Method for distributed multicast routing in connection-oriented networks and network for applying this method

1. A method of multicast routing for a telecommunications network comprising a plurality of communication nodes interconnected by multiple paths, for establishing a multicasting connection between a source node and a plurality of destination nodes, comprising the steps of:

a) making the source node generate a destination notification message which is propagated in the network until the destination notification message reaches the destination nodes, to inform the destination nodes of a need to connect to the source node;

b) making each destination node generate, on receipt of the destination notification message, a connection request message requesting establishment of the connection and containing information on weighted connection costs;

c) propagating the connection request message in the network towards the source node, while collecting further information on the weighted connection costs accumulated along a path; and

d) receiving at the source node the connection request messages propagated in the network from the destination nodes, selecting multicasting paths with satisfactory costs according to the information received from the source node with the connection request messages, and making the multicasting connection along the multicasting paths selected in this way, so that the multicasting connection is established for multicasting data from the source node to the destination nodes.

2. The method according to claim 1 , in which the connection request message which is sent by the destination nodes and which is propagated in the network towards the source node contains at least the following information:

i) Previous Hop (PH): address of a device node sending the message;

ii) D r : set of the destination nodes which can be reached via the PH; and

iii) Accumulated Cost (AC): sum of the costs of the connections along which the message passes from D r to the device node.

3. The method according to claim 2 , in which a node which receives information propagated from the destination nodes extracts useful information and stores the useful information in a receive table, and in which the node calculates, from the receive table, a send table, from which new information is extracted and propagated in the network towards the source node.

4. The method according to claim 3 , in which the receive table has a generic i-th input having the following fields:

i) the D r ;

ii) AC r =accumulated cost of the path from this node to all the nodes in the D r ;

iii) the PH; and

iv) E n =unique identifier of the input in the table.

5. The method according to claim 4 , in which the send table is obtained from the receive table by closure with respect to a combination of the discrete sets D r , and has the following properties:

i) for each set R of indices such that ∩ R D r =ø, there is an index m such that D m =∪ R D r ,

ii) for each set R of indices and for each index m such that ∩ R D r =ø and D m =∪ R D r , it is true that AC m ≦Σ R AC r .

6. The method according to claim 5 , in which, when a node receives a multicast connection creation request message, it takes the set of nodes D r which can be reached by the PH from the address field, and then looks in its send table to find an input i in the table with D i =D r ; if the input exists and AC i <AC r , the message is automatically rejected; otherwise, the i-th input in the receive table is replaced and/or supplemented with the information in the message.

7. The method according to claim 6 , in which the node, in order to update its send table, tests all the possible combinations with an empty intersection between the new record and all the records in the table; if one or more of the combinations matches the properties of the send table, they are added or substituted in it; otherwise, they are rejected.

8. The method according to claim 5 , in which the send table has an additional field (DF) indicating a set of records in the receive table from which it has been derived.

9. The method according to claim 8 , in which, for the propagation of the multicast connection creation requests, whenever a record of the send table is updated and/or created in one node, a creation request message is sent to all the neighboring nodes, with the exclusion, if necessary, of the PH of the inputs of the receive table indicated by the DF field.

10. The method according to claim 3 , in which, when the messages arrive at the source node, the source node selects the path between the source node and the destination nodes by selecting, among the records in its receive table, the one having all the desired destination nodes in the D r field and having the lowest total cost AC.

11. A telecommunications network, comprising: a plurality of communication nodes interconnected by multiple paths, for the establishment of a multicasting connection between a source node and a plurality of destination nodes, in which a method according to claim 1 is performed for the multicast routing.