Amine El hedadi wrote:
Linux use timer in muticast to excute periodically a function to keep session between switch & computer whitch need multicast flux , so it use one timer by multicast connection(IGMP protocol). this work not need a real time behaviurs, so why I have asked about using the same timer in RTNET framework. I can use real periodic task but I don't need real time behaviors in this case, may be rt task with low priority.
I see, my knowledge about multicast has just been proven to be rather limited :).
The point with a Linux timer is not that it is too unreliable for this task (BTW, about what period dimensions are we talking here?), the problem is that you cannot issue a packet from non-RT Linux context (IRQ, tasklet, process, whatever). So you need at least a low prio real-time task (one step above Linux, see how RTcfg works WRT timers e.g.) to transmit this keep-alive stuff.
I guess you have to transmit those packets only if no other traffic was present on the specific multicast channel (MAC address), haven't you? Isn't it possible to code this feature into the application? I think it knows best when it last received or transmitted some data. Or am I just missing some important characteristics of the IGMP protocol?
In any case, I think the IGMP part, which seems to be required when it comes to IP multicasting, is part of step 2, while the first step should be to get the low level multicast support (Ethernet layer) working. Or does this appear to be too tightly coupled for you?
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