METHOD AND SYSTEM FOR HANDLING MULTICAST EVENT CONTROL SYMBOLS

1 . A packet switching system comprising:

a receive port;

a plurality of transmit ports;

a switch fabric for selectively coupling the receive port to the transmit ports;

a reference clock signal input; and

a multicast control symbol input/output port coupled to the receive port for outputting a received multicast control symbol and to the plurality of transmit ports for inputting a control signal to be transmitted, whereby multicast control symbols are synchronized to the reference clock signal.

2 . A system as claimed in claim 1 including a multicast control symbol generator coupled to the control symbol input/output port.

3 . A system as claimed in claim 2 including a reference clock coupled to the reference clock input.

4 . A system as claimed in claim 2 wherein the multicast control symbol generator includes a clock input for coupling to a reference clock.

5 . A system as claimed in claim 2 wherein the multicast control symbol generator does not include a clock input for coupling to a reference clock

6 . A system as claimed in claim 1 including a multicast control symbol acceptor coupled to the multicast control symbol input/output port.

7 . A system as claimed in claim 6 including a software receiver coupled to the multicast control symbol acceptor.

8 . A system as claimed in claim 6 including a hardware receiver coupled to the multicast control symbol acceptor.

9 . A system as claimed in claim 1 including a software multicast control symbol originator coupled to the receive port.

10 . A packet switching system comprising:

a first switch including a first receive port, a first plurality of transmit ports, a first switch fabric for selectively coupling the receive port to the transmit ports, a first reference clock signal input and a first multicast control symbol input/output port coupled to the first plurality of transmit ports for inputting a multicast control signal to be transmitted; and

at least one second switch including a second receive port, a second plurality of transmit ports, a second switch fabric for selectively coupling the receive port to the transmit ports, a second reference clock signal input and a second multicast control symbol input/output port coupled to the second receive port for outputting a received multicast control symbol,

whereby multicast control symbols are synchronized to a reference clock signal.

11 . A system as claimed in claim 10 including a multicast control symbol generator coupled to the first multicast control symbol input/output port.

12 . A system as claimed in claim 10 including a reference clock coupled to the first reference clock input.

13 . A system as claimed in claim 10 wherein the control symbol generator includes a clock input for coupling to a reference clock.

14 . A system as claimed in claim 11 including a control symbol acceptor coupled to the second multicast control symbol input/output port.

15 . A system as claimed in claim 14 including a software receiver coupled to the multicast control symbol acceptor.

16 . A system as claimed in claim 10 including a software multicast control symbol originator coupled to the first receive port.

17 . A method of operating a packet switching system comprising a first switch including a first receive port, a first plurality of transmit ports, a first switch fabric for selectively coupling the receive port to the transmit ports, a first reference clock signal input and a first multicast control symbol input/output port coupled to the first plurality of transmit ports for inputting a control signal to be transmitted; and at least one second switch including a second receive port, a second plurality of transmit ports, a second switch fabric for selectively coupling the receive port to the transmit ports, a second reference clock signal input and a second multicast control symbol input/output port coupled to the second receive port for outputting a received multicast control symbol, said method comprising the steps of:

generating a reference clock signal;

generating a multicast control symbol in dependence upon the reference clock signal;

coupling the multicast control symbol directly to the first plurality of transmit ports; and

transmitting the multicast control symbol to the second receive port.

18 . A method as claimed in claim 17 including the step of synchronizing the multicast control symbol to the reference clock signal.

19 . A method as claimed in claim 17 wherein the step of transmitting the multicast control symbol uses the reference clock signal.

20 . A method as claimed in claim 17 including the step of receiving the multicast control symbol at the second receive port.

21 . A method as claimed in claim 17 where the transmission of the multicast control symbol is delayed to ensure that no RapidIO protocol artifacts induce jitter in the propagation of the multicast control symbol

22 . A method as claimed in claim 20 including the step of directly coupling the multicast control symbol via the second input/output port to a multicast control symbol acceptor.

23 . A method as claimed in claim 22 including the step of receiving in software the multicast control symbol from the multicast control symbol acceptor.

24 . A method as claimed in claim 22 including the step of receiving in hardware the multicast control symbol from the multicast control symbol acceptor.