Method for optimizing the distribution of multicast content within a communication network implementing a plurality of network slices.

Abstract

Method for optimizing the distribution of multicast content within a communication network implementing a plurality of network slices. The invention relates to a method for optimizing the distribution of multicast content within a communication network implementing a plurality of network slices.Such a process comprises: - the determination (12), by a controller of said communication network, following the acquisition (11) of information representative of the fact that said multicast stream is to be duplicated on a plurality of said network slices, of a perimeter of said communication network, called the aggregation perimeter, comprising a plurality of routers included in at least one distribution tree of said multicast stream; - the transmission (13), by said controller, to at least one router of said aggregation perimeter, of at least one configuration instruction for said router so that, within said aggregation perimeter, said multicast stream is routed on only one of said network slices, called the transport slice. Abbreviated figure: Figure 1.

Description

Title of the invention: Method for optimizing the broadcasting of multicast content within a communication network implementing a plurality of network slices. Technical field

[0001] The field of the invention is that of communications within at least one communication network, and in particular that of value-added IP services. More specifically, the invention relates to the implementation of content distribution services according to a multicast transmission mode, in a communication network within which network slices are deployed. Prior art

[0002] The broadcasting of the same content to multiple users is a service commonly offered and implemented via current communication networks, for example in the context of the retransmission of cultural or sporting events (retransmission of a concert in a metaverse, retransmission of a live football match, etc.). On a technical level, the engineering of such broadcasting services is generally based on a transmission mode called "multicast" (sometimes also referred to as "multicasting" or "group broadcasting"). This mode is in fact particularly suited to group communication schemes, such as the broadcasting of content to several users or machines, or the implementation of videoconferencing type services between several users where each participant is in turn source or receiver.In IP (Internet Protocol) networks, the multicast transmission mode relies on the calculation, establishment and maintenance of distribution trees by a dynamic routing protocol, such as the PIM (Protocol Independent Multicast, RFC7761) protocol for example. A main objective of implementing such distribution trees is to reduce network load by avoiding as much as possible that multiple copies of the same content use the same network link.

[0003] Certain recent communication networks, in particular fifth generation mobile networks (5G), also offer the possibility for the operators who operate them to create and deploy different network slices on the same physical infrastructure.

[0004] A network slice can be defined as a partition of the network, such as a virtual private network (VPN) deployed on a fixed infrastructure, mobile infrastructure, or a combination of both.

[0005] The characteristics of a network slice are essentially expressed in terms of capacity (i.e. bandwidth), quality of service (e.g. latency, one-way transit time), security (e.g. preservation of the confidentiality of information transmitted within the slice), traffic isolation or availability. Thus, an operator has the possibility of configuring a plurality of network slices within a communication network, a slice or a group of slices being for example dedicated to providing particular services and / or meeting particular technical requirements, which presents undeniable advantages in terms of flexibility and adaptability when deploying new functionalities.

[0006] Conventionally, traffic that may be routed within a network slice is subject to authorization (also called access control) to use the paths established within the slice in question. Such authorization is typically based on the application of traffic classification rules, generally applied by a network access point within which the network slices are deployed. Such an access point is a node located at the edge of the network, for example deployed in front of client access or used to connect a network to other neighboring networks. For example, this access point may be located at the connection interface of a gateway (for example a packet gateway, or "Packet Gateway" in English, for the most recent generations - 4G, 5G - of mobile networks) which provides access to the Internet network.Such an access point may also be located at the connection interface of a mobile terminal (or “User Equipment” or UE in English) to the radio access network (or “Radio Access Network” or RAN in English), in particular so as to optimize the use of radio resources depending on the type of network slice and the profile of the traffic that it is likely to carry.

[0007] In this context, the 3GPP organization has defined different types of network slices, with specific characteristics, including in particular:

[0008] - a first type of network slices allowing a wide mobile service to be offered enhanced Mobile BroadBand (eMBB);

[0009] - a second type of network slices allowing a service to be offered within the framework of a (massive) deployment of the Internet of Things (mloT); and

[0010] - a third type of network slices allowing to offer a communication service Ultra Reliable Low Latency Communications (URLLC).

[0011] The choice of designing and deploying one or other of the types of network slice is conditioned by the nature of the traffic characteristic of the applications or services used or subscribed to by a user. For example, a so-called "immersive" service which uses augmented or virtual reality techniques is generally very demanding in terms of terms of latency and reliability of data exchanges: the use of URLLC type slices is therefore preferred for such an immersive service.

[0012] To access content broadcast in multicast on a communication network implementing such network slices, a receiver (mobile terminal, personal computer, television set) must be able to connect to one or more network slices, which on the one hand host the distribution tree along which the traffic will be routed from the source to all the receivers, and on the other hand have characteristics reflecting those of the broadcast service(s). For example, one network slice will be designed and sized (in terms of bandwidth, one-way transit time, etc.) to route traffic encoded by the source in high definition (HD), another slice to route traffic encoded by the source in standard definition (SD), etc.

[0013] The variety of such “multicast” slices must make it possible to switch the broadcast traffic from one slice to another according to several considerations such as a possible congestion phenomenon, the access capacities of the receivers to one or other of the slices, the nature of the broadcast service to which a receiver has subscribed, etc. Such considerations make it possible in particular to dynamically adjust the traffic classification rules which govern the access of the receivers to one or other of these slices.

[0014] The deployment of a plurality of slices capable of routing a multicast stream within a communication network nevertheless leads to situations where the same content is likely to be broadcast through several distribution trees implemented within distinct network slices of the communication network. In this case, copies of the same content may be required to use the same physical network link several times, which is far from optimal in terms of use of network resources.

[0015] There is therefore a need for a technique for better optimizing the distribution of multicast content within a communication network in which several network slices are deployed. Summary of the invention

[0016] The present invention makes it possible to propose a solution aimed at remedying certain drawbacks of the prior art. According to one aspect, the present invention relates to a method for optimizing the broadcasting of multicast content within a communication network implementing a plurality of network slices. In doing so, the resources of a network are then optimized. According to the general principle of the proposed invention, such a method comprises:

[0017] - the determination, by a controller of said communication network, following obtaining information representative of the fact that said multicast flow is to be duplicated on a plurality of said network slices, of a perimeter of said communication network, called aggregation perimeter, comprising a plurality of routers involved in the routing of multicast traffic within at least one distribution tree of said multicast flow;

[0018] - transmission, by said controller, to at least one router of said aggregation perimeter, of at least one configuration instruction of said router so that in said aggregation perimeter, said multicast flow is routed on only one of said network slices, called transport slice.

[0019] In this way, the routing of content broadcast according to the multicast transmission mode within a communication network implementing network slices is optimized, in the sense that the invention makes it possible to manage the use of network resources more efficiently by setting up a partial or complete aggregation of distribution trees of a multicast stream, which makes it possible to avoid the systematic replication of the same content (i.e. content having the same encoding characteristics, in particular) within different distribution trees deployed in a plurality of network slices.

[0020] In a particular embodiment, said configuration instructions are transmitted to at least all the routers of the aggregation perimeter located at the edge of said aggregation perimeter.

[0021] In this way, the routers which delimit the aggregation perimeter can control the routing of the multicast flow into and out of this perimeter and more precisely the replication of the same multicast flow.

[0022] One or more aggregation perimeters may be set up for a single multicast stream. In addition, separate aggregation perimeters may be defined for separate streams routed through a given network.

[0023] In a particular embodiment, said transmission is implemented to all the routers of said aggregation perimeter.

[0024] In this way, the routing of the flow can be controlled even in the case where new access routers come to connect to the routers of the aggregation perimeter via intermediate routers which are not on the periphery of said aggregation perimeter.

[0025] In a particular embodiment, said method comprises, upon receipt of said configuration instructions by a router of said aggregation perimeter, the storage, within a data structure of said router, of a correspondence between an identifier of said transport slice and an identifier of a network slice defined according to an initial configuration for the routing of said multicast flow via said router.

[0026] In this way, even when a multicast stream is redirected to the transport slice, the router keeps in memory the information of the original slice via which it was planned to route the multicast stream according to the initial configuration of the router.

[0027] In a particular embodiment, said identifier of said transport slice is included in said configuration instructions.

[0028] In this way, the information of the transport slice to be used to route a multicast flow is known and directly accessible to each router which receives such instructions.

[0029] In a particular embodiment, said transport slice is a slice specifically designed and sized for routing said multicast flow in said aggregation perimeter.

[0030] In this way, suitable network resources can be allocated for the implementation of a slice dedicated specifically to the transport of a multicast flow in an aggregation perimeter, the engineering of this slice being able in particular to be conditioned by the volume of traffic, its nature, the number of receivers, etc.

[0031] In a particular embodiment, said transport slice is selected by said controller from among the network slices provided for routing the multicast flow according to an initial configuration of the routers of the aggregation perimeter, called original slices.

[0032] In this way, already existing resources can be used for the implementation of the transport slice, without necessarily mobilizing new resources.

[0033] According to a particular characteristic of this embodiment, said transport slice selected by said controller satisfies in particular technical requirements associated with each of said original slices.

[0034] In this way, routing the multicast stream via the transport slice in the aggregation perimeter does not cause performance and / or quality of service degradation compared to routing via a network slice initially provided for this purpose.

[0035] In a particular embodiment, said aggregation perimeter comprises at least one input router through which said multicast flow enters said aggregation perimeter and at least one output router through which said multicast flow leaves the aggregation perimeter, and said at least one configuration instruction leads:

[0036] - said at least one input router to proceed with the routing of the multicast stream in using a distribution tree deployed in said transport slice rather than in at least one origin slice within which said multicast stream is routed upstream of said ingress router; and

[0037] - said at least one output router to carry out the routing of the multicast stream using at least one distribution tree deployed in said at least one origin slice, downstream of said output router.

[0038] In this way, the multicast flow can be switched back to its original slot at the output of this perimeter, making the operation of routing the multicast flow via the transport slot in the aggregation perimeter transparent for a receiver of said flow.

[0039] According to a particular characteristic of this embodiment, said aggregation perimeter comprises at least one intermediate router, located between said at least one input router and said at least one output router.

[0040] In a particular embodiment, said method comprises, upon receipt of said configuration instruction by said at least one router, the transmission, by said at least one router, according to a dynamic routing protocol, of a graft request message to a distribution tree of said multicast flow hosted in said transport slice, said graft request message comprising an identifier of said transport slice.

[0041] In this way, the transport slice identifier is propagated to all the routers contributing to the routing of the multicast flow, particularly within an aggregation perimeter.

[0042] According to a particular characteristic, said graft request message further comprises data representing an encoding of said multicast stream or representing an absence of encoding information of said multicast stream.

[0043] In this way, additional discriminating data is available making it possible to select a distribution tree to be used within the transport slice, in the case where several distribution trees, each associated with the routing of the multicast stream according to a particular encoding, are hosted within this slice.

[0044] In a particular embodiment:

[0045] - said at least one configuration instruction comprises data allowing to identify said at least one ingress router, said at least one egress router, and said at least one originating slice;

[0046] - said configuration instruction is transmitted only to said at least one router output; and

[0047] - upon receipt of said configuration instruction, said at least one configuration message graft request issued by said at least one output router further comprises said data making it possible to identify said at least one input router, said at least one output router, and said at least one originating slot.

[0048] In this way, via the classic mechanics of the dynamic multicast routing protocol according to which the graft request message sent by the egress router is propagated in the opposite direction to the routing direction of a multicast flow, each router in the distribution tree has data allowing it to determine its category (egress router, intermediate router, or ingress router) and to consequently operate differentiated processing in determining the network slices to which it must route the multicast flow.

[0049] In a particular embodiment, said dynamic routing protocol is the PIM protocol and said graft request message is a “far” type message according to said PIM protocol, adapted to include said identifier of said transport slice, said data representative of an encoding of said multicast stream when said data representative of an encoding of said multicast stream is available, and / or said data making it possible to identify said at least one input router, said at least one output router, and said at least one original slice.

[0050] In this way, the present invention is based on a dynamic routing protocol widely used for setting up multicast broadcasting services in an IP network. According to another aspect, the invention relates to a network controller type entity, suitable for implementing the method for optimizing the broadcasting of a multicast stream described above. Such an entity may of course have the various characteristics relating to the optimization method according to the invention, which may be combined or considered in isolation. Thus, the characteristics and advantages of this entity are the same as those of the optimization method and are not detailed further.

[0051] According to another aspect, the proposed technique also relates to a computer program product downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a microprocessor, comprising program code instructions for executing the optimization method previously described in any of its embodiments, when this method is executed on a computer.

[0052] The proposed technique also relates to a computer-readable recording medium on which is recorded a computer program comprising program code instructions for executing the steps of the method as described above, in any of its embodiments.

[0053] Such a recording medium may be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a USB key or a hard disk.

[0054] On the other hand, such a recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical cable or optically, by radio or by other means, so that the computer program it contains is executable remotely. The program according to the invention can in particular be downloaded over a network, for example the Internet.

[0055] The different embodiments mentioned above can be combined with each other for implementing the invention. Figures

[0056] Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and non-limiting example, and the appended drawings, among which:

[0057] [Fig-1] schematically presents the different stages of a process optimizing the distribution of multicast content within a communication network implementing a plurality of network slices, in a particular embodiment of the invention;

[0058] [Fig.2a] schematically illustrates the routing of a multicast flow within an aggregation perimeter of a communication network organized in slices, when the invention is not implemented;

[0059] [Fig.2b] schematically illustrates the routing of a multicast flow on a transport slice within an aggregation perimeter of a communication network, in a particular embodiment of the invention;

[0060] [Fig.3] illustrates an example of formalism of a new attribute of a “far” PIM type message, in a particular embodiment of the invention;

[0061] [Fig.4] describes a simplified architecture of a network controller for implementing the invention. Detailed description of the invention

[0062] The technique described below makes it possible to overcome some of the aforementioned drawbacks. This technique is called MASSINE (for “MAnagement of Swapping of flows among Slices In NEtworks”, in English).

[0063] The proposed technique makes it possible in particular to manage more efficiently the use of the resources of a network organized in slices, within which distribution trees are established and maintained to route multicast content broadcast by one or more sources. According to the general principle of the invention, this resource management is based more particularly on the detection of distribution trees that at least partly overlap, and on the establishment of a partial or complete aggregation of said trees.

[0064] It should be noted that the present technique can be implemented independently:

[0065] - the nature of the content broadcast by the sources;

[0066] - encoding capabilities possibly associated with the broadcasting of such content;

[0067] - access capabilities of the receiving terminals to the networks which support said multicast network slices;

[0068] - the nature of these networks (which may be fixed and / or mobile);

[0069] - engineering choices made with regard to design, deployment and exploitation of multicast network slices;

[0070] - protocols used to access content broadcast in multicast;

[0071] - procedures put in place between a network and a source (e.g. the contract between a content provider and the operator, or authentication or authorization procedures).

[0072] - mechanisms for producing network slices.

[0073] In all the figures of this document, elements and steps of the same nature are designated by the same numerical reference.

[0074] According to a first aspect, the present technique relates to a method for optimizing the broadcasting of a multicast stream within a communication network implementing network slices. Such a method is illustrated in relation to [Fig.l].

[0075] The method is more particularly implemented at the initiative of a communication network control device (more simply called controller or network controller in this document), when it is detected that, according to an initial configuration, a multicast stream emitted by a source to one or more receivers is to be routed or is currently routed on a plurality of network slices (i.e. at least two) on at least one part of the communication network. In other words, the controller detects that a multicast stream corresponding to the same content is currently duplicated or is to be duplicated on several network slices implemented on the same infrastructure.

[0076] Such detection can be carried out at the controller itself, for example on the basis of data received from various control devices deployed within the network (e.g. software probes). Alternatively or additionally, it can also be carried out at the level of one or more routers which, detecting for example that they themselves belong to distribution trees of the same content deployed on several distinct network slices, transmit this information to the controller, for example by means of notification messages based for example on the NETCONF protocol (Network configuration protocol), gNMI (gRPC Network Management Interface), etc.

[0077] In any event, the controller obtains, in a step 11, information representative of the fact that a multicast stream representative of the same content is to be duplicated and routed over a plurality of network slices of the communication network.

[0078] According to the proposed technique, when such a situation is detected, the controller determines, in a step 12 and on the basis of the information obtained, a perimeter of the communication network in which an aggregation operation can be implemented. By "aggregation" is meant here a control of the duplication of the multicast flow, aimed precisely at preventing this flow from being duplicated and transported within several network slices, in a given perimeter of the communication network, called the aggregation perimeter.

[0079] More particularly, such an aggregation perimeter is defined by a set of network equipment identified by the controller, typically routers, which are simultaneously included in distribution trees deployed on several network slices and used to transmit the multicast stream to a set of receivers having requested it, via the communication network.

[0080] In other words, the aggregation perimeter corresponds to an area of ​​the communication network formed by a set of routers, within which it has been detected that the same multicast flow is likely, according to an initial configuration of the routers in question, to be duplicated and routed over a plurality of network slices, which is not optimal in terms of use of network resources.

[0081] Once this aggregation perimeter has been determined by the controller, the latter transmits, in a step 13, at least one configuration instruction to at least one router of said aggregation perimeter. More particularly, as illustrated in [Fig. 2b], the reception of such a configuration instruction at one or more target routers results in a modification of the configuration of said target routers, so that in the aggregation perimeter, the multicast stream is routed on a single network slice, called transport slice, according to methods described later in various embodiments of the proposed technique. The example of [Fig. 2b] presents in this respect an RC communication network implementing three multicast network slices TRI, TR2 and TR3 used to route a multicast stream in the direction of the arrow DF. As illustrated in this [Fig.2b], in the PA aggregation perimeter comprising routers 3, 4, 5, 6 and 7, the multicast flow initially routed (i.e. duplicated) on each of the TRI, TR2 and TR3 slices (as illustrated by [Fig.2a], which shows the routing of the flow before implementation of the invention) is no longer carried except on slice 1, which acts as a transport slice.

[0082] In a particular embodiment, the transport slice is selected by the controller. It corresponds for example to one of the network slices forming part of the slices provided for routing the multicast flow according to the initial configuration of the routers of the aggregation perimeter. In this case, the controller selects, from among these slices that can be described as original slices, a network slice whose characteristics also satisfy those of all the other slices, or at the very least of a maximum of these slices. In other words, a slice that meets the technical requirements of the other network slices (e.g. in terms of latency, reliability of data exchanges, etc.) is selected as the transport slice, provided that such a slice exists. In this way, the use of the transport slice to route the traffic related to the multicast flow in the aggregation perimeter does not lead to a decrease in performance and / or quality of service compared to the situation in which the initial configuration - i.e. the routing in this perimeter of the multicast flow via the originally planned slices - would have been maintained. Other considerations relating to a current state of the network (e.g. the volume of traffic, its nature, the number of receivers, etc.) can also be taken into account during this selection.

[0083] Alternatively, or in the case where none of the network slices forming part of the original slices intended to route the multicast stream according to the initial configuration of the routers of the aggregation perimeter satisfies all or a maximum of the technical requirements of the other slices, a network slice is possibly configured and deployed specifically to route the multicast stream in the aggregation perimeter. In this case, the transport slice selected or created on the fly by the controller is a dedicated network slice for routing multicast content in the aggregation perimeter of a communication network, specifically designed and sized for this purpose, in order to meet the same objectives of non-degradation of performance and / or quality of service as described previously.

[0084] We are now interested in the operations implemented by a router of the aggregation perimeter, when it receives a configuration instruction from the controller. Upon receipt of such an instruction, the router stores, within a so-called routing data structure, at least one correspondence between an identifier of the transport slice, included for example in the received configuration instruction, and an identifier of a network slice defined according to an initial configuration for routing the multicast stream via said router. In this way, even when the multicast stream is redirected to the transport slice, the router retains the information of the original slice via which it was intended to route the multicast stream according to the initial configuration of the router.

[0085] As illustrated in [Fig.2b], the aggregation perimeter typically comprises routers which can be described as border routers, in that they are located within the aggregation perimeter, but at the periphery of this perimeter, i.e. at the interface between the aggregation perimeter and the rest of the communication network.

[0086] Depending on the direction in which the multicast flow is routed (the direction according to the arrow DF, in the example of [Fig.2b]), the border routers are divided into two categories:

[0087] - input routers (router 7 in the example of [Fig.2b]), via which the multicast stream enters the PA aggregation scope; and

[0088] - output routers (routers 3 and 4 in the example of [Fig.2b]), by which the multicast flow leaves the PA aggregation perimeter.

[0089] In addition to the border routers, the aggregation perimeter also includes (optionally) other routers which can be referred to as intermediate routers (routers 5 and 6 in the example of [Fig.2b]), in that they are positioned between the entry and exit routers of the aggregation perimeter.

[0090] According to the general principle of the present technique, an edge router located at the entrance to the aggregation perimeter must be configured to terminate the deterministic replication of the same content within a distribution tree deployed in a plurality of slices, and proceed to forward the multicast flow using a distribution tree deployed in the transport slice.

[0091] A border router located at the output of the aggregation perimeter must for its part be configured to terminate the aggregation, that is to say to replicate the multicast flow in order to inject it into each distribution tree associated with the original slices intended to route the multicast flow according to the initial configuration of the routers, the identifier of these slices being available in the switching data structure.

[0092] [Fig.2b] illustrates in this respect explicitly on an example the result of the implementation of the present invention: a multicast flow associated with the same content previously duplicated and routed on the entirety of three network slices TRI, TR2 and TR3 is now, in a PA zone of the communication network corresponding to an aggregation perimeter, routed on a single slice, in this case the TRI slice in this example, which acts as a transport slice in this perimeter.

[0093] It is clear from the above that, in a particular embodiment, the controller may simply transmit configuration instructions to only the edge routers of the aggregation perimeter.

[0094] However, in another particular embodiment, configuration instructions are transmitted to all the routers in the aggregation perimeter, including the intermediate routers, which makes it possible to ensure rerouting to the transport slice in the case where, because for example new receivers wish to access the multicast stream, new access routers are added to the aggregation perimeter via these intermediate routers (routers 5 or 6 for example). By thus communicating the configuration information to all the routers in the aggregation zone and not just the border routers, reswitches and redundancies of the multicast stream to other slices in the aggregation perimeter are avoided, which is precisely the objective of the present technique.

[0095] To implement in practice the operations described above, it is proposed according to the present technique to intervene at the level of the routing protocol of the multicast flow.

[0096] Also, when it receives a configuration instruction from the controller, in addition to completing its routing data structure, the router also submits a membership request in order to join a distribution tree hosted on the transport slice. In other words, for the same multicast content, the routers in the aggregation zone maintain a single distribution tree: the one deployed within the transport slice. The information that the router is now attached to a single distribution tree is, for example, tracked in the router's MRIB (“Multicast Routing Information Base”) table.In a particular embodiment, the routing protocol is the PIM (“Protocol Independent Multicast”) protocol, and the membership request takes the form of a “far” PIM type message, comprising a new attribute called “MSLICE” identifying in particular the network slice hosting the distribution tree to which the router wishes to attach itself. According to a particular characteristic illustrated in relation to [Fig. 3], this new attribute is encoded according to a Type / Length / Value (TLV, RFC5384) format, the value field comprising the SID identifier of the target network slice, typically an identifier of the transport slice. Since the same network slice is sometimes likely to host several distribution trees (for example, a tree for SD broadcasting, another for HD broadcasting, etc.), it is also proposed according to another particular characteristic of the proposed technique, to add, in addition to the target network slice identifier, at least one useful discriminating data item in the case where simple knowledge of the target slice would not be sufficient to uniquely identify a distribution tree for the broadcasting of the multicast stream. Such discriminating data item may for example take the form of data item representative of a particular encoding of said multicast stream or representative of an absence of encoding information of said multicast stream. Also, according to a particular characteristic, the new attribute "MSLICE" also comprises, in addition to a target slice identifier, an encoding type ENCOD_TYPE, positioned at a value representative of a particular encoding (SD, HD, 4k, 8k, etc.) of the multicast stream, or to a value representing an absence of encoding information of said multicast stream (for example when the ENCOD_TYPE attribute is set to the value zero). The procedure for grafting to the distribution tree identified by such a “far” PIM message is then carried out according to the classic mechanism of the PIM-SM protocol (“PIM Sparse Mode”).

[0097] As already mentioned previously, in a particular embodiment, the network controller communicates the configuration instructions only to the routers of edge of the aggregation perimeter. According to a particular characteristic, in this case, it is proposed to add an additional attribute to the “Join” type messages sent according to the PIM protocol, in addition to the “MSLICE” attribute previously described. Thus, this new attribute, called “SWAP” and defined below, is present in the membership requests (i.e. the PIM “Join” messages) sent by a router upon receipt of configuration instructions from the controller, in addition to the “MSLICE” attribute which includes the transport slice identifier.

[0098] More particularly, such a new “SWAP” attribute includes at least the following information:

[0099] - an “Alternate_Slices” field, which includes the list of identifiers of the network slices which use the same distribution tree deployed in the transport slice, within the aggregation perimeter;

[0100] - a “Slice Aggregation Scope Border Routers” field. aggregation perimeter”, or SASBR), which includes information to identify not only the edge routers of the aggregation perimeter, but also the category to which they belong between:

[0101] — ingress routers through which the multicast stream enters the perimeter aggregation (for example router 7 in the example of [Fig.2b]), responsible for terminating the deterministic replication of the same content within a distribution tree deployed in a slice, and for routing the traffic characteristic of said content broadcast in multicast using the distribution tree deployed in the transport slice; and

[0102] — exit routers through which the multicast flow leaves the aggregation perimeter (e.g. routers 3 and 4 in the example in [Fig.2b]), responsible for replicating the content to inject it into each distribution tree of the original network slices, on which it was routed before entering the aggregation perimeter.

[0103] The “SWAP” attribute embedded within the “Join” PIM messages is more particularly used to implement such differentiated processing at the level of the routers of the aggregation perimeter, depending on whether the router considered is an intermediate router or a border router (and more particularly, in the latter case, a border router of the entry router type or a border router of the exit router type of the aggregation perimeter).

[0104] More particularly, upon receipt of a PIM “Join” message comprising the “SWAP” attribute, based on the information contained in the “Slice Aggregation Scope Border Routers” (SASBR) field, a router is able to determine whether or not it is part of the border routers of the aggregation scope, and, when it is indeed part of the border routers, further determine whether it is a router ingress or egress router of the aggregation perimeter.

[0105] Thus, in a particular embodiment, with reference to step 13 of [Fig.l], the controller can simply transmit a configuration instruction only to the output routers of the aggregation perimeter, while communicating to these output routers the information allowing them to construct the new “SWAP” attribute as defined previously, that is to say:

[0106] - the list of identifiers of the network slices which must use the same tree of distribution deployed in the transport slice, within the aggregation perimeter (in other words, the identifiers of the network slices on which it was detected, with reference to step 11 of [Fig.l], that a multicast flow was going to be duplicated) (which corresponds to the data intended to be inserted in the “Altemate_Slices” field of the “SWAP” attribute); and

[0107] - the identifiers of the border routers of the aggregation perimeter, as well as their category (ingress or egress router) (which corresponds to the data intended to be inserted into the “Slice Aggregation Scope Border Routers” field of the “SWAP” attribute).

[0108] Upon receipt of such an instruction, according to a conventional mechanism of the dynamic routing protocol, the “far” PIM message sent by the output router is propagated in the opposite direction to the routing direction of a multicast flow. The “SWAP” attribute integrated into this message is therefore itself propagated step by step, from the output routers to the input routers of the aggregation perimeter, passing through the intermediate routers.

[0109] Each router on this propagation path is thus able to determine its category (egress router, intermediate router, or ingress router) on the basis of the information included in the “Slice Aggregation Scope Border Routers” field of the “SWAP” attribute, and determine, if necessary, for which network slices it must switch the routing of the multicast flow to a distribution tree hosted on the transport slice on the basis of the information included in the “Alternate_Slices” field of the “SWAP” attribute. In particular, during these operations, the intermediate routers complete or update their switching data structure by associating the identifier of the transport slice with the identifiers of the slices recorded in the “Alternate_Slices” attribute.

[0110] According to a particular characteristic, when the message reaches an entry router of the aggregation perimeter, it is no longer useful to propagate the “SWAP” attribute to the following routers insofar as these routers are not part of the aggregation perimeter: once this point has been reached, it is therefore proposed in the invention to switch back to a conventional PIM mode, i.e. a message propagation of the “far” PIM type not including the “SWAP” attribute. It should be noted that the list of identifiers of slices entered in the switching data structure of a router can be modified at any time by the network controller, or following the reception of a "far" PIM message which includes the new "SWAP" attribute. Thus, a new association between a new slice identifier and the transport slice identifier can be added to the switching data structure, or an existing association deleted, the structure of the distribution trees evolving dynamically over time, in particular depending on the receivers which are grafted onto this structure or which are disconnected from it. Similarly, the controller can also modify the aggregation perimeter, in particular by designating other border routers. For example, with reference to [Fig.2b], while routers 3, 4, 5, and 6 were initially configured as border routers by the controller, the controller may subsequently modify this configuration to define routers 3, 4, and 7 as new border routers.

[0111] Furthermore, if the invention is described previously in particular embodiments in which the dynamic routing protocol used is the PIM protocol, this example is purely illustrative and not limiting. In particular, the general principle of the method described applies more generally to IP / MPLS networks (“Multi-protocol Label Switching”, in English), and is therefore not limited to the PIM protocol, which is provided solely as an example of a particular implementation.

[0112] Finally, in relation to [Fig.4], we present the simplified structure of an entity, typically a controller of a communication network, for the implementation of an optimization method according to at least one embodiment described above.

[0113] As illustrated by [Fig.4], such an entity comprises at least one memory 41 comprising a buffer memory, at least one processing unit 42, equipped for example with a programmable computing machine or a dedicated computing machine, for example a processor P, and controlled by the computer program 43, implementing steps of at least one method according to at least one embodiment of the invention.

[0114] At initialization, the code instructions of the computer program 43 are for example loaded into a RAM memory before being executed by the processor of the processing unit 42. More particularly, the processor of the processing unit 42 implements steps of the method for optimizing the broadcasting of a multicast stream within the network, as described previously, according to the instructions of the computer program 43, to:

[0115] - determine, following the obtaining of information representative of the fact that said multicast flow is caused to be duplicated on a plurality of said network slices, a perimeter of said communication network, called aggregation perimeter, comprising a plurality of routers included in at least one distribution tree of said multicast flow;

[0116] - transmit, to at least one router of said aggregation perimeter, to at least one configuration instruction for said router so that within said aggregation perimeter, said multicast flow is routed on only one of said network slices, called transport slice.

Claims

Claims

1. Method for optimizing the broadcasting of a multicast stream within a communication network implementing network slices, said method being characterized in that it comprises: - the determination (12), by a controller of said communication network, following the obtaining (11) of information representative of the fact that said multicast stream is to be duplicated on a plurality of said network slices, of a perimeter of said communication network, called aggregation perimeter, comprising a plurality of routers included in at least one distribution tree of said multicast stream; - the transmission (13), by said controller, to at least one router of said aggregation perimeter, of at least one configuration instruction of said router so that in said aggregation perimeter, said multicast stream is routed on only one of said network slices, called transport slice.

2. Method according to claim 1, characterized in that said configuration instruction is transmitted at least to all the routers of the aggregation perimeter located on the periphery of said aggregation perimeter.

3. Method according to claim 1, characterized in that it comprises, upon receipt of said configuration instruction by a router of said aggregation perimeter, the storage, within a data structure of said router, of a correspondence between an identifier of said transport slice and an identifier of a network slice defined according to an initial configuration for the routing of said multicast flow via said router.

4. Method according to claim 3, characterized in that said identifier of said transport slice is included in said configuration instruction.

5. Method according to claim 1, characterized in that said transport slice is a slice specifically designed and sized for the routing of said multicast flow in said aggregation perimeter.

6. Method according to claim 1, characterized in that said transport slice is selected by said controller from among the network slices provided for routing the multicast flow according to an initial configuration of the routers of the aggregation perimeter, called original slices.

7. A method according to claim 6, characterized in that said transport slice selected by said controller satisfies requirements techniques associated with each of the said original slices.

8. Method according to claim 1, characterized in that said aggregation perimeter comprises at least one input router through which said multicast flow enters said aggregation perimeter and at least one output router through which said multicast flow leaves the aggregation perimeter, and in that said at least one configuration instruction causes: - said at least one input router to proceed with the routing of the multicast flow using a distribution tree deployed in said transport slice rather than in at least one origin slice on which said multicast flow is routed upstream of said input router; and - said at least one output router to proceed with the routing of the multicast flow using at least one distribution tree deployed in said at least one origin slice, downstream of said output router.

9. Method according to claim 8, characterized in that said aggregation perimeter comprises at least one intermediate router, located between said at least one input router and said at least one output router.

10. Method according to claim 8 or 9, characterized in that it comprises, upon receipt of said configuration instruction by said at least one router, the transmission, by said at least one router, according to a dynamic routing protocol, of a transplant request message to a distribution tree of said multicast flow hosted in said transport slice, said transplant request message comprising an identifier of said transport slice.

11. Method according to claim 10, characterized: - in that said at least one configuration instruction comprises data making it possible to identify said at least one input router, said at least one output router, and said at least one original slice; - in that said configuration instruction is transmitted only to said at least one output router; - and that, upon receipt of said configuration instruction, said at least one graft request message sent by said at least one output router further comprises said data making it possible to identify said at least one input router, said at least one output router, and said at least one original slice.

12. Method according to claim 11, characterized in that said protocol dynamic routing is the PIM protocol and in that said graft request message is a "far" type message according to said PIM protocol, adapted to include said identifier of said transport slice, and said data making it possible to identify said at least one input router, said at least one output router, and said at least one origin slice.

13. Control entity for optimizing the broadcasting of a multicast stream within a communication network implementing network slices, comprising at least one processor configured to: - determining, following the obtaining of information representative of the fact that said multicast flow is to be duplicated on a plurality of said network slices, a perimeter of said communication network, called aggregation perimeter, comprising a plurality of routers included in at least one distribution tree of said multicast flow; - transmitting to at least one router of said aggregation perimeter at least one configuration instruction of said router so that in said aggregation perimeter, said multicast flow is routed on only one of said network slices, called transport slice.

14. Computer program comprising instructions for implementing a method according to any one of claims 1 to 12 when this program is executed by a processor.

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