FR2962285A1 - PAIR AUDIO COMMUNICATION - Google Patents

Abstract

In a peer-to-peer communication network comprising a network equipment and a plurality of terminals it is desired to transmit digital content at a transmission rate. An available current value of overall transmission capacity is associated with a current group to which a set of terminals of the network belongs, the current group being adapted to transmit the digital content in the form of portions of digital content, these portions being respectively transmitted by terminals of the current group. At the level of the network equipment, it transmits (23) to a terminal requiring digital content, the list of neighboring terminals. The list of neighboring terminals indicates: - terminals of the current group (203) if the current available value of overall transmission capacity is greater than the transmission rate of the digital content (201), otherwise (202), when terminals of the current group have already been indicated as a list of neighboring terminals to other terminals, terminals of a next group (204) formed by the other terminals.

Description

The invention relates to the field of transmissions in networks, and more particularly in peer-to-peer networks, still referenced peer-to-peer networks or P2P networks. A peer-to-peer network is based on a technology of direct data exchange between computers, or peers, which are interconnected via transmission resources of a network or several physical communication networks. Such a P2P network therefore allows data transfers directly between a plurality of computers without passing through a central server. Such P2P systems allow dissemination of digital contents by direct exchange of corresponding data between peers. In these P2P systems, it is possible to predict the reception of a digital content at a peer, this digital content being transmitted in the form of different portions respectively from several distinct peers. For this purpose, it is expected to cut the digital content into a plurality of portions, each of which is present in several peers. Thus, on the basis of a so-called "overlay mechanism" (or overlay), a peer is able to retrieve digital content from a plurality of peers. .20 We know of such a peer-to-peer system that is described in Xinyan Zhang, Jiangchuan Liu's and Bo Li's Hong Kong University of China's "On Large Scale Peer-To-Peer Live Video Distribution: CoolStreaming and Its Prelimianry Experimental Results." Science and Technology. This system makes it possible to perform streaming (or streaming) of digital content that can correspond to a scene transmitted live (or even "live transmission"). In this document, peers operate in 'pull' mode or 'PULL' mode. According to this mode, unlike a 'PUSH' type mode, peers are in charge of requesting from other peers the data they wish to receive. This document more particularly describes an overlay construction mechanism and a request management mechanism for portions of the digital content, such as a video for example. The overlay construction mechanism employs a random process. Specifically, when a new peer wants to receive the video, it makes the request to a central equipment. The latter provides him with a list of neighboring peers randomly selected from all peers who are already receiving the requested video. Then, this new peer then requires the portions of video to the neighboring peers thus listed. In addition, in addition to the 35 peers provided in the list by the central equipment, a peer can also identify by itself new neighboring peers to complete its list. For this purpose, he asks peers around him to determine for themselves whether they have the video requested. In this context, the neighbors of each peer to whom he can request portions of the desired video, are randomly determined among those who already receive the video. This random peer-to-peer management can offer no guarantee that the neighboring peers to which the new peer requires the video have sufficient resources to transmit the required portions of that video. However, in the case where the peer requires portions of video to a neighboring peer who is not able to provide them under suitable transmission conditions, the quality of the video can be seriously degraded. The present invention improves the situation. A first aspect of the present invention provides a method of transmitting digital content, to be transmitted at a transmission rate, in a peer-to-peer communication network comprising a network equipment and a plurality of terminals; wherein an available current value of overall transmission capacity is associated with a current group to which a set of terminals of the network belongs, said current group being adapted to transmit the digital content in the form of portions of digital content, said portions being transmitted respectively by terminals of the current group; following a request from a terminal requesting the digital content, said method comprises the following steps at the level of the network equipment: / 1 / determining a list of neighboring terminals; and / 2 / transmitting to the terminal said list of neighboring terminals; in which the list of neighboring terminals indicates: - terminals of the current group if the current available value of overall transmission capacity is greater than the transmission rate of the digital content, otherwise, when the current group has already been indicated as a list of neighboring terminals to other terminals, terminals of a next group formed by said other terminals. Here, it is expected that the peer-to-peer network comprises both terminals and a network equipment (or `tracker 'in English) adapted to manage a request for digital content from a terminal of the peer-to-peer network. Thus, in this architecture, when a terminal of the network wishes to receive digital content from one or more other terminals of the network, it first makes the request to this network equipment. This network equipment indicates, in response to such a request for digital content, a list of neighboring terminals that may be able to transmit this digital content.

This list of terminals can correspond to all the terminals of the current group. In this case, the terminal that receives this list of neighboring terminals is responsible for contacting the neighboring terminals listed to identify those that will be able to transmit the portions of the digital content. In the case where the terminal sends a request, it can be provided to indicate a list of terminals by providing respective addresses of these terminals in the network. It can also be expected that this list of neighboring terminals indicate only part of the terminals of the current group. This embodiment may be advantageous for the subsequent steps performed by the terminal receiving the list of neighboring terminals. Such an embodiment can be implemented in particular in the case where the network equipment knows an estimate of the transmission capacity values of the terminals of the group in question. It should be noted further that it is considered here that the digital content is to be transmitted at a given transmission rate. No limitation is attached to the definition of this transmission rate. It can be advantageously defined according to the type of the digital content to be transmitted. This transmission rate may for example correspond to a transmission rate considered nominal, below which the reception quality of the digital content is below an expected quality level. In one embodiment of the present invention, this transmission rate does not vary over time for a given digital content. The term terminal is understood to mean any type of terminal adapted to transmit and / or receive a data stream corresponding to the transmission of digital content. Such a terminal can be a computer, a mobile phone, etc. The terms `digital content 'mean any type of data that can be transmitted over a peer-to-peer network, such as for example a soundtrack, a set of 'images, or a video. Such digital content may correspond to a video taken and transmitted in real time, or still live video, or video in. The terms 'current value available of global transmission capacity' mean a value indicative of a transmission level which may be provide the current group of terminals in its entirety at a given time. This value is called 'current' because it can be evolutionary as a function of time. This current value of capacity may represent the transmission capacity 30 which remains available for the current group. The terms `neighbor terminal list 'denote a list of terminals which are` neighbors of another terminal' in the sense of a peer-to-peer network, ie which are likely to have a live communication with this other terminal. Here, the list of neighboring terminals indicates to the terminal that wishes to receive the digital content, terminals that are adjacent to it in the sense that it can address directly to them to receive the digital content in the form of portions respectively from different neighboring terminals . The transmission of the digital content is performed in portions (or `chunk 'in English), some portions being available in several pairs, to allow reception of the digital content as a whole from a plurality of respective terminals. In order to cleverly determine this list of neighboring terminals, it is here intended to take into consideration both the current available value of overall transmission capacity of the current group considered and the transmission rate of the digital content. By doing so, it is possible to avoid indicating terminals of a group that would not be able to transmit the digital content under acceptable conditions. More specifically, the network equipment is able to decide to indicate terminals of a current group if its current available value of overall transmission capacity is sufficient to ensure transmission of the digital content at a transmission rate. In the opposite case, if the current group has already been indicated as a list of neighboring terminals to other terminals, the network equipment can then advantageously indicate, as a list of neighboring terminals, terminals among these other terminals. Thus, either the current group considered is able to ensure the transmission of the digital content to the terminal the applicant, or it is the terminals that already receive the digital content from the current group that will be indicated in the list of neighboring terminals and, therefore, which will be solicited later by the terminal to receive the digital content. Under these conditions, it is particularly possible to avoid listing, as neighboring terminals, terminals of the current group, in the case where the number of terminals that already receive the digital content from this group is already significant in comparison with the overall initial transmission capacity of the group.

Advantageously, over time and received requests, while ensuring that the transmission rate of the digital content is respected, the network equipment successively generates groups of terminals, which transmit to each other the digital content. Indeed, as long as a current group is able, in view of its current available value of overall transmission capacity, to transmit the digital content again, this current group is in a sense assigned to a terminal transmitting a new request for this digital content. Then, when this is no longer the case, the terminals receiving this digital content from this current group will all be considered as a common group to provide the digital content to the terminals that will require it. Such features allow for sequential and optimized dissemination of digital content in the peer-to-peer network.

In addition, it should be noted that, in the context of a live transmission (or `Live '), all the terminals within the same group thus formed receive almost simultaneously the portions of the digital content. In other words, the terminals of the same group can receive the chunks (or portions of digital content) with a similar latency compared to the time of the encoding at an initial transmission source. Thus, the choice of neighbors to request a chunk is facilitated because they are all part of a group that has chunks assigned the same latency. In the context of a live transmission (or Live) of a video, for example, it is advantageous for the terminals to be virtually synchronized with the source for the display of the video. In other words, they must receive portions of the video with low latency compared to the time of encoding into an initial transmission source. Latency means the period of time that separates an encoding instant at a digital content transmission source from a reception instant at a terminal for the same portion of digital content (or even chunk).

If the neighbors of a terminal are selected randomly, there is a risk that their reception latency compared to the time of the encoding is very variable. As a result, the terminal can only request video from a portion of these peers. Specifically, it requests the lowest latency peer video to minimize its own latency. This results in a dispersion of the display time of the video which considerably reduces the interest of a live broadcast for an event. Such a method can therefore advantageously be iterative in the sense that terminals of a current group are provided as a list of neighboring terminals as long as the transmission capacity of this group allows it. As soon as this capacity proves to be insufficient, a next group is then created to be provided, at least partially, as a list of neighboring terminals thereafter, as long as the transmission capacity of this group allows it with respect to the transmission rate of the digital content considered. This method can be repeated over time and thus allow optimal transmission of terminal group digital content into terminal groups in the peer-to-peer network. In order to be able to apply this transmission method in a peer-to-peer network, in one embodiment of the present invention, it can be provided that, when the list of neighboring terminals indicates terminals of the next group, the following group is considered as than current group for next execution of step / a /. Thus, the next request for digital content received by the network equipment will receive in response a list of neighboring terminals corresponding to terminals of this new current group.

It should be noted that an available current value of overall transmission capacity is associated with the current group considered so as to reliably determine the list of neighboring terminals to be transmitted in response to a new request. In one embodiment of the present invention, this current value is updated over time as a function of the change in the number of terminals at which the network equipment indicates the current group as a list of neighboring terminals. It is thus advantageously possible to provide that the network equipment reduces the current available value of overall transmission capacity by a value representing the transmission rate of the digital content each time the current group is indicated as a list of neighboring terminals to a terminal. Thus, by updating in this manner the current available value of overall transmission capacity, it is possible to ensure a relevant evolution of the dissemination of the digital content in the peer-to-peer network. No limitation is attached to an initial value assigned to the current group even before terminals of this group are indicated as a list of neighboring terminals at any terminal in the network. For example, it is possible to determine an initial value of overall capacity of the current group as a function of the number of terminals belonging to this current group, for example by considering an estimated average value of the transmission capacity per terminal. One can also consider recovering a transmission capacity value of each terminal component of the current group. Be that as it may, no limitation is attached to the mechanism used to obtain this capacity value per terminal of the network. In addition, no limitation is attached either to the mechanism implemented at the terminal to ask the terminals of the list of neighboring terminals respective portions of the digital content. It is for example possible for the terminal to apply for this purpose a random selection of terminals in the list of neighboring terminals received. In one embodiment of the present invention, it can be provided that each request indicates a transmission capacity value of the terminal that issued the request. Then, when the list of neighboring terminals indicates terminals of the next group, the method may then comprise the following steps: / i / consider the next group as a current group; and / ii / assigning to said current group an available current value of overall transmission capacity equal to the sum of the transmission capacity values of the terminals of the current group. The knowledge of the transmission rate available in a terminal is outside the scope of the invention. The terms 'emission' and 'transmission' are used interchangeably.

By doing so, the network equipment can be informed of the transmission capacity of each terminal that makes a request for digital content. It can then sum the capacity values of each of the terminals that make up a current group to obtain an initial value of overall transmission capacity of the current group that is representative of the actual conditions at a time t, even though the latter are evolving in the time. The term `transmission capacity value 'means a value which indicates the data transmission capacity of a terminal, that is to say the characteristics of this terminal with respect to data rates that it is able to transmit. The transmission capacity of a terminal may depend on various parameters. No limitation is attached to the type of parameters that can be taken into account in determining such a value. In one embodiment, provision can be made for this transmission capacity value to be expressed in the form of a decimal number representing the number of times the terminal can transmit to the transmission rate of the digital content. In the context of the present invention, it is possible to provide that the network equipment manages a current value of transmission capacity which represents a value of transmission capacity evolving over time. Thus, in one embodiment of the present invention, the network equipment knows a current value of transmission capacity of each terminal from which it receives a request. The current transmission capacity value of a terminal is updated from an initial transmission capacity value of the terminal each time the terminal is indicated in a list of neighboring terminals. Thus, the network equipment knows an initial transmission capacity value for each terminal from which it has received a request for the digital content. Then, over the requests received later, the equipment can maintain a current value of transmission capacity for these terminals. By thus disposing of the current values of transmission capacity of the terminals, the network equipment is advantageously able to build a list of neighboring terminals targeted in the sense that it can really select terminals of the current group considered which have the capacity to transmit the terminal. digital content at best.

It may be provided in one embodiment of the present application that the digital content is initially transmitted by a transmission source. Thus, in one embodiment of the present invention, the peer-to-peer network includes a source for transmitting digital content having an initial value of overall transmission capacity. The network equipment then updates an available current value of overall transmission capacity of said transmission source at each request reception, and it indicates said transmission source as a list of neighboring terminals as long as the current available capacity value overall transmission is greater than the transmission rate of digital content; the terminals receiving the digital content from said transmission source then composing the first current group of terminals. By doing so, it is advantageously possible to shift the transmission load of the required digital content from the initial transmission source step by step, from terminal group to terminal group, while guaranteeing quality transmission in an even network. to peer. This first group of terminals is the one that suffers the lowest latency with respect to the source. In comparison, the state of the art with a random choice of the neighbors does not guarantee that they have a coherent latency to allow the selection by the requesting terminal (that is to say the receiving terminal of the content digital) of neighboring terminals with the lowest latency. On the contrary, an application of the present invention allows a grouping of the first requests in a first group, whose terminals have homogeneous and minimal latencies. Such a grouping makes it possible to considerably reduce the dispersion of the reception delays in a group, and offers a better guarantee of obtaining the chunks during queries distributed among all the neighboring terminals. In one embodiment of the present invention, it is intended to manage a possible failure of a terminal which has been indicated as a neighboring terminal in a list of neighboring terminals. In this case, the transmission method may further comprise the following steps: identifying a failed terminal among the terminals indicated in a list of neighboring terminals belonging to a given group; - In replacement of the failed terminal, indicate at least one terminal of the next group, which follows the given group, at least one neighboring terminal selected from a terminal of the given group and a terminal of the group preceding the given group. Here, it is advantageously planned to replace the neighboring terminal in breakdown by another terminal, in order to continue to guarantee the transmission rate of the digital content to the group of terminals that follows the given group to which the failed terminal belongs. The terminal replacing the one that has failed in a given group may be chosen: - either among the other terminals of the given group in the case where at least one terminal of the given group still has sufficient transmission capacity to replace the terminal of the same group that broke down; or among the terminals of the group that precedes the given group in which the terminal has failed. This choice of replacement may especially be advantageous in the case where the storage duration of the portions of digital content is greater than the latency between two consecutive groups. It may also be provided that the network equipment indicates to a terminal requesting the digital content only a portion of the resources available in a given group as a list of neighboring terminals in order to conserve transmission resources in the given group, avoiding soliciting some terminals of the given group, for use in case of failure of one or more terminals of the given group. In one embodiment, when a fault is identified on a terminal among the terminals indicated in a list of neighboring terminals belonging to a given group, the number of neighboring terminals indicated in the list is reduced as long as the sum of the current values of transmission capacity of the neighboring terminals of the list is greater than or equal to the transmission rate. We can thus possibly continue to provide the digital content despite a failure. A second aspect of the present invention provides a network equipment that includes means adapted for carrying out a transmission method according to the first aspect of the present invention.

A third aspect of the present invention provides a peer-to-peer network comprising a network equipment according to the second aspect of the present invention and terminals. A fourth aspect of the present invention provides a computer program including instructions for carrying out the method according to the first aspect of the present invention, when the program is executed by a processor.

A fifth aspect of the present invention provides a recording medium on which the computer program according to the fourth aspect of the present invention is stored. Other features and advantages of the present invention will appear in the detailed description below, made with reference to the accompanying drawings in which: Figure 1 illustrates a peer-to-peer communication network adapted for implementing a mode of embodiment of the present invention; Figure 2 illustrates the main steps of a communication method according to an embodiment of the present invention; Figure 3 illustrates latencies between different group of terminals according to an embodiment of the present invention; Figure 4 illustrates terminal groups of a peer-to-peer network according to an embodiment of the present invention. FIG. 5 illustrates the evolution of coefficients allocated to terminals belonging to a group Gi when new terminals connect to the peer-to-peer network; Fig. 6 illustrates the present invention in its application to a failure case in one embodiment; Fig. 7 illustrates a network equipment according to an embodiment of the present invention.

FIG. 1 illustrates a peer-to-peer communication network, or P2P network, adapted for carrying out an embodiment of the present invention. This P2P network comprises a plurality of terminals 101 and a network equipment 102 according to an embodiment of the present invention. This network equipment 102 is adapted to receive requests for digital content from the various terminals 101 of the network.

Figure 2 illustrates the main steps of a method of transmitting digital content according to an embodiment of the present invention. Here, it is planned to implement the steps of receiving a request from a requesting terminal and determining the list of neighboring terminals. This is an example of an application, but it is conceivable that these two steps of receiving request and determining list are performed on one or more other network equipment. The digital content is to be transmitted at a transmission rate. The digital content is to be transmitted at a transmission rate. This transmission rate can be determined according to the quality that is desired in reception. By defining this transmission rate associated with this digital content, it is thus possible to set a minimum threshold for transmission quality and therefore for receiving this digital content. In one embodiment of the present invention, the transmission rate is defined for a given digital content in a fixed manner over time. It should be considered that a real-time digital content is to be transmitted in a limited time. In other words, the transmission rate corresponding to a chunk can be known in advance, given the duration of the video fragment that it contains, and its amount of information. The video in question can be encoded under different types of coding. It can be encoded for example in CBR (Constant Bit Rate) mode. In this case, the transmission rate is strictly constant. It can also be provided to encode it in a variable bit rate (VBR) encoding. In this case, the encoding is constrained with a maximum nominal bit rate. In this context, it is then possible to reduce the amount of information, as well as the bit rate, if, for the same encoding quality, the encoder can compress the information at a lower bit rate.

In one embodiment of the present invention, it is then possible to always consider, for the configuration of the groups, a peer broadcast of the chunks at the predefined nominal bit rate of the video. In this case, when the data volume is lower for some chunks, these chunks can then be transmitted in a shorter transmission time.

Thus, the neighboring terminal that transmits these chunks may release some of its broadcast resources faster than expected. He is then able to respond a little more quickly to requests for chunks that he has accepted. We place ourselves here at a moment when a current group G; terminals is adapted to transmit the digital content in portions respectively from the terminals of the current group, taking into account the overall transmission rate of the group, and the nominal transmission rate of the video. At a time considered here, an available current value of overall transmission capacity is associated with a current group G; which belongs to a set of terminals of the network.

At the network equipment 102, at a step 21, a request from a new terminal, 101-R, requesting the reception of the digital content is received. Then, upon receiving this request, the network equipment 102 determines in a step 22 a list of neighboring terminals. This step 22 comprises a test 200 which consists in checking whether the current available value of overall transmission capacity of the current group G; is greater than the transmission rate of the digital content. In other words, this test 200 consists of determining whether there is still enough transmission capacity at the current group G; to ensure the transmission of the digital content to the terminal 101-R that issued the request being processed. If this test is positive, then a list A, k of neighboring terminals corresponding to terminals of the current group G, is entered at step 203. The list A; k of neighboring terminals may contain all or some of the terminals of the current group G ;. The index i of the list A;, k corresponds to the index i of the group G; from which is extracted this list A;, k, and the index k (integer) refers to the terminal to which this list is transmitted. Indeed, for a group G ;, it will be emphasized that this list A;, k is not fixed but can change with each new request for content. In fact, the neighboring terminals selected from the terminals of the group G; in response to a content request are not necessarily the same as the neighboring terminals selected from the terminals of the group G; in response to another content request. In the opposite case, that is to say if the current value of overall transmission capacity of the current group G is available; turns out to be insufficient, then the current group G; will be replaced by a next group G1 + 1 which is composed of terminals 101 analogous to the terminal 101-R, which has previously been indicated a list A1, k of neighboring terminals of the current group G1 as a list of neighboring terminals. This group following Gi + 1 then becomes the new current group for processing the following requests for receiving the digital content transmitted by terminals 101. The list of neighboring terminals Al + 1, k then corresponds to all or part of the terminals 101 of the group following at a step 204. Then, in a step 23, the list of neighboring terminals A;, k (if the test 200 is positive) or (if the test 200 is negative) is transmitted to the terminal 101-R having issued the request . The present invention can be implemented on the basis of transport protocols such as RTP / UDP thus making it possible to respect the real time. As an illustration, the following sections describe the present invention in its application to the transmission of digital content corresponding to a program that is to say live. In this context, the terminal users do not seek to obtain the digital content at its beginning, but closer to the present moment of encoding at the source of transmission. Thus, the latency in this context is a period of time separating the encoding at the source of the reception of the same chunk (or the same portion). Subsequently, X, refers to the latency affecting the terminal group G1, G, comprising a number Ni of terminals. In one embodiment, from the initial transmission capacity of the transmission source of the digital content, it is possible to create successive groups of terminals, the terminals of the same group undergoing the same latency with respect to the source. , in the case where the delays introduced in the transmission network are neglected. Thus, a first group G1 may be composed of terminals powered simultaneously by the transmission source (except transmission delays). Once this group G1 is constituted, that is to say when it is estimated that the transmission resources of the source are exploited, it can in turn feed a next group G2 having terminals wishing to receive the video. The next group G2 is formed when it is estimated that the transmission resources of the previous group G1 are exploited. In the prior art, P2P solutions typically rely on a random approach, which does not allow any optimization of network resources. These conventional solutions lead either to an over-dimensioning of the network, or to an inability to transmit in time all chunks (or portions) requested by a terminal. No limitation is attached to the manner of representing transmission capabilities in the context of the present invention. For example, these capacities can be expressed as a flow rate value. They can also be expressed in decimal form as a multiple of the transmission rate associated with digital content, for example. Thus, in one embodiment of the present invention, the transmission capacity values are coefficients which represent the number of times that a terminal or group of terminals can transmit the bit rate of the digital content. When the network equipment receives a request for the digital content indicating such a coefficient for the terminal transmitting the request, it stores this coefficient in association with this terminal. In other words, this coefficient represents, for a terminal considered, the number of terminals at which the terminal considered can transmit the digital content. This coefficient can be a decimal number representing a number of terminals, and therefore not only an integer number of terminals for which the transmission of the digital content can be done from the terminal in question. It can be provided that the terminal indicates only a part of its bit rate in the transmitted request, in order to preserve resources for signaling messages for example or other. If the list in a group is large enough, the use of decimal numbers makes it possible to retrieve fractions of available bit rates in a group to constitute a global resource sufficient for the transmission of the video to a new peer. On receiving the list of neighboring terminals in response to its request, the terminal can then contact the listed terminals to receive the chunks of the video or digital content. Of course, the terminal can ask the terminals listed only chunks they have already received. These chunks allow him to watch the video with a latency compared to that experienced by the terminals of the current group. This latency corresponds at least to the duration of a chunk, and, to be more precise, its delay of reception and transmission. The first group of terminals that require the digital content to the peer-to-peer network receive the video from the live transmission source (or `live server ') and thus experience relatively low latency compared to the encoding. The overall transmission capacity of a group Gi, denoted Cap ;, makes it possible ultimately to define a maximum number of terminals that can receive the video, or more generally the digital content, from the terminals of this group G1. Terminals of the same group G; all experience the same latency (with the exception of chunks transmission and reception delays) compared to encoding since the terminals of the previous group Gi_1 (that is, their providers) have the same latency. Figure 3 illustrates latencies between different groups of terminals according to an embodiment of the present invention. An initial source of transmission of digital content has transmitted the chunked portions: Cx, Cx + 1, Cx + 2, Cx + 3, Cx + 4. The source is transmitting the next chunk: Cx + s- The first group of terminals G1, according to one embodiment, has received chunks Cx, Cx + 1, Cx + 2, Cx + 3. The chunk Cx _,. 4 is being received by the group G1.

The second group of terminals G2 received chunks Cx_2, Cx_I, Cx, Cx + 1, Cx + 2. The chunk Cx + 3 is being received by the group G2. The third group of terminals G3 received chunks Cx_3, Cx_2, Cx-1, Cx, Cx + 1. The chunk Cx + 2 is being received by the G3 group. It may be noted that the terminals of a given group G 1, each experiencing the same latency, can send only the chunks they have already received. The terminals of the group Gi + 1 will therefore have a higher latency than that experienced by the terminals of the group G; This latency, as shown in Figure 3, is at least equal to the duration of a chunk. An initial transmission source of the video (or Live server) is the only device in the system that does not experience latency with respect to encoding. It is referred to as a Go group and an initial value of Capo transmission capacity corresponds to it. In order to make the best use of the live server resources without however congesting it, the network equipment indicates this server as a list of neighboring terminals for the first No terminals that require the digital content. When the transmission capacity is expressed in the number of terminals that can be supplied with digital content by the transmission source, it is then possible to write: No = Capo These terminal numbers constitute the first current group G1, in which the terminal numbers have a latency XI with respect to the encoding and a value of Cap1 overall transmission capacity.

Then, this group GI is transmitted as a list of neighboring terminals to the next terminals requiring the digital content. It can provide them as a list of neighboring terminals to the next Ni terminals that will issue a request. If the transmission capacity is expressed in the number of terminals to which the digital content can be supplied, then we have: N1 = Capi The Ni terminals receiving the digital content from the first group constitute a second group G2, having a latent X2 and a number Ni of terminals. This process is iterative on the basis of the same principle as that stated above. FIG. 4 thus illustrates groups of terminals of a peer-to-peer network according to one embodiment of the present invention.

For j integer ranging from 1 to i + 1, a group GG has a latency of Xj and a number of terminals M_1, N ~ _1 corresponding to the initial value of the transmission capacity of the group Gi_1 expressed in number of terminals. Here, it is therefore considered that each terminal P3, k (k integer ranging from 1 to the maximum number of terminals for the group to which this terminal belongs) has the same value of available initial transmission capacity, which can change as a function of time. A group of terminals on the basis of which a list of neighboring terminals is indicated to a new terminal 101, has the ability to provide the video to this new terminal. In other words, the sum of the coefficients of the terminals of the group is greater than or equal to 1. Either the network equipment is able to determine the terminals of the current group G; which can provide the overall digital content at the expected transmission rate (this may be the case if the network equipment maintains an indication of transmission capacity for each terminal of the current group), or it indicates the current group G ; as a whole, as a list of neighboring terminals. Then, it can be envisaged that the terminal 101 which receives a list of neighboring terminals randomly selects the terminals to which it will require the portions of digital content. These queries have a very high probability of success on the presence of chunks, because the group is coherent in latency. It can also be envisaged that, in the case of a refusal of a neighboring terminal, the requesting terminal interprets it as a neighboring terminal overhead and then decides to send a new request to another terminal. Such a mechanism allows a distribution of the flows in the group. In the following, an application of the present invention is envisaged in the case where the network equipment maintains a current value of transmission capacity for the terminals from which it has received a request. In the case where the list of neighboring terminals comprises a number L of terminals of the current group, it should be noted that the terminals indicated as neighbors have a transmission capacity value greater than or equal to 1 / L preferably. Such a random selection makes it possible to ensure a load balance between the members of a given group as a list of neighboring terminals. Each of the selected terminals has its coefficient which is then reduced by a value of 1 / L. Figure 5 illustrates the evolution of the coefficients assigned to the terminals belonging to the group Gi when new peers connect to the system. At a given instant T, the terminals of the group Gi have the following transmission capacities, the size of the list being L: - for P; : 0 - for P;, i + i: 3 / L for P; ,, J + 2: 3 / L 35 - for Pi j.1-3 1 / L for Pi ,,. 4: 3 / L

for Pi j-1-n_2 3 / L - for PiJ + ni: 2 / L - for Pi j + n: 5 / L where n is a positive integer, n is greater than L, representing the number of terminals in the group BOY WUT;. When the network equipment indicates, in response to a set request, the group G, it reduces the current available value of overall transmission capacity by the value 1 / L. In the following sections, L is equal to 6. The terminal transmitting the request regl requests the transmission of the digital content to L terminals which are the following: Pi J, 1, Pif + L, PiP, j + n, Pij + n- In a preferred embodiment, the list is obtained by random draw among the peers of the group having the sufficient transmission rate. Then, when the network equipment indicates, in response to a request req2, the group G i, it reduces the current value of the overall transmission capacity of the value 1 / L. Then, the transmitting terminal of the request req2 requests the transmission of the digital content to L terminals which are the following: P,, H, Pif + 2, Pi J + 3, Pi, i + 4, Pij + n-2, Pi, j + n-1. In some cases, the size of the list of neighboring terminals may be reduced to avoid providing unavailable terminals. For example, a list of size K smaller than L may be defined, provided that the coefficient of each terminal selected for this list of neighboring terminals is then greater than or equal to 1 / K. In another embodiment, if the number of available peers in a group is less than L, it is also possible to select a number of neighboring terminals smaller than L the number of neighboring terminals a priori contained in a list of terminals. neighbors, taking in each of these terminals transmission resources of value i / L (i positive integer) so that the sum of i / L, is equal to 1. For example, we can take on three respective terminals d the same group, the following coefficients: 2 / L, 1 / L, 3 / L, siL = 6. This selection mode makes it possible to take into account the actual available bit rate for each of the 30 terminals already present in the peer-to-peer network, which is particularly important in ADSL type networks for example, since there can be a significant disparity in the rising speeds of the terminals. An application of the present invention therefore allows dissemination of a digital content, such as for example a live program by management of successive groups. 16 The optimization of. the overlay latency described in one embodiment of the present invention reduces the delay between encoding the video and viewing it by the users. In one embodiment, it can be provided that the terminal, which has received a list of neighboring terminals in response to its request, periodically exchanges control messages with the terminals of the list. In response, each terminal thus requested sends him a detailed description of his chunks. The terminals of this list belonging to the same group and therefore having the same latency with respect to the encoding, have substantially the same chunks. It is possible, according to such a mechanism, that there are several terminals receiving the same list of neighboring terminals of the network equipment. In order to distribute the load between neighboring terminals and allow all terminals to receive the digital content in good conditions, it may be advantageous to limit the number of requests that several terminals can send at the same time to a given neighbor terminal. In order to speed up receiving chunks without overloading a given neighbor terminal, the requesting terminal can dispatch its chunks requests to several neighboring terminals, requiring only one chunk at a time. If the chunks are available at several neighboring terminals of the list, it is then possible to apply a mechanism favoring an equitable distribution of queries chunks, such as a mechanism like Round Robin or uniform distribution random law. If each of the terminals of the next group Gi + 1 applies such a chunks request distribution mechanism, towards the neighboring terminals of the group Gi, then the transmission load is balanced between all the terminals of the group Gi. In an embodiment of the present invention, in the case where a neighboring terminal of the list goes down, if the list of neighboring terminals indicated more terminals than necessary for the transmission of the digital content, then the requesting terminal can then choose another terminal of the list of neighboring terminals to replace the failed terminal. It is also possible to provide that one solicits either a terminal of the group to which the faulty terminal belongs but which has not been indicated in the list of neighboring terminals, or a terminal of the group preceding that to which the terminal belongs. breakdown. Indeed, here, the terminals that receive the digital content in the system are supposed to keep the chunks for a much longer time than the delivery time to the next group. Therefore it is also able to provide chunks to receptors at later constituted groups (see Figure 3). Thus, it is furthermore possible to provide the video to a group G; from a terminal of group Gi_2 also.

In the case where a terminal of group G; .1 is out of order, that is to say that it no longer asks for chunks in group G; _2 and that it no longer provides chunks to the terminals it feeds, there are two consequences: a loss of flow resources to feed the group G1, and a release of part of the transmission resources of the group Gi_2. In the case where the group G; _2 has chunks which are likely to interest the group G ;, it is then advantageously possible to transfer chunks directly from the group Gi_2 to the group G1.

In this case, it is advisable to ensure that a terminal of group Gi_1 which has failed is replaced by a terminal or several terminals of group Gi_2 which have transmission capacity values at least equivalent to that of the failed terminal. It is possible that terminals receiving the digital content are not selected in a group to be provided in the list of neighboring terminals, for the following reason: they have globally a residual of transmission capacity insufficient to supply a new peer. It can then be expected in case of failure to still exploit their transmission resource to recover the missing flow. In general, in case of failure, the network equipment 102 advantageously solicits terminals that still have chunks that the terminals affected by the failure were able to transmit. These terminals can therefore be terminals of the preceding group that were not selected in the list of neighboring terminals because of their transmission rate too low for example, or terminals of the previous group. There may therefore be in different groups terminals capable of providing a portion of the digital content to a terminal of the group G; when a terminal of group Gi_1 is down. In this case the network equipment starts by building the list with terminals that have a transmission rate available in the group G; _1. If the sum of the potential transmission capacities of these terminals is smaller than that of the terminal which has failed, then the network equipment completes the list by terminals of the group Gi-2. Fig. 6 illustrates the present invention in its application to a failure case in one embodiment. Gi [Xi, Nk] is a group of size N and latency Xi. Cap is the overall transmission capacity of the group and Disp is the remaining capacity, or current capacity of the group considered, or available capacity.

At a time t, the group G1 has the chunks: C1 to C5; group G2 has chunks: C1 to C4; group G3 has chunks: Cl to C3 and group G4 has chunks: Cl to C2. At this instant t, G1 is defined by X1, NO, a global capacity Cap = N1, and a Disp value of 0.5; G2 is defined by X2, N1, a global capacitance Cap = N2, and a Disp value of 0.2; G3 is defined by X3, N2, a global capacitance Cap = N3, and a Disp value of 0.3; G4 is defined by X4, N3, a global capacitance Cap = N4, and a Disp value of N4. A failure occurs at the G3 group level. It is then possible to transmit the chunk C2 to a requesting terminal of the group G4 from the group G1, which still has a Disp of value 0.2. In this particular embodiment, a majority of the G4 group receiving terminals continue to receive its G3 chunks. However, the receiving terminals that are affected by the failure in the group G3 can then receive chunks from neighboring terminals belonging to the group G2 and / or G1. By doing so, it is possible to recover rate residues and perform overlays based on a redundancy of chunks that can be provided by neighboring terminals that belong to several groups. In one embodiment of the present invention, the network equipment may knowingly consider that some terminals may be part of the group G; are not part of the list of neighboring terminals, in order to have a transmission resource in case of failure in this group G;

We can consider keeping as a backup resource in each group Gi a percentage around 10% resource not included in the group. Fig. 7 illustrates a network equipment 102 according to an embodiment of the present invention. This network equipment 102 is adapted to implement those of the steps of the method just described and which are carried out by the equipment 102.

Such network equipment 102 comprises: a reception unit 61 adapted to receive a request from a terminal requesting the reception of the digital content; a determination unit 62 adapted to determine a list of neighboring terminals; and a transmission unit 63 adapted to transmit to said terminal said list of neighboring terminals. The reception unit 61 is arranged to implement the step 21 of the previously described method. The transmission unit 63 is arranged to implement the step 23 of the previously described method.

The determining unit 62 comprises a control module for: deciding that the list of neighboring terminals indicates terminals of the current group if the current value of the overall transmission capacity is greater than the transmission rate of the digital content, and if not, in the case where terminals of the current group have already been indicated as a list of neighboring terminals to other terminals, to decide that the list of neighboring terminals indicates terminals of a next group formed by said other terminals.

The determining unit 62 is thus arranged to implement the substeps 201 to 204 of the step 21. In one embodiment of the present invention, when the list of neighboring terminals indicates terminals of the next group, the determining unit 62 then considers the next group as a current group.

The network equipment 102 may be adapted to reduce the current available global transmission capacity value by a value representing the transmission rate of the digital content each time terminals of the current group are indicated as a list of neighboring terminals at one time. terminal. The network equipment 102 may furthermore comprise an update unit 64 of current transmission capacity value of each terminal from which it receives a request 21; said current transmission capacity value of a terminal being updated, from an initial transmission capacity value of the terminal, whenever said terminal is indicated in a list of neighboring terminals.

Claims (16)

REVENDICATIONS1. A method of transmitting digital content, to be transmitted at a transmission rate, in a peer-to-peer communication network comprising a network equipment (102) and a plurality of terminals (101); wherein an available current value of overall transmission capacity is associated with a current group (G,) to which a set of terminals of the network belongs, said current group being adapted to transmit the digital content in the form of portions (C ') of digital content, said portions being respectively transmitted by terminals of the current group; following a request (21) from a terminal requesting the digital content, said method comprises the following steps at the level of the network equipment: / 1 / determining (22) a list of neighboring terminals; and / 2 / transmitting (23) to said terminal said list of neighboring terminals; the list of neighboring terminals indicating: terminals of the current group (G ;, 203) if the current available value of overall transmission capacity is greater than the transmission rate of the digital content (201), otherwise (202), when terminals of the current group have already been indicated as neighboring terminals to other terminals, terminals of a next group (204) formed by said other terminals. A transmission method according to claim 1, wherein, when the list of neighboring terminals indicates terminals of the next group, the next group is considered as the current group for next execution of the steps / 1 / to / 2 /. The transmission method according to claim 1, wherein the network equipment reduces the current available global transmission capacity value by one value representing the transmission rate of the digital content each time terminals of the current group are indicated as that list of neighboring terminals to a terminal. The transmission method according to claim 1, wherein the network device knows a current value of transmission capacity of each terminal from which it receives a request from the terminal requesting the digital content, said current value of transmission capacity of a terminal. terminal being updated from an initial transmission capacity value of the terminal, whenever said terminal is indicated in a list of neighboring terminals. The transmission method of claim 1, wherein each request indicates a transmission capacity value of the terminal that issued the request; and wherein, when the list of neighbor terminals indicates the next group, the method comprises the steps of: / i / considering the next group as a current group; and / ii / assigning to said current group an available current value of overall transmission capacity equal to the sum of the transmission capacity values of the terminals of the current group. A transmission method according to claim 1, wherein the peer-to-peer network comprises a digital content transmission source having an initial value of overall transmission capacity, wherein the network equipment updates a current global capacity value. said transmission source at each request reception; and wherein the network equipment indicates said transmission source as a list of neighboring terminals as long as the current available value of overall transmission capacity is greater than the transmission rate of the digital content; terminals receiving the digital content from said transmission source comprising the first current group of terminals. The transmission method of claim 1, further comprising the steps of: identifying a failed terminal among the terminals indicated in a list of neighboring terminals belonging to a given group; - In replacement of the failed terminal, indicate at least one terminal of the next group, which follows the given group, at least one neighboring terminal selected from a terminal of the given group and a terminal of the group preceding the given group. 8. The transmission method according to claim 1, wherein, when a fault is identified on a terminal among the terminals indicated in a list of neighboring terminals belonging to a given group, the number of neighboring terminals indicated in the list is reduced. the sum of the current transmission capacity values of the neighboring terminals of the list is greater than or equal to the transmission rate. 9. Network equipment in a peer-to-peer communication network adapted for transmitting digital content, to be transmitted at a transmission rate, said network further comprising a plurality of terminals; wherein an available current value of overall transmission capacity is associated with a current group (G;) to which a set of terminals of the network belongs, said current group being adapted to transmit the digital content in the form of portions (C ') of digital content, said portions being respectively transmitted by terminals of the current group; said network equipment comprising: - a determination unit (62) adapted to determine (22) a list of neighboring terminals, following a request (21) from a terminal requesting the digital content; and - a transmission unit (63) adapted to transmit (23) to said terminal said list of neighboring terminals; wherein the determining unit comprises means for deciding that the list of neighboring terminals indicates terminals of the current group (203) if the current available value of overall transmission capacity is greater than the transmission rate of the digital content (201), and otherwise (202), when terminals of the current group have already been indicated as a list of neighboring terminals to other terminals, to decide that the list of neighboring terminals indicates terminals of a next group (204) formed by said other terminals. The network equipment of claim 9, further comprising: a receiving unit (61) adapted to receive (21) a request from a terminal requesting the reception of the digital content; and a determining unit (62) adapted to determine (22) a list of neighboring terminals. 11. Network equipment according to claim 9, wherein, when the list of neighboring terminals indicates terminals of the next group, the determination unit then considers the next group as a current group. The network equipment according to claim 9, wherein the network equipment is adapted to reduce the current available value of overall transmission capacity by a value representing the transmission rate of the digital content whenever terminals of the current group are indicated by as a list of neighboring terminals to a terminal. Network equipment according to claim 9, comprising an update unit (64) of current value of transmission capacity of each terminal from which it receives a request for digital content; said current transmission capacity value of a terminal being updated, from an initial transmission capacity value of the terminal, whenever said terminal is indicated in a list of neighboring terminals. A peer-to-peer communication network comprising network equipment according to claim 9 and terminals. 15. Computer program comprising instructions for implementing the method according to claim 1, when this program is executed by a processor. 16. Recording medium on which the computer program according to claim 15.20 is stored.