The 802.11 MAC requires that all broadcast and multicast packets be sent at rates only in the Basic Service Set, which is generally the 1 or 2Mbps rate, even under 802.11g. Also, these packets do not receive the reliable (ACKed) transmission sevice, so drops go undetected and uncorrected at the link layer. This behavior is at the root of a lot of wireless network behavior oddities. It is sometimes possible to extend the BSS with good driver software, but I have never seen consumer-grade equipment offering this feature. One would certainly not attempt to suggest it to the public at large as a solution.
The true benefit of multicast for synchronization is that if the server sends a single multicast sync packet, all squeezeboxes should receive it simultaneously (aside from propagation variations, about 1ns per foot difference in distance from the host access point, which is negligible for our purposes) This approach eliminates the delay difference in the multiple unicast approach, even if the 802.11 MAC transmits the sync packet at a low rate in an unreliable fashion. If you send one sync packet per second, even if one gets lost there is another one coming real soon. Don't try to sync all squeezeboxes to a single squeezebox on the network, sync them all to the server. Buffering and streaming do not need to be changed; just signpost to a single common clock and all should be well. -- mikew ------------------------------------------------------------------------ mikew's Profile: http://forums.slimdevices.com/member.php?userid=3250 View this thread: http://forums.slimdevices.com/showthread.php?t=19466 _______________________________________________ Discuss mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/discuss
