RELATED APPLICATIONS

[0001] The subject matter of this application is related to the subject matter in the following applications:

U.S. Patent Application No. 13/847,814, entitled "ORDERED-ELEMENT NAMING FOR NAME-BASED PACKET FORWARDING," by inventor Ignacio Solis, filed 20 March 2013 (hereinafter "U.S. Pat. App. No. 13/847,814"); and U.S. Patent Application No.

12/338, 175 entitled "CONTROLLING THE SPREAD OF INTERESTS AND CONTENT IN A CONTENT CENTRIC NETWORK," by inventors Van L. Jacobson and Diana K.

Smetters, filed 18 December 2008 (hereinafter "U.S. Pat. App. No. 12/338, 175"); the disclosures of which are herein incorporated by reference in their entirety.

BACKGROUND

Field

[0002] This disclosure is generally related to distribution of digital content. More specifically, this disclosure is related to a system and method for facilitating the exchange of identifying information between connected nodes in a content centric network without requiring an external agent.

Related Art

[0003] The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients, forwarders (e.g., routers), and content producers, which communicate with each other by sending interest packets for various content items and receiving content object packets in return. CCN interests and content objects are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level.

[0004] In CCN, an external initiating agent can establish explicit connections between connected forwarders by naming the connections and providing the names and related information associated with these connections to the agent's local router. In some instances, a connection may be established by a listening node (e.g., the local router), but the connection may not be explicitly solicited by a recipient node (e.g., a connection end-point). This type of unsolicited connection has no identity other than the source address provided by the connection end-point. So, the local router has no other information regarding either the entity attached to the end-point or a logical name for the end-point.

[0005] While a CCN brings many desired features to a network, some issues remain unsolved for connecting forwarders before connections are established and available for CCNx messaging.

SUMMARY

[0006] One embodiment provides a system which facilitates an exchange of identifying information between connected nodes. During operation, the system generates, by an intermediate node for an adjacent node, an interest which includes an identifier for the intermediate node and a name for a link between the intermediate node and the adjacent node. In response to the interest, the system receives from the adjacent node a content object which includes an identifier for the adjacent node. The system creates an entry in a first data structure mapping the adjacent node's identifier to a first outgoing interface associated with the link. In response to receiving a first routing update for a first name prefix based on the adjacent node's identifier, the system updates a first forwarding information base based on the adjacent node's identifier, thereby facilitating the exchange of the identifying information between the connected nodes without requiring an external agent.

[0007] In some embodiments, the content object further includes the intermediate node's identifier and the link name.

[0008] In some embodiments, updating the forwarding information base further comprises: performing a lookup in the first data structure based on the adjacent node's identifier to obtain the corresponding first outgoing interface; and creating an entry in the first forwarding information base mapping the first name prefix to the obtained first outgoing interface.

[0009] In some embodiments, the interest further includes a signature of the intermediate node, and the content object further includes a signature of the adjacent node.

[0010] In some embodiments, the adjacent node receives the interest. The adjacent node verifies the interest based on a signature of the intermediate node included in the interest. In response to verifying the interest, the adjacent node: generates the content object; creates an entry in a second data structure mapping the intermediate node's identifier to a second outgoing interface associated with the link; and, in response to receiving a second routing update for a second name prefix based on the intermediate node's identifier, updates a second forwarding information base based on the intermediate node's identifier. In response to not verifying the interest, the adjacent node discards the interest.

[0011] In some embodiments, in response to verifying the content object, the system, by the intermediate node, enables a connection between the intermediate node and the adjacent node, wherein the connection is based on the link between the intermediate node and the adjacent node, wherein verifying the content object is based on a signature of the adjacent node included in the content object. In response to not verifying the content object, the system refrains from enabling the connection between the intermediate node and the adjacent node.

[0012] In some embodiments, a name is a hierarchically structured variable length identifier that includes contiguous name components ordered from a most general level to a most specific level, and a name for the interest is the same as a name for the content object.

BRIEF DESCRIPTION OF THE FIGURES

[0013] FIG. 1A illustrates an exemplary network which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0014] FIG. IB illustrates an exemplary network which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0015] FIG. 2A illustrates an exemplary interest which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0016] FIG. 2B illustrates an exemplary content object which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0017] FIG. 2C illustrates an exemplary node identifier table which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0018] FIG. 2D illustrates an exemplary forwarding information base which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. [0019] FIG. 3 presents a flow chart illustrating a method by an intermediate node for facilitating an exchange of identifying information with a connected adjacent node, in accordance with an embodiment of the present invention.

[0020] FIG. 4 presents a flow chart illustrating a method by an adjacent node connected to an intermediate node for facilitating an exchange of identifying information with the

intermediate node, in accordance with an embodiment of the present invention.

[0021] FIG. 5 illustrates an exemplary computer system that facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention.

[0022] In the figures, like reference numerals refer to the same figure elements.

DETAILED DESCRIPTION

[0023] The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Overview

[0024] Embodiments of the present invention provide a system which allows forwarders to exchange identity information with other connected and adjacent forwarders before connections are both established by an external agent and available for CCNx messaging. In CCN, an external initiating agent can establish explicit connections between connected forwarders by naming the connections and providing the names and related information associated with these connections to the agent's local router. In some instances, a connection may be established by a listening node (e.g., the local router), but the connection may not be explicitly solicited by a recipient node (e.g., a connection end-point). This type of unsolicited connection has no identity other than the source address provided by the connection end- point. So, the local router has no other information regarding either the entity attached to the end-point or a logical name for the end-point. Instead, the local router, and other forwarders, must make assumptions (or wait to be told) about new and unsolicited connections. Names for unsolicited connections may be derived from available information in the packet header. However, the available information may or may not be mapped to a logical or well-known name.

[0025] Embodiments of the present invention solve this problem by providing a system which facilitates an exchange of identifying information between connected nodes before connections are established by an external agent. The exchange of identifying information updates certain tables (e.g., "node identifier tables") by mapping a given node identifier to a corresponding outgoing interface or interfaces. This allows a routing protocol to run after the forwarders have exchanged identifying information, where the forwarders process routing updates by using the previously exchanged identifying information to populate the FIBs for a respective forwarder. One embodiment is provided in the CCNx Athena forwarder, which exchanges message with a new connection request (which includes a provided identity) and names the connection with the provided identity.

[0026] Embodiments of the present invention thus eliminate the need for an external agent to explicitly identify and name connections between connected and adjacent nodes. Router entries may be made using the identifying information for forwarders (e.g., the names of forwarders), which are already mapped and authenticated. In some embodiments, packets between forwarders may be identified by their signature, which allows multiple channels to be multiplexed across a single link by using different and negotiated signatures.

[0027] Thus, the present system provides improvements to the distribution of digital content, where the improvements are fundamentally technological. Embodiments of the present invention provide a technological solution (e.g., facilitating the exchange of identifying information between connected forwarders without requiring an external agent, where the exchange occurs in advance of a routing protocol, and where the results of the exchange are used in subsequent routing updates as part of the routing protocol) to the technological problem of the efficient, secure, and effective distribution of digital content.

[0028] In CCN, each piece of content is individually named, and each piece of data is bound to a unique name that distinguishes the data from any other piece of data, such as other versions of the same data or data from other sources. This unique name allows a network device to request the data by disseminating a request or an interest that indicates the unique name, and can obtain the data independent from the data's storage location, network location, application, and means of transportation. The following terms are used to describe the CCN architecture:

Content Object (or "content object"): A single piece of named data, which is bound to a unique name. Content Objects are "persistent," which means that a Content Object can move around within a computing device, or across different computing devices, but does not change. If any component of the Content Object changes, the entity that made the change creates a new Content Object that includes the updated content, and binds the new Content Object to a new unique name.

Unique Names: A name in a CCN is typically location independent and uniquely identifies a Content Object. A data-forwarding device can use the name or name prefix to forward a packet toward a network node that generates or stores the Content Object, regardless of a network address or physical location for the Content Object. In some embodiments, the name may be a hierarchically structured variable-length identifier (HSVLI). The HSVLI can be divided into several hierarchical components, which can be structured in various ways. For example, the individual name components pare, home, ccn, and test.txt can be structured in a left-oriented prefix-major fashion to form the name "/parc/home/ccn/test.txt." Thus, the name "/parc/home/ccn" can be a "parent" or "prefix" of "/parc/home/ccn/test.txt."

Additional components can be used to distinguish between different versions of the content item, such as a collaborative document. The HSVLI can also include contiguous name components ordered from a most general level to a most specific level.

[0029] In some embodiments, the name can include an identifier, such as a hash value that is derived from the Content Object's data (e.g., a checksum value) and/or from elements of the Content Object's name. A description of a hash-based name is described in U.S. Patent Application No. 13/847,814, which is herein incorporated by reference. A name can also be a flat label. Hereinafter, "name" is used to refer to any name for a piece of data in a name- data network, such as a hierarchical name or name prefix, a flat name, a fixed-length name, an arbitrary-length name, or a label (e.g., a Multiprotocol Label Switching (MPLS) label). Interest (or "interest"): A packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or Interest across an information-centric network, which CCN/NDN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or Interest.

Face or Interface (or "face" or "interface"): In CCN, the term "face" is a generalization of the concept of an interface. A face may be a connection to a network or directly to an application party. A face may be configured to send and receive broadcast or multicast packets on a particular network interface, or to send and receive packets using point-to-point addressing in the underlying transport, or using a tunnel (for example a TCP tunnel). A face may also be the connection to a single application process running on the same machine, via an encapsulation like UDP or an OS-specific inter-process communication path. All messages arrive through a face and are sent out through a face. In this disclosure, the term "neighbor" is interchangeable with the terms "face" and "interface," referring to an incoming or outgoing interface of an Interest.

"Prefix": In this disclosure, the term "prefix" can be used to refer to either a name of a specific content object or a name prefix for the content object. A routable name prefix can determine the routing of a packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or interest across an information-centric network, which CCN/NDN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or interest.

[0030] The methods disclosed herein are not limited to CCN networks and are applicable to other architectures as well. A description of a CCN architecture is described in U.S. Pat. App. No. 12/338,175, which is herein incorporated by reference.

Exemplary Network and Communication

[0031] FIG. 1 A illustrates an exemplary network 100 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. Network 100 can include a consumer or content requesting device 116, a producer or content producing device 118, and a router or other forwarding device at nodes 102, 104, 106, 108, 110, 112, and 114. A node can be a computer system, an end-point representing users, and/or a device that can generate interests or originate content. A node can also be an edge router (e.g., CCN nodes 102, 104, 112, and 114) or a core router (e.g., intermediate CCN routers 106, 108, and 110). Network 100 can be a content centric network.

[0032] Before any routing updates are transmitted or processed as part of a routing protocol, connected nodes in network 100 can communicate directly with one another to exchange identifying information. The exchanged information can be used to update a node identifier table, which can be subsequently searched when processing a routing update. For example, node 110 and node 112 can participate in an exchange of identifying information. Node 110 can generate an interest 120, which can indicate a request to exchange identifying

information with adjacent node 112. Interest 120 can include a name 120.1 of

"/gen/req/node/id," an "initiating" node identifier 120.2 which is a node identifier for node 110, such as "K ID," and can also include a link name 120.3 which is a name for a link between nodes 110 and 112, such as "Link_1234." Upon receiving interest 120, node 112 can verify the interest based on a signature of node 110 included in interest 120. Node 112 can generate a responsive content object 122, which can include a "target" node identifier 122.3 which is a node identifier for node 112, such as "A ID," and transmit content object 122 back to node 110. Content object 122 can also include a name 122.1 of

"/gen/req/node/id" which is the same as name 120.1 of interest 120, an initiating node identifier 122.2 of "K ID" which is the same as initiating node identifier 120.2 of interest 120, and a link name 122.4 of "Link_1234" which is the same as link name 120.3 of interest 120. Content object 122 can also include a signature (not shown) of node 112. Node 112 can create an entry in a node identifier table 160, where the entry maps node 110's identifier ("K ID") to the outgoing port associated with the link ("port 1").

[0033] Upon receiving content object 122, node 110 can verify content object 122 based on the signature of node 112 included in content object 122. Node 110 can enable the connection between node 110 and node 112. Similar to how node 112 processes interest 120, node 110 can process content object 122 by creating an entry in a node identifier table 140, where the entry maps node 112's identifier ("A ID") to the outgoing port associated with the link ("port_27").

[0034] Subsequent routing updates can populate a respective forwarding information base (FIB) based on the mappings stored in a respective node identifier table. For example, node 110 can receive a routing update for the name prefix "/pare/ A," indicating that this name prefix is to point to the interface (or interfaces) associated with the node identified by "A ID." Node 110 can update its FIB 150 based on adjacent node 112's identifier ("A ID"). Node 110 can perform a lookup in node identifier table 140 based on adjacent node 112's identifier ("A ID") to obtain a corresponding outgoing interface ("port_27"). Node 110 can create an entry in FIB 150 mapping the name prefix "/pare/ A" to the corresponding outgoing interface "port_27."

[0035] Similarly, node 112 can receive a routing update for the name prefix "/parc/K," indicating that this name prefix is to point to the interface (or interfaces) associated with the node identified by "K ID." Node 112 can update its FIB 170 based on adjacent node 110's identifier ("K ID"). Node 112 can perform a lookup in node identifier table 160 based on adjacent node 110's identifier ("K ID") to obtain a corresponding outgoing interface

("port_l"). Node 112 can create an entry in FIB 170 mapping the name prefix "/parc/K" to the corresponding outgoing interface "port l ." [0036] Data packets such as interests which are subsequently generated by, i.e., client device 116, can be processed based on standard CCN rules, as described in U.S. Pat. App. Nos. 13/847,814 and 12/338, 175, and as depicted below in relation to FIG. IB.

[0037] FIG. IB illustrates an exemplary network 100 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. During operation, client device 116 can generate an interest 180 with a name 180.1 of "/parc/A/bsj/end" and a payload 180.2 of "<data>." Interest 180 can travel through network 100, passing through various intermediate nodes (such as nodes 102, 110, 112, and 114) before reaching content producing device 118. Interest 180 can travel through network 100 based on information in the FIBs of the various intermediate nodes. For example, node 110 can receive interest 180 and perform a longest prefix match in its FIB 150 to obtain an entry for the name prefix "/parc/A/bsj" with a corresponding outgoing interface of "port_27." Node 110 can subsequently forward interest 180 via the interface associated with "port_27" (i.e., to adjacent node 112). In this manner, data plane activity proceeds in the same manner based on the control plane activity previously described in relation to FIG. 1A.

[0038] Thus, the system facilitates connected and adjacent nodes to exchange identifying information by populating a node identifier table (or other similar data structure). This allows the nodes to process subsequent routing updates by populating their respective FIBs. Subsequently received data packets may then be processed per standard CCN rules (e.g., interest 180 of FIG. IB).

Exemplary Interests, Content Objects, and Data Structures

[0039] FIG. 2A illustrates an exemplary interest 200 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. Interest 200 can include a name 202 of "/general/request/node/id," an initiating node identifier 204 of "K ID," a link name 206 of "Link_1234," and a payload 208 of "<data>." Name 202 indicates that interest 200 is a request to exchange identifying information with an adjacent node. The indication of this request can also be included in a field or in another manner under the protocol.

[0040] FIG. 2B illustrates an exemplary content object 210 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. Content object 210 can include a name 212 of "/general/request/node/id," an initiating node identifier 214 of "K ID," a target node identifier 216 of "A ID," a link name 218 of "Link_1234," and a payload 220 of "<data>."

[0041] FIG. 2C illustrates an exemplary node identifier table 230 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. Table 230 can include entries with a node identifier 232 and outgoing interfaces 234. For example, entry 230.1 can include a node identifier of "K ID" and outgoing interfaces of "{port l, ... }."

[0042] FIG. 2D illustrates an exemplary forwarding information base 240 which facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. FIB 240 can include entries with a name prefix 242 and outgoing interfaces 244. For example, entry 240.1 can include a name prefix of

"/parc/K" and outgoing interfaces of "{port_l, ... }."

Intermediate Node Initiates an Exchange of Identifying Information

[0043] FIG. 3 presents a flow chart 300 illustrating a method by an intermediate node for facilitating an exchange of identifying information with a connected adjacent node, in accordance with an embodiment of the present invention. During operation, the system generates, by an intermediate node for an adjacent node, an interest which includes an identifier for the intermediate node and a name for a link between the intermediate node and the adjacent node (operation 302). The interest can also indicate (e.g., in the name or another field of the interest) a request to exchange identifying information with the adjacent node. In response to the interest, the intermediate node receives from the adjacent node a content object which includes an identifier for the adjacent node (operation 304). The intermediate node verifies the content object (decision 306), which can be based on a signature for the adjacent node included in the content object. If the intermediate node does not successfully verify the content object, the intermediate node refrains from enabling a connection on the link (operation 308) and the operation returns.

[0044] If the intermediate node successfully verifies the content object, the intermediate node enables a connection between the intermediate node and the adjacent node, wherein the connection is based on the link between the intermediate node and the adjacent node

(operation 310). The intermediate node creates an entry in a first data structure mapping the adjacent node's identifier to a first outgoing interface associated with the link (operation 312). The first data structure can be a node identifier table of the intermediate node. [0045] Subsequently, the intermediate node receives a first routing update for a first name prefix based on the adjacent node's identifier (operation 314). The intermediate node performs a lookup in the first data structure based on the adjacent node's identifier to obtain the corresponding first outgoing interface (operation 316). The intermediate node creates an entry in a first forwarding information base mapping the first name prefix to the obtained first outgoing interface (operation 318).

Adjacent Node Participates in an Exchange of Identifying Information

[0046] FIG. 4 presents a flow chart 400 illustrating a method by a node adjacent to an intermediate node for facilitating an exchange of identifying information with the

intermediate node, in accordance with an embodiment of the present invention. The operations described in flow chart 400 can occur as a result of and in conjunction with the operations described above in relation to flow chart 300 of FIG. 3. During operation, the system receives, by a node adjacent to an intermediate node, from the intermediate node, an interest which includes an identifier for the intermediate node and a name for a link between the intermediate node and the adjacent node (operation 412). The adjacent node verifies the interest (decision 404), which can be based on a signature for the intermediate node included in the interest. If the adjacent node does not successfully verify the interest, the adjacent node discards the interest (operation 406) and the operation returns.

[0047] If the adjacent node successfully verifies the interest, the adjacent node generates a content object which includes an identifier for the adjacent node (operation 408). The adjacent node creates an entry in a second data structure mapping the intermediate node's identifier to a second outgoing interface associated with the link (operation 410). The second data structure can be a node identifier table of the adjacent node.

[0048] Subsequently, the adjacent node receives a second routing update for a second name prefix based on the intermediate node's identifier (operation 412). The adjacent node performs a lookup in the second data structure based on the intermediate node's identifier to obtain the corresponding second outgoing interface (operation 414). The adjacent node creates an entry in a second forwarding information base mapping the second name prefix to the obtained second outgoing interface (operation 416).

Exemplary Computer System

[0049] FIG. 5 illustrates an exemplary computer system that facilitates an exchange of identifying information between connected nodes, in accordance with an embodiment of the present invention. Computer system 502 includes a processor 504, a memory 506, and a storage device 508. Memory 506 can include a volatile memory (e.g., RAM) that serves as a managed memory, and can be used to store one or more memory pools. Furthermore, computer system 502 can be coupled to a display device 510, a keyboard 512, and a pointing device 514. Storage device 508 can store an operating system 516, a content-processing system 518, and data 528.

[0050] Content-processing system 518 can include instructions, which when executed by computer system 502, can cause computer system 502 to perform methods and/or processes described in this disclosure. Specifically, content-processing system 518 may include instructions for sending and/or receiving data packets to/from other network nodes across a computer network, such as a content centric network (communication module 520). A data packet can include an interest packet or a content object packet with a name which is an HSVLI that includes contiguous name components ordered from a most general level to a most specific level. A data packet can also include a control packet (which can also be an interest or a content object).

[0051] Furthermore, content-processing system 518 can include instructions for, generating an interest which includes an identifier for an intermediate node and a name for a link between the intermediate node and an adjacent node (packet-generating module 522).

Content-processing system 518 can include instructions for, in response to the interest, receiving from the adjacent node a content object which includes an identifier for the adjacent node (communication module 520). Content-processing system 518 can also include instructions for creating an entry in a first data structure mapping the adjacent node's identifier to a first outgoing interface associated with the link (node id table-managing module 524). Content-processing system 518 can include instructions for, in response to receiving a first routing update for a first name prefix based on the adjacent node's identifier, updating a first forwarding information base based on the adjacent node's identifier (FIB- updating module 526).

[0052] Content-processing system 518 can further include instructions for performing a lookup in the first data structure based on the adjacent node's identifier to obtain the corresponding first outgoing interface (node id table-managing module 524), and for creating an entry in the first forwarding information base mapping the first name prefix to the obtained first outgoing interface (FIB-updating module 526).

[0053] Content-processing system 518 can additionally include instructions for verifying an interest or a content object based on a signature of the intermediate node included in an interest or a signature of the adjacent node included in the content object (verification module 528). Content-processing system 518 can include instructions for, in response to verifying the content object (verification module 528), enabling a connection between the intermediate node and the adjacent node (communication module 520). Content-processing system 518 can also include instructions for, in response to not verifying the content object (verification module 528), refraining from enabling the connection between the intermediate node and the adjacent node (communication module 520).

[0054] Data 530 can include any data that is required as input or that is generated as output by the methods and/or processes described in this disclosure. Specifically, data 530 can store at least: an interest; a content object; a name; a name that is an HSVLI that includes contiguous name components ordered from a most general level to a most specific level; a routable prefix or a name prefix that indicates one or more contiguous name components beginning from the most general level; an identifier; an identifier for a node; an identifier for a local, remote, connected, or adjacent node; a first data structure with entries mapping an identifier to one or more outgoing interfaces; a forwarding information base with entries mapping a name prefix to one or more outgoing interfaces; a routing update; a routing entry; an indicator of a connection or a link between two nodes; and a signature for a packet, including for an interest or a content object.

[0055] The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer-readable media now known or later developed.

[0056] The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium.

[0057] Furthermore, the methods and processes described above can be included in hardware modules. For example, the hardware modules can include, but are not limited to, application- specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and other programmable-logic devices now known or later developed. When the hardware modules are activated, the hardware modules perform the methods and processes included within the hardware modules.

[0058] The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims.