System-wide synchronized switch-over of multicast flows

1. A network device, comprising:

multiple ports, for communicating over a communication network; and

packet processing circuitry, configured to:

receive via the ports packets belonging to a plurality of multicast flows;

receive, for each of the multicast flows, (i) a first configuration that specifies a respective first group of clients that are to receive the multicast flow prior to a specified switch-over time, and (ii) a second configuration that specifies a respective second group of clients that are to receive the multicast flow after the specified switch-over time;

forward the multicast flows via the ports in accordance with the first configuration;

extract from a field in at least one of the packets a value that is indicative of the switch-over time; and

based on the extracted value, switch-over forwarding of each of the multicast flows from the respective first group of clients to the respective second group of clients at the switch-over time, simultaneously both (i) for all the clients associated with each multicast flow and (ii) for all the multicast flows forwarded by the network device.

2. The network device according to claim 1 , wherein the multicast flows comprise Real-time Transport Protocol (RTP) media flows, and wherein the extracted value comprises an RTP timestamp.

3. The network device according to claim 1 , wherein the multicast flows convey video frames, and wherein the packet processing circuitry is configured to determine a video-frame boundary based on the extracted value, and to switch-over to the second configuration at the video-frame boundary.

4. The network device according to claim 1 , wherein the packet processing circuitry is configured to extract the value from a single selected multicast flow, and to switch-over all the multicast flows to the second configuration at the switch-over time indicated by the single selected multicast flow.

5. The network device according to claim 1 , wherein the packet processing circuitry is configured to determine the switch-over time, and to switch-over to the second configuration, irrespective of time synchronization with any other network device.

6. The network device according to claim 1 , wherein the packet processing circuitry comprises a table, which holds a rule that triggers a switch-over to the second configuration based on the extracted value.

7. The network device according to claim 6 , wherein the packet processing circuitry is configured to delete the rule from the table after the switch-over to the second configuration has been triggered.

8. The network device according to claim 1 , wherein the packet processing circuitry is configured to forward the multicast flows by looking-up a table, which points to the first configuration prior to the switch-over time and to the second configuration after the switch-over time.

9. The network device according to claim 8 , wherein, in response to a decision to switch-over to the second configuration, the packet processing circuitry is configured to update the table to point to the second configuration.

10. A method, comprising:

receiving in a network device packets belonging to a plurality of multicast flows;

receiving in the network device, for each of the multicast flows, (i) a first configuration that specifies a respective first group of clients that are to receive the multicast flow prior to a specified switch-over time, and (ii) a second configuration that specifies a respective second group of clients that are to receive the multicast flow after the specified switch-over time;

forwarding the multicast flows in accordance with the first configuration;

extracting from a field in at least one of the packets a value that is indicative of the switch-over time; and

based on the extracted value, switching-over forwarding of each of the multicast flows from the respective first group of clients to the respective second group of clients simultaneously at the switch-over time, simultaneously both (i) for all the clients associated with each multicast flow and (ii) for all the multicast flows forwarded by the network device.

11. The method according to claim 10 , wherein the multicast flows comprise Real-time Transport Protocol (RTP) media flows, and wherein the extracted value comprises an RTP timestamp.

12. The method according to claim 10 , wherein the multicast flows convey video frames, and wherein switching-over to the second configuration comprises determining a video-frame boundary based on the extracted value, and switching-over to the second configuration at the video-frame boundary.

13. The method according to claim 10 , wherein extracting the value comprises extracting the value from a single selected multicast flow, and wherein switching-over to the second configuration comprises switching-over all the multicast flows to the second configuration at the switch-over time indicated by the single selected multicast flow.

14. The method according to claim 10 , and comprising determining the switch-over time, and switching-over to the second configuration, by the network device irrespective of time synchronization with any other network device.

15. The method according to claim 10 , wherein switching-over to the second configuration comprises looking-up a table, which holds a rule that triggers a switch-over to the second configuration based on the extracted value.

16. The method according to claim 15 , and comprising deleting the rule from the table after the switch-over to the second configuration has been triggered.

17. The method according to claim 10 , wherein forwarding the multicast flows comprises looking-up a table, which points to the first configuration prior to the switch-over time and to the second configuration after the switch-over time.

18. The method according to claim 17 , and comprising, in response to a decision to switch-over to the second configuration, updating the table to point to the second configuration.