Date: Thu, 16 Sep 1999 21:02:08 From: Ross Finlayson <finlayson@live.com> To: The Hermit Hacker <scrappy@hub.org> Cc: freebsd-multimedia@FreeBSD.ORG Subject: Re: Multicast: a blanket protocol? Message-ID: <3.0.5.16.19990916210208.21971158@shell7.ba.best.com> In-Reply-To: <Pine.BSF.4.10.9909170921510.27097-100000@thelab.hub.org>
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Answering your various questions about multicast & liveCaster > If I run liveCaster (multicast) on our network of ~4000 >computers...do all those 4000 computers see packets? This depends upon how sophisticated your network's switches/routers are, but in general, every machine on your network *that has subscribed to the multicast address* will see packets. (Caveats: (i) If you have level-3 routers in your network, then they may have to be especially configured to do multicast routing. (ii) If you have level-2 switches in your network that aren't particularly sophisticated, then they *may* end up delivering multicast packets to all network segments (even those without hosts who have subscribed to the multicast address).) >The question is how far does this "broadcast" go? For instance, my >co-worker and I are on the same subnet, with other ppl on other subnet's >be able to see the stream also, or is there somethign special I have to do >at the router, or? If, as is likely, you have level-3 (i.e., IP level) routers between these subnets, then you may have to configure them to handle multicast routing. (Check with your network administrator and/or router vendor.) >Am I correct in assuming that since its multicast, getting stats on number >of listeners is impossible? *raised eyebrow* Getting *exact* statistics is, in general, impossible. However, if the multicast receiving tool implements RTCP, then it will periodically send back (via multicast) a 'status' message. The sending tool (liveCaster) will then receive these and use this to count the known audience size. (This count is shown in liveCaster's main window.) Note, however, that "Freeamp" - even though it can receive MP3/RTP multicast, currently does not implement RTCP, so if some of your listeners use Freeamp to receive your broadcast, you won't be able to count them. On the other hand, the "playRTPMPEG" tool (which works by feeding a separate, existing MP3 player tool) *does* implement RTCP, so you will be able to count (estimate) them. (Note: I will shortly be releasing a MP3/RTP input 'plugin' for the popular "Winamp" Windows MP3 audio player. This will also use RTCP.) Ross. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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