Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/02—Details
  • H04L12/16—Arrangements for providing special services to substations
  • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
  • H04L12/1863—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast comprising mechanisms for improved reliability, e.g. status reports
  • H04L12/1868—Measures taken after transmission, e.g. acknowledgments
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/02—Details
  • H04L12/16—Arrangements for providing special services to substations
  • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
  • H04L12/1863—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast comprising mechanisms for improved reliability, e.g. status reports
  • H04L12/1877—Measures taken prior to transmission

Definitions

• the invention relates to a method and a system for transmitting a multicast stream on physical links including unreliable links, such as the links provided by the shared networks, including the WIFI links 5 defined by the IEEE standard.
• 802.11 or 802.15 (a) or the links formed on the domestic lines with PLC power lines, defined by the Home Plug consortium.
• a multicast receiving terminal desiring to receive a given multicast stream, delivered by a multicast server for example, is pre-registered to a multicast group.
• This registration makes it possible to insert this terminal, or a multicast receiver address representing the latter, within a multicast tree, to which all the members of the same multicast group belong. Because of the aforementioned tree structure, materialized by the network connection of all its members, all the members of a multicast group receive the same transmission of multicast information. This transmission can be defined as a point / multipoint transmission.
• patent application US 2005 002365 proposes a reliability of multicast information broadcasting for unreliable links, such as the radio link according to the IEEE 802.11 standard.
• the proposed system concerns the layer of the OSI level 2 model but the described process requires the implementation of new multicast frame acknowledgment modules, not only in the multicast transmitter but also in each multicast receiver terminal.
• the US 2003 patent application 206549 also suggests a reliability of the multicast information broadcast for unreliable links, such as the radio link according to the IEEE 802.11 standard, the proposed system however concerning the level 3 OSI model layer.
• the process described is to establish between the multicast terminal-receiver and the multicast server an additional channel, whereby the receiving terminal is able to request multicast information expected, but not received.
• the multicast server can then multicast the required information.
• the process described by this document obviously overloads the server and the receiving endpoints, all of which receive rediffusion, by definition.
• the reliability introduced by level 3 of the OSI model introduces additional delay, during the detection of loss of frame multicast. This system also requires the implementation of new modules in the transmitter and in each multicast receiver terminal.
• the IGMP proxy checks in its table the existence of one or more terminals each designated by a destination unicast IP address, and, if so, replaces the destination multicast IP address of the packet by the unicast IP address of each of the terminals, multicast receiver.
• the present invention relates to the implementation of a method and a system for transmitting a multicast stream in data exchange network, or on any link, including any unreliable link such as IEEE type link 802.11 and 802.15 or CPL, links whose reliability is likely to be deteriorated by radio interference respectively of the low voltage power supply network.
• any unreliable link such as IEEE type link 802.11 and 802.15 or CPL, links whose reliability is likely to be deteriorated by radio interference respectively of the low voltage power supply network.
• an object of the present invention is the implementation of a system for transmitting a multicast stream, in the form of a specific module, implanted on the path of the transmission, at the very place where the transmission multicast switches from a reliable link, such as an Ethernet network link, to an unreliable link, especially at an access point that is still called a gateway.
• Another object of the present invention is, in particular, the implementation of a method and a system for transmitting a multicast stream by transforming a multicast stream at the link level, still referred to as a frame level, of the layers.
• Another object of the present invention is also the implementation of a method and a system for transmitting a multicast stream in a unicast stream at the link level, leaving the addresses and transfer protocols at the levels above the level unchanged. link of the OSI or TCP / IP model, the method and the systems object of the invention being thus totally transparent for the current servers and multicast receiving terminals and fully compatible with the latter.
• Another object of the present invention is finally the implementation of a method and a system for transmitting a multicast stream in which the interceptions of multicast frames necessary for their implementation are executed by filtering at the link level and their retransmission according to one or more unicast flows by address redirection, the method and the system, objects) of the present invention, thus requiring the implementation of no routing process and can therefore be implemented in network equipment with poor network intelligence, such as an access point, gateway, or switch.
• the method of transmitting a multicast stream in a data exchange network is remarkable in that it consists at least, at an access point to this shared network, to analyze the data frame multicast stream, for detecting the link-level multicast address of this multicast stream, substituting in each data frame for said link-level multicast address a link-level unicast address for at least one node of that network; shared, to generate a substituted multicast frame, transmit instead of these multicast streams at least one unicast flow, succession of substituted multicast frames, said unicast address at the link level, which allows to benefit from the frame acknowledgment mechanism of the unicast stream transmission, for the succession of substituted multicast frames.
• the system for transmitting a multicast stream in a data exchange network is implanted in a data exchange network access point, this access point comprising at least a plurality of data exchange networks.
• input / output points one of the input / output points being logically connected to a multicast stream server and another at least of these input / output points being connected to a potential receiver terminal of a multicast stream, and a software infrastructure module for managing the input / output ports.
• This potential receiver terminal is located in the shared network by a unicast address at the determined link level.
• the system which is the subject of the invention, is remarkable in that it comprises, at least one module for making the transmission of a multicast stream enabling transmission, instead of any multicast stream transmitted by this multicast server, at least one unicast flow, a succession of substituted multicast data frames in which the link-level multicast address is substituted for the unicast address at the determined link level, to this potential receiving terminal. It further comprises a database comprising at least one permanent database containing configuration data of the reliability module and a temporary database, for maintaining a state of the one or a plurality of potential receiver terminals of a multicast streams, each connected to one of the input / output points.
• the invention further relates to:
• a computer program stored on a storage medium for execution by a computer or by the central processing unit of a system, remarkable in that on connection of a potential receiver terminal of a multicast stream to the one of the input / output ports of this system, said computer program executes at least, successively: the calculation of an intercept amount filter data frames transmitted by said.
• a computer program stored on a storage medium for execution by a computer or by the central processing unit of a system remarkable in that, depending on the analysis of the nature of at least one frame of data transmitted by a potential address receiver terminal of a multicast stream, if the message conveyed by said frame is an end of access message to said multicast stream, said program executes at least, successively: the recovery in said frame of the higher level multicast address at the requested multicast stream link level; deriving, from said higher level multicast address at the link level, the address at the link level of the requested multicast stream; the deletion of the corresponding substitution rule; removing the descending filter on the input / output port to which said multicast server is connected; and, following verification of the non-existence of a specific rule relating to the unicast address at the link level of said potential receiving terminal, the deletion of the rising filter on the input / output port to which said potential receiving terminal is connected.
• the method, the system for transmitting a multicast stream and the computer program products that are the subject of the invention find application in the implementation of data exchange networks such as shared networks of the local network type. enterprise, home networks radio according to the IEEE 802.11 standard or powerline CPL for example. They will be better understood by reading the description and by observing the drawings, in which:
• FIG. 1 represents, by way of illustration, a flowchart of the essential steps for implementing the transmission method of a shared network multicast stream, object of the present invention
• FIG. 2a represents, by way of illustration, a detail of implementation of the step of analyzing the multicast stream executed by the method that is the subject of the invention illustrated in FIG. 1; • • • '
• FIG. 2b represents, by way of illustration, a detail of implementation of the address substitution step performed by the method forming the subject of the invention illustrated in FIG. 1;
• FIG. 3a shows, for illustrative purposes, a diagram. functional of a transmission system of a multicast stream object of the invention, implanted in an access point;
• FIG. 3b represents, by way of illustration, a block diagram of a reliability module for transmitting a constituent multicast stream of a system that is the subject of the invention, as represented in FIG. 3a;
• FIG. 4a represents, by way of illustration, a functional flowchart of the steps implemented by the system and the reliability module for the transmission of a multicast stream represented in FIGS. 3a and 3b, when launching a request for access to a multicast stream by a potential receiver terminal of a multicast stream;
• FIG. 4b represents, by way of illustration, a functional flowchart of the steps implemented by the system and the reliability module for the transmission of a multicast stream represented in FIGS. 3a and 3b, during the processing of multicast frames in a stream multicast whose multicast group address has been recognized according to the steps described in connection with FIG. 4a;
• FIG. 4c represents, by way of illustration, a functional flowchart of the steps implemented by the system and the module of FIG. reliability of the transmission of a multicast stream represented in FIGS. 3a and 3b, at launch a request to terminate access to a multicast session by a potential receiver terminal of a multicast stream;
• FIG. 5 represents an illustrative diagram of a substituted multicast frame, in accordance with the object of the present invention.
• FIG. 5 represents an illustrative diagram of a substituted multicast frame, in accordance with the object of the present invention.
• the method of transmitting a multicast stream in data exchange network is implemented at an access point AP, d. a gateway or switch as described previously in the description, these elements having no significant network intelligence, no network intelligence resource such as a routing resource being necessary for the implementation of the method of the present invention.
• a multicast stream consisting of a succession of multicast frames, each multicast frame denoted T [MUA] being at least linked to a multicast address MUA such that the multicast group address under which the diffusion of the multicast stream is performed.
• T [MUA] multicast stream
• MUF T [MUA]
• the method according to the invention consists, in a step A, in analyzing the multicast stream by data frames in order to detect the multicast address at the link level of the multicast stream in question.
• a multicast stream is meant not only any downstream multicast stream transmitted by a multicast server MS to a terminal T y potential receiver of the multicast stream considered as well as any succession of frames transmitted in the upstream direction of the potential receiver terminal mentioned above.
• T y to an AP access point or more generally to any multicast broadcast source, such as an MS multicast server.
• the above-mentioned upstream and downstream frames have in common the multicast destination address previously indicated MUA.
• step A of FIG. 1 the step of analyzing the multicast stream is represented by the relation:
• step A of FIG. 1 the detection of the multicast address at the link level is generally carried out from the address of each multicast frame at the higher level at the link level, these frames being denoted:
• Step A is then followed by a step B consisting in substituting in each screen of data at the link-level multicast address a link-level unicast address of at least one node of the data exchange network, to generate a substituted multicast frame.
• step B of FIG. 1 for a unipast address at the link level of a given node, address denoted UNA y , the node of the shared network being deemed to be constituted by the terminal T y mentioned above, the substitution operation is represented. by the symbolic relation:
• the multicast frame T [A A y ] substituted by red address redirection for example is none other than the previous multicast frame in which the address link-level multicast
• MUA x has been replaced by the unicast address at the link level of the node of the shared network, that is to say the terminal T y .
• Operation B is then followed by an operation C of transmitting instead of the multicast stream at least one unicast stream, the latter consisting of a succession of multicast frames substituted, the unicast stream being transmitted to the unicast address at the link level, that is to say towards the node of the shared network considered.
• a multicast stream frame T [MUA x ] may of course be substituted for a plurality of substituted multicast frames and finally a plurality of unicast streams transmitted under the unicast address UNA y of each of the nodes having access to the original multicast broadcast.
• the operating mode of the method that is the subject of the invention then makes it possible to benefit from the frame acknowledgment mechanism of the unicast stream transmission for each of the nodes of the shared network or terminals of the latter concerned by the multicast broadcast for the succession of frames. substituted multicast.
• the link level is constituted by layer level 2 of the OSI or TCP-IP model for defining the multicast and unicast flows.
• the latter operates only at the link level, that is to say at the level of the multicast or unicast frames, respectively, providing the link between the transfer points of the aforementioned frames and no case at the upper level of the successive layers of the OSI or TCP / IP model, which makes it possible to ensure the compatibility of the method that is the subject of the present invention with all the applications using such a protocol.
• the step of substituting in B of FIG. 1 for the link-level multicast address a link-level unicast address can advantageously be performed by filtering and redirecting the address of the data frames. received with the link-level multicast address to the link-level unicast address of the shared network node.
• terminal T y the connection of a potential receiver terminal of a multicast stream, terminal T y , is firstly considered, this terminal being deemed to execute a multicast stream request to a MUA group multicast address for example.
• step A of analyzing the multicast stream for detecting the link-level multicast address consists of at least as shown in FIG. FIG.
• step A 0 to detect the unicast address at the link level of a potential receiving terminal requesting access to the multicast stream in question
• the aforementioned step Ao can be executed when the receiving terminal is connected.
• potential T y at the access point AP via the corresponding data exchange network "the unicast address of the terminal T y being denoted UNA y and designating the corresponding unicast address of the terminal in the network of data exchange.
• the step A 0 is followed by a step A 1 consisted in calculating a filter intercept amount of data frames transmitted by the potential receiver terminal T y from the address unicast link level.
• the rising filter is noted for this reason:
• the aforementioned amount filter is intended to intercept any multicast access request message and in particular any multicast frame transmitted from the unicast address of the terminal UNAy.
• Each frame multicast access request includes multicast group address MUA which the terminal T wishes to access it and is noted for this reason T [MUA], this address is not known before interception.
• Step A 1 is then followed by a step A 2 of analyzing at least one data frame intercepted by the aforementioned amount filter to determine the type of multicast session messages transmitted by the terminal T y .
• step A 2 of FIG. 2a The aforementioned analysis step executed in step A 2 of FIG. 2a is represented by the symbolic relation
• step A 3 makes it possible to verify that the message supported by the multicast frame T [MUA] is a multicast session message of the accession type designated by "Access".
• the analysis method then consists in a return to the detection step of the unicast address of any address terminal UNA y at step Ao above.
• step A 3 On a positive response to the test of step A 3 , the message supported by the multicast frame T [MUA] being an accession-type multicast session message, the test step A 3 is followed by a step A 4 of discriminating the multicast address higher level link level of the multicast stream requested by the requesting terminal T y .
• step A 4 The discrimination of the higher level multicast address at the link level is represented by the relation in step A 4 :
• This discrimination operation is executed at the higher level at the link level, that is to say, finally, according to the OSI model or corresponding TCP / EP, on the level 3 of these, or on the packet level, the discrimination of the MUA address x + 1 , level 3, in the case of the implementation of the method of the invention is easily performed at the packet level.
• step A 4 is then followed by a step A 5 of deducing the MUA link level multicast address x from the higher level multicast address at MUA link level x + 1 .
• step A 5 of FIG. 2a this operation is represented by the relation:
• step B consisting in substituting the link level multicast address for a link level unicast address implemented by the method of the present invention, as illustrated in FIG. 1, will now be given in connection with FIG. Figure 2b. ,
• step A of. FIG. 1 provides not only the unicast address UNA y of the terminal T y but also the multicast address at the link level of the multicast stream requested and which normally must be received by the potential receiving terminal terminal T y .
• the method that is the subject of the invention for carrying out the aforementioned substitution then consists, at least in one step Bo, in calculating a downlink filter for intercepting data frames transmitted by the multicast stream, starting from the multicast address at the link level.
• step B 0 of FIG. 2b the downlink filter for intercepting data frames is noted:
• the aforementioned descending filter is intended to intercept any multicast stream frame transmitted by a multicast broadcasting source, such as a multicast server for example, under a multicast group address, the link-level MUA x address. .
• Step B 0 is then followed by a step B 1 consisting of calculating a link-level unicast address substitution rule at the link-level multicast address.
• step B1 of FIG. 2b the above substitution rule is noted:
• Step B 1 is then followed by a step B 2 of analysis of at least one data frame of the multicast stream intercepted by the aforementioned descending filter.
• step B2 the actual analysis operation is represented by the symbolic relationship:
• the descending filter applied to the MUF multicast stream (T [MUA x ] ⁇ , that is to say the succession of frames transmitted under the MUA group address x , makes it possible to intercept and analyze the corresponding frames to obtain the successive frames T [MUA x ] constituting the multicast stream.
• step B 2 is then followed by a step B 3 of applying the substitution rule calculated in step B0. For each intercepted multicast data frame is generated a substituted multicast data frame.
• step B 3 of FIG. 2b the operation of applying the substitution rule SR (MU A x , UNA y ) is represented by the symbolic relation:
• FIGS. 3 a, 3b A more detailed description of a system for transmitting a multicast stream in a data exchange network, in accordance with the subject of the present invention, will now be given in conjunction with FIGS. 3 a, 3b, and the following figures. .
• the system for transmitting a multicast stream in a data exchange network which is the subject of the present invention, is implemented in an AP access point in a data exchange network, the notion access point covering the notion of home gateway, the concept of switch giving access to the IP network for example, from a network such as a shared network.
• the access point AP comprises at least a plurality of input / output ports denoted P 1 ... Pj ... Pi and an infrastructure module port management software entry / exit marked SPIM.
• the aforementioned input / output port management software infrastructure module is connected by BUS connection to each of the aforementioned input / output ports.
• the access point advantageously comprises a central processing unit CPU and a working memory RAM interconnected by a BUS connection to the aforementioned input / output ports via the software infrastructure module of management of SPIM input / output ports.
• the central processing unit and the RAM working memory are conventional elements and, for this reason, shown in dotted lines in the drawing of FIG. 3a.
• one of the input / output ports, the port P 1 in a nonlimiting manner is logically connected to an MS multicast stream server by a wide area network, the logical connection meaning any connection by the intermediary IP protocol for example.
• Another at least one of the input / output ports, the port Pi as a non-limiting example is connected to a potential receiver terminal of a multicast stream, the terminal T y .
• the "potential T receiver terminal is detected in the network shared by the unicast address at the link level, the address UNA y previously mentioned in the description. This address is an address related to the single shared network ponfiguration and depends only mode shared network link! used and the terminal T y itself.
• the transmission system of a multicast stream in a data exchange network that is the subject of the invention also comprises, in a remarkable way, implanted in the access point AP considered, a reliability module 1 the transmission of multicast streams allowing the transmission instead of any multicast stream transmitted by the multicast server at least one unicast stream to the requesting terminal T y .
• the unicast stream considered is in fact constituted by a succession of frames of substituted multicast data, as described previously in the description, in which at the link-level multicast address, MUA x is substituted for the unicast address at the determined link level.
• UNA y of the terminal T y as described previously in the description.
• a database DB comprising at least one permanent database containing configuration data of the reliability module and a temporary database making it possible to maintain the database.
• the state of one or a plurality of potential receiving terminals such as the terminal T y , capable of receiving a multicast stream, each of the aforementioned terminals being connected to one of the input / output ports.
• FIG. 3a shows the integrated DB database at the access point PA.
• the database DB can then be constituted on a hard disk directly integrated with the AP access point.
• This situation can be encountered when the access point is a gateway such as a home gateway, for example, or a larger installation as part of a corporate network.
• the database DB can be implemented outside the access point AP.
• the database DB can be linked to the corporate network for example directly or via a port input / output above.
• the module 1 for reliability of the transmission of a multicast stream in a data exchange network can comprise, at least advantageously, a data storage / retrieval module Io of the database DB, the storage module 10 being advantageously connected by a BUS link to the database DB and to the central processing unit CPU for example, as represented in figure 3 a.
• the reliability module 1 comprises, as shown in FIG. 3b above, directly connected to the storage / extraction module I 0 , a Ii chain for filtering and recovering multicast frames from multicast frames transmitted by the input / output port management software infrastructure.
• the string 1 ⁇ filtering and recovering frames allows, from multicast frames transmitted by the software infrastructure management of input / output ports, to perform the operation of .filtering and recovery of the aforementioned frames.
• a module I 2 for unicast address recovery is directly connected to the data storage / retrieval module I 0 DB database.
• the above-mentioned module I 2 for unicast address retrieval allows the retrieval of the address declared during the connection of the potential receiver terminal T y of multicast streams to the input / output port Pi, for example.
• a chain I 3 for deducing the multicast address at the link level is also connected directly to the storage / extraction module lo.
• the chain I 3 for deducing the multicast address at the link level makes it possible, from the multicast address at the higher level to the link level, that is to say the MUA address x + i contained in the multicast frame, d obtain the deduction of the multicast address at MUA link level x as mentioned previously in the description.
• a chain I 4 for calculating and applying link-level unicast address substitution rules to the link-level multicast address is also provided and directly connected to the base data storage / retrieval module I 0. of data.
• the chain 1 1 for filtering and retrieving multicast frames from the multicast frames transmitted by the SPEVI input / output port management software infrastructure comprises a calculation module 1 10 of filters at the link level.
• This compute module calculates and install link level filters, level 2 filters, which are then applied at the relevant input / output ports.
• the lio module for calculating the filters at the link level makes it possible to store information relating to the filter in the database DB, by means of the storage / retrieval module IQ.
• the chain Ii for filtering and recovering multicast frames includes a read module for placing filters at the link level.
• the aforementioned module dialogs with software modules of the SPIM input / output port management software infrastructure, so as to place the link-level filters defined by the module 1 ! o calculating the filters at the link level on the input / output ports Pj relevant or to remove the aforementioned filters at the end of the session, as will be described later in the description.
• the SPIM input / output port management software infrastructure is then able to send I 1 filtered frames to a recovery module. 2, frames for which the established filter, filter at link level, by the module 1 10 calculating filters at link level is then recognized.
• the module 1 12 for recovering the filtered frames makes it possible to recover the frames sent by the software infrastructure for managing the input / output ports SPIM and sends the aforementioned recovered, that is, filtered, frames to a module I. 6 of filtered filtered multicast frames, provided by the chain of filtering and recovery multicast frames I 1 .
• the unicast address recovery module I 2 makes it possible to recover the unicast address provided during the connection of the terminal T y and the start of the procedure for the terminal T y mentioned above.
• the module I 2 makes it possible to store this information in the database DB by means of the module I 0 for storing / extracting the database.
• the chain I 3 for deducing the multicast address at the link level, from the multicast address at the higher level to the link level contained in each multicast frame, comprises in fact a module l 3 o of address recovery multicast at higher than the link level, that is to say at level 3.
• the address recovery module l 3 o makes it possible to recover the higher level multicast address at the link level contained in the multicast message and transmits the address. higher level at the aforementioned link level to a module I 31 constituting the chain I 3 deduction of the multicast address at link level.
• the module I 31 makes it possible to deduce from the multicast address at the higher level at the link level, the multicast address at the link level and makes it possible to store this information in the database DB by means of the storage / retrieval function of the database executed by the module I 0 .
• the chain I 4 for calculating and applying unicast address substitution rule rules at the address at the link level comprises, as shown in FIG. 3b, a module I 40 for calculating the substitution rules.
• the module I 40 makes it possible to form the substitution rules that make it possible to substitute the link-level multicast addresses with the corresponding link-level unicast addresses.
• the rules established by the aforementioned module I 40 are transmitted to a module I 41 constituting the chain I 4 for calculating and applying the rules for substituting addresses.
• the module 41 is a module for applying the substitution rules.
• the I 41 supra 1 thus receives the frames of the analysis module filtered I 6 a frame together with the identifier of the filter corresponding transmitted by the module I 6 Analysis of multicast frames filtered, recovered, provided by the filter chain and recovering filtered multicast frames.
• the module 41 makes it possible to apply the substitution rules defined by the module 40 for calculating the substitution rules and thus makes it possible to generate a substituted multicast frame, as described previously in the description.
• a module I 5 sending frames for switching to the corresponding input / output port Pi is provided.
• this frame is sent by the latter to the module 5 for sending the frames for switching to the port.
• the above-mentioned module I 5 then sends the substituted multicast frame back to the SPIM input / output port management software infrastructure to switch the frame to its final destination, ie to the address.
• UNA y unicast address of the terminal T y connected to the port P;
• module I 6 for analyzing the filtered frames it is indicated that the latter is in direct relation with the module 1 12 for the recovery of the filtered multicast frames from which it receives the filtered multicast frames but also in relation with the module I. 30 multicast address recovery at the level above the level link, with the module I 41 for applying the substitution rules and finally with the module I 5 for sending frames for switching to the relevant input / output port
• the module I 6 for analyzing filtered filtered multicast frames allows at least to ensure:
• the terminal T y contains a software application which is intended to multicast requested stream.
• the end user of the aforementioned terminal communicates with the multicast application by means of a man-machine interface in a conventional manner.
• an AP gateway or access point designates an element allowing the passage of data between physical links of different technologies.
• an AP access point allowing the passage between a physical link Ethernet and a Physical link radio type WIFI is considered a gateway in the broad sense of the term.
• a gateway may also have, if necessary, application-related functions such as address supply functions or the like.
• multicasthmicast procedure link level the procedure followed by the system and in particular the protocol 1 for reliability of the transmission of a multicast stream in network preferably shared but not limiting as illustrated with reference to Figures 4a to 4c above.
• the launching of the procedure concerns the launching of the link-level multicast / unicast procedure.
• the module 1 for reliability of a shared network multicast stream can:
• One of the applications of the gateway or access point AP • can then activate the module 1 for reliability of the transmission of a shared network multicast stream and provide it with the identifier of the terminator-receiver multicast is -to- say unicast address UNA y previously mentioned.
• the multicast / unicast procedure at the aforementioned link level is launched with at least one unicast address at the link level of at least one potential multicast receiving terminal, ie ie the UNA address y , which corresponds to a MAC address in the shared network for Medium Access ⁇ ontrol in English.
• the unicast address recovery module I 2 stores the identifier of the potential multicast receiver terminal T y , c 'in the database DB. that is, its unicast MAC address UNA y .
• the above-mentioned storage is performed by means of the function of the storage / retrieval module Io of the database DB.
• a step 100 for calculating the upstream filter A 1 is then called by the module 1 10 of the chain 1 1 for calculating the link level filters, the module I 2 thus making it possible to recover the unicast address. in order to establish a rising filter based on the aforementioned address.
• the link-level filter calculation module 1 then stores in the DB database the aforementioned filter, which is mapped into the DB database with the unicast address of the multicast receiver terminal.
• the read module then executes the placement function of the filter Ai in a step 101 shown in FIG. 4a, that is to say of placement and installation of the rising filter on the port Pj, logical port of the gateway, ensuring the connection of the gateway to the multicast receiving terminal T y .
• a 1 can be provided.
• the module 1 1 12 of recovery frames then filtered in a step 103 allows the interception of frames filtered by the filter amount Ai, frame after the potential receiver terminal T y, which are then transmitted to the 6 I frame analysis module .
• the aforementioned module analyzes the filtered frames and then allows, in a step 104 to detect the type of message transmitted by the terminal T y and, in particular, to detect the existence of an access signaling message to a multicast session , message says "Access" type.
• step 102 upright filter presence is performed to continue the process of monitoring each potential multicast receiver terminal T y .
• This operation is represented by the other message return loop in step 102 of Figure 4a.
• message type "Withdrawal” a specific procedure represented by the reference T on the Figure 4a is called, which will be described later in the description.
• a step 105 is called in the conditions below.
• the frame is then copied by the frame analysis module I 6 .
• the original frame is sent to the packet sending module for switching to the port, module I 5 , which then sends the original frame to the SPIM port management software infrastructure.
• Copying the filtered frame is then sent in the module I 30 for recovering multicast address of the upper level link level.
• the message supported by the above-mentioned frame contains the higher-level multicast address at the link level of the multicast group to which the potential multicast receiving terminal wishes to access.
• the higher-level address at the link level is then retrieved by the higher-level multicast address recovery module l 3 o at the link level.
• the module I 31 then makes it possible to carry out in step 106 the deduction of multicast address at the link level from the higher level multicast address at the aforementioned link level, the multicast address.
• the link level is the one used by the multicast group considered to be able to receive the multicast broadcast requested by the terminal T y , according to a predefined deduction rule.
• the link-level multicast address deduction module I 31 then proceeds to store the link-level multicast address in the DB database.
• the above-mentioned storage is carried out via the storage / extraction module Io of the database.
• the deduced multicast address is mapped to the unicast address of the potential receiver terminal T y and with the upstream filter A 1 previously stored.
• Discrimination steps 105, deduction 106 of the multicast address higher level MUA link level x + I and deduction of the multicast address at link level MUA x executed by the module I 30 , respectively I 31 are then continued by the succession of steps referenced G in Figure 4a, which are explained with reference to Figure 4b.
• the module 1 for reliability of the transmission of a multicast stream makes it possible to execute a step 107 of calculating a descending filter denoted B 1 .
• the descending filter B 1 is then stored in the database DB via the module I 0 and matched in the latter with the unicast address of the potential receiver terminal T y multicast with the upstream filter A 1 previously described and the multicast address at the previously stored link level.
• a step 108 of placing the descending filter B 1 on the port P 1 to which the multicast server MS is connected is then executed by the placement module of the filters at the link level referenced I 11 .
• Step 108 above is then followed by a step 109 of calculating the substitution rule noted C 1 in Figure 4b.
• This step is executed by the module I 40 , which retrieves from the database DB, the multicast address at the link level, the unicast address of the potential multicast receiver terminal T y and an identifier corresponding to the descendant filter B 1 , in order to form the substitution rule called rule C, designated SR (MUA x , UNA y ) previously in the description.
• the aforementioned rule makes it possible to replace the multicast address at the destination link level with the unicast address at the link level of the potential multicast receiver terminal T y previously stored in the database DB, at the same time. launching the procedure shown in FIG. 4a for the filtered frame intercepted by the descending filter B 1 .
• substitution rule Ci (destination_target_address_ "01: 00: 5E: 01: 02: 0B") substituted by destination_target_address_ "09: 88: 5E: 01; 99: 99" for frames filtered by the descending filter Bi.
• step 109 a return to step 102 for verifying the presence of the rising filter is provided, so as to allow the continued interception of any rising multicast frame.
• Each multicast frame filtered by the descending filter Bi is intercepted by the filtered frame retrieval module 1 n, transmitted to the filtered frames analysis module I 6 and then redirected, accompanied by the identifier of the descending filter B 1 to the module 1.
• 4 i application of the substitution rules The latter then executes the application of the corresponding substitution rule, that is to say, the rule corresponding to a frame intercepted by the descending filter B 1 having for destination address at the link level the multicast address deduced from step 106 of FIG. 4a.
• the module I 41 relays the frame to the intercepted I 5 sending module for switching frames to the port so that the. the aforementioned frame is switched to its new destination, that is to say the unicast address at the link level of the potential multicast receiver terminal T y .
• the rising filter A 1 can be maintained throughout the session, multicast, in order to intercept the multicast signaling messages from the potential multicast receiver terminal T y .
• This advantageous implementation variant is represented by the feedback loop of the test 104, in negative response to the type of message, to the test 102 in FIG. 4a.
• the aforementioned signaling messages allow the module and the reliability of the transmission system of a shared network multicast stream object of the invention, maintain and, if necessary, adapt each downlink filter B 1 and the rules of corresponding substitutions C 1 .
• step 4b the operations of recovery and analysis of frames in step 111 and application of the substitution rule C 1 to step 112, then the return of the frame to the
• the ports for step switching 113 executed respectively by the modules Ij 2 , I 6 , I 4 i and I 5 are of course executed for each substituted multicast frame, this successive operation being represented by the feedback loop between step 113 of FIG. FIG. 4b and the presence test 110 of the downward filter B 1 on the port P 1 to which the multicast server MS is connected.
• the reliability module 1 object of the invention allows to adapt to these changes in situation and, in particular , to adapt the B-type descending filters already in use or to add new filters.
• the upstream filter A 1 for intercepting the multicast signaling messages remains and is maintained in place throughout a multicast session or finally a plurality of multicast sessions.
• the above-mentioned amount filter thus makes it possible, throughout a multicast transmission, to filter and intercept the messages relating to:
• the new address is stored in the database DB by means of the storage / extraction module I 0 represented in FIG. 3b as previously described.
• this new multicast address is mapped to the upstream filter A 1 as well as to the unicast address of the potential multicast receiver terminal T y already stored.
• steps G of FIG. 4a is carried out in accordance with FIG. 4b and continued as described previously in the call description of step 107 for the calculation of a filter B 2 , a separate filter of the filter B 1 , then placing the downward filter B 2 in step 108 on the port P 1 or on a separate port on which the multicast server MS or another server is logically connected.
• Step 108 is followed by a step 109 of calculating another substitution rule C 2 of the step 110 of presence test of the downward filter B 2 on the relevant output input port and then by the execution of the steps 111, 112 and 113 to each frame filtered by the downlink filter B 2 , applying the substitution rule C 2 and corresponding forwarding of the frame to the ports for switching to step 113 for transmission of each substituted multicast frame conforming to the substitution rule C 2 established in step 109.
• the registration of the potential multicast receiver terminal T y to a new multicast group address group different from the previous one results in the introduction of a new substitution rule C 2 and the setting up of a new filter type B 2 .
• the frame containing the end-of-session message is intercepted by the ascending filter A 1 .
• the module I 6 for analysis of the filtered frames analyzes the aforementioned frame and detects the "withdrawal" type of signaling message.
• the aforementioned frame is copied intercepted by the module 6 I frames analysis and the original frame is returned to the module I 5 for transmission of switching frames to the port, which then proceeds to step 114 to transmit the frame towards the SPIM ports management software infrastructure; i -r- the copied frame is sent to the module I 30 for recovering higher level multicast address at the link level, the module I 30 supra then proceeding to step 114 for extracting the top-level multicast address at the link level, address of the multicast group that the potential multicast receiving terminal wishes to leave.
• the link-level multicast address deduction module I 31 derives the link-level multicast address from the higher-level multicast address at the aforementioned link level according to a rule already known as such. This operation is carried out in step 115 of FIG. 4c.
• step 115 and from the multicast address at the link level, and the identifier of the upstream filter A 1 , the module 1 for making the transmission of a transmission
• Step 116 is then followed by a step 117 consisting in determining, from the link-level multicast address and the identifier of the filter A 1 contained in the database DB, the descending filter B 1. to remove on the port P 1 , which is connected to the multicast server MS.
• the descending filter B 1 is removed by deactivation by the modulated 1 ⁇ of placement of the filters at the link level.
• Step 117 may be followed by a test step 118 allowing for. to check if there is another substitution rule, such as the rule C 2 above, relating to the unicast address of the potential multicast receiver terminal T y .
• This operation is symbolized by the symbolic relation:
• the potential T receiver terminal is having left all multicast groups to which it was registered, this terminal can be managed like any terminal and subjected to monitoring for new launch of the multicast procedure / unicast, as shown in Figure 4a by the module 1 and the reliability system of the transmission of a shared network multicast stream, in accordance with the object of the present invention.
• FIG. 5 represents a transmission frame of a multicast stream obtained thanks to the implementation of the method that is the subject of the invention.
• This frame constitutes. a substituted multicast frame having a link-level unicast address, the UNA-address y , a link-level header Suite, the network-level multicast destination address, the MUA-group address x , a continuation of the network-level header, a data field, multicast data, a network-level end-of-packet field, and a link-level end-of-field. . ,

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