Delayed updating of forwarding databases for multicast transmissions over telecommunications networks
A switch ( 110 R. 3 ) uses a forwarding database ( 140 F) to forward multicast packets. The switch participates in a multicast protocol (e.g. PIM) with other switches, and also uses a snooping database (e.g. for IGMP snooping) to learn about local group members, i.e. members for which the router serves as a local multicast router (e.g. the local members do not participate in the multicast protocol). When the switch learns of a local member of a multicast group, the switch updates the snooping database but may or may not install the snooping information in the forwarding database. Thus, the forwarding database is not necessarily provisioned for locally sourced data packets addressed to the group until receipt of a locally sourced data packet addressed to the group. If no such packets are received, the forwarding database is not provisioned for such packets, and therefore its size is reduced. Other features are also provided.
1. A method comprising operating a first switch which is one of a first set of network nodes which are network switches, wherein the first switch is operable to forward multicast data packets received from nodes of the first set and also from nodes of a second set which is a set of one or more network nodes, wherein each node of the second set is not in the first set;
wherein the first switch is operable to classify an incoming multicast data packet as being of a first type or a second type, wherein:
the first type comprises only multicast data packets received from one or more nodes of the first set;
the second type comprises multicast data packets received from one or more nodes of the second set but does not comprise any multicast data packet received from any node of the first set;
wherein the first switch uses a forwarding database to make forwarding decisions, the forwarding database being for providing the forwarding decisions for packets of the first type (“first-type data packets”) and of the second type (“second-type data packets”);
wherein operating the first switch comprises:
the first switch receiving an indication for an additional recipient of data packets addressed to a multicast group, the additional recipient being in the second set;
in response to the indication, the first switch provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of first-type data packets addressed to the multicast group, but the first switch not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of data packets of a third type (“third-type data packets”) that are addressed to the multicast group, wherein each data packet of the third type is also of the second type;
wherein after receiving the indication, the first switch does not provision the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group if the first switch does not receive a third-type data packet addressed to the multicast group;
wherein after receiving the indication, the first switch provisions the forwarding database to provide forwarding decisions for forwarding to the additional recipient of at least some third-type data packets addressed to the multicast group if the first switch receives a third-type data packet addressed to the multicast group, and wherein the third type consists of data packets received on an interface operable to receive multicast data packets from at least one node of the second set.
2. The method of claim 1 further comprising:
(a) the first switch receiving a third-type data packet addressed to the multicast group; and
(b) in response to receiving the third-type data packet addressed to the multicast group, the first switch provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group that are received by the first switch from a node from which the third-type data packet was received in operation (a).
3. The method of claim 1 wherein the third type consists of data packets received from a selected node of the second set.
4. The method of claim 1 wherein: the first type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the first set; the second type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the second set.
5. The method of claim 1 wherein the nodes of the first set exchange control messages with each other according to a first protocol for setting up distribution paths for distributing multicast data packets through the first set;
wherein the control messages of the first protocol are not addressed to any node of the second set.
6. The method of claim 5 wherein the first protocol is sparse-mode PIM (Protocol Independent Multicast) protocol.
7. The method of claim 5 wherein the second set does not use the first protocol.
8. The method of claim 1 wherein not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets increases available space in the forwarding database.
9. A first switch which is a network switch operable to be configured as one of a first set of network nodes which are network switches, wherein the first switch is operable to forward multicast data packets received from nodes of the first set and also from nodes of a second set which is a set of one or more network nodes, wherein each node of the second set is not in the first set;
wherein the first switch is operable to classify an incoming multicast data packet as being of a first type or a second type, wherein:
the first type comprises only multicast data packets received from one or more nodes of the first set;
the second type comprises multicast data packets received from one or more nodes of the second set but does not comprise any multicast data packet received from any node of the first set;
wherein the first switch is operable to use a forwarding database to make forwarding decisions, the forwarding database being for providing the forwarding decisions for packets of the first type (“first-type data packets”) and of the second type (“second-type data packets”);
wherein the first switch is operable to perform operations of:
receiving an indication for an additional recipient of data packets addressed to a multicast group, the additional recipient being in the second set;
in response to the indication, provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of first-type data packets addressed to the multicast group, but not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of data packets of a third type (“third-type data packets”) that are addressed to the multicast group, wherein each data packet of the third type is also of the second type;
after receiving the indication, not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group if the first switch does not receive a third-type data packet addressed to the multicast group;
after receiving the indication, provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of at least some third-type data packets addressed to the multicast group if the first switch receives a third-type data packet addressed to the multicast group,
wherein the third type consists of data packets received on an interface operable to receive multicast data packets from at least one node of the second set.
10. The first switch of claim 9 wherein the first switch is operable to:
(a) receive a third-type data packet addressed to the multicast group;
(b) in response to receiving, from a specific node of the second set, the third-type data packet addressed to the multicast group, provision the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group that are received by the first switch from a node from which the third-type data packet was received in operation (a).
11. The first switch of claim 9 wherein the third type consists of data packets received from a selected node of the second set.
12. The first switch of claim 9 wherein: the first type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the first set; the second type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the second set.
13. The first switch of claim 9 wherein the nodes of the first set are to exchange control messages with each other according to a first protocol for setting up distribution paths for distributing multicast data packets through the first set;
wherein the control messages of the first protocol are not addressed to any node of the second set.
14. The first switch of claim 13 wherein the first protocol is sparse-mode PIM (Protocol Independent Multicast) protocol.
15. The first switch of claim 13 wherein the second set does not use the first protocol.
16. A non-transitory computer readable medium comprising computer instructions for causing a first switch, which is a network switch, to operate as one of a first set of network nodes which are network switches, wherein the computer instructions are for causing the first switch to forward multicast data packets received from nodes of the first set and also from nodes of a second set which is a set of one or more network nodes, wherein each node of the second set is not in the first set;
wherein the computer instructions are for causing the first switch to classify an incoming multicast data packet as being of a first type or a second type, wherein:
the first type comprises only multicast data packets received from one or more nodes of the first set;
the second type comprises multicast data packets received from one or more nodes of the second set but does not comprise any multicast data packet received from any node of the first set;
wherein the computer instructions are for causing the first switch to use a forwarding database to make forwarding decisions, the forwarding database being for providing the forwarding decisions for packets of the first type (“first-type data packets”) and of the second type (“second-type data packets”);
wherein the computer instructions are for causing the first switch to perform operations of:
receiving an indication for an additional recipient of data packets addressed to a multicast group, the additional recipient being in the second set;
in response to the indication, provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of first-type data packets addressed to the multicast group, but not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of data packets of a third type (“third-type data packets”) that are addressed to the multicast group, wherein each data packet of the third type is also of the second type;
after receiving the indication, not provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group if the first switch does not receive a third-type data packet addressed to the multicast group;
after receiving the indication, provisioning the forwarding database to provide forwarding decisions for forwarding to the additional recipient of at least some third-type data packets addressed to the multicast group if the first switch receives a third-type data packet addressed to the multicast group,
wherein the third type consists of data packets received on an interface operable to receive multicast data packets from at least one node of the second set.
17. The medium of claim 16 wherein the computer instructions are for causing the first switch, upon receipt from a specific node of the second set of a third-type data packet addressed to the multicast group, to provision the forwarding database to provide forwarding decisions for forwarding to the additional recipient of the third-type data packets addressed to the multicast group that are received by the first switch from the specific node.
18. The medium of claim 16 wherein the third type consists of data packets received from a selected node of the second set.
19. The medium of claim 16 wherein: the first type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the first set; the second type consists of data packets received on any interface operable to receive multicast data packets from at least one node of the second set.
20. The medium of claim 16 wherein the nodes of the first set are to exchange control messages with each other according to a first protocol for setting up distribution paths for distributing multicast data packets through the first set;
wherein the control messages of the first protocol are not addressed to any node of the second set.
21. The medium of claim 20 wherein the first protocol is sparse-mode PIM (Protocol Independent Multicast) protocol.
22. The medium of claim 20 wherein the second set does not use the first protocol.