Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L45/00—Routing or path finding of packets in data switching networks

Definitions

• the present invention relates to a method of marking a datagram transmitted in a communication network of the IP (“Internet Protocol”) type. It also relates to a transmission method which can use a marking of a datagram thus carried out.
• IP Internet Protocol
• the identification of the path followed by a datagram in a communication network is an important issue for several aspects. This concerns, in particular, certain services intended to guarantee transmission quality guarantees. For example, it is preferable that successive datagrams of the same flow follow the same path in the network, in order to avoid that the order of arrival of the datagrams at the destination terminal is different from the order of sending of the same datagrams by the5 transmitting terminal.
• a transmission method exists, according to which the path followed by a datagram in the network is registered in the datagram by the terminal transmitting the datagram.
• This process is known as "source routing".
• a drawback of this method comes from the fact that the terminals 0 do not know the network topology, that is to say that they do not know the available or unavailable links of the network.
• the path entered in the datagram is definitively fixed at the time of the transmission of the datagram by the transmitting terminal, and no subsequent modification of the path is possible depending on the possible unavailability of certain links in the network.
• This transmission method therefore does not make it possible to activate adaptive mechanisms of the routing function in IP networks.
• the use of the “source routing” method does not reduce the risk of the appearance of congestion phenomena in the network, that is to say situations according to which the number of datagrams to be routed by a determined link. of the network reaches or exceeds the maximum transmission capacity of this link.
• the path registered in a datagram cannot contain more than nine routers, because of the size of the field of the datagram in which this path is registered.
• the “source routing” process lacks security, in the sense that the source IP address of the first datagrams can be usurped to cross an access control system based on this address. Second datagrams sent in response to the first datagrams also using the “source routing” process can then be diverted. According to a known method of identifying the path followed by a datagram in a network, called "record routing", each router through which a datagram passes inscribes its IP address in this datagram, following the address entered by the previous router on the path followed by the datagram.
• a traceability of the path followed is thus obtained, by reading the series of addresses entered in the datagram.
• This method of identifying the path followed has the disadvantage of not making it possible to orient a datagram at the level of a router as a function of data external to this router at the time of the transmission of the datagram.
• the number of routers of the path followed by a datagram registered in this datagram according to the “record routing” method is limited to nine routers.
• An object of the present invention is to develop a marking of a datagram transmitted in a communication network, which does not have the drawbacks of the “source routing” and “record routing” methods indicated above.
• the invention provides a method of marking a datagram transmitted in a communication network comprising routers connected together by transmission links.
• the datagram is transmitted from a terminal sending the datagram connected to a first network router to a terminal receiving the datagram connected to a second network router.
• the datagram comprises a vector formed of ordered fields each containing a reference and a vector index field.
• each router in the network has a table of references.
• the marking process comprises the following steps, when a router receives the datagram: - reading a value in the index field of the datagram, - reading the reference contained in the vector field of the datagram designated by the value d 'index read; - if the router table does not contain the reference read, writing, in the vector field of the datagram designated by the index value read, of a reference selected in the router table; - entry, in the index field of the datagram, of a value equal to the value read incremented by one; and - transmission of the datagram to a next router on the network.
• the recording of a new reference in the datagram by a router is not systematic.
• the reference read which constitutes data external to the router during the transmission of the datagram, is preferred to remain registered in the datagram.
• the registration by the router of a new reference occurs when the reference read is not contained in the router reference table.
• the router is then autonomous in selecting, in its reference table, the new reference to be entered in the datagram.
• the references entered in the vector fields of the datagram are each identical to a reference contained in the reference table of a router having transmitted this datagram. More precisely, the reference registered in the n th field of the vector is contained in the table of the n th router located on the path followed by the datagram in the network, n being a value taken by the vector index of the datagram during the transmission of it in the network.
• each reference identifies a route along which the datagram was transmitted by a router
• knowledge of the meaning of the references in the table of each router makes it possible to reconstruct the path followed by the datagram in the network.
• the marking method according to the invention is safe, because the mere reading in the datagram of the references written in the fields of the vector is not sufficient to obtain significant information. It is also essential to know the meaning of the references for each router. Intercepting a datagram without having this knowledge does not allow an exploitation of the references registered in this datagram.
• the reference read by the router is identical to a registered reference by this router during the transmission of an earlier datagram of said stream. If the network has stable operation, that is to say that no breakdown or congestion of certain network links occurs, which affects a router through which said previous datagram has passed, the same reference contained in the table a router through which several successive datagrams of the flow pass is then associated with all these datagrams. An identical marking is thus obtained along the path followed by the successive datagrams of the flow, to which a specific processing associated with this flow can be attached.
• the invention also relates to a method of transmitting a datagram in which route references are written.
• These references may have been previously entered in the datagram using a marking process as described above, but not necessarily. They may also have been entered in the datagram by another method, such as, for example, a “source routing” type method.
• a knowledge of the network topology by the terminals is necessary, as well as a knowledge by the terminals of the reference tables of the routers.
• a network router has a table of references associated with respective routes between this router and a destination terminal of the datagram connected to the network.
• the reference table is associated with a unique destination prefix contained in a routing table of the router.
• the datagram transmission method then includes the following steps: - when the datagram is received by the router, reading a reference in the datagram; and - search for the reference read from the router reference table,. if the table contains the reference read, transmission of the datagram along the route with which the reference read is associated,. otherwise, selection of a reference in the table, and transmission of the datagram along the route with which the selected reference is associated.
• a transmission method according to the invention is implemented at the level of the IP protocol layer.
• a first advantage of such a transmission method lies in the fact that it requires only an adaptation of the IP layer, without modification of the other layers of protocols implemented in the routers. An existing communication network can therefore be easily adapted for the implementation of such a transmission method.
• a second advantage of a transmission method according to the invention comes from the fact that it allows an initial qualification of the path followed by a datagram in the network.
• the transmission of a datagram by a router takes priority into account a route reference read in this datagram.
• successive datagrams of the same stream, transmitted by a given transmitting terminal bound for a given receiving terminal are transmitted in the network along identical routes, if these datagrams contain, during their transmission by the transmitting terminal , with the same references, and if the network has stable operation.
• the reference table of a router does not contain the reference read from a datagram, this router selects a route from possible routes to transmit the datagram.
• the transmission method of the invention therefore conforms to the main mode of operation of an IP network, by independent elementary transmissions, designated by "hop by hop” in English.
• the reference selected in the reference table of the router is also written into the datagram using a marking method as described above.
• marking and transmission methods according to the invention are simultaneously implemented within an IP network, in addition to the functions of transmitting datagrams and knowing the network topology, the routers can modify the references of registered routes in datagrams. Initial references can be entered in the datagrams by the terminals, without knowledge of the network topology. To this end, the terminals can store references read in a received datagram, in order to use these read references as initial references for an emitted datagram.
• the router reference table further comprises, for each reference of said table, a load rate value assigned to the route to which said reference is associated.
• the load rate of a route characterizes the amount of traffic carried along this route.
• the invention also relates to a terminal adapted to implement a marking process as described first.
• a terminal comprises: - means for producing a datagram intended to be transmitted by the terminal, the datagram comprising a vector of ordered fields and a vector index field; means for registering an initial reference in each field of the datagram vector intended to be transmitted by the terminal; and - means for registering an initial value in the index field of the datagram intended to be transmitted by the terminal.
• the terminal further comprises: - means for reading second references in fields of an additional vector contained in a datagram received by the terminal; and - means for storing, in a table of communication session contexts of said terminal, second references with communication session context data of the received datagram, so that the initial reference entered in each field of the vector of the datagram intended to be sent by the terminal is a so-called second reference read in a field of the additional vector of the received datagram, when the datagram intended to be sent belongs to the communication session of the received datagram.
• previously determined route references can be used for the datagram intended to be transmitted.
• the means for producing the datagram intended to be transmitted can be adapted so that the datagram intended to be transmitted further comprises an additional vector of fields.
• the terminal then further comprises: - means for reading first references in fields of a vector contained in the received datagram; means for storing, in the table of contexts of communication sessions of said terminal, said first references with the communication session context data of the received datagram; and means for registering said first references in the fields of the additional vector of the datagram intended to be sent by the terminal, when the datagram intended to be sent belongs to the communication session of the received datagram.
• the invention further relates to a router suitable for implementing a transmission method as described secondly.
• Such a router comprises: means for reading a value in a vector index field of a datagram received by the router; means for reading a reference contained in a vector field of said datagram designated by the index value read; - means for storing a reference table; - means for associating the references contained in the table with respective routes; means for searching for a read reference, in the reference table of said router, arranged to control a transmission of said datagram along the route with which the read reference is associated, if the reference table contains the read reference; means for selecting a reference in the reference table, arranged to be activated if the reference table does not contain the reference read, and arranged to control a transmission of said reference datagram along the route to which the selected reference is associated; and means for recording, in the index field of said datagram, a value equal to the value read incremented by one.
• the association means are included in means for calculating a routing table of this router.
• the calculation means belong to a control unit of the router.
• the router can be adapted to simultaneously implement a method of marking a datagram passing through this router, as described first. For this, it further comprises means for writing the reference selected in the vector field of the datagram designated by the index value read. Even if the combination within the same router of the implementation of the marking and transmission methods which are the subject of the invention is particularly advantageous for obtaining an efficient operation of the network, the router may include means for implementing the method regardless of the presence, in this same router, of datagram marking means. And vice versa.
• a router which combines implementations of the two methods, some of the means mentioned above for each method may be common to the two methods.
• the invention finally relates to a communication network which comprises a router as described above.
• FIG 1 shows a communication network in which the invention can be implemented
• - Figure 2 illustrates the structure of an IP datagram header as used for an implementation of the invention
• - Figures 3a and 3b intended to be associated, illustrate different stages of a transmission according to the invention of several datagrams, within a network as shown in Figure 1
• - Figure 4 is a flow diagram of a method of transmitting a datagram according to the invention.
• a communication network by transmission of datagrams 100 comprises routers 4-9 linked together by transmission links.
• a chain of routers forms a route in the network 100, to transmit a datagram.
• Each router can include a routing unit (or
• Forming unit which transfers the datagrams between two links linked to this unit, and a command unit (or “control unit”) which supervises the activity of the routing unit.
• control unit which supervises the activity of the routing unit.
• the routing unit and the control unit are respectively referenced 5a and 5b. Terminals are connected to some of the routers in network 100.
• terminals can be of different types, such as, for example, computer units, mobile communication units, etc.
• computer units 1 and 10 are connected to routers 4 and 7, respectively.
• Data produced by terminal 1 and intended for terminal 10 is distributed by terminal 1 in IP datagrams.
• IP datagrams are transmitted by some of the routers of the network 100 to the terminal 10. It is considered below that the operation of an IP type network is known.
• each transmission link of the network 100 is identified by a prefix DP, followed by identifiers of each of the routers or terminals connected to this link.
• Each IP datagram has a header as shown in Figure 2, for version 4 of the IP protocol (IPv4).
• IPv4 IP protocol
• the header includes a basic header part Bl present in all the datagrams, and an optional header part B11.
• the header part B1 has a fixed length of 20 bytes.
• the header part B11 can have a variable length.
• Among the fields of the header part B1 appear the field "SOURCE ADDRESS", in which the IP address of the terminal sending the datagram is indicated, and the “DESTINATION ADDRESS” field, in which the IP address of the terminal receiving the datagram is indicated.
• Other fields include: - the “Type Of Service”, or TOS, field in which the way in which the datagram is to be managed is specified; - the "TOTAL LENGTH” field, in which the total length of the datagram is specified; - the "ID” field intended to receive an identification number of the datagram, in particular with a view to possible fragmentation of the datagram; - the “TTL” or “TIME TO LIVE” field, in English, in which is indicated a maximum duration of existence of the datagram being routed in the network; and - the “PROTOCOL” field, in which the high-level protocol to which the data placed by the sending terminal in the datagram data field (or “payload”, in English, and not shown in FIG. 2) is indicated. ).
• the header part B11 comprises a first field denoted “OPT. TYPE ", 1 byte. This field is intended to receive a reference constructed according to a nomenclature known to those skilled in the art. This reference specifies the presence, the class and a dedicated option number, which make it possible to identify the nature of the content of the header part Bll. By way of example, for the embodiment of the invention described below, this reference can be 10011001 in binary representation of the byte. The length of the header part B11, expressed in bytes, is indicated in the "OPT.” LENGTH ”(1 byte). For the implementation of the invention described here, the maximum possible length for the header part B11 is used, namely 40 bytes.
• the 38 bytes remaining available in the header part B11 are divided into four fields arranged as follows: - a first field denoted FVI, for “Forward Vector Index” in English, of 1 byte, intended to receive a value digital index; - a second field denoted BVL, for “Backward Vector Length”, also of 1 byte, intended to receive a value of vector length; - a first ordered series of 36 fields, noted FFIV, for "Forward Flow Identifier Vector", of 18 bytes in total.
• the fields of this first series arranged one after the other, form a first vector and are intended to receive 36 first digital references, coded on 4 bits each.
• the index and the first vector are respectively designated below by the FVI index and the FFIV vector.
• the FVI index is used to locate a field in the FFIV vector, by the sequence number of the position of this field in the FFIV vector, counted from the start of the vector.
• the value of the FVI index varies between 1 and 36.
• a second ordered series of fields denoted BFIV, for "Backward Flow Identifier Vector", also of 18 bytes in total. This second series of fields is organized in the same way as the first series of fields.
• the BFIV fields form a second vector and are intended to receive 36 second digital references coded on 4 bits each.
• This second vector which corresponds to the additional vector mentioned in the general description of the invention, is designated hereinafter by BFIV vector.
• BFIV vector This second vector, which corresponds to the additional vector mentioned in the general description of the invention, is designated hereinafter by BFIV vector.
• the positions of the fields FVI and BVL, as well as those of the fields of the vectors FFIV and BFIV shown in FIG. 2 are given by way of example. Other positions can be chosen, in order to obtain alternative embodiments of the invention. Such alternative modes of implementation are also included in the invention. However, it is particularly advantageous, in the context of the IPv4 version of the IP protocol, to design the FVI and BVL fields, as well as the FFIV and BFIV vector fields, so as to exploit the maximum length of the part of- Bll head.
• IPv6 IP protocol
• FIB table for "Forwarding Information dataBase” in English.
• Table 1 below represents a part of such a routing table, established by way of example for router 5 in FIG. 1:
• the FIB table must be read in rows, each row corresponding to a route.
• the second line characterizes the direction to take, that is to say the IP address of the following router, ie DP_5_6: 6, to reach the destination prefix DP_7_10.
• the first column of the FIB table entitled “Destination Prefix” in English, groups DP destination prefixes.
• the destination prefix noted DP_7_10 corresponds to the interconnection subnet between router 7 and terminal 10.
• the second column of the FIB table entitled “Next Hop", indicates an IP address of a router or terminal connected to router 5 by a single transmission link, for each destination prefix indicated in the first column.
• IP addresses are constructed in a known manner, with a DP prefix followed by an identifier of the terminal or the router.
• the columns “Interface” and “Encapsulation L2” give useful information for the transmission of the datagram, without relation to the invention.
• the IP address of the terminal receiving this datagram is read in the "DESTINATION ADDRESS" field in the header part B1 of the datagram.
• the destination prefix of the address read is isolated using a network mask, and is identified with one of the destination prefixes contained in the first column of the FIB table according to a principle of greater coincidence, or "longest match" in English.
• the FIB table of each router is completed in the following manner, illustrated by table 2 below. Table 2 also represents a part of the FIB table, established by way of example for router 5 (see FIG. 1):
• a FIB table conforming to table 2 has two additional columns.
• the first column contains route references, and is titled “Ref.”
• the second column titled “Load”, contains load rate values.
• a FIB table conforming to table 1 indicates a single possibility of transmission of a datagram by the router, for each destination prefix.
• an FIB table conforming to table 2 indicates a or several possibilities of transmitting a datagram for each destination prefix. Each possibility corresponds to a different route between the router concerned, that is to say the router 5 in the example considered, and the destination terminal whose IP address is read in the datagram.
• the “Ref.” Column associates a numerical reference to each of these routes.
• references distinguish the different routes taken into account in the FIB table, which correspond to the same destination prefix.
• the same reference can possibly be used several times in the FIB table, to designate routes corresponding to different destination prefixes.
• the references associated with the routes taken into account in the FIB table have only an identification function, and do not correspond to a classification.
• the references used depend on the modifications which have occurred in the FIB table during successive updates thereof, established by the control unit of the router.
• the reference table mentioned in the general description of the invention is formed by all of the rows of the FIB table which correspond to a single determined destination prefix.
• the reference table considered for a datagram whose destination prefix is DP_7_10 comprises the third to fifth rows of the FIB table, without counting the row of column names .
• the "Load" column indicates a value of load rate. This value is determined by the control unit based on network status data. Such data are, for example, load rate values of at least some of the links in network 100.
• the value indicated in the “Load” column for each row of the FIB table can be, for example, at the most large of the load rate values of all links along the route corresponding to this line.
• This communication session context includes in particular the following data: the respective IP addresses of the terminals 1 and 10, a transport protocol number (for example the TCP or UDP protocols) and source and destination port numbers.
• the data of the communication session context are stored in the terminal 1.
• the terminal 1 configures the header part B1 of this datagram. In particular, it registers the respective IP addresses of terminals 1 and 10 in the "SOURCE ADDRESS” and "DESTINATION ADDRESS" fields. It also configures the header part Bll, by entering the following initial values in the different fields: - OPT field. TYPE: 10011001 - OPT field.
• LENGTH 40 - FVI field: 1 - BVL field: 0 - FFIV vector fields: 0, 0 0 - BFIV vector fields: 0, 0 0
• 1 is the initial value of the index FVI
• 0 is the initial value entered in the BVL field.
• 0 is also the initial reference entered in all the fields of the vectors FFIV and BFIV.
• the reference 0 is reserved for the initialization function: it is not used in the router reference tables to identify a route.
• the initialization at 0 of the fields of the vectors FFIV and BFIV of a datagram by a terminal means that this datagram is either an isolated datagram, or a first datagram of a flow, or a datagram subsequent of a flow for which the transmitting terminal does not have predetermined initial references.
• These references entered in the fields of the vectors FFIV and BFIV of the datagram 20, as well as the values written in the fields FVI and BVL of the datagram 20, are stored by the terminal 1 with the data of the context of the communication session.
• the terminal 1 then transmits the datagram 20 to the router 4 (step B).
• the router 4 transmits the datagram 20 to the router 5 (step C).
• the router 4 writes the value 2 in the index field FVI of the datagram 20, as well as the reference 3, given by way of example, in the first field of the vector FFIV of the datagram 20.
• the method of transmission of the datagram 20, implemented within each router, is now described in detail for the router 5.
• the router 5 selects a line in its FIB table (table 2). This selection is made in two successive stages. During a first step of selecting a line from the FIB table, the router 5 reads the IP address of the destination terminal of the datagram 20 in the "DESTINATION ADDRESS" field of the header part Bl.
• the destination prefix isolates the destination prefix from this address, and compares it to the destination prefixes contained in the first column of the FIB table. According to the process of greatest coincidence (“longest match”), it selects from the FIB table the longest destination prefix which corresponds to that of the IP address of the destination terminal.
• the selected destination prefix is noted DP_7_10 (table 2).
• Router 5 first reads the value entered in the FVI index field of datagram 20 (step 30). The value read is 2. It then reads the reference contained in the field of the vector FFIV whose position within this vector corresponds to the value read in the FVI field (step 31). The reference 0 is thus read in the second field of the vector FFIV. Since the reference read is equal to the initialization reference (step 32a), the router 5 is then autonomous in determining the route along which it transmits the datagram.
• the router 5 registers the reference 4 in the field of the vector FFIV designated by the index FVI (second field of the vector FFIV - step 34 of FIG. 4). It then increments the value of the FVI index by one and writes the value obtained in the FVI field of the datagram 20 (step 35).
• the datagram 20 then contains the values and references indicated in FIG. 3a, for step D.
• the line of the FIB table which corresponds to the selected destination prefix and to the reference 4 is the selected line.
• Router 5 transmits datagram 20 according to the indication in the “Next Hop” column for the selected line. In the example described, it transmits the datagram 20 to the router 6.
• the routers 6 (step E of FIG. 3b) then 7 (step F) each transmit the datagram 20 by following a process identical to that described for the router 5.
• the terminal 10 receives the datagram 20 containing the index value FVI and the references, written in the fields of the vectors FFIV and BFIV, indicated in step G, by way of example.
• the terminal 10 stores the data of the context of the communication session of the datagram 20, read in the header part B1 of the datagram 20. It also stores, with these data, the contents of the fields FVI and BVL, as well as those FFIV and BFIV vector fields.
• the terminal 10 then reads the data contained in the data field (or “payload”) of the datagram 20. It is now assumed that the terminal 10 in turn produces data intended for the terminal 1, in response to the data carried by the datagram 20.
• the data produced by terminal 10 are transmitted in the context of the same communication session as that of the datagram 20.
• the datagram 20 therefore belongs to a go flow coming from this communication session, and new datagrams sent by the terminal 10 belong to a return flow from this session Communication.
• the terminal 10 creates a new datagram 21, by taking the data from the communication session context of the datagram 20 (step H of FIG. 3b).
• the datagram 21 has a structure identical to that of the datagram 20.
• the terminal 10 completes the fields of the header part B1 of the datagram 21 as described above for the terminal 1 and the datagram 20, by exchanging the data relating to the sending and receiving terminals. In addition, the terminal 10 retrieves, with the data of the stored communication session context, the references and values memorized during the reception of the datagram 20.
• the terminal 10 writes them in the fields of the header part Bll of the datagram 21 , as follows: - in the successive fields of the FFIV vector of the datagram 21: the references contained in the fields of the BFIV vector of the datagram 20, in the same order; - in the successive fields of the BFIV vector of the datagram 21: the references contained in the fields of the FFIV vector of the datagram 20, in the same order; and - in the BVL field of the datagram 21: the value read in the FVI field of the datagram 20.
• the terminal 10 writes the initial value 1 in the index field FVI of datagram 21 (step I).
• the transmission of the datagram 21 in the network 100 to the terminal 1 is carried out in a manner analogous to the transmission of the datagram 20 described above. It should be noted that the datagram 21 does not pass, a priori, by the same routers as the datagram 20, and that the numbers of routers through which each of the datagrams 20 and 21 respectively pass are a priori different. In FIGS. 3a and 3b, there is the number of routers through which the datagram 21 passes. The contents of the BVL field and BFIV vector fields of the datagram 21 are transported during the transmission of the datagram 21 in the network 100, without being used. The reception of the datagram 21 by the terminal 1 (step J of FIG.
• the references entered by the routers in the FFIV vector fields of the datagram 20, as well as the last value entered in the FVI index field of the datagram 20, ie the value entered by the router 7, are stored in the two terminals 1 and 10 with the data of the context of the communication session.
• the method now described applies to the situation where the terminal 1 produces new data intended for the terminal 10, in response to the data conveyed by the datagram 21.
• the terminal 1 then creates a datagram 22, according to the procedure already described, by taking the data from the stored communication session context (step K of FIG. 3a).
• the datagram 22 belongs to the same go flow pertaining to this communication session as the datagram 20.
• the terminal 1 enters, in the FVI field of the datagram 22, the initial value 1, and, in the BVL field of the datagram 22, the value y of the FVI index read in the datagram 21 upon reception of the latter by the terminal 1. It also writes, in the fields of the vector FFIV of the datagram 22, the references read in the fields of the vector BFIV of the datagram 21. From even, it inscribes in the fields of the vector BFIV of the datagram 22, the references read in the fields of the vector FFIV of the datagram 21. The values and references thus obtained for the fields of the datagram 22 are indicated in step L of FIG. 3a .
• the fields of the BFIV vector of said datagram are intended to receive references entered in the fields of a FFIV vector of a datagram of a return flow pertaining to said communication session, transmitted by the terminal receiving the datagrams of the outward flow, and received by the terminal transmitting the datagrams of the flow- go before the transmission of said go flow datagram.
• the BVL field of said go flow datagram is intended to receive the last value entered in the FVI field of said return flow datagram.
• the datagram 22 is transmitted to the router 4 by the terminal 1, then to the router 5 by the router 4 (step M), in the same way as the datagram 20.
• that -ci increments the value of the FVI index to 2.
• the router 4 also leaves the reference 3 written in the first field of the vector FFIV of the datagram 22.
• the description of the method of transmission of a datagram by a router of the network 100 is now completed, in the case of the datagram 22 transmitted by the router 5.
• the first step of selecting a line from the FIB table is identical to that described for the transmission of datagram 20.
• router 5 analyzes the FFIV vector of the datagram 22 according to the method of FIG. 4. It reads the reference indicated by the FVI index (steps 30 and 31). The reference read is 4, in accordance with the entry made by the router 5 in the datagram 20, during step D of the transmission of the latter. This reference read being different from the initialization reference 0 of the vector fields (step 32a), the router 5 examines whether the reference table determined during the first step of selecting a line of the FIB table contains the reference 4 (step 32b). Two situations can then arise: according to a first situation, the reference table still contains reference 4, and according to a second situation, it no longer contains reference 4.
• the first situation occurs, in particular, when the FIB table of router 5 has not been modified between the respective transmissions of datagrams 20 and 22. It intervenes also if the reference 4 has been maintained in the FIB table for the destination prefix DP_7_10 during updates of the FIB table which have occurred between the transmissions of datagrams 20 and 22.
• the FFIV vector is not modified by router 5, the FVI index is incremented (step 35), and router 5 transmits datagram 22 to router 6 (step 36).
• the transmissions of datagrams 20 and 22 by the router 5 are then identical.
• the second situation occurs when an update of the FIB table of router 5 has occurred between the transmission of datagram 20 and that of datagram 22.
• the router 5 has selected in its FIB table the two lines corresponding to the destination prefix DP_7_10. These two lines constitute the new reference table considered.
• the first of these two lines corresponds to the route reference 1, and the charge rate value indicated is 70%.
• the second of these two lines corresponds to the route reference 6, and the charge rate value indicated is 20%.
• the router 5 selects one of these two references for which the route has the minimum load rate value (steps 32b and 33): the reference 6.
• the combination of the marking and transmission methods of a datagram according to the invention provides the following advantages: when a new datagram belongs to a flow for which datagrams have already been transmitted, the use of a route followed by an earlier datagram of the same flow is preferred for the new datagram; - when the route used for the previous datagram of the stream is no longer available, the new datagram is transmitted according to a new route; and the new route is determined so as to distribute the datagram flows between different transmission links of the network according to their degrees of availability.
• This association combines transmission by independent elementary jumps (“hop by hop”) and a reduction in the risk of network congestion. Stable network operation results. It is understood that variants can be introduced with respect to the mode of implementation of the invention which has been described above.
• steps 32a and 32b can be grouped together in a single step, corresponding to the same test as that of step 32b.
• references written in a field of the vector FFIV or vector BFIV of a datagram, as well as a value written in the field FVI or BVL of a datagram can only be stored in one of the two terminals sender or recipient of this datagram.
• Such an implementation may, in particular, relate to a datagram belonging to a return flow.

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  • 2004-12-08 US US10/584,236 patent/US20070140265A1/en not_active Abandoned
  • 2004-12-08 WO PCT/FR2004/003157 patent/WO2005071902A1/fr active Application Filing
  • 2004-12-08 EP EP04805663A patent/EP1766889A1/de not_active Withdrawn

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