against a record of the credentials for the user accessible to the management agent535. The record of the credentials635may be stored and maintained on a database accessible to the management agent535and the appliances200. If the credentials635do not match, the management agent535may refrain from authentication of the client102for establishing the connection with the appliances200including the primary appliance200A. In some embodiments, the management agent535may determine that the authentication credential provided by the client102is not validated. In some embodiments, the management agent535may send a message indicating a failure of authentication to the client102. Upon receipt of the indication, the gateway connector515may provide the prompt to the user to re-enter the authentication credentials635, and repeat the authentication procedure with the management agent535.

Conversely, if the credentials635match, the management agent535may authenticate the client102to establish the connection with the primary appliance200A. In some embodiments, the management agent535may also validate the authentication credentials635provided by the client102. With the validation of the authentication credentials635, the management agent535may also issue or generate at least one certificate640to authenticate the client102for secure communications with the appliances200including the primary appliance200A. In some embodiments, the certificate640may be generated by a certificate authority separate from the management agent535. The certificate640may identify or include: at least one identity associated with the client102or the user of the client102; at least one cryptographic key (e.g., a public key) to be used to encrypt communications between the client102and the management agent535; at least one digital signature corresponding to an entity (e.g., the management agent535or the certificate authority) issuing the certificate640, among others. Upon generation, the management agent535may also send, transmit, or otherwise provide the certificate640to authenticate the client102.

In some embodiments, the management agent535may retrieve or identify at least a portion of the configuration profile605for the client102using the authentication credentials635, upon validation. In some embodiments, the client102may initially lack one or more portions of the configuration profile605, such as the gateway list610or the server list620, and may be provided the configuration profile605upon validation of the authentication credentials635. The configuration profile605may be maintained and stored on a database accessible to the management agent535. The management agent535may access the database to find, retrieve, or identify the configuration profile605using the authentication credentials635. The configuration profile605retrieved by the management agent535may also include the gateway list610and the server list615. For example, the gateway list610may identify the set of alternate appliance200with which the client102is permitted to connect in accessing the servers106identified in the server list615. With the identification, the management agent535may send, transmit, or otherwise provide the configuration profile605in conjunction with the certificate640to the client102.

The gateway connector515may in turn retrieve, identify, or otherwise receive the certificate640from the management agent535. Upon receipt, the gateway connector515may use the certificate640may to establish the connection between the client102and the primary appliance200A. In some embodiments, the gateway connector515may store and maintain the certificate640on the storage530. In some embodiments, the gateway connector515may identify the primary appliance200A from the gateway list610, upon receipt of the certificate640. To establish the connection, the gateway connector515may also provide, send, or otherwise transmit the certificate640to the primary appliance200A.

The primary appliance200A may in turn retrieve, identify, or otherwise receive the certificate640from the client102. The primary appliance200A may verify that the client102is authenticate by checking the certificate640with the management agent535. Upon receipt and verification of the certificate640, the primary appliance200A may complete the establishment of the connection between the primary appliance200A and the client102. The certificate640may be used for communications between the primary appliance200A and the client102. For example, the gateway connector515may use the cryptographic key of the certificate640to encrypt communications to be sent to the primary appliance200A and decrypt communications from the primary appliance200A. In some embodiments, the primary appliance200A may provide the configuration profile605for the client102. In turn, the gateway connector515may retrieve, identify, or receive the configuration profile605identified and provided by the primary appliance200A. Upon receipt, the gateway connector515may store and maintain the configuration profile605on the storage630. With the establishment of the connection, the client102may attempt to or may be able to access one or more the servers106identified by the server list620of the configuration profile605through the primary appliance200A.

Referring now toFIG.6C, depicted is a block diagram of a process660for checking reachability in the system500for selecting gateways. The process660may be performed subsequent to successful establishment of the connection between the client102and the primary appliance200A. Under the process660, the resource monitor520executing on the client102may carry out or perform a reachability check on each server106identified in the server list620of the configuration profile605. In performing, the resource monitor520may identify the set of servers106that the client102is to be able to reach via the connection with the primary appliance200A. From the configuration profile605, the resource monitor520may find or identify the set of servers106corresponding to the set of server identifiers625specified in the server list620.

With the identification, the resource monitor520may identify, determine, or otherwise detect whether each server106is accessible or reachable from the client102via the connection with the primary appliance200A. The connection between the client102and the primary appliance200A may rely on or use the certificate640as discussed above. To detect, in some embodiments, the resource monitor520may send, provide, or otherwise transmit at least one message665. The message665may be to check the reachability of at least one of the identified server106from the client102via the connection with the primary appliance200A. The message665may identify one or more of the servers106specified by the server list620of the configuration profile605. The primary appliance200A may in turn retrieve, identify, or receive the message665from the client102via the network104and may forward the message665to the identified servers106as message665′ via the network104′.

Upon transmission, the resource monitor520may wait or monitor for responses670A-N (hereinafter generally referred to as responses670) to the message665′ from each identified server106. The waiting for the response670may be for a set time window (e.g., ranging from a few seconds to minutes) relative to the transmission of the message665. Each response670may identify or indicate acknowledgment of receipt of the message665′ by the corresponding server106, and may identify the server106that generated and sent the response670. In response to receipt of the message665′, the server106may send, return, or transmit the response670to the primary appliance200A. The primary appliance200A in turn may send or forward the response670from each server106to the client102.

Using the receipt of the responses670, the resource monitor520may determine whether the corresponding server106is accessible from the client102via the connection with the primary appliance200A. The receipt of the response670may correlate with or indicate the reachability of the server106(e.g., servers106A,106B, and106N as depicted) from the client102via the connection with the primary appliance200A. When the response670is received from the server106within the time window, the resource monitor520may identify or determine that the corresponding server106is reachable from the client102. In some embodiments, the resource monitor520may maintain a counter for the number of servers106reachable from the client102via the connection. Upon receipt of the response670, the resource monitor520may increment the number of servers106kept track by the counter.

In contrast, when the response670is not received from the server106within the time window, the resource monitor520may identify or determine that the corresponding server106is unreachable from the client102via the connection with the primary appliance200A. The lack of any response670from the server106(e.g., the server106C as depicted) may correlate with or indicate the lack of acknowledgement of the receipt of the message665′. In some embodiments, the resource monitor520may maintain a counter for the number of servers106unreachable from the client102. Upon determining that the server106is unreachable, the resource monitor520may increment the counter. In addition, the resource monitor520may repeat the transmission of the message665to the server106identified as unreachable, and wait for the response670from the server106. In some embodiments, the resource monitor520may maintain a counter for the number of attempts to wait for the response670from the corresponding server106or across the servers106identified in the server list620. Each time the message665is transmitted, the resource monitor520may increment the number of attempts kept track by the counter.

In some embodiments, the resource monitor520may at least partially share the resource monitoring process with the primary appliance200A. To that end, the resource monitor520may send, transmit, or provide the set of server identifiers625corresponding to the set of servers106to be accessible from the client102to the primary appliance200A. The primary appliance200A may retrieve, identify, or receive the server identifiers625from the client102. In some embodiments, the primary appliance200A may initiate and establish a connection with each server106identified in the set of server identifiers625over the network104′. If the establishment of the connection is successful, the primary appliance200A may determine that the server106is reachable from the client102. The primary appliance200A may send an indication that the corresponding server106is reachable to the client102. The resource monitor520may in turn retrieve, identify, or receive the indication from the primary appliance200A, and may determine that the identified server106is reachable. Otherwise, if the establishment of the connection is unsuccessful, the primary appliance200A may determine that the server106is unreachable from the client102. The primary appliance200A may send an indication that the corresponding server106is unreachable to the client102. The resource monitor520may in turn retrieve, identify, or receive the indication from the primary appliance200A, and may determine that the identified server106is unreachable.

In some embodiments, the primary appliance200A may send, provide, or otherwise transmit the at least one message665′ to each identified server106. The message665′ may be to check the reachability of a corresponding server106identified in the set of server identifiers625. Upon transmission, the primary appliance200A may wait or monitor for responses670to the message665′ from each identified server106within a set time period, and may perform the operations of the resource monitor520as discussed above. Similar to the resource monitor520, the primary appliance200A may use the receipt of responses570to determine whether the corresponding server106is accessible from the client102via the connection with the primary appliance200A.

When the response670is received from the server106within the time window, the primary appliance200A determine that the corresponding server106is reachable from the client102. In some embodiments, the primary appliance200A may transmit, provide, or otherwise send an indication that the corresponding server106is reachable to the client102. The resource monitor520may in turn retrieve, identify, or receive the indication from the primary appliance200A, and may determine that the identified server106is reachable. Conversely, when the response670is not received from the server106within the time window, the primary appliance200A may identify or determine that the corresponding server106is unreachable from the client102. In some embodiments, the primary appliance200A may transmit, provide, or otherwise send an indication that the corresponding server106is unreachable to the client102. The resource monitor520may in turn retrieve, identify, or receive the indication from the primary appliance200A, and may determine that the identified server106is unreachable. In some embodiments, the resource monitor520may provide the server identifier625corresponding to the server106identified as unreachable to the primary appliance200A, and repeat the process of checking the reachability of the server106.

In some embodiments, the primary appliance200A may also maintain a counter for the number of reachable servers, a counter for the number of unreachable servers, and a counter for number of attempts as discussed above. With the determinations, the primary appliance200A may send, transmit, or provide the number of unreachable servers, the number of reachable servers, or the number of attempts, or any combination thereof, to the client102. The resource monitor520may retrieve, identify, or receive the number of unreachable servers, the number of reachable servers, or the number of attempts, transmitted by the primary appliance200A.

Referring now toFIG.6D, depicted is a block diagram of a process680for switching over in the system500for selecting gateways. The process680may be performed upon detection of reachability issues at one or more of the servers106identified in the server list620of the configuration profile605. Under the process680, the failover handler525executing on the client102may determine whether to perform a switch over685from the primary appliance200A from an alternate appliance200(e.g., the appliance200B). The determination of whether to perform the switch over685may be based on the detection that the identified servers106are unreachable from the client102via the connection with the primary appliance200A. When all the servers106identified in the server list620are determined to be reachable from the client102via the connection, the failover handler525may determine to not perform the switch over685. The client102may continue to access the servers106via the connection with the appliance200A.

Conversely, when at least one server106identified in the server list620is determined to be unreachable from the client102, the failover handler525may determine to perform the switch over685. In some embodiments, the failover handler525may continue the determination as to whether to perform the switch over685based on the conditions specified by the configuration profile605. The conditions may include, for example, the minimum number of reachable servers, maximum number of unreachable server, and maximum number of attempts, among others. When the number of reachable servers is greater than or equal to the minimum number, the failover handler525may determine to not perform the switch over685, and may invoke the resource monitor520to continue with the reachability check process. In contrast, when the number of reachable servers is less than the minimum number, the failover handler525may determine to perform the switch over685.

Continuing on, when the number of unreachable servers is greater than or equal to the maximum number, the failover handler525may determine to perform the switch over685. On the other hand, when the number of unreachable servers is less than the maximum number, the failover handler525may determine to not perform the switch over685, and may invoke the resource monitor520to continue with the reachability check process. In addition, when the number of attempts is less than the maximum number specified by the configuration profile605, the failover handler525may determine to not perform the switch over685. The failover handler525may also invoke the resource monitor520to continue with the reachability check process. In contrast, when the number of attempts is greater than or equal to the maximum number, the failover handler525may determine to perform the switch over685.

When the switch over685is determined to be performed, the failover handler525may identify or select an alternate appliance200B from the set of appliances200in accordance with the gateway list610of the configuration profile605. The failover handler525may identify the alternate appliance200B corresponding to the gateway identifier615B as defined in the gateway list610. In some embodiments, the failover handler525may select the alternate appliance200B as specified in the sequence of gateways in the gateway list610of the configuration list610. For example, the failover handler525may select the third appliance200A corresponding to the third gateway identifier615C, after detecting the servers106are unreachable from the second appliance200B referenced by the second gateway identifier615B.

In some embodiments, the failover handler525may determine whether there are more alternate appliances200B available for selection as identified in the gateway list610of the configuration profile605, when the switch over685is determined to be performed. The failover handler525may identify all the appliances200to which the client102connected in attempting to access the server106. When there are additional appliances200available for selection, the failover handler525may identify the appliance200previously used by the client102, and select the appliance200next identified in the sequence as defined by the gateway list610. Otherwise, when there are no more appliances200available for selection, the failover handler525may determine that the servers106are unreachable from the client102via any of the appliances200. In some embodiments, the failover handler525may provide an indication of the determination that the servers106are unreachable. The indication may be presented via a prompt to the user of the client102. The indication may also be provided to the network administrator.

In some embodiments, the failover handler525may select the alternate appliance200B from the set of appliances200available for selection as identified in the gateway list610based on a network load at each of the appliances200. The set of appliances200available for selection may correspond to the set of gateway identifiers615of the gateway list610. The failover handler525may measure, determine, or identify the network load at each appliance200in the set. The network load may include, for example, an amount of network traffic inbound to the appliance200, network traffic outbound from the appliance200, an amount of data to be processed at the appliance200, among others. With the measurements, the failover handler525may identify the appliance200with the lowest network load. The appliance200may be different from the primary appliance200A (or the previously used appliance200). The failover handler525may select the appliance200having the lowest network load as the alternate appliance200B.

With the selection of the alternate gateway200B, the gateway connector515may carry out, execute, or otherwise perform the switch over685from the primary appliance200A (or previously used appliance200) to the alternate appliance200B. The gateway connector515may terminate the connection between the client102and the primary appliance200A. The gateway connector515may initiate and establish a new connection with the selected alternate appliance200B. The establishment of the new connection may be in accordance with a communications protocol used by the appliances200or the network104, as described above in conjunction with process660. In establishing the connection with the alternate appliance200B, the gateway connector515may use the certificate640used to authenticate the client102with the primary appliance200A. As discussed above, the certificate640may be received from the management agent535. In some embodiments, the gateway connector515may reuse the certificate640without providing a prompt for the user of the client102to enter or input the authentication credentials635. In some embodiments, the gateway connector515may present or provide a prompt for the user of the client102to enter authentication credentials635to login with the alternate appliance200. The processing of the authentication credentials635may be performed as discussed above. Upon establishment of the connection with the alternate gateway200B, the client102access one or more the servers106identified by the server list620of the configuration profile605via the alternate appliance200B. The connectivity manager505may also repeat the processes630and660as discussed above.

In this manner, the configuration profile605may be used by the connectivity manager505running on the client102to check the reachability of the designated servers106to be accessed via one of the appliances200available to the selection. By having the client102perform the check for resource reachability, the complexity associated with probing each and every server106from the appliance200may be reduced. In addition, the re-use of the certificate640from one appliance200to another appliance200may reduce or eliminate the experience of the user at the client102in accessing the resources hosted on the servers106. The avoidance of repeated entry of the authentication credentials635may thus improve the quality of the human-computer interactions (HCIs) between the user at the client102and the overall system500.

Referring now toFIG.7, depicted is a function band diagram of a method700of selecting gateways for reconnection upon detection of reachability issues on backend resources. The functionalities of method800may be implemented using, or performed by, the components described inFIGS.1-6C, such as the client102. Under the method700, a client (e.g., the client102) may connect with at least one gateway (e.g., the appliance200A) (705). The gateway may return a connection success to the client (710). Upon successful connection, the client may initiate a resource monitoring loop (715). In performing the loop, the client may send a message to check reachability of a resource to a server (e.g., the server106) (720). If the server is reachable through the gateway, the server may return a reachability response to the client via the appliance (725). Otherwise, if no response is returned, the client may determine that the server is not reachable (730). The client may further identify the next alternate gateway as identified in a configuration profile (e.g., the configuration profile605) (735). The client may select the next gateway to connect (740), and repeat the functionalities (700)—(730).

Referring now toFIG.8, depicted is a flow diagram for a method600of selecting gateways for reconnection upon detection of reachability issues on backend resources. The functionalities of method800may be implemented using, or performed by, the components described inFIGS.1-6C, such as the client102. In brief overview, a client may identify a configuration profile (805). The client may connect with a gateway (810). The client may determine whether a backend service is reachable (815). If the backend service is reachable, the client may continue with the gateway connection (820). Conversely, if the backend service is unreachable, the client may determine whether there are additional alternate gateways (825). When there are no more alternate gateways, the client may provide an indication of unreachability (830). Otherwise, when there are additional alternate gateways, the client may identify the next gateway (835). The client may re-use an authentication certificate (840).

In further detail, a client (e.g., the client102) may identify a configuration profile (e.g., the configuration profile605) (805). The client may identify a set of backend services (e.g., the servers106) to be accessed by the client and a set of gateways (e.g., the appliances200) available for selection to access the servers. The client may identify a first gateway as defined by the configuration profile to connect with.

The client may connect with a gateway (e.g., the primary appliance200A or another appliance200) (810). In establishing a connection, the client may prompt a user of the client to enter authentication credentials (e.g., the authentication credentials635). Upon validation of the credentials, the gateway may issue a certificate (e.g., the certificate640) to the client. The client may use the certificate in secure communications with the gateway.

The client may determine whether a backend service (e.g., the server106) is reachable (815). The client may send a message (e.g., the message365) to check reachability of the backend service toward the gateway. The gateway in turn may forward the message to the backend service. If the message reaches the backend service, the backend service may return a response to the gateway, and the gateway in turn may forward the response to the client. When the response is received, the client may determine that the backend service is reachable. Otherwise, when response is not received in a time window, the client may determine that the backend service is unreachable.

If the backend service is reachable, the client may continue with the gateway connection (820). The client may continue accessing the backend service through the gateway. Conversely, if the backend service is unreachable, the client may determine whether there are additional alternate gateways (e.g., the alternate appliance200B) (825). The client may identify the alternate gateway from the configuration profile.

When there are no more alternate gateways, the client may provide an indication of unreachability (830). The client may present a prompt that the backend service is unreachable. Otherwise, when there are additional alternate gateways, the client may identify the next gateway (835). The client may select the alternate gateway as defined in the configuration profile, and initiate a connection with the selected gateway. The client may re-use the authentication certificate (e.g., the certificate640) (840). In establishing the connection, the client may reuse the certificate used with the previously connected gateway.

Various elements, which are described herein in the context of one or more embodiments, may be provided separately or in any suitable subcombination. For example, the processes described herein may be implemented in hardware, software, or a combination thereof. Further, the processes described herein are not limited to the specific embodiments described. For example, the processes described herein are not limited to the specific processing order described herein and, rather, process blocks may be re-ordered, combined, removed, or performed in parallel or in serial, as necessary, to achieve the results set forth herein.

It should be understood that the systems described above may provide multiple ones of any or each of those components and these components may be provided on either a standalone machine or, in some embodiments, on multiple machines in a distributed system. The systems and methods described above may be implemented as a method, apparatus or article of manufacture using programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. In addition, the systems and methods described above may be provided as one or more computer-readable programs embodied on or in one or more articles of manufacture. The term “article of manufacture” as used herein is intended to encompass code or logic accessible from and embedded in one or more computer-readable devices, firmware, programmable logic, memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, SRAMs, etc.), hardware (e.g., integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.), electronic devices, a computer readable non-volatile storage unit (e.g., CD-ROM, USB Flash memory, hard disk drive, etc.). The article of manufacture may be accessible from a file server providing access to the computer-readable programs via a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. The article of manufacture may be a flash memory card or a magnetic tape. The article of manufacture includes hardware logic as well as software or programmable code embedded in a computer readable medium that is executed by a processor. In general, the computer-readable programs may be implemented in any programming language, such as LISP, PERL, C, C++, C#, PROLOG, or in any byte code language such as JAVA. The software programs may be stored on or in one or more articles of manufacture as object code.

While various embodiments of the methods and systems have been described, these embodiments are illustrative and in no way limit the scope of the described methods or systems. Those having skill in the relevant art can effect changes to form and details of the described methods and systems without departing from the broadest scope of the described methods and systems. Thus, the scope of the methods and systems described herein should not be limited by any of the illustrative embodiments and should be defined in accordance with the accompanying claims and their equivalents.

It will be further understood that various changes in the details, materials, and arrangements of the parts that have been described and illustrated herein may be made by those skilled in the art without departing from the scope of the following claims.