Patent Publication Number: US-2022224684-A1

Title: Validating session tokens using network properties

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to and the benefit of International Patent Application No. PCT/GR2021/000002, titled “VALIDATING SESSION TOKENS USING NETWORK PROPERTIES,” and filed on Jan. 8, 2021, the contents of all of which are hereby incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     The present application generally relates to network sessions. In particular, the present application relates to systems and methods of validating session tokens using network properties. 
     BACKGROUND 
     A device may establish a session with another device for communications over a network. Depending on the level of security, the session may be vulnerable to external entities intending to obtain the data communicated over the session. 
     BRIEF SUMMARY 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features, nor is it intended to limit the scope of the claims included herewith. 
     Cryptographic protocols may be used to protect communications among devices in network. Many of these cryptographic protocols (e.g., Internet Key Exchange (IKE) and Transport Layer Security (TLS)) may provide very strong identity protection that guarantee entities that are in communication with one another are what they purport to be. These protocols, however, may have very little protections to guarantee where the entity is and may be unable to provide assurances for multipath environments. For certain applications (e.g., financial transactions), it may be imperative that the network not only be secured with a trusted identity, but also that the network be accessed from trusted locations. This may be particularly the case in a multi-path environment where some connections have no inherent security or providing security that is prohibitively expensive. 
     In addition, sessions and tunnels for communications may be quickly re-established using tokens without user intervention in accordance with various protocols, such as the Multipath-TCP (RFC6824) under which a network identifier may be used to associate multiple paths to a single connection. While such protocols may provide for assurances in multiple paths, these communication protocols by themselves may be unable to provide protections as to where the connecting entity is. 
     To address these and other technical challenges, the secured token may be leveraged in a multipath network environment to allow known, secured paths to automatically permit other unknown paths to establish connections and forward network traffic. For a session or tunnel between two endpoints in a multipath environment, specific paths between the endpoints may be marked as critical or trusted. In such an environment, each path may be secured with a different session or tunnel, such as IKE or TLS. These paths may be selected when the configuration of the network in which the path traverses provides assurances for the location of the device. Examples of such configurations may include: an  1 VIPLS network specifying physical access to enter the network; a node configured with a static address in a network with static routing such that traffic from a spoofed IP cannot be returned to an attacker; and a node configured with a static address in a network with reverse path filtering such that traffic from a spoofed IP cannot be returned to an attacker. While these examples are not perfectly inviolable, the network level protection provided may be sufficient to provide assurances for many applications. 
     During session initialization, each endpoint may generate a session token (e.g., using a cryptographic algorithm) to uniquely identify the multipath session. The session may be kept in volatile memory and may not be exposed outside of encrypted channels. In conjunction with the encrypted phase of the session negotiation, a vendor specific payload may be sent containing the multipath session token. To ensure the safety of the token, the vendor specific payload may be also be secured with the identity protection mechanism, such as public key infrastructure (PKI) signing. 
     When a session is successfully negotiated and a token has been received, a determination as to whether the path is to be trusted may be performed. If the path is considered trusted, the token may be marked as trusted. On the other hand, if the path is not trusted, a previously known token marked as trusted may be found. If the previous token was validated and other paths with the token are still active, the new session may be rejected or terminated. If no token has been trusted or no other session exists for other paths, no action may be taken. All endpoints may refuse to forward traffic on or process forwarded traffic from a path whose token is not trusted. 
     Aspects of the present disclosure are directed to systems, methods, and non-transitory computer-readable media for validating session tokens using network properties. A first device having one or more processors coupled with memory may identify a session token from an initiation of a session between the first device and a second device via a network path of a plurality of network paths. The first device may determine that the first network path is to be trusted based at least on a property of the network path. The first device may validate the session token for use over the plurality of network paths, responsive to determining that the network path is to be trusted. The first device may provide, responsive to validating, the session token to the second device for use in communications over the plurality of network paths. 
     In some embodiments, the first device may determine that a second network path of the plurality of network paths is not to be trusted based at least on a property of the second network path. In some embodiments, the first device may restrict a second session token of a second session for use over the plurality of network paths, responsive to determining that the second network path is not to be trusted. 
     In some embodiments, the first device may identify, responsive to determining that a second network path of the plurality of network paths is not to be trusted, the session token validated for use over the plurality of network paths. In some embodiments, the first device may restrict a second session token of the second network path for use over the plurality of network paths, responsive to identifying the session token. 
     In some embodiments, the first device may determine, responsive to determining that a second network path of the plurality of network paths is not to be trusted, that the plurality of network paths for which the session token is validated is inactive. In some embodiments, the first device may restrict, responsive to determining that the plurality of network paths is inactive, a second session over the second network path for communications between the first device and the second device. 
     In some embodiments, the first device may identify, subsequent to validating the session token, the session token from an initiation of a second session between the first device and the second device via a second network path of the plurality of network paths. In some embodiments, the first device may re-validate, without determination of whether the second network path is to be trusted, the session token for use in communications over the second network path 
     In some embodiments, the first device may validate a second session token identified from an initiation of a second session between the first device and a third device via a second network path based at least on a property of the second network path. In some embodiments, the first device may provide, responsive to validating the second session token, the second session token to the first device and the third device for use in communications over a third network path between the second device and the third device. 
     In some embodiments, the first device may determine that a second network path between the first device and a third device is not to be trusted based at least on a property of the second network path. In some embodiments, the first device may restrict, responsive to determining that the second network path is not to be trusted, a second session token associated with a second session over the second network path from use in communications over a third network path between the second device and the third device. 
     In some embodiments, the first device may cause, responsive to determining that a second network path between the first device and a third device is not to be trusted based on a property of the second network path, the third device to provide a second session token via a third network path between the second device and the third device. In some embodiments, the first device may provide, responsive to determining that the third network path is to be trusted based at least on a property of the third network path, the second session token over the third network path to the third device for use in communications over the second network path and the third network path. 
     In some embodiments, the first device may identify a network type of the network path as one of a plurality of trusted network types. In some embodiments, the first device may determine that the second device is configured with a static address in the network path with at least one of a static routing or a reverse path filtering. In some embodiments, the first device may provide the session token to the second device to cause the second device to store the session token to use in communications over the plurality of network paths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Objects, aspects, features, and advantages of embodiments disclosed herein will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawing figures in which like reference numerals identify similar or identical elements. Reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features, and not every element may be labeled in every figure. The drawing figures are not necessarily to scale, emphasis instead being placed upon illustrating embodiments, principles and concepts. The drawings are not intended to limit the scope of the claims included herewith. 
         FIG. 1A  is a block diagram of a network computing system, in accordance with an illustrative embodiment; 
         FIG. 1B  is a block diagram of a network computing system for delivering a computing environment from a server to a client via an appliance, in accordance with an illustrative embodiment; 
         FIG. 1C  is a block diagram of a computing device, in accordance with an illustrative embodiment; 
         FIG. 2  is a block diagram of an appliance for processing communications between a client and a server, in accordance with an illustrative embodiment; 
         FIG. 3  is a block diagram of a virtualization environment, in accordance with an illustrative embodiment; 
         FIG. 4  is a block diagram of a cluster system, in accordance with an illustrative embodiment; 
         FIGS. 5A-D  are block diagrams of an embodiment of a system for validating session tokens using network properties in accordance with an illustrative embodiment; 
         FIG. 6  is a communication diagram of an embodiment of a process for validating session tokens using network properties in accordance with an illustrative embodiment; and 
         FIG. 7  is a flow diagram of an embodiment of a method for validating session tokens using network properties in accordance with an illustrative embodiment. 
     
    
    
     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; and 
     Section E describes embodiments of systems and methods for validating session tokens using network properties. 
     A. Network and Computing Environment 
     Referring to  FIG. 1A , an illustrative network environment  100  is depicted. Network environment  100  may include one or more clients  102 ( 1 )- 102 ( n ) (also generally referred to as local machine(s)  102  or client(s)  102 ) in communication with one or more servers  106 ( 1 )- 106 ( n ) (also generally referred to as remote machine(s)  106  or server(s)  106 ) via one or more networks  104 ( 1 )- 104   n  (generally referred to as network(s)  104 ). In some embodiments, a client  102  may communicate with a server  106  via one or more appliances  200 ( 1 )- 200   n  (generally referred to as appliance(s)  200  or gateway(s)  200 ). 
     Although the embodiment shown in  FIG. 1A  shows one or more networks  104  between clients  102  and servers  106 , in other embodiments, clients  102  and servers  106  may be on the same network  104 . The various networks  104  may be the same type of network or different types of networks. For example, in some embodiments, network  104 ( 1 ) may be a private network such as a local area network (LAN) or a company Intranet, while network  104 ( 2 ) and/or network  104 ( n ) may be a public network, such as a wide area network (WAN) or the Internet. In other embodiments, both network  104 ( 1 ) and network  104 ( n ) may be private networks. Networks  104  may 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 in  FIG. 1A , one or more appliances  200  may be located at various points or in various communication paths of network environment  100 . For example, appliance  200  may be deployed between two networks  104 ( 1 ) and  104 ( 2 ), and appliances  200  may communicate with one another to work in conjunction to, for example, accelerate network traffic between clients  102  and servers  106 . In other embodiments, the appliance  200  may be located on a network  104 . For example, appliance  200  may be implemented as part of one of clients  102  and/or servers  106 . In an embodiment, appliance  200  may be implemented as a network device such as NetScaler® products sold by Citrix Systems, Inc. of Fort Lauderdale, Fla. 
     As shown in  FIG. 1A , one or more servers  106  may operate as a server farm  38 . Servers  106  of server farm  38  may be logically grouped, and may either be geographically co-located (e.g., on premises) or geographically dispersed (e.g., cloud based) from clients  102  and/or other servers  106 . In an embodiment, server farm  38  executes one or more applications on behalf of one or more of clients  102  (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. Clients  102  may seek access to hosted applications on servers  106 . 
     As shown in  FIG. 1A , in some embodiments, appliances  200  may include, be replaced by, or be in communication with, one or more additional appliances, such as WAN optimization appliances  205 ( 1 )- 205 ( n ), referred to generally as WAN optimization appliance(s)  205 . For example, WAN optimization appliance  205  may 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, appliance  205  may be a performance enhancing proxy or a WAN optimization controller. In one embodiment, appliance  205  may be implemented as CloudBridge® products sold by Citrix Systems, Inc. of Fort Lauderdale, Fla. 
     Referring to  FIG. 1B , an example network environment  100 ′ for delivering and/or operating a computing network environment on a client  102  is shown. As shown in  FIG. 1B , a server  106  may include an application delivery system  190  for delivering a computing environment, application, and/or data files to one or more clients  102 . Client  102  may include client agent  120  and computing environment  15 . Computing environment  15  may execute or operate an application,  16 , that accesses, processes or uses a data file  17 . Computing environment  15 , application  16  and/or data file  17  may be delivered to the client  102  via appliance  200  and/or the server  106 . 
     Appliance  200  may accelerate delivery of all or a portion of computing environment  15  to a client  102 , for example by the application delivery system  190 . For example, appliance  200  may 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 client  102  and a server  106 . 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. Appliance  200  may also provide load balancing of servers  106  to process requests from clients  102 , act as a proxy or access server to provide access to the one or more servers  106 , provide security and/or act as a firewall between a client  102  and a server  106 , 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 client  102  to a server  106 , such as a secure socket layer (SSL) VPN connection and/or provide encryption and decryption operations. 
     Application delivery management system  190  may deliver computing environment  15  to a user (e.g., client  102 ), remote or otherwise, based on authentication and authorization policies applied by policy engine  195 . A remote user may obtain a computing environment and access to server stored applications and data files from any network-connected device (e.g., client  102 ). For example, appliance  200  may request an application and data file from server  106 . In response to the request, application delivery system  190  and/or server  106  may deliver the application and data file to client  102 , for example via an application stream to operate in computing environment  15  on client  102 , or via a remote-display protocol or otherwise via remote-based or server-based computing. In an embodiment, application delivery system  190  may be implemented as any portion of the Citrix Workspace Suite™ by Citrix Systems, Inc., such as XenApp® or XenDesktop®. 
     Policy engine  195  may control and manage the access to, and execution and delivery of, applications. For example, policy engine  195  may determine the one or more applications a user or client  102  may access and/or how the application should be delivered to the user or client  102 , such as a server-based computing, streaming or delivering the application locally to the client  50  for local execution. 
     For example, in operation, a client  102  may request execution of an application (e.g., application  16 ′) and application delivery system  190  of server  106  determines how to execute application  16 ′, for example based upon credentials received from client  102  and a user policy applied by policy engine  195  associated with the credentials. For example, application delivery system  190  may enable client  102  to receive application-output data generated by execution of the application on a server  106 , may enable client  102  to execute the application locally after receiving the application from server  106 , or may stream the application via network  104  to client  102 . For example, in some embodiments, the application may be a server-based or a remote-based application executed on server  106  on behalf of client  102 . Server  106  may display output to client  102  using a thin-client or remote-display protocol, such as the Independent Computing Architecture (ICA) protocol by Citrix Systems, Inc. of Fort Lauderdale, Fla. 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 servers  106  may include a performance monitoring service or agent  197 . In some embodiments, a dedicated one or more servers  106  may 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 clients  102  (e.g., client agent  120 ), servers  106  (e.g., agent  197 ) or an appliances  200  and/or  205  (agent not shown). In general, monitoring agents (e.g.,  120  and/or  197 ) execute transparently (e.g., in the background) to any application and/or user of the device. In some embodiments, monitoring agent  197  includes any of the product embodiments referred to as EdgeSight by Citrix Systems, Inc. of Fort Lauderdale, Fla. 
     The monitoring agents  120  and  197  may 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 environment  100 . The monitoring agents may monitor resource consumption and/or performance of hardware, software, and/or communications resources of clients  102 , networks  104 , appliances  200  and/or  205 , and/or servers  106 . 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 agents  120  and  197  may provide application performance management for application delivery system  190 . For example, based upon one or more monitored performance conditions or metrics, application delivery system  190  may be dynamically adjusted, for example periodically or in real-time, to optimize application delivery by servers  106  to clients  102  based upon network environment performance and conditions. 
     In described embodiments, clients  102 , servers  106 , and appliances  200  and  205  may 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, clients  102 , servers  106  and/or appliances  200  and  205  may each correspond to one computer, a plurality of computers, or a network of distributed computers such as computer  101  shown in  FIG. 1C . 
     As shown in  FIG. 1C , computer  101  may include one or more processors  103 , volatile memory  122  (e.g., RAM), non-volatile memory  128  (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 interfaces  118 , and communication bus  150 . User interface  123  may include graphical user interface (GUI)  124  (e.g., a touchscreen, a display, etc.) and one or more input/output (I/O) devices  126  (e.g., a mouse, a keyboard, etc.). Non-volatile memory  128  stores operating system  115 , one or more applications  116 , and data  117  such that, for example, computer instructions of operating system  115  and/or applications  116  are executed by processor(s)  103  out of volatile memory  122 . Data may be entered using an input device of GUI  124  or received from I/O device(s)  126 . Various elements of computer  101  may communicate via communication bus  150 . Computer  101  as shown in  FIG. 1C  is shown merely as an example, as clients  102 , servers  106  and/or appliances  200  and  205  may 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)  103  may 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 interfaces  118  may include one or more interfaces to enable computer  101  to 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 device  101  may execute an application on behalf of a user of a client computing device (e.g., a client  102 ), 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 client  102 ), 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. 2  shows an example embodiment of appliance  200 . As described herein, appliance  200  may be implemented as a server, gateway, router, switch, bridge or other type of computing or network device. As shown in  FIG. 2 , an embodiment of appliance  200  may include a hardware layer  206  and a software layer  205  divided into a user space  202  and a kernel space  204 . Hardware layer  206  provides the hardware elements upon which programs and services within kernel space  204  and user space  202  are executed and allow programs and services within kernel space  204  and user space  202  to communicate data both internally and externally with respect to appliance  200 . As shown in  FIG. 2 , hardware layer  206  may include one or more processing units  262  for executing software programs and services, memory  264  for storing software and data, network ports  266  for transmitting and receiving data over a network, and encryption processor  260  for 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 appliance  200  allocates, manages, or otherwise segregates the available system memory into kernel space  204  and user space  202 . Kernel space  204  is reserved for running kernel  230 , including any device drivers, kernel extensions or other kernel related software. As known to those skilled in the art, kernel  230  is the core of the operating system, and provides access, control, and management of resources and hardware-related elements of application. Kernel space  204  may also include a number of network services or processes working in conjunction with cache manager  232 . 
     Appliance  200  may include one or more network stacks  267 , such as a TCP/IP based stack, for communicating with client(s)  102 , server(s)  106 , network(s)  104 , and/or other appliances  200  or  205 . For example, appliance  200  may establish and/or terminate one or more transport layer connections between clients  102  and servers  106 . Each network stack  267  may include a buffer for queuing one or more network packets for transmission by appliance  200 . 
     Kernel space  204  may include cache manager  232 , packet engine  240 , encryption engine  234 , policy engine  236  and compression engine  238 . In other words, one or more of processes  232 ,  240 ,  234 ,  236  and  238  run in the core address space of the operating system of appliance  200 , 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 manager  232  may 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 manager  232  may be a data object in memory  264  of appliance  200 , or may be a physical memory having a faster access time than memory  264 . 
     Policy engine  236  may 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 appliance  200 , and define or configure security, network traffic, network access, compression or other functions performed by appliance  200 . 
     Encryption engine  234  may process any security related protocol, such as SSL or TLS. For example, encryption engine  234  may encrypt and decrypt network packets, or any portion thereof, communicated via appliance  200 , may setup or establish SSL, TLS or other secure connections, for example between client  102 , server  106 , and/or other appliances  200  or  205 . In some embodiments, encryption engine  234  may use a tunneling protocol to provide a VPN between a client  102  and a server  106 . In some embodiments, encryption engine  234  is in communication with encryption processor  260 . Compression engine  238  compresses network packets bi-directionally between clients  102  and servers  106  and/or between one or more appliances  200 . 
     Packet engine  240  may manage kernel-level processing of packets received and transmitted by appliance  200  via network stacks  267  to send and receive network packets via network ports  266 . Packet engine  240  may operate in conjunction with encryption engine  234 , cache manager  232 , policy engine  236  and compression engine  238 , 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 space  202  is 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 space  204  directly and uses service calls in order to access kernel services. User space  202  may include graphical user interface (GUI)  210 , a command line interface (CLI)  212 , shell services  214 , health monitor  216 , and daemon services  218 . GUI  210  and CLI  212  enable a system administrator or other user to interact with and control the operation of appliance  200 , such as via the operating system of appliance  200 . Shell services  214  include programs, services, tasks, processes or executable instructions to support interaction with appliance  200  by a user via the GUI  210  and/or CLI  212 . 
     Health monitor  216  monitors, 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 appliance  200 . In some embodiments, health monitor  216  intercepts and inspects any network traffic passed via appliance  200 . For example, health monitor  216  may interface with one or more of encryption engine  234 , cache manager  232 , policy engine  236 , compression engine  238 , packet engine  240 , daemon services  218 , and shell services  214  to determine a state, status, operating condition, or health of any portion of the appliance  200 . Further, health monitor  216  may 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 appliance  200 . Additionally, health monitor  216  may measure and monitor the performance of any application, program, process, service, task or thread executing on appliance  200 . 
     Daemon services  218  are programs that run continuously or in the background and handle periodic service requests received by appliance  200 . In some embodiments, a daemon service may forward the requests to other programs or processes, such as another daemon service  218  as appropriate. 
     As described herein, appliance  200  may relieve servers  106  of much of the processing load caused by repeatedly opening and closing transport layers connections to clients  102  by opening one or more transport layer connections with each server  106  and maintaining these connections to allow repeated data accesses by clients via the Internet (e.g., “connection pooling”). To perform connection pooling, appliance  200  may translate or multiplex communications by modifying sequence numbers and acknowledgment numbers at the transport layer protocol level (e.g., “connection multiplexing”). Appliance  200  may also provide switching or load balancing for communications between the client  102  and server  106 . 
     As described herein, each client  102  may include client agent  120  for establishing and exchanging communications with appliance  200  and/or server  106  via a network  104 . Client  102  may have installed and/or execute one or more applications that are in communication with network  104 . Client agent  120  may intercept network communications from a network stack used by the one or more applications. For example, client agent  120  may 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 agent  120 , for example to intercept and redirect a transport layer connection to an IP address and port controlled or managed by client agent  120 . Thus, client agent  120  may 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 agent  120  can 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 agent  120  is implemented as an Independent Computing Architecture (ICA) client developed by Citrix Systems, Inc. of Fort Lauderdale, Fla. Client agent  120  may perform acceleration, streaming, monitoring, and/or other operations. For example, client agent  120  may accelerate streaming an application from a server  106  to a client  102 . Client agent  120  may also perform end-point detection/scanning and collect end-point information about client  102  for appliance  200  and/or server  106 . Appliance  200  and/or server  106  may use the collected information to determine and provide access, authentication and authorization control of the client&#39;s connection to network  104 . For example, client agent  120  may 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 to  FIG. 3 , a block diagram of a virtualized environment  300  is shown. As shown, a computing device  302  in virtualized environment  300  includes a virtualization layer  303 , a hypervisor layer  304 , and a hardware layer  307 . Hypervisor layer  304  includes one or more hypervisors (or virtualization managers)  301  that allocates and manages access to a number of physical resources in hardware layer  307  (e.g., physical processor(s)  321  and physical disk(s)  328 ) by at least one virtual machine (VM) (e.g., one of VMs  306 ) executing in virtualization layer  303 . Each VM  306  may include allocated virtual resources such as virtual processors  332  and/or virtual disks  342 , as well as virtual resources such as virtual memory and virtual network interfaces. In some embodiments, at least one of VMs  306  may include a control operating system (e.g.,  305 ) in communication with hypervisor  301  and used to execute applications for managing and configuring other VMs (e.g., guest operating systems  310 ) on device  302 . 
     In general, hypervisor(s)  301  may provide virtual resources to an operating system of VMs  306  in any manner that simulates the operating system having access to a physical device. Thus, hypervisor(s)  301  may 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)  301  may be implemented as a XEN hypervisor, for example as provided by the open source Xen.org community. In an illustrative embodiment, device  302  executing 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, device  302  may be implemented as a XEN server as provided by Citrix Systems, Inc., of Fort Lauderdale, Fla. 
     Hypervisor  301  may create one or more VMs  306  in which an operating system (e.g., control operating system  305  and/or guest operating system  310 ) executes. For example, the hypervisor  301  loads a virtual machine image to create VMs  306  to execute an operating system. Hypervisor  301  may present VMs  306  with an abstraction of hardware layer  307 , and/or may control how physical capabilities of hardware layer  307  are presented to VMs  306 . For example, hypervisor(s)  301  may manage a pool of resources distributed across multiple physical computing devices. 
     In some embodiments, one of VMs  306  (e.g., the VM executing control operating system  305 ) may manage and configure other of VMs  306 , 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)  301  and/or other VMs via, for example, one or more Application Programming Interfaces (APIs), shared memory, and/or other techniques. 
     In general, VMs  306  may provide a user of device  302  with access to resources within virtualized computing environment  300 , for example, one or more programs, applications, documents, files, desktop and/or computing environments, or other resources. In some embodiments, VMs  306  may 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 in  FIG. 3  as including a single virtualized device  302 , virtualized environment  300  may 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, appliance  200  may be additionally or alternatively implemented in a virtualized environment  300  on any computing device, such as a client  102 , server  106  or appliance  200 . 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 appliance  200 . 
     In some embodiments, a server may execute multiple virtual machines  306 , 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., in  FIGS. 1C, 2 and 3 ), 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 client  102 , server  106  or appliance  200 , 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 in  FIGS. 1A and 1B  as being single appliances, appliances  200  may 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. 4  shows a block diagram of an illustrative computing device cluster or appliance cluster  400 . A plurality of appliances  200  or other computing devices (e.g., nodes) may be joined into a single cluster  400 . Cluster  400  may operate as an application server, network storage server, backup service, or any other type of computing device to perform many of the functions of appliances  200  and/or  205 . 
     In some embodiments, each appliance  200  of cluster  400  may 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 appliances  200  of cluster  400  may 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 appliances  200  of cluster  400  may be geographically distributed, with appliances  200  not 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, cluster  400  may 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 in  FIG. 4 , appliance cluster  400  may be coupled to a client-side network  104 via client data plane  402 , for example to transfer data between clients  102  and appliance cluster  400 . Client data plane  402  may be implemented a switch, hub, router, or other similar network device internal or external to cluster  400  to distribute traffic across the nodes of cluster  400 . 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 cluster  400  may be coupled to a second network  104 ′ via server data plane  404 . Similarly to client data plane  402 , server data plane  404  may be implemented as a switch, hub, router, or other network device that may be internal or external to cluster  400 . In some embodiments, client data plane  402  and server data plane  404  may be merged or combined into a single device. 
     In some embodiments, each appliance  200  of cluster  400  may be connected via an internal communication network or back plane  406 . Back plane  406  may 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 cluster  400 . In some embodiments, back plane  406  may be a physical network, a VPN or tunnel, or a combination thereof. 
     E. Systems and Methods for Validating Session Tokens Using Network Properties 
     Referring now to  FIG. 5A , depicted is a system  500  for validating session tokens using network properties. In overview, the system  500  may include at least one initiator  505  and at least one responder  510 . The initiator  505  and the responder  510  communicatively coupled with one another over one or more networks  515 A-N (hereinafter generally referred to as networks  515 ) via one or more paths  520  (hereinafter generally referred to as paths  520 ). The initiator  505  (also referred herein generally as a device) may include at least one session interface  525 , at least one token handler  530 , and at least one database  535 . The responder  510  may include at least one communication handler  540 , at least one path evaluator  545 , at least one token validator  550 , at least one session controller  555 , and at least one database  560 . 
     The systems and methods of the present solution may be implemented in any type and form of device, including clients  102 , servers  106 , and/or appliances  200 . As referenced herein, a “server” may sometimes refer to any device in a client-server relationship, e.g., an appliance  200  in a handshake with a client device  102 . The clients  102 , servers  106 , and the appliances  200  may execute any functionalities of the initiator  505  or the responder  510 . In some embodiments, the initiator  505  may correspond to the client  102  and the responder  510  may correspond to the server  106  or a server-side appliance  200 . In some embodiments, the initiator  505  may correspond to a client-side appliance  200  and the responder  510  may correspond to the server  106  or the server-side appliance  200 . The present systems and methods may be implemented in any intermediary device or gateway, such as any embodiments of the appliance or devices  200  described 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. 
     In further detail, the one or more networks  515  may communicatively couple the initiator  505  and the responder  510  with each other. The networks  515  may be established (e.g., previously by the initiator  505 , the responder  510 , or another entity) in accordance with any number of routing techniques or security mechanisms. The routing techniques may include, for example, static routing (e.g., a multiprotocol label switching (MPLS), default static route, default static route, summary static route, and the floating static rule) and dynamic or adaptive routing (e.g., Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS), and Interior Gateway Routing Protocol (GRP), and the Internet (INET)), among others. The security mechanisms may include, for example, reverse-path filtering (RPF), ingress filtering, or egress filtering, among others. At least one network  515  (e.g., MPLS) may specify or entail physical access by the participant nodes (e.g., the initiator  505  and the responder  510 ) for entry and access. Conversely, at least one other network  515  (e.g., INET) may not entail physical access by the participant nodes for entry and access. In addition, each network  515  may facilitate or support one or more paths  520  for communications between the initiator  505  and the responder  510 . The communications over the path  520  may be in accordance with established and secured with any number of communications protocols to, such as Internet Key Exchange (IES), Transport Layer Security (TLS), and Transmission Control Protocol (TCP), among others. 
     Referring now to  FIG. 5B , depicted is the system  500  for validating session tokens using network properties focused on one of the paths  520  (e.g., the path  515 A) of one network  515  (e.g., the network  515 A) between the initiator  505  and the responder  510 . The session interface  525  executing on the initiator  505  may start or initiate at least one session  570  with responder  510  over the path  520  via the network  515 . Conversely, the communication handler  540  executing on the responder  510  may manage or facilitate the initiation of the session  570  with the initiator  505  over the path  520  via the network  515 . The session  570  may be used to facilitate or support communications between the initiator  505  and the responder  510  over the path  520  of the network  515 . For example, an application executing on the initiator  505  may initiate the session  570  to access resources for the application hosted or accessible via the responder  510  over the network  515  via the path  520 . 
     To initiate, the session interface  525  executing on the initiator  505  and the communication handler  540  may exchange or communicate a series of messages in accordance with a communication protocol. In some embodiments, the session interface  525  of the initiator  505  and the communication handler  540  of the responder  510  may perform the initiation of the session  570  in accordance with a handshake process of the communication protocol (e.g., TCP handshake process). The session interface  525  may send, provide, or otherwise transmit at least one initiation message  575  over the path  520  of the network  515 . The initiation message  575  may include information (e.g., in the header or metadata) defining the establishment of the session  570  over the path  520  via the network  515  with the responder  510 . The information may include source address (e.g., Internet Protocol (IP) address or media access control (MAC) address) and source port corresponding to the initiator  505 . The information may also include destination address (e.g., IP address or MAC address) and destination port corresponding to the responder  510 . The source and destination addresses may be defined in accordance with the network  515  over which the session  570  is to be established, and the type of network address (e.g., static, dynamic, public, or private IP address) may be identified in the information. For example, when the network  515  uses static routing, the source and destination addresses may be static IP addresses. On the other hand, when the network  515  uses dynamic routing, the source and destination addresses may be dynamic IP addresses. The message from the initiator  505  may identify or include session information, such as network type (including the routing technique) of the network  515  and the encryption protocol to be applied to the communications in the session  570  via the path  520 , among others. 
     In turn, the communication handler  540  may identify, obtain, or otherwise receive the initiation message  575  from the initiator  505 . With receipt of the initiation message  575 , the communication handler  540  may store and maintain the session information from the initiation message  575  for the session  570  on the database  560 . The session information may be stored on the database  560  with a session state that the associated session  570  is active. In addition, the communication handler  540  may generate at least one acknowledgement message  580  in accordance with the handshake process of the communication protocol. The acknowledgment message  580  may indicate the completion of the establishment of the session  570  between the initiator  505  and the responder  510 . The acknowledgment message  580  may include the information identified by the initiation message  575 . For example, the information of the acknowledgement message  580  may include the source address and source port corresponding to the responder  510 , the destination address and port corresponding to the initiator  505 , and the session information (e.g., the network type of the network  515  and the communication protocol), among others. Upon generation, the communication handler  540  may send, provide, or otherwise transmit the acknowledgement message  580  to the initiator  505 . The session interface  525  in turn may receive the acknowledgement message  580  from the responder  510 . The receipt of the acknowledgement message  580  may mark the completion of the establishment of the session  570  between the initiator  505  and the responder  510 . 
     In response to the receipt of the acknowledgment message  580 , the session interface  525  may generate at least one token message  585  to send to the responder  510 . The token message  585  may be generated in accordance with the communications protocol for the network  515  over which the path  520 . The session interface  525  may determine, create, or otherwise generate at least one token  590  to include in the token message  585 . The token  590  may include a set of alphanumeric characters or a numeric value to reference or uniquely identify the session  570  between the initiator  505  and the respond  510  over the path  510  via the network  515 . The token  590  may be a multi-path token and may be applicable to the one or more paths  510  overs one or more networks  515 . The token  590  may be generated by the session interface  525  according to an encryption algorithm, such as a cryptographic key, digital signature, a message authentication code, or a cryptographic hashing function, among others. With the generation, the session interface  525  may add, insert, or include the token  590  in the token message  585 . The token message  585  may also include the information discussed above with respect to the initiation message  575 . The session interface  525  may then send, provide, or otherwise transmit to the responder  510  via the path  520  over the network  515 . 
     In turn, the communication handler  540  may retrieve, identify, or otherwise receive the token message  585  sent by the initiator  505  in conjunction with the initiation of the session  570 . Upon receipt, the communication handler  540  may parse the token message  585  to extract, retrieve, or otherwise identify the token  590  included in the token message  585 . The communication handler  540  may also store and maintain the token  590  identified from the token message  585  onto the database  560 . In some embodiments, the communication handler  540  may store an association of the token  590  with the session  570  or the initiator  505  onto the database  560 . If there were other sessions established between the initiator  505  and the responder  510 , the communication handler  540  may also store and maintain one or more previous tokens  590 ′ from such sessions on the database  560 . The communication handler  540  may store and maintain the association of the token  590 ′ with the prior session or the initiator  505  on the database  560 . The token  590 ′ may also be stored on the database  560  with an indication of whether the token  590 ′ is validated or not validated. The validation of the tokens  590  and  590 ′ is detailed herein below. 
     The path evaluator  545  executing on the responder  510  may identify or otherwise determine at least one property of the network  515  (or the path  520  established over the network  515 ). The property of the network  515  or the path  520  may include the routing technique for directing the communications over the network  515 , an access requisite to enter the network  515 , a communication protocol used to secure the communications over the network  515 , and a configuration of the initiator  505  with respect to the network  515 . The routing technique may include static routing or dynamic routing as discussed above. The access requisite may identify one or more conditions for the initiator  505  to enter the network  515 . The communication protocol may include protocols used to secure communications over the network  515  as discussed above. The configuration may include a type of the source address (e.g., static or dynamic IP address) corresponding to the initiator  505  and access requisites for the network  515 , among others. 
     To identify the property of the network  515 , the path evaluator  545  may parse the at least one of the messages (e.g., the initiation message  575 , the acknowledgement message  580 , and the token message  580 ) exchanged via the path  520  in establishing the session  570 . In some embodiments, the path evaluator  545  may retrieve or identify the session information from the initiation message  575  to identify the property of the network  515 . In some embodiments, the path evaluator  545  may parse the message to extract or identify the session information regarding the session  570  established via the path  520  over the network  515 . From parsing, the path evaluator  545  may identify the routing technique used by the path  520  over the network  515  as one of the properties of the network  515 . In some embodiments, the path evaluator  545  may identify a property of a point of access used to establish the session  570  to identify the property of the network  515 . The point of access may be a network node (e.g., a router or a gateway) or a network interface of a device (e.g., the communication interface  118 ). The property of the point of access may include, for example, the access requisite, the routing technique, or security mechanism. To identify the point of access, the path evaluator  545  may access the point of access associated with the session  570 . In some embodiments, the path evaluator  545  may determine the access requisite for the network  515  (e.g., physical or logical access based on the routing technique, and may use the access requisite as one of the properties for the network  515 . The path evaluator  545  may also identify the encryption protocol to be applied to the communications in the session  570  over the path  520  as another property of the network  515 . The path evaluator  545  may further identify the type of address for the network address referencing the initiator  505  (or the responder  510 ) as another property associated with the network  515 . 
     Based on the one or more properties of the network  515  (or the path  520 ), the path evaluator  545  may determine whether the network  515  (or the path  520  established over the network  515 ) is to be trusted. In determining, the path evaluator  545  may compare the properties of the network  515  with a rule set (also referred herein as a policy, requisites, or conditions) for trusted networks. The rule set may be predefined or pre-configured by a network administrator of the responder  510 , and may define, identify, or otherwise specify a combination of properties (e.g., routing technique, access requisite, encryption protocol, type of address) for the network  515  to be trusted. One combination of properties identified by the rule set may specify that the network  515  over which the session  570  is established be a MPLS network and the access requisite for the network  515  is physical access. Another combination of properties may define that the network address for the initiator  505  is a static address and that the routing technique employed by the network  515  is static routing. Another combination of properties defined by the rule set may identify that the initiator  505  is a static address and that the routing technique employed is reverse-path filtering. 
     When the properties identified for the network  515  (or the path  520 ) do not match with any combination of properties identified by the rule set for trusted networks, the path evaluator  505  may determine that the network  515  (or the path  520 ) is not to be trusted. The path evaluator  505  may also store and maintain an indication of the network  515  as untrusted onto the database  560 . In some embodiments, the path evaluator  505  may store an association of the network  505  as untrusted with the session information for the session  570  onto the database  560 . In some embodiments, the path evaluator  505  may store an association of the path  520  established over the network  515  as untrusted with the session information for the session  570  onto the database  560 . Otherwise, when the properties identified for the network  515  (or the path  520 ) match with at least one combination of properties laid out in the rule set for trusted networks, the path evaluator  505  may determine that the network  515  (or the path  520 ) is to be trusted. The path evaluator  505  may also store and maintain an indication of the network  515  as trusted on the database  560 . In some embodiments, the path evaluator  505  may store an association of the network  515  as trusted with the session information for the session  570 . In some embodiments, the path evaluator  505  may store an association of the path  520  established over the network  515  as trusted with the session information for the session  570 . 
     Depending on the determination as to whether the network  515  is determined to be trusted, the token validator  550  executing on the responder  510  may validate the token  590  from use in communications over one or more of the networks  515  (and paths  520 ) between the initiator  505  and the responder  510 . When the network  515  is determined to be trusted, the token validator  550  may validate the token  590  for use in communications over one or more networks  515  between the initiator  505  and the responder  510 . The token validator  550  may also store and maintain an indication of the token  590  as validated on the database  560 . Conversely, when the network  515  is determined to be not trusted, the token validator  550  may not validate or otherwise restrict the token  590  from use in the communications over one or more of the networks  515  except for the current session  570 . Further restrictions of the token  590  and the associated session  570  may be based on other factors and conditions. 
     In some embodiments, when the network  515  is determined to be not trusted, the token validator  550  may determine whether a previous token  590 ′ for the initiator  505  exists. The previous token  590 ′ may be from a previous session established between the initiator  505  and the responder  510  over any one of the networks  515 . In determining, the token validator  550  may access the database  560  to search or find the token  590 ′ associated with the initiator  505 . If no token  590 ′ associated with the initiator  505  is found, the token validator  550  may determine that no previous token  590 ′ for the initiator  505  exists. In addition, the token validator  550  may not validate or otherwise restrict the token  590  for use in communications over one or more of the networks  515 . The restriction of the token  590  may include the current session  570  and the path  520  over the network  515 . The token validator  550  may also store and maintain an indication of the  590  as not validated onto the database  560 . 
     On the other hand, if at least one token  590 ′ associated with the initiator  505  is found, the token validator  550  may determine whether the previous token  590 ′ was validated. As discussed above, the token  590 ′ may have been stored and maintained on the database  560  with an indication as to whether the previous token  590 ′ was validated. In determining, the token validator  550  may access the database  560  to identify the indication of validation for the previous token  590 ′ associated with the initiator  505 . If the indication identifies the previous token  590 ′ as not validated, the token validator  550  may not validate or otherwise restrict the token  590  for communications over one or more of the networks  515 , except for the current session  570 . The token  590  may be used for the current session  570  over the path  520  via the network  515 , but not for other communications over other networks  515  between the initiator  505  and the responder  510 . The token validator  550  may also store and maintain an indication of the token  590  as not validated onto the database  560 . In some embodiments, the token validator  550  may perform no further action upon determining that none of the session states are indicated as active. 
     In contrast, if the indication identifies the previous token  590 ′ as validated, the token validator  550  may determine whether other sessions or paths  520  between the initiator  505  and the responder  510  are active or inactive. To determine, the token validator  550  may access the database  560  to identify a session state for each of the other sessions established between the initiator  505  and the responder  510 . The session state may identify whether the other session is active or inactive. The identified session state may at least include that of the session associated with the previous token  590 ′. If any of the session states of the other session is indicated as active, the token validator  550  may permit or allow the current session  570  for communications. In addition, the token validator  550  may validate or permit the token  590  for use in communications in the current session  570 . In some embodiments, the validation of the token  590  may be limited to the current session  570  over the path  520 , but not for other communications over the other networks  515 . In some embodiments, the token validator  550  may carry out no further action in response to the determination to allow the current session  570 . On the other hand, if none of the session states of the other session is indicated as active, the token validator  550  may not validate or otherwise restrict the token  590  for communications over one or more of the networks  515 , including the current session  570 . In some embodiments, the token validator  550  may re-initiate negotiation of the token  590  in the manner described above. 
     The session controller  555  executing on the responder  510  may manage or handle the session  570  based on the determination as to whether the token  590  from the session  570  is validated or not validated. The handling of the session  570  may also be dependent on the restrictions determined based on the previous token  590 ′ and other sessions as discussed above. When the token  590  is validated, the session controller  555  may send, provide, or otherwise transmit the token  590  via at least one configuration message  595 . The configuration message  595  may include the token  590  and the indication that the token  590  is validated for communications across one or more of the networks  515  between the initiator  505  and the responder  510 . In some embodiments, the session controller  555  may generate the configuration message  595  to include the token  590  and at least a portion of the information discussed above included in the previous messages. By providing the configuration message  595 , the session controller  555  may indicate to the initiator  505  that the token  590  is permitted to be used for communications over one or more of the networks  515  between the initiator  505  and the responder  510 . 
     On the other hand, when the token  590  is not validated, the session controller  555  may generate the configuration message  595  to send, provide, or otherwise transmit to the initiator  505  according to the determination of restrictions for the token  590 . If the token  590  is not validated for communications including for the current session  570 , the session controller  555  may restrict the session  570  over the path  520  of the network  515 . In some embodiments, the session controller  555  may terminate or cease the establishment of the session  570  over the path  520  via the network  515 . The session controller  555  may include the token  590  and an indication to restrict (e.g., terminate) the session  570  associated with the token  590  in the configuration message  595 . In some embodiments, the indication may also identify that the token  590  is not to be used over any communications over any of the networks  515  with the responder  510 . With the inclusion, the session controller  555  may transmit the configuration message  595  to the initiator  505  via the path  520  over the network  515 . Conversely, if the token  590  is not validated for communications excluding the current session  570 , the session controller  555  may generate the configuration message  595  to include the token  590  and an indication that the token  590  is validated for communications limited to the network  515 . The indication may also identify that the token  590  is not validated for communications over other networks  515  between the initiator  505  and the responder  510 . Upon inclusion, the session controller  555  may transmit the configuration message  595  to the initiator  505  via the path  520  over the network  515 . 
     From the responder  510 , the token handler  530  executing on the initiator  505  may identify or receive the configuration message  595 . Upon receipt, the token handler  530  may parse the configuration message  595  to extract or identify the token  590  and the indication. Based on the indication, the token handler  530  may manage or configure the session  570  established over the path  520  via the network  515 . When the indication is that the token  590  is to restrict the session  570 , the token handler  530  may terminate or cease the session  570  associated with the token  590  and communications with the responder  510  over the session  570 . In some embodiments, the token handler  530  may also terminate or cease the session  570 , when the indication from the configuration message  595  is that the token  590  is not validated for any communications between the initiator  505  and the responder  510 . 
     In addition, when the indication is that the token  590  is validated for use in communications limited to the network  515 , the token handler  530  may use the token  590  for subsequent communications with the responder  510  within the current session  570 . The token handler  530  may allow or permit continued communications from the initiator  505  to the responder  510  over the current session  570  via the network  515 . The token handler  530  may store and maintain the token  590  on the database  535  for communications over the network  515  over which the session  570  is established. With the indication, the token handler  530  may refrain from using the token  590  in communications over other networks  515  with the responder  510 . The token  590  may be used for the duration of the session  570  via the path  520  over the network  515 , but may not be used in communications for other networks  515 . Otherwise, when the indication is that the token  590  is validated for use in communications over one or more of the networks  515 , the token handler  530  may use the token  590  for subsequent communications with the responder  510 . The token handler  530  may also allow or permit continued communications from the initiator  505  to the responder  510 . Furthermore, the token handler  530  may store and maintain the token  590  on the database  535  for communications over one or more other networks  515  with the responder  510 . 
     Referring now to  FIG. 5C , depicted is the system  500  for revalidating session tokens focused on one of the paths  520 ′ (e.g., the path  515 B) of one network  515  (e.g., the network  515 B) between the initiator  505  and the responder  510 . Subsequently, with the indication that the token  590  is validated for use in communications over other networks  520 , the session interface  525  may initiate another session  570 ′ over another path  520 ′ via another network  515  using the token  590 . The network  515  over which the subsequent session  570 ′ may have properties that would be determined to be not trusted under the rule set applied by the path evaluator  545 . Nonetheless, as the token  590  may have been previously validated over the other network  515  with properties determined to be trusted, the session interface  525  may use the token  590  to establish the subsequent session  570 ′ over the network  515 . The initiation of the subsequent session may be performed in a similar manner as discussed above. For example, the session interface  525  may transmit an initiation message  575 ′ containing information for establishment of the new session  570 ′. In return, the communication handler  540  may respond with an acknowledgment message  580 ′ to the initiator  505  to complete the establishment of the session  570 ′ between the initiator  505  and the responder  510  via the path  520  of the network  515 . With the establishment of the session  570 ′, the session interface  525  may access the database  530  to retrieve or identify the token  590  previously validated at the responder  510 . Once identified, the session interface  525  may generate a token message  585 ′ to include the token  590 ′ from the database  535 . The session interface  525  may send, transmit, or otherwise provide the token message  585 ′ including the token  590 ′ to the initiator  505 . 
     In turn, the communication handler  540  may identify or receive the token message  585 ′ sent by the initiator  505 . Upon receipt, the communication handler  540  of the responder  510  may parse the token message  585 ′ to extract or identify the token  590 . The token validator  550  may determine whether the token  590  identified from the token message  585  was previously validated. To determine, the token validator  550  may search or find the database  560  using the token  590  identified from the token message  585 ′. As the token  590  was previously validated, the token validator  550  may find the token  590 ′ stored and maintained on the database  560  that matches token  590 . When found, the token validator  550  may determine that the token  590  has been previous validated. In some embodiments, based on the finding of the match, the token validator  550  may revalidate the token  590  without determination as to whether the network  515  to which the path  520 ′ belongs is to be trusted. In response to the determination that the token  590  was previously validated, the session controller  595  may transmit the token  590  via at least one configuration message  595 ′ to the initiator  505 . The configuration message  595 ′ may also include the indication that the token  590  is re-validated for communications across one or more of the networks  515  between the initiator  505  and the responder  510 . 
     From the responder  510 , the token handler  530  of the initiator  505  may identify or receive the configuration message  595 ′. Upon receipt, the token handler  530  may parse the configuration message  595  to extract or identify the token  590  and the indication. Based on the indication that token  590  is re-validated for use in communications over one or more of the networks  515 , the token handler  530  may use the token  590  for subsequent communications with the responder  510  in the new session  570 ′. The token handler  530  may also allow or permit continued communications from the initiator  505  to the responder  510 . 
     Referring now to  FIG. 5D , depicted is a block diagram of the system  500  for validating session tokens from various initiators  505  (e.g., initiators  505 A and  505 B) over multiple networks (e.g., networks  515 A-C) and multiple paths (e.g., paths  520 A-E). The functionalities of the initiators  505 A and  505 B and the responder  510  may be similar to those detailed herein above. The validation of tokens  590  over a network  515  (e.g., the networks  515 A and  515 B as depicted) that is determined to be trusted may be used to establish a session  570  over a network  515  (e.g., the network  515 C as depicted) that would be determined as not trusted. The initiations of the session  570  between the initiator  505 A and the responder  510  over the network  515 A and the session  570  between the initiator  505 B and the responder  510  over the network  515 B may be performed as discussed above. With the initiation, the session interface  525  of the initiator  505 A may transmit a token message  585 A including a token  590 A to the responder  510 . The token  590 A may identify the session established over the network  515 A. Likewise, the session interface  525  of the initiator  505 B may transmit a token message  585 B including a token  590 B to the responder  510 . 
     With the receipt of the token messages  585 A and  585 B, the communication handler  540  of the responder  510  may parse the token message  585 A to identify the token  590 A and parse the token message  585 B to identify the token  590 B. The path evaluator  545  of the responder  510  may determine whether the network  515 A associated with the token  590 A is to be trusted based on a property of the network  515 A. Similarly, the path evaluator  545  of the responder  510  may determine whether the network  515 B associated with the token  590 B is to be trusted based on a property of the network  515 B. 
     When one of the networks  515  (e.g., the network  515 B contrary to the depiction) is determined to be not trusted, the session controller  555  of the responder  510  may not validate the token  590  (e.g., the token  590 B) associated with the network  515 . The session controller  555  may also restrict the session  570  over the network  515  in the manner as discussed above. The session controller  555  may provide a configuration message  595  to the initiator  505 B with an indicator that the token  590  is not validated for communications. In contrast, the other network  515  (e.g., the network  515 A) may be determined to be trusted based on the property of the network  515 A. For example, the network  515 A may be a MPLS network that would have properties determined to be trusted, whereas the network  515 B may be a public Internet network that would have properties determined to be not trusted. Based on these determinations, the session controller  555  may transmit a configuration message  595  including an indicator to the initiator  505 A in communication over the other network  515 A that the token  590 B is not validated. The configuration message  595  may include the token  590 A with an indication that the token  590 A has been validated for communications with the responder  510 . For example, the initiator  505 A may use the token  950 A for communications over the path  520 A via the network  515 A and over the path  520 C via the network  515 C. With the receipt of the configuration message  595 , the initiator  505 A may continue communications with the responder  510  over the network  515 A. 
     Conversely, when both the networks  515 A and  515 B are determined to be trusted (e.g., as depicted), the token validator  550  of the responder  510  may validate the tokens  590 A and  590 B. For example, the network  515 A and  515 B may be both MPLS networks. Based on the validation, the session controller  555  of the responder  510  may transmit a configuration message  595  to the initiator  505 A including an indicator that the token  590 A is validated for communications among the initiators  505 A and  505 B and the responder  510 . The communications may include, for example, those over the path  520 A-E over networks  515 A-C. In some embodiments, the session controller  555  may also provide the token  590 B from the initiator  505 B to the initiator  505 A via the configuration message  595 . Furthermore, the session controller  555  may transmit a configuration message  595  to the initiator  505 B including an indicator that the token  590 B is validated for communications among the initiators  505 A and  505 B and the responder  510 . In some embodiments, the session controller  555  may also provide the token  590 A from the initiator  505 A to the initiator  505 B via the configuration message  595 . 
     Subsequently, the token handler  530  of the initiator  505 A may receive the configuration message  595  from the responder  910 . The token handler  530  of the initiator  505 A may identify both the tokens  950 A and  950 B for use in communications among the initiator  505 A and  505 B and the responder  510 . The token handler  530  may store and maintain the tokens  950 A and  950 B on the database  536  of the initiator  505 A. Likewise, the token handler  530  of the initiator  505 B may receive the configuration message  595  from the responder  910 . The token handler  530  of the initiator  505 B may identify both the tokens  950 A and  950 B for use in communications among the initiator  505 A and  505 B and the responder  510 . The token handler  530  may store and maintain the tokens  950 A and  950 B on the database  536  of the initiator  505 B. 
     To establish a session over the network  515 C, each of the initiator  505 A and  505 B may perform a procedure as discussed above, and exchange the initiation message  575  and acknowledgement message  580  with each other over the path  520 E of the network  515 C. The network  515 C may have one or more properties that would be determined to be untrusted by the path evaluator  545  of the responder  510 . With the establishment of the session, the initiators  505 A and  505 B may exchange token messages  585 C and  585 D respectively over the network  515 C. The token message  585 C from the initiator  505 A may include the token  590 B of the initiator  505 B validated by the responder  510 . Conversely, the token message  585 D from the initiator  505 B may include the token  590 A of the initiator  505 A validated by the responder  510 . With the receipt of the token  590 A and  590 B, the session interface  525  at each initiator  505 A and  505 B may check whether the token  590 A or  590 B is stored on the respective database  535  to revalidate the token  590 A and  590 B. When found, the session interface  525  of each initiator  505 A and  505 B may send a configuration message  595  to indicate the re-validation of the tokens  590 A and  590 B. 
     Referring now to  FIG. 6 , depicted is a communication diagram of a process  700  for validating session tokens using network properties. The functionalities of process  700  may be implemented using, or performed by, the components described in  FIGS. 1-5 , such as the initiator  505  or the responder  510 . In brief overview, the initiator  505  may send a start session message via an Internet path to the responder  510  ( 605 ). The responder  510  may return a session started message via the Internet path to the initiator  505  ( 610 ). The initiator  505  may provide a multipath token to the responder  510  via the Internet path ( 615 ). As the Internet path is untrusted, the responder  510  may reject the token ( 620 ). The responder  510  may terminate the session over the Internet path ( 625 ). 
     The initiator  505  may send a start session message via a multiprotocol label switching (MPLS) path to the responder  510  ( 630 ). The responder  510  may return a session started message via the MPLS path to the initiator  505  ( 635 ). The initiator  505  may provide a new multipath token to the responder  510  via the MPLS path ( 640 ). As the MPLS path is trust, the responder  510  may accept the token and permit the MPLS path for network traffic ( 645 ). The responder  510  may return token as validated over the MPLS path to the initiator  505  ( 650 ). The initiator  505  may in turn approve and store the validated token ( 655 ). 
     Subsequently, the initiator  505  may send a start session message via an Internet path to the responder  510  ( 660 ). The responder  510  may return a session started message via the Internet path to the initiator  505  ( 665 ). The initiator  505  may provide the previously validated multipath token to the responder  510  via the Internet path ( 670 ). Since the token was previously provided over the MPLS path and was validated, the responder  510  may permit the Internet path for network traffic ( 675 ). The responder  510  may return token over the Internet path to the initiator  505  ( 680 ). The initiator  505  may permit the Internet path for network traffic ( 685 ). 
     Referring now to  FIG. 7 , depicted is a flow diagram for a method  800  of validating session tokens using network properties. The functionalities of method  800  may be implemented using, or performed by, the components described in  FIGS. 1-7 , such as the initiator  505  or the responder  510 . In overview, an initiator may initiate a session ( 705 ). A responder may identify a token ( 710 ). The responder may determine whether a path is to be trusted ( 715 ). If the path is not to be trusted, the responder may determine whether a previous token exists ( 720 ). If the previous token exists, the responder may determine whether the previous token was validated ( 725 ). If the previous token was validated, the responder may determine whether other paths are active ( 730 ). If no previous tokens exists or when at least one path is determined to be active, the responder may restrict the new session ( 735 ). Otherwise, if no other paths are active or no previous token was validated, the responder may take no action ( 740 ). On the other hand, if the path is to be trusted, the responder may validate the token ( 745 ). The responder may provide the token ( 750 ). The initiator may receive the token ( 755 ). The initiator may store the token ( 760 ). The initiator may use the token in a session ( 765 ). The responder may accept the token for the session ( 770 ). 
     In further detail, an initiator (e.g., the initiator  505 ) may initiate a session (e.g., the session  570 ) with a responder (e.g., the responder  510 ) ( 705 ). The initiator and the responder may exchange a set of messages (e.g., the initiation message  575  and the acknowledgement message  580 ) to establish the session. The session may be established over a path (e.g., the path  520 ) via a network (e.g., the network  515 ) between the initiator and the responder. The responder may identify a token (e.g., the token  590 ) ( 710 ). From the initiation of the session, the initiator may provide a message (e.g., the token message  585 ) including the token to the responder. The responder may parse the message to identify the token. 
     The responder may determine whether the path is to be trusted ( 715 ). The responder may identify properties of the network associated with the path. The properties of the network may include a routing technique applied, an access requisite to enter the network, a communication protocol, a configuration of the initiator or the responder, among others. The responder may compare the properties of the network with a rule set defining conditions to be a trusted network. When the properties match, the responder may determine that the path is to be trusted. Otherwise, when any of the properties do not match, the responder may determine that the path is not to be trusted. 
     If the path is not to be trusted, the responder may determine whether a previous token exists ( 720 ). The previous token may be from a previous session established between the initiator and the responder. The responder may access a database (e.g., the database  560 ) to find whether the previous token exists. If the previous token exists, the responder may determine whether the previous token was validated ( 725 ). The responder may access the database to identify an associated indicator as to whether the previous token was validated. 
     If the previous token was validated, the responder may determine whether other paths are active ( 730 ). The responder may access the database to identify session information each of the paths between the initiator and the responder. The session information may identify whether the path (or session) is active or inactive. When the session information indicates that the path is active, the responder may determine that the path is active. Conversely, when the session information indicates that the path is inactive, the responder may determine that the path is inactive. If no previous tokens exists or when at least one path is determined to be active, the responder may restrict the new session ( 73   5 ). Otherwise, if no other paths are active or no previous token was validated, the responder may take no action ( 740 ). 
     On the other hand, if the path is to be trusted, the responder may validate the token ( 745 ). The token may be validated for communications via other networks and paths between the initiator and the responder. The responder may provide the token ( 750 ). The responder may send the token using a message (e.g., the configuration message  595 ) to the initiator. The initiator may receive the token ( 755 ). The initiator may parse the message received from the responder to identify the token. The initiator may store the token ( 760 ). Upon identification, the initiator may store and maintain the token on a database (e.g., the database  535 ) for communications between the initiator and the responder. The initiator may use the token in a session (e.g., the session  570 ′) ( 765 ). The session may be established over another network via another path (e.g., the path  520 ′) The responder may accept the token for the session ( 770 ). The acceptance of the token may be performed without any determination as to whether the network is to be trusted. 
     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.