Subject: Re: SDL-News: Broadcast
Date: Thu Aug 06 1998 - 08:12:31 GMT
The originator of this message is responsible for its content.
-----From tariq#erg.abdn.ac.uk to sdlnews -----
I do applogise for qouting the wrong example regarding the Internet packet.
Sorry for the mis-information.
> From daemon Mon Aug 3 17:01:02 1998
> >From j.dalton#virgin.net Mon Aug 3 17:00:55 1998
> Date: Mon, 03 Aug 1998 16:44:44 +0100
> From: John Dalton <j.dalton#virgin.net>
> MIME-Version: 1.0
> To: tariq#erg.abdn.ac.uk, sdlnews#sdl-forum.org
> Subject: Re: SDL-news: Broadcast
> Content-Transfer-Encoding: 7bit
> tariq#erg.abdn.ac.uk wrote:
> > For example the protocols we are develpoing in Aberdeen require a message to be
> > transmitted to all the process and a process makes a decision either message is
> > addressed to it or not. I belive it is very similar to a packet which transmitted
> > over the internet and each reciver makes a decision wheather the packet is addressed
> > to it or not. If packet is addressed to it, the reciver accept a packet and if not
> > it ignores it.
> This is not how Internet works! If it did it would be a logjam. Routers decide which
> ports (channels) to send messages out of depending on their address headers. Only a few
> trial messages get multicast to find out which channel is fastest/closest, and then only
> along the list of available ports. Stuff on your local network is broadcast to all
> receivers on the network, but it doesn't all go out of the internet gateway!
> The LAN activity is really layer 1 stuff, a characteristic of the
> transmission medium implemented in hardware. It's normally really hard to describe
> physical layer stuff in SDL. Things like collision avoidance, time-delay propagation
> protocols and so on are impossible in SDL.
> I agree broadcast would be convenient at times, but to be practical it would also have
> to be limited as well. How else could you terminate the broadcast? The echos could go
> on forever......
> >From John Dalton of Reflex Technology, High Wycombe UK 01494-465907
> SDL tools, real-time OS tools and debugging hardware (01308-863795 direct)
-----End text from tariq#erg.abdn.ac.uk to sdlnews -----
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