FR2779019A1 - METHOD AND DEVICE FOR TRANSMITTING DATA, METHOD AND DEVICE FOR RECEIVING DATA - Google Patents

Abstract

A method of transmitting user data over a switched network between a "source" node (10) having a unique identifier and a "destination" node (50), in which the source node determines additional data defining in particular, in its entirety, the path to be followed on said network, by said user data, the additional outgoing data being, moreover, representative of said unique identifier of the source node.On reception of each packet, the destination node reads said identifier and checks that the data has been correctly received and returns data representative of the logical channel followed, on the outward journey, by the user data.

Description

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  The present invention relates to a method and a device for transmitting data, a method and a device for receiving data and

  systems implementing them.

  In currently known switched network transmission methods: - packet switching protocols such as ATM protocols (initials of the English words "Asynchronous Transfer Mode" meaning, in French, "asynchronous transfer mode") or X25, are too complex to be implemented and used in local networks, and - low-level packet switching protocols, such as the "IEEE 1355" protocol do not provide all the qualities expected of a

  network transmission (priority, sharing of reliable and unreliable modes, ...

  The present invention intends to remedy these drawbacks.

  In general, the present invention consists in combining the means and the advantages of packet routing at the source (known by the English name of "source routing") and the transmission of an address of the node which transmits the packet on said network, in the header of the packet, to make the transmission more reliable by allowing the node receiving the packet

  send, in return, an acknowledgment of receipt of the packet.

  Thus, the present invention relates, according to a first aspect, to a method of transmitting user data over a switched network between

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  a so-called "source" node having a unique identifier on said network and a so-called "recipient" node, a method comprising, carried out by the source node: - an operation of determining additional outgoing data defining in particular, in its entirety, the path to be followed on said network, by said user data, and - an operation of transmission, by the source node, of at least one packet of said user data and said additional outward data which are related thereto, characterized in that : - during the operation of determining additional outward data, the source node defines additional outward data representative of said unique identifier of the source node, and - the method comprises, carried out by the destination node, upon receipt of each packet: * an operation of reading said identifier in said additional data to go, and an operation of checking for good rec eption of user data and, in the event of good reception: 20. an operation for determining additional return data defining in particular a path going from said recipient node to the node identified by said identifier, and an acknowledgment operation by sending data from acknowledgment indicating good reception of said user data and of said additional return data. According to a second aspect, the present invention relates to a method for transmitting user data over a switched network implemented by a node called "source" having a unique identifier on said network for transmitting user data to a node called "recipient" ,

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  method comprising: an operation for determining additional outward data defining in particular, in its entirety, the path to be followed on said network, by said user data, and an operation for transmitting, by the source node, at least a packet of said user data and said additional outward data relating thereto, characterized in that the additional data determined during the operation of determining additional data are

  representative of said unique identifier of the source node.

  According to a third aspect, the present invention relates to a method of receiving, by a node called "recipient", user data on a switched network, data coming from a node called "source" having a unique identifier on said network, characterized in that that it comprises, on receipt of each packet coming from the source node, and carried out by the destination node: an operation of reading an identifier in additional data to be transmitted, in said packet, with user data, and e an operation for verifying good reception of user data and, in the event of good reception: an operation for determining additional return data defining in particular a path going from said destination node to the node identified by said identifier, and an acknowledgment operation by transmission of acknowledgment data indicating the good reception of said user data and said data has Additional returns. Thanks to the provisions of each aspect of the present invention, the source node is informed of the good reception of the data

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  transmitted user, or else, when it does not receive acknowledgment data, it may assume that the user data it has transmitted has not been correctly received. In the latter case, it can implement various procedures intended to correct, at least partially, the failure to transmit the packet, such as, for example, the repeated transmission of the transmitted packet.

  The invention therefore makes it possible to make a switched network reliable.

  According to particular characteristics - during the operation of determining additional outward data, the source node defines additional outward data representative of the virtual channel that said user data must follow, - during the operation of determining of additional return data, the destination node determines additional return data representative of the virtual channel that the acknowledgment data must follow, and / or - during the operation of determining additional return data, the destination node incorporates to the additional return data a virtual channel identifier represented by

  additional data received from the source node.

  Thanks to these provisions, the invention is particularly simple to implement. In addition, the source node can transmit simultaneously on several virtual channels without waiting for the acknowledgment concerning the packets already sent. Finally, in return, it is not necessary to send to the node

  source the identifier of the destination node.

  According to a fourth aspect, the present invention relates to a device for transmitting user data over a network switched between a so-called "source" node having a unique identifier on said network and a so-called "recipient" node, said source node comprising:

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  - a means of determining additional outward data defining in particular, in its entirety, the path to be followed on said network, by said user data, and - a means of transmission, by the source node, of at least one packet said user data and said additional outward data relating thereto, characterized in that: the means for determining additional outward data from the source node is adapted to define additional outward data representative of said unique identifier of the source node, and the destination node comprises: a means of reading said identifier in said additional data to go from each packet, and to processing means adapted to: 15. verify the correct reception of user data and, in the event of good reception, to determine additional return data defining in particular a path going from said recipient node to the node identified by the said identifier, to means for transmitting acknowledgment data indicating the good reception of said user data and said

additional return data.

  According to a fifth aspect, the present invention relates to a device for transmitting user data over a switched network, from a so-called "source" node having a unique identifier on said network, comprising: - means for determining additional data of go defining in particular, in its entirety, the path to be followed on said network, by said user data, to reach a node called "recipient", and - a means for transmitting at least one packet of said user data and said data additional to go which are relative to it, characterized in that:

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  the means for determining additional outward data is adapted to define additional outward data representative of said

  unique identifier of the source node.

  According to a sixth aspect, the present invention relates to a device for receiving, by a so-called "recipient" node, user data on a switched network, data coming from a so-called "source" node having a unique identifier on said network, characterized in that that the recipient node comprises ò means for reading an identifier in additional data to be transmitted, in said packet with user data, and processing means suitable for verifying the proper reception of user data, for determining additional return data defining in particular a path going from said destination node to the node identified by said identifier, transmission means on the one hand, additional return data and, on the other hand, acknowledgment data indicating

  the proper reception of said user data.

  The invention also relates to a camera, a fax machine, a photographic camera, a computer and a television set, characterized in that they

  include a device as succinctly set out above.

  The invention also relates to: - a means of storing information readable by a computer or a microprocessor, retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention as succinctly set out above, and - a removable information storage means, partially or totally, readable by a computer or a microprocessor, retaining

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  instructions of a computer program characterized in that it allows the implementation of the method of the invention as succinctly set out above, The particular characteristics and advantages of the devices of the fourth, fifth and sixth aspects of the invention , this camera, this fax machine, this photographic camera, this computer, this television set and these information storage means being identical to those of the process targeted by the first aspect of the invention, they are not recalled here.

  The invention will be better understood on reading the description which

  will follow, made with reference to the appended drawings in which: - Figure 1 represents a transmission device according to the present invention, - Figure 2 represents a flowchart of operation of the transmission device illustrated in Figure 1, - Figure 3 represents data processed by different layers of transmission protocol implemented by a transmission device as illustrated in FIG. 1, FIG. 4 represents a succession of packets exchanged via a network, in accordance with transmission method object of the present invention, - Figure 5 shows a reception device according to the present invention, and - Figures 6A and 6B show a flowchart of

  operation of the receiving device illustrated in FIG. 5.

  In FIG. 1, the transmission device is illustrated in the form of a block diagram and represented under general reference 10 and comprises, interconnected by an address and data bus 102 - a central processing unit 106; - a random access memory RAM 104; - ROM 105;

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  - an input / output port 103 used to receive, in the form of binary data, so-called "user" information that the transmission device must transmit and allowing the transmission device to transmit information packets to a network communication 109; and, independently of the bus 102, an input 111 of user information to

  transmit, input connected to input / output port 103.

  Each of the elements illustrated in FIG. 1 is well known to those skilled in the art of network transmission systems and, more generally, information processing systems. These elements do not

are therefore not described here.

  It is observed here that the word "register" used below designates, in each of the memories, both a low-capacity memory area (retaining only a few binary data) and a memory area of

  large capacity (allowing to store an entire program).

  The random access memory 104 stores data, variables and intermediate processing results, in memory registers carrying,

  in the following description, the same names as the data they

  keep the values. The random access memory 104 comprises in particular: - a "user_data" register in which the user information to be transmitted is stored, information which includes, in particular, the information coming from the input 111, - a "add_data" register in which information is stored additional information to go to transmit, information which defines, in particular, in its entirety, the path to be followed by user data on the communication network, and - a "route" register in which routing information describing a succession of communication network nodes that user data can follow to reach a

  information reception device as illustrated in FIG. 5.

  The read-only memory 105 is adapted to keep:

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  - the operating program of the central processing unit 106, in a "programl" register, - an identifier representative of the transmission device 10, an identifier which is unique on the communication network, - one or more pieces of information representative of good reception of information by an information recipient node, in a

"acquit data" register.

  The read-only memory 105 constitutes a means of storing information readable by a computer or a microprocessor, retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention. According to a variant, the read-only memory 105 is removable, partially or totally, and comprises, for example, a magnetic tape, a floppy disk or a compact disk with frozen memory ("CD-ROM"

in English).

  The central processing unit 106 is adapted to implement the flowchart described in FIG. 2. In this FIG. 2, it can be seen that during an operation 200, the central processing unit 106 is in an operating state that is not requiring no communication on the network then, during an operation 201, it receives, from a software application, a request for communication of a message to a destination node on the network. From the reception of this request, the central unit 106 initializes the

  communication in the transmission device 10, according to known methods.

  Then, the central unit 106 adds, in the register "add_data" of the random access memory 104, the route information 308 (see FIG. 3) that the packet will have to follow for

reach the recipient node.

  During an operation 202, the central unit 106 adds, in the register "add_data" of the random access memory 104, a virtual channel identifier

309 (see Figure 3).

  During an operation 203, the central unit 106 adds, in the "adddata" register of the random access memory 104, a new stamp 311 (see

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  figure 3), whose binary value is different from that of the associated stamp

  to the previous packet sent by the source node on the same virtual channel.

  During an operation 204, the user data to be sent are received from the software application that issued the request, during the operation 201, and stored in the "user_data" register of the

RAM 104.

  During an operation 205, the packet consisting of the data

  additional data and user data is sent over the network.

  During an operation 206, the central unit waits for the receipt of an acknowledgment from the destination node, for a predetermined duration. When this time has elapsed, the central unit 106 performs a test 207, during which it determines whether an acknowledgment has been received from the

part of the recipient node, or not.

  When the result of test 207 is negative, operation 205 is repeated. When the result of the test 207 is positive, during a test 208, the central unit 106 determines whether the stamp contained in the acknowledgment is

  identical to the stamp of the issued package, or not.

  When the result of test 208 is negative, operation 205 is repeated. When the result of the test 208 is positive, during a test 209, the central unit 106 determines whether the packet sent was the last packet of the message, or not. When the result of test 209 is negative, operation 201

is reiterated.

  When the result of test 209 is positive, operation 200 is repeated, which has the effect of warning the software application of the correct

  transmission of user data to the destination node.

  In FIG. 3, it can be seen that, for the user layer 300 of the communication protocol, a data frame 301 is transmitted to the message layer 302 of the communication protocol. To constitute the user data message, the layer 302 adds to the data constituting the frame, a message header 303, comprising protocol identification information 304, message dimension information

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  305, memory identification information 306 and information 307 representative of the size of the useful information, within the meaning of the IPC protocol set

  implemented by the "Chorus" operating system.

  We observe here that information 305 and 306 are specifically linked to the "Chorus" operating system and are in no way linked

  to the implementation of the invention.

  The packet layer 320 constitutes, from this message, packets each comprising user data, and a packet header comprising: route information 308 comprising information representative of each node of the network by which the user information must pass, - virtual channel number information 309, - an identifier 310 of the source node, and - information called "stamp" 311 ("stamp" in English),

  intended to allow the management of the loss of the packet before reception.

  In the embodiment described and shown, the route information is gradually extracted from the packet: each time a node of the network receives this packet, it determines with the first part of the route information which is the next node who will receive the package and it transmits the entire package it received, except for the first part. Thus, the additional data sent by the source node is not fully received by the destination node. This mode of operation of the network and, more particularly of its nodes or switches is known as

  English for "header deletion".

  In the embodiment described and shown, the stamp is binary and can therefore take two values alternately. However, more values can be assigned to the stamp to increase the

  reliability of the methods and devices of the invention.

  At the end of each packet, with the exception of the last, there is a termination consisting of end-of-packet information 312. At the end of the

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  last packet of the message, instead of the end of packet information, the

  packet layer places end of message information 313.

  In the bottom right of FIG. 3, a packet 315 of acknowledgment data is represented, a packet also called "acknowledgment" in the rest of the

  description. This acknowledgment is issued by the destination node of a packet

  containing user data intended for the source node, when the

  recipient node successfully received user data.

  It is observed that the acknowledgment 315 comprises only: - route information 317 comprising information representative of each node of the network through which the other information of the acknowledgment must pass, - virtual channel number information 316, and

  - The stamp 311 received with the user data.

  It is observed here that the virtual channel number information 309 and 316 are identical. Indeed, this number is copied by the recipient node in the additional outbound data. In the additional data which accompanies the user data, the source node places, in addition to the virtual channel number, the unique identifier that it has on the network, which allows the destination node to identify the channel

  virtual used by user data, unambiguous.

  On the contrary, to return the acknowledgment, the destination node does not have to send its unique identifier on the network, insofar as the virtual channel number that it uses is already known to the source node. So,

  the virtual channel identifier is sufficient to acknowledge reception.

  In Figure 4, we observe, symbolized by downward arrows placed in a central column, messages transmitted over the network, between a source node 10, on the left, and a destination node 50 (see Figure 5), on the right. The arrows oriented from left to right correspond to packets transmitted from the source node of user data intended for the destination node of this data and the arrows oriented from right to left correspond to packets transmitted

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  from the destination node of user data to the source node of

those data.

  The four arrows 401 to 404 in the central column

  correspond to a mode of communication in accordance with the present invention.

  The first packet 401 is sent by the source node 10 or sending device, to the destination node, during operation 205. Then, the destination node 50 which receives the packet verifies that it has enough memory for keep user data, on the one hand, and if the stamp is different from the stamp of the previous packet received from the same source node

  (see tests 603 and 606 in FIG. 6A).

  When these verifications are positive, the destination node transmits to the source node an acknowledgment 402 comprising the same

stamps as package 401.

  At the same time, the source node waits for the receipt of an acknowledgment from the destination node (operation 206, FIG. 2) and at the end of this period, since it has received the acknowledgment 402, it checks that the stamp of

  the acknowledgment is identical to the stamp of the package 401 (test 208, FIG. 2).

  When this verification is positive, and if it has another packet to send to the destination node, the source node sends a new packet 403, comprising a stamp of value different from the stamp of packet 401. In the case shown, it is assumed that the destination node then no longer has enough memory available to store the user data of the packet 403. In this case, it ignores the packet 403 and does not return

  no acknowledgment to the source.

  At the end of the waiting time provided for operation 206, the source node then determines that it has not received an acknowledgment and proceeds with a

  re-issue of packet 401, in the form of packet 404.

  The reception device shown in FIG. 5, under general reference 50, is illustrated in the form of a block diagram. It comprises, linked together by an address and data bus 502:

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  - a central processing unit 506; - a random access memory RAM 504; - ROM 505 read only memory; an input / output port 503 used to receive information packets that the reception device must process, store or transmit and allowing the reception device to transmit all or part of the user information received; and, independently of the bus 502, the network 109, connected to the input / output port 503, receiving the packets intended for the device

reception 50.

  Each of the elements illustrated in FIG. 5 is well known to those skilled in the art of information communication systems and, more generally, information processing systems. These elements do not

are therefore not described here.

  The random access memory 504 stores data, variables and intermediate processing results, in memory registers carrying,

  in the following description, the same names as the data they

  keep the values. The random access memory 504 comprises in particular: a “userdata” register in which the received user information is stored, information coming from the input / output port 503, a “add_data” register in which additional information received with the user information is stored , - a "reverse_adddata" register in which additional information to be transmitted is stored, information which defines, in particular, in its entirety, the path to be followed by the acknowledgment data on the communication network, and - a "reverse_route" register in which routing information is stored describing a succession of nodes of the communication network that the acknowledgment data can follow to reach

  an information transmission device as illustrated in FIG. 1.

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  The read-only memory 105 is adapted to keep: - the operating program of the central processing unit 506, in a register "program2", - acknowledgment data to be transmitted back to the transmission device when the user data have have been correctly transmitted,

in an "acquit_data" register.

  The read-only memory 505 constitutes a means of storing information readable by a computer or a microprocessor, retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention. According to a variant, the read-only memory 505 is removable, partially or totally, and comprises, for example, a magnetic tape, a floppy disk or a compact disk with frozen memory ("CD-ROM"

in English).

  The central processing unit 506 is adapted to implement the flowchart described in FIGS. 6A and 6B. In FIG. 6A, it can be seen that during an operation 601, the destination node 50 which processes software applications not detailed here, receives a packet in the port buffer memory

  input / output 103 and reads the additional data it contains.

  During an operation 602, the central unit 506 considers the stamp contained in the received packet as well as the virtual channel identifier and the source node identifier. During a test 603, the central unit 506 determines whether the stamp received is identical to the stamp previously received from the same source node, on the same virtual channel. It is observed here that the stamp alternately takes different values for each of the virtual channels. Thus, by using two different virtual channels, can the source node use two identical timestamps, but not between two successive packet transmissions using the same channel

  virtual, the stamps necessarily take two different values.

  When the result of test 603 is positive, operation 601 is repeated. When the result of test 603 is negative, during a test 604,

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  the central processing unit 506 determines whether the packet considered is a first packet of a message or not, by determining whether the message header 303 is in the

package considered, or not.

  When the result of test 604 is positive, operation 605 consists in reserving sufficient memory space for storing the whole of the

message, in RAM 504.

  During a test 606, the central processing unit 506 then determines whether the memory reservation has been made, that is to say whether the memory space

  necessary was available or not, in RAM 504, or not.

  When the result of test 606 is negative, operation 601 is repeated. When the result of test 606 is positive or when the result of test 604 is negative, during an operation 607, the packet considered is put in

  memory in the part reserved for this purpose, of the RAM 504.

  Then, during a test 608, the central unit determines whether the memorization has gone well or not. To this end, the central unit 506 verifies the integrity of the package by means known to those skilled in the art, by

  example using parity bits or error correction codes.

  When the result of test 608 is positive, operation 601 is repeated. When the result of the test 608 is negative, during an operation 609 (FIG. 6B), the central unit 506 determines the route information 317 and the virtual channel so that the acknowledgment packet reaches the source node identified by the source node identifier 310 of the received packet and places this route information and that of virtual channel in the "add_data" register of the

RAM 504.

  During an operation 610, the central unit 506 copies

  the stamp of the packet received in the "add_data" register of the RAM 504.

  During an operation 611, the central unit 506 transmits the packet consisting of the information kept in the "adddata" register of the

  random access memory 504, intended for the source node.

  Finally, the central unit returns to operation 601.

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Claims (20)

  1. A method of transmitting user data over a switched network between a so-called "source" node (10) having a unique identifier on said network and a so-called "recipient" node (50), a method comprising, performed by the source node - a operation for determining additional outward data (201 to 203) defining in particular, in its entirety, the path to be followed on said network, by said user data, and - a transmission operation (205), by the source node, at least one packet of said user data and said additional outward data relating thereto, characterized in that: during the operation of determining additional outward data, the source node defines additional data d 'go representative of said unique identifier of the source node, and - the method comprises, carried out by the destination node, on receipt of each packet: a read operation (602, 604 ) of said identifier in said additional outgoing data, and to a verification operation (604) of good reception of the user data and, in the event of good reception: an operation of determining additional return data (609, 610) defining in particular a path going from said recipient node to the node identified by said identifier, and an acknowledgment operation (611) by sending acknowledgment data indicating the good reception of said user data and said data additional returns. 18 2779019   2. Transmission method according to claim 1, characterized in that, during the operation of determining additional outward data (201 to 203), the source node defines additional outward data   representative of the virtual channel that said user data must follow.   3. Transmission method according to claim 2, characterized in that during the operation of determining additional return data (609, 610), the destination node determines additional return data representative of the virtual channel that the data must follow.   4. Method for transmitting user data over a switched network implemented by a so-called "source" node (10) having a unique identifier on said network for transmitting user data to a so-called "recipient" node (50), method comprising: - an operation for determining additional outward data (201 to 203) defining in particular, in its entirety, the path to be followed on said network, by said user data, and - a transmission operation (205), by the source node, of at least one packet of said user data and said additional outward data relating thereto, characterized in that the additional data determined during the operation of determining additional outward data are   representative of said unique identifier of the source node.   5. Transmission method according to claim 4, characterized in that the additional data determined during the operation of determining additional outward data (201 to 203) are   representative of the virtual channel that said user data must follow.   6. Method according to claim 5, characterized in that it comprises, on reception of a return packet, coming from said destination node, packet comprising acknowledgment information: 19 2779019   To a read operation (207) of a virtual channel identifier represented by said acknowledgment information, and To a comparison operation (207) of said received identifier and the virtual channel identifier implemented during the 'issue operation. 7. Method for receiving, by a so-called "recipient" node (50), user data on a switched network, data coming from a so-called "source" node (10) having a unique identifier on said network, characterized in that it comprises, on reception of each packet coming from the source node, and carried out by the destination node: an operation of reading (604) of an identifier in additional data to be transmitted, in said packet with user data, and an operation for verifying good reception of the user data and, in the event of good reception: an operation for determining additional return data (609, 610) defining in particular a path going from said destination node to the node identified by said identifier, and 20. an acknowledgment operation by sending acknowledgment data indicating the good reception of said user data and of said additional return data. 8. Reception method according to claim 7, characterized in that, during the operation of determining additional return data (609, 610), the destination node determines additional return data representative of the virtual channel that the data acquittal have to follow.   9. Reception method according to any one of   claims 7 or 8, characterized in that, during the operation of   determination of additional return data (609, 610), the node 2779019   recipient incorporates into the additional return data a virtual channel identifier represented by additional data received from the source node. 10. Device for transmitting user data over a network switched between a so-called "source" node (10) having a unique identifier on said network and a so-called "recipient" node (50), said source node comprising: - means for determining (104 to 106) of additional forward data defining in particular, in its entirety, the path to be followed on said network, by said user data, and - a transmission means (103), by the source node, of at least at least one packet of said user data and said additional outward data which are related thereto, characterized in that: the means for determining additional outward data from the source node is adapted to define additional outward data representative of said unique identifier of the source node, and - the destination node comprises: * means for reading (504 to 506) of said identifier in said additional forward data of each packet, and * m processing means (504 to 506) adapted to: check the good reception of user data and, in the event of good reception, to determine additional return data defining in particular a path going from said recipient node to the node identified by said identifier, and means for transmitting acknowledgment data indicating the good reception of said user data and said additional return data. 21 2779019   11. Transmission device according to claim 10, characterized in that, the means for determining additional outward data is adapted to define additional outward data representative   of the virtual channel that said user data must follow.   12. Transmission device according to claim 11, characterized in that the means for determining additional return data is adapted to determine additional return data   representative of the virtual channel that the acknowledgment data should follow.   13. Device for transmitting user data on a switched network, from a so-called "source" node (10) having a unique identifier on said network, comprising: - means for determining (104 to 106) additional data of go defining in particular, in its entirety, the path to be followed on said network, by said user data, to reach a so-called "recipient" node (50) and - a transmission means (103) of at least one packet of said user data and said additional outward data relating thereto, characterized in that: the means for determining additional outward data is adapted to define additional outward data representative of said outward   unique identifier of the source node.   14. Transmission device according to claim 13, characterized in that the means for determining additional outward data (104 to 106) is adapted to define additional outward data representative of the   virtual channel that said user data must follow.   15. Transmission device according to claim 14, characterized in that it comprises: a means for receiving (103) a packet coming from the destination node, a packet comprising acknowledgment information, 22 2779019   means for reading (104 to 106) a virtual channel identifier represented by said acknowledgment information, and means for comparing (104 to 106) said received identifier and the virtual channel identifier used in during the transmission operation. 16. Device for receiving a so-called "recipient" node (50), user data on a switched network, data coming from a so-called "source" node (10) having a unique identifier on said network, characterized in that it comprises:  10. means for reading (504 to 506) an identifier in additional data going to be transmitted, in said packet with user data, and processing means (504 to 506) adapted to verify the good reception of the data user, 15. to determine additional return data defining in particular a path going from said destination node to the node identified by said identifier, and to transmission means (103) on the one hand, additional return data and, on the other hand, acknowledgment data indicating the   good reception of said user data.   17. Reception device according to claim 16, characterized in that the means for determining (504 to 506) additional return data is adapted to determine additional data representative of the   virtual channel that the acknowledgment data should follow.   18. Reception device according to any one of   claims 16 or 17, characterized in that the means for determining   additional return data (504 to 506) is adapted to incorporate into the additional return data, a virtual channel identifier represented   by additional data received from the source node. 23 2779019   19. Camera, characterized in that it includes a device for   management according to any one of claims 10 to 18.   20. Fax machine, characterized in that it includes a device for   management according to any one of claims 10 to 18.   21. Camera, characterized in that it comprises a   management device according to any one of claims 10 to 18.   22. Computer, characterized in that it comprises a device for   management according to any one of claims 10 to 18.   23. Television, characterized in that it comprises a device for   management according to any one of claims 10 to 18.