Ordered-element naming for name-based packet forwarding

A name-based content-forwarding system generates an ordered-element name for a content item, and can process an interest to identify and perform an action that satisfies the interest. To generate the ordered-element name, the system generates one or more fixed-length elements for a content item, such that each fixed-length element of the ordered-element name is mapped to the content item or to a context associated with the content item. The system then generates the ordered-element name to include the one or more fixed-length elements so that the name elements are ordered from a highest matching priority to a lowest matching priority. The system can also generate a packet that includes the ordered-element name for the content item, and sends the packet to a target location that corresponds to the ordered-element name.

BACKGROUND

Field

This disclosure is generally related to routers. More specifically, this disclosure is related to using an ordered-element name, which includes fixed-length elements, to forward an interest for a content item.

Related Art

The proliferation of the Internet and mobile-related Internet services continue to fuel revolutionary changes in the network industry. Today, a significant number of information exchanges, from online movie viewing to daily news delivery, retail sales, and instant messaging, are conducted online, and oftentimes on a mobile computing device. An increasing number of Internet applications are also becoming mobile, while the current Internet operates on a largely location-based addressing scheme. The two most ubiquitous protocols, the Internet Protocol (IP) and Ethernet protocol, are both based on location-based addresses. That is, a consumer of content can only receive the content by explicitly requesting the content from an address (e.g., IP address or Ethernet media access control (MAC) address) closely associated with a physical object or location. This restrictive addressing scheme is becoming progressively inadequate for meeting the ever-changing network demands.

In general, a network device, such as an IP router or Ethernet switch, receives a packet at one of its input ports (e.g., a network interface). The device then performs a lookup to identify an output port to which the packet should be forwarded based on the packet's destination address. An IP router typically uses a longest-prefix-match lookup engine to process an IP address tied to a physical location, whereas an Ethernet switch uses an exact-match lookup engine to process a MAC address tied to a physical device. These devices are not adapted to process a packet based on a name for a piece of content.

SUMMARY

One embodiment provides a name-generating system that generates an ordered-element name for a content item. During operation, the system obtains name-generating information associated with the content item, and generates one or more fixed-length elements for the content item. Each fixed-length element of the ordered-element name is mapped to the content item or to a context associated with the content item. The system determines an ordering for the fixed-length elements, which orders the one or more fixed-length elements from a highest matching priority to a lowest matching priority. The system then generates an ordered-element name, for the content item, to include the one or more fixed-length elements in the determined ordering.

In some embodiments, the system determines the ordering by determining a matching priority for a respective fixed-length element, such that a matching priority for a respective fixed-length element is based on the corresponding name-generating information. The system then determines the ordering, for the one or more fixed-length elements, from a highest matching priority to a lowest matching priority.

In some embodiments, the context mapped to by the fixed-length element is associated with one or more of: a group of data to which the content item belongs; an entity associated with an interest packet for the content item; an entity which stores the content item; and an entity which generates the content item.

In some embodiments, the name-generating information includes one or more of: an ordered-element name associated with the content item, hierarchically structured variable-length identifier (HSVLI) associated with the content item, a filename associated with the content item, or structured information for the content item. The name-generating information can also include a location identifier, such as a universal resource identifier (URI) for the content item, and/or domain name system (DNS) information associated with the content item.

In some variations, the name-generating information can include information related to the content item. This name-generating information can include a timestamp associated with the content item, a location associated with the content item, an entity associated with the content item, a portion of the content item, data included in the content item, a keyword associated with content of the content item, a keyword for a category associated with the content item, and/or a keyword for an organization associated with the content item.

In some variations, the name-generating information can include information related to a content producer, creator, publisher or owner of the content item, and/or can include information related the content requester, consumer or user. The name-generating information can also include information related a physical environment, a runtime environment, information obtained from a user, or a randomly generated number.

In some embodiments, the ordered-element name includes a set of flags for a respective element. Further, the set of flags can include a termination flag, a non-terminal flag, and/or an exclude flag. When the termination flag is set for a corresponding fixed-length element, the flag indicates that a successful exact-match lookup for the corresponding element satisfies a lookup for the content item. When the non-terminal flag is set for a corresponding fixed-length element, the non-terminal flag indicates that an exact-match lookup for the corresponding fixed-length elements identifies routing information for the content item, but does not satisfy an exact-match lookup for the content item.

When the exclude flag is set for a corresponding fixed-length element and an exact-match is identified for the corresponding fixed-length element, the exclude flag indicates that the ordered-element name does not satisfy a match even if a successful match is identified for other fixed-length elements of the ordered-element names.

In some embodiments, the ordered-element name also includes metadata associated with the content item. The metadata can include a content type, data-version information, data-format information.

In some variations, the metadata can also include author-related information that identifies an entity which generated the content item, and/or authentication information that authenticates the entity which generated the content item. The metadata can include content author information, name-generator information.

In some variations, the metadata can also include encryption information that indicates an encryption technique used to encrypt the content item, a version identifier for the content item, and/or a format identifier for the content item.

In some variations, the metadata can include contextual information related for the content item. This metadata can include network status information, an error code, time information, location information, user-behavior information, and security-related information.

In some embodiments, the ordered-element name also includes a set of attribute fields indicating attributes used to generate the ordered-element name. The set of attribute fields indicate one or more of: context information associated with the content item; a filename for the content item; metadata associated with the content item; and a hierarchically structured variable-length identifier (HSVLI) for the content item.

In some embodiments, to generate a fixed-length element, the system can derive a unique fixed-length identifier using a predetermined function that takes as input at least one attribute of the content item, compute a hash using the attribute of the content item, and/or compute a hash based on at least a portion of the content item.

In some embodiments, the system can compute the hash using a predetermined hash function to compute the hash, using the predetermined hash function and a secret salt to compute a salted hash, and/or using a cryptographic function and a secret key to produce a fixed-length encrypted value from the hash or the salted hash.

One embodiment provides a packet-generating system that generates a packet associated with an ordered-element name. During operation, the system generates an ordered-element name for a content item. The ordered-element name includes one or more fixed-length elements ordered from a highest priority to a lowest priority, such that a respective fixed-length element is mapped to the content item or to a context associated with the content item. The system can generate a packet that includes the ordered-element name for the content item. The system determines a packet type for the packet, and determines a target location for the packet based on the ordered-element name. The system then sends the packet to the determined target location.

In some embodiments, the target location can include a data repository within the local computing device, an application executed by the local computing device, a remote computing device, and/or an application executed by the remote computing device.

In some embodiments, the context mapped to by the fixed-length element is associated with a group of data to which the content item belongs, an entity associated with an interest packet for the content item, an entity which stores the content item, and/or an entity which generates the content item.

In some embodiments, the packet type is a data packet that includes the content item, such that the ordered-element name facilitates matching an interest for the content item to the data packet.

In some embodiments, the packet type is an interest packet that includes an interest for the content item, such that the interest indicates the ordered-element name to facilitate forwarding the interest to a remote computing device that satisfies the interest for the content item.

In some embodiments the packet type is a control packet, which facilitates advertising the content item to one or more remote devices.

In some embodiments, the system generates the interest packet to include reverse-path information that is used by a remote computing device to send a data packet that includes the content item to the local computing device.

In some embodiments, the system generates the ordered-element name to include a set of flags that facilitate processing the fixed-length elements of the ordered-element name. The set of flags can include a termination flag, a non-terminal flag, and/or an exclude flag.

In some embodiments, the interest packet also includes data associated with the interest.

In some embodiments the system maintains a data repository, which facilitates determining when a data packet needs to be sent to a remote device.

In some variations, the data repository includes a forwarding information base (FIB), which maps a fixed-length element to one or more remote devices.

In some variations, the data repository includes a pending interest table (PIT), which maps a respective fixed-length element of an interest packet to the interest packet.

In some embodiments, while determining the target location, the system performs an exact-match lookup operation on the FIB, based on the ordered-element name, to identify a remote computing device. Then, to send the packet to the target location, the system sends the interest packet to the identified remote computing device.

In some embodiments, the system stores the interest packet in the PIT. Then, in response to receiving the content item from the remote computing device, the system removes the interest packet from the PIT.

In some embodiments, the system maintains a repository, which maps a respective packet to one or more remote devices, to keep track of when a packet has been sent to a remote device.

One embodiment provides a packet-processing system, which processes a packet to identify and perform an action necessary for processing the packet. During operation, the system receives a packet which includes an ordered-element name for a content item. The ordered-element name includes one or more fixed-length elements ordered from a highest priority to a lowest priority, such that a respective fixed-length element is mapped to the content item or to a context associated with the content item. The system determines a packet type for the received packet, and determines a packet-processing operation for the packet, based on the packet's ordered element name and/or packet type. The system then performs the packet-processing operation to process the received packet.

In some embodiments, while determining the packet-processing operation, the system determines a target packet-processing operation corresponding to the packet type. The system then performs a target-device-lookup operation, based on the packet type, to identify a target computing device that is to perform the target packet-processing operation.

In some embodiments, the target-device-lookup operation involves one or more of: performing an exact-match lookup operation based on the packet type; performing an exact-match lookup operation based on the ordered-element name; performing a wildcard-lookup operation based on the packet type; and performing a wildcard-lookup operation based on the ordered-element name.

In some embodiments, the target computing device is a remote computing device. Also, while performing the packet-processing operation, the system forwards the packet to the remote computing device. The system can also store the packet, such as an interest packet, in a local repository which maps a respective fixed-length element of the packet to the packet.

In some embodiments, the target computing device is the local computing device. Also, while performing the packet-processing operation, the system obtains a stored packet from a local repository, such that packet corresponds to the ordered-element name. The system then sends the stored packet to a remote computing device from which the local computing device received the original packet.

In some embodiments, the target computing device is the local computing device. Also, while performing the packet-processing operation, the system generates a packet based on information from the received packet, and sends the generated packet to a remote computing device from which the local computing device received the original packet.

In some embodiments, while generating the packet, the system determines data-generating parameters based on a fixed-length element of the original packet's ordered-element name, an attribute indicated by the ordered-element name, metadata indicated by the original packet or the ordered-element name, and/or a data object stored in the original packet. Further, the system can generate the response packet based on the determined data-generating parameters.

In some embodiments, the target computing device is the local computing device. Also, while performing the packet-processing operation, the system provides the packet to an application executing on the computing device to determine an application-specific operation for processing the packet.

In some embodiments, the packet corresponds to an interest packet, and while processing the interest packet, the system performs an exact-match lookup operation on a forwarding information base (FIB) to identify a target computing device that satisfies the interest for the content item. The system can also store the interest packet in a pending interest table (PIT), which maps a respective fixed-length element of the interest packet to the interest packet. For example, the target computing device may correspond to a remote computing device, and the packet-processing operation may involve forwarding the interest packet to the remote computing device. Then, in response to receiving the content item from the remote computing device, the system removes the interest packet from the PIT.

One embodiment provides a content-advertising system, which advertises the presence of data to other computing devices. During operation, the system detects a first content item to advertise to other computing devices, and generates an advertisement for the first content item. The advertisement indicates one or more of the fixed-length elements to advertise the presence of the first content item in a local repository. The system then sends the advertisement to one or more neighboring nodes of a computer network.

In some embodiments, the system receives an advertisement for a second content item, from a target entity that satisfies an interest in the second content item. The system then determines forwarding information for the target entity, and adds the fixed-length elements of the received advertisement into a forwarding information base (FIB). The FIB maps a respective fixed-length element to the forwarding information associated with the target entity.

In some embodiments, the content item can include a content item stored within a local repository, a content item that is to be generated by a local computing device, or a content item that is hosted by a remote computing device.

DETAILED DESCRIPTION

Overview

Embodiments of the present invention provide a system of network devices that facilitate disseminating and routing data packets across a computer network using ordered-element names. The ordered-element name includes one or more fixed-length elements, ordered based on a matching priority for the individual elements. In some embodiments, the network devices that process data packets can match a fixed-length element of the ordered-element name, based on their ordering, to a content item or to another network device that may be able to obtain the content item. The network devices that use these ordered-element names can include a content producer or a content consumer (e.g., a personal computing device), a wireless access point, a proxy server, a network firewall, and/or a network router.

For example, an end-host device can generate a an ordered-element name for a content item by deriving multiple fixed-length elements that can be used by an exact-match engine, and orders these elements to form an ordered-element name. The end-host device can derive these fixed-length elements from the content item's attributes (e.g., from the content item's name, author, subject, etc.), or from the content item itself (e.g., to form a checksum value). A router can use exact-match switching equipment, such as Ethernet switches, to forward packets based on the ordered-element name for the content item.

The end-host device can include a desktop computer, a smartphone, a computer tablet, a laptop computer, a wearable computing device (e.g., a watche), an embedded computing device, a smart appliance, etc. The end-host device can communicate and request data by generating and disseminating interest packets via a computer network. These interest packets are similar to the data packets, whose payload can include an ordered-element name describing the data that the end-host device is interested in. The interest packet's payload can also include additional information that can be used to identify the data that is being requested.

In some embodiments, the data of interest may not exist yet. The ordered-element name contained in an interest packet can be used to identify an existing data item, as well as to guide the interest packet to a network location where a copy of the data item may reside or may be generated.

In some embodiments, a network device can receive an interest packet via a computer network, and processes the interest packet, for example, to forward the interest packet to another device, store the interest packet, modify the packet, or discard the interest packet. Also, if the network device has a stored copy of the data item named in the interest packet, the device can respond to the interest packet by generating a data packet that includes the data item, and sending this data packet to the network device from which it received the interest packet. When the network device performs a lookup operation using an ordered-element name, the device can identify a match without requiring an exact match between two ordered-element names. A match is identified when a subset of elements in the ordered-element names are equal.

In some embodiments, a network device can generate and disseminate advertisement packets to other devices in the network, such that an advertisement packet indicates a data item that resides locally and/or in another network device. The advertisement packet can use an ordered-element name (or a set of unordered fixed-length elements) to identify the content item, which allows other network devices to perform a lookup using any of the name elements of the ordered-element name. An advertisement packet does not need to explicitly advertise a unique data packet or elements of the ordered-element name of a packet. For example, an advertisement can indicate a set of name elements for groups of data. Interest packets oftentimes include at least some group-identifying name elements that have been advertised, and network devices can use these group-identifying name elements to forward these interest packets by matching these name elements to one or more of the advertised fixed-length elements.

One embodiment provides a device that converts named data into a set of ordered-element named packets. The device can use a component or portion of the original name and/or metadata of the named data to generate ordered-element names for one or more ordered-element data packets. In some embodiments, the original name can include any name that indicates key words or attributes for the named data. For example, the original name can include a hierarchically structured variable-length identifier (HSVLI). The HSVLI identifies the content item, and comprises contiguous components ordered in a hierarchy from a most general level of the hierarchy to a most specific level of the hierarchy.

When the router device receives packets named with an ordered-element name, the router can process a packet based on its ordered-element name, for example, to forward the packet to another device, to store the packet, to modify the packet and forward them to another device, or to discard the packet. The ordered-element name, which is also referred to as a Structured Flat Name (SFN), includes a list of fixed-length elements ordered from a highest priority to a lowest priority.

The router device can include an exact-match lookup engine that can compare fixed-length addresses, such as an exact-match lookup engine for Ethernet MAC addresses. The device can process the ordered-element names using the lookup engine to effectively perform a longest-prefix-match lookup on hierarchically structured variable-length identifiers (HSVLIs), or on any type of structured name now known or later developed.

An HSVLI indicates a piece of content, is hierarchically structured, and includes one or more contiguous components ordered from a most general level to a most specific level. The length of a respective HSVLI is not fixed. Embodiments of the present invention involve converting the HSLVI, which includes one or more hierarchical components, into an ordered-element name (also referred to as a Structured Flat Name, or SFN) that can be processed using the exact-match lookup engine.

Techniques for performing an exact-match lookup using an HSVLI are also described in U.S. Pat. No. 8,243,735, entitled “System for Forwarding Packets with Hierarchically Structured Variable-Length Identifiers using an Exact-Match Lookup Engine,” by inventors Van L. Jacobson and James D. Thornton, the disclosure of which is incorporated by reference in its entirety herein.

Embodiments of the present invention can also be applied to content-centric networks (CCNs). Content-centric networks—where routing is based on interests rather than addresses—bring a new approach to content transport. Instead of having network traffic viewed at the application level as end-to-end conversations over which content travels, content is requested or returned based in part on the name given to it, and the network is responsible for routing content from the provider to the consumer. Content includes data that can be transported in the communication system, and can be any form of data such as text, images, video, and/or audio. A consumer and a provider can be a person at a computer or an automated process inside or outside the network. In such a network, a piece of content can refer to the entire content or a respective portion of the content. For example, a newspaper article might be represented by multiple pieces of content embodied as data packets. A piece of content can also be associated with metadata describing or augmenting the piece of content with information such as authentication data, creation date, content owner, etc.

In content-centric networks, unlike a conventional IP network, a packet may be identified by an HSVLI. For example, “abcd/bob/papers/ccn/news” could be the name of the content and identifies the corresponding packet(s); i.e., the “news” article from the “ccn” collection of papers for a user named “Bob” at the organization named “ABCD.”

To request a piece of content, a node expresses (e.g., disseminates, or broadcasts) an interest in that content by the content's name. An interest in a piece of content can be a query for the content according to the content's name or identifier. The content, if available in the network, is routed back to the node from any node that stores the content. The routing infrastructure intelligently propagates the interest to the prospective nodes that are likely to have the information, and then carries available content back along the path which the interest traversed.

As mentioned above, HSVLIs refer to content, and it is desirable that they be able to represent organizational structures for content and be at least partially meaningful to humans. An individual component of a HSVLI may have an arbitrary length, HSVLIs can have explicitly delimited components, can include any sequence of bytes, and are not limited to human-readable characters. A longest-prefix-match lookup is important in forwarding packets with HSVLIs. For example, an HSVLI indicating an interest in “/parc/home/solis” will match both “/parc/home/solis/alpha.txt” and “/parc/home/solis/beta.txt.” The longest match, in terms of the number of name components, is considered the best because it is the most specific.

FIG. 1illustrates an exemplary architecture of a network180, in accordance with an embodiment of the present invention. In this example, network180comprises nodes100-145. Each node in network180is coupled to one or more other nodes. Network connection185is an example of such a connection. InFIG. 1, network connections are shown as a solid line, but each line could also represent sub-networks or super-networks, which can couple one node to another node. Network180can be content-centric, a local network, a super-network, or a sub-network. Each of these networks can be interconnected so that a node in one network can reach a node in other networks. The network connection can be broadband, wireless, telephonic, satellite, or any type of network connection. A node can be a computer system, an end-point representing users, and/or a device that can generate interests or originate content.

In accordance with an embodiment of the present invention, a consumer can generate an interest in a piece of content, and can send that interest to a node in network180. The piece of content can be stored at a node in network180by a publisher or content provider, who can be located inside or outside the network. For example, inFIG. 1, the interest in a piece of content originates at node105. If the content is not available at the node, the interest flows to one or more nodes coupled to the first node. For example, inFIG. 1, the interest flows (interest flow150) to node115, which does not have the content available. Next, the interest flows (interest flow155) from node105to node125, which again does not have the content. The interest then flows (interest flow160) to node130, which does have the content available. The flow of the content then retraces its path in reverse (content flows165,170, and175) until it reaches node105, where the content is delivered. Other processes such as authentication can be involved in the flow of content.

In network180, any number of intermediate nodes (nodes100-145) in the path between a content holder (node130) and the interest generation node (node105) can participate in caching local copies of the content as it travels across the network. Caching reduces the network load for a second subscriber located in proximity to other subscribers by implicitly sharing access to the locally cached content.

In some embodiments, some network nodes can include a network forwarder system, such as network routers (e.g., nodes115and125), and optionally the network end-hosts (e.g., nodes105and130). The network forwarder system can include a forwarding information base (FIB) that stores individual name elements for a plurality of content items, and associates each name element with forwarding information associated with the corresponding content item. The network forwarder system forwards data packets and interest packets by using the FIB to perform an exact-match lookup operation against one or more fixed-length elements of the ordered-element name for a piece of content. The network forwarder system can also include a content repository (also referred to as a content store) that includes a plurality of content items, each of which is associated with one or more name elements that can uniquely identify the content item. If the network forwarder system receives an interest with a name element matching an entry in the content repository, the system can satisfy the interest by returning the corresponding content.

In some embodiments, some network nodes can include a network helper system that interfaces between applications and the network. For example, the network helper system can analyze network traffic (e.g., data packets and interest packets) to convert a structured name into an ordered-element name for the content. The network helper system can reside at certain network devices that provide access to content, such as interest generation node105or content holder130. The network helper system can also reside at network nodes that provide network access to end-host devices, such as intermediate nodes115or125that may implement a wireless access point or a home router.

Generating and Using Fixed-Length Elements for Forwarding Packets

Conventional packet forwarding is based on addresses assigned to nodes (or interfaces of nodes). For example, in Ethernet forwarding, a 48-bit MAC address of an Ethernet frame is used for an exact-match lookup in a forwarding table to determine the output port on the switch for the frame. However, such exact-match lookup is not suitable for forwarding packets based on a name for a content item (e.g., an HSVLI). First, the Ethernet-style exact-match lookup can only handle a fixed-length MAC address, whereas an ordered-element name for a content item can have a variable number of fixed-length “elements.” Second, Ethernet-style lookup engines can only perform exact-match lookups, whereas a name for the content item can vary in length. For example, an HSVLI can include several variable-length “components,” such that the hierarchical structure of an HSVLI calls for a longest-prefix-match of the HSVLI components to have a higher priority than other matching component subsets.

Ethernet switches are not designed to route packets across a large-scale network (such as the Internet) and are only intended to forward packets between small-scale networks (such as local-area networks). As a result, hierarchical routing is not a requirement in the original Ethernet protocol. However, packets that are to be forwarded based on their original name or HSVLIs may travel across networks of any size (such as the Internet), and name-based hierarchical routing is more suitable. For hierarchical routing, longest-prefix-match lookup is more efficient and scalable than exact-match lookup. In this disclosure, longest-prefix-match lookup refers to the process of performing a lookup based on attributes of a content item's original name or the content item itself. The system can perform the longest-prefix-match lookup, for example, based on an ordered-element name for an HSVLI, which returns a result matching an element that corresponds to the largest number of HSVLI components, from the highest to the lowest hierarchy of the HSVLI.

Recall that a piece of content can be associated with metadata describing or augmenting the piece of content with information such as authentication data, creation date, content owner, etc. In some embodiments, the system can generate one or more of the fixed-length elements from attributes of the piece of data, such as based on metadata, or based on the piece of content itself. For example, the system can use a predetermined function, such as a hash function, to generate a fixed-length element from one or more metadata elements. The system can also generate a fixed-length element by generating a checksum of the piece of content itself. Hence, by generating an ordered-element name based on the attributes of the piece of content, an end-host can disseminate an interest that uniquely identifies a desired version of the content.

In some embodiments, the network helper system can generate an interest that realizes network security. For example, a content producer's system can use a cryptographic operation to generate a name element for a piece of content, thus producing an encrypted name element. This way, only content consumers that know the necessary encryption key can generate an interest capable of accessing the content. If a content consumer generates an interest that includes the necessary name elements for reaching the content producer, but does not generate the encrypted name element for the content item, the content producer can ignore the interest as it does not match the interest for the content item. Also, the ordered-element names can be signed (e.g., using a digital certificate), which allows a content producer to authenticate a content consumer.

In some embodiments, the network helper system can generate an interest that realizes network privacy. For example, a network consumer can generate an interest for a content item so that the interest includes name elements for the content item (which are fixed-length keys), but does not include a structured name for the content item (e.g., an HSVLI that can identify the content by human-readable key words). Hence, the interest allow a content consumer to obtain content without identifying any given physical computer or location associated with a specific content producer, and without using human-readable names that can provide insight into the content being requested.

Network Helper System for Generating Ordered-Element Names

In embodiments of the present invention, the packet-forwarding system facilitates accessing content over a network using an ordered-element name for the content. The fixed-length elements of the ordered-element name can be derived from the content's original name (e.g., an HSVLI for the content), from content tags associated with the content, and/or from the content itself.

Some network devices can include a network helper system that analyzes network traffic, such as an interest for content, to convert a structured name into an ordered-element name for the content. The network helper system can reside at certain network devices that provide access to content, such as at an end-host device (e.g., a personal computing device) that generates content or an interest for content, or at an access point for end-host devices.

The ordered-element name can include one or more fixed-length elements that can be used to perform an exact-match lookup for determining forwarding information. The network helper system can use the ordered-element name to access the content locally (e.g., to satisfy an interest from a remote device), or to access the content from a remote device (e.g., by generating and disseminating an interest that indicates the ordered-element name). When the network helper system disseminates an interest across a network, network routers can use a fixed-length, exact-match lookup engine to forward the interest based on the ordered-element name, without having to first convert an HSVLI into the ordered-element name at run-time.

FIG. 2Apresents a flow chart illustrating a method for generating and disseminating an interest that includes an ordered-element name for a content item in accordance with an embodiment. During operation, the system obtains a request for a content item (operation202), and determines a structured name for the content item (operation204). The system then generates an ordered-element name for the content item, based on the structured name (operation206), and can generate a packet that includes an interest for the content item (operation208). The interest can include the ordered-element name that identifies the content item. To obtain the content item, the system disseminates the interest to one or more neighboring network nodes (operation210).

In some embodiments, the end-host device can include a content repository that stores a plurality of content items. The device can make these content items accessible from other remote devices by advertising its local collection to other neighboring nodes of the computer network. For example, the network-helper system can advertise the presence of a content item by providing one or more fixed-length elements for the content item to the neighboring network nodes, such as a router.

FIG. 2Bpresents a flow chart illustrating a method for synchronizing a content repository with other neighboring network nodes based on ordered-element names for content items in accordance with an embodiment. During operation, the system can detect a new content item in a local repository (operation252). For example, the content item can be a new object, such as a new file created or downloaded by a local user (e.g., a document, a picture, or a video), or can be an automatically generated object such as a system log file. The content item can also include a new or updated version of an existing object, such as a revised word-processing document, spreadsheet, etc.

The system can obtain a structured name for the content item (operation254), and generates one or more fixed-name elements for the content item based on the structured name and/or other attributes of the content item (operation256). The system then generates an advertisement that includes the fixed-length elements for the content item (operation258), and sends a packet that includes the advertisement to one or more neighboring network nodes (operation260).

The system can also process advertisements from other computing devices. For example, the system can receive an advertisement from a target entity that stores or generates a content item (e.g., satisfies an interest in the content item). The system then determines forwarding information for the target entity, and adds the fixed-length elements of the received advertisement into a forwarding information base (FIB). The FIB maps a respective fixed-length element to the forwarding information associated with the target entity.

In some embodiments, the network helper system can generate an ordered-element name for a content item to include a set of flags that guide a router while processing an interest for the content item, such as a termination flag, a non-terminal flag, and an exclude flag. When the termination flag is set for a corresponding fixed-length element, the flag indicates that a successful exact-match lookup for the corresponding element satisfies a lookup for the content item. For example, the system can set a termination flag for a given fixed-length element which is exclusively associated with the content item, which informs the router that a successful match for this element satisfies an exact match for the content item's data, or satisfies an exact match for the content item's original name (e.g., an HSVLI). Hence, when the system detects an exact match for an element whose termination flag is set, the system determines that the detected match is sufficient for satisfying the interest without processing other fixed-length elements.

When the non-terminal flag is set for a corresponding fixed-length element, the non-terminal flag indicates that an exact-match lookup for the corresponding fixed-length elements identifies routing information for the content item, but does not satisfy an exact-match lookup for the content item. However, when the exclude flag is set for a corresponding fixed-length element and an exact-match is identified for the corresponding fixed-length element, the exclude flag indicates that the ordered-element name does not satisfy a match even if a successful match is identified for other fixed-length elements of the ordered-element names.

As another example, the system can set the non-terminal flag for fixed-length elements that are not exclusively associated with the content item, such as fixed-length elements that were generated from information that facilitates forwarding an interest to a content producer or content holder. On the other hand, the system can set the exclude flag for fixed-length elements that are intended to indicate explicitly failed lookup operations. For example, the system can determine contextual information indicating when a packet is not to be forwarded to a target device or by a target device (e.g., by a firewall), and can set the exclude flag for fixed-length elements derived from this information.

FIG. 3presents a flow chart illustrating a method for generating an ordered-element name for a content item in accordance with an embodiment. During operation, the system generates one or more fixed-length elements for the structured name (operation302), and determines a set of flags for the individual fixed-length elements (operation304).

As mentioned above, the set of flags can include a termination flag, which when set, informs a router that a successful match for this element is sufficient for satisfying the interest. However, other flags are possible. For example, some flags can indicate a type for the fixed-length element, such as to indicate whether the element is derived from HSVLI components, from content tags, or from the content itself. Other flags can indicate a type of function that was used to generate the fixed-length element, such as to indicate a specific hash function. During operation304, the system can determine values for any type of flag, either now known or later developed, for controlling the exact-match lookup.

The system also determines an ordering for the fixed-length elements (operation306), for example, in parallel to or after generating the fixed-length elements and/or the set of flags. The system then generates an ordered-element name to include the one or more fixed-length elements, and the corresponding set of flags, in the determined ordering (operation308).

FIG. 4Aillustrates exemplary fixed-length name elements410generated from a content item406, an HSVLI402for content item406, content tags408in accordance with an embodiment. The system can use HSVLI402(e.g., “a/b/c”) to produce a set of prefixes404, which can be ordered from the most specific to the most general. For example, the system can produce prefixes404of HSVLI402to include “/a/b/c,” “/a/b,” and “/a.” The system can convert each of these prefixes into an n-bit fixed-length address, such as addresses412for a name element410.1. The system can also generate a set of k flags for each fixed-length address, and creates an n-bit fixed-length element by appending the n−k bit address and the k bit flags. For example, the system can append flags414after address412as shown inFIG. 4, or the system can append flags414before address412(not shown).

The most-specific prefix can be unique to a desired content item, and so the system assigns a highest priority to the address for the most-specific prefix, and enables the termination flag for this address (e.g., sets the termination flag to “1”). The system assigns a priority for other prefixes relative to their level of the HSVLI hierarchy, and orders these prefixes based on their priority (e.g., each prefix is ordered after other more-specific prefixes, and before other more-general prefixes).

The system can create a name element410.1by converting “/a/b/c” into n−k bit fixed-length address412with a value “f(/a/b/c),” and setting the value for the termination flag to “1” because the prefix corresponds to a most-specific level of the HSVLI hierarchy. Similarly, the system can create a name element410.2by converting “/a/b” into n−k bit fixed-length address with a value “f(/a/b),” and setting the value for the termination flag to “0” because the prefix does not correspond to a most-specific level of the HSVLI hierarchy. Note that “f(/a/b/c)” is a shorthand notation for the fixed-length address, which is derived from the prefix “/a/b/c” by entering the prefix into a predetermined function f( ) Each fixed-length address can be generated to include a predetermined number of bits (e.g., n−k bits). If function f( ) produces an output with less than n−k bits, the system can pad the result with a sufficient number of ‘0’ bits to produce a fixed-length address with n−k bits. As mentioned above, various methods can be used to derive a fixed-length address from a prefix, such as by using a hash function ho. Other prefixes inFIG. 6can be similarly converted to n−k bit fixed-length addresses.

The system can also generate a fixed-length address for content item406by computing a hash of content item406, such as a checksum (e.g., “cksum(File(/a/b/c))”). In some embodiments, the system may obtain the checksum of the file from a unique identifier for the file, which the system can use to disseminate an interest for the file. In some other embodiments, the system can generate the checksum to advertise the presence of content item406in a local repository to other network nodes. To compute the checksum from the file, the system can access the file using HSVLI402(e.g., to obtain “File(/a/b/c)”), and computes cksum(File(/a/b/c)). The system generates name element410.4by generating the address portion to include the computed checksum, and by generating the set of flags to have the termination flag enabled given that the checksum uniquely identifies content item406.

The system can generate checksum-based name element410.4to perform data de-duplication. For example, a user's office computer can include a picture on a work-related namespace (e.g., “/parc/solis/picture.jpg”), and the user's home computer can include the same picture on a personal namespace (e.g., “/solisfamily/pictures/nacho.jpg”). If these computers generate an ordered-element name that includes name element410.4, both of these computers can satisfy an interest for the picture based on the checksum, even though the HSVLIs for the two picture instances do not have matching HSVLI components.

In some embodiments, the system can also derive one or more fixed-length addresses from a set of content tags408. Content tags408can include tags that include metadata of content item406, such as keywords found in content item406or related to content item406, authentication data, a creation date, a content owner, etc. The system can generate various combinations of content tags408, and can sort these combinations from most specific to most general (e.g., based on the number of tags in a combination, and other values such as a weight indicating a significance or uniqueness of a given tag).

The system then generates a set of name elements for the tag combinations (e.g., name elements410.5,410.6, and410.7), and arranges them based on the ordering determined for the tag combinations. The system can generate a fixed-length address for a name element (e.g., name element410.6) by processing the corresponding tags using a predetermined function (e.g., using a hash function h( ) to compute h(“PARC”, “Solis”, “2013”)). In some embodiments, because the name elements derived from the content tags may not uniquely identify a content item, the system sets the corresponding termination flags to “0.” However, if the system generates a tag combination that includes a content tag that uniquely identifies content item406(e.g., a checksum value, or any other unique identifier for content item406), the system can set the corresponding termination flag to “1.”

In some embodiments, the system can generate an interest for content item406by appending the p individual n-bit fixed-length elements, based on their determined ordering, to form a p*n-bit ordered-element name.

In some embodiments, if the system is advertising content item406to other neighboring nodes of a computer network, the system can communicate one or more of the individual n−k bit fixed-length addresses to the neighboring nodes without having to communicate their corresponding flags414or the complete ordered-element name. The neighboring nodes can insert the fixed-length addresses for content item406in their local forwarding information base (FIB) in any order, and in association with their network interface to the local computing device. The neighboring node can include a router, which can perform an exact-match lookup for the ordered elements of an interest, using the FIB, to determining forwarding information for the interest.

FIG. 4Billustrates exemplary ordered-element name430that includes fixed-length elements in accordance with an embodiment. Ordered-element name430can include name elements432,432.2, and432.3that are derived from an HSVLI, can include a name element432.4that includes a checksum for a content item, and can include a set of name elements that are derived from content tags for a piece of content (e.g., name element432.p).

In some embodiments, the system can generate an ordered-element name to include both fixed-length elements, as well as HSVLI components that facilitate determining forwarding information at routing nodes that are not capable of processing the fixed-length elements.

In some embodiments, the ordered-element name can include metadata associated with the content item. The metadata can include author-related information that identifies an entity which generated the content item, and/or authentication information that authenticates the entity which generated the content item. The metadata can also include encryption information that indicates an encryption technique used to encrypt the content item, a version identifier for the content item, and/or a format identifier for the content item.

The ordered-element name can also include a set of attribute fields indicating attributes used to generate the ordered-element name. The set of attribute fields can indicate context information associated with the content item, a filename for the content item, metadata associated with the content item, and a hierarchically structured variable-length identifier (HSVLI) for the content item. The contextual information can include a timestamp, a group of data to which the content item belongs, an entity associated with an interest packet for the content item, an entity which stores the content item, and an entity which generates the content item.

FIG. 4Cillustrates exemplary ordered-element name that includes fixed-length elements460and HSVLI components in accordance with an embodiment. Ordered-element name460can include name elements462.2and462.3that include prefixes from an HSVLI, and can include name elements derived from an HSVLI (e.g., name element462.1), from a checksum for a content item (e.g., name element462.4), and from content tags for a piece of content (e.g., name element462.p).

Network Forwarder System for Processing an Interest

In some embodiments, a network forwarder system (e.g., a router) can route data and interest packets by performing an exact-match lookup operation against one or more fixed-length elements of the ordered-element name for a piece of content. The system can provide a cache, forwarding information base (e.g., forwarding tables), pending-interest tables, etc.

FIG. 5Apresents a flow chart illustrating a method for forwarding an interest based on an ordered-element name in accordance with an embodiment. During operation, the system obtains an interest that includes an ordered-element name for a content item (operation502). The system performs an exact-match lookup for one or more elements of the ordered-element name (operation504), and determines whether an exact-match exists (operation506). The system can process the individual elements in parallel, in a sequence, or in a combination of the two.

If the system determines that an exact-match exists for an element, the system obtains forwarding information for this element from the exact-match lookup (operation508). The system then forwards the interest using the obtained forwarding information (operation510).

In some embodiments, if the system determines at operation506that an exact-match does not exist, the system can perform a remedial action. For example, the system can store the interest in a pending interest table (PIT), which maps the various fixed-length element of the interest to the interest. Then, when the content item becomes available (e.g., in response to receiving the content item from a remote computing device), the system can remove the interest from the PIT. As another example, the system can ignore the interest to allow another network node to respond.

In some embodiments, a network device can include a content repository, which stores content items that can be accessed using a matching interest. The network device can include a router or firewall with a content cache, a personal computing device, a content server, or a server within a computer cluster. When the network device receives an interest, the network device can perform an exact-match lookup in the content repository for elements of the ordered-element name that have a termination flag enabled. If the content item is stored locally, the network device can return the content item from the local content repository, without having to perform an exact-match lookup for other elements of the ordered-element name.

FIG. 5Bpresents a flow chart illustrating a method for forwarding an interest based on an ordered-element name with termination flags in accordance with an embodiment. During operation, the system can obtain an interest that indicates an ordered-element name for a content item (operation552). The system can process the individual elements in parallel, in a sequence, or in a combination of the two. For example, the system can select an element from the ordered-element name (operation554), and performs an exact-match lookup using the selected element. Recall that the ordered-element name includes a set of elements that are ordered based on their priority. Hence, during operation554, the system can select the element based on the explicit ordering.

To perform the exact-match lookup, the system determines whether the selected element's termination flag is set (operation556). If so, the system performs an exact-match lookup operation in a content repository using the selected element (operation558), and determines whether an exact match exists (operation560). If an exact match exists, the system does not need to consider other elements of the ordered-element name, at which point the system obtains a content item associated with the selected element (operation562), and returns the obtained content item to the network node from which the system received the interest (operation564).

If the system determines at operation556that the selected element's termination flag is not set, or determines during operation560that an exact match does not exist in the content repository for the selected element, the system can proceed to process the element in accordance to the flags and priorities of the other elements. For example, the system may first determine whether there is an exact-match in the content repository for other lower-priority elements that have the termination flag set, and proceeds to process the selected element otherwise (not shown).

To process the selected element, the system can perform an exact-match lookup in a forwarding information base (FIB) using the selected element (operation566), and determines whether an exact match exists (operation568). If an exact match exists, the system obtains forwarding information for the element from the FIB (operation570), and forwards the interest using the forwarding information (operation572).

Recall that the system can process the fixed-length elements in parallel, or in a sequence. In some embodiments, the system may utilize a hardware-based exact-match lookup mechanism that can process up to n elements in parallel. Hence, the system may need to process some elements in a sequence when the ordered-element name includes more than n elements. During operation568, if an exact-match does not exist for the selected element (or for any of the n elements processed in parallel), the system proceeds to determine whether there are more elements to process (operation574).

If other elements remain to be processed, the system can return to operation554to select another element from the ordered-element name. If no more elements remain, the system has determined that an exact-match does not exist for the ordered-element name, and can perform a remedial action, such as to add the interest to the PIT, to ignore the interest, or to send a response message to the network node from which it received the interest.

In some embodiments, the system can receive a data packet that includes a content item that satisfies an interest stored in the local PIT. The data packet can include one or more fixed-length elements (e.g., the content item's ordered-element name), and the system searches the PIT using these fixed-length elements to determine whether a pending interest exists for the content item. If a pending interest does exist for the content item, the system determines a target entity for the content item, and forwards the data packet to the target entity. The system can search the PIT by performing an exact-match lookup through the PIT to identify an interest whose ordered-element name includes a fixed-length element that matches a fixed-length element of the data packet's ordered-element name. Also, in some embodiments, if the interest includes a set of termination flags for the fixed-length elements, the content item satisfies the interest if the interest has a termination flag set for the matching fixed-length element.

FIG. 6illustrates an exemplary apparatus600that facilitates obtaining a content item based on an ordered-element name for the content item in accordance with an embodiment. Apparatus600can comprise a plurality of modules which may communicate with one another via a wired or wireless communication channel. Apparatus600may be realized using one or more integrated circuits, and may include fewer or more modules than those shown inFIG. 6. Further, apparatus600may be integrated in a computer system, or realized as a separate device which is capable of communicating with other computer systems and/or devices. Specifically, apparatus600can comprise a communication module602, an interest-processing module604, an exact-match lookup module606, an interest-forwarding module608, a name-generating module610, and a repository-managing module612.

In some embodiments, communication module602can send and/or receive packets over a computer network, such as packets that include a content item or an interest for a content item. Interest-processing module604can determine forwarding information for the interest using an exact-match lookup for one or more of the fixed-length elements. Exact-match lookup module606can search, in a forwarding information base (FIB), for an exact match to a fixed-length element of the interest to obtain forwarding information. Interest-forwarding module608can select forwarding information for at least one fixed-length element for which an exact match is found.

Name-generating module610can convert a structured name into an ordered-element name, so that the ordered-element name includes fixed-length elements ordered from a highest-priority to a lowest-priority. Repository-managing module612can generate a repository-synchronization message for the content item, which indicates one or more of the fixed-length elements, and sends the repository-synchronization message to one or more neighboring nodes of a computer network to advertise the presence of the content item.

FIG. 7illustrates an exemplary computer system702that facilitates obtaining a content item based on an ordered-element name for the content item in accordance with an embodiment. Computer system702includes a processor704, a memory706, and a storage device708. Memory706can 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 system702can be coupled to a display device710, a keyboard712, and a pointing device714. Storage device708can store operating system716, packet-forwarding system718, and data726.

Packet-forwarding system718can include instructions, which when executed by computer system702, can cause computer system702to perform methods and/or processes described in this disclosure. Specifically, packet-forwarding system718may include instructions for sending and/or receiving packets over a computer network, such as packets that include a content item or an interest for a content item (communication module720). Further, packet-forwarding system718can include instructions for determining forwarding information for the interest using an exact-match lookup for one or more of the fixed-length elements (interest-processing module722).

Packet-forwarding system718can include instructions for searching, in a forwarding information base (FIB), for an exact match to a fixed-length element of the interest to obtain forwarding information (exact-match lookup module724). Packet-forwarding system718can also include instructions for selecting forwarding information for at least one fixed-length element for which an exact match is found (interest-forwarding module726).

Packet-forwarding system718can include instructions for converting a structured name into an ordered-element name, so that the ordered-element name includes fixed-length elements ordered from a highest-priority to a lowest-priority (name-generating module728). Packet-forwarding system718can also include instructions for generating a repository-synchronization message for the content item, which indicates one or more of the fixed-length elements, and sending the repository-synchronization message to one or more neighboring nodes of a computer network to advertise the presence of the content item (repository-managing module730).

Data726can 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, data726can store at least a content repository and/or a forwarding information base.