EP2332332A1

EP2332332A1 - Method and device for redirecting a data flow monitoring query

Info

Publication number: EP2332332A1
Application number: EP09741379A
Authority: EP
Inventors: Frédéric FIEAU; Thang Vu Duong
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2008-09-08
Filing date: 2009-09-08
Publication date: 2011-06-15
Also published as: WO2010026355A1; US8639777B2; US20110167138A1

Abstract

The invention relates to a method and device for redirecting a data flow monitoring query. The method according to the invention includes: - a step of obtaining information representing a current data flow monitoring capability for a plurality (11) of broadcast servers upon receiving said monitoring query sent by a terminal apparatus (STB); - a step of selecting, using said information, a server (NTSSk0) from among said plurality of servers that is capable of monitoring said flow (FLo) broadcast by the source; - a step of sending a flow capture query to the selected server if the latter has not already captured the flow for at least one other terminal apparatus; and - a step of redirecting the monitoring query to the selected server.

Description

Method and device for redirecting a request for controlling a data flow

BACKGROUND OF THE INVENTION The present invention relates to the general field of telecommunications.

It relates more particularly to the control mechanisms on data streams broadcast by a source on an IP network, such as for example multimedia data streams broadcast in multicast mode within an IPTV (Internet Protocol Television) infrastructure.

The invention applies in particular, in a preferred but non-limiting manner, in the context of the management and implementation of a time shift service, managed by a telecommunications network. Such a service is also known as "network time shifting" (hereinafter referred to as nTS service).

In known manner, an nTS service allows an end user, receiving on a terminal equipment an IPTV data stream broadcast in real time (commonly referred to as "live stream"), to control control operations on this stream (or more precisely on a recording of this stream), similar to those provided by a VCR. These control operations are for example read, pause, rewind, stop, etc. operations.

Deployment of such a service by an operator of a telecommunications network requires the implementation in the network of broadcast servers. These broadcast servers must be adapted to capture (that is to say record), in circular buffers, the different streams for which the operator wishes to offer this service, and then to broadcast these streams to the user terminal equipment. subscribers to the service, depending on the operations required by these subscribers. In the techniques of the prior art, the broadcast servers considered are programmed with a predefined list of streams to capture, so as to allow the permanent capture of all the streams for which the operator wishes to offer this service. This therefore requires the deployment of a large number of servers and / or very large capacity servers, in order to be able to offer this service for a large number of streams (that is to say of channels broadcast by the network of telecommunication) and to a large number of subscribers. This constraint is all the more problematic as the number of streams broadcast today on telecommunications networks is constantly growing.

There is therefore a need for a solution for managing such a control service that does not have such drawbacks.

Obiet and summary of the invention

The present invention responds to this need by proposing a method for redirecting a request for controlling a data stream broadcast by a source in a telecommunications network, transmitted by a terminal equipment, this method comprising:

upon receipt of this request, a step of obtaining information representative of a current flow control capability for a plurality of broadcast servers; a step of selecting, using at least this information, a server from the plurality of servers, able to control the stream broadcast by the source;

a step of sending a request to capture this stream of data to the selected server if the latter does not already capture this stream for at least one other terminal equipment; and

a step of redirecting the control request to the selected server.

Correlatively, the invention also provides a device for redirecting a request for controlling a data stream broadcast by a source in a telecommunications network, transmitted by a terminal equipment, this device comprising:

means, activated upon receipt of this request, for obtaining information representative of a current data flow control capability, for a plurality of broadcast servers; means for selecting, using at least this information, a server from among the plurality of servers, able to control the stream broadcast by the source;

means for determining whether or not the selected server captures this data stream for at least one other terminal equipment; means for sending a request to capture this stream to the selected server, activated if it does not already capture this stream for at least one other terminal equipment; and

means for redirecting the control request to the selected server.

It will be noted that, within the meaning of the invention, a control request for a data stream may designate either a request for activation or deactivation of a control of the data flow, a request to establish a control session of this stream or a request to activate a specific control operation on this stream such as for example a pause, read or rewind operation.

Moreover, within the meaning of the invention, the current flow control capacity of a broadcast server characterizes its ability to control, at the current time, a data stream, that is to say, to capture it. and broadcast it to a terminal equipment in order to be able to implement control operations on this stream, and this in view of the data flows already controlled by this server at this current time. Here is meant by capturing a stream of data, the recording of this stream. The current flow control capacity of a server can thus be expressed, for example, in the form of a bit rate or a number of data streams that can still be controlled by the server, given the flows already controlled. by this server at the current time.

The invention applies in particular to the management of a control of a time shift nTS service data stream managed by the telecommunications network. The terminal equipment can be in this case, for example, a TV decoder also called "set top box".

The invention thus makes it possible, in this context, to dynamically manage and activate the recording of a stream broadcast over the telecommunications network by a broadcast server, as a function of the requests from the terminal equipments receiving this stream.

The number of broadcast servers required to implement an nTS service that benefits from this dynamic management, as well as the capacity, particularly in terms of storage space, of these servers, are then advantageously limited, which reduces the costs of deployment necessary for the service.

Indeed, unlike the techniques of the prior art, the invention makes it possible to capture at the broadcast server level only the streams for which a control (nTS service) is required by a terminal equipment. Also, for the sake of simplification, we will talk later in this dynamic nTS service document.

Thus, smaller broadcast servers can be used to implement the invention, which makes it possible to deploy these servers closer to the terminal equipment in the network (for example at the edge of the collection network or in the collection network, also called backhaul). However, of course, these broadcast servers can also be deployed, as for the techniques of the prior art, at the point of presence of the network (POP) located at the junction of the collection network and the network. core network ("backbone").

Furthermore, advantageously, the invention makes it possible to control congestion at the broadcast server level by selecting, using information representative of a current flow control capability of the broadcast servers (that is, that is, reflecting the state of the control resources available at the broadcast server at the time of the processing of the control request by the redirection device), a broadcast server able to control the data flow, in other words to the capture and broadcast it to the terminal equipment. In a particular embodiment of the invention, the information representative of a current flow control capability of a broadcast server comprises representative information:

a current capacity of broadcast sessions of this server (i.e. reflecting the current ability of the server to broadcast a stream to a terminal equipment, given the streams already broadcast by this server); and

- a current stream capture capability of this server (ie reflecting the current ability of the server to capture a stream, given the streams already captured by this server). Thus, during the redirection method according to the invention, a broadcast server will be considered to be able to control a stream if it has sufficient current capture capabilities and broadcast sessions for that stream.

If a server already captures this stream for another terminal equipment, it will be considered that it has a sufficient current capture capacity for this stream. Information representative of a current capture capacity of this server may be, in this case, the information that this server captures this stream.

It will be noted that the invention advantageously makes it possible to combine captures (recordings) of static data streams, that is to say as performed in the prior art where the broadcast servers are programmed with a predefined list of stream to capture so as to allow the permanent capture of these flows, and captures of dynamic type, that is to say, as permitted by the invention according to the needs of the terminal equipment. In a particular embodiment, the redirection method further comprises, after the selection step, a step of establishing a session with the terminal equipment for the data stream. During the maintenance of this session, at least one other control request issued by the terminal equipment for this flow is redirected to the server already selected.

Correlatively, the redirection device may furthermore comprise means for establishing a session with the terminal equipment for this data stream, the redirection means of the device being adapted, during the maintenance of this session, to redirect at least one other request. from the terminal equipment for this stream to the already selected server.

Thus, the selection step is implemented once, for example the first time that the terminal equipment sends a control request on a given stream, this request comprising or not a control operation on the stream. This speeds up the execution of the dynamic nTS service according to the invention.

The selection of the broadcast server to which to redirect requests from the terminal equipment may also depend on the proximity of the server to the terminal equipment in the telecommunications network. For example, we will select a broadcast server capable of capturing and broadcasting the stream belonging to the same subnetwork of the telecommunications network as the terminal equipment. In this way, the speed and the reliability of execution of the dynamic nTS service according to the invention will be optimized (it limits in particular the latency and the loss of packets due to a journey of data packets of the flow in the network too long).

The server may also be selected based on the existence at this server of a capture of the data stream for at least one other terminal equipment.

Thus, the storage space (Random Access Memory (RAM) or disk array for example) required to implement the nTS service is optimized, because it favors the dissemination of the same data stream by a single server. Of course, several broadcast servers may still be required to capture and broadcast the same data stream, especially if this is necessary for example because their respective capacity is not sufficient to satisfy all equipment terminals requiring nTS operations on this stream (high demand stream).

It will be noted that other selection criteria may be considered, depending on the policy of the telecommunications network operator offering the dynamic nTS service.

For example, the selection step can also take into account a type of data stream capture for at least one broadcast server, which type can be selected from at least one type of static capture and one type of dynamic capture. For this purpose in particular, the operator can specify, in a database defining the service management policy: - the data streams recorded statically at different broadcast servers. This may be, for example, streams from thematic or regional channel groups; and - dynamically recorded data streams.

The choice of the type of recording can be established according to various criteria, such as, for example, a rate of audience on a given channel: in this case, if a channel benefits from an audience rate beyond a certain Audience threshold, the streams of data it broadcasts can be switched in the list of static captures for a predetermined duration. In a particular embodiment of the invention, the redirection method further comprises:

a step of detecting a data flow control deactivation event for the terminal equipment; a step of determining whether the selected server for the data flow for the terminal equipment captures this data flow for at least one other terminal equipment;

if this is not the case, a step of sending a request to end the capture of this data stream to the selected server. Correlatively, the redirection device may further comprise:

means for detecting a data flow control deactivation event for the terminal equipment;

means for determining whether the selected server for the data stream for the terminal equipment captures this data stream for at least one other terminal equipment;

means for sending a request for the end of capture of this data stream to the selected server, activated if this is not the case.

In this way, it is avoided to capture flows for which control is no longer desired by any terminal equipment.

Alternatively, the redirection method further comprises a step of determining a type of data stream capture, which type can be selected from at least one type of static capture and a type of dynamic capture, and if it is determined that the capture of the stream is of static type, the step of sending an end of capture request is not implemented.

In a particular embodiment of the invention, the redirection method comprises, before the redirection of a control request to the selected server: a detection step that the control request comprises a control operation which can not Be implemented by the selected server and

a step of replacing this operation in the control request with an authorized control operation. Correlatively, the redirection device may further comprise: detection means that the control request includes a control operation that can not be implemented by the selected server; and

- Replacement means in the control request for this operation by an authorized control operation, said detection and replacement means being activated before redirecting a control request to the server selected by the redirection means.

In this way, it is possible to anticipate errors that may appear at the broadcast server, especially when the capture of the stream has started recently and certain flow control operations, such as for example a rollback on this stream, can not be performed by the broadcast server (the buffer including the record is not sufficiently filled). To avoid this, we can advantageously replace in the request of the terminal equipment the return operation by a pause operation for example.

It can also be envisaged, in other embodiments, that the method and the redirection device according to the invention present in combination all or part of the aforementioned characteristics. In a particular embodiment, the various steps of the redirection method are determined by computer program instructions.

Accordingly, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a redirection device or more generally in a computer, this program comprising instructions adapted to the implementing the steps of a redirection method as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.

The invention also relates to a computer-readable information medium, comprising instructions of a computer program as mentioned above. The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.

On the other hand, 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 program according to the invention can be downloaded in particular on an Internet type network.

Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

Brief description of the drawings

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

- Figure 1 shows a redirection device according to the invention, in its environment, in a particular implementation implementation; - Figure 2 shows the hardware architecture of a redirection device according to the invention, in a particular embodiment; and

FIGS. 3A-3D represent the main steps of a redirection method according to the invention, when it is implemented by a redirection device as represented in FIGS. 1 and 2, in a particular embodiment .

Detailed description of an embodiment

FIG. 1 illustrates an implementation of the invention for a control of a time shift nTS service data stream managed by a telecommunications network 1. As previously described, an nTS service allows an end user, receiving on a terminal equipment a data stream

IPTV broadcast in real time by a source of a telecommunications network, to control control operations on this stream similar to those provided by a VCR.

In the embodiment described here, the telecommunications network 1 is equipped with an IPTV infrastructure enabling the broadcasting of IPTV multimedia streams in real time, by implementing known mechanisms for multicast broadcasting and "streaming". In a known manner, streaming means the broadcasting mechanism of continuously sending data from a source to a destination without the destination needing to download or store the data as a whole.

The IPTV infrastructure of the network 1 includes, for this purpose, an HE headend (source within the meaning of the invention) adapted to generate and broadcast in the telecommunications network 1 FL data streams. These data streams consist here of a series of packets carrying TV-type multimedia data (data broadcast on channels or channels of audiovisual programs). The IPTV infrastructure of the network 1 also includes ROUT devices (such as routers), allowing the diffusion of FL data streams in a multicast broadcast mode. In a known manner, a multicast broadcasting mode makes it possible to organize and optimize the sending of the same stream of data transmitted by a source to several recipients, thus avoiding unnecessary replication of the data packets in a network.

Note that the invention also applies when a unicast broadcast mode of the data stream between the source and the terminal equipment is envisaged. Those skilled in the art will easily transpose the embodiment described here in the context of a unicast diffusion mode, so that this transposition will not be described in more detail here.

FL streams are received and decoded at an end user U by a terminal equipment STB. This terminal equipment is for example here a TV set-top box or "set top box". Of course, other terminal equipment equipped with such a decoder can be considered.

To offer a dynamic nTS service as proposed by the invention, the IPTV infrastructure of the network 1 is equipped with an nTS system 10 including:

a set 11 of K NTSS broadcast servers ₁ , ..., NTSSK;

a redirection device RB according to the invention also called redirection server RB;

a PORT server hosting a portal dedicated to the nTS service; - a "dynamic" sDB database, called a session database;

- a "static" tDB database, called a topology database.

Optionally, the system 10 may also include an oDB database specifying an operator policy, referred to as the operator base (shown in dashed lines in Figure 1), and specifying a type of data stream capture based on the strings of programs that broadcast them, for one or more broadcast servers of the set 11 (ie static or dynamic recording).

The NTSSk broadcast servers, k = 1,..., K, implement nTS services such as those proposed in the prior art. Each of these broadcast servers here has the hardware architecture of a computer, and notably comprises a processor, a RAM type of RAM and a ROM type ROM (not shown).

It also includes means for capturing flows allowing it, on request of the redirection server: - to subscribe to at least one ROUT router, to receive one or more determined data streams, broadcast (s) ) in multicast mode by the headend HE, and for which service (s) nTS is desired; and

- Unsubscribe from the same router, to no longer receive one or more of these data streams.

These subscription and unsubscription operations are carried out by the ING means using the Internet Group Management Protocol (IGMP), for example.

The means ING are further adapted to capture (that is to say record) a data stream to which the NTSS server _k is subscribed, in a BUF circular buffer of predefined size. This circular buffer is located in a storage space of the NTSSk server, for example in the RAM or in a hard disk of this server. We will consider a circular buffer per captured data stream.

Furthermore, the NTSS server _k also comprises STR broadcasting means adapted to interpret and process a control request issued by a terminal equipment for a given data stream.

Such a request may include a read, pause, etc. operation, and conforms to a predefined protocol.

In the embodiment described here, the control requests sent by the terminal equipment STB as part of the dynamic nTS service are Real Time Streaming Protocol (RTSP) requests. Thus the STR means implement here the RTSP protocol, known to those skilled in the art. This protocol is described in particular in the document

IETF RFC 2326 entitled "Real Time Streaming Protocol". In a variant, these requests may be in accordance with other application protocols such as the Session Initiation Protocol (SIP) or the HyperText Transfer Protocol (HTTP).

The means STR are also adapted to broadcast in unicast mode to the terminal equipment, the contents of the circular buffer BUF corresponding to a control operation contained in a control request RTSP issued by this equipment. They can in particular implement for this purpose a known transport protocol such as RTP / UDP,

UDP, TCP or HTTP.

It will be noted that the means ING and STR, as well as the operating principle of a circular buffer, are known to those skilled in the art and will not be detailed further here.

Moreover, in the example described here, the capture means

ING and STR broadcast are considered implemented by a single device (eg a single computer), namely the NTSS server. However, in a variant, the means ING, the means STR and the buffer BUF can be implemented by separate devices; NTSS server will then be understood to mean a system comprising these different devices.

The redirection server RB is in accordance with the invention. It has here the hardware architecture of a computer, as represented in FIG. 2, and comprises a processor 20, a random access memory of the RAM type

21 and a ROM ROM 22. This read-only memory 22 constitutes a recording medium in accordance with the invention, readable by the redirection server RB, and on which is recorded a computer program according to the invention. This program includes instructions for performing the steps of a redirection method according to the invention. The main steps of this method are shown, in a particular embodiment of the invention, in FIGS. 3A-3D described later (steps F1 to F190).

The redirection server RB also comprises means of communication 23 with the terminal equipment STB and with the broadcast servers NTSSk, implementing the RTSP protocol in the example described here.

It further comprises means 24 for interrogating and updating the database of sDB sessions. These means 24 are also suitable for interrogating the tDB topology database.

The tDB topology database includes, for each NTSS server _k :

the maximum capacity for capturing streams of this server, denoted ICapMax (k), that is to say the maximum number of data streams that can be captured (ie recorded) simultaneously by the NTSS server _k . This capability takes into account the capture and processing resources implemented by the NTSS server _k to satisfy control operations required by a terminal equipment on a given flow; and the maximum capacity of broadcast sessions of this server, denoted DCapMax (k), that is to say the maximum number of broadcast sessions that can be managed simultaneously by this server for different terminal equipments. In known manner, a broadcast session includes the stream broadcast between the broadcast server and a terminal equipment, as well as the control flows exchanged between the terminal equipment and the broadcast server and the control flows exchanged between the redirection server. and the broadcast server. This capacity thus takes into account the processing and broadcasting resources implemented by the NTSS server _k to satisfy control operations required by a terminal equipment on a given flow. The ICapMax (k) and DCapMax (k) capabilities are static, i.e. invariant, data that depends on NTSSk server resource requirements (eg, storage space, CPU performance, etc.) . They can vary from one NTSS server to another.

This static data can be provisioned in the tDB database or be communicated by the NTSSk servers during a preliminary phase.

In the example described here, the topology database tDB also comprises, for each NTSS server _k , a location parameter of this server. This location parameter is for example here an identifier

IDSub (k) of the subnet to which the NTSS server _k belongs in the telecommunications network 1, and more precisely an IP address.

Alternatively, other subnet identifiers may be considered, as well as other location parameters (such as for example a CLID or Calling An IDentifier in English).

The sDB session database includes, at a given moment:

a list of current flow capture sessions implemented by NTSS servers _k of set 11 at this time; and

a list of current broadcast sessions managed by NTSSk servers of the set 11 at this time.

Each current stream capture session is defined in the sDB database by a triplet comprising: an identifier of the NTSS server carrying out the capture of the stream;

an identifier of the captured stream;

an indicator of the instant at which this flux capture started.

Each current streaming session is defined in the sDB database by a triplet comprising: an identifier of the broadcast stream;

an identifier of the NTSS server carrying out the control of this broadcast;

- an identifier of the terminal equipment that required the control.

We will now describe, with reference to FIGS. 3A to 3D, the main steps of the redirection method according to the invention, when it is implemented, in a particular embodiment, by the redirection server RB shown in FIGS. 1 and 2. In this embodiment, it is envisaged that a user U of the terminal equipment STB wishes to access the dynamic nTS service proposed by the operator of the telecommunications network 1, in order to implement time shift operations on a data stream. multimedia data FU received in real time by the terminal equipment STB, for example a return operation OP (control operation within the meaning of the invention).

Referring to FIG. 3A, it is assumed that for this purpose, the user U has previously subscribed to this service with the PORT server, and that the terminal equipment STB obtains the authorization to access the dynamic nTS service. for example, by correctly authenticating with the PORT server.

It should be noted that in order to benefit from this service, the terminal equipment STB will have previously unsubscribed from the multicast broadcast of the stream FL ₀ to the router ROUT.

Alternatively, other network equipment, such as a DSLAM device (Digital Subscriber Access Multiplexer) network 1 connected to the terminal equipment STB, may be responsible for this unsubscription. In order to access the return operation OP, the user U for example presses a corresponding key on a remote control of the terminal equipment STB, which transmits the request for access to the user's operation OP. U to the terminal equipment.

Upon receipt of this access request (step ElO), the terminal equipment STB sends the redirection server RB a request R_act (FI_o) initialization of a control session for the data stream FL ₀ (step E20) . This request is a control request within the meaning of the invention.

The request R_act (FI_o) is here an RTSP request including an identifier of the stream FL ₀ (eg a multicast IP address). It may also include the command relating to the OP control operation required by the user U on the stream FL ₀ - However, this command may be sent later to the redirection server RB, once the control session has been established. embodiment described here). On receipt of the R_act control request, the RB server selects, according to predetermined criteria, an NTSSRO server from the plurality of broadcast servers.

To this end, the redirection server RB initially interrogates, using the interrogation means 24, the sDB session database (step FlO), so as to obtain for each NTSSk server:

the current number ICurr (k) of streams of data simultaneously captured by this server at this time (i.e. current number of capture sessions); the current number DCurr (k) of broadcast sessions simultaneously managed by this server at this instant; and

the identifiers of the streams captured by this server.

The numbers ICurr (k) and DCurr (k) are computed in a known manner by the interrogation means of the database sDB, from the information broadcast sessions and capture sessions stored in this database, to the for example, an appropriate query query obvious to the skilled person.

The redirection server RB also queries, during this step, the tDB topology database to obtain, for each NTSS server _k , the maximum capacities ICapMax (k) and DCapMax (k).

From this information, it evaluates the values of [ICapMax (k) -ICurr (k)] and [DCapMax (k) -DCurr (k)], representative respectively of the current capture capabilities and server broadcast sessions. NTSS _k , and more generally a current flow control capability of the NTSSR server. Note that in this example, the capture capabilities and broadcast sessions are expressed in the form of flow numbers, however this assumption is not limiting, one could for example express these capabilities in the form of flow rates. It is the same of course for the capacity of flow control of the server.

Using these values, the redirection server constitutes, in a second step (step F20), a list L of potential NTSS servers that are potential candidates among the NTSS servers _k , that is to say, that are capable of capturing the FL ₀ data stream and establish a broadcast session of this data stream for the terminal equipment STB (that is, again, which have a current capacity of sufficient flow control, for example non-zero).

More precisely here, this list consists of the NTSS servers _k of the plurality of servers for which the following conditions (1) or (2) are verified:

Conditions (1): A server is a potential candidate if it has a current stream capture capability and a current capacity of broadcast sessions sufficient to provide the service (ie, above predetermined thresholds, εl and ε2> 0), for example here if: [ICapMax (k) -ICurr (k)]> εl and [DCapMax (k) - DCurr (k)]> ε2

Conditions (2): A server is a potential candidate if it has a current broadcast session capacity sufficient to provide the service (ie greater than a predetermined threshold ε2) and if it already captures the FLo stream for another terminal equipment , ie for example here, if:

[DCapMax (k) - DCurr (k)]> ε2 and the server already captures the stream

FL ₀ for another terminal equipment.

Note that, for a server verifying conditions (2), information representative of a current capture capacity of this server in the sense of the invention may consist of the information that this server captures the flow required by the server. terminal equipment.

In the example described here, if the list L thus obtained comprises several potential candidate NTSS servers, the redirection server RB then preferably selects, in the order: - an NTSSRO server of this list already capturing the stream FL ₀ for a other terminal equipment;

the NTSSRO server of the list closest to the terminal equipment STB in the network 1.

An NTSS server will be considered here as being the closest to the terminal equipment STB if it belongs to the same subnet in the network 1 as the terminal equipment STB. To determine this server, the redirection server RB extracts from the control request R_act, the IP address of the terminal equipment STB (address transmitted in the request in a manner known per se) and compares it with the identifiers IDSub (k) of the under- NTSSk server networks of list L. These identifiers are obtained by querying the tDB topology database using means 24.

Of course, other identifiers could be considered.

Alternatively, when the list L includes several potential candidate NTSS _k servers, other selection criteria can be used to select the NTSSko server.

For example, it is possible to consider a load sharing criterion (or "load balancing" in English), consisting of alternately selecting, for different terminal equipments, the potential candidate servers from the list. Other load-sharing strategies can of course be considered, such as selecting the server that captures the least flow.

In a variant, the redirection server RB also interrogates, during this step, the oDB operator database to obtain the type of record specified for the data flow object of the control request. Advantageously, it will be possible, during the establishment of the list L, to privilege an NTSSko server of this list which captures the stream FL ₀ statically.

It is assumed here that among the list L, none of the potential candidate servers already captures the stream FL ₀ for another terminal equipment. The closest NTSSko server is then selected from the terminal equipment STB, as previously described.

Since this NTSSko server does not capture the stream FL ₀ , the redirection server RB sends the means ING of the NTSSω server a request RTSP for capturing the data stream FL ₀ (step F30), noted below.

R_cap (FL-o).

This request is processed by the means ING, which then send a request for subscription to the stream FL ₀ to the router ROUT (for example using the IGMP protocol), in order to benefit from the multicast broadcast of the stream FL ₀ implemented. by the headend HE (step GlO).

As a variant, to benefit from a unicast broadcast of the stream FL ₀ , an RTSP Setup or HTTP Setup request may be sent to a device of the RTSP server or proxy type network, or respectively to a device of the server type network or HTTP proxy. Following this subscription, a flow capture session FL ₀ is initiated by the means ING (step G20). In other words, the means ING record the stream FL ₀ , broadcast in real time in multicast mode by the headend HE, in a circular buffer BUF associated with the stream FL ₀ .

They then send an RTSP acknowledgment message ACK (eg RTSP 200 OK) to the redirection server RB in response to the capture request R_cap (FU) (step G30).

On receipt of this acknowledgment message, the redirection server RB updates the dynamic database sDB (step F40), with the new entry the capture session of the stream FL ₀ initiated by the NTSSko server. As mentioned earlier, this new capture session is represented in the dynamic database sDB by:

the identifier of the NTSS server _k0 ;

the identifier of the flow FL ₀ ; and

- a to indicator of the moment at which flow capture started.

Note that if, during step F20, an NTSSRO server already capturing the stream FL ₀ for another terminal equipment is selected, the steps F30 sending a capture request to the server NTSSk ₀ , GlO of NTSS server subscription _k0 , G20 of initiation of a stream capture session FL ₀ , G30 of sending an acknowledgment message to the redirection server RB and F40 of the database update of sDB are not not implemented, the NTSSko server is already subscribed to the broadcast of FL ₀ stream and recording this stream.

Following the update of the database sdB, the redirection server sends to the terminal equipment an acknowledgment message (eg RTSP 200 OK), in response to the control request R_act (step F50). A SESS control session is then established between the terminal equipment STB and the redirection server RB (step F60). The establishment of this RTSP session includes the creation of a context (ie a set of data) associated with this session, and saved for example in the database sDB. Such a context notably contains, in a manner known per se, a session identifier, an identifier of the terminal equipment STB (eg its IP address) and an identifier of the NTSS server _k o.

Following the establishment of this session, the R_act control request sent by the terminal equipment STB to the redirection server RB is redirected by this server to the distribution means STR of the NTSSko server, in the form of a control request. RTSP R_act '(step F70). The broadcast server NTSS _k o then establishes a broadcast session for the stream FL ₀ and the terminal equipment STB (step G40) and informs the redirection server RB (step G50), which updates the dynamic database sDB with this new broadcast session (step F80). As mentioned earlier, this new broadcast session is represented in the sDB database by:

- the identifier of the NTSSRO server;

the identifier of the flow FL ₀ ; and

- the identifier of the terminal equipment STB. It will be noted that the redirected request R_act 'may be identical to the control request R_act, or alternatively, slightly modified so as to include including parameters of the NTSS server _k o such as its IP address or a port number.

It will also be noted that in order to maintain the SESS session between the terminal equipment STB and the redirection server, the latter sends periodically here, to the terminal equipment, session maintenance messages ("keep-alive" messages). ) (step F90). For this, the RB server can use the RTSP protocol, or alternatively the SIP or HTTP protocol. If no response from the terminal equipment to these messages is received within a predetermined time interval following their sending, the redirection server RB terminates the SESS control session. Otherwise, the SESS session is maintained.

In a variant, the redirection server RB does not send periodic maintenance messages, but it is the terminal equipment STB that is at the origin of these messages. Similarly, if the RB server does not receive such a message within a predetermined time interval, then it terminates the SESS session established with the terminal equipment STB.

With reference to FIG. 3B, in the embodiment described here, to facilitate the interaction of the user U with the dynamic nTS service, the terminal equipment STB sends a request to the portal PORT in order to obtain the status of the BUF buffer associated with FL flow ₀ (step E30). This request can be in particular an HTTP or SIP request. Here is meant by buffer state its filling rate.

This filling rate is calculated by the portal PORT from the start time to the capture session of the stream FL ₀ by the server NTSSR _O , provided, of course, that the filling rate of the buffers by NTSS servers and the size of these buffers are known (which is assumed here).

The start time to is obtained by the PORT portal by consulting the sDB database (step H10). The server PORT sends, in response to the request of the terminal equipment STB, the fill rate thus calculated, for example in the form of a progress bar displayed on the screen of the user U (step H20 ) and updated in real time.

With reference to FIG. 3C, following the establishment of the SESS control session, the terminal equipment STB sends the redirection server RB a request to activate the operation OP (step E40).

In the example described here, it is assumed, as mentioned previously, that this OP operation is a return operation on the stream

FL ₀ at a predetermined time ti of the stream, so as to review this flow from this moment ti. Of course, other time shift operations may be required, such as a read, pause, etc. operation.

The activation request, denoted by R (OP, FI_o), is a control request within the meaning of the invention and comprises the desired OP operation on the flow FL _{0 as} well as the instant ti.

On receipt of this request, the server RB interrogates the database sDB (step FlOO), to determine if a control session is already established with the terminal equipment STB for the stream FL ₀ -

If necessary (for example here the SESS session is established), it identifies, from the context of this session, the NTSS server _k o to which to redirect the control requests and more particularly to activate time shift operations during maintaining this session (step FIlO).

The request R (OP, FI_o) is then redirected to the means STR of this NTSS server _k o in the form of a request R '(step F120).

In the embodiment described here, during the step FI10, the redirection server RB also determines, by consulting the sDB session database, the start time to the stream capture session.

FL ₀ by the NTSSko server, and calculates, using this instant, the filling rate of the buffer BUF associated with this stream as described above. The server RB then verifies whether the OP backtracking operation at the instant ti is allowed. If the server RB detects that the filling rate calculated is not sufficient to allow the OP operation required by the terminal equipment, then, before redirecting the request R to the server NTSSRO, it replaces in this request the operation OP control by an OP 'control operation allowed, namely in the example described here by a pause operation at time to. This advantageously makes it possible to avoid the rejection of the request by the NTSSko server.

This request is then received and processed by the means STR of the NTSS server _k o (step G60), which broadcast to the terminal equipment the required content of the stream FL ₀ from the buffer BUF. In the example described here, a frozen image of the stream at time to is thus broadcast to the terminal equipment STB (execution of the OPO command (step G70).

The various steps described above with reference to FIG. 3C for the OP operation are implemented for each subsequent control operation required by the user U on the FLO flow.

Note that when the control operation OP is included in the request R_act, the steps of checking and possibly replacing the operation required by an authorized operation are implemented in a similar manner, before redirecting the request to control to the NTSSko server

We will now describe, with reference to FIG. 3D, the different steps implemented during the closure of the sessions established for the flow FL ₀ and the terminal equipment STB. These session closures may be the result of different events, such as:

the end of the circular buffer BUF associated with the stream FL ₀ can be reached, following a time offset operation required by the terminal equipment. In this case, the means STR of the NTSS server _k o stop broadcasting the required content of the stream FL ₀ to the terminal equipment and send a RTSP message indicating the end of the buffer (message type

"End of Buffer") to the terminal equipment (alternatively another application protocol may be used). On receipt of this message, the terminal equipment STB sends an R_stop request (FI_o) for deactivation of the control to the redirection server RB (step E50); the user U may wish to manually interrupt the broadcast as part of the flow control FL ₀ to the terminal equipment. In this case, the terminal equipment STB, upon receipt of a command from the user (for example following the support by the user U on a key of the remote control of the terminal equipment STB), sends a request R_stop (FI_o) disabling the control RB redirection server (step E50).

The reception of this deactivation request by the redirection server RB is in itself a detection of a control deactivation event for the data stream FL ₀ for the terminal equipment STB within the meaning of the invention.

Upon detection of such an event, the redirection server RB consults the dynamic database sDB (step F130), to determine the current number of broadcast sessions established by the NTSSko server for the stream FL ₀ , and this, in order to identify if there are other broadcast sessions at the NTSSko server for this stream for other end devices.

If it is determined (step F140) that the terminal equipment STB is the only terminal equipment for which a broadcast session is in progress at the NTSSko server for the stream FL ₀ , then the server RB sends to the means ING of the server NTSSko a request to stop the capture of the flow FL ₀ (step F150).

On receipt of this request, the means ING stop the capture of the stream FL ₀ and send a request to unsubscribe the broadcast of the stream FL ₀ to the router ROUT (step G80). If necessary, the circular buffer BUF associated with stream FL ₀ can also be deleted.

Preferably, stopping the capture of the stream and sending the unsubscription request will only be implemented after a predetermined time interval during which no request from the terminal equipment STB has been received, so to avoid in particular the restarts and untimely stops of FLo flow capture at the NTSS _k o server. On receipt of an acknowledgment message of this stop transmitted by the NTSSko server (step G90), the redirection server updates the database sDB to reflect the closing of the capture session of the stream FL ₀ by the NTSS server _k0 (step F160). It also redirects the stop request R_stop (FI_o) sent by the terminal equipment STB to the means STR of the NTSSko server (step

F170), for these to close the broadcast session associated with the stream

FL ₀ and the terminal equipment STB, and thus stop the broadcast of the stream to the terminal equipment STB (step GlOO).

On receipt of an acknowledgment message of this closure issued by the NTSS server _k o (step GI10), the redirection server updates the database sDB to reflect the closure of the broadcast session of the FLo stream by the NTSSko server. for the terminal equipment STB (step F180). The current number DCurr (kO) of broadcast sessions managed by the NTSS server _k o is thus decremented by 1.

The session established between the terminal equipment STB and the server RB is then terminated (step F190) and the periodic sending of the hold messages stopped. Note further that, in the case where an operator policy has been defined to specify a type of data stream record broadcast by the program strings, the redirection server RB consults the corresponding dynamic base oDB and determines if the relevant data stream is statically captured on the NTSS broadcast server _k o. If so, it does not issue a capture stop request to this server.

The terminal equipment STB can then, if the user U desires, request a new state of the buffer port PORT.

It should be noted that the broadcast and capture sessions, and the control session established between the terminal equipment and the redirection server can also be interrupted due to exceptional and unexpected events. For example :

- the STB terminal equipment can be switched off unexpectedly. In this case, it can no longer respond to the hold messages sent by the RB redirection server. The non-reception of these messages is in itself a deactivation event of the control detected by the redirection server;

during a broadcast session, the means STR can stop broadcasting the required contents of the buffer BUF unexpectedly. In this case, the terminal equipment STB detects the non-reception of a stream of STR means and sends to the redirection server a request to deactivate the control;

during a capture session, the means ING may stop unexpectedly to capture the stream FL ₀ . In this case, the terminal equipment STB detects an abnormal flow sent by the means STR and sends, after a predetermined time interval, a request for deactivation of the control to the redirection server.

Moreover, because of a problem in the telecommunications network 1 or a software and / or hardware problem, it may be that the recording of the stream FL ₀ by the selected NTSSko server is not possible. In this case, the selected NTSSko server sends a non-acknowledgment message (NACK) to the redirection server, which can either select another server or deny access to the nTS control service by the terminal equipment STB for this stream. . It will be noted that in the embodiment described here, the means implemented to carry out the redirection method according to the invention are located on the same device (namely the redirection server RB). As a variant, these means (and the functionalities associated with them) could be distributed over different devices, for example on the RB redirection server and on the broadcast servers.

MSTN.

Furthermore, advantageously, in another embodiment of the invention, it will also be possible to consider, in addition to the plurality of broadcast servers considered previously performing a dynamic capture of the streams, one or more additional broadcast servers adapted to statically capture (permanently) a predefined stream list. It will thus be possible to allocate, for example to these additional broadcast servers, the streams most requested by the subscribers, and systematically redirect (via the redirection server RB) to these servers the control requests issued by a terminal equipment relating to these flows (provided of course that they are not congested). The servers of the plurality of servers previously considered can then be used either to capture and broadcast the least requested streams, or support additional servers when the capacity of these will prove insufficient.

Claims

REVEN DICATIONS

A method for redirecting a control request (R_act) of a data stream (FL ₀ ) broadcast by a source (HE) in a telecommunications network (1), transmitted by a terminal equipment (STB), said characterized in that it comprises:

upon receipt of this request, a step of obtaining (FlO) information representative of a current flow control capability for a plurality (11) of broadcast servers; a selection step (F20), using at least one of this information, of a server (NTSSko) from among said plurality of servers, able to control said stream (FL ₀ ) broadcast by the source;

a step of sending (F30) a capture request (R_cap) of this stream (FL ₀ ) to the selected server if the latter does not already capture this data stream for at least one other terminal equipment; and

a step of redirecting (F70) the control request (R_act) to the selected server.

2. redirection method according to claim 1 characterized in that the information representative of a current capacity of data flow control by a server comprises representative information:

- a current capacity of broadcast sessions of this server; and

- a current stream capture capability of this server.

3. redirection method according to claim 1 characterized in that the selection step takes into account a type of capture of the data stream for at least one broadcast server, said type being selected from at least one type of static capture and a type of dynamic capture.

4. redirection method according to claim 1 characterized in that it further comprises, after the selection step, a step of establishing (F60) a session with the terminal equipment for this data stream, and in that, during the maintenance of this session, at least one other control request (R) issued by the terminal equipment (STB) for this data flow is redirected (F120) to the selected server (NTSS _k0 ).

5. redirection method according to claim 1 characterized in that, during the selection step (F20), the server is selected also according to its proximity to the terminal equipment.

6. redirection method according to claim 1 characterized in that, during the selection step (F20), the server is selected also based on the existence at this server of a capture of the data stream for at least one other terminal equipment.

7. redirection method according to claim 1 characterized in that it further comprises: - a step of detecting a data flow control deactivation event for the terminal equipment;

a step (F140) of determining whether the selected server for the data flow for the terminal equipment captures this data flow for at least one other terminal equipment; if it is not the case, a step of sending (F150) a request for the end of capture of this data flow to the selected server.

8. redirection method according to claim 7, characterized in that it further comprises a step of determining a type of capture of the data stream, said type being selected from at least one type of static capture and a type of dynamic capture, and in that, if it is determined that the capture is of static type, the sending step (Fl 50) of an end of capture request is not implemented.

9. redirection method according to claim 1, characterized in that it comprises, before the redirection of the request for control of the flow of data to the selected server:

a detection step (FI10) that the control request comprises a control operation that can not be implemented by the selected server; and a step of replacing (F120), in the control request, this operation by an authorized control operation.

A computer program comprising instructions for performing the steps of the redirection method according to claim 1 when said program is executed by a computer.

11. Device (RB) for redirecting a request for controlling a data stream broadcast by a source (HE) in a telecommunications network (1), transmitted by a terminal equipment, said device being characterized in that it further comprises:

means of obtaining (21, 24), activated upon receipt of this request, of information representative of a current flow control capacity, for a plurality of broadcast servers; selection means (21), using at least this information, of one of said plurality of servers, able to control said stream (FL ₀ ) broadcast by the source;

means for determining (21,24) whether or not the selected server captures this data stream (FL ₀ ) for at least one other terminal equipment;

means for sending (23) a request to capture this stream of data to the selected server, activated if the latter does not already capture this data stream for at least one other terminal equipment; and

means for redirecting the control request to the selected server.

12. Redirection device according to claim 11 characterized in that it further comprises means for establishing a session with the terminal equipment for this data stream, said redirection means being adapted during the maintenance of this session, to redirect at least one other control request issued by the terminal equipment for this stream to the selected server.