WO2014000252A1

WO2014000252A1 - Method for establishing a hierarchical transmission structure in a content centric network

Info

Publication number: WO2014000252A1
Application number: PCT/CN2012/077860
Authority: WO
Inventors: Yifan Yu
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2012-06-29
Filing date: 2012-06-29
Publication date: 2014-01-03
Anticipated expiration: 2014-12-29

Description

METHOD FOR ESTABLISHING A HIERARCHICAL TRANSMISSION STRUCTURE IN A CONTENT CENTRIC NETWORK

The present invention generally relates to data routing in a Content Centric Network or

CCN.

The concept of Content Centric Network (CCN) has been proposed by PARC (Palo Alto Research Center) and is considered as a promising candidate architecture for the future Internet.

CCN architectures have been disclosed for instance in documents US20090288163,

US20090287835, and US20090285209.

The different nodes of the CCN declare their interest in some content by sending an Interest packet with the name of the wanted content to other nodes of the CCN. Upon the reception of Interest packet, a node determines whether the content satisfying the interest is available. If so, the corresponding content is sent to the terminal which asked for the content or Interest packet owner in the terminology of CCN. Otherwise, the Interest packet is marked as pending in the receiving node and forwarded to a second node in the CCN based on the interest. After receiving content from the second node in response to the forwarded Interest packet, the node un-marks the Interest packet as pending and sends the content to the Interest packet owner.

A node of the CCN routes a packet based on the action corresponding to the condition as specified in the routing policy of the CCN. A node of the CCN comprises a routing table containing three main data structures: a base called FIB (Forwarding Information Base), a buffer memory called ContentStore, and a table called PIT (Pending Interest Table).

The FIB is used to forward Interest packets toward potential source(s) of matching data. It is similar to an IP (Internet Protocol) FIB except it allows for a list of outgoing faces rather than a single one. The term face is used to represent a node registered in the routing table. The ContentStore is similar as the buffer memory of an IP router. The PIT is used to keep track of Interest packets that have been forwarded upstream toward content source(s) so that returned data can be sent downstream to its requestor(s).

A user device asks for content by broadcasting an Interest packet. A node receiving the

Interest packet and having data that satisfies it can respond with a Data packet containing data related to the content. Data packet is transmitted only in response to an Interest packet.

Figu re 1 represents a CCN comprising four CCN routers A^ to A₄, and two IP routers and B₂. A CCN router A_rA₄ may create and update its routing table as explained below.

When a media repository next to router A^ is announcing that it can serve Interests matching the prefix Vparc.com/media/art', the router A^ hears this announcement and, in response, installs a local CCN FIB entry for the prefix'/parc. com/media/art' pointing at the face Iv^ where it heard the announcement. Then, router A^ packages the prefix 7parc.com/media/art' into a message called Interior Gateway Protocol Link-State Advertisement or IGP LSA which is flooded to all nodes of the CCN. Router A₃ receives the LSA message and adds in its routing table FIB a prefix entry for 7parc.com/media/art' pointing to the face A_{1 :} as represented in Figure 1 .

Then, when a repository M₂ adjacent to router A₂ announces prefixes 7parc.com/media' and 7parc.com/media/art', router A₂ floods aLSA message for these two prefixes.

When receiving the LSA message from router A₂, the FIB of router A₃ is updated to contain /parc.com/media' pointing at face A₂, and 7parc.com/media/art' pointing to faces and A₂, as represented in Figure 1 .

Then, if a user device adjacent to router A₃ expresses interest in index /parc.com/media/art/impressionisthistory.mp4, this interest will get forwarded to both routers and A₂, and routers and A₂ will each forward it to their adjacent repository M,, M₂.

CCN approach enables each node in the CCN to have a global knowledge of content distribution by flooding each LSA message in the entire CCN.

However, such an approach may lead to significant overhead in large scale CCNs where huge amount of media content to be shared among the nodes.

Thus a large part of the bandwidth available in a CCN is consumed by the LSA messages.

The consequence is that a small part of the processing capabilities of each CCN router is used to deal with the data packet relating to a media content.

With the increment of the CCNs size, where the amount of media content disseminated in the network is increasing as well as the number of nodes deployed in the network, the CCN spends more resource such as bandwidth and processing capacity to cope with the CCN control packets including especially the LSA messages. This may lead a deterioration of the performance of the CCN due to the lack of resource assigned to transmission of data packets relating to media contents.

It is an objective of the present invention to overcome disadvantages and/or make improvements in the prior art.

In that respect, the present invention relates to a method for establishing a hierarchical transmission structure for transmitting a control message relating to an electronic content in a content centric network comprising a plurality of nodes, the method comprising the following steps executed by a first node belonging to a first hierarchical level of the content centric network :

- receiving a control message relating to an electronic content stored in one of the other nodes of the content centric network,

- determining at least a second node to which the control message relating to an electronic content is to be transmitted to,

- if the second node belongs to a second hierarchical level of the content centric network, establishing a permanent link between the first node and the second node. The method of the invention enables the reduction of the resource consumption in a CCN by assigning more resource to the transmission of data packets relating to media contents instead of allowing more resource to the control messages such as LSA messages as it is the case in the prior art.

The method of the invention consists in organizing the CCN in a hierarchical structure or tree-structure and allowing the transmission of control messages such as LSA messages or Interest messages between nodes of the CCN belongings to different hierarchical levels or, between nodes belonging to a same branch of the tree-structure.

By transmitting the control messages along the hierarchy, the number of control messages exchanged within the network is reduced and so is the resource consumption.

According to a characteristic of the method of the invention, if the second node belongs to the first hierarchical level, the method further comprises the steps of :

- determining a value of a parameter representing a frequency of transmission of messages relating to an electronic content between the first node and the second node,

- comparing the determined value of the parameter representing the frequency of transmission of control messages relating to an electronic content with a threshold,

- if the value of the parameter representing the frequency of transmission of control messages relating to an electronic content is above the threshold, establishing a link between the first node and the second node.

Such a characteristic enables to dynamically establish a link between two nodes belonging to the same hierarchical level, or to another branch of the network. Thus it is possible to transmit control messages more efficiently in the CCN without increasing the resource consumption.

According to a characteristic of the method of the invention, if the value of the parameter representing the frequency of transmission of control messages relating to an electronic content is below the threshold, terminating the link established between the first node and the second node.

The link established between two nodes of the same hierarchical level can be terminated when there is no longer any transmission of control messages between the nodes or when the number of control messages exchanges between these two nodes is under a threshold.

This enables a optimal management of the resources in the CCN.

The invention also concerns a method for transmitting a control message relating to an electronic content in a hierarchical transmission structure of a content centric network comprising a plurality of nodes, the method comprising the following steps executed by a first node belonging to a first hierarchical level of the content centric network :

- receiving a control message relating to an electronic content stored in one of the other nodes of the content centric network, - determining at least a second node to which the control message relating to an electronic content is to be transmitted to,

if the second node belongs to a second hierarchical level of the content centric network, transmitting the control message to the second node.

Another object of the invention is a node intended for establishing a hierarchical transmission structure for transmitting a control message relating to a electronic content in a content centric network, the node belonging to a first hierarchical level of the content centric network and comprising means for :

- establishing a permanent link between the first node and the second node, when the second node belongs to a second hierarchical level of the content centric network.

Such a node is for example a router.

Finally, one object of the invention concerns a computer program, in particular a computer program on or in an information medium or memory, suitable for implementing the method object of the invention. This program can use any programming language, and be in the form of source code, binary code, or of code intermediate between source code and object code such as in a partially compiled form, or in any other desirable form for implementing the communication methods according to the invention.

The information medium may be any entity or device capable of storing the program. For example, the medium can comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a diskette (floppy disk) or a hard disk.

Moreover, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The programs according to the invention may in particular be downloaded from a network of Internet type.

The present system and method are explained in further detail, and by way of example, with reference to the accompanying drawings wherein:

FIG. 1 represents a content centric network according to the prior art,

FIG. 2 represents a content centric network CCN in which the method of the invention is implemented,

FIG. 3 represents the steps executed by the different nodes 10, 1 10-1 12 and 120-124 of the content centric network CCN in order to establish the tree-structure,

FIG. 4 represents the steps executed by the nodes of the network when a LSA message is transmitted in the content centric network CCN, FIG. 5 represents a node of the content centric network CCN intended to execute the steps of the methods of the invention.

Figu re 2 represents a content centric network CCN in which the method of the invention is implemented.

The content centric network CCN comprises a plurality of nodes 10, 1 10-1 12 and 120-

124.

Each nodes 10, 1 10-1 12 and 120-124 of the content centric network CCN comprises a routing table containing three main data structures: a base called FIB (Forwarding Information Base), a buffer memory called ContentStore, and a table called PIT (Pending Interest Table).

The nodes 10, 1 10-1 12 and 120-124 form a hierarchical or tree-structure. The node 10 constitutes a first hierarchical level of the hierarchical structure and the root of the tree- structure.

The nodes 1 10-1 12 constitute a second hierarchical level of the hierarchical structure. The nodes 120-124 constitute a third hierarchical level of the hierarchical structure and the leaves of the tree-structure.

The content centric network CCN may comprise as many hierarchical levels as necessary.

The links established between the nodes belonging to the tree-structure are represented by continuous lines on figure 2. The links established between the different nodes 10, 1 10-1 12 and 120-124 of the tree-structure are physical connections between the nodes but logical paths. These are permanent links.

Dynamic links can be established between nodes belonging to different hierarchical levels or to different ranches of the tree-structure. Such dynamic links, represented by dotted lines on figure 2 are established between nodes 121 and 1 1 1 , nodes 121 and 122 or between nodes 123 and 124.

In an embodiment of the invention dynamical links can be established between a node of the content centric network CCN and a node belonging to another content centric network.

Figu re 3 represents the steps executed by the different nodes 10, 1 10-1 12 and 120- 124 of the content centric network CCN in order to establish the tree-structure. The steps are described for the branch constituted by the nodes 122, 1 1 1 and 1 1 . These steps are also executed in the other branches of the content centric network CCN.

In a step E1 , the node 122 receives a message from a media repository (not represented on the figures) announcing that it can serve Interests matching the prefix 7parc.com/media/art'. Upon reception of this message, the node 122 installs an entry in its FIB for the prefix7parc.com/media/art' pointing to the media repository where it heard the announcement.

In a step E2, the node 122 determines using a routing table at least a second node to which the LSA message is to be transmitted to. The second node is usually a neighbor node, separated from the node 122 by a hop. For example, nodes 123, 121 and 1 1 1 are the neighbor nodes of node 122.

Among those neighbor nodes 123, 121 and 1 1 1 , the node 122 determines which one belongs to a different hierarchical level in the content centric network CCN in a step E3. For example this information is store in the routing table of the node 122.

The result of the determination executed during step E3 is the node 1 1 1 which belong to a different hierarchical level than the node 122.

Then, in a step E4, the node 122 packages the prefix 7parc.com/media/art' into a LSA message LSA1 which is transmitted only to the node 1 1 1 .

In a step E5, the node 1 1 1 receives the message LSA1 . The reception of the message LSA1 triggers the execution of steps E1 to E3 by the node 1 1 1 .

In the step E1 , the node 1 1 1 installs an entry in its FIB for the prefix7parc.com/media/art' pointing to the media repository where it heard the announcement.

In a step E2, the node 1 1 1 determines using a routing table at least a second node to which the LSA message LSA1 is to be transmitted to. The second node is usually a neighbor node, separated from the node 122 by a hop. For example, nodes 121 , 122, 123 and 10 are the neighbor nodes of node 122.

Among those neighbor nodes121 , 122, 123 and 10, the node 1 1 1 determines which one belongs to a different hierarchical level in the content centric network CCN in a step E3.

The result of the determination executed during step E3 is the node 10 which belong to a higher hierarchical level than the node 1 1 1 .

Then, in a step E4, the node 1 1 1 packages the prefix 7parc.com/media/art' into a LSA message LSA2 which is transmitted only to the node 10.

In a step E6, executed after step E3, the node 1 1 1 determines for each node which does not belong to a different hierarchical level in the tree-structure or to the same branch of the tree-structure, i.e. for node 121 , a value of a parameter representing a frequency of transmission of messages comprising data relating to an electronic content between the node 1 1 1 and the node 121 .

In a step E7, the node 1 1 1 compares the determined value of the parameter representing the frequency of transmission of messages relating to an electronic content with a threshold.

In a step E8, if the value of the parameter representing the frequency of transmission of messages relating to an electronic content is above the threshold, the node 1 1 1 establishes a dynamic link with the node 121 .

In a step E9, the node 1 1 1 packages the prefix 7parc.com/media/art' into a LSA message LSA3 which is transmitted only to the node 121 . When the value of the parameter representing the frequency of transmission of messages relating to an electronic content between the node 1 1 1 and the node 121 is below the threshold, the node 1 1 1 terminates the dynamic link established between the node 1 1 1 and the node 121 .

The dynamic link established between the node 1 1 1 and the node 121 can be an asymmetric link, i.e. it is used to transmits messages from the node 1 1 1 to the node 121 or symmetric, i.e. allows a bidirectional transmission between the node 1 1 1 and the node 121 .

Figu re 4 represents the steps executed by the nodes of the network when a LSA message is transmitted in the content centric network CCN. The steps are described for the branch constituted by the nodes 122, 1 1 1 and 1 1 . These steps are also executed in the other branches of the content centric network CCN.

The hierarchical structure or tree-structure of the content centric network CCN is either established by running the method described in reference to figure 3 or the hierarchical structure is predefined during the deployment of the content centric network CCN. The same goes for the dynamical links established between different nodes of the content centric network CCN. These dynamic links can be established by running the method described in reference to figure 3 or predefined during the deployment of the content centric network CCN.

In a step G1 , the node 122 receives a message from a media repository (not represented on the figures) announcing that it can serve Interests matching the prefix 7parc.com/media/art'. Upon reception of this message, the node 122 installs an entry in its FIB for the prefix7parc.com/media/art' pointing to the media repository where it heard the announcement.

In a step G2, the node 122 packages the prefix 7parc.com/media/art' into a LSA message LSA1 which is transmitted only to the node 1 1 1 which is its parent node in the tree-structure if the content centric network CCN.

In a step G3, the node 1 1 1 receives the message LSA1

In the step G4, the node 1 1 1 installs an entry in its FIB for the prefix7parc.com/media/art' pointing to the media repository where it heard the announcement.

In a step G5, the node 1 1 1 packages the prefix 7parc.com/media/art' into a LSA message LSA2 which is transmitted only to the node 10 which is the parent node of the node 1 1 1 in the hierarchy of the content centric network CCN.

In a step G6, the node 1 1 1 packages the prefix 7parc.com/media/art' into a LSA message LSA3 which is transmitted only to the node 121 , which is the node connected to the node 1 1 1 through a dynamic link.

In this method, a LSA message is transmitted in the tree-structure of the content centric network CCN, and thus to a limited number of nodes, limiting the amount of LSA messages exchanged in the content centric network CCN.

In an embodiment of the method of the invention, when the node 10 receives the LSA message LSA2, it can transmit it to another content centric network distinct from the content centric network CCN through a dynamic link established with a node of the other content centric network. When the hierarchical structure of the content centric network CCN is established, Interest packets comprising the name of a wanted media content are transmitted through the hierarchical structure of ten content centric network CCN.

When the node 122 receives an Interest packet comprising the name a media content, the node 122 looks up its FIB with the name of the media content comprised in the Interest packet.

If there is not entry matching the media content name in the FIB of the node 122, the Interest packet is transmitted only to the node 1 1 1 which is its parent node in the tree-structure if the content centric network CCN.

Upon reception of the Interest packet, the node 1 1 1 looks up its FIB with the name of the media content comprised in the Interest packet.

If there is not entry matching the media content name in the FIB of the node 1 1 1 , the Interest packet is transmitted only to the node 10 which is the parent node of the node 1 1 1 in the hierarchy of the content centric network CCN.

Upon reception of the Interest packet, the node 10 looks up its FIB with the name of the media content comprised in the Interest packet.

If there is not entry matching the media content name in the FIB of the node 10, the Interest packet is either discarded or transmitted only to another content centric network through a dynamic link established between the node 10 and a node of this other content centric network..

In this method, an Interest packet is transmitted in the tree-structure of the content centric network CCN, and thus to a limited number of nodes, limiting the amount of Interest packets exchanged in the content centric network CCN.

Figu re 5 represents a node of the content centric network CCN intended to execute the steps of the methods of the invention.

The node 122 means 20 for receiving a message from a media repository (not represented on the figures) announcing that it can serve Interests matching the prefix 7parc.com/media/art'. Connected to these receiving means 20, the node 122 comprises a FIB in which it installs an entry for the prefix7parc.com/media/art' pointing to the media repository where it heard the announcement.

Connected to the FIB, the node 122 comprises means 21 for determining using a routing table RT at least a second node to which the LSA message is to be transmitted to

The node 122 comprises means 22 for packaging the prefix 7parc.com/media/art' into a LSA message LSA1 which is transmitted only to the node 1 1 1 by transmitting means 23. The packaging means 22 are connected to the determining means 21 and the transmitting means 23.

The node 122 comprises means 24 for determining for each node which does not belong to a different hierarchical level in the tree-structure or to the same branch of the tree- structure a value of a parameter representing a frequency of transmission of messages comprising data relating to an electronic content between the node 122 and the node 1 1 1 . The determining means 24 are connected to the transmitting means 23. The node 122 comprises means 25 for comparing the determined value of the parameter representing the frequency of transmission of messages relating to an electronic content with a threshold, connected to the determining means 24.

When the value of the parameter representing the frequency of transmission of messages relating to an electronic content is above the threshold, the node 122 establishes a dynamic link with the node 1 1 1 . In order to do so, the node 122 comprises means 26 for establishing a dynamic link connected to the comparing means 25.

Claims

1 . A method for establishing a hierarchical transmission structure for transmitting a control message relating to an electronic content in a content centric network comprising a plurality of nodes, the method comprising the following steps executed by a first node belonging to a first hierarchical level of the content centric network :

- if the second node belongs to a second hierarchical level of the content centric network, establishing a permanent link between the first node and the second node.

2. The method of claim 1 , wherein if the second node belongs to the first hierarchical level, the method further comprises the steps of :

3. The method of claim 2, wherein If the value of the parameter representing the frequency of transmission of control messages relating to an electronic content is below the threshold, terminating the link established between the first node and the second node.

4. A method for transmitting a control message relating to an electronic content in a hierarchical transmission structure of a content centric network comprising a plurality of nodes, the method comprising the following steps executed by a first node belonging to a first hierarchical level of the content centric network :

- if the second node belongs to a second hierarchical level of the content centric network, transmitting the control message to the second node.

5. Node intended for establishing a hierarchical transmission structure for transmitting a control message relating to a electronic content in a content centric network, the node belonging to a first hierarchical level of the content centric network and comprising means for :

6. A computer program characterized in that it comprises program code instructions for the implementation of the steps of the method for establishing a hierarchical structure for transmitting a control message relating to an electronic content in a content centric network as claimed in claim 1 when the program is executed by a processor.